Epigenetic regulatory mechanisms of histone acetylation in the treatment of cutaneous squamous cell carcinoma.

Cutaneous squamous cell carcinoma (cSCC) is the second most common malignancy; as such, novel systemic therapies are important for the treatment of locally advanced or metastatic disease. Histone deacetylase (HDAC) inhibitors have been increasingly studied in recent years as epigenome-targeted therapy for cSCC. HDACs inhibitors reduce tumorigenesis by blocking HDAC activity and creating a more relaxed chromatin structure, thus inducing gene expression by inhibiting deacetylation of transcription factors. In vitro experiments and in vivo mice studies have shown that HDAC inhibition halts cSCC pathogenesis. Ginsenoside 20(R)-Rg3 has been successfully employed to inhibit HDAC3 and thereby inhibit cSCC epithelial mesenchymal transition. Similarly, vorinostat has been found to blunt growth of human xenograft epidermoid cSCCs in highly immunosuppressed mice. Additionally, trichostatin A induces irreversible growth arrest in SCC cells, and MS-275 significantly reduces cSCC tumor burden in mice. These recent studies indicate that HDAC inhibitors represent a promising emerging therapy for cSCC.