TY - JOUR
T1 - Inhibition of G Protein–Coupled Receptor Kinase 2 Promotes Unbiased Downregulation of IGF1 Receptor and Restrains Malignant Cell Growth
AU - Crudden, Caitrin
AU - Shibano, Takashi
AU - Song, Dawei
AU - Dragomir, Mihnea P.
AU - Cismas, Sonia
AU - Serly, Julianna
AU - Nedelcu, Daniela
AU - Fuentes-Mattei, Enrique
AU - Tica, Andrei
AU - Calin, George A.
AU - Girnita, Ada
AU - Girnita, Leonard
N1 - Publisher Copyright:
©2020 American Association for Cancer Research.
PY - 2021/1/15
Y1 - 2021/1/15
N2 - The ability of a receptor to preferentially activate only a subset of available downstream signal cascades is termed biased signaling. Although comprehensively recognized for the G protein–coupled receptors (GPCR), this process is scarcely explored downstream of receptor tyrosine kinases (RTK), including the cancer-relevant insulin-like growth factor-1 receptor (IGF1R). Successful IGF1R targeting requires receptor downregulation, yet therapy-mediated removal from the cell surface activates cancer-protective b-arrestin–biased signaling (b-arr-BS). As these overlapping processes are initiated by the b-arr/IGF1R interaction and controlled by GPCR-kinases (GRK), we explored GRKs as potential anticancer therapeutic targets to disconnect IGF1R downregulation and b-arr-BS. Transgenic modulation demonstrated that GRK2 inhibition or GRK6 overexpression enhanced degradation of IGF1R, but both scenarios sustained IGF1–induced b-arr-BS. Pharmacologic inhibition of GRK2 by the clinically approved antidepressant, serotonin reuptake inhibitor paroxetine (PX), recapitulated the effects of GRK2 silencing with dose- and time-dependent IGF1R downregulation without associated b-arr-BS. In vivo, PX treatment caused substantial downregulation of IGF1R, suppressing the growth of Ewing’s sarcoma xenografts. Functional studies reveal that PX exploits the antagonism between b-arrestin isoforms; in low ligand conditions, PX favored b-arrestin1/Mdm2-mediated ubiquitination/degradation of IGF1R, a scenario usually exclusive to ligand abundancy, making PX more effective than antibody-mediated IGF1R downregulation. This study provides the rationale, molecular mechanism, and validation of a clinically feasible concept for “system bias” targeting of the IGF1R to uncouple downregulation from signaling. Demonstrating system bias as an effective anticancer approach, our study reveals a novel strategy for the rational design or repurposing of therapeutics to selectively cross-target the IGF1R or other RTK. Significance: This work provides insight into the molecular and biological roles of biased signaling downstream RTK and provides a novel “system bias” strategy to increase the efficacy of anti–IGF1Rtargeted therapy in cancer.
AB - The ability of a receptor to preferentially activate only a subset of available downstream signal cascades is termed biased signaling. Although comprehensively recognized for the G protein–coupled receptors (GPCR), this process is scarcely explored downstream of receptor tyrosine kinases (RTK), including the cancer-relevant insulin-like growth factor-1 receptor (IGF1R). Successful IGF1R targeting requires receptor downregulation, yet therapy-mediated removal from the cell surface activates cancer-protective b-arrestin–biased signaling (b-arr-BS). As these overlapping processes are initiated by the b-arr/IGF1R interaction and controlled by GPCR-kinases (GRK), we explored GRKs as potential anticancer therapeutic targets to disconnect IGF1R downregulation and b-arr-BS. Transgenic modulation demonstrated that GRK2 inhibition or GRK6 overexpression enhanced degradation of IGF1R, but both scenarios sustained IGF1–induced b-arr-BS. Pharmacologic inhibition of GRK2 by the clinically approved antidepressant, serotonin reuptake inhibitor paroxetine (PX), recapitulated the effects of GRK2 silencing with dose- and time-dependent IGF1R downregulation without associated b-arr-BS. In vivo, PX treatment caused substantial downregulation of IGF1R, suppressing the growth of Ewing’s sarcoma xenografts. Functional studies reveal that PX exploits the antagonism between b-arrestin isoforms; in low ligand conditions, PX favored b-arrestin1/Mdm2-mediated ubiquitination/degradation of IGF1R, a scenario usually exclusive to ligand abundancy, making PX more effective than antibody-mediated IGF1R downregulation. This study provides the rationale, molecular mechanism, and validation of a clinically feasible concept for “system bias” targeting of the IGF1R to uncouple downregulation from signaling. Demonstrating system bias as an effective anticancer approach, our study reveals a novel strategy for the rational design or repurposing of therapeutics to selectively cross-target the IGF1R or other RTK. Significance: This work provides insight into the molecular and biological roles of biased signaling downstream RTK and provides a novel “system bias” strategy to increase the efficacy of anti–IGF1Rtargeted therapy in cancer.
UR - http://www.scopus.com/inward/record.url?scp=85100418152&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85100418152&partnerID=8YFLogxK
U2 - 10.1158/0008-5472.CAN-20-1662
DO - 10.1158/0008-5472.CAN-20-1662
M3 - Article
C2 - 33158816
AN - SCOPUS:85100418152
SN - 0008-5472
VL - 81
SP - 501
EP - 515
JO - Cancer Research
JF - Cancer Research
IS - 2
ER -