title: Squamous cell carcinoma of the lung compared with other histotypes shows higher messenger RNA and protein levels for thymidylate synthase.
abstract: BACKGROUND
  In patients with cancer, one of the main mechanism of resistance to antimetabolite drugs is related to higher levels of thymidylate synthase (TS) activity.
  
  
  METHODS
  To investigate the association between TS expression and histopathologic data, 56 resection specimens from patients with nonsmall cell lung carcinoma (NSCLC) were collected consecutively. TS messenger RNA (mRNA) was evaluated in tumor specimens by using real-time polymerase chain reaction (PCR) analysis; protein expression was evaluated by using immunohistochemistry (IHC) in formalin-fixed, paraffin-embedded (FFPE) specimens; and the analysis of TS transcriptional regulation activity was performed by using real-time PCR analysis in snap-frozen normal and tumor specimens.
  
  
  RESULTS
  The amplification of the TS gene from FFPE tissues was obtained from all samples, with a median level (unit-less ratio) of 1.45 (range, 0.34-5.24); whereas positive TS status at IHC (>10% positive cells) was detected in 56% of samples. It is noteworthy that TS expression was significantly higher in squamous cell carcinoma compared with adenocarcinoma when both mRNA levels (2.17 vs. 1.16; P < .0001) and protein levels (P = .0269) were considered in FFPE specimens, and a strong association was observed between mRNA and protein expression (P = .00017). Moreover, higher TS levels were observed in high-grade tumors (P = .0389 and P = .0068 for mRNA and protein quantification, respectively). The analysis in snap-frozen samples revealed that the TS gene was up-regulated strongly in tumors (P = 3.8 x 10(-12)), and an 8-fold increase (as a cut-off value) in the TS mRNA ratio between tumor and corresponding normal tissue was detected in 32 of 56 patients (57%) bearing preferentially squamous cell tumors (P = .0022) and high-grade tumors (P < .001).
  
  
  CONCLUSIONS
  Data from the current study consistently indicated higher TS expression levels in squamous cell and in high-grade carcinomas. This information may be useful in selecting which patients with NSCLC should receive treatment with TS-inhibiting agents.
authors.affiliation: Thoracic Oncology Unit, Department of Clinical and Biological Sciences, University of Turin, San Luigi Hospital, Orbassano, Torino, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Ceppi
authors.forename: Marco
authors.initials: M
authors.lastname: Volante
authors.forename: Silvia
authors.initials: S
authors.lastname: Saviozzi
authors.forename: Ida
authors.initials: I
authors.lastname: Rapa
authors.forename: Silvia
authors.initials: S
authors.lastname: Novello
authors.forename: Alberto
authors.initials: A
authors.lastname: Cambieri
authors.forename: Marco
authors.initials: M
authors.lastname: Lo Iacono
authors.forename: Susanna
authors.initials: S
authors.lastname: Cappia
authors.forename: Mauro
authors.initials: M
authors.lastname: Papotti
authors.forename: Giorgio V
authors.initials: GV
authors.lastname: Scagliotti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis*; D013940:Thymidylate Synthase / Q000032:analysis* / Q000235:genetics; D015854:Up-Regulation
chemical_list: D012333:RNA, Messenger; D013940:Thymidylate Synthase