title: Irinotecan changes gene expression in the small intestine of the rat with breast cancer.
abstract: OBJECTIVE
  The aetiology of mucositis is complex involving change in gene expression, altered apoptosis and interaction between epithelial and subepithelial compartments. This is the first investigation using microarray to assess chemotherapy-induced changes in the gut. The aims of this study were to identify genes that are altered by irinotecan, to determine how these genes contribute to apoptosis and to identify any potential gene families and pathways that are important for mucositis development.
  
  
  METHODS
  Tumour-bearing female dark Agouti rats were administered twice with 150 mg/kg of irinotecan and killed 6 h after the final dose. Jejunal tissue was harvested and RNA was isolated. cDNA was synthesised and purified, prior to hybridisation and microarray analysis. A 5-K oligo clone set was used to investigate gene expression. Results from the microarray were quantified using RT-PCR.
  
  
  RESULTS
  Many genes were significantly up- or down-regulated by irinotecan. In particular, multiple genes implicated in the mitogen-activated protein kinase (MAPK) signalling pathway were differentially regulated following treatment. These included interleukin 1 receptor, caspases, protein kinase C and dual-specificity phosphatase 6. RT-PCR was used to confirm effects of irinotecan on caspase-1 expression in jejunal tissue and was significantly increased 6 h after treatment with irinotecan.
  
  
  CONCLUSIONS
  This study has identified MAP kinase signalling as being involved with irinotecan-induced intestinal damage and confirms previous findings with radiation-induced oral mucosal damage, which also implicated this pathway. Microarrays are emerging as a valuable tool in mucositis research by linking such findings. The common pathway of chemotherapy- and radiotherapy-induced damage, which utilises the caspase-cascade, may be a useful target to prevent apoptosis following cancer treatment.
authors.affiliation: Department of Medical Oncology, Royal Adelaide Hospital, North Terrace, Adelaide, 5000, South Australia, Australia. joanne.bowen@adelaide.edu.au
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Bowen
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Gibson
authors.forename: Adrian G
authors.initials: AG
authors.lastname: Cummins
authors.forename: Anna
authors.initials: A
authors.lastname: Tyskin
authors.forename: Dorothy M K
authors.initials: DM
authors.lastname: Keefe
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D020170:Caspase 1 / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D000077146:Irinotecan; D007583:Jejunum / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D052016:Mucositis / Q000139:chemically induced / Q000235:genetics / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D012333:RNA, Messenger; D000077146:Irinotecan; D020929:Mitogen-Activated Protein Kinase Kinases; D020170:Caspase 1; D002166:Camptothecin