Transcriptional upregulation and unmethylation of the promoter region of p16 in invasive basal cell carcinoma cells and partial co-localization with the gamma 2 chain of laminin-332.
Basal cell carcinoma cells show low proliferation rates at the invasive front and a concordant upregulation of the cdk-inhibitor p16, limiting proliferative capacity. Little is known about the mechanisms of p16 regulation in normal and malignant cells apart from that many transcription factors such as Ets1, Ets2, SP1, SP3, JunB and the polycomb protein Bmi1 have the potential to induce or repress p16 expression. Therefore, the aim of this study was to determine how p16 is regulated in basal cell carcinoma with special focus on its upregulation in invasive cells. By analysing various microdissected areas of basal cell carcinoma using real-time quantitative PCR we observed upregulation of p16 mRNA in invasive tumour cells compared to centrally localized tumour cells. The methylation status of the p16 promoter, analysed by methylation-specific PCR, also showed diminished methylation in tumour cells at the invasive front, supporting the hypothesis that promoter methylation can affect the transcriptional activation of p16 in vivo. There was only sporadic co-localization of Ets, or ERK1/2 phosphorylation with p16 upregulation at the invasive front, suggesting that these factors were not directly involved in the regulation of p16. Furthermore, the gamma 2 chain of laminin-332 has been reported to be increased at the invasive front compared to the central areas of many tumours. Interestingly, in basal cell carcinoma we observed partial co-localization between p16 and the gamma 2 chain of laminin-332 in tumour cells towards areas of ulceration and in the majority of clearly infiltrative tumour cells but not in p16 positive tumour cells with a more pushing invasive growth pattern. These data suggest that concurrent p16 upregulation and decreased proliferation are more general phenomena in different types of invasive growth patterns in basal cell carcinomas and that these only partially overlap with the gamma 2 chain of laminin-332 associated invasion patterns.
Svensson Månsson
S
S
Division of Pathology, Department of Laboratory Medicine, Lund University, UMAS, SE-205 02 Malmö, Sweden.
Reis-Filho
J
J
Landberg
G
G
D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D002280:Basal Cell Carcinoma / Q000235:genetics* / Q000473:pathology; D015815:Cell Adhesion Molecules / Q000032:analysis; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D019175:DNA Methylation; D015972:Gene Expression Regulation, Neoplastic; D019942:Genes, p16; D006801:Humans; D007150:Immunohistochemistry; D007797:Laminin / Q000032:analysis*; D009361:Neoplasm Invasiveness; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D000097794:Kalinin
D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D019941:Cyclin-Dependent Kinase Inhibitor p16; D007797:Laminin; D012333:RNA, Messenger; D000097794:Kalinin