Jei Ha Lee, Jeong Yul Kim, Soo Im Choi, Eun Wie Cho and In Gyu Kim
Department of Radiation Biology, Environmental Radiation Research Group & Radiation Biotechnology and Applied Radioisotope Korea University of Science and Technology(UST), Korea Atomic Energy Research Institute, Daejeon, South Korea
Tescalcin(TESC), calcineurin-homologous protein 3, has been known to be expressed in several tissues and is involved in cell differentiation and cancer malignancy. In this study, we showed that forced TESC overexpression partly intensifies epithelial-to-mesenchymal transition(EMT) and cancer stem cell(CSC) properties and thus enhances gamma-radiation-resistance of lung cancer cells. We found that TESC and STAT3 were highly up-regulated in ALDH1high cells than ALDH1low cells sorted from A549 lung cancer cells. ALDH1 has been used as a successful and universal marker to isolate CSCs of many cancers. TESC directly interacts with SRC and thus affects EMT and stemness properties of cancer cell by regulation of ALDH1 expression via the activation of SRC/STAT3 signaling pathway. Chromatin immunoprecipitation assay clearly showed that proteins captured with STAT3 antibody in cell lysates interacted with the promoter region of ALDH1, indicating that STAT3 functions as a potential transcription activator of ALDH1 expression. We investigated sphere-forming ability and metastatic capacity upon inhibition of STAT using inhibitor or siRNA for inactivation of STAT3. Both inhibitor treatment and STAT3 suppression with siRNA in A549 cells partly suppressed ALDH1A1 and ALDH1A3 expression and thus significantly inhibited sphere-forming ability and metastatic capacity of cancer cells. FACS analysis using the ALDEFLUOR assay confirmed that treatment with STAT3 inhibitor down-regulates cellular level of ALDH1. These results suggest that TESC partly reinforces the self-renewal, metastatic and radiation resistance capacity of lung cancer cells through the SRC/STAT3/ALDH1 signaling pathway. [Korea Atomic Energy Research Institute, 57231-16]
Keywords: Tescalcin, stemness, cancer stem cell, ALDH1, STAT3.