Quercetin has been reported to possess therapeutic effects in the treatment of cancers. In this study, the molecular action of quercetin, with emphasis on its ability to control the intracellular signaling cascades of hypoxia inducible factor-$1{alpha}$ (HIF-$1{alpha}$), mammalian target of rapamycin (mTOR), and AMP-activated protein kinase (AMPK), responsible for survival or induction of apoptosis in hypoxic MCF-7 cells, was investigated. The effects of quercetin on apoptosis in relation to its ability to prevent HIF-$1{alpha}$ induction were investigated. The involvement of HIF-$1{alpha}$ reduction in quercetin-based cancer control was clearly shown in conditions of mTOR inhibition by rapamycin, an mTOR inhibitor. Surprisingly, quercetin induced an AMPK-suppressed state in a $CoCl_2$-induced hypoxic condition. It is speculated that quercetin is capable of inhibiting AMPK to decrease HIF-$1{alpha}$, which is a critical survival factor in hypoxia. A complex control of HIF-$1{alpha}$, mTOR, and AMPK is necessary in inducing apoptosis of MCF-7 breast cancer cells under hypoxia.