Amplifying TLR-MyD88 signals within tumor-specific T cells enhances antitumor activity to suboptimal levels of weakly immunogenic tumor antigens.

The efficacy of T cell-based immunotherapy to treat cancer patients remains a challenge partly because of the weak activity toward subdominant tumor antigens (TAg) and to tumors expressing suboptimal TAg levels. Recent reports indicate that Toll-like receptor (TLR) stimulation on T cells can lower the activation threshold. In this study, we examined the antitumor activity and survival of TLR2-MyD88-stimulated CD8 T cells derived from melanoma patients and T-cell receptor transgenic pmel mice. TLR2-stimulated pmel CD8 T cells, but not TLR2(-/-)pmel or MyD88(-/-)pmel T cells, responded to significantly lower TAg levels and resulted in increased production of effector molecules and cytotoxicity. Wild-type or MyD88(-/-) mice treated with TLR2 ligand and pmel T cells, but not TLR2(-/-)pmel or MyD88(-/-)pmel T cells, showed tumor regression of an established melanoma tumor. Overexpressing TLR2 in TAg-specific T cells eradicated tumors; four times fewer cells were needed to generate antitumor responses. The enhanced antitumor activity of TLR2-MyD88-stimulated T cells was associated with increased effector function but perhaps more importantly with improved survival of T cells. Activating TLR-MyD88 signals in patient-derived T cells also reduced the activation threshold to several weakly immunogenic TAgs, resulting in increased cytokine production, expansion, and cytotoxicity. These data highlight a previously unappreciated role for activating TLR-MyD88 signals in tumor-reactive T lymphocytes.

Geng D ，Zheng L ，Srivastava R ，Velasco-Gonzalez C ，Riker A ，Markovic SN ，Davila E ... -  《-》

Cross-talk between 4-1BB and TLR1-TLR2 Signaling in CD8+ T Cells Regulates TLR2's Costimulatory Effects.

The activation of TLR-MyD88 (Toll-like receptor-myeloid differentiation factor 88) signaling within T cells functions as a potent costimulatory signal that boosts antitumor and antiviral responses. However, the molecular mechanisms underlying the costimulatory processes are poorly understood. We compared microarray gene analysis data between TLR1-TLR2-stimulated and unstimulated T-cell receptor transgenic "pmel" and MyD88(-/-) pmel CD8(+) T cells and identified changes in the expression of several TNF family members. In particular, TLR stimulation increased 4-1BB levels in pmel but not in MyD88(-/-)pmel T cells. A link between 4-1BB and TLR1-TLR2 signaling in CD8(+) T cells was highlighted by the suboptimal responses of 4-1BB(-/-) T cells to TLR1-TLR2 agonist, but their normal response to CD28 or OX40 costimulation. Blocking 4-1BB signaling with antibodies also hindered the costimulatory effects of the TLR1-TLR2 agonist. The elevated levels of 4-1BB transcripts in TLR1-TLR2-stimulated cells were not due to increased mRNA stability nor increased histone activation, but instead were associated with increased binding of p65 and c-Jun to two distinct 4-1BB promoter sites. Combining TLR1-TLR2 ligand with an agonistic antibody to 4-1BB enhanced the antitumor activity in mice with established melanoma tumors. These studies reveal that the costimulatory effects of TLR1-TLR2 signaling in CD8(+) T cells are in part mediated by 4-1BB and are important for mounting an effective antitumor immune response. Cancer Immunol Res; 4(8); 708-16. ©2016 AACR.

Joseph AM ，Srivastava R ，Zabaleta J ，Davila E ... -  《-》

Mycobacterium indicus pranii therapy induces tumor regression in MyD88- and TLR2-dependent manner.

Kumar P ，Das G ，Bhaskar S 《-》

A Synthetic CD8α:MyD88 Coreceptor Enhances CD8(+) T-cell Responses to Weakly Immunogenic and Lowly Expressed Tumor Antigens.

T cell-based immunotherapies are a promising approach for patients with advanced cancers. However, various obstacles limit T-cell efficacy, including suboptimal T-cell receptor (TCR) activation and an immunosuppressive tumor environment. Here, we developed a fusion protein by linking CD8α and MyD88 (CD8α:MyD88) to enhance CD8+ T-cell responses to weakly immunogenic and poorly expressed tumor antigens. CD8α:MyD88-engineered T cells exhibited increased proliferation and expression of effector and costimulatory molecules in a tumor antigen-dependent manner. These effects were accompanied by elevated activation of TCR and Toll-like receptor signaling-related proteins. CD8α:MyD88-expressing T cells improved antitumor responses in mice. Enhanced antitumor activity was associated with a unique tumor cytokine/chemokine signature, improved T-cell infiltration, reduced markers of T-cell exhaustion, elevated levels of proteins associated with antigen presentation, and fewer macrophages with an immunosuppressive phenotype in tumors. Given these observations, CD8α:MyD88 represents a unique and versatile approach to help overcome immunosuppression and enhance T-cell responses to tumor antigens. Cancer Res; 77(24); 7049-58. ©2017 AACR.

Kaczanowska S ，Joseph AM ，Guo J ，Tsai AK ，Lasola JJ ，Younger K ，Zhang Y ，Gonzales CV ，Davila E ... -  《-》

When Toll-like receptor and T-cell receptor signals collide: a mechanism for enhanced CD8 T-cell effector function.

Geng D ，Zheng L ，Srivastava R ，Asprodites N ，Velasco-Gonzalez C ，Davila E ... -  《-》