STANDARD_NAME KOBAYASHI_RESPONSE_TO_ROMIDEPSIN SYSTEMATIC_NAME M3021 COLLECTION C2:CGP MSIGDB_URL https://www.gsea-msigdb.org/gsea/msigdb/human/geneset/KOBAYASHI_RESPONSE_TO_ROMIDEPSIN NAMESPACE HUMAN_SEQ_ACCESSION DESCRIPTION_BRIEF Genes up-regulated in MM-LH cells (malignant melanoma) after treatment with the HDAC inhibitor romidepsin (FK228) [PubChem=5352062]. DESCRIPTION_FULL Histone deacetylase (HDAC) inhibitors are expected to be effective for refractory cancer because their mechanism of action differs from that of conventional antineoplastic agents. In this study, we examined the effect of the HDAC inhibitor FK228 on malignant melanoma, as well as its molecular mechanisms. FK228 was highly effective against melanoma compared with other commonly used drugs. By comparing the gene expression profiles of melanoma cells and normal melanocytes, we defined a subset of genes specifically upregulated in melanoma cells by FK228, which included Rap1, a small GTP-binding protein of the Ras family. The expression of Rap1 mRNA and protein increased in FK228-treated melanoma cells in both a dose- and a time-dependent manner. A decrease in the phosphorylation of c-Raf, MEK1/2, and ERK1/2 was accompanied by an increase in Rap1 expression in both FK228-treated and Rap1-overexpressing cells. Inhibition of Rap1 upregulation by small interfering RNA (siRNA) abrogated the induction of apoptosis and suppression of ERK1/2 phosphorylation in FK228-treated melanoma cells. These results indicate that the cytotoxic effects of FK228 are mediated via the upregulation of Rap1. Furthermore, we found that Rap1 was overexpressed and formed a complex with B-Raf in melanoma cell lines with a V599E mutation of B-Raf. The siRNA-mediated abrogation of Rap1 overexpression increased the viability of these cells, suggesting that Rap1 is also an endogenous regulator of Ras-MAP kinase signaling in melanomas. PMID 16186804 GEOID AUTHORS Kobayashi Y,Ohtsuki M,Murakami T,Kobayashi T,Sutheesophon K,Kitayama H,Kano Y,Kusano E,Nakagawa H,Furukawa Y CONTRIBUTOR Arthur Liberzon CONTRIBUTOR_ORG MSigDB Team EXACT_SOURCE Table 1 FILTERED_BY_SIMILARITY EXTERNAL_NAMES_FOR_SIMILAR_TERMS EXTERNAL_DETAILS_URL SOURCE_MEMBERS AB020677,AK026681,AK056390,BC034049,D38522,D80010,M76766,NM_000247,NM_000584,NM_001445,NM_001661,NM_002507,NM_004093,NM_005252,NM_006928,NM_007115,NM_014781,NM_022456,NM_022726 GENE_SYMBOLS DENND3,MERTK,KLHL7,DNAJC27,SYT11,LPIN1,GTF2B,MICA,CXCL8,FABP6,ARL4D,NGFR,EFNB2,FOS,PMEL,TNFAIP6,RB1CC1,RAB3IP,ELOVL4 FOUNDER_NAMES