Myofibroblastic stromal reaction and lymph node status in invasive breast carcinoma: possible role of the TGF-β1/TGF-βR1 pathway
© Catteau et al.; licensee BioMed Central Ltd. 2014
Received: 3 February 2014
Accepted: 30 June 2014
Published: 9 July 2014
The microenvironment modulates tissue specificity in the normal breast and in breast cancer. The stromal loss of CD34 expression and acquisition of SMA myofibroblastic features may constitute a prerequisite for tumor invasiveness in breast carcinoma. The aim of the present study is to examine the stromal expression of CD34 and SMA in cases of invasive ductal carcinoma and to try to demonstrate the role played by the TGF-ß 1 et TGF-ß R1 pathway in the transformation of normal breast fibrocytes into myofibroblasts.
We carried out an immunohistochemical study of CD34, SMA, TGF-ß and TGF-ß R1 on a series of 155 patients with invasive ductal carcinoma. We also treated a breast fibrocytes cell line with TGF-ß1.
We found a loss of stromal expression of CD34 with the appearance of a myofibroblastic reaction in almost 100% cases of invasive ductal carcinoma. The strong stromal expression of SMA correlates with the presence of lymph node metastases. We were also able to show a greater expression of TGF-ß in the tumor cells as well as a higher expression of TGF- ß R1 in the tumor stroma compared to normal breast tissue. Finally, we demonstrated the transformation of breast fibrocytes into SMA positive myofibroblasts after being treated with TGF-ß1.
Our study demonstrated that a significant tumor myofibroblastic reaction is correlated with the presence of lymph node metastasis and that this myofibroblastic reaction can be induced by TGF-ß1. Future research on fibrocytes, myofibroblasts, TGF-ß and stromal changes mechanisms is essential in the future and may potentially lead to new treatment approaches.
KeywordsBreast carcinoma Tumor microenvironment Fibrocytes Myofibroblasts SMA CD34 TGF-ß Metastasis Lymph node
Breast cancer is the most common cancer among women in the world . The microenvironment modulates normal breast tissue, as well as the growth, survival, polarity, and invasive behavior of breast cancer cells [2, 3]. The stromal loss of CD34 expression and acquisition of smooth muscle actin (SMA) myofibroblastic features may constitute a prerequisite for tumor invasiveness in breast carcinoma [4, 5]. The origin of myofibroblasts is not yet clear and multiple hypotheses have been proposed. Myofibroblasts modulate the stroma in physiology and pathology through direct cell-to-cell contact and through secretion of different proteinases, extracellular matrix (ECM) components, growth factors and cytokines. Transforming Growth-Beta (TGF-ß) are multifunctional cytokines which inhibit epithelial cell growth, stimulate mesenchymal cell proliferation, regulate ECM, modulate immune function and wound repair. A desmoplastic reaction is frequent in many solid tumors, such as breast tumors, in which high levels of TGF-ß are found [6–9]. Casey et al. demonstrated that TGF-ß1 treatment in vitro activates normal primary breast fibroblasts and carcinoma-associated fibroblasts (CAFs) into myofibroblasts [10, 11], and subcutaneous injections of TGF-ß1 into mice stimulates the formation of reactive stroma . We hypothesize that TGF-ß facilitates breast cancer invasion by stimulating the appearance of myofibroblasts and creates an environment that promotes invasion and facilitates metastasis. The present study aims to investigate this phenomenon in cases of invasive ductal carcinoma (IDC) and to try to understand the underlying mechanism responsible for this myofibroblastic reaction, especially the role played by TGF-ß.
Breast tissue from cancer patients and normal controls (reduction mammoplasty) was collected from consecutive patients who were identified through the Pathology and Genetics Institute (IPG), resulting in 165 consecutive patients diagnosed between January 2010 and December 2012. This retrospective study was performed on 155 cases of invasive breast carcinoma and 10 cases of reduction mammoplasty from normal breast tissue to compare the expression of the antibodies between the tumor and normal breast tissue. All patients were female. 83 resection specimens and 82 biopsies were obtained. The study protocol was approved by the institutional ethics and research review boards at Erasme Hospital. People sign a written informed consent on admission to the hospital. Consent requires that physicians have the right to use the surplus biological material. The material that has not been used for diagnosis can be used for research (opting out system). Consent has been established by the local ethics committee and is in accordance with Belgian and International law (Helsinki declaration). The final pathological tumor stage was determined using the TNM staging system (AJCC Cancer Staging Manual, 7th edition, 2007) and graded using the Nottingham system . In addition, the patient’s age, tumor size, tumor shape, estrogen receptor (ER), progesterone receptor (PR), HER2/Neu status and KI-67 index were assessed in per cases. Among them, radiologists reviewed the radiological images of tumors and classified them as nodular, spiculate or mixed lesions.
