Human Breast Cancer Incidence Research Articles

Exploring the presence of bovine leukemia virus among breast cancer tumors in a rural state.

The bovine leukemia virus (BLV) is a deltaretrovirus that causes malignant lymphoma and lymphosarcomas in cattle globally and has high prevalence among large scale U.S. dairy herds. Associations between presence of BLV DNA in human mammary tissue and human breast cancer incidence have been reported. We sought to estimate the prevalence of BLV DNA in breast cancer tissue samples in a rural state with an active dairy industry. We purified genomic DNA from 56 fresh-frozen breast cancer tissue samples (51 tumor samples, 5 samples representing adjacent normal breast tissue) banked between 2016 and 2019. Using nested PCR assays, multiple BLV tax sequence primers and primers for the long terminal repeat (LTR) were used to detect BLV DNA in tissue samples and known positive control samples, including the permanently infected fetal lamb kidney cell line (FLK-BLV) and blood from BLV positive cattle. The median age of patients from which samples were obtained at the time of treatment was 60 (40-93) and all were female. Ninety percent of patients had invasive ductal carcinoma. The majority were poorly differentiated (60%). On PCR assay, none of the tumor samples tested positive for BLV DNA, despite having consistent signals in positive controls. We did not find BLV DNA in fresh-frozen breast cancer tumors from patients presenting to a hospital in Vermont. Our findings suggest a low prevalence of BLV in our patient population and a need to reevaluate the association between BLV and human breast cancer.

Revisiting the MMTV Zoonotic Hypothesis to Account for Geographic Variation in Breast Cancer Incidence.

Human breast cancer incidence varies by geographic location. More than 20 years ago, we proposed that zoonotic transmission of the mouse mammary tumor virus (MMTV) from the western European house mouse, Mus musculus domesticus, might account for the regional differences in breast cancer incidence. In the intervening years, several developments provide additional support for this hypothesis, including the limited impact of genetic factors for breast cancer susceptibility revealed by genome-wide association studies and the strong effect of antiretroviral therapy to reduce breast cancer incidence. At the same time, economic globalization has further expanded the distribution of M. m. domesticus to Asia, leading to a significant increase in breast cancer incidence in this region. Here, we revisit this evidence and provide an update to the MMTV zoonotic hypothesis for human breast cancer at a time when the world is recovering from the global COVID-19 zoonotic pandemic. We present evidence that mouse population outbreaks are correlated with spikes in breast cancer incidence in Australia and New Zealand and that globalization has increased the range of M. m. domesticus and MMTV. Given the success of global vaccination campaigns for HPV to eradicate cervical cancer, a similar strategy for MMTV may be warranted. Until breast cancer incidence is reduced by such an approach, zoonotic transmission of MMTV from mice to humans as an etiologic factor for breast cancer will remain controversial.

Prevalence and characteristics of mouse mammary tumor virus-like virus associated breast cancer in China

BackgroundDespite extensive molecular epidemiological studies, the prevalence and characteristics of Mouse Mammary Tumor Virus-Like Virus (MMTV-LV) in Chinese women breast cancer are still unclear. Besides, the prevalence of MMTV-LV in women breast cancer tissue varies in different countries and its dependent factors remain inconclusive.MethodsIn the first part of the study, a case-control study was performed. 119 breast cancer samples (84 from Northern China and 35 from Southern China) and 50 breast fibroadenoma specimens were collected from Chinese women patients. MMTV-like env sequence and the homology to MMTV env gene were analysed by semi-nested polymerase chain reaction (PCR). We also explored the association of MMTV-LV prevalence with sample sources (Southern and Northern China) and patients’ clinicopathological characteristics. To investigate the dependent factors of the prevalence of MMTV-LV in breast cancer worldwide, a meta-analysis was conducted in the second part of the study.ResultsWe found that the prevalence of MMTV-LV was much higher in breast cancer tissues (17.65%) than that in breast fibroadenoma specimens (4.00%) (P < 0.05). MMTV-LV prevalence in Chinese women breast cancer tissues was significantly different between Southern China (5.71%) and Northern China (22.62%) (P < 0.05). The prevalence of MMTV-LV also associates significantly with expression of HER2, but shows no significant correlation with other parameters. In the meta-analysis, we found that MMTV-LV prevalence in breast cancer tissue was dependent on the distribution of M. domesticus mouse (M. d), M. musculus mouse (M.m) and M.castaneus mouse (M.c) worldwide (P < 0.05).ConclusionThe distribution of house mice may be a crucial environmental factor that explains the geographic differences in human breast cancer incidence. Our findings may provide a potential avenue of prevention, diagnosis and treatment for breast cancer.

