Abstract 2053: Targeting GRK2 increases chemotherapy-induced apoptosis in medulloblastoma

Abstract

Background: G protein receptor kinase-2 (GRK2; ADRBK1) belongs to the family of G protein-coupled receptor (GPCR) kinases (GRKs). GRK2 phosphorylates GPCR and non-GPCR targets including cell surface receptors, cytoskeletal and mitochondrial proteins and transcription factors. It also functions in embryonic development, heart function, metabolism, and some cancer models. Here we hypothesized that targeting GRK2 will sensitizes cancer cells to therapy. We tested this in medulloblastoma, the most common malignant brain tumor in children. Methods: siRNA transfections, shRNA viral infections, SDS-PAGE, western blotting, flow cytometry. Cells: UW228 and DAOY medulloblastoma. Results: We found that GRK2 inhibition promotes anti-tumor effects of chemotherapeutic drugs cisplatin and etoposide in UW228 and DAOY medulloblastoma cell lines. GRK2 silencing increased apoptosis induced by cisplatin and etoposide and GRK2 overexpression decreased apoptosis induced by these drugs in UW228 and DAOY. Time dependent studies revealed that GRK2 overexpression delayed cisplatin- and etoposide-induced apoptosis measured by the induction of Annexin V positive population and by PARP-1 cleavage. GRK2 mutants, GRK2 K220R (kinase deficient mutant) and GRK2 S670A (cannot be phosphorylated) were similar to wildtype GRK2 in delaying the cisplatin and etoposide induced apoptosis. GRK2 knockdown antagonized serum induced AKT and ERK phosphorylation in both lines whereas GRK2 overexpression promoted phosphorylation, suggesting that GRK2 is important in medulloblastoma survival pathways. Conclusions: These results demonstrate that targeting GRK2 enhances cisplatin- and etoposide-induced apoptosis in medulloblastoma cell lines and suggests that GRK2 inhibitors may enhance responsiveness of medulloblastoma to chemotherapy. Note: This abstract was not presented at the meeting. Citation Format: Anup S. Pathania, Xiuhai Ren, Min Mahdi, Gregory M. Shackleford, Anat Erdreich-Epstein. Targeting GRK2 increases chemotherapy-induced apoptosis in medulloblastoma [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 2053.