Targeting alternative splicing as a new cancer immunotherapy-phosphorylation of serine arginine-rich splicing factor (SRSF1) by SR protein kinase 1 (SRPK1) regulates alternative splicing of PD1 to generate a soluble antagonistic isoform that prevents T cell exhaustion.
Cancer Immunol Immunother
; 72(12): 4001-4014, 2023 Dec.
Article
en En
| MEDLINE
| ID: mdl-37973660
ABSTRACT
BACKGROUND:
Regulation of alternative splicing is a new therapeutic approach in cancer. The programmed cell death receptor 1 (PD-1) is an immunoinhibitory receptor expressed on immune cells that binds to its ligands, PD-L1 and PD-L2 expressed by cancer cells forming a dominant immune checkpoint pathway in the tumour microenvironment. Targeting this pathway using blocking antibodies (nivolumab and pembrolizumab) is the mainstay of anti-cancer immunotherapies, restoring the function of exhausted T cells. PD-1 is alternatively spliced to form isoforms that are either transmembrane signalling receptors (flPD1) that mediate T cell death by binding to the ligand, PD-L1 or an alternatively spliced, soluble, variant that lacks the transmembrane domain.METHODS:
We used PCR and western blotting on primary peripheral blood mononuclear cells (PBMCs) and Jurkat T cells, IL-2 ELISA, flow cytometry, co-culture of melanoma and cholangiocarcinoma cells, and bioinformatics analysis and molecular cloning to examine the mechanism of splicing of PD1 and its consequence.RESULTS:
The soluble form of PD-1, generated by skipping exon 3 (∆Ex3PD1), was endogenously expressed in PBMCs and T cells and prevents cancer cell-mediated T cell repression. Multiple binding sites of SRSF1 are adjacent to PD-1 exon 3 splicing sites. Overexpression of phosphomimic SRSF1 resulted in preferential expression of flPD1. Inhibition of SRSF1 phosphorylation both by SRPK1 shRNA knockdown and by a selective inhibitor, SPHINX31, resulted in a switch in splicing to ∆Ex3PD1. Cholangiocarcinoma cell-mediated repression of T cell IL-2 expression was reversed by SPHINX31 (equivalent to pembrolizumab).CONCLUSIONS:
These results indicate that switching of the splicing decision from flPD1 to ∆Ex3PD1 by targeting SRPK1 could represent a potential novel mechanism of immune checkpoint inhibition in cancer.Palabras clave
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Empalme Alternativo
/
Colangiocarcinoma
Límite:
Humans
Idioma:
En
Revista:
Cancer Immunol Immunother
Asunto de la revista:
ALERGIA E IMUNOLOGIA
/
NEOPLASIAS
/
TERAPEUTICA
Año:
2023
Tipo del documento:
Article
País de afiliación:
Reino Unido