Downregulation effect of CD147 expression via ScFv-M6-1B9 intrabody on apoptotic induction of colorectal cancer CaCo2 cells

Abstract

The human leukocyte surface molecule CD147 enriched on the surface of many cancer cells, which plays an important role in proliferation and metastasis. The chimeric adenoviral vector Ad5/F35 carrying gene encoding scFv against CD147 (scFv-M6-1B9) was utilized in this study to investigate the effect of CD147 downregulation on programmed cell death response in colorectal cancer (CRC) cells, Caco-2. The results showed that scFv-M6-1B9 intrabody exhibited a robust activity to reduce CD147 cell surface expression and accumulated inside the cells. Consequently, these approaches lead to decrease cell proliferation and induce apoptosis, which was relative with intracellular lactate accumulation, increasing of apoptotic bodies in sub-G1 peak, phosphatidylserine externalization as well as DNA fragmentation. Moreover, analysis of signaling pathway reveals that CD147 downregulation enhances apoptosis through mitochondrial pathway. The reduction of Bcl-2, leading to the translocation of cytochrome c from mitochondria to the cytosol, and also the dramatic activation of caspase-3 were examined by real-time RT-PCR and western blotting analysis. Furthermore, carcinoembryonic antigen (CEA), a tumor marker for CRC, was significantly diminished in both secreted protein and mRNA expression level. In conclusion, these findings suggested that CD147 downregulation by scFv-M6-1B9 intrabody has a great potential efficacy of apoptosis induction mediated mitochondrial pathway and decline in the CEA level. Thus, its benefit would be applied as future prospects for targeted gene therapy and prognostic approach to monitoring colorectal cancer.