CpG Island Methylation Is Responsible for p14ARF Inactivation and Inversely Correlates with p53 Overexpression in Resected Non–Small Cell Lung Cancer

Abstract

Purpose and Experimental Design: The molecular mechanisms by which the p14ARF gene is altered in non-small cell lung cancer (NSCLC) are complex and unclear. Using genetic and epigenetic analyses, we examined various molecular alterations including the loss of protein and mRNA expression, and 5CpG hypermethylation, allelic imbalance, and mutation of the p14ARF gene in a series of 102 NSCLC samples, in parallel with clinicopathological and prognostic analyses. To clarify the biological significance of p14ARF alterations, its relationship with p16INK4a and p53 alterations was also examined.Results: We found that 34% of NSCLC patients had aberrant P14ARF protein expression, which was more frequent in adenocarcinomas (AD; 44%) than in squamous cell carcinomas (22%; P ‫؍‬ 0.024). A high concordance was observed between alterations in protein and mRNA expression and 5CpG hypermethylation (P < 0.001). The p14ARF hypermethylation inversely correlated with P53 overexpression (P ‫؍‬ 0.001). This mutually exclusive relationship for alteration between p14ARF and p53 was also supported by a worse prognosis of AD patients with positive P14ARF expression (P ‫؍‬ 0.01) and of AD patients with P53 overexpression (P ‫؍‬ 0.006). Our data also indicated that hemizygous/ homozygous deletion and mutation in the p14ARF gene occurred at 26%, 9%, and 0%, respectively, of microdissected NSCLCs.Conclusions: Our data suggest that p14ARF 5CpG hypermethylation is the predominant mechanism involved in the aberrant expression of the p14ARF gene. In addition, p14ARF 5CpG hypermethylation occurs inversely to P53 overexpression.

The role of NPM, p14arf and MDM2 in precursors of bronchial squamous cell carcinoma

“…MDM2 was initially overexpressed at the MiD stage in the current study, with 80% of the biopsies showing a high MDM2 expression, compared with only 19% of normal bronchial tissue. Previous studies have demonstrated a loss of p14arf expression in 18-50% of invasive SQCC [20,22,24]. However, no study has been published on p14arf expression in bronchial squamous cell pre-neoplastic lesions.…”

“…Indeed, MDM2 and p14arf have been widely studied in invasive lung cancer [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. However, limited data suggest that MDM2 expression is modified in the early stages of carcinogenesis [14], while p14arf has not been assessed in bronchial pre-invasive tissues.…”

Alteration of DNA methyltransferases contributes to 5′CpG methylation and poor prognosis in lung cancer

“…However, data concerning the frequency and mechanisms of overexpression of multiple DNMTs at the protein level have never been documented in the same series of cancer patients. We previously found that promoter hypermethylation plays an important role in the inactivation of certain TSGs including p16 INK4a , p14 ARF , hMLH1, hMSH2 and FHIT in non-small cell lung cancer (NSCLC) [21][22][23][24][25]. We proposed that dysregulation of DNA methylation machinery may lead to the promoter hypermethylation of TSGs we observed.…”

Correlation of p53, MDM2 and p14ARF protein expression in human esophageal squamous cell carcinoma

“…As described previously (Hsu et al 2004), the intensity of staining was evaluated semi-quantitatively and graded on a four point scale based on the percentage of immunostained cells. The levels were scored as follows: for p53 (0, <10%; 1, 11-25%; 2, 26-50%; 3, >50%) and for MDM2 and p14 ARF (0, <1%; 1, 1-10%; 2, 11-50%; 3, >50%).…”