title: Plasma membrane calcium ATPase 4 and the remodeling of calcium homeostasis in human colon cancer cells.
abstract: A remodeling of calcium homeostasis has been identified as a characterizing feature of some cancers. Possible consequences of this include alterations in many pivotal physiological responses including apoptosis, proliferation and gene transcription. An alteration in calcium homeostasis can occur via changes in the expression of proteins that transport calcium and examples of cancers where this is seen includes the prostate and breast. A specific isoform of the calcium efflux pump, plasma membrane Ca(2+)-ATPase (PMCA) 4, is significantly upregulated during differentiation of the HT-29 colon cancer cell line suggesting that it may also be altered in colon cancer. We now report that differentiated HT-29 colon cancer cells have pronounced plasma membrane PMCA4 localization, consistent with augmented calcium efflux. Assessment of PMCA4 transcription in human colon cancer samples suggests that PMCA4 is significantly (P < 0.000001) downregulated early in the progression of some colon cancers as these cells become less differentiated. Inhibition of PMCA4 using small interfering RNA did not induce cell death or augment sensitivity to the mitochondrial uncoupler carbonyl cyanide 3-chlorophenylhydrazone (CCCP) or tumor necrosis factor-related apoptosis-inducing ligand. Reversing the colon cancer remodeling of PMCA4 by overexpression reduced cellular proliferation (P < 0.01) and downregulated transcription of the calcium sensitive early response gene FOS. Our studies suggest that the remodeling of the calcium signal in colon cancer is associated with compromised calcium efflux at a level that promotes proliferative pathways while avoiding increased sensitivity to apoptotic stimuli.
authors.affiliation: School of Pharmacy, University of Queensland, Brisbane, 4072, Australia.
authors.forename: Cho S
authors.initials: CS
authors.lastname: Aung
authors.forename: Weilan
authors.initials: W
authors.lastname: Ye
authors.forename: Greg
authors.initials: G
authors.lastname: Plowman
authors.forename: Amelia A
authors.initials: AA
authors.lastname: Peters
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Monteith
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Roberts-Thomson
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016762:Genes, fos; D006801:Humans; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D014158:Transcription, Genetic; D014475:Uncoupling Agents / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; D014475:Uncoupling Agents; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium