Distinct pattern of E2F1 expression in human lung tumours: E2F1 is upregulated in small cell lung carcinoma.
The transcription factor E2F1 is a key component of cell cycle that acts to transactivate genes required for S phase entry. Thus, it plays an important role in cellular proliferation, oncogenesis and differentiation. In order to investigate its potential implication in human lung carcinogenesis, we studied E2F1 protein expression by Western blotting and immunohistochemistry in a series of 58 human lung tumours of all histological types. We showed that E2F1 product was overexpressed in 92% (24/26) of small cell lung carcinoma (SCLC) and in 50% (5/10) of large cell neuroendocrine carcinoma (LCNEC) whereas it was undetectable in 90% (10/11) of adenocarcinoma and 82% (9/11) of squamous carcinoma when compared to corresponding normal lung. No amplification was found but an increase in E2F1 mRNA expression was detected in 75% (18/24) of SCLC overexpressing E2F1 product. In these tumours and in contrast with NSCLC, upregulation of E2F1 product was associated with its nuclear accumulation and with overexpression of several of its target-genes. Moreover, E2F1 overexpression in NE lung tumours was significantly associated with a high KI67 index (P<0.0001) as well as a Bcl-2:Bax ratio >1 (P<0.001). Overall, these results demonstrate a distinct pattern of E2F1 expression in human lung tumours and suggest that its deregulation could be involved in the carcinogenesis of SCLC.
Eymin
B
B
Groupe de Recherche sur le Cancer du Poumon, EA 2021, Equipe INSERM 9924, Institut Albert Bonniot, 38706 La Tronche Cedex, France.
Gazzeri
S
S
Brambilla
C
C
Brambilla
E
E
D018288:Carcinoma, Small Cell / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D016160:Retinoblastoma Protein / Q000032:analysis; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein