The histone deacetylase inhibitor LBH589 inhibits undifferentiated pleomorphic sarcoma growth via downregulation of FOS-like antigen 1.

Undifferentiated pleomorphic sarcoma (UPS) is the second most frequent soft tissue sarcoma. Because of its resistance to chemotherapy, UPS patients are treated with surgical resection and complementary radiotherapy. However, since standard chemotherapy has not been established, unresectable or metastatic cases result in a poor prognosis. Therefore, the identification of a more effective therapy for UPS patients is needed. The development and progression of malignant tumors involve epigenetic alterations, and histone deacetylases (HDAC) have become a promising chemotherapeutic target. In this study, we investigated the potential effects and mechanisms of an HDAC inhibitor, LBH589, in UPS cells. We confirmed that LBH589 exhibits potent antitumor activities in four human UPS cell lines (GBS-1, TNMY-1, Nara-F, and Nara-H) and IC50 values ranged from 7 to 13 nM. A mouse xenograft model showed that LBH589 treatment effectively suppressed tumor growth. FACS analysis showed that LBH589 induced apoptosis and G2/M cell cycle arrest. Among apoptosis-related proteins, the expressions of Bcl-2 and Bcl-xL were decreased and the expression of Bak and Bim increased. Among cell cycle-related proteins, reductions of CDK1, p-CDK1, cyclin B1, Aurora A, and Aurora B were observed after LBH589 treatment. RNA microarray identified the FOS-like antigen 1 (FOSL1) gene as a downregulated gene in response to LBH589 in UPS cells. While knockdown of FOSL1 decreased UPS cell proliferation, overexpression induced cell proliferation. Our results show that LBH589 could be a promising chemotherapeutic agent in the treatment of UPS and downregulation of the FOSL1 gene could be the new molecular target of UPS treatment.