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Spatial transcriptomics profiling of gallbladder adenocarcinoma: a detailed two-case study of progression from precursor lesions to cancer
BMC Cancer volume 24, Article number: 1025 (2024)
Abstract
Background
Most studies on tumour progression from precursor lesion toward gallbladder adenocarcinoma investigate lesions sampled from distinct patients, providing an overarching view of pathogenic cascades. Whether this reflects the tumourigenic process in individual patients remains insufficiently explored. Genomic and epigenomic studies suggest that a subset of gallbladder cancers originate from biliary intraepithelial neoplasia (BilIN) precursor lesions, whereas others form independently from BilINs. Spatial transcriptomic data supporting these conclusions are missing. Moreover, multiple areas with precursor or adenocarcinoma lesions can be detected within the same pathological sample. Yet, knowledge about intra-patient variability of such lesions is lacking.
Methods
To characterise the spatial transcriptomics of gallbladder cancer tumourigenesis in individual patients, we selected two patients with distinct cancer aetiology and whose samples simultaneously displayed multiple areas of normal epithelium, BilINs and adenocarcinoma. Using GeoMx digital spatial profiling, we characterised the whole transcriptome of a high number of regions of interest (ROIs) per sample in the two patients (24 and 32 ROIs respectively), with each ROI covering approximately 200 cells of normal epithelium, low-grade BilIN, high-grade BilIN or adenocarcinoma. Human gallbladder organoids and cell line-derived tumours were used to investigate the tumour-promoting role of genes.
Results
Spatial transcriptomics revealed that each type of lesion displayed limited intra-patient transcriptomic variability. Our data further suggest that adenocarcinoma derived from high-grade BilIN in one patient and from low-grade BilIN in the other patient, with co-existing high-grade BilIN evolving via a distinct process in the latter case. The two patients displayed distinct sequences of signalling pathway activation during tumour progression, but Semaphorin 4 A (SEMA4A) expression was repressed in both patients. Using human gallbladder-derived organoids and cell line-derived tumours, we provide evidence that repression of SEMA4A promotes pseudostratification of the epithelium and enhances cell migration and survival.
Conclusion
Gallbladder adenocarcinoma can develop according to patient-specific processes, and limited intra-patient variability of precursor and cancer lesions was noticed. Our data suggest that repression of SEMA4A can promote tumour progression. They also highlight the need to gain gene expression data in addition to histological information to avoid understimating the risk of low-grade preneoplastic lesions.
Background
Gallbladder cancer accounts for less than 2% of cancer-related deaths and is often fortuitously diagnosed in gallbladder samples following cholecystectomy. The prognosis of the disease remains poor because patients often present at an advanced stage with unresectable tumour. Late diagnosis results from the lack of specific symptoms and of screening strategies, as well as from limited knowledge of the mechanisms driving tumour progression [1, 2]. Several studies investigated the pathology, genomics and epigenomics of tumour progression from precursor to cancer stage. They mostly investigated precursor and cancer lesions from distinct patients, precluding a good understanding of tumour progression at the individual level. Spatial transcriptomic data on precursor and adenocarcinoma lesions coexisting in a same patient are expected to provide clues on the mechanisms of tumour progression.
Adenocarcinomas account for > 90% of gallbladder cancers and are considered to develop according to a metaplasia-dysplasia-adenocarcinoma histogenic sequence, in which the dysplastic stage consists of low-grade and high-grade biliary intraepithelial neoplasia (BilIN) [3,4,5,6,7,8]. BilINs consist of microscopic, flat or micropapillary lesions whose grade depends on the highest degree of cytological and architectural atypia. Low-grade BilINs display moderate cytoarchitectural atypia with pseudostratification of the nuclei, increased nucleo-cytoplasmic ratio and hyperchromasia. High-grade BilINs, formerly called carcinomas in situ, are defined by loss of nuclear polarity, marked cytological atypia and complex architectural patterns such as micropapillae [9,10,11].
Genomic alterations are already found at the BilIN stage. KRAS and TP53 mutations were found in BilINs [12, 13] and a progressive increase in TP53 overexpression was proposed to occur during the evolution from low-grade BilIN to GBC [14]. A recent exome sequencing study uncovered CTNNB1, TP53, ARID2 and ERBB3 as the most frequently mutated genes in low-grade and high-grade BilINs [15]. When the disease evolves to invasive adenocarcinoma, alterations accumulate, and tumours display significant cell type heterogeneity [16, 17]. At that stage the most frequent mutations affect KRAS, CTNNB1, TP53, PI3KCA, ERBB2, CDKN2A and CDKN2B [18,19,20,21,22,23,24,25,26], indicating that a fraction of the mutations found at the cancer stage can be detected in BilIN lesions. At the epigenome level, cancer lesions were split in subtypes with distinct hypermethylation: hypomethylation ratios; progressive and cumulative changes in promoter methylation were detected during progression from cholecystitis to cancer [26,27,28,29]. Increased hypermethylation was observed in adenocarcinomas as compared to BilINs. These epigenomic changes impacted Wnt/β-catenin signalling, Hedgehog signalling, tumour suppression and cell-microenvironment interactions [30,31,32]. Further, since gallstone-induced chronic inflammation drives gallbladder carcinogenesis [33], several authors compared the transcriptome of normal gallbladder tissue, gallbladder cancer, and gallbladder tissue exposed for varying lengths of time to gallstones, and identified molecular signatures associated with disease progression [34, 35]. Finally, in line with the genomic and epigenomic studies, single gene analyses revealed aberrant expression levels of TP53, P21, cyclin D1, EZH2, SMAD4 and CDKN2A protein at the BilIN stage [11], as well as the ability of a combined activation of KRAS and canonical Wnt/β-catenin or Notch signalling to induce gallbladder BilINs with malignant potential [36, 37]. Spatial transcriptomic data investigating BilIN to adenocarcinoma progression are still lacking.
