Nerve infiltration has been implicated in the formation and progression of several solid tumor types including prostate, gastric, and pancreatic cancers. However, despite its neural origin, melanoma innervation has not been previously reported. In our preliminary studies, we discovered that melanoma tumor tissues from patient samples and mouse models are highly innervated. This innervation is dependent on tumor cell expression of nerve growth factor (NGF), as targeted NGF depletion eliminates intratumoral nerve fibers. Importantly, melanoma denervation via NGF knockdown or chemical sympathectomy dramatically reduces tumor burdens by remodeling the tumor microenvironment (TME). This TME reprogramming is associated with increased cytokine and chemokine expression, CD103+ DC activation, and CD8+ T cell recruitment, suggesting that NGF or nerve-derived neurotransmitters support tumor growth by suppressing antitumor immunity. Importantly, we confirmed this inverse correlation between tumor innervation and inflammation using clinical samples: melanomas expressing low levels of NGF are immunologically hot and associated with improved patient survival. These findings inspire our central hypothesis that NGF-mediated innervation of the tumor microenvironment can be exploited pharmacologically to reverse immunosuppression. In this study, we will test this hypothesis with the following three aims:
Aim 1 will dissect molecular mechanisms of NGF-mediated remodeling of the intratumor immune microenvironment.
Aim 2 will dissect molecular mechanisms by which NGF regulates T cell activation.
Aim 3 will determine the pre-clinical efficacy of a therapeutic strategy combining NGF axis inhibition and immune checkpoint blockade against melanoma. Findings from the proposed studies will lay the foundation upon which potential combinational therapies can be developed to combat this disease.
Cancer immunotherapy has shown great promise in combatting cancer, but interactions between cancer cells and the immune system or anti-tumor immune response within the tumor microenvironment remain to be explored to increase the potential of this approach as a major arsenal for cancer treatment.