MITF-independent pro-survival role of BRG1-containing SWI/SNF complex in melanoma cells.
Metastasized malignant melanoma has a poor prognosis because of its intrinsic resistance to chemotherapy and radiotherapy. The central role in the melanoma transcriptional network has the transcription factor MITF (microphthalmia-associated transcription factor). It has been shown recently that the expression of MITF and some of its target genes require the SWI/SNF chromatin remodeling complex. Here we demonstrate that survival of melanoma cells requires functional SWI/SNF complex not only by supporting expression of MITF and its targets and but also by activating expression of prosurvival proteins not directly regulated by MITF. Microarray analysis revealed that besides the MITF-driven genes, expression of proteins like osteopontin, IGF1, TGFß2 and survivin, the factors known to be generally associated with progression of tumors and the antiapoptotic properties, were reduced in acute BRG1-depleted 501mel cells. Western blots and RT-PCR confirmed the microarray findings. These proteins have been verified to be expressed independently of MITF, because MITF depletion did not impair their expression. Because these genes are not regulated by MITF, the data suggests that loss of BRG1-based SWI/SNF complexes negatively affects survival pathways beyond the MITF cascade. Immunohistochemistry showed high expression of both BRM and BRG1 in primary melanomas. Exogenous CDK2, osteopontin, or IGF1 each alone partly relieved the block of proliferation imposed by BRG1 depletion, implicating that more factors, besides the MITF target genes, are involved in melanoma cell survival. Together these results demonstrate an essential role of SWI/SNF for the expression of MITF-dependent and MITF-independent prosurvival factors in melanoma cells and suggest that SWI/SNF may be a potential and effective target in melanoma therapy.
Laboratory of Transcription and Cell Signaling, Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.
Lubica
L
Ondrušová
Jiri
J
Vachtenheim
Jiri
J
Réda
Petra
P
Záková
Kamila
K
Benková
D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000235:genetics / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051739:Microphthalmia-Associated Transcription Factor / Q000235:genetics* / Q000378:metabolism; D009506:Nevus / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077022:Survivin; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D053781:Transforming Growth Factor beta2 / Q000235:genetics / Q000378:metabolism
C107489:BIRC5 protein, human; D002868:Chromosomal Proteins, Non-Histone; D051034:Inhibitor of Apoptosis Proteins; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D009687:Nuclear Proteins; C084011:SMARCA2 protein, human; C445179:SWI-SNF-B chromatin-remodeling complex; D000077022:Survivin; D014157:Transcription Factors; D053781:Transforming Growth Factor beta2; D053495:Osteopontin; D007334:Insulin-Like Growth Factor I; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; C084108:SMARCA4 protein, human; D004265:DNA Helicases