Considering the genomics of tumour progression, Lin and coworkers provided evidence for patient-specific tumourigenic processes [15]. Their results indicated that precursor and cancer lesions within the same patient bear similar mutations, whereas the mutational signatures significantly vary between patients. Phylogenetic analysis of single nucleotide variants in lesions generated revealed that gallbladder cancer developed either BilIN-dependently or BilIN-independently [15].
To address the spatial transcriptomics of gallbladder tumour progression in individual patients, we selected samples from two patients displaying simultaneously several areas of gallbladder BilINs and adenocarcinoma, and collected an extensive spatial transcriptomic data set of each type of lesion per patient. The two patients were selected because of their differing cancer aetiology, offering the possibility to address intra-patient variability and tumour progression in distinct contexts. Our results show that each type of lesion displayed limited variability within the same patient, but significantly differed among patients. This revealed that the two patients have distinct tumourigenic processes, thereby corroborating earlier conclusions at the transcriptomic level. Our molecular investigations using gallbladder organoids also provide evidence that Semaphorin 4 A (SEMA4A) repression, which was observed in the two patients, can contribute to tumour progression.
Methods
Spatial transcriptomics
Spatial profiling was performed on formalin-fixed paraffin-embedded (FFPE) tissue sections using GeoMx (NanoString Technologies, Seattle, WA, USA) [38] which was implemented by NanoString. The GeoMx Whole Transcriptome Atlas assay probe cocktail containing 18,677 probes was tested. Regions of interest (ROIs) subjected to spatial transcriptomic profiling encompassed epithelial areas of approximately 200 cells. The 24 ROIs of Patient #1 were all located on the same tissue section. For Patient #2, the ROIs were partitioned over two sections, namely 8 ROIs covering normal epithelium on one section, and 24 ROIs covering lesional tissue on a second section (Table 1). Additional information is provided in Additional file 1 (Supplementary methods).
Histology and staining
Hematoxylin/Eosin (H&E) and Sirius red/fast green stainings were performed on 6 μm sections of FFPE tissues, tumours or organoids. Briefly, tissue sections were deparaffinised 3 × 3 min in xylene, 3 min in 99%, 95%, 70% and 30% ethanol and deionised H2O. Sections were stained 7 s in 100% hematoxylin, rinsed with H2O, stained for 7 s in 100% eosine, and rinsed with deionised H2O. Dehydration of sections was performed in deionised H2O, followed by 30%, 70%, 95%, 99% ethanol for 30 s, and 30 s in xylene. For collagen staining, slides were incubated into a picric acid solution with Sirius Red (Direct Red 80, Sigma-Aldrich) and Fast Green (SigmaAldrich) following manufacturer’s instructions. Coverslips were placed on slides using Depex mounting medium (VWR, Leuven, Belgium). Pictures were taken with panoramic P250 Digital Slide Scanner (Histogenex, Antwerpen, Belgium) using 3DHISTECH Case Viewer software.
Immunofluorescence and immunohistochemistry
Immunofluorescence and immunohistochemistry were performed on 6 μm sections of FFPE tissues. FFPE tissue sections were deparaffinised 3 × 3 min in xylene, 2 min in 99%, 95%, 70% and 30% ethanol and deionised water. Antigen retrieval was performed by the use of Lab Vision PT Module (Thermo Fisher Scientific, Waltham, MA), in 10 mM citrate pH 6. Sections were permeabilised for 10 min in 0.3% Triton X-100 in PBS before blocking for 1 h in 5% HS,10% BSA, 0.3% Triton X-100 in PBS. Primary antibodies were diluted in blocking solution at 4 °C overnight and secondary antibodies were diluted in 10% BSA, 0.3% Triton X-100 in PBS at 37 °C for 1 h. Images were taken with panoramic P250 Digital Slide Scanner (Histogenex, Antwerpen, Belgium) using 3DHISTECH Case Viewer software. Primary and secondary antibodies are described in Additional file 1 (Supplementary Table S1).
