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Several lines of investigation have revealed the apparent interplay between the immune system of the host and many conventional, "standard-of-care" anticancer therapies, including chemotherapy and small molecule targeted therapeutics. In particular, preclinical and clinical studies have demonstrated the important role of regulatory T cells (Tregs) in inhibiting immune responses elicited by immunotherapeutic regimens such as those based on anticancer vaccines or checkpoint inhibitors. However, how the number and immunosuppressive function of Tregs change in cancer patients undergoing treatment with non-immune anticancer therapies remains to be precisely elucidated. To determine whether immunostimulatory therapies can be employed successfully in combination with conventional anticancer regimens, we have investigated both the number and function of Tregs obtained from the peripheral blood of carcinoma patients before the initiation and during the course of chemotherapeutic and targeted agent regimens. Our studies show that the treatment of breast cancer patients with tamoxifen plus leuprolide, a gonadotropin releasing hormone agonist, has minimal effects on Tregs, while sunitinib appears to exert differential effects on Tregs among patients with metastatic renal carcinoma. However, the administration of docetaxel to patients with metastatic prostate or breast cancer, as well as that of cisplatin plus vinorelbine to non-small cell lung cancer patients, appears to significantly increase the ratio between effector T cells and Tregs and to reduce the immunosuppressive activity of the latter in the majority of patients. These studies provide the rationale for the selective use of active immunotherapy regimens in combination with specific standard-of-care therapies to achieve the most beneficial clinical outcome among carcinoma patients. [ABSTRACT FROM AUTHOR]

This study demonstrates that CD8+ T cells in the tumor microenvironment display reduced functionality and hyporesponsiveness. TGF-β contributed markedly to the tumor-infiltrating CD8+ T cells’ (TILs) reduced functionality, which could be reversed using a small molecule TGF-β inhibitor. Upon T-cell receptor (TCR) activation, the activation of ITK and ERK kinases were reduced in CD8+ TILs, as compared to splenic CD8+ T cells: TGF-β inhibitor could reverse this phenomenon. This study demonstrates for the first time the association of the Spred-1 gene, an inhibitor of the Ras/MAPK pathway, with CD8+ TILs and TGF-β activity. Spred-1 was upregulated in CD8+ TILs and TGF-β enhanced the expression of Spred-1 in effector/memory CD8+ T cells and not in rested/memory CD8+ T cells. Based on these findings, this study supports the hypothesis that TGF-β mediates an inhibitory mechanism on CD8+ TILs involving TCR-signaling blockade and the upregulation of Spred-1, thus implicating Spred-1 as a potential new target for future anti-tumor immune studies. [ABSTRACT FROM AUTHOR]

Abstract: We compared the effects of yeast-treated human dendritic cells (DCs) with CD40L-matured human DCs for the induction of effector cells and the number and functionality of CD4+CD25+CD127−FoxP3+ regulatory T cells (Tregs). DCs were treated with yeast or CD40L and cocultured with isolated autologous CD4+ T cells. CD4+CD25+CD127− T cells isolated from the coculture of CD4+ T cells plus yeast-treated DCs (yeast coculture) had a lower expression of FoxP3 and decreased suppressive function compared to CD4+CD25+CD127− T cells isolated from the coculture of CD4+ T cells plus CD40L-treated DCs (CD40L coculture). Also, compared to the CD40L coculture, the yeast coculture showed increases in the ratio of CD4+CD25+ activated T cells to Tregs and in the production of Th1-related cytokines (IL-2, TNF-α, IFN-γ) and IL-6. In addition, yeast-treated DCs used as antigen-presenting cells (APCs) incubated with the tumor antigen CEA enhanced the proliferation of CEA-specific CD4+ T cells compared to the use of CD40L-matured DCs used as APCs. This is the first study to report on the role of yeast-treated/matured human DCs in reducing Treg frequency and functionality and in enhancing effector to Treg ratios. These results provide an additional rationale for the use of yeast as a vector in cancer vaccines. [Copyright &y& Elsevier]