Gene expression profiling analysis of CRTC1-MAML2 fusion oncogene-induced transcriptional program in human mucoepidermoid carcinoma cells.
BACKGROUND
Mucoepidermoid carcinoma (MEC) arises from multiple organs and accounts for the most common types of salivary gland malignancies. Currently, patients with unresectable and metastatic MEC have poor long-term clinical outcomes and no targeted therapies are available. The majority of MEC tumors contain a t(11;19) chromosomal translocation that fuses two genes, CRTC1 and MAML2, to generate the chimeric protein CRTC1-MAML2. CRTC1-MAML2 displays transforming activity in vitro and is required for human MEC cell growth and survival, partially due to its ability to constitutively activate CREB-mediated transcription. Consequently, CRTC1-MAML2 is implicated as a major etiologic molecular event and a therapeutic target for MEC. However, the molecular mechanisms underlying CRTC1-MAML2 oncogenic action in MEC have not yet been systematically analyzed. Elucidation of the CRTC1-MAML2-regulated transcriptional program and its underlying mechanisms will provide important insights into MEC pathogenesis that are essential for the development of targeted therapeutics.


METHODS
Transcriptional profiling was performed on human MEC cells with the depletion of endogenous CRTC1-MAML2 fusion or its interacting partner CREB via shRNA-mediated gene knockdown. A subset of target genes was validated via real-time RT-PCR assays. CRTC1-MAML2-perturbed molecular pathways in MEC were identified through pathway analyses. Finally, comparative analysis of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles was carried out to assess the contribution of CREB in mediating CRTC1-MAML2-induced transcription.


RESULTS
A total of 808 differentially expressed genes were identified in human MEC cells after CRTC1-MAML2 knockdown and a subset of known and novel fusion target genes was confirmed by real-time RT-PCR. Pathway Analysis revealed that CRTC1-MAML2-regulated genes were associated with network functions that are important for cell growth, proliferation, survival, migration, and metabolism. Comparison of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles revealed common and distinct genes regulated by CRTC1-MAML2 and CREB, respectively.


CONCLUSIONS
This study identified a specific CRTC1-MAML2-induced transcriptional program in human MEC cells and demonstrated that CRTC1-MAML2 regulates gene expression in CREB-dependent and independent manners. Our data provide the molecular basis underlying CRTC1-MAML2 oncogenic functions and lay a foundation for further functional investigation of CRTC1-MAML2-induced signaling in MEC initiation and maintenance.
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA. jiejennychen@gmail.com.
Jie
J
Chen
Sanford Burnham Prebys Medical Discovery Institute at Lake Nona, Orlando, FL, 32827, USA. jlli@sbpdiscovery.org.
Jian-Liang
JL
Li
Deparment of Molecular Genetics and Microbiology, UF Health Cancer Center, University of Florida, Gainesville, FL, 32610, USA. zirong@ufl.edu.
Zirong
Z
Chen
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA. James_Griffin@dfci.harvard.edu.
James D
JD
Griffin
Deparment of Molecular Genetics and Microbiology, UF Health Cancer Center, University of Florida, Gainesville, FL, 32610, USA. lzwu@ufl.edu.
Lizi
L
Wu
D018277:Carcinoma, Mucoepidermoid / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D020869:Gene Expression Profiling / Q000379:methods*; D057809:HEK293 Cells; D006801:Humans; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000096:biosynthesis / Q000235:genetics*; D015534:Trans-Activators; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*
C500984:CRTC1 protein, human; D004268:DNA-Binding Proteins; C471297:MAML2 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D015534:Trans-Activators; D014157:Transcription Factors