Abstract 3048: Study of mitochondria in multi-drug resistance and Polyphyllin D anti-cancer effect in hepatocellular carcinoma

Abstract

Liver cancer, being the sixth common cancer, causes approximately 700,000 deaths worldwide annually. Major treatment relies on chemotherapies because of the late diagnosis in many cases of liver cancer. However, the results are not satisfactory since the cancer cells develop multi-drug resistance (MDR), which greatly hampers the efficacy of multiple kinds of structurally different drugs, during the course of treatment. Several mechanisms of MDR were identified, the most notable one is the over-expression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp) and multi-drug resistance protein 1 (MRP-1), on plasma membrane. These transporters act as efflux pump of various types of chemo-drugs to accentuate the MDR phenotype. Nevertheless, the complete picture of MDR formation is yet to be explored. As mitochondria contribute vitally in apoptosis and energy production, in which both criteria are substantially altered in cancer context, we hypothesized that the organelle also takes part in the development of MDR in liver cancer. In our study, with the support of conventional assays such as western blotting and confocal imaging analysis, we adopted a novel approach by making use of the tunable resistive pulse sensing (TRPS) technique to characterize isolated mitochondria of HepG2 and R-HepG2, which corresponds to the native and multi-drug resistant liver cancer cell lines respectively. We identified a difference in volume and amount of mitochondria present in HepG2 and R-HepG2, plus the expression of P-gp and MRP-1 on mitochondria of R-HepG2. These suggest a potential role of mitochondria in MDR. On the other hand, a drug candidate Polyphyllin D (PD) was found to exert selective potency against R-HepG2. However, the mechanism is not lucid. We investigated the possible participation of mitochondria in this phenomenon and identified PD causes stronger swelling and membrane potential depolarization to isolated mitochondria of R-HepG2. Future attempt in elucidating pathways involved in PD toxicity will bring insight on designing therapeutics against cancer cells with MDR phenotype. This study also suggested future research in mitochondria can aid the discovery of more mechanisms in MDR development.

Citation Format: Brandon Ho Ngai, Jacky Fong Chuen Loo, Siu Kai Kong. Study of mitochondria in multi-drug resistance and Polyphyllin D anti-cancer effect in hepatocellular carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3048. doi:10.1158/1538-7445.AM2015-3048