Overexpression of E2F1 associated with LOH at RB locus and hyperphosphorylation of RB in non-small cell lung carcinoma.
OBJECTIVE
E2F1 plays a critical role in cell proliferation, and its function is controlled by the retinoblastoma (RB) protein. We examined the expression of E2F1 and the aberration of RB gene and protein to elucidate what factors contribute to the overexpression of E2F1 in non-small cell lung carcinomas.


METHODS
The expression level of E2F1 in tissues of non-small cell lung carcinomas was measured by means of quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. For RB, we examined loss of heterozygosity (LOH) by PCR-restriction fragment length polymorphism and a variable number of tandem repeats, and protein expression by immunohistochemistry.


RESULTS
Fifteen cases of carcinoma (46%) showed high transcription levels of E2F1 gene. Immunohistochemically, almost all (14 of 15) cases overexpressing E2F1 mRNA were positive for E2F1 protein. LOH at the RB locus was found in 13 of 30 informative cases. In 13 cases with LOH, ten showed overexpression of E2F1 mRNA and protein. Immunohistochemical positivity for phosphorylated RB protein was also closely correlated with overexpression of E2F1.


CONCLUSIONS
Our results suggest that overexpression of E2F1, induced both by LOH at the RB locus and anomalous phosphorylation of the RB protein, is involved in the development of non-small cell lung carcinoma.
Department of Health Science, Ishikawa Prefectural Nursing University, Kahoku-shi, Ishikawa, Japan.
Miwa Akasofu
MA
Imai
Yoshio
Y
Oda
Makoto
M
Oda
Isao
I
Nakanishi
Ei
E
Kawahara
D000230:Adenocarcinoma / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D019656:Loss of Heterozygosity; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018598:Minisatellite Repeats; D010766:Phosphorylation; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D014157:Transcription Factors