MST1 and sarcoma: Since treatment with 5-azacytidine (AZA) did not significantly rescue expression of MST1 and MST2 in many sarcoma cell lines, it suggested that promoter hypermethylation was not the predominant transcriptional mechanism regulating expression of MST1 and MST2. Promoter hypermethylation is linked structurally to histone acetylation.