title: Mechanisms of resistance and adaptation to thapsigargin in androgen-independent prostate cancer PC3 and DU145 cells.
abstract: Cells with increasing resistance to the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor thapsigargin (TG), ranging from 60-fold (PC3/TG(10) cells) to 1350-fold (PC3/TG(2000) cells), were derived from PC3 cells. SERCA2 is overexpressed in all PC3/TG cells but retains sensitivity to TG. siRNA-mediated downregulation of SERCA completely or partially reverses TG resistance in PC3/TG(10) or PC3/TG(2000) cells, respectively; thus SERCA overexpression mediates resistance in PC3/TG(10) cells but is not the only resistance mechanism in PC3/TG(2000) cells. By contrast, SERCA is not overexpressed in TG-resistant DU145/TG cells derived from DU145 cells. DU145/TG cells retain resistance while in PC3/TG cells resistance decreases upon removal of TG selection. The transport proteins PGP/BCRP/MRP1 and anti-apoptotic proteins Bcl2/Bcl(XL) are not involved in mediating resistance in either cell line. PARP and caspase 3 cleavage in response to other drugs demonstrate that the apoptotic pathways tested remain intact in these cells. Further, no cross-resistance occurs to other drugs. Thus, novel TG-specific resistance mechanisms are recruited by these cancer cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors.forename: Dong I
authors.initials: DI
authors.lastname: Lee
authors.forename: Carlota
authors.initials: C
authors.lastname: Sumbilla
authors.forename: Myounghee
authors.initials: M
authors.lastname: Lee
authors.forename: Chidambaram
authors.initials: C
authors.lastname: Natesavelalar
authors.forename: Michael G
authors.initials: MG
authors.lastname: Klein
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Ross
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Inesi
authors.forename: Arif
authors.initials: A
authors.lastname: Hussain
mesh_terms: D000728:Androgens / Q000378:metabolism*; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D004351:Drug Resistance; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020868:Gene Silencing; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D019284:Thapsigargin / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: D000728:Androgens; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D019284:Thapsigargin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506946:ATP2A2 protein, human; D002118:Calcium