Dystrophin Controls Exosome Secretion and Promotes Drug Resistance via Protein-Protein Interaction with Rab GTPase 3C in Colorectal Carcinoma

Abstract

Background: RAB GTPases is involved in membrane trafficking (vesicle formation) and cell motility. Recently, exocytotic RABs has been noted that the exocytosis by RABs is correlated with drug resistance and immune response in tumorigenesis. However, the molecular mechanisms of exocytotic RABs in colorectal tumorigenicity remain unknown. Methods: Established RAB3C-based proteomics datasets and mass spectrometry analyses and found dystrophin (DMD) is upregulated in RAB3C ectopically overexpressed colon cancer cell lines. High DMD expression levels were found correlated with poor survival in colorectal cancer patient cohorts. Findings: We further found that DMD is a rare mutant event in colorectal clinical cohort by next generation sequencing analysis. Our results showed that DMD could be stabilized by RAB3C through protein-protein interaction. Besides, our results revealed RAB3C co-localized with dystrophin complex by immunohistochemistry staining analysis. Merged DMD with RAB3C serves as a significant independent prognostic factor in colorectal cancer and is associated with several clinical parameters. In addition, dystrophin complex decreased cell membrane integrity and altered calcium channel activity for exocytosis. Interpretation: DMD is a new functional binding protein for RAB3C that affected colorectal carcinogenesis. These findings suggest a new therapeutic strategy for targeting cancer-specific protein-protein interactions in the treatment patients with colorectal cancer. Funding Statement: This study is supported by Academia Sinica grants AS-SUMMIT-108 to Michael Hsiao. Declaration of Interests: The authors have no competing financial interests to declare. Ethics Approval Statement: The studied tissues were retrieved from the Department of Pathology, Taipei Municipal Wan Fang Hospital (Taipei, Taiwan) with Institutional Review Board approval (TMU-IRB 99049).