CRHR2/Ucn2 signaling is a novel regulator of miR‐7/YY1/Fas circuitry contributing to reversal of colorectal cancer cell resistance to Fas‐mediated apoptosis

• Published in: International journal of cancer 2018-01, Vol.142 (2), p.334-346
• Main Authors: Pothoulakis, Charalabos, Torre‐Rojas, Monica, Duran‐Padilla, Marco A., Gevorkian, Jonathan, Zoras, Odysseas, Chrysos, Emmanuel, Chalkiadakis, George, Baritaki, Stavroula
• Format: Article
• Language: English
• Subjects: Apoptosis; Cancer; Cell Proliferation; Colorectal cancer; Colorectal carcinoma; Colorectal Neoplasms - genetics; Colorectal Neoplasms - metabolism; Colorectal Neoplasms - pathology; Corticotropin-releasing hormone; Corticotropin-Releasing Hormone - genetics; Corticotropin-Releasing Hormone - metabolism; CRHR2; Cytotoxicity; Epithelial-Mesenchymal Transition; Fas; fas Receptor - genetics; fas Receptor - metabolism; FasL protein; Gene Expression Regulation, Neoplastic; Humans; Medical research; Mesenchyme; Metastases; Metastasis; MicroRNAs - genetics; microRNA‐7; Receptors, Corticotropin-Releasing Hormone - genetics; Receptors, Corticotropin-Releasing Hormone - metabolism; Sensitivity; Signal Transduction; Tissues; Transcription; Tumor Cells, Cultured; Urocortin; Urocortins - genetics; Urocortins - metabolism; YY1; YY1 Transcription Factor - genetics; YY1 Transcription Factor - metabolism
• ISSN: 0020-7136; 1097-0215; 1097-0215
• DOI: 10.1002/ijc.31064

Colorectal cancer (CRC) responds poorly to immuno‐mediated cytotoxicity. Underexpression of corticotropin‐releasing‐hormone‐receptor‐2 (CRHR2) in CRC, promotes tumor survival, growth and Epithelial to Mesenchymal Transition (EMT), in vitro and in vivo. We explored the role of CRHR2 downregulation in CRC cell resistance to Fas/FasL‐mediated apoptosis and the underlying molecular mechanism. CRC cell sensitivity to CH11‐induced apoptosis was compared between Urocortin‐2 (Ucn2)‐stimulated parental and CRHR2‐overexpressing CRC cell lines and targets of CRHR2/Ucn2 signaling were identified through in vitro and ex vivo analyses. Induced CRHR2/Ucn2 signaling in SW620 and DLD1 cells increased specifically their sensitivity to CH11‐mediated apoptosis, via Fas mRNA and protein upregulation. CRC compared to control tissues had reduced Fas expression that was associated with lost CRHR2 mRNA, poor tumor differentiation and high risk for distant metastasis. YY1 silencing increased Fas promoter activity in SW620 and re‐sensitized them to CH11‐apoptosis, thus suggesting YY1 as a putative transcriptional repressor of Fas in CRC. An inverse correlation between Fas and YY1 expression was confirmed in CRC tissue arrays, while elevated YY1 mRNA was clinically relevant with advanced CRC grade and higher risk for distant metastasis. CRHR2/Ucn2 signaling downregulated specifically YY1 expression through miR‐7 elevation, while miR‐7 modulation in miR‐7high SW620‐CRHR2+ and miR‐7low HCT116 cells, had opposite effects on YY1 and Fas expressions and cell sensitivity to CH11‐killing. CRHR2/Ucn2 signaling is a negative regulator of CRC cell resistance to Fas/FasL‐apoptosis via targeting the miR‐7/YY1/Fas circuitry. CRHR2 restoration might prove effective in managing CRC response to immune‐mediated apoptotic stimuli. What's new? Colorectal cancer (CRC) is highly resistant to immune‐mediated cytotoxicity, in large part due to its ability to escape Fas/FasL‐mediated apoptosis. This study uncovers a novel role of the regulatory receptor for stress, CRHR2, in reversing CRC resistance to extrinsic apoptotic stimuli. Thus, here the authors show that CRHR2/Ucn2 signaling specifically resensitizes CRC cells to Fas/FasL‐induced apoptosis through upregulation of Fas receptor. They further delineate the underlying molecular mechanism, showing the involvement of the miR‐7/YY1/Fas circuitry. The findings suggest that CRHR2 expression and activation levels might be of prognostic and therapeutic releva