RNAscope in situ hybridisation
RNAScope RNA in situ hybridisation was performed on 5 μm sections of FFPE tissues, according to the manufacturer’s protocol for manual RNAscope®2.5 HD Assay—RED (#322360, Advanced Cell Diagnostics/Bio-Techne, Abingdon, United Kingdom). The tissue sections were incubated at 60 °C for 1h30, deparaffinised 2 × 5 min in xylene and dehydrated 2 × 2 min in 99% ethanol. Endogenous peroxidase was blocked with hydrogen peroxide for 10 min at room temperature followed by two short washings with deionised water. Slides were heated for 10 s at 100 °C in deionised water, and antigen retrieval was performed for 15 min at 100 °C using RNAscope®Target retrieval. Tissue sections were washed in deionised water and 99% ethanol. Slides were dried for 5 min at room temperature and tissues were delineated using an ImmEdge Hydrophobic Barrier Pen (#310018, Advanced Cell Diagnostics/Bio-Techne, Abingdon, United Kingdom). Slides were incubated for 15 min with RNAscope®Protease plus (diluted at 1/5 in deionised water) at 40 °C, washed with deionised water and incubated with the Hs-COL1A1-Homo sapiens collagen type I alpha 1 mRNA probe for 2 h at 40 °C. The tissue sections were washed with RNAscope®Wash buffer and six amplifications were performed (using six reagents AMP1-AMP6). The signal detection followed using RNAscope®Fast A and B reagents for 10 min at RT. The slides were kept in phosphate-buffered saline (PBS) overnight and immunostaining was performed: sections were blocked for 45 min at room temperature in 3% milk, 10% bovine serum albumin (BSA), 0.3% Triton in PBS. Primary and secondary antibodies were diluted in 10% BSA, 0.3% Triton in PBS. Primary antibodies were incubated overnight at 4 °C and secondary antibodies were incubated 1h30 at 37 °C. Pictures were taken with Cell Observer Spinning Disk (Carl Zeiss, Zaventem, Belgium) and analysed with Zen blue software. Primary and secondary antibodies are described in Additional file 1 (Supplementary Table S1).
Gallbladder organoid culture
Human non-tumoral gallbladder tissues were obtained from patients who underwent cholecystectomy at the Cliniques Universitaires Saint-Luc, Brussels, using the method of Rimland and coworkers [39]. The karyotype of the selected organoid line was normal and whole exome sequencing detected an ERBB3R675G missense mutation at an allelic fraction of 0.021. The COSMIC database of somatic mutations in cancer does not report this variant which we considered as non-contributory to our experiments. To analyse the impact of blocking SEMA4A in gallbladder organoids, the latter were split and plated. After 24 h, SEMA4A antibody (IgG-SEMA4A, #14-1002-82 eBioscience/Thermo Fisher scientific, Brussels, Belgium) was added into the medium (10 µg/ml) and organoids were grown for 3 days. Additional information is provided in Additional file 1 (Supplementary Methods).
Cell culture
Human EGI-1 cholangiocarcinoma cells (German Collection of Microorganisms and Cell Cultures, kind gift from L. Fouassier) were grown in Dulbecco’s Modified Eagle Medium High Glucose with L-Glutamine (DMEM; Lonza/Westburg Leusden, The Netherlands), 10% foetal bovine serum (#F7524, SigmaAldrich) and 1% Penicillin-Streptomycin (Gibco). Cell cultures were incubated at 37ºC in a humidified atmosphere with 5% CO2.
Clonogenic assay
Colony forming capacity was determined by seeding 200 cells per well of a 6-well plate. Colony formation was allowed to occur over 10 days under 50 ng/ml treatment of recombinant human protein SEM4A4A (rhSEMA4a; Abcam #ab182683, Amsterdam, The Netherlands) or 10 µg/ml of IgG-SEMA4A previously desalted using a Zeba Spin Desalting Column, with the medium replenished every 3 days. Once colonies had formed, plates were washed in PBS and colonies fixed with methanol and stained 0.5% crystal violet solution (Sigma-Aldrich) for 15 min at room temperature. Following this step, crystal violet was discarded, and plates were washed with water. After drying, plates were scanned, and the number of colonies was analyzed using ImageJ software 1.50 (National Institutes of Health, Bethesda, USA).
Transwell assay
Cell migration was evaluated by using 8.0 μm pore size transwell inserts (Corning) in 24-well plate wells. Prior to migration assessment, cells were pre-treated for 48 h with 50 ng/ml rhSEMA4a or 10 µg/ml of IgG-SEMA4A. Next, cells were seeded into the upper chamber transwell insert (6 × 104 cells) in 200 µl serum-free medium while 750 µl medium with 10% foetal bovine serum was added to the lower chambers. In the case of cells treated with rhSEM4A or IgG-SEMA4A, both chambers contained rhSEM4A (50 ng/ml) or IgG-SEMA4A (10 µg/ml), respectively. After 24 h, cells were fixed with methanol and stained with 0.5% crystal violet. Non-migrated cells in the upper chamber were removed using a cotton swab. The area covered by migrated cells was analysed using ImageJ software 1.50 (NIH).
