Targeting SRPK1 to control VEGF-mediated tumour angiogenesis in metastatic melanoma

Abstract

Background:Current therapies for metastatic melanoma are targeted either at cancer mutations driving growth (e.g., vemurafenib) or immune-based therapies (e.g., ipilimumab). Tumour progression also requires angiogenesis, which is regulated by VEGF-A, itself alternatively spliced to form two families of isoforms, pro- and anti-angiogenic. Metastatic melanoma is associated with a splicing switch to pro-angiogenic VEGF-A, previously shown to be regulated by SRSF1 phosphorylation by SRPK1. Here, we show a novel approach to preventing angiogenesis—targeting splicing factor kinases that are highly expressed in melanomas.Methods:We used RT–PCR, western blotting and immunohistochemistry to investigate SRPK1, SRSF1 and VEGF expression in tumour cells, and in vivo xenograft assays to investigate SRPK1 knockdown and inhibition in vivo.Results:In both uveal and cutaneous melanoma cell lines, SRPK1 was highly expressed, and inhibition of SRPK1 by knockdown or with pharmacological inhibitors reduced pro-angiogenic VEGF expression maintaining the production of anti-angiogenic VEGF isoforms. Both pharmacological SRPK1 inhibitors and SRPK1 knockdown reduced growth of human melanomas in vivo, but neither affected cell proliferation in vitro.Conclusions:These results suggest that selective blocking of pro-angiogenic isoforms by inhibiting splice-site selection with SRPK1 inhibitors reduces melanoma growth. SRPK1 inhibitors may be used as therapeutic agents.

Alternative Splicing in CKD

“…However, it has been discovered in a screen to potently affect splicing of several apoptotic genes and to be able to decrease tumor growth in animal models. 61,62 Recently, a class of small molecule compounds that inhibit SRPK1 (SRPIN340, SPHINX), a major regulator of AS through SR-protein phosphorylation, has been shown to switch VEGF-A splicing toward the VEGF-A xxx b isoforms, and therefore inhibit angiogenesis in several mouse models including ocular neovascularization, 63 melanoma xenografts, 64 and orthotopic prostate cancer. 65 Administration of rhVEGF 165 b is therapeutic in mouse models of DN.…”

Modulators of alternative splicing as novel therapeutics in cancer

“…However, it has been found in a screen to potently affect splicing of several genes involved in apoptosis and further-on to be able to decrease tumour growth in animal models [25] . Recently a class of small molecule compounds that inhibit SRPK1, a major regulator of AS through SR-protein phosphorylation, has been shown to inhibit VEGF splicing and angiogenesis in a model of ocular neovascularization [26] as well as melanoma xenografts growth [27] and orthotopic prostate cancer mouse models [28] . Potentially, other types of molecules could be involved in splicing modulation, like chemicals that affect splice factor/RNA interactions or molecules that affect directly the tertiary structure of a particular splice junction (Figure 1).…”

Contradictory Relationships between Cancer and Normal Cells and Implications for Anti-cancer Therapy

“…Another positive feedback mechanism between CD147 and insulin-like growth factor-1 (IGF-1) has been observed between cancerous and endothelial cells, and it also promotes the proliferation of tumor and vascular endothelial cells (Chen, Gou et al, 2012). Recent studies identified a key molecule in tumor cells, serinearginine protein kinase 1 (SRPK1), which is one main regulator of angiogenesis (Lucas et al, 2014;Brakspear et al, 2014;Brimacombe et al, 2014). SRPK1 can splice the pre-mRNA of vascular endothelial growth factor (VEGF) into pro-angiogenic mRNA.…”