title: Capsaicin induces apoptosis in human small cell lung cancer via the TRPV6 receptor and the calpain pathway.
abstract: Capsaicin, the pungent ingredient of chili peppers, displays potent anti-neoplastic activity in a wide array of human cancer cells. The present manuscript examines the signaling pathways underlying the apoptotic activity of capsaicin in human small cell lung cancer (SCLC) in vitro and in vivo. Studies in neuronal cells show that capsaicin exerts its biological activity via the transient receptor potential vanilloid (TRPV) superfamily of cation-channel receptors. The TRPV family is comprised of six members (TRPV1-6). Capsaicin is a known agonist of the TRPV1 receptor. We observed that capsaicin-induced apoptosis in human SCLC cells was mediated via the TRPV receptor family; however it was independent of TRPV1. Surprisingly, the apoptotic activity of capsaicin required the TRPV6 receptor. Depletion of TRPV6 receptor by siRNA methodology abolished the apoptotic activity of capsaicin in SCLC cells. Immunostaining and ELISA showed that TRPV6 receptor was robustly expressed on human SCLC tissues (from patients) and SCLC cell lines but almost absent in normal lung tissues. This correlates with our results that capsaicin induced very little apoptosis in normal lung epithelial cells. The pro-apoptotic activity of capsaicin was mediated by the intracellular calcium and calpain pathway. The treatment of human SCLC cells with capsaicin increased the activity of calpain 1 and 2 by threefold relative to untreated SCLC cells. Such calpain activation, in response to capsaicin, was downstream of the TRPV6 receptor. Taken together, our data provide insights into the mechanism underlying the apoptotic activity of capsaicin in human SCLCs.
authors.affiliation: Department of Pharmacology, Physiology and Toxicology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, USA.
authors.forename: Jamie K
authors.initials: JK
authors.lastname: Lau
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Brown
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Dom
authors.forename: Theodore R
authors.initials: TR
authors.lastname: Witte
authors.forename: Brent A
authors.initials: BA
authors.lastname: Thornhill
authors.forename: Clayton M
authors.initials: CM
authors.lastname: Crabtree
authors.forename: Haley E
authors.initials: HE
authors.lastname: Perry
authors.forename: J Michael
authors.initials: JM
authors.lastname: Brown
authors.forename: John G
authors.initials: JG
authors.lastname: Ball
authors.forename: Rebecca G
authors.initials: RG
authors.lastname: Creel
authors.forename: C Luke
authors.initials: CL
authors.lastname: Damron
authors.forename: William D
authors.initials: WD
authors.lastname: Rollyson
authors.forename: Cathryn D
authors.initials: CD
authors.lastname: Stevenson
authors.forename: W Elaine
authors.initials: WE
authors.lastname: Hardman
authors.forename: Monica A
authors.initials: MA
authors.lastname: Valentovic
authors.forename: A Betts
authors.initials: AB
authors.lastname: Carpenter
authors.forename: Piyali
authors.initials: P
authors.lastname: Dasgupta
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D064593:Heterografts; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D015398:Signal Transduction; D055752:Small Cell Lung Carcinoma / Q000473:pathology*; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D016588:Anticarcinogenic Agents; D000970:Antineoplastic Agents; D015220:Calcium Channels; D050916:TRPV Cation Channels; C422827:TRPV6 protein, human; D002154:Calpain; D002211:Capsaicin; D002118:Calcium