Zinc enhances CDKN2A, pRb1 expression and regulates functional apoptosis via upregulation of p53 and p21 expression in human breast cancer MCF-7 cell.

Zinc (Zn) is an essential trace elements, its deficiency is associated with increased incidence of human breast cancer. We aimed to study the effect of Zn on human breast cancer MCF-7 cells cultured in Zn depleted and Zn adequate medium. We found increased cancer cell growth in zinc depleted condition, further Zn supplementation inhibits the viability of breast cancer MCF-7 cell cultured in Zn deficient condition and the IC25, IC50 value for Zn is 6.2μM, 15μM, respectively after 48h. Zn markedly induced apoptosis through the characteristic apoptotic morphological changes and DNA fragmentation after 48h. In addition, Zn deficient cells significantly triggered intracellular ROS level and develop oxidative stress induced DNA damage; it was confirmed by elevated expression of CYP1A, GPX, GSK3β and TNF-α gene. Zinc depleted MCF-7 cells expressed significantly (p≤0.001) decreased levels of CDKN2A, pRb1, p53 and increased the level of mdm2 expression. Zn supplementation (IC50=15μM), increased significantly CDKN2A, pRB1 & p53 and markedly reduced mdm2 expression; also protein expression levels of CDKN2A and pRb1 was significantly increased. In addition, intrinsic apoptotic pathway related genes such as Bax, caspase-3, 8, 9 & p21 expression was enhanced and finally induced cell apoptosis. In conclusion, physiological level of zinc is important to prevent DNA damage and MCF-7 cell proliferation via regulation of tumor suppressor gene.

Bisphenol A (BPA) Exposure In Utero Leads to Immunoregulatory Cytokine Dysregulation in the Mouse Mammary Gland: A Potential Mechanism Programming Breast Cancer Risk.

Bisphenol-A (BPA) is a ubiquitous estrogen-like endocrine disrupting compound (EDC). BPA exposure in utero has been linked to breast cancer and abnormal mammary gland development in mice. The recent rise in incidence of human breast cancer and decreased age of first detection suggests a possible environmental etiology. We hypothesized that developmental programming of carcinogenesis may involve an aberrant immune response. Both innate and adaptive immunity play a role in tumor suppression through cytolytic CD8, NK, and Th1 T-cells. We hypothesized that BPA exposure in utero would lead to dysregulation of both innate and adaptive immunity in the mammary gland. CD1 mice were exposed to BPA in utero during gestation (days 9-21) via osmotic minipump. At 6weeks, the female offspring were ovariectomized and estradiol was given at 8weeks. RNA and protein were extracted from the posterior mammary glands, and the mRNA and protein levels were measured by PCR array, qRT-PCR, and western blot. In mouse mammary tissue, BPA exposure in utero significantly decreased the expression of members of the chemokine CXC family (Cxcl2, Cxcl4, Cxcl14, and Ccl20), interleukin 1 (Il1) gene family (Il1β and Il1rn), interleukin 2 gene family (Il7 receptor), and interferon gene family (interferon regulatory factor 9 (Irf9), as well as immune response gene 1 (Irg1). Additionally, BPA exposure in utero decreased Esr1 receptor gene expression and increased Esr2 receptor gene expression. In utero exposure of BPA resulted in significant changes to inflammatory modulators within mammary tissue. We suggest that dysregulation of inflammatory cytokines, both pro-inflammatory and anti-inflammatory, leads to a microenvironment that may promote disordered cell growth through inhibition of the immune response that targets cancer cells.

