Both sensory neurons and immune cells, albeit at markedly different levels, express
the vanilloid (capsaicin) receptor, Transient Receptor Potential, Vanilloid-1 (TRPV1).
Activation of TRPV1 channels in sensory afferent nerve fibers induces local effector
functions by releasing neuropeptides (most notably, substance P) which, in turn, trigger
neurogenic inflammation. There is good evidence that chronic activation or inactivation
of this inflammatory pathway can modify tumor growth and metastasis. TRPV1 expression
was also demonstrated in a variety of mammalian immune cells, including lymphocytes,
dendritic cells, macrophages and neutrophils. Therefore, the effects of TRPV1 agonists
and antagonists may vary depending on the prominent cell type(s) activated and/or
inhibited. Therefore, a comprehensive understanding of TRPV1 activity on immune cells
and nerve endings in distinct locations is necessary to predict the outcome of therapies
targeting TRPV1 channels. Here, we review the neuro-immune modulation of cancer growth
and metastasis, with focus on the consequences of TRPV1 activation in nerve fibers
and immune cells. Lastly, the potential use of TRPV1 modulators in cancer therapy
is discussed.
