title: Artemisinin induces doxorubicin resistance in human colon cancer cells via calcium-dependent activation of HIF-1alpha and P-glycoprotein overexpression.
abstract: OBJECTIVE
  Artemisinin is an antimalarial drug exerting pleiotropic effects, such as the inhibition of the transcription factor nuclear factor-kappa B and of the sarcoplasmic/endoplasmic reticulum Ca(++)-ATPase (SERCA) of P. falciparum. As the sesquiterpene lactone thapsigargin, a known inhibitor of mammalian SERCA, enhances the expression of P-glycoprotein (Pgp) by increasing the intracellular Ca(++) ([Ca(++)](i)) level, we investigated whether artemisinin and its structural homologue parthenolide could inhibit SERCA in human colon carcinoma HT29 cells and induce a resistance to doxorubicin.
  
  
  METHODS
  HT29 cells were incubated with artemisinin or parthenolide and assessed for SERCA activity, [Ca(++)](i) levels, Pgp expression, doxorubicin accumulation and toxicity, and translocation of the hypoxia-inducible factor, HIF-1alpha.
  
  
  RESULTS
  Artemisinin and parthenolide, like the specific SERCA inhibitors thapsigargin and cyclopiazonic acid, reduced the activity of SERCA. They also increased intracellular calcium concentration ([Ca(++)](i)) and Pgp expression and decreased doxorubicin accumulation and cytotoxicity. The intracellular Ca(++) chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, and the inhibitor of calmodulin-dependent kinase II (CaMKII) KN93 prevented these effects. CaMKII is known to promote the phosphorylation and the activation of HIF-1alpha, which may induce Pgp. In HT29 cells, artemisinin and parthenolide induced the phosphorylation of HIF-1alpha, which was inhibited by KN93.
  
  
  CONCLUSIONS
  Our results suggest that artemisinin and parthenolide may act as SERCA inhibitors and, like other SERCA inhibitors, induce resistance to doxorubicin in human colon cancer cells, via the CaMKII-dependent activation of HIF-1alpha and the induction of Pgp.
authors.affiliation: Department of Genetics, Biology and Biochemistry, University of Torino, and Research Center on Experimental Medicine (CeRMS), Via Santena, Torino, Italy. chiara.riganti@unito.it
authors.forename: C
authors.initials: C
authors.lastname: Riganti
authors.forename: S
authors.initials: S
authors.lastname: Doublier
authors.forename: D
authors.initials: D
authors.lastname: Viarisio
authors.forename: E
authors.initials: E
authors.lastname: Miraglia
authors.forename: G
authors.initials: G
authors.lastname: Pescarmona
authors.forename: D
authors.initials: D
authors.lastname: Ghigo
authors.forename: A
authors.initials: A
authors.lastname: Bosia
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000962:Antimalarials / Q000009:adverse effects*; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D037621:Artemisinins / Q000009:adverse effects*; D002118:Calcium / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D012717:Sesquiterpenes / Q000009:adverse effects
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000962:Antimalarials; D000964:Antimetabolites, Antineoplastic; D037621:Artemisinins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012717:Sesquiterpenes; C002669:parthenolide; D004317:Doxorubicin; C031327:artemisinin; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium