In patients with inoperable advanced
non-small cell lung carcinomas (NSCLCs), histological subtyping using small-mount biopsy specimens was often required to decide the indications for drug treatment. The aim of this study was to assess the utility of highly sensitive
mRNA quantitation for the subtyping of advanced NSCLC using small
formalin fixing and
paraffin embedding (FFPE) biopsy samples.
Cytokeratin (CK) 6, CK7, CK14, CK18, and thyroid
transcription factor (TTF)-1
mRNA expression levels were measured using semi-nested real-time quantitative (snq) reverse-transcribed polymerase chain reaction (RT-PCR) in microdissected
tumor cells collected from 52 lung biopsies. Our results using the present snqRT-PCR method showed an improvement in
mRNA quantitation from small FFPE samples, and the
mRNA expression level using snqRT-PCR was correlated with the immunohistochemical
protein expression level. CK7, CK18, and TTF-1
mRNA were expressed at significantly higher levels (P<0.05) in
adenocarcinoma (AD) than in
squamous cell carcinoma (SQ), while CK6 and CK14
mRNA expression was significantly higher (P<0.05) in SQ than in AD. Each histology-specific CK, particularly CK18 in AD and CK6 in SQ, were shown to be correlated with a poor prognosis (P=0.02, 0.02, respectively). Our results demonstrated that a quantitative CK subtype
mRNA analysis from lung biopsy samples can be useful for predicting the histology subtype and prognosis of advanced NSCLC.