Hsp27 and Hsp70 may contribute with the DNA repair function of hMLH1 and hMSH2 in peripheral blood lymphocytes from normal subjects and cancer patients.

SILVINA BEATRIZ NADIN, LAURA M. VARGAS-ROIG, GISELA DRAGO, JORGE IBARRA,AND DANIEL R. CIOCCA.

Concepción, Chile

Workshop; 5th Internacional Workshop on the Molecular Biology of Stress Responses; 2006

Cell Stress Society International

Mismatch repair (MMR) deficiency and heat shock proteins (Hsps) expression have been implicated in drug resistance to platinum compounds (cisplatin) and to topoisomerase II poisons (doxorubicin). This study was designed to examine the interactions between Hsp27 and Hsp70 with hMLH1 and hMSH2 MMR proteins and the DNA damage status (evaluated by comet assay) in peripheral blood lymphocytes (PBL) treated with doxorubicin or cisplatin and to investigate whether these proteins and the comet assay correlate with the survival of cancer patients. PBL from 10 healthy donors and 25 cancer patients (before and after three cycles of chemotherapy) were exposed to in vitro treatments: C (control), HS (heat shock at 42ºC), Do/Pt (doxorubicin/cisplatin alone), and HS+Do/HS+Pt (heat shock + doxorubicin/cisplatin). PBL were collected at time 0 (T0: immediately after drug treatment) and after 24 hours of repair (T24). Hsp27, Hsp70, hMLH1 and hMSH2 were studied by immunocytochemistry and the DNA damage by alkaline comet assay. Immunofluorescence studies and confocal microscopy revealed that hMLH1 and hMSH2 colocalized with Hsp27 and Hsp72 (inducible form of Hsp70), which constitutes the first evidence of the interaction Hsps-MMR proteins. hMLH1 and hMSH2 were significantly induced by Pt and HS+Pt at T24 in cancer patients, but only discreet influenced by Do. Cancer patients presented higher basal expression of total and nuclear Hsp27 and Hsp70 than controls, and these proteins were also increased by HS, Do and HS+Do. The Hsp70 induction by Pt and HS+Pt was noted in patients, specially nuclear Hsp70. In cancer patients, basal DNA damage was lightly higher than in healthy persons; and after Pt and HS+Pt treatments, DNA migration and number of apoptotic cells were higher than controls. Hsps accomplished a cytoprotective function in pre-chemotherapy PBL (HS before Do or Pt), but not in post-chemotherapy samples. The results suggest that Hsps could associate with MMR proteins to assist the DNA repair function and point to the utility of these molecules and of the comet assay as predictive markers.