title: Influence of MLH1 on colon cancer sensitivity to poly(ADP-ribose) polymerase inhibitor combined with irinotecan.
abstract: Poly(ADP-ribose) polymerase inhibitors (PARPi) are currently evaluated in clinical trials in combination with topoisomerase I (Top1) inhibitors against a variety of cancers, including colon carcinoma. Since the mismatch repair component MLH1 is defective in 10-15% of colorectal cancers we have investigated whether MLH1 affects response to the Top1 inhibitor irinotecan, alone or in combination with PARPi. To this end, the colon cancer cell lines HCT116, carrying MLH1 mutations on chromosome 3 and HCT116 in which the wild-type MLH1 gene was replaced via chromosomal transfer (HCT116+3) or by transfection of the corresponding MLH1 cDNA (HCT116 1-2) were used. HCT116 cells or HCT116+3 cells stably silenced for PARP-1 expression were also analysed. The results of in vitro and in vivo experiments indicated that MLH1, together with low levels of Top1, contributed to colon cancer resistance to irinotecan. In the MLH1-proficient cells SN-38, the active metabolite of irinotecan, induced lower levels of DNA damage than in MLH1-deficient cells, as shown by the weaker induction of γ-H2AX and p53 phosphorylation. The presence of MLH1 contributed to induce of prompt Chk1 phosphorylation, restoring G2/M cell cycle checkpoint and repair of DNA damage. On the contrary, in the absence of MLH1, HCT116 cells showed minor Chk1 phosphorylation and underwent apoptosis. Remarkably, inhibition of PARP function by PARPi or by PARP-1 gene silencing always increased the antitumor activity of irinotecan, even in the presence of low PARP-1 expression.
authors: Department of System Medicine, University of Rome 'Tor Vergata', I-00133 Rome, Italy.
authors: Lucio
authors: L
authors: Tentori
authors: Carlo
authors: C
authors: Leonetti
authors: Alessia
authors: A
authors: Muzi
authors: Annalisa Susanna
authors: AS
authors: Dorio
authors: Manuela
authors: M
authors: Porru
authors: Susanna
authors: S
authors: Dolci
authors: Federica
authors: F
authors: Campolo
authors: Patrizia
authors: P
authors: Vernole
authors: Pedro Miguel
authors: PM
authors: Lacal
authors: Françoise
authors: F
authors: Praz
authors: Grazia
authors: G
authors: Graziani
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D000071877:Checkpoint Kinase 1; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D006801:Humans; D000077146:Irinotecan; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D010766:Phosphorylation / Q000187:drug effects; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D059004:Topoisomerase I Inhibitors / Q000008:administration & dosage
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D000070957:MutL Protein Homolog 1; D002166:Camptothecin