This study was undertaken to interrogate cancer cell survival during long-term hypoxic stress. Two systems with relevance to carcinogenesis were employed: Fully transformed BJ cells and a renal carcinoma cell line (786-0). The dynamic of AMPK activity was consistent with a prosurvival role during chronic hypoxia. This was further supported by the effects of AMPK agonists and antagonists (AICAR and compound C). Expression of a dominant-negative AMPK alpha resulted in a decreased ATP level and significantly compromised survival in hypoxia. Dose-dependent prosurvival effects of rapamycin were consistent with mTOR inhibition being a critical downstream mediator of AMPK in persistent low oxygen. (C) 2008 Elsevier Inc. All rights reserved.