Increased Notch receptors induces CD8(+) T cell exhaustion in patients with prostate cancer

Abstract

Objective: To investigate Notch receptor expression in CD8(+) T cells in patients with prostate cancer, and to assess the influence of Notch signaling pathway on the function of CD8(+)T cells inpatients with prostate cancer. Methods: Forty-five patients with prostate cancer, forty-one patients with nonbacterial prostatitis, and thirty healthy controls who were hospitalized or followed-up in Shanxi Provincial People's Hospital between November 2017 and June 2018 were enrolled. CD8(+)T cells were purified, and mRNA relative levels of Notch1-4 were semi-quantified by reverse transcriptional real-time PCR. CD8(+)T cells were stimulated with Notch signaling inhibitor γ-secretase inhibitor (GSI). mRNA relative levels of perforin, granzyme B, and FasL were semi-quantified by reverse transcriptional real-time PCR. Percentages of PD-1 and CTLA-4 positive cells were investigated by flow cytometry. Direct contact and indirect contact coculture systems were set up between CD8(+)T cells and prostate cancer cell line LAPC4 cells. The influence of Notch signaling inhibition to CD8(+)T cell cytotoxicitywas assessed by measuringtarget cell death and cytokine secretion. One-Way ANOVA, LSD-t test, and paired t test was used for comparison. Results: mRNA relative levels of Notch1~4 were elevated in CD8(+)T cells from prostate cancer patients when compared with those from healthy controls and nonbacterial prostatitis patients (all P<0.05). There was CD8(+)T cell exhaustion in prostate cancer patients, which presented as decreased mRNA relative levels of perforin, granzyme B, and FasL (all P<0.000 1), as well as increased percentage of PD-1(+)CD8(+) (19.3%±5.4%) and CTLA-4(+)CD8(+)(11.7%±3.9%) cells. CD8(+)T cells from prostate cancer patients induced LAPC cell death was downregulated in direct contact coculture system (28.8%±6.4% vs 37.2%±2.6%, P=0.015). IFN-γsecretion was also reduced ((61.7±10.6)ng/L vs (88.6±20.2)ng/L, P=0.003 2). Inhibition of Notch signaling by GSI increased mRNA of perforin, granzyme B, and FasL in CD8(+)T cells from prostate cancer patients (all P<0.01), while reduced percentage of PD-1(+)CD8(+)(12.6%±2.5% vs 17.4%±4.7%, P=0.005 9) and CTLA-4(+)CD8(+) (12.0%±1.0% vs 14.1%±3.1%, P=0.011)cells. Notch signaling inhibition promoted LAPC4 cell death (34.3%±7.2%, P=0.000 2) which induced by prostate cancer derived CD8(+)T cells, and increased IFN-γ production ((88.4±33.6)ng/L, P=0.008 3). Conclusion: Elevated Notch receptors induced CD8(+)T cells exhaustion in prostate cancer patients.