Pan-CDK inhibition augments cisplatin lethality in nasopharyngeal carcinoma cell lines and xenograft models

In addition to their canonical roles in regulating cell cycle transition and transcription,cyclin-dependent kinases(CDKs)have been shown to coordinate DNA damage response pathways,suggesting a rational pairing of CDK inhibitors with genotoxic chemotherapeutic agents in the treatment of human malignancies.Here,we report that roniciclib(BAY1000394),a potent pan-CDK inhibitor,displays promising anti-neoplastic activity as a single agent and potentiates cisplatin lethality in preclinical nasopharyngeal carcinoma(NPC)models.Proliferation of the NPC cell lines HONE-1,CNE-2,C666-1,and HK-1 was effectively curbed by roniciclib treatment,with IC_(50)values between 11 and 38 nmol/L.These anticancer effects were mediated by pleiotropic mechanisms consistent with successful blockade of cell cycle CDKs 1,2,3,and 4 and transcriptional CDKs 7 and 9,ultimately resulting in arrest at G1/S and G2/M,downregulation of the transcriptional apparatus,and repression of anti-apoptotic proteins.Considerably enhanced tumor cell apoptosis was achieved following combined treatment with 10 nmol/L roniciclib and 2.0μmol/L cisplatin;this combination therapy achieved a response over 250%greater than either drug alone.Although roniciclib chemosensitized NPC cells to cisplatin,it did not sensitize untransformed(NP69)cells.The administration of 0.5 mg/kg roniciclib to BALB/c xenograft mice was well tolerated and effectively restrained tumor growth comparable to treatment with 6 mg/kg cisplatin,whereas combining these two agents produced far greater tumor suppression than either of the monotherapies.In summary,these data demonstrate that roniciclib has strong anti-NPC activity and synergizes with cisplatin chemotherapy at clinically relevant doses,thus justifying further evaluation of this combinatorial approach in clinical settings.