Autophagy is a cellular catabolic process by which long-lived
proteins and damaged organelles are degradated by lysosomes. Activation of autophagy is an important survival mechanism that protects
cancer cells from various stresses, including
anticancer agents. Recent studies indicate that
pyrvinium pamoate, an FDA-approved antihelminthic
drug, exhibits wide-ranging anticancer activity. Here we demonstrate that
pyrvinium inhibits autophagy both in vitro and in vivo. We further demonstrate that the inhibition of autophagy is
mammalian target of rapamycin independent but depends on the transcriptional inhibition of autophagy genes. Moreover, the combination of
pyrvinium with autophagy stimuli improves its toxicity against
cancer cells, and pretreatment of cells with 3-MA or siBeclin1 partially protects cells from
pyrvinium-induced cell death under
glucose starvation, suggesting that targeted autophagy addiction is involved in
pyrvinium-mediated cytotoxicity. Finally, in vivo studies show that the combination
therapy of
pyrvinium with the anticancer and autophagy stimulus agent,
2-deoxy-D-glucose (2-DG), is significantly more effective in inhibiting
tumor growth than
pyrvinium or 2-DG alone. This study supports a novel
cancer therapeutic strategy based on targeting autophagy addiction and implicates using
pyrvinium as an autophagy inhibitor in combination with chemotherapeutic agents to improve their therapeutic efficacy.