Table 1.

Potential molecules that were under investigation

Molecule	Mechanisms	Ref.
Capsaicin/resiniferatoxin	Activation of vanilloid receptors on cancer cells, inducing apoptosis	Hartel et al[17]
MEN 11467	NK-1R antagonists, inhibiting cell growth and neuronal invasion	Friess et al[18]
HSV-Enk viral vector	Increased met-enkephalin production in the peripheral nerve terminal endings and in dorsal root ganglion, reducing pain	Lu et al[45] Yang et al[46]
Phentolamine	Alpha-adrenergic blockade of sympathetic induced pain	Yasukawa[47]

NK-1R: Neurokinin-1 receptors; HSV-enk: Herpes simplex virus carrying the human preproenkephalin.