Breast cancer and human papillomavirus infection: No evidence of HPV etiology of breast cancer in Indian women
© Hedau et al; licensee BioMed Central Ltd. 2011
Received: 4 December 2009
Accepted: 20 January 2011
Published: 20 January 2011
Two clinically relevant high-risk HPV (HR-HPV) types 16 and 18 are etiologically associated with the development of cervical carcinoma and are also reported to be present in many other carcinomas in extra-genital organ sites. Presence of HPV has been reported in breast carcinoma which is the second most common cancer in India and is showing a fast rising trend in urban population. The two early genes E6 and E7 of HPV type 16 have been shown to immortalize breast epithelial cells in vitro, but the role of HPV infection in breast carcinogenesis is highly controversial. Present study has therefore been undertaken to analyze the prevalence of HPV infection in both breast cancer tissues and blood samples from a large number of Indian women with breast cancer from different geographic regions.
The presence of all mucosal HPVs and the most common high-risk HPV types 16 and 18 DNA was detected by two different PCR methods - (i) conventional PCR assays using consensus primers (MY09/11, or GP5+/GP6+) or HPV16 E6/E7 primers and (ii) highly sensitive Real-Time PCR. A total of 228 biopsies and corresponding 142 blood samples collected prospectively from 252 patients from four different regions of India with significant socio-cultural, ethnic and demographic variations were tested.
All biopsies and blood samples of breast cancer patients tested by PCR methods did not show positivity for HPV DNA sequences in conventional PCRs either by MY09/11 or by GP5+/GP6+/HPV16 E6/E7 primers. Further testing of these samples by real time PCR also failed to detect HPV DNA sequences.
Lack of detection of HPV DNA either in the tumor or in the blood DNA of breast cancer patients by both conventional and real time PCR does not support a role of genital HPV in the pathogenesis of breast cancer in Indian women.
Breast cancer is the second most common cancer in the world, after the cancer of the lung, affecting one in eight women during their lifetime, but it is the leading cancer among women worldwide . In India breast cancer is the second most dominant cancer in women, but it is showing a fast rising trend in major metropolitan cities in India . Although various clinico-epidemiologic, genetic and epigenetic factors including mutations in breast cancer susceptibility genes BRCA1 and BRCA2 [3, 4], sex-steroid hormones and lifestyle factors have been strongly implicated in the development of breast cancer, the mechanism(s) of breast carcinogenesis is still not clearly understood.
High-risk human papillomaviruses (HR-HPVs) are carcinogenic viruses which are primarily associated with cervical cancer but are also linked with other anogenital cancers and cancers of other organ sites  such as oral cavity [6–8], esophagus [9–11], nasopharyngeal and laryngeal carcinoma [5, 12–15] and possibly in retinoblastoma [16–18]. In India, HPV is found to be present in 100% of cervical cancer specimens and prevalence of high risk HPV type 16 is exceptionally high (~90%) in them . The HR-HPV oncoproteins E6 and E7 which have been found to interact and inactivate the two principal host cell tumor suppressor proteins p53 and Rb respectively [20–22] are also shown to immortalize human mammary epithelial cells in-vitro [23, 24]. Several other viruses have also been implicated in the etiology of human breast cancer [23, 24] but these are not confirmed by other authors [25, 26].
Reports on the distribution of HPV infection in breast cancer are not only limited but also highly controversial. Several authors [27–31] including our previous report on fine needle aspirated breast cancer cells  did not find any HPV infection in breast cancer. A moderate frequency of 20-48% HPV infection was reported by many authors [33–42], whereas a very high frequency of HPV infection ranging from 60 to 85% occurrence of HPV in breast cancer was reported by others [43–46]. Most interesting is recent demonstration of high risk HPV18 in the breast cancer cell lines by in-situ hybridization and observation of HPV-specific koilocytes in breast cancer cells which reiterates the oncogenic role of HPV in breast cancer . This prompted us to re-look into the role of HPV in a large number of breast cancer cases that were previously analyzed for mutations in BRCA1, BRCA2 and p53 tumor suppressor genes  and collected from all four different regions of India. We used both conventional and real time PCR assays with consensus (MY09/11, GP5+/GP6+) and type specific (HPV16 E6/E7) primers to detect HPV DNA sequences in tumors as well as corresponding blood samples of same breast cancer patients. The results demonstrate complete absence of HPV DNA in breast cancer patients in India.
