Ethanol decreases negative cell-cycle-regulating proteins in a head and neck squamous cell carcinoma cell line

INK4 Family -A promising target for 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer

Inactivation of the p16(INK4a) gene is one of the most frequent defects that contribute to oncogenesis in human cancer, since it is a tumor-suppressor gene. Therefore, functional restoration of p16(INK4a) is one of the most effective methods for cancer prevention. We proposed the concept of 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer, which assumes that transcriptional regulation by drugs on tumor-suppressor genes or functionally similar genes to the tumor-suppressor genes contributes to the prevention of human malignancies. The p16(INK4a) homologs p15(INK4b), p18(INK4c) and p19(INK4d) have been recently identified, and these four members constitute the INK4 family of proteins. All directly bind to cyclin D-cyclin dependent kinase (CDK) 4/6 and are therefore specific inhibitors of these complexes. We recently showed that histone deacetylase (HDAC) inhibitors, promising chemopreventive and chemotherapeutical agents, induce p15(INK4b) and p19(INK4d) gene expression and cause growth arrest, suggesting that both genes are important molecular targets for HDAC inhibitors. Furthermore, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA), which is widely used as a tumor promoter and protein kinase C activator, promotes human cancer cell growth through the down-regulation of p18(INK4c) gene expression. This suggests that a mouse two-stage carcinogenesis model using TPA might partially represent the most common human carcinogenesis pathway related to RB. Our results suggest that the INK4 family consists of attractive and promising molecular targets for the 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer.

Association of p73 G4C14-to-A4T14 polymorphism with human papillomavirus type 16 status in squamous cell carcinoma of the head and neck in non-Hispanic whites

BACKGROUND

The tumor protein p73 interacts with the human papillomavirus type 16 (HPV-16) oncoproteins E6 and E7, and p73 variation may modify the interaction between p73 protein and HPV-16 oncogenic proteins and contribute to cellular malignant transformation.

METHODS

In this case-case comparison study, the authors analyzed HPV-16 status in tumor specimens and genotyped the p73 G4C14-to-A4T14 polymorphism using genomic DNA from blood of 202 non-Hispanic white patients with squamous cell carcinoma of the head and neck (SCCHN). Odds ratio (OR) and 95% confidence intervals (95% CIs) were calculated in univariate and multivariable logistic regression models to examine the association between the p73 polymorphism and HPV-16 status in SCCHN.

RESULTS

Compared with the p73 GC/GC genotype, the AT/AT and combined GC/AT + AT/AT variant genotypes were associated significantly with HPV-16-positive tumor status among patients with SCCHN (adjusted OR, 5.32; 95% CI, 1.32-21.4; adjusted OR, 1.91; 95% CI, 1.03-3.53, respectively). There was a significant dose-effect relation between the AT allele and HPV-16-positive tumor status in patients with SCCHN (trend test: P = .014). Moreover, the stratified analyses indicated that the association between HPV-16-positive tumor status and the combined p73 GC/AT + AT/AT genotypes was more pronounced among several subgroups of patients who were older, men, ever drinkers, and those with oropharyngeal cancer.

CONCLUSIONS

The p73 polymorphism was associated with HPV-16 status in SCCHN and may serve as a marker of positive HPV-16 tumor status in patients with SCCHN, particularly those with oropharyngeal cancer.

Discrimination of epithelium-like and fibroblast-like phenotypes derived from ethanol-treated immortalised human gingival keratinocytes in epithelial equivalents

Ethanol treatment of immortalised human gingival keratinocytes (IHGK) yields in an epithelium-like (EPI) and fibroblast-like (FIB) phenotype. With respect to the stratified gingival epithelium, putative structural and molecular differences assigning cells to these phenotypes have not, to date, been analysed in a three-dimensional tissue/epithelial context. Therefore, we generated epithelial equivalents (EEs) in organotypic co-cultures of IHGK, EPI and FIB cells for 1 and 2 weeks and conducted protein and gene expression studies on the EEs for epithelial biomarkers including keratin K14, integrin subunits alpha6 and beta1, E-cadherin, and mesenchymal vimentin. As in the EEs of IHGK and EPI, indirect immunofluorescence revealed continuous expression of beta1 integrin in EEs of FIB cells. However, FIB cells exhibited a significant down-regulation in K14 and integrin alpha6 protein and a loss of E-cadherin at week 2, whereas vimentin was increased. FIB EEs were devoid of transcripts for E-cadherin at both time points, although transcription of the other genes remained constant in all phenotypes. Thus, the FIB phenotype exhibited a poor epithelial structure coinciding with disturbances in the expression of epithelial biomarkers and the persistence of mesenchymal vimentin. Transcription analysis revealed post-transcriptional regulation of vimentin in IHGK and EPI and of K14 and alpha6 in FIB cells. Our findings indicate that differences in the epithelial integrity and expression of molecules in EEs allow for the discrimination of EPI and FIB cells. This suggests that FIB cells share features of epithelial-mesenchymal transition and reflect a more progressive stage in epithelial cell transformation.

Alcohol--the neglected risk factor in head and neck cancer

Alcohol remains second only to cigarette smoking as a risk factor for head and neck cancer worldwide. The increase in incidence in head and neck cancer in a number of countries appears linked at least in part to contemporaneous rises in alcohol consumption. The relative increase in risk in women may also relate to increasing alcohol consumption. Women may be particularly sensitive to alcohol-induced tumours in the oral/oropharyngeal sites. The risk is dose related, but with a non-linear increase for heavy drinkers (>100 g i.e. 12 units/day). The type of alcoholic beverage consumed seems less important. Potential mechanisms include local toxic cellular proliferation; carcinogenic action of metabolites e.g. acetaldehyde or impurities; induction of enzymes which activate procarcinogens; reduction of the protective retinoic acid; genetic polymorphism may play a part in certain geographic locations. Alcohol is also linked to stage at presentation, risk of second primary and the occurrence of comorbidity. Public awareness of the risks of alcohol remains disappointingly low. Those in identifiable high-risk groups should perhaps be targeted specifically for counselling.