Abstract 1783: A combination therapy of atypical protein kinase inhibitor and phosphatidylinositol-3- kinase inhibitor reduces multidrug resistance in renal cell carcinoma (RCC)

Abstract

Renal Cell Carcinoma (RCC) is the most common type of kidney cancer (85%) of which 75% of the cases involve conventional clear cell RCC (ccRCC). Choice of treatments recommended for clear cell carcinoma and non-clear cell carcinoma are partial nephroctomy (Stage I), radical nephoroctomy (Stage II and III) and chemotherapy (stage IV). Phosphatidylinositol-3- kinase (PI3K) inhibitors are one of the most prospective candidate in the therapy of ccRCC as the PI3CA gene for p110α (a class of the catalytic sub unit of PI3K) is mutated in most of the cases. Hence, PI3K inhibitors like Alpelisib (BYL 719) can be a treatment. But current therapeutic prospects are limited to the fact that RCC is a chemotherapy-resistant cancer type that acts as a barrier for successful treatment with this inhibitor. In addition, of all the other aPKCs, PKC ί/λ and PKC ζ are reported to be frequently overexpressed in most cancer cells and to have different significant roles in tumor progression and carcinogenesis of different type of cancers. Caki-1 metastatic clear cells were treated with PKC ζ inhibitor [8-hydroxynaphthalene-1,3,6-trisulfonic acid] or ζ-stat, Alpelisib and combination of both ζ-stat and Alpelisib at different doses. The results of WST-1 shows that the combination of ζ-stat (7.5 µM) and Alpelisib (10.0 µM) has the most cytotoxicity compared to the single therapy of Alpelisib. Annexin-V/PI assay also suggested that the combination therapy caused greater percentage of apoptosis and cell death compared to the single therapy of Alpelisib. The efflux proteins, (p-glycoprotein (P-gp) and ATP-binding cassette sub-family G member 2 (ABCG2), are responsible for developing cell resistance in Caki-1 cells had reduced expression in the cells when treated with the combination treatment of Alpelisib and ζ-stat. Therefore, combination therapy of Alpelisib and an aPKC inhibitor for metastatic ccRCC can reduce expression of multi drug resistance (MDR) proteins/efflux transporter P-gp and ABCG2. Hence, this combination may be a possible treatment that might help eradicating MDR of ccRCC. Thus, a combination of Alpelisib and an aPKC inhibitor can be a two pronged approach reducing the cell proliferation and resistance. Citation Format: Khandker Mohammad Khalid. A combination therapy of atypical protein kinase inhibitor and phosphatidylinositol-3- kinase inhibitor reduces multidrug resistance in renal cell carcinoma (RCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1783.