In vivo assessment of semaphorin 4 A function
The impact of IgG-SEMA4A and rhSEMA4A on tumour growth was evaluated in NOD scid gamma (NSG) mice carrying EGI-1 subcutaneous xenografts. 106 EGI-1 cells from independent cultures were injected subcutaneously at 4 distinct locations (under the right and left front leg, and under the right and left rear leg) in NSG mice. After 4 weeks, the animals received intraperitoneal injections of PBS, IgG-SEMA4A (5 mg/kg) previously desalted using a Zeba Spin Desalting Column (Thermo Fisher Scientific), or rhSEM4A (500 µg/kg) in a final volume of 200 µl every other day, receiving a total of 4 doses of treatment. Tumour volume (V) was measured every 48 h using a calliper and calculated by the formula [V = 0.5 × (L × W2)], where L and W represent the longest and the perpendicular tumour axis respectively. Relative tumour volume was defined by normalising to the initial tumour volume at the start of the treatment (V0).
Data on growth of PBS-treated tumours were obtained with 10 independent EGI-I cell cultures injected in 3 NSG mice (each receiving simultaneous cell injections at 3, 3 and 4 locations, respectively); out of these, 7 tumours were selected for histological analyses and microvascular invasion, and they originated from two mice. Data on growth of rhSEMA4A-treated tumours were obtained with 8 independent EGI-I cell cultures injected in 2 NSG mice (each receiving 4 simultaneous cell injections); out of these, 7 tumours were selected for histological analyses and microvascular invasion. Data on growth of anti-SEMA4A IgG-treated tumours were obtained with 8 independent EGI-I cell cultures injected in 2 NSG mice (each receiving 4 simultaneous cell injections); the 8 tumours were analysed for histology and microvascular invasion.
Bioinformatic analysis of spatial transcriptomic profiling data
Sequencing quality was assessed for each ROI. Raw number of reads ranged from 1,750,000 to 21,875,463. Alignments rates, sequencing saturation and RTSQ30 were respectively higher than 80%, 70%, and 98% in all ROIs. The percent of detected genes (i.e. genes with an expression value higher than the LOQ value, defined as the negative probes geometric means + 2 standard deviations) was evaluated per segment, to identify low-performing AOIs that should be removed. All ROIs were kept, as values ranged from 13.6 to 51.4%. Raw count normalisation and differential expression analyses were performed using DESeq2 Bioconductor package v1.32.0 [40]. The generalised linear model was fitted using the following design: type of lesion * patient. The lists of differentially expressed genes generated by DESeq2 were ranked on the t-statistic values, and KEGG and HALLMARK gene set enrichment analyses were performed using clusterProfiler v4.0.5 [41].
Results
Selection of normal epithelium, BilIN and adenocarcinoma in samples of human gallbladder
Our goal is to characterise the spatial transcriptome of gallbladder lesions during progression from normal epithelium to adenocarcinoma. This required gallbladder samples that simultaneously contain non-tumoral (i.e. histologically normal) epithelium, low-grade BilIN, high-grade BilIN and adenocarcinoma, from patients with distinct cancer aetiology. Each lesion must be large enough to enable us to analyse the whole transcriptome of several regions of each type of lesion. Samples that met these critera from two patients were identified in the biobank of the Cliniques Universitaires Saint-Luc: Patient #1 was an 81 year old woman who underwent cholecystectomy to treat cholecystitis; adenocarcinoma was an incidental finding. Patient #2 was a 53 year old man affected with primary sclerosing cholangitis (PSC) whose gallbladder was resected following imaging that revealed a thickening of the gallbladder wall. According to the TNM classification, both patients were staged IIa (pT2a T0 M0). Pathological diagnoses of non-tumoral epithelium, BilINs and adenocarcinoma were made on H&E-stained sections, and were confirmed by two expert pathologists. Patient #1 displayed two small foci of intestinal metaplasia, and no metaplasia was detected in Patient#2. GeoMx Digital Spatial Profiling (NanoString) [38] was implemented on sections adjacent to the H&E-stained sections to collect whole transcriptome data from 56 epithelial ROIs, each covering approximately 200 epithelial cells of non-tumoral epithelium, BilIN and adenocarcinoma (Table 1). Metaplasia in Patient #1 were too small for spatial profiling. Figure 1 illustrates the spatial distribution of areas in which ROIs were delineated (Fig. 1A), as well as examples of H&E-stained non-tumoral epithelium, BilINs and adenocarcinomas (Fig. 1B). All adenocarcinoma ROIs in the two patients were well-differentiated (histological grade 1) and compatible with the definition of pancreatico-biliary adenocarcinomas which are characterised by widely spaced tubular structures embedded in a fibrous stroma [42]. Epithelial ROIs were delineated on sections stained with antibodies which detect markers of the epithelium (panCytokeratin), leukocytes (CD45), and mesenchymal cells (α smooth muscle actin). Nuclei were immunolabeled with anti-Human antigen R antibodies (Additional file 2, Supplementary Fig. S1). The ROIs were subjected to transcriptomic analyses as described in Methods.