Abstract 5143: Rats heterozygous for Pten develop fibroadenoma and adenocarcinoma arising from the mammary gland

Abstract To further characterize the function of the tumor suppressor Pten in the role of tumorigenesis we have created a colony of Pten mutant Sprague Dawley (SD) rats. Utilizing zinc finger nuclease technology we introduced a 7bp deletion in Exon 7 of the Pten gene, creating a frameshift mutation and an early stop codon. Pten homozygous null animals are not viable so a colony of heterozygous animals is maintained. Spontaneous tumors of the mammary gland arise in these animals and were removed for staining and pathological analysis. We describe briefly the creation of this model and preliminary genotypic and proteomic characterization. Further we describe pathological observations made on tumor tissues removed from aging Pten heterozygous animals. We have confirmed a reduction in Pten expression by Western Blot utilizing a monoclonal antibody targeting a central locus in the protein. Heterozygous Pten animals develop spontaneous tumors of the mammary gland which were removed if animals demonstrated deteriorating health or any condition within our Humane Care and Use guidelines. Thirty six tissues from 16 animals were submitted for histopathological analysis. Eight of the animals were male, 8 of the animals were female and had a mean lifespan of 159 days (165 male, 153 female). Remaining consistent with human breast cancer incidence in women below 30 years of age, the most common lesion observed is a benign fibroadenoma (30/36 samples). The malignant adenocarcinoma was observed in 5/36 samples submitted. Fibroadenoma only lesions were observed in 12 of the 16 rats while both fibroadenoma and adenocarcinoma was observed in 4 of the 16 rats. Taken together we believe that a Pten heterozygous rat provides an additional tool for the elucidation of the role of Pten in human cancers. This model may also be useful in the study of neurological disorders such as Autism, Parkinson's disease, Alzheimer's disease, obesity, cardiovascular disease, and diabetes. Mutations in Pten strongly correlate with several human disorders including Cowden syndrome, Bannayan-Zonana syndrome, and Lhermitte-Duclos disease. These disorders result in a tumor pathologies including an increased risk for breast cancers. Citation Format: Aaron M. McCoy, Bala Manickam, Lara Reid, Edward Weinstein, Xiaoxia Cui. Rats heterozygous for Pten develop fibroadenoma and adenocarcinoma arising from the mammary gland. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5143. doi:10.1158/1538-7445.AM2015-5143

Global breast cancer seasonality

Human breast cancer incidence has seasonal patterns that seem to vary among global populations. The aggregate monthly frequency of breast cancer diagnosis was collected and examined for 2,921,714 breast cancer cases diagnosed across 64 global regions over spans from 2 to 53 years. Breast cancer is consistently diagnosed more often in spring and fall, both in the Northern and Southern Hemispheres, regardless of presumable menopausal status (<or=50, >50). This seasonality is increasingly more prominent as population distance from the equator increases and this latitude dependence is most pronounced among women living in rural areas. Moreover, the overall annual incidence (2005-2006), per 100,000 population, of breast cancer increased as the latitude of population residence increased. These data make it clear that human breast cancer discovery occurs non-randomly throughout each year with peaks near both equinoxes and valleys near both solstices. This stable global breast cancer seasonality has implications for better prevention, more accurate screening, earlier diagnosis, and more effective treatment. This complex latitude-dependent breast cancer seasonality is clearly related to predictable local day/night length changes which occur seasonally. Its mechanism may depend upon seasonal sunlight mediation of vitamin D and seasonal mediation of nocturnal melatonin peak level and duration.

Polymorphisms of the SIPA1 gene and sporadic breast cancer susceptibility

BackgroundThe novel breast cancer metastasis modulator gene signal-induced proliferation-associated 1 (Sipa1) underlies the breast cancer metastasis efficiency modifier locus Mtes 1 and has been shown to influence mammary tumour metastatic efficiency in the mouse, with an ectopically expressing Sipa1 cell line developing 1.5 to 2 fold more surface pulmonary metastases. Sipa1 encodes a mitogen-inducible GTPase activating (GAP) protein for members of the Ras-related proteins; participates in cell adhesion and modulates mitogen-induced cell cycle progression. Germline SIPA1 SNPs showed association with positive lymph node metastasis and hormonal receptor status in a Caucasian cohort. We hypothesized that SIPA1 may also be correlated to breast carcinoma incidence as well as prognosis. Therefore, this study investigated the potential relationship of SIPA1 and human breast cancer incidence by a germline SNP genotype frequency association study in a case-control Caucasian cohort in Queensland, Australia.MethodsThe SNPs genotyped in this study were identified in a previous study and the genotyping assays were carried out using TaqMan SNP Genotyping Assays. The data were analysed with chi-square method and the Monte Carlo style CLUMP analysis program.ResultsResults indicated significance with SIPA1 SNP rs3741378; the CC genotype was more frequently observed in the breast cancer group compared to the disease-free control group, indicating the variant C allele was associated with increased breast cancer incidence.ConclusionThis observation indicates SNP rs3741378 as a novel potential sporadic breast cancer predisposition SNP. While it showed association with hormonal receptor status in breast cancer group in a previous pilot study, this exonic missense SNP (Ser (S) to Phe (F)) changes a hydrophilic residue (S) to a hydrophobic residue (F) and may significantly alter the protein functions of SIPA1 in breast tumourgenesis. SIPA1 SNPs rs931127 (5' near gene), and rs746429 (synonymous (Ala (A) to Ala (A)), did not show significant associations with breast cancer incidence, yet were associated with lymph node metastasis in the previous study. This suggests that SIPA1 may be involved in different stages of breast carcinogenesis and since this study replicates a previous study of the associated SNP, it implicates variants of the SIPA1 gene as playing a potential role in breast cancer.

