ABSTRACT
Artemin (ARTN) has been reported to promote a TWIST1-dependent epithelial to mesenchymal transition of estrogen receptor negative mammary carcinoma (ER-MC) cells associated with metastasis and poor survival outcome. We therefore examined a potential role of ARTN in the promotion of the cancer stem cell (CSC)-like phenotype in mammary carcinoma cells. Acquired resistance of ER-MC cells to either ionizing radiation (IR) or paclitaxel was accompanied by increased ARTN expression. Small interfering RNA (siRNA)-mediated depletion of ARTN in either IR- or paclitaxel-resistant ER-MC cells restored cell sensitivity to IR or paclitaxel. Expression of ARTN was enriched in ER-MC cells grown in mammospheric compared with monolayer culture and was also enriched along with BMI1, TWIST1, and DVL1 in mammospheric and ALDH1+ populations. ARTN promoted mammospheric growth and self-renewal of ER-MC cells and increased the ALDH1+ population, whereas siRNA-mediated depletion of ARTN diminished these CSC-like cell behaviors. Furthermore, increased ARTN expression was significantly correlated with ALDH1 expression in a cohort of ER-MC patients. Forced expression of ARTN also dramatically enhanced tumor initiating capacity of ER-MC cells in xenograft models at low inoculum. ARTN promotion of the CSC-like cell phenotype was mediated by TWIST1 regulation of BCL-2 expression. ARTN also enhanced mammosphere formation and the ALDH1+ population in estrogen receptor-positive mammary carcinoma (ER+MC) cells. Increased expression of ARTN and the functional consequences thereof may be one common adaptive mechanism used by mammary carcinoma cells to promote cell survival and renewal in hostile tumor microenvironments.
Subject(s)
Breast Neoplasms/pathology , Neoplastic Stem Cells/pathology , Nerve Tissue Proteins/metabolism , Nuclear Proteins/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Radiation Tolerance , Twist-Related Protein 1/metabolism , Aldehyde Dehydrogenase 1 Family , Animals , Breast Neoplasms/drug therapy , Breast Neoplasms/enzymology , Cell Line, Tumor , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/radiation effects , Female , Humans , Isoenzymes/metabolism , Mice , Mice, SCID , Neoplastic Stem Cells/drug effects , Neoplastic Stem Cells/radiation effects , Paclitaxel/pharmacology , Paclitaxel/therapeutic use , Radiation Tolerance/drug effects , Radiation Tolerance/radiation effects , Radiation, Ionizing , Receptors, Estrogen/metabolism , Retinal Dehydrogenase/metabolism , Xenograft Model Antitumor AssaysABSTRACT
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
Drug resistance is a major cause of chemotherapy failure in breast cancer patients with metastatic disease. We previously demonstrated that autocrine human growth hormone (hGH) plays a key role in oncogenic transformation and progression of mammary carcinoma. The present study investigated the role of autocrine hGH in the development of resistance to mitomycin C (MMC), an alkylating agent utilised in the treatment of advanced metastatic breast cancer. Stable forced expression of the hGH gene was established in the mammary carcinoma cell lines MDA-MB-231, MCF-7 and T47D. Autocrine hGH reduced the sensitivity of mammary carcinoma cells to MMC in cell viability assays and reduced MMC-induced apoptotic cell death when compared to a control cell line. In addition, autocrine hGH enhanced MDA-MB-231 clonogenic survival, anchorage independent cell growth, growth in 3D Matrigel and protected MDA-MB-231 cells from induction of DNA double-strand breaks following MMC treatment. Functional antagonism of hGH in the endometrial carcinoma cell line RL95-2, which endogenously expresses hGH, significantly increased the sensitivity of these cells to MMC-induced DNA damage and cell death. Thus, autocrine hGH promotes mammary and endometrial carcinoma cell resistance to MMC. These studies indicate a potential role for antagonism of autocrine hGH in chemoresistant breast cancer.
