Moreover, the reverse correlation between p16INK4a immunostaining and p16INK4a promoter hypermethylation was also only observed in nonsmoking female lung tumors.
Secondly, genetic resistance to lung tumor formation appears to segregate with one particular haplotype, which also is deleted preferentially in lung adenocarcinomas of Cdkn2a heterozygous mice.
Western blot analysis showed that stromal cells of lung tumours were characterised by a statistically significantly lower expression level of the p16 protein as compared with that in normal lung stromal cells.
In multivariate analysis, p16 hypermethylation was more prevalent in lung tumours from male than female patients (P = 0.018) and in squamous cell carcinomas than in adenocarcinomas (P = 0.025).
The formation of lung tumors by these chemicals involved mutations in the K-ras cancer gene and loss of heterozygosity in the region of K-ras on distal chromosome 6, while alterations in p53 and p16 were implicated in brain tumorigenesis.
The p14ARF transcript, which is an alternative spliced form of this locus, is also altered or deleted in a proportion of human lung cancers and has been shown to inhibit cell cycle progression as an endogenous cellular regulator of the p53 protein, raising the possibility that it might constitute an additional lung tumor suppressor gene at the 9p21 locus.
In order to explore the possibility of a selective deregulation of p15(INK4b) in human lung carcinogenesis, we studied p15(INK4b) status in neuroendocrine (NE) lung tumours where homozygous deletions of the p16(INK4a)/p14(ARF) locus are rarely observed.
To further explore the molecular mechanisms between altered TSGs promoter methylation and overexpression of DNMTs protein, we performed a tissue chromatin-immunoprecipitation polymerase chain reaction assay for lung tumors and showed that the methylated FHIT, p16(INK4a) and RARbeta promoters were bound by both DNMT protein and methyl-CpG-binding protein 2.
Here, we applied methylation-specific polymerase chain reaction to compare the frequencies of the methylated promoter of p16 and O6-methylguanine-DNA methyltransferase (MGMT) genes in lung tumors from 122 patients with non-small cell lung cancer, including 81 smokers and 41 never-smokers.
To conclude, systemic p16 peptide administration decreased lung tumor development in a mouse metastatic BT model without severe adverse events, as assessed by blood analyses and histological evaluation.
Our analyses revealed a high frequency of aberrant hypermethylation of MTHFR, RASSF1A, and CDKN2A in lung tumors as compared with control blood samples, whereas no significant increase in methylation levels of GSTP1 and CDH1 was observed, consistent with the notion that aberrant DNA methylation occurs in a tumor-specific and gene-specific manner.
Moreover, and consistent with p14ARF being a determinant of CHK2 phosphorylation in lung carcinogenesis, a strong correlation between p14ARF and phospho-CHK2 (Thr68) protein expression is observed in human lung tumors (P < 0.00006).
<b>Patients & methods:</b> Lung tumor tissue microarray (n = 163), immunohistochemical study of p16 and p53, and HPV <i>in-situ</i> hybridization were analyzed.
The Contrasting Role of p16Ink4A Patterns of Expression in Neuroendocrine and Non-Neuroendocrine Lung Tumors: A Comprehensive Analysis with Clinicopathologic and Molecular Correlations.
We examined the tumor and the matched BAL DNA for aberrant methylation of eight gene promoters (CDH1, APC, MGMT, RASSF1A, GSTP1, p16, RAR-beta 2, and ARF) from 31 patients with primary lung tumors by quantitative fluorogenic real-time PCR.
Methylation of the p16 and ER genes was very common (80 and 50%, respectively) in beryllium-induced lung tumors; both genes were methylated in 40% of the tumors.
These results substantiate the primary tumor as the origin for dysfunction of the p16 gene and implicate CpG island methylation as the major mechanism for inactivating this gene in the rat lung tumors examined.
H1299 lung cancer cells, lacking Fhit, Wwox, p16(INK4a) and Rassf1a expression due to epigenetic modifications, were used to assess efficacy of epigenetically targeted protocols in suppressing growth of lung tumors, by injection of 5-aza-2-deoxycytidine (AZA) and trichostatin A (TSA) in nude mice with established H1299 tumors.
Moreover, 36.7% (22/60) of the non-small cell lung tumours without p16 expression showed p16 promoter methylation, detecting a significant correlation between p16 methylation and the histological subtype of squamous cell carcinomas (SCC) (P=0.04).
Based on the concordance of biomarkers in lung tumours and corresponding sputum, and the low prevalence in cancer-free individuals, we selected seven markers for a nested case-control study: microsatellite instability of D9S942; loss of heterozygosity of D9S286, D9S942, GATA49D12, and D13S170; and methylation of p16INK4a and RARbeta.