Breast cancer patient population and sample collection
Distribution of breast biopsies and blood samples from the different regions of India
Name of the Hospitals
Lok Nayak Hospital, New Delhi
Sher-I-Kashmir Institute of Medical Sciences, Srinagar, Jammu & Kashmir
Regional Institute of Medical Science, Imphal Assam Medical College, Dibrugarh Silchar Medical College, Silchar
Goa Medical College, Goa
Kidwai Memorial Institute of Oncology, Bangalore
DNA extraction for PCR
Conventional PCR using L1 consensus MY09/11 and GP5+/GP6+ or HPV16 E6/E7 primers
Oligonucleotide primer sequences used for the amplification of different regions of HPV and internal control.
5'-GCM CAG GGW CAT AAY AAT GG-3'
5'-CGT CCM ARR GGA WAC TGA TC-3' where M = A + C, W = A + T, Y = C + T, R = A + G).
5'-TTT GTT ACT GTG GTA GAT ACT AC-3'
5'-CTT ATA CTA AAT GTC AAA TAA AAA-3'
HPV16 E6 (F)
5'-GAA ACC GGT TAG TAT AAA AGC AGA C-3'
HPV16 E6 (R)
5'-AGC TGG GTT TCT CTA CGT GTT CT-3'
HPV16 E7 (F)
5'-CAA TAA TAT AAG GGG TCG GTG GA-3'
HPV16 E7 (R)
5'-TTT TTC CAC TAC AGC CTC TAC AT-3'
5'-GAA GAG CCA AGG ACA GGT AC-3'
5'-CAA CTT CAT CCA CGT TAC ACC-3'
p53 Exon 5 (F)
5'-TAC TCC CCT GCC CTC AAC AA-3'
p53 Exon 5 (R)
5'-CAT CGC TAT CTG AGC AGC GC-3'
Briefly, the method involved a 25 μl reaction mix containing 100-200ηg DNA, 10 mM Tris-Cl (pH 8.4), 50 mM KCl, 1.5 mM MgCl2, 12.5 μM of each dNTP (dATP, dCTP, dGTP and dTTP), 5 pmoles of each oligonucleotide primer and 0.5 U Taq DNA polymerase (Perkin-Elmer Biosystems, Foster City, CA, USA). The temperature profile used for amplification constituted an initial denaturation at 95°C for 5 min followed by 30 cycles with denaturation at 95°C for 30 sec, annealing at 55°C for 30 sec and extension at 72°C for 30 sec which was extended for 7 min in the final cycle. The HPLC-purified oligonucleotide primers were custom synthesized commercially by M/s Microsynth GmbH (Balgach, Switzerland).
Highly sensitive qRT-PCR was performed for detection of low copy number HPV infection. qRT-PCR employed in the study had the capability of detecting as low as 5 copies of HPV genome per reaction which is equivalent to 0.005 HPV copies per cell equivalent using GP5+/GP6+ consensus primers with Biorad SYBR Green Supermix kit and iCycler PCR (Biorad, Hercules, CA). p53 exon 5 primer sequences (Table 2) were used to normalize the HPV DNA with respect to human genomic DNA. qRT-PCR was calibrated using 10 fold serial dilutions of HPV16 International Standards (IS; ranging from 104-101) supplied under WHO Global HPV LabNet program. Background genomic DNA from HPV-negative cell line C33a was used as negative control and for dilution of standards as prescribed by WHO. Briefly, the amplification was performed in 25 μl reaction mix containing 5 pmol each of GP5+ and GP6+ primers and 30-50ηg of genomic DNA in 5 ul of test volume. The amplification ramp included first step for 3 min at 95°C for initial denaturation, followed by denaturation cycle of 20 sec at 95°C, an annealing cycle of 15 sec at 40°C and an elongation and readout cycle of 30 sec at 72°C for 45 cycles. The specificity was verified by a dissociation curve analysis. Linear plots of the log copy number vs the number of the threshold cycles was consistently obtained for HPV16 L1 amplification and the correlation coefficient was between 0.995 to 1.000 in each run.
Detailed pathological classification and clinical stages of 252 breast cancer patients
Infiltrating Ductal Carcinoma (IDC) (218)
Stage I (14)
Stage II (83)
Stage III (114)
Stage IV (7)
Mixed IDC & mucinous (20)
Stage I (4)
Stage II (7)
Stage III (8)
Stage IV (1)
Medulllary Invasive carcinoma (8) Papillay invasive carcinoma (6)
Stage II (4)
Stage III (5)
Stage IV (5)
Despite breast cancer being one of the most frequently diagnosed cancers in women, the etiology and molecular pathobiology of breast carcinogenesis is still not clearly understood. In addition to various exogenous, endogenous, hormonal and genetic risk factors responsible for breast carcinogenesis, its viral etiology particularly implicating HPV remains highly controversial. Although HPV infection, particularly the HR-HPV types 16 and 18, have been strongly implicated in the development of cervical  and other cancers [53–63], the evidence for an oncogenic role of HPV in breast cancer is limited.
