Polymerase chain reaction amplification and direct sequencing of p16 exons 1 and 2 revealed no mutations, indicating that p16-altered expression in lung cancer is not necessarily linked to mutational events of these genes.
These results provide the first link between germ-line functional deficits in pathways that protect the cell from tobacco- and radon-induced DNA damage, and the development of aberrant promoter methylation of the p16 and MGMT genes in the respiratory epithelium of individuals at high risk for lung cancer.
In contrast, cancer cell lines which were wild-type for p16 but mutant or null for pRb (Saos-2, C33a and H358) were <threefold more sensitive to Adp16 when compared to a control virus.
To compare the degree of cellular senescence among COPD, IPF, and CTD-ILD, tissue samples from surgical lung biopsies or noncancerous tissue from lobectomy specimens of patients with lung cancer were subjected to immunostaining for p16 and p21.
In contrast, p16 expression was lost in moderate dysplasia (12%) and in CIS (30%) in patients with lung cancer. p16 loss occurred exclusively in patients who displayed loss of p16 expression in their related invasive carcinoma.
All of these findings are consistent with loss of Fhit protein expression being as frequent an abnormality in lung cancer pathogenesis as are p53 and p16 protein abnormalities and that such loss occurs independently of the commitment to the metastatic state and of most other molecular abnormalities.
Our data show that a combination of cytological analysis of sputum and examination of p16 hypermethylation in sputum and plasma identified 92.0% (46/50) of the lung cancer patients studied, offering an effective means of early detection of lung cancer.
Furthermore, the inactivation of the p16 gene by these carcinogenic exposures supports a possible role for oxidative stress and inflammation in the etiology of human lung cancer.
Knockdown of DeltaDNMT3B4 expression by small interfering RNA resulted in a rapid demethylation of RASSF1A promoter and reexpression of RASSF1A mRNA but had no effect on p16 promoter in the lung cancer cells.
Evaluation of p16 and ESR1 promoter methylation in blood using real-time PCR appears to be very useful for lung cancer diagnosis and there is some possibility that these methylated genes might come to represent useful biomarkers for the early detection of lung cancer.
Since somatic mutations of the p53, RB and p16 genes occur frequently in lung cancer and the replication error phenotype is seen in a subset of lung cancer, it is possible that germ-line mutations of the p53, RB, p16 and mismatch repair genes influence the susceptibility to lung cancer.
Positive rates of MAGE A1-A6 RT-PCR, MAGE A3 MSP and p16 MSP were as follows: in lung cancer tissue, 87.5, 58.3 and 70.8%; in the sputum of lung cancer patients, 50.8, 46.2 and 63.1%; benign lung diseases, 10.3, 30.9 and 39.7%; and healthy individuals, 3.3, 6.7 and 3.3%.
Multiple logistic regression analysis showed that the odds ratio for having lung cancer was 10.204 for individuals with p16 methylation (P = .013) and 9.952 for individuals with RASSFIA methylation (P = .019).
Furthermore, the p16 gene was affected by promoter methylation at a frequency even higher among the lung cancer group, compared with the noncancer group [70.7% (41/58) versus 51.7% (55/107), p = 0.017].
Both copies of the candidate tumor suppressor gene on chromosome 9, CDKN2, are deleted in approximately one-fourth of lung cancer cell lines examined and the protein product of CDKN2, p16 is undetectable in one-third of the lung cancer cell lines studied.