Administration of a glypican‐3 peptide increases the infiltration and cytotoxicity of CD8⁺ T cells against testicular yolk sac tumor, associated with enhancing the intratumoral cGAS/STING signaling

Abstract

BackgroundGlypican‐3 (GPC3) is highly expressed in testicular yolk sac tumor (TYST). GPC3 has been evaluated as a cancer vaccine for some types of tumors, but little is known on the effects of GPC3 peptide‐based therapy on TYST. Here, we evaluated the antitumor effect of GPC3144‐152 on TYST and its potential mechanisms.MethodsGPC3144‐152‐specific CD8+ T cells were induced by vaccine immunization and examined by ELISPOT. The CD8+ T cells were purified for testing their cytotoxicity in vitro against TYST cells by CCK‐8 and TUNEL assays and in vivo against tumor growth. The influence of GPC3144‐152 loading and/or cGAS silencing on the tumor growth, apoptosis and cGAS/STING signaling was tested by immunohistochemistry, immunofluorescence, flow cytometry, and Western blot.ResultsVaccination with GPC3144‐152 induced tumor‐specific CD8+ T cells that secreted high levels of IFN‐γ and granzyme B, and had potent cytotoxicity against TYST in a dose‐dependent manner. Adoptive transfer of CD8+ T cells and treatment with GPC3144‐152 significantly inhibited the growth of TYST tumors, but less effective for cGAS‐silenced TYST tumors in vivo. Treatment with GPC3144‐152 enhanced the infiltration of CD8+ T cells into the tumor environment and their cytotoxicity against TYST tumors in vivo by up‐regulating granzyme B and IFN‐β expression, but down‐regulating GPC3 expression in the tumors. Co‐culture of CD8+ T cells with TYST in the presence of exogenous GPC3144‐152 enhanced peptide‐specific CD8+ T‐cell cytotoxicity in vitro, accompanied by enhancing cGAS, γH2AX, TBK1, and IRF3 phosphorylation in TYST cells, but less effective in cGAS‐silenced TYST cells.ConclusionsThese data indicated that GPC3 peptide‐specific CD8+ T cells had potent antitumor activity against TYST tumor, particularly for combined treatment with the peptide, which was partially dependent on the intratumoral cGAS/STNG signaling. GPC3 peptide vaccine may be valuable for the combination treatment of TYST.

The Immune Landscape and Immunotherapeutic Strategies in Platinum-Refractory Testicular Germ Cell Tumors

“…Glypican-3 (GPC3) is an antigen that is highly expressed in yolk sac tumors providing the rationale for peptide-based vaccine therapy in this histologic TGCT subtype. Indeed, preliminary in vivo results from vaccination with GPC3144-152 showed an induction of tumor-specific CD8+ T cells secreting high levels of IFN-γ and granzyme B and led to growth inhibition in yolk sac tumors [71].…”

“…There appears to be a small proportion of TGCTs (8-18%), particularly nonsemonimatous GCTs, with gene amplification of several of the above-described immune mediators (TIGIT, LAG3, HAVCR2, NECTIN4, MET, GPC3), as illustrated on computational analysis of 149 cases from The Cancer Genome Atlas (TCGA) TGCT database (Figure 1). ical subtypes, its seems that non-seminomatous patients might derive a greater benefit, particularly those with a diagnosis of choriocarcinoma [24,29,48,71], at least partially due to a higher expression of various immune targets in NSGCTs. However, given the heterogeneity of the disease and the potential of chemotherapy to induce PD-L1 expression, particularly in metastatic seminoma patients [45], this population could be reasonably targeted as well for immune-based therapeutic approaches.…”

“…CASP3 is a protease involved in the cleavage of many substrates including PARP. Besides this role, recent TCGA pan-cancer data revealed a low methylation status of the corresponding gene in TGCTs, which was associated with tumor mutational burden and microsatellite instabil- Overall, while such preliminary evidence is still insufficient to help reach a definitive conclusion about the magnitude of immunotherapy effect across different TGCT histological subtypes, its seems that non-seminomatous patients might derive a greater benefit, particularly those with a diagnosis of choriocarcinoma [24,29,48,71], at least partially due to a higher expression of various immune targets in NSGCTs. However, given the heterogeneity of the disease and the potential of chemotherapy to induce PD-L1 expression, particularly in metastatic seminoma patients [45], this population could be reasonably targeted as well for immune-based therapeutic approaches.…”