Increased antitumor activities of glypican-3-specific chimeric antigen receptor-modified T cells by coexpression of a soluble PD1–CH3 fusion protein

Abstract

Our recent clinical study demonstrated that glypican-3 (GPC3)-specific chimeric antigen receptor-modified T (CAR-T) cells are a promising treatment for hepatocellular carcinoma (HCC). However, the interaction of programmed cell death 1 (PD-1) and PD-L1-mediated T-cell inhibition is involved in immune evasion in a wide range of solid tumors, including HCC. To overcome this problem, we introduced a fusion protein composed of a PD-1 extracellular domain and CH3 from IgG4 into GPC3-specific CAR-T cells (GPC3-28Z) to block the PD-1/PD-L1 pathway. GPC3-specific CAR-T cells carrying the PD-1-CH3 fusion protein (sPD1) specifically recognized and lysed GPC3-positive HCC cells. The proliferation capacity of GPC3-28Z-sPD1 T cells after weekly stimulation with target cells was much higher than that of control GPC3-28Z T cells. Additionally, the coexpression of sPD1 could protect CAR-T cells from exhaustion when incubated with target cells, as phosphorylated AKT and Bcl-xL expression levels were higher in GPC3-28Z-sPD1 T cells than in GPC3-28Z cells. Importantly, in two HCC tumor xenograft models, GPC3-28Z-sPD1 T cells displayed a significantly higher tumor suppression capacity than GPC3-28Z T cells. In addition, an increased number of CD3 T cells in the circulation and tumors and increased granzyme B levels and decreased Ki67 expression levels in the tumors were observed in the mice treated with GPC3-28Z-sPD1 T cells. Together, these data indicated that GPC3-specific CAR-T cells carrying sPD1 show promise as a treatment for patients with HCC.

Immune-based therapies for hepatocellular carcinoma

“…The positive results from adoptive cellular immunotherapy and the evidence of TAA-specific responses in HCC have stimulated research into chimeric antigen receptor T-cells, which combine antigen-specificity with the potential to infuse a fully active cytotoxic effector T-cell population. Whilst initial pre-clinical evidence is promising [150,151] concerns over toxicity warrants a careful clinical development in patients with HCC [152].…”

Improved survival of chimeric antigen receptor‐engineered T (CAR‐T) and tumor‐specific T cells caused by anti‐programmed cell death protein 1 single‐chain variable fragment‐producing CAR‐T cells

“…This result is concordant with a previous report that CAR-T cells engineered to produce PD-1-CH3 fusion protein showed Bcl-xL upregulation. 25 Based on these studies, overexpression of Bcl-xL in CAR-T cells would be an interesting approach to enhance the antitumor efficacy, although oncogenic potential of Bcl-xL to induce leukemic transformation should be carefully investigated. 26,27 In order to attenuate the PD-1 inhibitory signal in CAR-T cells, several researchers have developed CAR-T-cell systems which contain a dominant-negative form of PD-1, PD-1/CD28 chimeric switch receptor, or genetic disruption of PD-1.…”

“…***P < .001, **P < .005 three recent studies reported CAR-T cells engineered to produce soluble PD-1 blockers. 25,28,29 Among these studies, two of them used NSG immune-deficient mice as recipients, so that effects on endogenous tumor-specific T cells could not be evaluated. 25,28 A report by Rafiq et al 29 used immune-competent mouse models and showed that anti-PD-1 scFv produced from CAR-T cells improved the antitumor activity of bystander T cells as well as CAR-T cells.…”

Engineered Anti‐GPC3 Immunotoxin, HN3‐ABD‐T20, Produces Regression in Mouse Liver Cancer Xenografts Through Prolonged Serum Retention

“…Sadly, most patients succumb to disease before a suitable donor can be found. New therapies are emerging for the treatment of GPC3‐targeting liver cancers in the form of antibody‐drug conjugates (ADC) and chimeric antigen receptor (CAR) T‐cell therapies, but these new technologies are still being developed and may require years of optimization. Therefore, additional therapeutic options are needed for patients currently suffering from liver cancer.…”