Transcriptional inhibition by CDK7/9 inhibitor SNS-032 suppresses tumor growth and metastasis in esophageal squamous cell carcinoma.

Metastasis is one of most lethal causes that confer a poor prognosis of patients with esophageal squamous cell carcinoma (ESCC), whereas there is no available target drug for metastatic ESCC currently. In this study, we aimed to determine whether the transcriptional inhibition by CDK7/9 inhibitor SNS-032 is activity against ESCC. MTT and soft agar assays were performed to examine the influence of SNS-032 on ESCC growth in vitro. Tumor xenograft in nude mice was used to assess the antitumor activity of SNS-032 in vivo. The roles of SNS-032 in ESCC metastasis were conducted by wound healing and transwell assays in vitro, and by a lung and a popliteal lymph node metastasis model in vivo. The results showed that CDK7 and CDK9 were highly expressed in ESCC cells; SNS-032 effectively inhibited cellular viability, abrogated anchorage-independent growth, and potentiated the sensitivity to cisplatin in ESCC cells in vitro and in vivo. In addition, SNS-032 induced a mitochondrial-dependent apoptosis of ESCC cells by reducing Mcl-1 transcription. SNS-032 also potently abrogated the abilities of ESCC cell migration and invasion through transcriptional downregulation of MMP-1. Importantly, SNS-032 remarkably inhibited the growth of ESCC xenograft, increased the overall survival, as well as diminished the lung and lymph node metastasis in nude mice. Taken together, our findings highlight that the CDK7/9 inhibitor SNS-032 is a promising therapeutic agent, and warrants a clinical trial for its efficacy in ESCC patients, even those with metastasis.