PubMed · 7943645
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V A LiVolsi. 1994. Keratoacanthomas.. https://doi.org/10.1097/00000372-199406000-00020
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We previously reported a novel association between CDKN2A nonpromoter methylation and transcription (ARF/INK4a) in human papillomavirus associated oropharyngeal tumors. In this study we assessed whether nonpromoter CDKN2A methylation in laryngeal squamous cell carcinomas (LXSCC) conferred a similar association with transcription that predicted patient outcome. We compared DNA methylation and ARF/INK4a RNA expression levels for the CDKN2A locus using the Illumina HumanMethylation27 beadchip and RT-PCR in 43 LXSCC tumor samples collected from a prospective study of head and neck cancer patients treated at Montefiore Medical Center (MMC). Validation was performed using RNAseq data on 111 LXSCC tumor samples from the Cancer Genome Atlas (TCGA). The clinical relevance of combined nonpromoter CDKN2A methylation and transcription was assessed by multivariate Cox regression for locoregional recurrence on a subset of 69 LXSCC patients with complete clinicopathologic data from the MMC and TCGA cohorts. We found evidence of CDKN2A nonpromoter hypermethylation in a third of LXSCC from our MMC cohort, which was significantly associated with increased ARF and INK4a RNA expression (Wilcoxon rank-sum, P = 0.007 and 0.003, respectively). A similar association was confirmed in TCGA samples (Wilcoxon rank-sum test P < 0.0001 for ARF and INK4a). Patients with CDKN2A hypermethylation or high ARF/INK4a expression were significantly less likely to develop a locoregional recurrence compared to those with neither of the features, independent of other clinicopatholgic risk factors (adjusted hazard ratio=0.21, 95% confidence interval:0.05-0.81). These results support the conclusion that CDKN2A nonpromoter methylation is associated with increased ARF and INK4a RNA expression, and improved locoregional control in LXSCC.
Individuals with specific phase I and phase II enzyme polymorphisms may be at increased risk for squamous cell carcinoma of the esophagus. However, to our knowledge there has been only one previous report that evaluates a potential role for these polymorphisms in increasing risk for preneoplastic squamous lesions of the esophagus. To explore this further, we examined polymorphisms in CYP1A1, CYP2E1, GSTM1 and GSTT1, both independently and in combination, for potential associations with the risk of biopsy-proven squamous dysplasia of the esophagus in asymptomatic adults from Linxian, a high risk region in China. Cases consisted of 56 individuals from an esophageal cancer screening study with an endoscopic biopsy diagnosis of mild or moderate squamous dysplasia. Each case was matched on age (+/- 1 year) and gender to a control. Controls were defined as screening study participants with an endoscopic biopsy diagnosis of normal mucosa or esophagitis. DNA was extracted from frozen cell samples obtained by cytologic balloon examination and genotyped using standard methods. Individuals who were GSTM1 null (homozygous for GSTM1*0) were found to have a tendency for an increased risk of esophageal squamous dysplasia (odds ratio=2.6, 95% CI, 0.9-7.4). No excess risks were observed for inheritance of other putative at risk genotypes CYP1A1*2B, CYP2E1*6 or GSTT1*0. The risk associated with the inheritance of combined genotypes was not significantly different than the risk estimates from the univariate analysis. These results are consistent with the notion that exposure to environmental carcinogens that are detoxified by GSTM1, such as polycyclic aromatic hydrocarbons, may contribute to the etiology of esophageal cancer in Linxian.
Loss of heterozygosity (LOH) on 18q predicts poor survival in head and neck squamous cell carcinomas (HNSCCs). Several putative tumor suppressor genes, such as DCC, DPC4/Smad4, and MADR2/Smad2, are mapped to 18q, but thus far, the important gene locus in HNSCC is not known. To identify possible gene loci on 18q, we performed LOH studies using tumor DNA from 57 HNSCC primary tumor cell lines and DNA isolated from fibroblasts or lymphoblastoid cells from the same patients. Forty-two highly polymorphic microsatellite markers spaced not more than 5 cM apart (mean distance, 1.82 cM) spanning the region from D18S44 in 18q11.1 to D18S1141 in 18q23 were used. D18S71 in 18p11.21 on 18p was also used to determine whether the short arm was retained. Forty-three of 57 (75%) HNSCC lines showed LOH or isolated allelic imbalance (AI) for at least one locus on 18q. Although many of the cell lines had large distal 18q deletions with a breakpoint between 18q11.1 and 18q12.2 to qter, three loci were identified that were lost in 70% or more of the cases. The minimally lost regions (MLRs) range in size from 1.5-15.79 cM. The most proximal is centered on D18S39 (1.56 cM) in band 18q21.1, with LOH or isolated AI in 28 of 38 (74%) of informative cases. The largest (15.8 cM) begins at D18S61 (28 of 40; 70%) in band 18q22.2 and extends through D18S50 in 18q23. The third is centered on D18S70 (30 of 40; 75%) in band 18q23 (3.67 cM). Of these MLRs, only the one centered on D18S39 has been implicated previously in HNSCC. D18S70, the most frequently lost marker, was the only marker consistently lost in three tumor cell lines with very minimal losses, UM-SCC-19, UM-SCC-67, and UM-SCC-73A. In addition, UM-SCC-91 exhibited AI only at this locus, and UT-SCC-4 had AI at D18S70 and D18S39 only. Close physical mapping of these three regions may pinpoint one or more previously unidentified tumor suppressor genes.