HYPOXIA INDUCES HSP-70 GENE-EXPRESSION IN HUMAN HEPATOMA (HEP-G2) CELLS

Populations of cells within solid tumours are exposed to low oxygen co ncentrations. The mechanism by which tumour cells tolerate such hypoxi a is unknown but it may parallel responses to other types of cellular stress. We investigated the effect of oxygen on steady state levels of inducible heat shock protein 70 mRNA in cultured human hepatoma cells . Northern blot analysis demonstrated that hypoxia increased HSP 70 mR NA levels within 3 hours, with a transient 12-fold increase at 6 hours compared with normoxia. We also showed that heat shock induced a 20-f old increase in HSP 70 mRNA. This data suggests that HSPs may be impor tant in tumour progression by protecting cells from hypoxic stress.