Repression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) but not its receptors during oral cancer progression.

BACKGROUND: TRAIL plays an important role in host immunosurveillance against tumor progression, as it induces apoptosis of tumor cells but not normal cells, and thus has great therapeutic potential for cancer treatment. TRAIL binds to two cell-death-inducing (DR4 and DR5) and two decoy (DcR1, and DcR2) receptors. Here, we compare the expression levels of TRAIL and its receptors in normal oral mucosa (NOM), oral premalignancies (OPM), and primary and metastatic oral squamous cell carcinomas (OSCC) in order to characterize the changes in their expression patterns during OSCC initiation and progression. METHODS: DNA microarray, immunoblotting and immunohistochemical analyses were used to examine the expression levels of TRAIL and its receptors in oral epithelial cell lines and in archival tissues of NOM, OPM, primary and metastatic OSCC. Apoptotic rates of tumor cells and tumor-infiltrating lymphocytes (TIL) in OSCC specimens were determined by cleaved caspase 3 immunohistochemistry. RESULTS: Normal oral epithelia constitutively expressed TRAIL, but expression was progressively lost in OPM and OSCC. Reduction in DcR2 expression levels was noted frequently in OPM and OSCC compared to respective patient-matched uninvolved oral mucosa. OSCC frequently expressed DR4, DR5 and DcR1 but less frequently DcR2. Expression levels of DR4, DR5 and DcR1 receptors were not significantly altered in OPM, primary OSCC and metastatic OSCC compared to patient-matched normal oral mucosa. Expression of proapoptotic TRAIL-receptors DR4 and DR5 in OSCC seemed to depend, at least in part, on whether or not these receptors were expressed in their parental oral epithelia. High DR5 expression in primary OSCC correlated significantly with larger tumor size. There was no significant association between TRAIL-R expression and OSSC histology grade, nodal status or apoptosis rates of tumor cells and TIL. CONCLUSION: Loss of TRAIL expression is an early event during oral carcinogenesis and may be involved in dysregulation of apoptosis and contribute to the molecular carcinogenesis of OSCC. Differential expressions of TRAIL receptors in OSCC do not appear to play a crucial role in their apoptotic rate or metastatic progression.

Association of p21/p27 polymorphisms with risk of HPV16-associated oral squamous cell carcinoma

The increasing incidence of oral squamous cell carcinoma (OSCC) among young adults has been associated with sexually transmitted infection of human papillomavirus (HPV), particularly HPV16. Given the roles of p21 (WAF1/Cip1/CDKN1A) and p27 (Kip1/CDKNIB) in cell-cycle regulation and of HPV16 E6 and E7 oncoproteins in p53 degradation and pRb inactivation, the effect of HPV16 L1 seropositivity and three putatively functional single-nucleotide polymorphisms (SNPs) of p21 (p21 C70T and p21 C98A) and p27 (p27 T109G), individually and in combination, on the risk of OSCC was evaluated in a hospital-based case-control study of 327 cases and 401 cancer-free controls who were frequency-matched on age, gender and smoking status. Individuals with HPV16 L1 seropositivity had an overall 3-fold increased risk of having OSCC than those with HPV16 seronegativity. The increased risk of HPV16-associated OSCC was particularly found among younger people (aged ≤ 50 years), males, never smokers, never drinkers and oropharynx cancer patients. None of three p21 and p27 polymorphisms alone was significantly associated with risk of OSCC. Individuals with variant genotypes for both p21 polymorphisms were more likely to have OSCC than individuals with wild-type genotypes or variant genotypes for either one of the p21 polymorphisms (adjusted OR, 1.4; 95% CI, 0.9-2.1). There was a borderline significant or significant interaction between the p21 C70T, combined p21 and combined p21/p27 genotypes and HPV16 L1 seropositivity on risk of OSCC. The three studied p21 and p27 polymorphisms, individually or in combination, did not appear to have an effect on HPV16-related clinical outcomes (overall and disease-free survival and tumor recurrence). Despite the fact that the exact biological mechanism remains to be explored, these findings suggest possible involvement of p21variants, particularly the p21 C70T variant genotypes (CT/TT), in the etiology of HPV16-associated OPSCC. Further large and functional studies are required to validate the findings.^

Identification of genetic risk factors for cerebellar mutism in pediatric brain tumor patients

Following posterior fossa surgery for resection of childhood medulloblastoma and primitive neuroectodermal tumor (M/PNET), cerebellar mutism (CM) may develop. This is a condition of absent or diminished speech in a conscious patient with no evidence of oral apraxia, which can be accompanied by other symptoms of the posterior fossa syndrome complex, which includes ataxia and hypotonia. Little is known about the etiology. Therefore, we conducted a SNP, gene, and pathway-level analysis to assess the role of host genetic variation on the risk of CM in M/PNET subjects following treatment. Cases (n= 20) and controls (n= 53) were recruited from the Childhood Cancer Epidemiology and Prevention Center, in Houston, TX. DNA samples were genotyped using the Illumina Human 1M Quad SNP chip. Ten pathways were identified from logistic regression used to identify the marginal effect of each SNP on CM risk. The minP test was conducted to identify associations between SNPs categorized to genes and CM risk. Pathways were assessed to determine if there was a significant enrichment of genes in the pathway compared to all other pathways. There were 78 genes that reached the threshold of min P ≤0.05 in 948 genes. The Neurotoxicity pathway was the most significant pathway after adjusting for multiple comparisons (q=0.040 and q=0.005, using Fisher's exact test and a test of proportions, respectively). Most genes within the Neurotoxicity pathway that reached a threshold of minP ≤0.05 were known to have an apoptosis function, possibly inducing neuronal apoptosis in the dentatothalamocortical pathway, and may be important in CM etiology in this population. This is the first study to assess the potential role of genetic risk factors on CM. As an exploratory study, these results should be replicated in a larger sample. ^