Seasonal modulation of post-resection breast cancer metastasis

Human breast cancer incidence, histopathologic grade, invasiveness, and mortality risk vary significantly throughout each year. In order to better understand this seasonal cancer biology, we investigated the circannual pattern of post-resection breast cancer metastasis, under genetically and environmentally controlled conditions. Over a span of 14 consecutive years, we conducted 22 similar experiments to investigate metastatic biology of breast cancer among 1,214 C3HeB/FeJ female mice. All mice were kept in temperature-controlled environment with 12 h light:12 h dark photoperiod, with food and water freely available, from birth until death. At 10-13 weeks of age, each mouse received 20,000 viable syngeneic mammary cancer cells subcutaneously and the tumor bearing leg was resected 10-12 days after tumor inoculation for potential cure. Once 10% of resected mice were found moribund, due to autopsy proven pulmonary metastases, all remaining mice were sacrificed and metastatic lung nodules were counted. The incidence of post-resection pulmonary metastasis was not randomly distributed throughout the year, but peaked prominently in Summer and Winter. Although tumor volume at resection was strongly associated with metastatic potential, a significantly higher probability of pulmonary metastasis was observed if surgery was performed in Summer and Winter, regardless of tumor volume at resection, compared to Spring and Fall. These results support the likelihood that human breast cancer seasonality is real and of biological origin. There are implications of this cancer chronobiology for breast cancer prevention, screening, diagnosis, and treatment.

Identification of a retrovirus in human breast cancer

548 Background: Breast cancer (BC) in mice is caused by mouse mammary tumor virus (MMTV). We have reported that 38% of BC in American women contain envelope gene sequences, 95% to 99% homologous to the env gene of MMTV implying the presence of a human mammary tumor virus (HMTV) (Cancer Res 55, 5173; 1995). Env positivity is high in regions with high incidence of BC (Western Europe, North Africa, the Americas, Australia) and low in low regions (Asia, Asia Minor) (Clin Cancer Res 10, 5647; 2004). Methods: Polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR), and nucleotide sequencing were performed by standard Methods: Env positive breast cancer cells were co-cultured for five days through a micropore barrier with normal breast or peripheral blood mononuclear cells (PBMC). Results: A complete 9.9 kb proviral structure has been identified, 95% homologous to MMTV. Unique differences from MMTV are systematically found in the long terminal repeat (LTR) gene of the HMTV. Normal tissues of the same patient do not contain sequences, thereby excluding endogenous sequences and genetic inheritance as mechanisms of transmission. In six of twelve experiments viral sequences were transferred to allogeneic breast cells and in four of six to allogeneic PBMC as detected by specific monoclonal antibody staining and by PCR. Conclusions: HMTV is an infectious agent, horizontally acquired, that can be transmitted from BC cells in vitro. These data establish that a substantial proportion of human BC is associated with a viral agent, HMTV, closely similar to MMTV, which is known to cause mammary tumors in mice. The correlation of HMTV with human BC incidence is consistent with considerations of causality. No significant financial relationships to disclose.