Cell line cultures
Human mammary fibrocytes P10893 was purchased from Innoprot® and maintained in Innoprot-recommended media and conditions. The media were changed every two days. When cells reached confluence they were passaged to a 25 cm2 flask (Corning® Plasticware Cell Culture, Corning, NY, USA) by treating with 0.25% trypsin-25 mM EDTA (Gibco® Invitrogen Corporation) and agitating until cells began to detach from the surface of the flask (passage 1; p1). P2 cells were moved to a 75 cm2 flask and then passaged 1:4. All experiments were performed on fibrocytes that had been cultured for 3–10 passages.
Cells were phenotypically characterized by immunostaining. Cells positive for vimentin and negative for cytokeratin staining were considered fibroblasts. Cells were plated in six well chamber slides (Corning®), and grown to confluence. Cells were washed with PBS and fixed with 4% buffered formalin and immunostained according to the manufacturer’s protocols.
Assessment of fibrocytes activation into myofibroblasts
Cells were plated and grown to confluence in six-chamber slides in basal medium. Media was aspirated from the cultures and cells were washed twice with PBS and then incubated for 24 h in serum-free media with 0 or 2.5 ng/ml TGF-ß1 (Peprotech®) for 48 h with a change in the culture medium after 24 h. After 48 h, cells were fixed, and incubated with SMA and CD34 antibodies. The percentage of myofibroblasts was assessed by counting at least 1,000 total cells and determining the proportion stained positively for SMA in three fields at 200X in duplicate preparations.
Antibodies used in this study
Semi-quantitative assessment of immunohistochemistry
We analyzed the stromal distribution of CD34 and SMA in the tumor. Immunohistochemical expression of TGF-ß and transforming growth-Beta receptor-1 (TGF-ßR1) was evaluated in normal breast tissue (glands and stroma) and in tumor tissue (tumor cell and stroma). The immunoreactivity of CD34, SMA, TGF-ß and TFG-ßR1 was assessed semi-quantitatively. The percentage of stromal cells expressing CD34 and SMA was graded as “0”, “+”, “++”, “+++”, “++++” when up to 5%, more than 5% and up to 25%, more than 25% and up to 50%, more than 50% and up to 75% or more than 75% of stromal cells, disclosed immunoreactivity, respectively. Percentages were assessed by two independent observers, assuming that a high-power microscopic field (objective x40, microscopic magnification: x400) harbored 100 stromal cells (range: 75–150). We also evaluated the presence or absence of expression of TGF-ß and TGF-ßR1 in glands and stroma of normal and tumor tissue. Staining intensity for the TGF-ß and TGF-ßR1 antibodies was assessed in a semiquantitative manner by XC and JCN using the H scoring system as described by McCarty et al. . Briefly, scores are generated by adding together 3 ×% strongly staining, 2 ×% moderately staining, and 1 ×% weakly staining, giving a possible range of 0 to 300. An H-score >50 was considered as positive. An assessment of total percentage of cells showing positive staining was also carried out. When disagreements occurred between the two observers they were resolved using a double-headed microscope.
The relationship between the staining patterns of SMA and different clinical and histological features - age, tumor size, tumor shape, grade of invasive carcinoma, lymph node status, luminal classification, and KI-67 index - was compared using a Chi-squared test. A Student’s t-test was used to compare H-score and percentage positivity. A p-value <0.05 was considered statistically significant. All analyses were performed using Statistica®.
Clinicopathological features of invasive breast carcinoma patients
Clinicopathological data of 155 cases of invasive breast carcinoma
T1 (0.1- 2 cm)
T2 (>2- 5 cm)
T3 (>5 cm)
Stromal CD34 and SMA in vivo expression
Relation of stromal expression and clinicopathological features
Strong expression SMA*
Weak expression SMA**
p = 0.9
>40- ≤ 60
p = 0.98
p = 0.2
≤ 1 cm
p = 0.1
> 1 - ≤ 2 cm
> 2 cm
p = 0.9
Lymph node status
p < 0.05
TGF-ß and TGF-ßR1 in vivo expression
TGF-ß and TGF-ßR1 expression in tumor and normal tissue
Stromal TGF- ß
p > 0.05
Glandular TGF- ß
185 + − 81
125 + −41
p = 0.02
Stromal TGF- ß R1
197 + −104
80 + −27
p = 0.001
Glandular TGF- ß R1
129 + −102
110 + −22
p = 0.4
In vitro transformation of fibrocytes into myofibroblasts by TGF-ß1 in mammary cell line fibrocytes
Tumor cells secrete TGF-ß and normal fibrocytes have TGF-ß receptors. As demonstrated in vitro, tumor cells are therefore able to transform fibrocytes into SMA myofibroblasts.
