O1-7-3 - CARF regulates EMT through Wnt/b-catenin signaling: its clinical relevance & potential as a therapeutic cancer target

Abstract

Background: CARF (Collaborator of ARF)/CDKN2AIP was discovered in our laboratory as a novel ARF-binding protein. It was shown to interact with p53-tumor suppressor and HDM2 proteins, and regulate p53-HDM2-p21 pathway in two directions in a dose-dependent manner. Whereas CARF-overexpression results in growth arrest, its super-high level of expression led to aggressive malignant transformation of cancer cells. Suppression of CARF, on the other hand, triggered apoptosis, suggesting that it is an essential cell survival protein and could serve as a target for cancer therapy. We demonstrated that a moderate upregulation of CARF caused growth arrest and senescence, its excessively enriched levels were shown to facilitate aggressive proliferation and malignant transformation of cancer cells. Methods: We have examined the expression level of CARF in clinical cancer datasets. CARF-enriched cells were used to investigate its role in EMT transition, malignant transformation and cancer metastasis. siRNA and shRNA were used to target CARF in vitro and in vivo. Results: We found amplification of CARF (both at gene and transcript levels) in a variety of invasive and metastatic malignancies. Consistent to the clinical readouts, CARF-enriched cells showed enhanced epithelial-mesenchymal transition (EMT). By molecular assays, we determined that the latter is mediated by activation of Wnt/b-catenin signaling axis. CARF-enriched cells showed enhanced nuclear localization and transcriptional activation of b-catenin as marked by increased level of its several effector proteins. Of note (i) CARF-silencing in cells either by siRNA or miRNA led to growth arrest of cells and (ii) CARF-targeting in vivo caused suppression of tumor progression and lung metastasis. Conclusion: We report clinical and therapeutic relevance of CARF in EMT and cancer invasiveness/metastasis, and propose it as a potent therapeutic target of aggressive cancers.