Spatial transcriptomic analysis suggests limited intra-patient variability and distinct modes of tumour progression among the two patients
Principal component analysis (PCA) of the 56 transcriptomes revealed a remarkable clustering of the non-tumoral epithelial samples of the two patients (Fig. 2A). ROIs from the same type of lesions clustered together within the same patient, but were separated between patients. In Patient #1, adenocarcinoma ROIs clustered close to high-grade BilIN ROIs, whereas adenocarcinomas in Patient #2 appeared closely related to low-grade BilINs. These results were corroborated by the number of differentially expressed genes (log2 fold change ≥ 1.0; padj ≤ 0.05) when cross-comparing all tissue types (Additional file 2, Supplementary Fig. S2A). Together, these data revealed that each lesional type displays limited intra-patient variability, but that distinct mechanisms are driving tumourigenesis in the two patients. Moreover, the PCA plot suggested that adenocarcinoma evolved according to a normal → low-grade BilIN → high-grade BilIN → adenocarcinoma sequence in Patient #1, and according to a normal → low-grade BilIN → adenocarcinoma sequence in Patient #2, with high-grade BilIN emerging separately from adenocarcinoma in this patient.
We next compared the lesions in the two patients and focused on signalling pathways. Using Gene Set Enrichment Analysis (GSEA) [43], we found several enriched signalling pathways when comparing adenocarcinoma and non-tumoral epithelium. Negative or positive enrichment scores reflect enrichment of downregulated or upregulated genes, respectively (Fig. 2B). The use of KEGG or HALLMARKS gene sets revealed several pathways that were enriched in both patients, and other pathways that were enriched in only one patient. Heatmaps illustrate genes from the HALLMARKS and KEGG pathway gene sets that are differentially expressed between adenocarcinoma and non-tumoral epithelium in the two patients (Fig. 2C; Additional file 2, Supplementary Fig. S2B).
Galbladder cancer is often associated with mutations in PI3KCA, CTNNB1, KRAS, TP53, and ERBB2 [18,19,20,21,22,23,24,25,26]. GSEA revealed that PI3K-AKT-mTOR signalling (HALLMARK) is enriched in adenocarcinoma of both patients (Fig. 2C), and out of the 38 leading edge genes in Patient #2, 23 overlapped with the leading edge genes in Patient#1. HALLMARK gene sets are based on coordinately expressed and biologically relevant genes, and identify pathway activation phenotypes [44]. Therefore, the positive enrichment of PI3K-AKT-mTOR signalling reflects activation of the pathway. Further, GSEA suggested enrichment of Wnt signalling in both patients, when considering the KEGG Wnt signalling gene set in Patient #1 and the HALLMARK Wnt-β-catenin gene set in Patient #2 (Fig. 2C). However, the two gene sets differ in their composition, leading to different conclusions in the two patients. In Patient #1, Wnt ligands (WNT7B, WNT8A, WNT10A, WNT11), receptors (FZD2, FZD5) and effector (TCF7L2) were upregulated in adenocarcinoma as compared to non-tumoral epithelium. Genes induced by Wnt signalling and reflecting activation of a negative feedback loop (AXIN2, GSK3B) further reveal dynamic activity of the Wnt pathway in this patient (Additional file 2, Supplementary Fig. S2C). In contrast, in Patient #2, only 13 genes from the HALLMARK Wnt-β-catenin gene set were significantly enriched. Among these, most genes are not typical for Wnt signalling and belong to pathways with which Wnt signalling crossreacts. CTNNB1 is upregulated in adenocarcinoma of Patient #2 (log2 fold change = 1.10; padj=8.65 × 10− 10), in parallel with upregulation of Wnt signalling inhibitors DKK4 (log2 fold change = 0.86; padj=84.76 × 10− 4) and CSNK1E (log2 fold change = 0.51; padj=1.66 × 10− 3). Therefore, the analysis of genes of the HALLMARK Wnt-β-catenin gene set does not strongly support that Wnt signalling is active in Patient #2. KRAS signalling differs between the two patients, as evidenced by enrichment of RAS signalling (KEGG) in Patient #1, but downregulation of several KRAS targets within the KRAS signalling up gene set (HALLMARK) in Patient #2 (Fig. 2C). Similar to KRAS signalling, the p53 pathway differed between patients. Finally, GSEA did not highlight ERBB signalling. However, we found significant overexpression of EGFR, ERBB2 and ERBB3 in Patient #2, but only overexpression of ERBB2 in Patient #1 (Fig. 3A).
Although both patients can display enrichment of the same pathway, we noticed that the sequence of enrichment during tumourigenesis may differ among the patients. Indeed, PI3K-AKT-mTOR signalling became enriched in precursor lesions of Patient #1, namely at the low-grade BilIN → high-grade BilIN transition, whereas it became enriched only at the adenocarcinoma stage in Patient #2 (Fig. 3B). Other pathways whose enrichment is shared between the patients may in contrast display a similar sequence of enrichment. Indeed, androgen response and estrogen signalling became enriched at the precursor-to-adenocarcinoma transition (Fig. 3B). Notch signalling was also enriched in adenocarcinoma of both patients, and the enrichment was only significant when comparing non-tumoral epithelium and adenocarcinoma, not when comparing the precursor to adenocarcinoma transitions. This likely reflected a progressive activation throughout the tumourigenic process, without significant jumps between lesional states. Moreover, comparing the expression of leading edge genes in the Notch pathway also revealed interesting differences such as the strong upregulation of NOTCH3 in Patient #1 (log2 fold change = 2.05; padj = 5.2 × 10− 11) and more modest upregulation of this gene in Patient #2 (log2 fold change = 0.77; padj = 1.5 × 10− 3) (Fig. 3C).
