The GPR 55 agonist, L-α-lysophosphatidylinositol, mediates ovarian carcinoma cell-induced angiogenesis.

Nicole A Hofmann,Sunia A Trauger,Joyce Bischoff,Marsha A Moses,Dirk Strunk,Hironao Nakayama,Jiang Yang,Michael Klagsbrun,Wolfgang F Graier,Lan Huang

doi:10.1111/bph.13196

Abstract

Background and PurposeHighly vascularized ovarian carcinoma secretes the putative endocannabinoid and GPR55 agonist, L-α-lysophosphatidylinositol (LPI), into the circulation. We aimed to assess the involvement of this agonist and its receptor in ovarian cancer angiogenesis.Experimental ApproachSecretion of LPI by three ovarian cancer cell lines (OVCAR-3, OVCAR-5 and COV-362) was tested by mass spectrometry. Involvement of cancer cell-derived LPI on angiogenesis was tested in the in vivo chicken chorioallantoic membrane (CAM) assay along with the assessment of the effect of LPI on proliferation, network formation, and migration of neonatal and adult human endothelial colony-forming cells (ECFCs). Engagement of GPR55 was verified by using its pharmacological inhibitor CID16020046 and diminution of GPR55 expression by four different target-specific siRNAs. To study underlying signal transduction, Western blot analysis was performed.Key ResultsOvarian carcinoma cell-derived LPI stimulated angiogenesis in the CAM assay. Applied LPI stimulated proliferation, network formation, and migration of neonatal ECFCs in vitro and angiogenesis in the in vivo CAM. The pharmacological GPR55 inhibitor CID16020046 inhibited LPI-stimulated ECFC proliferation, network formation and migration in vitro as well as ovarian carcinoma cell- and LPI-induced angiogenesis in vivo. Four target-specific siRNAs against GPR55 prevented these effects of LPI on angiogenesis. These pro-angiogenic effects of LPI were transduced by GPR55-dependent phosphorylation of ERK1/2 and p38 kinase.Conclusions and ImplicationsWe conclude that inhibiting the pro-angiogenic LPI/GPR55 pathway appears a promising target against angiogenesis in ovarian carcinoma.

Highlights

Ovarian cancer is the most common cause of death from gynaecological cancers (Siegel et al, 2012) and a high level of angiogenesis is a poor prognostic marker in ovarian carcinoma patients (Schoell et al, 1997; Banerjee and Kaye, 2011)
That ovarian cancer cells secrete LPI, and promote tumour angiogenesis in vivo via an LPI/GPR55dependent mechanism; conditioned medium from the human ovarian cancer cell lines OVCAR-3, OVCAR-5 and COV-362 was analysed for its LPI levels and in the chorioallantoic membrane (CAM) angiogenesis model
Selective inhibition of the LPI receptor GPR55 with CID16020046 (20 μM) effectively blocked ovarian cancer-induced angiogenesis of all tested cell lines (Figure 1B). These results suggest that LPI produced by ovarian cancer cells induces angiogenesis in a GPR55dependent manner

Summary

Introduction

Ovarian cancer is the most common cause of death from gynaecological cancers (Siegel et al, 2012) and a high level of angiogenesis is a poor prognostic marker in ovarian carcinoma patients (Schoell et al, 1997; Banerjee and Kaye, 2011). Clinical studies have revealed that patients with ovarian and peritoneal cancer show elevated levels of lysophospholipids in blood and ascites fluids (Xiao et al, 2000; 2001; Xu et al, 2001; Murph et al, 2007), suggesting that lysophospholipids might be a biomarker for these highly vascularized tumours (Sutphen et al, 2004; Murph et al, 2007; Pineiro and Falasca, 2012). It was shown that L-α-lysophosphatidylinositol (LPI), but not other lysophospholipids, secreted by ovarian and prostate carcinomas regulated cancer cell growth via an autocrine loop (Pineiro et al, 2011). To study underlying signal transduction, Western blot analysis was performed

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