Sorafenib potentiates ABT-737-induced apoptosis in human oral cancer cells

• Sorafenib synergistically kills oral cancer cells when combined with ABT-737.
• Combination treatment induces the expression of Bax and Bak and their activation.
• Inactivation of ERK and STAT3 may be associated with the synergy of combination treatment.

ObjectiveThe mimetic BH3 ABT-737, a potent inhibitor of anti-apoptotic Bcl-2 family proteins, has potential as anti-cancer drug in many cancers. Recently, patients treated with ABT-737 have developed drug tolerance during cancer therapy. Therefore, we examined whether ABT-737 is effective in killing MC-3 and HSC-3 human oral cancer cells either alone or in combination with the oncogenic kinase inhibitor, sorafenib.DesignThe potentiating activities of sorafenib in ABT-737-induced apoptosis were determined using trypan blue exclusion assay, DAPI staining, cell viability assay and Western blot analysis.ResultsCombined use of ABT-737 and sorafenib synergistically suppressed cell viability and induced apoptosis compared with either compound individually. The combination of ABT-737 and sorafenib altered only Bax and Bak proteins and their activations, resulting in mitochondrial translocation of Bax from the cytosol. Additionally, combination treatment-mediated apoptosis may be correlated with ERK and STAT3 pathways.ConclusionsThese results suggest that sorafenib may effectively overcome ABT-737 resistance to apoptotic cell death, which can be a new potential chemotherapeutic strategy against human oral cancer.