Finally, the proposed sequence of tumor progression in patient #2, namely normal → low-grade BilIN → adenocarcinoma, suggests that low-grade BilINs in this patient display upregulated pathways that may be indicative of aggressiveness. In that context, GSEA analyses comparing non-tumoral tissues and low-grade BilINs showed enrichment of the MYC oncogenic pathway in patient #2, unlike in patient #1 (Fig. 3D). We also noticed that low-grade BilINs of patient #2, unlike those of patient #1, displayed increased expression of Midkine as compared to non-tumoral tissue (log2 fold change = 2.89; padj: 7.684 × 10− 15). Midkine is known to promote immunosuppressive macrophage differentiation in gallbladder cancer [17]. Also, EGFR, ERBB2 and ERBB3 expression was upregulated in the low-grade BilINs of patient #2 (Fig. 3A).
Spatial transcriptomic analysis reveals induction of collagen gene expression in tumoral epithelia
Nepal and coworkers considered the hallmark “epithelial-mesenchymal transition (EMT)” as indicative of poor prognosis [26]. In Patient #1, the corresponding HALLMARK gene set has the highest enrichment score when comparing adenocarcinoma with non-tumoral epithelium (Fig. 2B-C). The sequence of EMT enrichment is shown in Fig. 4A. No similar enrichment was found in Patient #2. Importantly, transcription factors typical for EMT and CADHERINS showed no significant differential expression during tumour progression in either patient (Fig. 4B). In contrast, extracellular matrix-coding genes were significantly upregulated and contributed significantly to the enrichment of the EMT pathway in the GSEA analyses (Fig. 4C). To support the latter data at the histological level, we resorted to RNAscope in situ hybridisation. We detected rare mRNAs coding for COL1A1 in non-tumoral epithelia of the two patients. Strong induction of COL1A1 was detected in high-grade BilIN of Patient #1, but also in low-grade BilINs of Patient #2 (Fig. 4D).
SEMAPHORIN4A downregulation promotes tumour progression
Our GSEA data uncovered axon guidance signalling as a potential driver of tumour progression in Patient #1 (Fig. 2B). Axon guidance genes, including SEMAPHORIN/PLEXIN ligand-receptor pairs, were enriched in Patient #1 adenocarcinomas, but not in Patient #2 (Additional file 2, Supplementary Fig. S3A). SEMA4A was downregulated in the adenocarcinomas of both patients, and this was noticed already at the precursor stages (Fig. 5A). The involvement of SEMA4A in gallbladder cancer is unexplored, but SEMA4A loss-of-function mutation in familial colorectal cancer type X was found to promote cancer development, thereby revealing a tumour suppressor role for SEMA4A [45, 46]. Furthermore, we analysed a public RNAseq dataset from 10 patients for which paired non-tumoral tissue and adenocarcinoma had been collected [47]. The results showed that SEMA4A was significantly reduced in gallbladder tissue (Additional file 2, Supplementary Fig. S3B), in line with our findings in patients #1 and #2. This prompted us to investigate the role of SEMA4A in gallbladder cancer development.
We first generated organoids from gallbladder epithelium and selected a line which displayed no karyotypic anomalies. It expressed biliary-specific markers and exhibited biliary transport functions (Additional file 2, Supplementary Fig. S4). It also expressed the genes coding for SEMA4A and its receptor Plexin B1 (PLXNB1) (Additional file 2, Supplementary Fig. S3C). To mimick the downregulation of SEMA4A observed in our transcriptomic analyses, we incubated the organoids for 3 days with a blocking anti-SEMA4A IgG antibody. We found no change in cell proliferation, but observed local areas of pseudostratification of the epithelium in a subset of organoids (Fig. 5B). The histology of those areas was reminiscent of BilIN, indicating that inhibiting SEMA4A impacts cell polarisation.
We next determined if SEMA4A had additional tumour suppressor properties. Since the organoid lines were not able to induce tumour formation after subcutaneous injection in immunodeficient NSG mice, we used the human extrahepatic cholangiocarcinoma cell line EGI-1. In vitro, clonogenic and transwell migration assays demonstrated that adding rhSEMA4A to cultured EGI-1 cells reduced their clonogenicity and migration (Fig. 5C). Blocking anti-SEMA4A IgG antibody slightly but not significantly increased colony formation, and did not impact cell migration (Fig. 5C). In vivo, subcutaneous injection of EGI-1 cells in immunodeficient NSG mice resulted in the formation of tumours. We did not observe any significant histological differences between EGI-1 xenografts treated with intraperitoneal administration of rhSEMA4A, anti-SEMA4A IgG, or the control condition, except for microvascular invasions (Fig. 5D; Additional file 2, Supplementary Fig. S3D). Indeed, consistent with the decreased migration induced in vitro by rhSEMA4A, administration of rhSEMA4A resulted in a significant reduction of microvascular invasion in EGI-1 cell-derived tumours (Fig. 5D). Anti-SEMA4A IgG antibody had no effect on microvascular invasion in the tumours. Recombinant SEMA4A did not impact tumour growth. In contrast, blocking IgG anti-SEMA4A antibody accelerated growth at the earliest stages of tumour growth to progressively reach a plateau (Fig. 5E). We conclude that SEMA4A can control tumour progression by impacting polarity, clonogenicity and migration of cells.
