Modification of growth and tumorigenicity in epidermal cell lines by DNA-mediated gene transfer of M(r) 27,000 heat shock protein (hsp27).

In the present communication, the role of the M(r) 27,000 human small heat shock protein (hsp27) in tumorigenicity was examined. Stable transfectants of a melanoma cell line (A375) and an epidermal squamous carcinoma cell line (A431), isolated by cotransfection of a hsp27 expression vector (pSG-2711) and a neomycin-resistant plasmid, were obtained. Clones expressing high levels of hsp27 were analyzed using immunohistochemistry and immunoblotting. Cells transfected with only the plasmid for neomycin were used as control cells. Growth analysis of transfectants in A375 and A431 tumor cells showed in vitro a lower proliferation rate than control clones derived from both lines. To investigate the correlation of hsp27 expression and tumorigenicity, transfectants of each cell type and control cells were injected into nude mice. A delay in tumor development was detected in animals inoculated with cells overexpressing hsp27. However, after this initial delay, tumors appeared in some of these animals and no difference could be observed in their growth dynamics compared to control tumors. When tumors transfected with the hsp27 construct were analyzed using immunohistochemistry and PCR, no evidence for hsp27 expression was obtained which implicates instability of the transduced foreign DNA when maintained under nonselective conditions. The present study shows that genetic manipulation of tumor cells may provide valuable information on the role of hsp27 in tumor growth.