Gene expression profiling of chemically induced rat mammary gland cancer

Exposure to carcinogens through diet, the atmosphere and other means is generally regarded as influencing human cancer risk, but the impact of specific environmental carcinogens on human breast cancer incidence is still unknown. We examined whether distinct chemical carcinogens induce a unique transcriptional profile in mammary gland cancer that is characteristic of the etiologic agent. Rat mammary gland cancers (n = 34) were generated by various carcinogens, including the food-derived heterocyclic amines 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 7,12-dimethylbenz[a]anthracene, N-nitrosomethylurea and 4-aminobiphenyl. The histopathology of the carcinomas was graded using a modified Scarff-Bloom-Richardson scheme and the gene expression profiles in the carcinomas were evaluated on a 10K cDNA microarray. Unsupervised hierarchical clustering analysis revealed two major clusters of carcinomas irrespective of the carcinogenic agent that distinguished two groups with different histopathological parameters (degree of differentiation, nuclear grade, mitotic activity, epithelial cell growth pattern and necrosis). Using class comparison analysis and hierarchical clustering of all carcinomas irrespective of histopathology, gene expression profiles were further shown to be statistically differentially expressed according to the carcinogenic agent. These findings indicate that the transcriptional program in carcinomas is unique to the etiologic agent and can be observed among a diverse set of carcinogens despite variations in carcinoma histopathology. The ability to use microarray analysis to discern an etiology-specific profile among a pathologically heterogeneous group of breast carcinomas may ultimately be valuable in determining the role of environmental chemical carcinogens in human breast cancer risk.

Breast cancer incidence highest in the range of one species of house mouse, Mus domesticus

Incidence of human breast cancer (HBC) varies geographically, but to date no environmental factor has explained this variation. Previously, we reported a 44% reduction in the incidence of breast cancer in women fully immunosuppressed following organ transplantation (Stewart et al (1995) Lancet346: 796–798). In mice infected with the mouse mammary tumour virus (MMTV), immunosuppression also reduces the incidence of mammary tumours. DNA with 95% identity to MMTV is detected in 40% of human breast tumours (Wang et al (1995) Cancer Res55: 5173–5179). These findings led us to ask whether the incidence of HBC could be correlated with the natural ranges of different species of wild mice. We found that the highest incidence of HBC worldwide occurs in lands where Mus domesticus is thse resident native or introduced species of house mouse. Given the similar responses of humans and mice to immunosuppression, the near identity between human and mouse MTV DNA sequences, and the close association between HBC incidence and mouse ranges, we propose that humans acquire MMTV from mice. This zoonotic theory for a mouse-viral cause of HBC allows testable predictions and has potential importance in prevention. © 2000 Cancer Research Campaign

The relationship of dietary selenium and breast cancer.

An inverse relationship exists between dietary selenium (Se) concentrations and the incidence of human breast cancer. The addition of Se to the diet has been shown to decrease the incidence of spontaneous murine mammary tumors. We compared the serum Se concentrations in breast cancer patients with those of women without breast cancer. Serum was collected from 35 women with breast cancer. Nineteen of these women had infiltrating ductal carcinoma and two had Paget disease of the nipple. Nine women had lymph nodal metastases at the time of mastectomy, four had definite evidence of metastatic disease when the blood samples were drawn, and the disease process of one patient was unclassified. Samples from 27 women known to be free of breast cancer were used as controls. The difference noted between the mean serum Se concentrations of breast cancer patients and controls were found to be significant.

7,12-Dimethylbenz(α)anthracene(DMBA)による乳癌誘発に及ぼすアルギニン・インバランスの影響に関する実験的研究

Incidence of human breast cancer is high in developed countries and low in undeveloped countries with the notable exception of Japan. Among the factors responsible for the incidence of breast cancer, genetic, racial, hormonal and nutritional factors were thought to be important modifiers. Because of the paucity of information dealing with the relationship between mammary carcinogenesis and dietary protein, a further study of this problem seems justified.In this paper, to clarify the relationship between dietary protein and mammary carcinogenesis, the following experiments were undertaken. Part I of this study is concerned with the effect of arginine imbalanced diets and various proportions of casein diets on genesis and growth of mammary carcinoma in rats induced by 7,12-DMBA. The experimental animals were female Sprague-Dawley rats. The diets used in this experiment were as follows: Group I.50% casein diet Group II.20% casein diet Group III.8% casein diet Group IV.15% casein supplemented with 5% arginine Group V. CMF type of pellet (Oriental Yeast Co. ) These diets were given isocalorically every day. The rats were injected with 3 mg of DMBA at the age of 52 and 55 days. All animals were examined every day during the experimental period, and the onset and evolution of the tumors were recorded. The following results were obtained: 1. The normal body growth rates were not retarded on arginine imbalanced diets, and no ill effects of arginine were shown.