Discussion
Earlier mutational profiling of precursor and cancer lesions coexisting in a same patient provided evidence that adenocarcinoma development may be BilIN-dependent or -independent [15]. Here, using GeoMx technology we extended these findings at the transcriptional level in two patients. We showed that lesions exhibited low intra-patient variability, but exhibited patient-specific sequences of signalling pathway activation.
In Patient #1, ROIs from a same type of lesion were often located at a short distance from each other, except for adenocarcinoma ROIs which were more scattered throughout the tissue sample. In Patient #2, high-grade BilIN ROIs were close to each other, but low-grade BilIN, adenocarcinoma and non-tumoral epithelium ROIs were significantly dispersed (Fig. 1A). Still, in spite of the scattering within the tissue, the transcriptomic profile of lesions belonging to the same histological type showed low intra-patient variabilty. Such transcriptomic homogeneity likely reflects that cells from a same type of lesion proliferated in a similar environment and with limited accumulation of new mutations. Clonal analysis of gallbladder cancers revealed subclonal diversification [48], in line with significant epithelial cell heterogeneity in the adenocarcinoma lesions notices in single cell RNA sequencing studies [16, 17]. However, our patient samples contained all lesional types on the same tissue sections, suggesting that cancer lesions had not enough time to accumulate genomic lesions, invade the tissue and produce subclones.
The neighbourhood of low-grade BilIN, high-grade BilIN and adenocarcinoma which may occur in pathological samples, leads us to surmise that the epithelium undergoes a normal epithelium → low-grade BilIN → high-grade BilIN → adenocarcinoma histogenic sequence. A contrario, the transcriptomic profile of Patient #2 strongly suggests that adenocarcinoma derived from low-grade BilIN, not from adjacent high-grade BilINs. This contrasted with Patient #1 whose adenocarcinoma ROIs were closely related to high-grade BilINs. We excluded that adenocarcinoma in Patient #2 corresponded to low-grade BilINs extending in Rockitansky-Aschoff sinuses. In Patient #2, only 58 genes were 2-fold up- or downregulated when comparing low-grade BilIN and adenocarcinoma, revealing that low-grade BilIN may be at high risk for evolution towards invasive cancer.
Many signalling pathways were activated during tumour progression and several were common between the two patients. However, the sequence of pathway activation differed between patients, some of the common pathways being activated at the BilIN stage in one patient, but only in the adenocarcinoma cells in the other patient. Therefore, our work suggests that various combinations of pathway activations may end up yielding cancer, no specific pathway or combination of pathways being responsible for transition from one stage to the other.
The HALLMARK gene set “Inflammatory response” was enriched in adenocarcinomas of both patients (not shown), reflecting their common chronic inflammatory background. Still, the tumour aetiology differed in Patients #1 and #2, with Patient #2 being affected with PSC, a disease with high incidence of adenocarcinoma [49]. The adenocarcinoma in Patient#2 was mucosecreting (Fig. 1B), unlike the carcinoma in Patient #1. The mutational profile of cholangiocarcinoma in PSC is heterogeneous and affects genes similar to those in non-PSC associated cholangiocarcinoma, the most frequently mutated being TP53, KRAS, PI3KCA and GNAS. In low-grade and high-grade dysplastic lesions, loss or amplifications of several genes, as well as mutations in ERBB2 and TP53, can already occur [50, 51]. Our work extend these data at the transcriptomic level and highlight that low-grade BilIN can be very closely related to adenocarcinoma.
EMT is a phenotypic continuum during which epithelial cells evolve to a mesenchymal state via transitional or hybrid states [52]. It involves disruption of polarity and intercellular adhesion, changes in the interaction between cells and extracellular matrix, and increased migration [53, 54]. Interestingly, both patients display increased expression of COL1A1 and COL1A2. This differs from pancreatic cancer in which COL1A2 is no longer expressed [55], leading to the production of collagen α1/α1/α1 trimers which promote tumor progression.
