Heat Shock Factor-1 Is Required for Oncogenic H-RasG12V-induced Transformation in Human Bronchial Epithelial Cells

• Main Authors: Chih-Jou Su, 蘇致柔
• Other Authors: Jing-Yuan Chuang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/5c9h9q

碩士 === 中國醫藥大學 === 醫學檢驗生物技術學系碩士班 === 102 === Heat shock transcription factor-1 (HSF1) is a master regulator of heat shock response, which not only restores the normal protein folding environment but modulates cellular signaling pathways and metabolism to maintain cell survival under stresses. HSF1 is also activated by cancer-associated stresses and supports cellular transformation and cancer progression. In the present study, whether and how HSF1 may modulate oncogenic RasG12V-induced cell transformation in human bronchial epithelial cell line (BEAS2B) was investigated. The transcription activity of HSF1 before and after Ras transformation was measured using a HSPA1A promoter-luciferase reporter. Ectopic overexpression of the oncogenic RasG12V in BEAS2B cells significantly increased the transactivation activity of HSF1. The activity of HSF1 in BEAS2B cells stably overexpressing H-RasG12V (Ras-AIT2) was not due to the activation of Ras-related signaling pathway (MAPKs, PI3K/AKT, GSK3β), histone deacetylase (HDAC), or reactive oxidative stress (ROS). In addition, Ras-AIT2 cells treated with anti-cancer drugs (ATO, PES, TSA) were more resistant than the parental BEAS2B cells. Depletion of HSF1 by shRNA or inhibition of HSF1 by KRIBB11 in Ras-AIT2 cells reduced the cell proliferation rate and induced apoptosis. A marked increase in LC3-II (a component of autophagosomes) and SQSTM1/p62 (an autophagy-specific substrate) were induced after depletion of HSF1 for 72 h. Depletion of HSF1 in Ras-AIT2 cells disrupted lysosomal membrane permeability (LMP), indicating HSF1 was required for maintaining lysosome integrity. Attenuation of autophagy flux by chloroquine (CQ) significantly reduced HSF1 depletion-induced cell death. These results indicated that HSF1 may protect H-RasG12V-transformed cells by maintaining autophagy flux.