Ciclo Económico Municipal De Rionegro 1950 –

Metastatic melanoma is largely refractory to existing therapies and has a very poor prognosis. Despite the significant progresses made in the cancer immunotherapy field in recent years, only a small proportion of melanoma patients show positive clinical responses. There are several major barriers to improve the efficacy of immunotherapy for solid tumors. First, the

specific CD8+ T cell responses against tumor antigens can be severely dampened by the

prevalence of immunosuppressive ligands expressed within TME. Second, the immune control of tumor growth can be directly suppressed by tumor stromal fibroblasts, which suppress immune responses through different mechanisms. Third, tumor cells are capable of evading the immune pressure exerted by vaccine- or T cell transfer-induced immune responses due to the advantageous growth of non-targeted subpopulations, further impairing the efficacy of immunotherapy. In addition, T cells become functionally exhausted within the TME during tumor

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progression, which is traditionally viewed as a result of chronic exposure to cancer antigens. Our preliminary data suggest that the metabolic stresses, including glucose and oxygen limitation in late stage tumors, may lead to the metabolic alteration and functional impairment of TILs.

The overall goal of my thesis project is to develop novel immunotherapeutic strategies against melanoma that can overcome the immunosuppressiveness of the TME, reduce the exhaustion of TILs and thus achieve sustained tumor regression. The vaccines I designed against melanoma are based on chimpanzee-derived adenoviral vector AdC68, which is known to

induce potent CD8+ T cell responses. I hypothesize that the melanoma cell targeting vaccine not

only has to express multiple melanoma antigens in an immunogenic form but also has to

overcome the low responsiveness of TA-specific CD8+T cells. Furthermore, the novel cancer

treatment strategies have to contain components that directly reduce the TME’s ability to suppress tumor-specific immune responses. In my thesis I addressed this hypothesis through the following aims:

Specific Aim 1: To determine whether blocking prevalent immunoinhibitory pathway during T cell priming could reduce the exhaustion of melanoma-associated antigens

(MAAs)-specific CD8+T cells in the TME and improve the antitumor efficacy of cancer

vaccine.

Co-expression of several different immunogenic antigens in one vaccine can minimize

the frequent immune escape of tumor cells. In addition, studies by our lab have shown that vaccines expressing antigens as fusion proteins within herpes simplex virus glycoprotein D (gD) can induce markedly enhanced antigen-specific T cell responses through disruption of the immunosuppressive B-and T-lymphocyte attenuator (BTLA)-herpesvirus entry mediator (HVEM)

signaling pathway in the TME(243,244). I hypothesized that the Ad vaccine expressing multiple

immunogenic MAA epitopes fused within gD can induce high frequencies of CD8+T cells targeting

melanoma cells for destruction. Blocking the immunosuppressive signaling in activated T cells

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and exhaustion status of MAA-specific T cells induced by melanoma vaccine expressing multiple MAA epitopes fused within gD to those of T cells elicited by a vaccine expressing MAA epitopes without gD in melanoma-bearing mice.

Specific Aim 2: To determine whether depleting tumor stromal fibroblasts through vaccination could enhance the antitumor efficacy of melanoma cell targeting vaccine.

Tumor stromal fibroblasts express selectively the fibroblast activation protein (FAP),

which is not expressed by normal fibroblasts or normal adult tissues. FAP+ stromal fibroblasts suppress the immune response to tumors by attracting regulatory T cells into the tumor and

interfering with T cell-tumor cell interaction. I hypothesized that combining an Ad-based vaccine

directly targeting tumor stromal fibroblasts for destruction will enhance the efficacy of the melanoma antigen-expressing vaccine by reducing immunosuppression within TME. The frequencies and functions of immunosuppressive cells may change upon FAP+ stromal cell

depletion, which may also reduce the exhaustion of MAA-specific TILs. To study the effect of

FAP+ stromal cell depletion, I designed an AdC68-based vaccine targeting murine full-length FAP protein. The effects of the vaccine given either alone or in combination with the MAA targeting vaccine were tested in both a B16 transplantable tumor model and a clinically relevant inducible transgenic melanoma mouse model.

Specific Aim 3: To determine whether metabolic challenges within TME contribute to T cell functional exhaustion and to explore novel strategies to alter the metabolism of TILs in order to improve their functions.

The TME poses significant metabolic challenges to TILs due to disorganized vascularization, presence of toxic products derived from tumor and stromal cells and lack of

nutrients and oxygen (O2)(245). TILs require energy to eliminate tumor cells. Upon activation T

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but provides building blocks for biomass formation and cell proliferation. Tumor cells also use glycolysis(247), which may lead to Glu depletion within the TME(192,197). T cells with limited access to Glu have to rely on OXPHOS to produce energy. Although many substances including

FAs can fuel OXPHOS, it requires O2, which can become limiting within tumors due to insufficient

blood supply(248). TILs therefore face dual metabolic jeopardy, which I hypothesize drives their

functional exhaustion and thereby impairs the efficacy of cancer immunotherapy. I studied the

effects of metabolic stress within the TME on differentiation and effector functions of CD8+TILs in a B16 melanoma mouse model. Melanoma-bearing mice were immunized with a mixture of vaccines that induce CD8+T cells specific for MAAs and an unrelated tumor antigen (TA), i.e. E7 of human papilloma virus (HPV)-16. I analyzed the metabolism, differentiation and functions of both MAA- and E7-specific TILs in spleens, small tumors or late stage tumors using a series of transcriptional profile, flow and metabolomics analysis. The impact of metabolic challenges on the

tumoricidal functions of effector T cells was studied both in vitro and in vivo. Moreover, I explored

strategies to manipulate the metabolism of TILs in order to improve their tumor-killing capacity in the TME.

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In document Plan estratégico de marketing para el desarrollo de la gestión de marca origen del cacao en beneficio de la construcción de una identidad agroindustrial en Colombia (página 168-172)