ABSTRACT
Although recent advances in breast cancer treatment regimes have improved patient prognosis, resistance to breast cancer therapies, such as radiotherapy, is still a major clinical challenge. In the current study, we have investigated the role of autocrine human GH (hGH) in resistance to ionising radiation (IR)-based therapy. Cell viability and total cell number assays demonstrated that autocrine hGH promoted cell regrowth in the mammary carcinoma cell lines, MDA-MB-435S and T47D, and the endometrial carcinoma cell line, RL95-2, following treatment with IR. In addition, autocrine hGH enhanced MDA-MB-435S and T47D cell clonogenic survival following radiation exposure. The enhanced clonogenic survival afforded by autocrine hGH was mediated by JAK2 and Src kinases. Investigation into the DNA repair capacity demonstrated that autocrine hGH reduced IR-induced DNA damage in MDA-MB-435S and T47D cells. Functional antagonism of hGH increased RL95-2 sensitivity to IR in cell viability and total cell number assays, reduced clonogenic survival and enhanced the induction of DNA damage. Thus, autocrine hGH reduced sensitivity to treatment with IR in mammary and endometrial carcinoma cell lines in vitro, while functional antagonism of hGH sensitised endometrial carcinoma cells to IR. Functional antagonism of hGH, used in conjunction with radiotherapy, may therefore enhance treatment efficacy and improve the prognosis of patients with breast and endometrial cancer.
Subject(s)
Breast Neoplasms/metabolism , Endometrial Neoplasms/metabolism , Human Growth Hormone/metabolism , Radiation Tolerance/physiology , Animals , Apoptosis/drug effects , Apoptosis/radiation effects , Breast Neoplasms/pathology , Breast Neoplasms/radiotherapy , Cell Line, Tumor , Cell Survival/drug effects , Cell Survival/radiation effects , DNA Damage/drug effects , Endometrial Neoplasms/pathology , Endometrial Neoplasms/radiotherapy , Female , Gene Expression Regulation, Neoplastic , Human Growth Hormone/analogs & derivatives , Human Growth Hormone/antagonists & inhibitors , Human Growth Hormone/genetics , Human Growth Hormone/pharmacology , Humans , Mice , Radiation Tolerance/drug effects , Radiation, Ionizing , Radiation-Protective Agents/pharmacology , Tumor Burden/drug effects , Xenograft Model Antitumor AssaysABSTRACT
Deregulated PAX5 expression has been associated with metastatic mammary carcinoma, although the precise role of PAX5 in cancer progression is unclear. Stable forced expression of PAX5alpha in the mammary carcinoma cell lines MCF-7 and MDA-MB-231 reduced cell cycle progression, cell survival, and anchorage-independent cell growth. In xenograft studies, forced expression of PAX5alpha was associated with a significant reduction in tumor volume. Furthermore, forced expression of PAX5alpha in mammary carcinoma cells resulted in altered cell morphology with resultant enhancement of epithelial cell characteristics. Morphologic changes were associated with localization of beta-CATENIN at cell-cell junctions and with altered mRNA expression of mesenchymal markers in mammary carcinoma cells. In addition, forced expression of PAX5alpha in MCF-7 and MDA-MB-231 cells significantly reduced cell migration and invasion. Concomitantly, small interfering RNA-mediated depletion of PAX5alpha increased MCF-7 total cell number, cell motility, migration, and invasion. These studies show that PAX5alpha enhances the epithelial characteristics of mammary carcinoma cells, reminiscent of mesenchymal to epithelial transition.
Subject(s)
Breast Neoplasms/metabolism , Carcinoma/metabolism , Cell Dedifferentiation/physiology , Epithelial Cells/metabolism , PAX5 Transcription Factor/metabolism , Tumor Suppressor Proteins/metabolism , Biomarkers/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Carcinoma/genetics , Carcinoma/pathology , Cell Count , Cell Differentiation/genetics , Cell Line, Tumor , Cell Movement/genetics , Cell Transformation, Neoplastic/genetics , Cell Transformation, Neoplastic/metabolism , Down-Regulation/genetics , Epithelial Cells/cytology , Female , Gene Expression Regulation, Neoplastic/genetics , Humans , Intercellular Junctions/metabolism , Intercellular Junctions/ultrastructure , Mesoderm/cytology , Mesoderm/metabolism , Neoplasm Invasiveness/genetics , Neoplasm Invasiveness/physiopathology , PAX5 Transcription Factor/genetics , RNA Interference/physiology , RNA, Messenger/metabolism , Tumor Suppressor Proteins/genetics , beta Catenin/metabolismABSTRACT
Accumulating literature implicates pathological angiogenesis and lymphangiogenesis as playing key roles in tumor progression. Autocrine human growth hormone (hGH) is a wild-type orthotopically expressed oncogene for the human mammary epithelial cell. Herein we demonstrate that autocrine hGH expression in the human mammary carcinoma cell line MCF-7 stimulated the survival, proliferation, migration, and invasion of a human microvascular endothelial cell line (HMEC-1). Autocrine/paracrine hGH secreted from mammary carcinoma cells also promoted HMEC-1 in vitro tube formation as a consequence of increased vascular endothelial growth factor-A (VEGF-A) expression. Semiquantitative RT-PCR analysis demonstrated that HMEC-1 cells express both hGH and the hGH receptor (hGHR). Functional antagonism of HMEC-1-derived hGH reduced HMEC-1 survival, proliferation, migration/invasion, and tube formation in vitro. Autocrine/paracrine hGH secreted by mammary carcinoma cells increased tumor blood and lymphatic microvessel density in a xenograft model of human mammary carcinoma. Autocrine hGH is therefore a potential master regulator of tumor neovascularization, coordinating two critical processes in mammary neoplastic progression, angiogenesis and lymphangiogenesis. Consideration of hGH antagonism to inhibit angiogenic processes in mammary carcinoma is therefore warranted.