SEMA4A is a tumour suppressor in colorectal cancer [45, 46]. Here we found that it is downregulated in both patients during gallbladder tumour progression, starting at the BilIN stage. Downregulation of SEMA4A in gallbladder cancer was also found in other patients (Additional file 2, Supplementary Fig. S3B). Gallbladder organoids expressed SEMA4A and its receptor PLXNB1 and the levels of SEMA4A expression varied considerably (Additional file 2, Supplementary Fig. S3B), likely explaining the variable pseudostratification of the gallbladder organoids when treated with blocking IgG antibody (Fig. 5B). Also, the low levels of SEMA4A and PLXNB1 in cholangiocarcinoma EGI-1 cells, as compared to organoids derived from normal gallbladder epithelium, fit with the notion that SEMA4A is repressed in biliary cancer cells and with our observation that anti-SEMA4 blocking antibodies have limited or no effect on clonogenicity and migration of EGI-1 cells in vitro. In vivo, we detected a higher level of SEMA4A in EGI-1 cell-drived tumours than in in vitro cultured EGI-1 cells (Additional file 2, Supplementary Fig. S3C). We excluded that this results from SEMA4A production by tumour-invading mouse cells, as our PCR primers were designed to specifically detect human SEMA4A. Inhibiting this in vivo production of SEMA4A enabled us to monitor growth-promoting properties of anti-SEMA4 blocking antibodies. How these anti-SEMA4A antibodies promote EGI-1 cell-derived tumour growth remains unclear. Indeed, our data show that inhibiting SEMA4A accelerates tumour growth during 4 days. This effect slows down to reach a plateau (Fig. 5E), and at the plateau stage we noticed a slight but not significant increase in proliferation rate, as evidenced by immunostaining for phospho-Histone H3 (Additional file 2, Supplementary Fig. S3C). We hypothesise that anti-SEMA4A antibodies promoted proliferation mainly during the first 4 days of treatment. Interestingly, rhSEMA4 did not impact tumour growth, but decreased microvascular invasion, suggesting that reduction of SEMA4 promotes metastasis. The signalling pathways mediating the effects of SEMA4A on migration, polarity and potentially proliferation deserve further investigation. Further studies will determine how frequently SEMA4A is repressed at early stages of gallbladder cancer and whether understanding its pathway may lead to identify biomarkers of early diagnosis of gallbladder tumours.
Conclusion
Our spatial transcriptomic analysis reveals that precursor and cancer lesions can display limited intra-patient variability during gallbladder cancer progression and supports that tumourigenic mechanisms are patient-specific. Repression of SEMA4A may contribute to tumour progression. Our work also underscores that low-grade BilINs may be at high risk for developing to cancer and should ideally be characterised by gene expression profiling.
Data availability
The dataset supporting the conclusions of this article is available in Gene Expression Omnibus (GSE259311).
Abbreviations
- BilIN:
-
Biliary intraepithelial neoplasia
- EMT:
-
Epithelial-mesenchymal transition
- FFPE:
-
Formalin-fixed paraffin-embedded
- H&E:
-
Haematoxylin and eosin
- PSC:
-
Primary sclerosing cholangitis
- ROI:
-
Region of interest
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Acknowledgements
The authors thank Cédric Van Marcke de Lummen (Université Catholique de Louvain, Brussels, Belgium) for advice; Atsushi Kumanogoh (Osaka University, Osaka, Japan), Thomas Worzfeld (University of Marburg, Marburg, Germany) and Svetlana Chapoval, University of Maryland, Baltimore, MA, USA) for information on SEMA4A biology; the Lemaigre lab members for help and support.
Funding
The work of F.P.L. was supported by the Belgian Foundation against Cancer (grant #2018-078), and the Fonds Joseph Maisin (grants 2020–2021 and 2022–2023). F.P.L. and L.G. were supported by the Fonds de la Recherche Scientifique (F.R.S.-F.N.R.S. Belgium, grant Télévie #7.8505.21). S.P., F.M.-N. and A.L. were supported by fellowships from the Fonds de la Recherche Scientifique (grants Télévie #7.4544.18 and Télévie #7.6510.20 to S.P.; Télévie #7.8505.21 to F.M.-N. and A.L.).
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S.P., F.M.-N., A.L., M.K., L.G. and F.L. designed the study; S.P., F.M.-N., A.L., S.C., S.A., C.H., S.T., acquired data; S.P., F.M.-N., A.L., L.D., N.L., C.S., M.K., L.G. and F.L. analysed and interpreted data. S.P., F.M.-N., A.L., L.D., N.L., L.G. performed statistical analyses. S.P., F.M.-N. and F.L. drafted the manuscript. All authors read and approved the final paper.
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The study on human samples was conducted in compliance with the ethical guidelines of the 2013 Declaration of Helsinki and was approved by the Comité d’Ethique Hospitalo-Facultaire (UCLouvain and Cliniques Universitaires Saint-Luc) with numbers 2018/06Jul/281 and 2021/26OCT/444. In accordance with article 8 of the internal rules of the Cliniques universitaires Saint-Luc, the need for informed consent was waived to the present retrospective study. The study is based solely on the analysis of residual human body material and on the collection of data existing in the medical files of patients who have not expressed their opposition to the use of their medical file for scientific research purposes. An informed consent exemption request was thus presented to the Ethics Committee, which was accepted. Mice received humane care and the research protocol was approved by the Animal Welfare Committee of the Université Catholique de Louvain with number 2022/UCL/MD/17.
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Pirenne, S., Manzano-Núñez, F., Loriot, A. et al. Spatial transcriptomics profiling of gallbladder adenocarcinoma: a detailed two-case study of progression from precursor lesions to cancer. BMC Cancer 24, 1025 (2024). https://doi.org/10.1186/s12885-024-12770-0
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DOI: https://doi.org/10.1186/s12885-024-12770-0