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[摘要]：The p53 tumor suppressor is negatively regulated by murine double minute 2 (MDM2), which binds to p53 and promotes p53 ubiquitination and degradation. MDM2 inhibitor-219 (MI-219), a small molecule MDM2 inhibitor, was recently reported to disrupt p53-MDM2 binding, leading to p53 activation and suppression of tumor cell growth both in vitro and in vivo. This study tested the efficacy of MI-219 against a panel of lung cancer cell lines alone or in combination with MDM2 knockdown, an X-linked inhibitor of apoptosis protein (XIAP) inhibitor, or a chemotherapeutic drug, etoposide. When acting alone, MI-219 selectively inhibited growth of wild-type (wt) p53-containing lung cancer cells by induction of G(1) or G(2) arrest in a p53-dependent manner, but had a minor effect on wt p53-bearing immortalized cells. MDM2 knockdown had a minimal effect on MI-219 induced growth suppression. Although MI-219 increased XIAP expression, blockage of XIAP via SM-164, a Smac mimetic compound, did not selectively enhance MI-219 cytotoxicity. Significantly, MI-219 sensitized lung cancer cells to etoposide-induced cell killing. This study revealed that, when acting alone, MI-219 selectively inhibits the growth of lung cancer cells harboring a wt p53. In combination, MI-219-induced cytotoxicity was not affected by MDM2 knockdown nor by a XIAP inhibitor, but MI-219 sensitized cancer cells to etoposide, suggesting MI-219 could serve as a chemosensitizing agent. |
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