Esophageal carcinoma is aggressive in nature and its prognosis is largely dependent on the degree of invasion. Histone deacetylase 6 (HDAC6), as the most unique member of HDACs family, has the positive activity to promote initiation and progression of various cancers via targeting multiple non‐histone proteins in cytoplasm. In this study, we found that HDAC6 was over‐expressed in three esophageal cancer cell lines (KYSE140, KYSE170, KYSE180) when compared to non‐carcinoma esophageal epithelial cell HEEC‐1. Then two HDAC6 specific siRNAs and HDAC6 inhibitor tubastatin A greatly suppressed KYSE140 and KYSE180 cells proliferation and migration, and the inhibition of cell motility was accompanied by elevated acetylation of α‐tubulin, a target of HDAC6. Consistently, the microtubulin skeleton was stabilized after HDAC6 knockdown or inhibition. In addition, acetylation status of HSP90, another HDAC6 target, was also increased towards HDAC6 knockdown or inhibition by co‐immunoprecipitation assay. Besides, co‐treatment of HSP90 inhibitor (PU‐H71) and HDAC6 inhibitor (tubastatin A) induced a stronger cell migration inhibition compared to administration of either drug alone. Furthermore, cell proliferation of KYSE140 and KYSE180 were also compromised in response to combination of HDAC6 and HSP90 inhibitors. Additionally, co‐administration of HSP90 inhibitor and HDAC6 inhibitor strongly inhibited tumor growth in vivo. Taken together, our results indicated that HDAC6 is a promising target by inhibiting HSP90 function in ESCC.

This study presented the analysis of free-breathing lung tumor motion characteristics using GE 4DCT and Varian RPM systems. Tumor respiratory movement was found to be associated with GTV size, the superior-inferior tumor location in the lung, and the attachment degree to rigid structure (e.g., chest wall, vertebrae, or mediastinum), with tumor location being the most important factor among the other two. Improved outcomes in survival and local control of 43 lung cancer patients were also reported. Consideration of respiration-induced motion based on 4DCT for lung cancer yields individualized margin and more accurate and safe target coverage and thus can potentially improve treatment outcome.