Deleterious c-Cbl Exon Skipping Contributes to Human Glioma

• DOI: 10.1016/j.neo.2015.06.003
• Publication Date: 2015-07-04T04:01:02Z
• Authors: Min Woo Seong; Seung Hyeun Ka; Ji Ho Park; Jong Ho Park; Hee Min Yoo; Seung Wook Yang; Jung Mi Park; Dongeun Park; Soon Tae Lee; Jae Hong Seol; Chin Ha Chung
• Keywords: 0301 basic medicine; 0303 health sciences; Reverse Transcriptase Polymerase Chain Reaction; Blotting, Western; Neoplasms. Tumors. Oncology. Including cancer and carcinogens; Exons; Glioma; Real-Time Polymerase Chain Reaction; Article; Rats; 3. Good health; ErbB Receptors; Gene Expression Regulation, Neoplastic; 03 medical and health sciences; Mutation; Tumor Cells, Cultured; Animals; Humans; Immunoprecipitation; Proto-Oncogene Proteins c-cbl; RNA, Messenger; Regulatory Elements, Transcriptional; Hypoxia; 10. No inequality; RC254-282

c-Cbl, a RING-type ubiquitin E3 ligase, downregulates various receptor tyrosine kinases (e.g., epidermal growth factor receptor (EGFR)), leading to inhibition of cell proliferation. Moreover, patients with myeloid neoplasm frequently harbor c-Cbl mutations, implicating the role of c-Cbl as a tumor suppressor. Recently, we have shown that c-Cbl downregulates αPix-mediated cell migration and invasion, and the lack of c-Cbl in the rat C6 and human A172 glioma cells is responsible for their malignant behavior. Here, we showed that c-Cbl exon skipping occurs in the glioma cells and the brain tissues from glioblastoma patients lacking c-Cbl. This exon skipping resulted in generation of two types of c-Cbl isoforms: type I lacking exon-9 and type II lacking exon-9 and exon-10. However, the c-Cbl isoforms in the cells and tissues could not be detected as they were rapidly degraded by proteasome. Consequently, C6 and A172 cells showed sustained EGFR activation. However, no splice site mutation was found in the region from exon-7 to exon-11 of the c-Cbl gene in C6 cells and a glioblastoma tissue lacking c-Cbl. In addition, c-Cbl exon skipping could be induced when cells transfected with a c-Cbl mini-gene were grown to high density or under hypoxic stress. These results suggest that unknown alternations (e.g., mutation) of splicing machinery in C6 and A172 cells and the glioblastoma brain tissues are responsible for the deleterious exon skipping. Collectively, these findings indicate that the c-Cbl exon skipping contributes to human glioma and its malignant behavior.