CD4 and neoplasm: For example, the activation of TRPV1 in the tumor microenvironment of Lewis lung carcinoma triggers the release of CGRP from sensory neurons, which contributes to tumor progression through two mechanisms: first, inducing angiogenesis by upregulating VEGF, and second, suppressing the immune response by weakening cytotoxic CD8+ T cells and reducing the activity of CD4+ T cells and NK cells.