Mect1-Maml2 fusion oncogene linked to the aberrant activation of cyclic AMP/CREB regulated genes.
Malignant salivary gland tumors can arise from a t(11;19) translocation that fuses 42 residues from Mect1/Torc1, a cyclic AMP (cAMP)/cAMP-responsive element binding protein (CREB)-dependent transcriptional coactivator, with 982 residues from Maml2, a NOTCH receptor coactivator. To determine if the Mect1-Maml2 fusion oncogene mediates tumorigenicity by disrupting cAMP/CREB signaling, we have generated in-frame deletions within the CREB-binding domain of Mect1/Torc1 for testing transformation activity and have also developed a doxycycline-regulated Mect1-Maml2 mammalian expression vector for global gene expression profiling. We observed that small deletions within the CREB-binding domain completely abolished transforming activity in RK3E epithelial cells. Further, we have shown that the ectopic induction of Mect1-Maml2 in HeLa cells strongly activated the expression of a group of known cAMP/CREB-regulated genes. In addition, we detected candidate cAMP-responsive element sites within 100 nucleotides of the transcriptional start sites of other genes activated by Mect1-Maml2 expression. In contrast, we did not observe alterations of known Notch-regulated target genes in these expression array profile experiments. We validated the results by reverse transcription-PCR in transfected HeLa, RK3E, and H2009 lung tumor cells and in mucoepidermoid cancer cells that endogenously express the fusion oncopeptide. Whereas overexpression of components of the cAMP pathway has been associated with a subset of human carcinomas, these data provide a direct genetic link between deregulation of cAMP/CREB pathways and epithelial tumorigenesis and suggest future therapeutic strategies for this group of salivary gland tumors.
Coxon
Amy
A
Genetics Branch and Cancer Therapeutics Branch, Center for Cancer Research, National Cancer Institute and the National Naval Medical Center, Bethesda, Maryland 20889, USA.
Rozenblum
Ester
E
Park
Yoon-Soo
YS
Joshi
Nina
N
Tsurutani
Junji
J
Dennis
Phillip A
PA
Kirsch
Ilan R
IR
Kaye
Frederic J
FJ
D018277:Carcinoma, Mucoepidermoid / Q000235:genetics; D000242:Cyclic AMP / Q000235:genetics*; D017362:Cyclic AMP Response Element-Binding Protein; D004318:Doxycycline / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D017434:Protein Structure, Tertiary; D012468:Salivary Gland Neoplasms / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection
C115163:CREB1 protein, human; C500984:CRTC1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; C495418:MECT1-MAML2 fusion protein, human; D015514:Oncogene Proteins, Fusion; D014157:Transcription Factors; D000242:Cyclic AMP; D004318:Doxycycline