Our previous study on a limited number of patients  as well as several other reports worldwide [27–31] did not observe any infection of HPV in breast cancer, whereas a moderate (20-45%) to high frequency (60-85%) of HPV infection has been reported by many authors [33–42]. Recent reports of detection of very high rate of HPV infection in breast cancer up to 85% [43–46] and in breast cancer cell lines  prompted us to re-look into the prevailing condition of HPV infection in breast cancer which we refuted previously . Since in earlier study we used mainly fine needle aspirated (FNAC) cells from breast cancer patients (n = 26) including four tumor biopsy specimens to detect HPV, in the present study we have screened as many as 228 sporadic breast cancer biopsy specimens and 142 blood samples from a total of 252 breast cancer patients with no history of HPV infection or HPV-associated malignancies for the detection of HPV infection. The samples were collected from four different geographic regions of the country and two different PCR techniques both conventional and highly sensitive qRT-PCR were employed. The L1 consensus primers MY09/11 or GP5+/GP6+ and HPV16 E6/E7 (Table 2) which detect as may as 40 mucosal HPV genotypes, including the most prevalent high risk (HPV 16 & 18) and low risk (HPV 6 & 11) types were used but none of the samples by either methods revealed presence of HPV DNA. Additionally, blood samples from 24 familial breast cancer cases which had defined hereditary etiology for development of breast cancer failed to show presence of HPV DNA.
Of 22 previous studies on HPV in breast cancer till date, 15 reported presence of HPV infection in breast cancer and the authors have tried to put forward their possible explanation for detection of HPV DNA in breast cancer. Although the spreading of genital HPV infection from one site to the other is not established, a few studies have reported detection of genital HPVs in peripheral blood lymphocytes of patients with urino-genital cancers [64–67] and head & neck cancers . So, it has been suggested that, there is a possibility of systemic spread of oncogenic virus through organ perfusion  facilitating its entry into the breast through circulation. For this reason we tried to look for HPV DNA in blood samples of 142 breast cancer patients from Bangalore, North-east region, J & K and Goa but none of them was found positive for HPV DNA. However, the detection of genital HPVs in the nipple and areolar region reported by de Villers et al.  suggests an alternative and perhaps more likely route of infection. Because of varied sexual behavior it is possible that genital HPVs may transmit to breast through oro-genital route or directly through genital-breast contacts. So there could be transmission of HPV infection by mechanical path where the virus is scrubbed through the skin . However, the lack of detection of HPV in breast cancer indicates that the virus has no role to play in breast carcinogenesis in Indian women.
List of studies identified HPV DNA sequences in breast cancer tissues
types n (%)
Di Lonardo et al., 1992
Henning et al., 1999
Yu et al., 1999
19 (HPV 33)
Yu et al., 2000
Liu et al., 2004
Damin et al., 2004
Widschwendter et al., 2004
de Villiers et al., 2005
Kroupis et al., 2006
Kan et al., 2005
Gumus et al., 2006
Khan et al., 2008
de Leon et al., 2009
Mendizabal-Ruiz et al., 2009
Heng et al., 2009
9 cell lines
List of studies that did not detect HPV DNA sequences in breast cancer tissues
types n (%)
Wrede et al., 1992
Bratthauer et al., 1992
Gopalkrishna et al., 1996
Czerwenka et al., 1996
Lindel et al., 2007
de Cremoux et al., 2008
Hedau et al. (Present study)
Similarly, from Austria, Widschwendter et al  analyzed only 11 cases of breast cancer, of which 7 (63.7%) had HPV infection while Czerwenka et al  from the same country reported complete absence of HPV infection in breast cancer cases. The reason(s) for disparity of presence or absence of HPV infection in breast cancer cases from the same country is not understood. It may be primarily because of selection of primer types and the amplicon region in the HPV genome which could be the possible explanation for the observed differences in HPV detection. It may also in part, be attributed to cross-contamination during collection and processing of biological samples from other organ sites, if infected with HPV.
