Targeting G_i/o protein-coupled receptor signaling blocks HER2-induced breast cancer development and enhances HER2-targeted therapy

Abstract

G protein coupled receptors (GPCRs) are among the most desirable drug targets for human disease. Although GPCR dysfunction drives the development and progression of many tumors including breast cancer (BC), targeting individual GPCRs has limited efficacy as a cancer therapy because numerous GPCRs are activated. In this study, we sought a new way of blocking GPCR activation in HER2+-BC by targeting a subgroup of GPCRs that couple to Gi/o proteins (Gi/o-GPCRs). Using cell lines and transgenic mouse models, we showed in mammary epithelial cells, HER2 hyperactivation altered GPCR expression, particularly, Gi/o-GPCRs. Gi/o-GPCR stimulation transactivated EGFR and HER2, which in turn activated the PI3K/AKT and Src pathways. Uncoupling Gi/o-GPCRs from cognate Gi/o proteins by pertussis toxin (PTx) inhibited BC cell proliferation and migration in vitro and suppressed HER2-driven tumor formation and metastasis in vivo. Moreover, targeting Gi/o-GPCR signaling via PTx, PI3K, or Src inhibitors enhanced HER2-targeted therapy. These results indicate that HER2 hyperactivation in BC cells drives aberrant Gi/o-GPCR signaling, and Gi/o-GPCR signals converge on PI3K/AKT and Src signaling pathways to promote cancer progression and the development of resistance to HER2-targeted therapy. Our findings suggest a new way to pharmacologically deactivate GPCR signaling to block tumor growth and enhance therapeutic efficacy.

Active Gαi/o mutants accelerate breast tumor metastasis via the c-Src pathway

“…Indeed, in Neu cells and tumor samples, Gi2R179C and GoAR243H primarily enhance c-Src and EGFR transactivation. This is in stark contrast to our previous data showing that Gi/o-coupled receptor signaling contributes to the activation of multiple pathways, including c-Src and AKT, and transactivation of both EGFR and HER2 (17). The activation of additional pathways by Gi/o-GPCRs likely involve G subunits liberated from heterotrimeric Gi/o proteins since activation of heterotrimeric Gi/o proteins by GPCRs generates both functional Gi/o and G subunits and G is known to be involved in PI3K/AKT activation (3,4,(23)(24)(25).…”

“…We showed previously that G i/o -coupled GPCRs transactivate EGFR and HER2, and that their signaling converges at the AKT and c-Src pathways to promote Neu-induced breast cancer growth and metastasis (17). Western blotting analysis shows that, compared with Neu tumors, Gα i2 R179C tumors showed significantly increased phosphorylation of EGFR Y1068 and c-Src Y416 but no significant changes in phosphorylation of HER2 Y1221/1222 , STAT3 Y705 and AKT S473 (Figure 5A and 5B).…”

“…Moreover, we and others have established that Gβγ signaling is critical for breast cancer cell growth and migration induced by multiple G i/o -GPCRs (20, 24). Given that blocking G i/o -coupled receptor signaling not only delays Neu-induced tumor initiation, but also suppresses tumor growth and metastasis (17), G i/o -coupled GPCRs likely signal through both Gα i/o and Gβγ to accelerate breast tumor progression. While Gα i/o signaling primarily drives tumor metastasis, Gβγ signaling may promote both primary tumor growth and metastasis.…”

“…Our previous work found that many G i/o -coupled GPCRs are upregulated in breast cancer, and the upregulated G i/o -coupled GPCRs play a significant role in HER2-induced breast tumor initiation, growth, and metastasis (17, 18). G i/o -coupled GPCRs can transmit signals through both the dissociated Gα i/o and Gβγ subunits.…”

Endothelial Cells Promote Migration of Mesenchymal Stem Cells via PDGF-BB/PDGFRβ-Src-Akt in the Context of Inflammatory Microenvironment upon Bone Defect

“…During ASAP1regulated osteogenic differentiation of MSCs, Src and Akt were implicated and Akt served as the downstream effector. Yet, there is evidence demonstrating the regulatory effect of Akt on Src [32]. As with MSCs, the influence of Src or Akt has been generally accepted; however, little is known on their interaction with regard to motility regulation.…”