TRAP1 is Involved in Cell Cycle Regulated by Retinoblastoma Susceptibility Gene (RB1) in Early Hypoxia and has Variable Expression Patterns in Human Tumors
Pages 186-193
Jiangting Hu, Ern Yu Tan, Leticia Campo, Russell Leek, Zainina Seman, Helen Turley, Domenico Delia, Alfredo Cesario, Kevin Gatter and Francesco Pezzella

DOI: http://dx.doi.org/10.6000/1929-2279.2013.02.03.5

Published: 1 July 2013 

Abstract: Tumor necrosis factor receptor associated protein 1(TRAP1) is a member of the Hsp90 family that acts as a molecular chaperon to the tumor suppressor retinoblastoma susceptibility gene (RB1). We have previously demonstrated that TRAP1-positive cells contain a high level of cell proliferating genes, whilst TRAP1-negative cells contain a high level of genes involved in cell cycles and metastases. In this study, we performed a functional analysis of TRAP1 which focused on its regulation within a cell cycle in relation to RB1. Following a heat shock, TRAP1 translocates to the nucleus and chaperonsRB1. When TRAP1 is silenced by siRNA, or prevented from entering the nucleus in hypoxic cells, formation of RB1/E2F1 complexes is impaired and cell cycle activity is promoted by deregulating the G1/S transition. Inhibition of the nuclear translocation of TRAP1 with geldanamycin abrogates its ability to maintain RB1 in a form that associates with E2F1. Restoration of TRAP1 expression reverses these effects. We analysed TRAP1/RB1 expression on 630 tumors by immunohistochemical staining and found TRAP1 lost in some types of cancer, such as non-small cell lung cancer and breast cancer, and the positive correlation of TRAP1 expression in nuclear and cytoplasm with RB1 was observed. Clinico-pathological data showed that breast carcinoma patients lacking nuclear TRAP1 have a shorter disease free survival. Our data suggests that nuclear translocation of TRAP1 is crucial for its function as a chaperon. The loss of TRAP1 expression in certain types of cancer may provide the growth advantage due to the lost control at cell cycle check point.