Increased resistance of tumor cells to hyperthermia mediated by integrin-linked kinase

Purpose: Integrin-linked kinase (ILK) is a serine-threonine kinase associated with anchorage-independent growth and tumorigenic transformation. Previous studies indicate that overexpression of ILK is common among several types of tumors, and it is involved in the regulation of tumor cell survival under stress. In this study, we examined the effects of ILK expression on tumor cellular response to hyperthermia. Experimental Design: We used an adenovirus-mediated approach to overexpress the ILK gene in a prostate cancer cell line and examine its effects on heat stress-induced cell death. Clonogenic survival, as well as apoptosis, was evaluated in cells that overexpress ILK. In addition, the ability to form tumors in vivo was examined in syngeneic hosts. Finally, potential molecular mechanisms of ILK-mediated resistance to heat were examined by determining the status of a variety of signal transduction pathways. Results: ILK overexpression made tumor cells significantly more resistant to the cell-killing effects of hyperthermia. This was correlated at the molecular level with the down-regulation of hyperthermia-induced activation of stress-activated protein kinase/c-Jun-NH2-terminal kinase, p38 mitogen-activated protein kinase activities, and caspase 9. The overexpression of ILK was also shown to induce a more rapid tumor growth in a murine prostate cancer cell line Conclusion: ILK plays an important role in tumor growth and tumor response to hyperthermia treatment.