title: Cell cycle regulators in testicular cancer: loss of p18INK4C marks progression from carcinoma in situ to invasive germ cell tumours.
abstract: Cell cycle regulators govern cellular proliferation, modulate differentiation and, when defective, contribute to oncogenesis. Here, we examined expression of cyclins A, B1 and E, and cyclin-dependent kinase (CDK) inhibitors p18INK4C (p18), p21WAF1/Cip1 (p21) and p27KiP1 (p27), in normal human adult testis (n = 5), and 53 testicular tumours, including 23 carcinomas in situ (CIS) and 30 germ cell tumours (GCTs). Immunohistochemical analysis revealed a correlation between proliferation and abundance of the cyclin proteins, and abundant p18 and the lack of p21 and p27 in normal spermatogenesis. Expression of p21 and/or p27 was induced in some differentiated structures seen in teratomas, and was recapitulated in cell culture, using human NTera2/D1 teratocarcinoma cells induced to differentiate into neurons. CIS lesions showed abundant p18, low cyclin E, and moderate p27, in contrast with most invasive seminomas and embryonal carcinomas with very low-to-negative p18, often elevated cyclin E, and, unexpectedly, sustained or increased p27. Our results suggest increased abundance of cyclin E, and particularly downmodulation or loss of p18INK4C as the features that correlate with progression from CIS to invasive germ cell tumours of the human testis.
authors.affiliation: Department of Cell Cycle and Cancer, Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Bartkova
authors.forename: M
authors.initials: M
authors.lastname: Thullberg
authors.forename: E
authors.initials: E
authors.lastname: Rajpert-De Meyts
authors.forename: N E
authors.initials: NE
authors.lastname: Skakkebaek
authors.forename: J
authors.initials: J
authors.lastname: Bartek
mesh_terms: D000328:Adult; D002278:Carcinoma in Situ / Q000201:enzymology / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000378:metabolism*; D018450:Disease Progression; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000378:metabolism*; D018237:Germinoma / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D015151:Immunoblotting; D008163:Luminescent Measurements; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D018243:Teratocarcinoma / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D013736:Testicular Neoplasms / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
chemical_list: C493956:CDKN1A protein, human; C493971:CDKN2C protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050763:Cyclin-Dependent Kinase Inhibitor p18; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases