title: Apoptosis induced by hyperthermia and verapamil in vitro in a human colon cancer cell line.
abstract: The aim of this study was to determine the mechanisms responsible for the growth inhibitory effect of hyperthermia and verapamil in human colon cancer cell line HT-29. Apoptotic cell death was verified by flow cytometry analysis. The effect of treatment with hyperthermia and verapamil on the expression of apoptosis-associated proteins including Bcl-2, p53, bax, and c-Myc was studied by Western blot analysis. Changes in intracellular calcium homeostasis was analysed by fluorescence microscopy. The combination of 42 degrees C hyperthermia and verapamil caused a significant delay of human colon cancer cell proliferation as a result of apoptosis. Administration of these agents alone did not cause any cell inhibitory effect. Our experiments have shown that HT-29 cells constitutively express apoptosis-promoting proteins, such as Bax and c-Myc, while they fail to produce Bcl-2. Therefore, we hypothesize that HT-29 cells must have Bcl-2 independent pathways to protect cells against death-inducing signals. Also, apoptosis of HT-29 cells produced by hyperthermia in the presence of verapamil is a p53-independent process. Verapamil, when it did not act as a calcium channel blocker or inhibitor of release from intracellular storages under hyperthermic conditions, accelerated the increase of [Ca2+]i in HT-29 cells which resulted in programmed cell death (apoptosis).
authors.affiliation: Department of Surgery, Lombardi Cancer Center, Georgetown University, Washington, D.C. 22207, USA.
authors.forename: I B
authors.initials: IB
authors.lastname: Shchepotin
authors.forename: V
authors.initials: V
authors.lastname: Soldatenkov
authors.forename: J T
authors.initials: JT
authors.lastname: Wroblewski
authors.forename: A
authors.initials: A
authors.lastname: Surin
authors.forename: M
authors.initials: M
authors.lastname: Shabahang
authors.forename: R R
authors.initials: RR
authors.lastname: Buras
authors.forename: R J
authors.initials: RJ
authors.lastname: Nauta
authors.forename: H
authors.initials: H
authors.lastname: Pulyaeva
authors.forename: S R
authors.initials: SR
authors.lastname: Evans
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology* / Q000627:therapeutic use; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D006979:Hyperthermia, Induced; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D002121:Calcium Channel Blockers; D014700:Verapamil; D002118:Calcium