Tumor cells may have an autocrine effect on their growth because they have TGF-ßR1 and express TFG-ß.
Since the stroma does not express TGF-ß, it therefore seems unlikely that the stroma may trigger the process of tumorigenesis via the TGF-ß pathway in any case.
We believe that several mechanisms may explain the promotion of tumor invasion in breast tissue induced by the loss of CD34 fibrocytes and the gain of SMA myofibroblasts.
CD34 fibrocytes are involved in the remodeling of stromal tissue damage not only through tissue contractility via TGF-ß, collagen I and III synthesis and SMA, but also in terms of migration factors within the injured tissue via CCR7, CXCR4, SLC, and CXCL12.
CD34 fibrocytes also play a role in angiogenesis via fibroblast growth factor, vascular endothelial growth factor, platelet-derived growth factor, interleukin-8, and matrix metalloproteinase-9.
The increase in myofibroblasts in breast cancer could result from transdifferentiation of resident interstitial cells expressing or not expressing CD34 fibrocytes into myofibroblasts.
Orimo et al.  demonstrated that carcinoma-associated fibroblasts (CAF), represented to a large degree by myofibroblasts, promote tumor growth and increase tumor angiogenesis by secretion of stromal derived factor (SDF)-1/CXCL12, which acts in a paracrine fashion to increase tumor cell proliferation via CXCR4. Hepatocyte growth factor (HGF) is another CAF-derived factor that has been implicated in promoting tumor progression and metastasis. The paracrine activation of c-Met on tumor cells by HGF increases invasion of experimental DCIS lesions in xenografts, for example . Interestingly, co-culture of normal mammary fibroblasts with breast cancer cells can ‘educate’ the fibroblasts to secrete HGF and increase their tumor-promoting activities .
The causal role of myofibroblasts in the transition from the non-invasive towards the invasive phenotype is suggested by the finding that the appearance of myofibroblasts precedes the invasive stage of cancer. This hypothesis seems to be confirmed in one of our previous studies in which we demonstrated the appearance of myofibroblasts around the lesions of DCIS. This expression was more intense around the high-grade lesions (pre-invasive lesions) .
Associated myofibroblasts prevent physical contact between cancer cells and immune cells, an essential phenomenon for cancer cell destruction. Histology of different types of tumors indicates that, in those tumors in which the myofibroblastic network is poorly developed, inflammatory cells infiltrate the tumors and are in close contact with the cancer cells. In contrast, the presence of myofibroblasts around progressive tumors is associated with the absence of immune and inflammatory cells within tumors .
In contrast to wound healing, myofibroblasts in the tumor microenvironment do not disappear by apoptosis, indicating that cancer is a wound that does not heal .
The stromal reaction induced by carcinomatous lesions leads to acquisition of SMA expression and in turn to stabilization of the lesion (wound contraction) that helps prevent the spread of tissue damage . This may reflect a defense mechanism against “stromal invasion” that induces a phenomenon of stromal healing and stabilization. However, the phenotypic transformation or suppression of (CD34) fibrocytes into SMA myofibroblasts could also cause the loss of most essential functions (including immunity, cell adhesion, motility, stromal remodeling, and angiogenesis inhibition), and in a paradoxical manner promote tumorigenesis, thus facilitating invasion and metastatic dissemination of tumor cells.
The present study demonstrated that a significant tumor myofibroblastic reaction is correlated with the presence of lymph node metastases and that this myofibroblastic reaction can be induced by TGF-ß1. Future larger studies on fibrocytes, myofibroblasts, TGF-ß and stromal change mechanisms are needed to confirm these results and may potentially lead to new treatment approaches.
Smooth muscle actin
Ductal carcinoma in situ
Invasive ductal carcinoma
Pathology and Genetics Institute
Transforming growth-beta receptor-1
Hepatocyte growth factor.
We thank Isabelle Fayt, Benedicte Culot, Cécile Dupond for their help with processing histological specimens and cell line cultures. This study was supported by IRSPG (Institut de Recherche Scientifique de Pathologie et de Génétique).
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