S-15 in combination of Akt inhibitor promotes the expansion of CD45RA(−)CCR7(+) tumor infiltrating lymphocytes with high cytotoxic potential and downregulating PD-1(+)Tim-3(+) cells as well as regulatory T cells

BACKGROUND: Autologous tumor-infiltrating lymphocytes (Tils) immunotherapy is a promising treatment in patients with advanced hepatocellular cancer. Although Tils treatment has shown great promise, their persistence and the efficacy after adoptive-transfer are insufficient and remain a challenge. Studies have demonstrated that IL-15 and Akt inhibitor can regulate T cell differentiation and memory. Here, we constructed S-15 (Super human IL-15), a fusion protein consisting of human IL-15, the sushi domain of the IL-15 receptor α chain and human IgG-Fc. Herein we compared the effects of S-15 with IL-2 or in combination with Akti on the expansion and activation of Tils. METHODS: Hepatocellular cancer tissues were obtained from 6 patients, Tils were expanded using IL-2, IL-2/S-15, IL-2/Akti or in combination IL-2/S-15/Akti. At day 10, anti-CD3 antibody was added to the culture media and expanded to day 25. The composition, exhaustion and T-cell differentiation markers (CD45RA/CCR7) were analyzed by flow cytometry. RESULTS: We found that IL-2/S-15/Akti expanded Tils and showed the highest percentage of central memory CD45RA(−)CCR7(+) phenotype prior to anti-CD3 antibody activation and after anti-CD3 antibody activation. T cells cultured with IL-2/S-15/Akti exhibited a mixture of CD4(+), CD8(+), and CD3(+)CD4(−)CD8(−) T cells; S-15 in combination with Akt inhibitor downregulated the expression of PD-1(+)Tim-3(+) on Tils and decreased the Tregs in Tils. Additionally, the Tils expanded in the presence of the Akt inhibitor and S-15 showed enhanced antitumor activity as indicated by the increase in IFN-γ producing tumor infiltrating CD8(+) T cells and without comprising the Tils expansion. CONCLUSION: Our study elucidates that IL-2/S-15/Akti expanded Tils and represent a viable source for the cellular therapy for patients with hepatocellular cancer.