title: Genome-wide transcriptomic profiling of microdissected human breast tissue reveals differential expression of KIT (c-Kit, CD117) and oestrogen receptor-alpha (ERalpha) in response to therapeutic radiation.
abstract: The pathogenesis of late normal tissue fibrosis after high-dose ionizing radiation involves multiple cell types and signalling pathways but is not well understood. To identify the molecular changes occurring after radiotherapy, paired normal tissue samples were collected from the non-irradiated breast and from the treated breast of women who had undergone curative radiotherapy for early breast cancer months or years previously. As radiation may induce distinct transcriptional changes in the different components of the breast, laser capture microdissection and gene expression microarray profiling were performed separately for epithelial and stromal components and selected genes were validated using immunohistochemistry. In the epithelial compartment, a reduction of KIT (c-Kit; CD117) and a reciprocal increase in ESR1 (oestrogen receptor-alpha, ERalpha) mRNA and protein levels were seen in irradiated compared to non-irradiated samples. In the stromal compartment, extracellular matrix genes including FN1 (fibronectin 1) and CTGF (connective tissue growth factor; CCN2) were increased. Further investigation revealed that c-Kit and ERalpha were expressed in distinct subpopulations of luminal epithelial cells. Interlobular c-Kit-positive mast cells were also increased in irradiated cases not showing features of post-radiation atrophy. Pathway analysis revealed 'cancer, reproductive system disease and tumour morphology' as the most significantly enriched network in the epithelial compartment, whereas in the stromal component, a significant enrichment for 'connective tissue disorders, dermatological diseases and conditions, genetic disorder' and 'cancer, tumour morphology, infection mechanism' networks was observed. These data identify previously unreported changes in the epithelial compartment and show altered expression of genes implicated in late normal tissue injury in the stromal compartment of normal breast tissue. The findings are relevant to both fibrosis and atrophy occurring after radiotherapy for early breast cancer.
authors: Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors: Charlotte B
authors: CB
authors: Westbury
authors: Jorge S
authors: JS
authors: Reis-Filho
authors: Tim
authors: T
authors: Dexter
authors: Betania
authors: B
authors: Mahler-Araujo
authors: Kerry
authors: K
authors: Fenwick
authors: Marjan
authors: M
authors: Iravani
authors: Anita
authors: A
authors: Grigoriadis
authors: Suzanne
authors: S
authors: Parry
authors: David
authors: D
authors: Robertson
authors: Alan
authors: A
authors: Mackay
authors: Alan
authors: A
authors: Ashworth
authors: John R
authors: JR
authors: Yarnold
authors: Clare M
authors: CM
authors: Isacke
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000378:metabolism / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy*; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D047628:Estrogen Receptor alpha / Q000032:analysis / Q000235:genetics*; D005260:Female; D005355:Fibrosis; D015870:Gene Expression; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects*; D055106:Genome-Wide Association Study / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry; D042282:Microdissection; D018613:Microscopy, Confocal; D008875:Middle Aged; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis / Q000235:genetics*; D018709:Statistics, Nonparametric; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects
chemical_list: D047628:Estrogen Receptor alpha; D019009:Proto-Oncogene Proteins c-kit