Targeting MCL-1 sensitizes human esophageal squamous cell carcinoma cells to cisplatin-induced apoptosis

Background: Esophageal squamous cell carcinoma (ESCC) is one of the most lethal malignancies in China and is an exceptionally drug-resistant tumor with a 5-year survival rate less than 15%. Cisplatin is the most commonly used conventional chemotherapeutic drug for the treatment of ESCC, but some patients have a poor response to cisplatin-based chemotherapy. New strategies that could enhance chemosensitivity to cisplatin are needed. Methods: We used reverse transcription-RCR (RT-PCR), immunoblot, immunohistochemical (IHC) staining, anchorage-dependent and -independent growth assays, co-immunoprecipitation (Co-IP) assay, RNA interference and in vivo tumor growth assay to study the expression of MCL-1 in ESCCs and the response of ESCC cells to cisplatin. Results: The present study showed that MCL-1 expression was significantly increased in ESCC tissues compared to normal adjacent tissues and was associated with depth of invasion and lymph node metastasis. Knockdown of MCL-1 produced significant chemosensitization to cisplatin in association with caspase-3 activation and PARP cleavage in KYSE150 and KYSE510 cells. The selective MCL-1 inhibitor UMI-77 caused dissociation of MCL-1 from the proapoptotic protein BAX and BAK, and enhanced KYSE150 and KYSE510 cells to cisplatin-induced apoptosis accompanied by caspase-3 activation and PARP cleavage. Conclusions: The current study suggests that MCL-1 contributes to the development of ESCC and is a promising therapeutic target for chemosensitization of ESCC cells to cisplatin. This might provide a scientific basis for developing effective approaches to treat the subset of ESCCs patients with MCL-1 overexpression.