Abstract 166: Identification of Grk2 as novel oncology target and development of potent Grk2 inhibitors
Authors: Lantermann Alexandra , Chekler Eugene , Lefker Bruce , Yuen Garmen , Lam Vanessa , Strickland Matthew , Pennacchio Justyne , Fulgham Aaron , Bree Dara , Perekslis Thomas , Piizzi Grazia , Dai Hongyue , Zheng Tim , Wagner John , Huang Pearl 
Published: June 2022

Abstract
G Protein-Coupled Receptor Kinase 2 (Grk2) is a serine-threonine kinase widely expressed in the human body. The GRK family of kinases is known for its role in GPCR phosphorylation and desensitization upon GPCR activation by agonists. Besides its role in GPCR phosphorylation, Grk2 has been shown to phosphorylate non-GPCR receptors and cytoplasmic substrates and has also been demonstrated to play phosphorylation-independent roles in cells. Using pooled CRISPR screening we identified that Grk2 knockout inhibits pancreatic and bladder cancer cell line proliferation in vitro and tumor growth in xenografts in vivo, which has not been demonstrated before. Rescue experiments re-expressing wildtype or kinase inactive Grk2 showed that this effect is dependent on catalytically active Grk2. We developed Grk2 inhibitors with exquisite enzymatic potency and anti-proliferative activity in pancreatic cancer cell lines. On a cellular level Grk2 knockout and Grk2 inhibitors slow down G2/M cell cycle progression in pancreatic cancer cell lines, and Grk2 inhibitor CYG-N-2278 induced a 71% tumor growth inhibition in PAXF1657 pancreatic PDX-derived xenografts. Besides its direct role in cancer cell growth Grk2 also plays a role in immune cell function. Grk2 is highly expressed in immune cells, and we have demonstrated that Grk2 inhibitors upregulate proinflammatory cytokine expression in myeloid cells. In the MC38 colorectal syngeneic tumor model implanted into immunocompetent C57BL6 mice CYG-N-2278 Grk2 inhibitor resulted in a 39% tumor growth inhibition, whereas no effect was observed on MC38 tumor growth in immunodeficient NSG mice, suggesting an immune cell mediated tumor growth inhibition. Analysis of The Cancer Genome Atlas data has showed that Grk2 is amplified across multiple tumor types, including bladder, uterine and cholangiocarcinoma cancer, and that Grk2 amplification is prognostic for tumor outcome, confirming the human relevance and suggesting a translatable patient selection strategy. In conclusion, we identified Grk2 as novel target for oncology, demonstrating a direct effect of Grk2 inhibition on cancer cells through inhibiting G2/M cell cycle progression and an indirect effect on tumor growth through immune cell activation. Cygnal’s Grk2 inhibitors possess superior potency over previous Grk2 inhibitors and have shown promising preclinical anti-tumor efficacy.
Citation Format: Alexandra Lantermann, Eugene Chekler, Bruce Lefker, Garmen Yuen, Vanessa Lam, Matthew Strickland, Justyne Pennacchio, Aaron Fulgham, Dara Bree, Thomas Perekslis, Grazia Piizzi, Hongyue Dai, Tim Zheng, John Wagner, Pearl Huang. Identification of Grk2 as novel oncology target and development of potent Grk2 inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 166.