An investigation of Plk1 PBD inhibitor KBJK557 as a tumor growth suppressor in non-small cell lung cancer

Abstract

Lung cancer is the second most commonly reported type of cancer worldwide. Approximately 80–85% of lung cancer occurrences are accounted by non-small cell lung cancer (NSCLC). Polo-like kinase-1 (Plk1) plays multiple roles in cell cycle progression and its overexpression is observed in majority of malignancies, including NSCLC. A combination of frontline drugs and inhibitors targeting the Plk kinase domain (KD) has been used to overcome drug resistance in NSCLC. Plk1 KD inhibitors are highly prone to cross-reactivity with similar kinases, eventually leading to undesirable side effects. Moreover, there have been no reports of Plk1 PBD inhibitors showing antitumorigenic effects on NSCLC cells or animal models so far. To address this issue herein, for the first time, our recently reported Plk1 PBD inhibitor KBJK557 was evaluated for the anticancer potential against NSCLC cells. KBJK557 displayed notable cytotoxic effects in A549, PC9, and H1975 cells. Mechanistic investigations revealed that KBJK557-treated cells underwent G2/M cell cycle arrest, triggering subsequent apoptosis. In vivo antitumorigenic activity in xenograft mice model demonstrates that KBJK557-treated mice showed a considerable decrease in tumor size, proving the significances of Plk1 in lung cancer. Collectively, this study demonstrates that KBJK557 can serve as a promising drug candidate for treating the lung cancer through Plk1 PBD inhibition.