title: Phosphorylation of EGFR measured with in situ proximity ligation assay: relationship to EGFR protein level and gene dosage in cervical cancer.
abstract: OBJECTIVE
  We have applied the sensitive and specific in situ proximity ligation assay (PLA) to characterize Tyr1068 phosphorylation of the epidermal growth factor receptor (EGFR) in cervical cancer in relation to the protein level and gene dosage.
  
  
  METHODS
  Pretreatment tumor biopsies from 178 patients were analyzed. EGFR protein level was determined by immunohistochemistry, and Tyr1068 phosphorylation was detected with PLA in 97 EGFR positive tumors. EGFR gene dosage was derived from array comparative genomic hybridization of 86 cases.
  
  
  RESULTS
  EGFR was expressed in most tumors, whereas phosphorylation was seen in about half of the EGFR positive ones. A correlation was found between the expression of EGFR and phosphorylated EGFR (p=0.016, membrane; p=0.012, cytoplasm). However, tumor regions with high protein level without phosphorylation were occasionally seen and the percentage of EGFR positive cells was higher than the phosphorylated percentage (p<0.001). Moreover, an increase in the phosphorylation in both the membrane (p=0.014) and cytoplasm (p=0.002) was seen in 11 tumors with gain of EGFR. The protein level was not correlated with gene dosage.
  
  
  CONCLUSIONS
  In contrast to gain of the EGFR chromosomal region, high EGFR protein level may not necessarily indicate Tyr1068 phosphorylation and thereby receptor activation in cervical cancer.
authors.affiliation: Department of Radiation Biology, Oslo University Hospital, Norway.
authors.forename: Cathinka
authors.initials: C
authors.lastname: Halle
authors.forename: Malin
authors.initials: M
authors.lastname: Lando
authors.forename: Kolbein
authors.initials: K
authors.lastname: Sundfør
authors.forename: Gunnar B
authors.initials: GB
authors.lastname: Kristensen
authors.forename: Ruth
authors.initials: R
authors.lastname: Holm
authors.forename: Heidi
authors.initials: H
authors.lastname: Lyng
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001707:Biopsy, Needle; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D002462:Cell Membrane / Q000378:metabolism; D015331:Cohort Studies; D003593:Cytoplasm / Q000378:metabolism; D066246:ErbB Receptors / Q000032:analysis / Q000378:metabolism*; D005260:Female; D018628:Gene Dosage; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization / Q000379:methods; D020287:In Situ Nick-End Labeling; D008875:Middle Aged; D010766:Phosphorylation; D018709:Statistics, Nonparametric; D014448:Tyrosine-tRNA Ligase / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology
chemical_list: C512478:EGFR protein, human; D066246:ErbB Receptors; D014448:Tyrosine-tRNA Ligase