text: Because of their mechanism of action, phorbol esters can be used to study tumor proliferation and pain response. TPA is most commonly used in the laboratory to induce a cellular response. For example, TPA can be used to measure response to pain and test compounds that may mitigate the inflammatory response. TPA and other phorbol esters can also be used to induce tumor formation and to study mechanism of action. TPA, together with ionomycin, can also be used to stimulate T-cell activation, proliferation, and cytokine production, and is used in protocols for intracellular staining of these cytokines.