title: HCT116 cells deficient in p21(Waf1) are hypersensitive to tyrosine kinase inhibitors and adriamycin through a mechanism unrelated to p21 and dependent on p53.
abstract: p21(Waf1) (p21) was described as a cyclin-dependent kinase inhibitor, but other p21 activities have subsequently been described, including its ability to inhibit apoptosis in some models. Comparative work on the human colon cancer isogenic cell lines HCT116 and HCT116p21(-/-) led to the proposal that p21 protects colon cancer cells against apoptosis by genotoxic drugs. We asked whether p21 also protected from cell death induced by non-genotoxic drugs, such as tyrosine kinase inhibitors. We found that p21-deficient cells were dramatically more sensitive towards imatinib and gefitinib than parental cells. Interestingly, HCT116p21(-/-) also showed higher basal activity of protein kinases as c-Abl, c-Src, and Akt. We generated HCT116p21(-/-) sublines with inducible p21 expression and found that p21 did not rescue the hypersensitivity to imatinib. Moreover, down-regulation of p21 by enforced c-Myc expression or by p21 siRNA did not sensitize parental HCT116 cells. We found that, in HCT116p21(-/-) cells, p53 showed higher stability, higher transcriptional activity and phosphorylation in serines associated with p53 activity. Furthermore, silencing of p53 with siRNA and inactivation of p53 with a dominant negative mutant rescued the hypersensitive response to kinases inhibitors, 5-fluorouracil and adriamycin in HCT116p21(-/-) cells. Consistently, HCT116p53(-/-) cells are more resistant to imatinib than parental cells, suggesting that imatinib activity is partly dependent on p53 in colon cancer cells. We conclude that high p53 activity, rather than p21 deficiency, is the mechanism responsible for hypersensitivity to drugs of HCT116p21(-/-) cells. Therefore the role of p21 on apoptosis of HCT116 colon cancer cells should be re-evaluated.
authors.affiliation: Dpto de Biología Molecular, Instituto de Biomedicina y Biotecnología de Cantabria, Universidad de Cantabria-CSIC-IDICAN, Santander, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Ferrandiz
authors.forename: Jorge
authors.initials: J
authors.lastname: Martin-Perez
authors.forename: Rosa
authors.initials: R
authors.lastname: Blanco
authors.forename: Derya
authors.initials: D
authors.lastname: Donertas
authors.forename: Axel
authors.initials: A
authors.lastname: Weber
authors.forename: Martin
authors.initials: M
authors.lastname: Eilers
authors.forename: Paolo
authors.initials: P
authors.lastname: Dotto
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Delgado
authors.forename: Javier
authors.initials: J
authors.lastname: Leon
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001549:Benzamides; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D004317:Doxorubicin / Q000494:pharmacology*; D000077156:Gefitinib; D045325:HCT116 Cells; D006801:Humans; D000068877:Imatinib Mesylate; D051379:Mice; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D055550:Protein Stability; D011743:Pyrimidines / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000502:physiology*
chemical_list: D000903:Antibiotics, Antineoplastic; D001549:Benzamides; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D011799:Quinazolines; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin; D000068877:Imatinib Mesylate; D000077156:Gefitinib