title: Hyperthermia effects on Hsp27 and Hsp72 associations with mismatch repair (MMR) proteins and cisplatin toxicity in MMR-deficient/proficient colon cancer cell lines.
abstract: OBJECTIVE
  Hyperthermia is used in combination with conventional anticancer agents to potentiate their cytotoxicity. One of its key events is the synthesis of heat shock proteins (HSPs), which are able to associate with components from DNA repair mechanisms. However, little is known about their relationship with the mismatch repair system (MMR). Our aim was to study the effects of hyperthermia on cisplatin (cPt) sensitivity and to determine whether MLH1 and MSH2 associate with Hsp27 and Hsp72 in MMR-deficient(-)/-proficient(+) cells.
  
  
  METHODS
  HCT116+ch2 (MMR-) and HCT116+ch3 (MMR+) cell lines were exposed to cPt with or without previous hyperthermia (42 °C, 1 h). Clonogenic survival assays, MTT, confocal immunofluorescence, immunoprecipitation, immunoblotting and flow cytometry were performed.
  
  
  RESULTS
  Hyperthermia increased the cPt resistance in MMR- cells 1.42-fold. Immunofluorescence revealed that after cPt, Hsp27 and Hsp72 translocated to the nucleus and colocalisation coefficients between these proteins with MLH1 and MSH2 increased in MMR+ cells. Immunoprecipitation confirmed the interactions between HSPs and MMR proteins in control and treated cells. Hyperthermia pretreatment induced cell cycle arrest, increased p73 expression and potentiated cPt sensitivity in MMR+ cells.
  
  
  CONCLUSIONS
  This is the first report showing in a MMR-/+ cellular model that MLH1 and MSH2 are client proteins of Hsp27 and Hsp72. Our study suggests that p73 might participate in the cellular response to hyperthermia and cPt in a MMR-dependent manner. Further functional studies will confirm whether HSPs cooperate with the MMR system in cPt-induced DNA damage response or whether these protein interactions are only the result of their chaperone functions.
authors.affiliation: Tumour Biology Laboratory, Institute of Medicine and Experimental Biology of Cuyo, National Scientific and Technical Research Council , Mendoza .
authors.forename: Mayra L
authors.initials: ML
authors.lastname: Sottile
authors.forename: Antonella D
authors.initials: AD
authors.lastname: Losinno
authors.forename: Mariel A
authors.initials: MA
authors.lastname: Fanelli
authors.forename: F Darío
authors.initials: FD
authors.lastname: Cuello-Carrión
authors.forename: M Magdalena
authors.initials: MM
authors.lastname: Montt-Guevara
authors.forename: Laura M
authors.initials: LM
authors.lastname: Vargas-Roig
authors.forename: Silvina B
authors.initials: SB
authors.lastname: Nadin
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000009:adverse effects* / Q000633:toxicity; D003110:Colonic Neoplasms / Q000188:drug therapy*; D004249:DNA Damage / Q000235:genetics*; D053843:DNA Mismatch Repair / Q000235:genetics*; D005334:Fever / Q000235:genetics*; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans
chemical_list: D000970:Antineoplastic Agents; D055551:HSP27 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; D002945:Cisplatin
keywords: Chaperones; DNA damage/repair; HT radio-chemosensitization; heat shock response; thermotolerance