ABSTRACT
The synthetic steroid mifepristone blocks the growth of ovarian cancer cells, yet the mechanism driving such effect is not entirely understood. Unbiased genomic and proteomic screenings using ovarian cancer cell lines of different genetic backgrounds and sensitivities to platinum led to the identification of two key genes upregulated by mifepristone and involved in the unfolded protein response (UPR): the master chaperone of the endoplasmic reticulum (ER), glucose regulated protein (GRP) of 78 kDa, and the CCAAT/enhancer binding protein homologous transcription factor (CHOP). GRP78 and CHOP were upregulated by mifepristone in ovarian cancer cells regardless of p53 status and platinum sensitivity. Further studies revealed that the three UPR-associated pathways, PERK, IRE1α, and ATF6, were activated by mifepristone. Also, the synthetic steroid acutely increased mRNA translation rate, which, if prevented, abrogated the splicing of XBP1 mRNA, a non-translatable readout of IRE1α activation. Moreover, mifepristone increased LC3-II levels due to increased autophagic flux. When the autophagic-lysosomal pathway was inhibited with chloroquine, mifepristone was lethal to the cells. Lastly, doses of proteasome inhibitors that are inadequate to block the activity of the proteasomes, caused cell death when combined with mifepristone; this phenotype was accompanied by accumulation of poly-ubiquitinated proteins denoting proteasome inhibition. The stimulation by mifepristone of ER stress and autophagic flux offers a therapeutic opportunity for utilizing this compound to sensitize ovarian cancer cells to proteasome or lysosome inhibitors.
Subject(s)
Autophagy/drug effects , Lysosomes/metabolism , Mifepristone/pharmacology , Ovarian Neoplasms/genetics , Ovarian Neoplasms/pathology , Proteasome Inhibitors/pharmacology , Protein Biosynthesis/drug effects , Unfolded Protein Response/drug effects , Activating Transcription Factor 4/metabolism , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Chloroquine/pharmacology , Cinnamates/pharmacology , Endoplasmic Reticulum Chaperone BiP , Eukaryotic Initiation Factor-2/metabolism , Female , Gene Expression Profiling , Gene Expression Regulation, Neoplastic/drug effects , Humans , Lysosomes/drug effects , Platinum/pharmacology , Protein Biosynthesis/genetics , Puromycin/pharmacology , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction/drug effects , Thiourea/analogs & derivatives , Thiourea/pharmacology , Tunicamycin/pharmacologyABSTRACT
This study tested the hypothesis that reciprocal communication occurs between macrophages and cultured human endometrial stromal cells and that this communication may contribute to the pathology of endometriosis. An endometrial stromal cell line (telomerase-immortalized human endometrial stromal cell [T-HESC]) was treated with macrophage-conditioned medium (CM) +/- estradiol + progesterone. Macrophages were treated without or with T-HESC CM. DNA microarray identified 716 differentially expressed genes in T-HESCs in response to factors secreted by macrophages. Upregulated genes in T-HESC included interleukin 8 (IL-8)/chemokine (C-X-C motif) ligand 8 (CXCL8), matrix metalloproteinase 3 (MMP3), phospholamban, cysteine-rich angiogenic inducer 61 (CYR61), connective tissue growth factor (CTGF), tenascin C, and nicotinamide N-methyltransferase (NNMT), whereas integrin alpha-6 was downregulated. In contrast, 15 named genes were differentially expressed in macrophages in response to factors secreted by endometrial stromal cells. The data document reciprocal communication between macrophages and endometrial stromal cells and suggest that interaction with macrophages stimulates the expression of genes in endometrial stromal cells that may support the establishment of endometriosis.