UHRF1-mediated tumor suppressor gene inactivation in nonsmall cell lung cancer.

Background: The UHRF1 gene possesses an essential role in DNA methylation maintenance, but its contribution to tumor suppressor gene hypermethylation in primary human cancers currently remains unclear.

Methods: mRNA expression levels of UHRF1, DNMT1, DNMT3A, DNMT3B, and E2F1 were evaluated in 105 primary nonsmall cell lung carcinomas by quantitative polymerase chain reaction. The methylation status of CDKN2A and RASSF1 promoters was examined by pyrosequencing.

Global DNA hypomethylation-induced ΔNp73 transcriptional activation in non-small cell lung cancer.

p73 possesses an extrinsic P1 promoter and an intrinsic P2 promoter controlling the expression of the pro-apoptotic TAp73 isoforms and the anti-apoptotic ΔΝp73 isoforms respectively. In this study, we investigated the DNA methylation status of both promoters as a means of epigenetic transcriptional control of their corresponding isoforms in 102 primary non-small cell lung carcinomas (NSCLCs). We demonstrated that while P1 hypermethylation-associated reduction of TAp73 mRNA levels is relatively infrequent, the P2 hypomethylation-associated over-expression of ΔΝp73 mRNA is a frequent event, particularly among squamous cell carcinomas.

Sp1 binds to the external promoter of the p73 gene and induces the expression of TAp73gamma in lung cancer.

The p73 gene possesses an extrinsic P1 promoter and an intrinsic P2 promoter, resulting in TAp73 and DeltaNup73 isoforms, respectively. The ultimate effect of p73 in oncogenesis is thought to depend on the apoptotic TA to antiapoptotic DeltaN isoforms' ratio. This study was aimed at identifying novel transcription factors that affect TA isoform synthesis.

Hypomethylation of retrotransposable elements correlates with genomic instability in non-small cell lung cancer.

LINE-1 and Alu elements are non-LTR retrotransposons, constituting together over 30% of the human genome and they are frequently hypomethylated in human tumors. A relationship between global hypomethylation and genomic instability has been shown, however, there is little evidence to suggest active role for hypomethylation-mediated reactivation of retroelements in human cancer. In our study, we examined by Pyrosequencing the methylation levels of LINE-1 and Alu sequences in 48 primary nonsmall cell carcinomas and their paired adjacent tissues.