Mesothelioma cells escape heat stress by upregulating Hsp40/Hsp70 expression via mitogen-activated protein kinases

Therapy with hyperthermal chemotherapy in pleural diffuse malignant mesothelioma had limited benefits for patients. Here we investigated the effect of heat stress on heat shock proteins (HSP), which rescue tumour cells from apoptosis. In human mesothelioma and mesothelial cells heat stress (39-42 degrees C) induced the phosphorylation of two mitogen activated kinases (MAPK) Erk1/2 and p38, and increased Hsp40, and Hsp70 expression. Mesothelioma cells expressed more Hsp40 and were less sensitive to heat stress compared to mesothelial cells. Inhibition of Erk1/2 MAPK by PD98059 or by Erk1 siRNA down-regulated heat stress-induced Hsp40 and Hsp70 expression and reduced mesothelioma cell survival. Inhibition of p38MAPK by SB203580 or siRNA reduced Hsp40, but not Hsp70, expression and also increased mesothelioma cell death. Thus hyperthermia combined with suppression of p38 MAPK or Hsp40 may represent a novel approach to improve mesothelioma therapy.