Interestingly, in Brazilian women, Damin et al  could not observe HPV DNA in benign breast disease, but HPV could be detected in 25% of patients with breast carcinoma. However, HPV infection was found to have no correlation with prognosis of the disease. Lindel and her colleagues  showed no evidence of HPV infection in 81 Swiss women with breast carcinomas using the SPF1/2 primers covering about 40 different low, intermediate and high risk HPV types. Similarly, de Cremoux et al  analyzed 50 invasive breast carcinoma tissues from French patients using consensus and type-specific primers but no HPV infection were detected in any of breast cancer cases. Wrede et al  analyzed a group of 95 British women with breast cancer for the infection of HPV6b, 11, 13, 16, 18, 30, 31, 32, 33, 45 and 51 but they also failed to detect any HPV infection. Kroupis et al  performed HPV test on 107 breast carcinomas in Greece and only 17 (15.9%) were found positive. Many of them were having multiple infections of as many as 21 high risk HPV types and majority (14/17; 67%) of them were positive for HPV16. Yu et al  analyzed 72 patients from Shanghai, China and Tokushima in Japan found 34.1% positivity for HPV33 alone but there was no evidence of HPV16-positive breast cancer. Yet another study by Mendizabal-Ruiz et al  analyzed 67 breast cancer patients including 40 non-malignant tissues and a very low 4.4% (3/67) frequency of HPV infection was observed. Although there exists conflicting reports, it does not insinuate that the reports that did not find viruses in breast cancer specimens were attempting to confirm or refute previous reports but failed to detect HPV. However, it is also clear from these studies that presence of HPV infection in breast cancer may not be a universal phenomenon. The prevalence of HPV infection in breast cancer may differ between places and population and several factors may contribute to this effect. This is amply clear from a recent interesting study of Heng et al  who analyzed HPV DNA sequences in as many as nine human breast cancer cell lines including the commonly used MCF-7 cells but only two cell lines (MDA-MB-175 VII and SK-BR-3) were found positive for HPV18. It is, however, not unlikely that these two breast cancer cell lines might have got contaminated in the laboratory with most commonly used HeLa cells that harbor HPV18.
Several other authors from different parts of the world reported presence of HPV infection in breast cancer cases. It is, however, most important to note that not many studies have indicated or analyzed if the women with breast cancer recruited for HPV detection also had anogenital or oropharynheal lesions with HPV infection. Although the route of HPV transmission from one organ to the other is not clear, Hening et al  demonstrated HPV16 in 46% of breast carcinoma patients who had a history of CIN III lesions. Most interestingly, all patients with HPV16 positive for breast cancer correspond to same patients with cervical CIN III lesions with HPV16 infection. This is indicative of possible transmission of virus from ano-genital organs to the breast. One of the route discussed earlier could be through blood circulation [64–68]. So, it is essential to look for genital or oropharyngeal infection of HPV in breast cancer patients to rule out the possibility of inter-organ transmission and/or cross contamination of viral infection. However, published data suggest that various epidemiological factors, sexual behavior including the history of HPV-associated diseases specific to the region may play a role in differential distribution of HPV in breast cancer .
In spite of exceedingly higher prevalence of genital HPV infection in India as compared to that in Europe and in the USA including presence of other conducive risk factors such as early age marriage, multiple pregnancy, malnutrition, poor hygiene and healthcare, the complete absence of HPV infection in Indian women with breast cancer in the present study does not suggest the role of HPV in breast carcinogenesis in Indian women. It is suggested that although HPV DNA is undetectable, serologic assay may be useful in revealing exposure by detecting presence of antibodies against HPV. But natural HPV infection being poorly immunogenic, the antibody titer will be too low to be detected with the existing serological tests. HPV serology is presently not available in our laboratory and is being developed under the WHO LabNet programme. We however, do not preclude the possibility of yet unidentified HPV playing important role in breast carcinogenesis in India. Furthermore, due to the changing social and psyco-sexual behavior particularly in urban Indian population, it may not be unlikely to find, presence of HPV in breast tissue in future due to an exterior transfer of HPV form genital organs to the breast.
Complete absence of HPV DNA either in the tumor tissue or in the blood of the same breast cancer patients recruited from four different regions of the country by employing the highly sensitive qRT-PCR does not support the etiological role of oncogenic HPV in the pathogenesis of breast cancer in Indian women.
human papilloma virus
polymerase chain reaction and Breast carcinoma
We thank ICMR for financial assistance for cancer research project to North-east regions and Department of Science and Technology (DST), Govt. of India for the project on expression and mutation of breast cancer susceptibility genes in Indian women. RK is grateful to CSIR for financial support.
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