Over-expression of the small heat-shock protein, hsp25, inhibits growth of Ehrlich ascites tumor cells

hsp25 is a small, growth-related, mammalian stress protein which is highly accummulated in the stationary phase or Ehrlich ascites tumor in vivo. Ehrlich ascites cells cultivated in vitro under conditions of continuous exponential growth express hsp25 only at a low level. These cells were stably transfected with an eukaryotic expression vector carrying the coding sequence of the small heat-shock protein, hsp25, under control of the murine metallothionein promoter. The resulting cell lines (EAT 116 and EAT 118) exhibit constitutive over-expression of the small heat-shock protein. hsp25, which can be further increased by induction with cadmium. Both cell lines show increased thermoresistance. The in vitro proliferation rate of the transfected cell lines EAT 116 and EAT 118 is significantly decreased depending on the degree of cadmium-regulated over-expression of hsp25. Furthermore, a significant delay in Ehrlich ascites tumor growth in mice using the hsp25 over-expressing cells for primary inoculation could be demonstrated.