Crucial Role of TNF-α in CD8 T Cell-Mediated Elimination of 3LL-A9 Lewis Lung Carcinoma Cells In Vivo

Abstract

The role of perforin, IFN-γ, and TNF-α in anti-tumor CD8 T cell immunity was examined in a new tumor model using a CD8 T cell epitope (GP33) derived from lymphocytic choriomeningitis virus as a tumor-associated Ag. In contrast with parental 3LL-A9 (A9) Lewis lung carcinoma cells that progressively grow in C57BL/6 mice, s.c. injection of GP33-transfected A9GP33 tumor cells induced a protective GP33-specific CD8 T cell response that led to complete tumor cell elimination. Tumor regression was dependent on perforin, IFN-γ, or TNF-α, because A9GP33 tumors developed in mice deficient in one of these genes. A9GP33 tumors arising in perforin- and IFN-γ-deficient mice represented GP33 Ag-loss variants, demonstrating that GP33-specific CD8 T cells from these mice were able to exert an Ag selection pressure. In contrast, tumor cells growing in TNF-α knock-out mice still expressed the tumor-associated GP33 peptide despite the presence of activated GP33-specific CD8 T cells. These findings provide evidence for a crucial role of TNF-α in A9 tumor cell elimination by CD8 T cells in vivo.

Solid tumors “melt” from the inside after successful CD8 T cell attack

“…Thus, the conclusions drawn from these results may also be valid for other solid tumors. Our previous work revealed that regression of A9 GP33 tumors in B6 mice is dependent on perforin, IFN-c and TNF activity [36]; here we show that T cell-mediated rejection of MCA102 GP33 tumor cell challenge in immunized mice (protective immunity) also requires IFN-c but not perforin.…”

“…We showed previously that 3LL-A9 Lewis lung carcinoma cells (designated A9 cells in this study) grow progressively in C57BL/6 (B6) mice, whereas subcutaneous (s.c.) injection of GP33-transfected A9 GP33 tumor cells, expressing the MHC class I-restricted T cell epitope GP33 from LCMV as a tumor-associated model antigen, results in transient growth followed by regression [36]. To examine the importance of GP33-specific T cells in this tumor model, ALB1 tg mice expressing GP33 under the control of the albumin promoter were used.…”

“…The generation of LCMV GP33-transfected 3LL-A9 GP33 [36] and MCA102 GP33 [38] tumor cells has been described. Tumor cells were cultured in DMEM high glucose supplemented with 10% heat-inactivated FCS, L-glutamine, streptomycin and penicillin (all from Gibco, Gaithersburg, MD).…”

Engineered CD8+ cytotoxic T cells with fiber-modified adenovirus-mediated TNF-α gene transfection counteract immunosuppressive interleukin-10-secreting lung metastasis and solid tumors

“…The enhancement of in vivo therapeutic effect of the engineered T TNF cells observed in this study may not be due to its upregulated expression of perforin, but may be associated with its enhanced secretion of the transgenecoded human TNF-a as well as its elongated survival in vivo. TNF-a plays an essential role in CD8 þ T-cellmediated elimination of tumors in vivo 52,55 possibly by its direct cytotoxicity to tumor cells leading apoptosis through engagement of the p55 TNF-a receptor I. 56 The inflammatory cytokine TNF-a also activates macrophages, natural killer cells and T cells 20,57 by its binding to the p75 TNF-a receptor II (TNFRII).…”

“…56 The inflammatory cytokine TNF-a also activates macrophages, natural killer cells and T cells 20,57 by its binding to the p75 TNF-a receptor II (TNFRII). 55 In addition, it deactivate aVb3 integrin on angiogenic endothelial cells leading to lack of adhesion and apoptosis 58 and promoting intravascular thrombosis. 59 Recently, it has further been reported that TNF-a inhibits the suppressive function of regulatory T (Tr) cells by upregulated expression of TNFRII on Tr cells leading to downregulation of FoxP3 expression.…”