Overexpression of the replication licensing regulators hCdt1 and hCdc6 characterizes a subset of non-small-cell lung carcinomas: synergistic effect with mutant p53 on tumor growth and chromosomal instability--evidence of E2F-1 transcriptional control over hCdt1.
Replication licensing ensures once per cell cycle replication and is essential for genome stability. Overexpression of two key licensing factors, Cdc6 and Cdt1, leads to overreplication and chromosomal instability (CIN) in lower eukaryotes and recently in human cell lines. In this report, we analyzed hCdt1, hCdc6, and hGeminin, the hCdt1 inhibitor expression, in a series of non-small-cell lung carcinomas, and investigated for putative relations with G(1)/S phase regulators, tumor kinetics, and ploidy. This is the first study of these fundamental licensing elements in primary human lung carcinomas. We herein demonstrate elevated levels (more than fourfold) of hCdt1 and hCdc6 in 43% and 50% of neoplasms, respectively, whereas aberrant expression of hGeminin was observed in 49% of cases (underexpression, 12%; overexpression, 37%). hCdt1 expression positively correlated with hCdc6 and E2F-1 levels (P = 0.001 and P = 0.048, respectively). Supportive of the observed link between E2F-1 and hCdt1, we provide evidence that E2F-1 up-regulates the hCdt1 promoter in cultured mammalian cells. Interestingly, hGeminin overexpression was statistically related to increased hCdt1 levels (P = 0.025). Regarding the kinetic and ploidy status of hCdt1- and/or hCdc6-overexpressing tumors, p53-mutant cases exhibited significantly increased tumor growth values (Growth Index; GI) and aneuploidy/CIN compared to those bearing intact p53 (P = 0.008 for GI, P = 0.001 for CIN). The significance of these results was underscored by the fact that the latter parameters were independent of p53 within the hCdt1-hCdc6 normally expressing cases. Cumulatively, the above suggest a synergistic effect between hCdt1-hCdc6 overexpression and mutant-p53 over tumor growth and CIN in non-small-cell lung carcinomas.
Department of Histology and Embryology, Molecular Carcinogenesis Group, School of Medicine, Univerity of Athens, Greece.
Panagiotis
P
Karakaidos
Stavros
S
Taraviras
Leandros V
LV
Vassiliou
Panayotis
P
Zacharatos
Nikolaos G
NG
Kastrinakis
Dionysia
D
Kougiou
Mirsini
M
Kouloukoussa
Hideo
H
Nishitani
Athanasios G
AG
Papavassiliou
Zoi
Z
Lygerou
Vassilis G
VG
Gorgoulis
D000368:Aged; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D064200:Cdh1 Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005455:Fluorescent Antibody Technique; D064248:Geminin; D006801:Humans; D020287:In Situ Nick-End Labeling; D019656:Loss of Heterozygosity; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008875:Middle Aged; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins; D011003:Ploidies; D018807:Polymorphism, Single-Stranded Conformational; D011379:Prognosis; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000096:biosynthesis; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; C577584:FZR1 protein, human; C577585:Fzr1 protein, mouse; C577995:GMNN protein, human; D064248:Geminin; C577997:Gmnn protein, mouse; D009687:Nuclear Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53