Expression of biomarkers for transformation in 7,12-dimethylbenz[a]anthracene-treated mammary epithelial-cells

Drug-Resistant Stem Cells: Novel Approach for Colon Cancer Therapy

Metastatic progression of female breast and colon cancer represents a major cause of mortality in women. Spontaneous/acquired resistance to conventional and targeted chemo-endocrine therapy is associated with the emergence of drug-resistant tumor-initiating cancer stem cell populations. The cancer-initiating premalignant stem cells exhibit activation of select cancer cell signaling pathways and undergo epithelial–mesenchymal transition, leading to the evolution of a metastatic phenotype. The development of reliable cancer stem cell models provides valuable experimental approaches to identify novel testable therapeutic alternatives for therapy-resistant cancer. Drug-resistant stem cell models for molecular subtypes of clinical breast cancer and for genetically predisposed colon cancer are developed by selecting epithelial cells that survive in the presence of cytostatic concentrations of relevant therapeutic agents. These putative stem cells are characterized by the expression status of select cellular and molecular stem cell markers. The stem cell models are utilized as experimental approaches to examine the stem-cell-targeted growth inhibitory efficacy of naturally occurring dietary phytochemicals. The present review provides a systematic discussion on (i) conceptual and experimental aspects relevant to the chemo-endocrine therapy of breast and colon cancer, (ii) molecular/cellular aspects of cancer stem cells and (iii) potential stem-cell-targeting lead compounds as testable alternatives against the progression of therapy-resistant breast and colon cancer.

Epithelial cell culture models for the prevention and therapy of clinical breast cancer (Review)

Clinical breast cancer progresses via a multi-step carcinogenic process wherein genetic, molecular, endocrine and dietary factors play significant roles in the pathogenesis, prevention and therapy of the disease. Preclinical cell culture models, expressing clinically relevant genetic and endocrine defects and exhibiting quantifiable cancer risk, may provide facile, clinically translatable approaches to identify molecular targets and susceptible mechanistic pathways for the efficacy of novel interventional approaches. This review summarizes laboratory investigations focused on i) developing murine and human mammary tissue-derived cell culture models; ii) optimizing mechanism-based quantitative endpoint biomarker assays specific for carcinogenic risk and preventive/therapeutic efficacy; and iii) providing quantifiable proof-of-principle evidence for validation of the present cell culture approaches, capable of prioritizing efficacious lead compounds for subsequent in vivo animal studies and clinical trials for the prevention/therapy of breast cancer. Epithelial cell culture models are developed and characterized where the carcinogenic process is initiated by the targeted expression of clinically relevant oncogenes. The cell culture systems from mouse mammary tissue are in vitro approaches that complement the Ras and Myc transgenic mouse models. The human mammary tissue-derived systems are in vitro models for chemoendocrine, therapy-resistant, clinical, pre-invasive ER(-)/PR(-)/HER-2(+) comedo ductal carcinoma in situ, ER(+)/PR(+) chemoendocrine therapy-responsive breast cancer and ER(-)/PR(-)/HER-2(-) triple-negative chemoendocrine, therapy-resistant breast cancer. The oncogene-initiated phenotypes exhibit loss of homeostatic growth control, downregulation of cell apoptosis and gain of carcinogenic risk in vitro, as well as transplantable tumor development in vivo. Numerous mechanistically distinct, synthetic pharmacological agents, as well as naturally occurring dietary compounds, re-establish homeostatic growth control via cell cycle arrest and/or induction of cell apoptosis, downregulate oncogene-mediated cell signaling pathways, modulate the expression of numerous cell cycle regulatory and apoptosis-specific proteins and reduce carcinogenic risk in pre-neoplastic and carcinoma-derived cell culture models. These data validate the present cell culture approaches as novel, mechanism-based screens to evaluate and prioritize promising lead compounds for the prevention/therapy of clinical breast cancer.