On the molecular biology of breast cancer

The Role of Extracellular Matrix Proteins in Breast Cancer

The extracellular matrix is a structure composed of many molecules, including fibrillar (types I, II, III, V, XI, XXIV, XXVII) and non-fibrillar collagens (mainly basement membrane collagens: types IV, VIII, X), non-collagenous glycoproteins (elastin, laminin, fibronectin, thrombospondin, tenascin, osteopontin, osteonectin, entactin, periostin) embedded in a gel of negatively charged water-retaining glycosaminoglycans (GAGs) such as non-sulfated hyaluronic acid (HA) and sulfated GAGs which are linked to a core protein to form proteoglycans (PGs). This highly dynamic molecular network provides critical biochemical and biomechanical cues that mediate the cell–cell and cell–matrix interactions, influence cell growth, migration and differentiation and serve as a reservoir of cytokines and growth factors’ action. The breakdown of normal ECM and its replacement with tumor ECM modulate the tumor microenvironment (TME) composition and is an essential part of tumorigenesis and metastasis, acting as key driver for malignant progression. Abnormal ECM also deregulate behavior of stromal cells as well as facilitating tumor-associated angiogenesis and inflammation. Thus, the tumor matrix modulates each of the classically defined hallmarks of cancer promoting the growth, survival and invasion of the cancer. Moreover, various ECM-derived components modulate the immune response affecting T cells, tumor-associated macrophages (TAM), dendritic cells and cancer-associated fibroblasts (CAF). This review article considers the role that extracellular matrix play in breast cancer. Determining the detailed connections between the ECM and cellular processes has helped to identify novel disease markers and therapeutic targets.

Prediction of years of life after diagnosis of breast cancer using omics and omic-by-treatment interactions

Breast cancer (BC) is the second most common type of cancer and a major cause of death for women. Commonly, BC patients are assigned to risk groups based on the combination of prognostic and prediction factors (eg, patient age, tumor size, tumor grade, hormone receptor status, etc). Although this approach is able to identify risk groups with different prognosis, patients are highly heterogeneous in their response to treatments. To improve the prediction of BC patients, we extended clinical models (including prognostic and prediction factors with whole-omic data) to integrate omics profiles for gene expression and copy number variants (CNVs). We describe a modeling framework that is able to incorporate clinical risk factors, high-dimensional omics profiles, and interactions between omics and non-omic factors (eg, treatment). We used the proposed modeling framework and data from METABRIC (Molecular Taxonomy of Breast Cancer Consortium) to assess the impact on the accuracy of BC patient survival predictions when omics and omic-by-treatment interactions are being considered. Our analysis shows that omics and omic-by-treatment interactions explain a sizable fraction of the variance on survival time that is not explained by commonly used clinical covariates. The sizable interaction effects observed, together with the increase in prediction accuracy, suggest that whole-omic profiles could be used to improve prognosis prediction among BC patients.

Menopausal status does not predict Oncotype DX recurrence score

BACKGROUND

Adjuvant treatment for early stage, estrogen receptor (ER) positive invasive breast cancer has been based on prognosticators such as menopausal status. The recurrence score (RS) from the 21-gene assay Oncotype DX (ODX) is predictive of a 10-y distant recurrence in this population but is rarely applied to premenopausal patients. The relationship between menopausal status and RS was evaluated.

MATERIALS AND METHODS

An institutional review board-approved retrospective review was conducted of invasive breast cancer patients with known RS. ODX eligibility was based on National Comprehensive Cancer Network guidelines or physician discretion. Perimenopausal women were classified as premenopausal for statistical analyses. Comparisons of menopausal status and RS were made using general linear regression model and the exact Wilcoxon rank-sum test.

RESULTS

Menopausal status was available for 575 patients (142 premenopausal, 433 postmenopausal). Median age was 46 y for premenopausal and 62 y for postmenopausal. Median invasive tumor size was 1.5 cm for both cohorts. Mastectomy rate was higher in the premenopausal group (54.8%) than postmenopausal (42%; P = 0.0001). Premenopausal women had a higher local-regional recurrence rate (2.8% versus 0%; P = 0.0384) but distant recurrence and overall survival were not statistically different (P = 0.6808). Median ER H-score was lower in premenopausal (H-score = 270) than postmenopausal women (H-score = 280; P < 0.0001). Median RS was 16 for both premenopausal (range, 0-54) and postmenopausal (range, 0-63) women. Menopausal status as a categorical variable was not predictive of RS (P-value = 0.6780).

CONCLUSIONS

Menopausal status has limited predictive power for distant recurrence. Therefore, menopausal status alone should not preclude performance of ODX in ER-positive, early stage breast cancer.

Reproductive and hormonal risk factors for luminal, HER2-overexpressing, and triple-negative breast cancer in Japanese women

BACKGROUND

Although the clinical relevance of the molecular subtypes of breast cancer is evident, etiological differences among subtypes have not been well established, especially among Asian. Here, we evaluated the hypothesis that the etiologic impact of reproductive and hormonal features differs among molecular subtypes.

MATERIALS AND METHODS

We conducted a case-control study in pre- and postmenopausal Japanese. We examined 706 breast cancer patients and 1412 age- and menopausal status-matched noncancer controls. Immunohistochemical stains for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2) were used to classify the cases into 554 luminal (hormone receptor positive), 84 HER2-overexpressing (hormone receptor negative, HER2 positive), and 68 triple-negative cases (hormone receptor negative, HER2 negative). Associations were evaluated using multivariate polytomous logistic regression models.

RESULTS

A significant association was observed between early age at menarche and risk of luminal disease (odds ratios = 1.67, 95% confidence interval: 1.22-2.29; P trend = 0.001). No significant differences in association with parity, age at first live birth, breastfeeding history, age at menopause, or synthetic hormonal use were seen across molecular subtypes of breast cancer.

CONCLUSIONS

These findings indicate that reproductive events in adolescence have differential impact on the risk of breast cancer molecular subtypes in Japanese.

Altered Endoplasmic Reticulum Calcium Pump Expression during Breast Tumorigenesis

Endoplasmic reticulum calcium homeostasis is involved in several essential cell functions including cell proliferation, protein synthesis, stress responses or secretion. Calcium uptake into the endoplasmic reticulum is performed by Sarco/Endoplasmic Reticulum Calcium ATPases (SERCA enzymes). In order to study endoplasmic reticulum calcium homeostasis in situ in mammary tissue, in this work SERCA3 expression was investigated in normal breast and in its benign and malignant lesions in function of the cell type, degree of malignancy, and histological and molecular parameters of the tumors. Our data indicate, that although normal breast acinar epithelial cells express SERCA3 abundantly, its expression is strongly decreased already in very early non-malignant epithelial lesions such as adenosis, and remains low in lobular carcinomas. Whereas normal duct epithelium expresses significant amounts of SERCA3, its expression is decreased in several benign ductal lesions, as well as in ductal adenocarcinoma. The loss of SERCA3 expression is correlated with Elston-Ellis grade, negative hormone receptor expression or triple negative status in ductal carcinomas. The concordance between decreased SERCA3 expression and several histological, as well as molecular markers of ductal carcinogenesis indicates that endoplasmic reticulum calcium homeostasis is remodeled during tumorigenesis in the breast epithelium.