Rigosertib is a more effective radiosensitizer than cisplatin in concurrent chemoradiation treatment of cervical carcinoma, in vitro and in vivo.

Abstract PURPOSE: To compare rigosertib versus cisplatin as an effective radiosensitizing agent for cervical malignancies. METHODS AND MATERIALS: Rigosertib and cisplatin were tested in cervical cancer cell lines, HeLa and C33A. A 24-hour incubation with rigosertib and cisplatin, before irradiation (2-8 Gy), was used for clonogenic survival assays. Cell cycle analysis (propidium iodide staining) and DNA damage (γ-H2AX expression) were evaluated by fluorescence-activated cell sorter cytometry. Rigosertib was also tested in vivo in tumor growth experiments on cervical cancer xenografts. RESULTS: Rigosertib was demonstrated to induce a G2/M block in cancer cells. Survival curve comparison revealed a dose modification factor, as index of radiosensitization effect, of 1.1-1.3 for cisplatin and 1.4-2.2 for rigosertib. With 6-Gy irradiation, an increase in DNA damage of 15%-25% was achieved in both HeLa and C33A cells with cisplatin pretreatment, and a 71-108% increase with rigosertib pretreatment. In vivo tumor growth studies demonstrated higher performance of rigosertib when compared with cisplatin, with 53% longer tumor growth delay. CONCLUSIONS: Rigosertib was more effective than cisplatin when combined with radiation and caused minimal toxicity. These data support the need for clinical trials with rigosertib in combination therapy for patients with cervical carcinoma.