Kinome-wide RNAi studies in human multiple myeloma identify vulnerable kinase targets, including a lymphoid-restricted kinase, GRK6

Abstract

A paucity of validated kinase targets in human multiple myeloma has delayed clinical deployment of kinase inhibitors in treatment strategies. We therefore conducted a kinome-wide small interfering RNA (siRNA) lethality study in myeloma tumor lines bearing common t(4;14), t(14;16), and t(11;14) translocations to identify critically vulnerable kinases in myeloma tumor cells without regard to preconceived mechanistic notions. Fifteen kinases were repeatedly vulnerable in myeloma cells, including AKT1, AK3L1, AURKA, AURKB, CDC2L1, CDK5R2, FES, FLT4, GAK, GRK6, HK1, PKN1, PLK1, SMG1, and TNK2. Whereas several kinases (PLK1, HK1) were equally vulnerable in epithelial cells, others and particularly G protein-coupled receptor kinase, GRK6, appeared selectively vulnerable in myeloma. GRK6 inhibition was lethal to 6 of 7 myeloma tumor lines but was tolerated in 7 of 7 human cell lines. GRK6 exhibits lymphoid-restricted expression, and from coimmunoprecipitation studies we demonstrate that expression in myeloma cells is regulated via direct association with the heat shock protein 90 (HSP90) chaperone. GRK6 silencing causes suppression of signal transducer and activator of transcription 3 (STAT3) phosphorylation associated with reduction in MCL1 levels and phosphorylation, illustrating a potent mechanism for the cytotoxicity of GRK6 inhibition in multiple myeloma (MM) tumor cells. As mice that lack GRK6 are healthy, inhibition of GRK6 represents a uniquely targeted novel therapeutic strategy in human multiple myeloma. (Blood. 2010;115:1594-1604)

Functional proteomics to dissect tyrosine kinase signalling pathways in cancer

“…PAK2 is hyperphosphorylated in ovarian cancer 73 , while an siRNA screen identified GRK6 as required for the viability of myeloma cells but not normal cells 74 . DBF4 is a regulatory subunit of the cell cycle kinase CDC7 and this complex is overexpressed in a variety of cancer cell lines and cancers 75 .…”

Overexpression of GRK6 associates with the progression and prognosis of colorectal carcinoma

“…Therefore, GRKs are hypothesized to be valuable therapeutic targets. GRK6, a member of the GRK family, is present in many human tissues, and has been implicated in multiple disease pathways (15,16). Additionally, present studies indicate that GRK6 may be implicated in the metastasis of several carcinomas, including hepatic and lung cancer, medulloblastoma and multiple myelomas (17)(18)(19).…”

“…Previous studies also revealed that endogenous GRK6 molecules contribute to the desensitization of M3 muscarinic acetylcholine in the human SH-SY5Y neuroblastoma cell line (32). Furthermore, the 'silencing' of GRK6 in myeloma cells reduced the levels of myeloid cell leukemia 1 and suppressed the phosphorylation of signal transducer and activator of transcription 3 (STST3), thereby causing a tumor-inhibitory effect (16). Additionally, Chen et al (33) demonstrated that GRK6 serves critical roles in cell adhesion and migration of three cancer cell lines (pC3, MB231 and HeLa cells) (33).…”

“…levels in CRC. Previous studies have revealed that GRK6 expression contributes to the progression of several types of cancer (11,16,18,(28)(29)(30)(31). Despite these diverse studies, the precise functions and the mechanistic actions of GRK6 have not been defined completely.…”

Cyclin G–Associated Kinase Is Necessary for Osteosarcoma Cell Proliferation and Receptor Trafficking

“…Similarly, GAK knockdown in HeLa cells (human cervix epithelioid carcinoma cell line) resulted in the promotion of cell proliferation (38). In contrast, GAK knockdown leads to cell death in myeloma tumor cells as a part of results of high-throughput kinome siRNA screening (39). GAK expression has been implicated as a prognostic biomarker in prostate cancers also, in which GAK expression increases with prostate cancer progression to androgen independence (40).…”