Expression and Methylation Pattern of p16 in Neuroblastoma Tumorigenesis

Understanding migration, population and differentiation of primordial neural crest cells will help in evolving biology of neuroblastoma. P16 is a tumour suppressor gene contributing in cell cycle arrest as cyclin dependent kinase inhibitor. Methylation is an important mechanism for silencing tumor suppressor genes. The aim of this study was to evaluate the role of p16 and its methylation pattern in neuroblastoma tumorigenesis. This study included 23 cases (11 male; 12 female) and 31 samples from archival paraffin embedded tissues. P16 was studied in 5 samples of normal adrenal medullar tissue, 5 samples of adrenal tissue including blastic rests, 5 samples of neuroblastoma in situ tissue and in 8 samples of neuroblastoma tissues primary and after chemotherapy in each group. The adrenal gland tissues were obtained from paediatric autopsy cases. Expression of p16 was searched by immunohistochemistry. Methylation specific PCR was used to detect the methylation rate of p16. The age range of autopsy cases was between 20 weeks of foetal age and 36 months of infant age. The mean age of neuroblastoma cases was 45 months. P16 expression was positive in normal adrenal tissues, in one of 5 samples of adrenal blastic rest tissue and in all of samples of after chemotherapy; while no expression was observed in neuroblastoma and neuroblastoma in situ tissues. P16 methylation was observed in samples of neuroblastoma in situ and primary neuroblastoma tissues. Our results suggest that p16 and its methylation seems to play role in neuroblastoma tumorigenesis and in the migration, population and differentiation of primordial neural crest cells. Inhibitors of DNA methylation may provide a useful tool for restoring p16 activity in neuroblastoma treatment

Predicting invasive phenotype with CDH1, CDH13, CD44, and TIMP3 gene expression in primary breast cancer

We aimed to determine changes in the expression of the genes CDH1, CDH13, CD44, and TIMP3 to look for any relationship between them, HER2 and ESR1 expression at the RNA level, and the histopathological properties of tumors. We also analyzed the expression properties of double-negative (estrogen receptor [ER] and human epidermal growth factor receptor [HER2] both negative) breast tumors. Expression status was studied in fresh tissue at the mRNA level with quantitative PCR using hydrolysis probes. Sixty-two cancer patients and four normal controls were included in the study. When the tumor group was analyzed as a whole, the correlations of ESR1 with CDH1, CDH13, and TIMP3 were P < 0.05, P < 0.005, and P < 0.005, respectively. In ER-positive tumors, CDH1 and CDH13 were correlated directly (P < 0.005) when HER2 was correlated with CDH1, CDH13, and TIMP3 indirectly (P < 0.005, P < 0.005, and P < 0.05, respectively). CDH1 and CD44 had a strong indirect correlation (P < 0.005) in ER-negative tumors. There were significant differences in the expression levels of the CDH13, TIMP3, and CD44 genes (P < 0.005, P < 0.005, and P < 0.05, respectively) between the ER-positive and -negative groups. All four genes were found to be correlated with invasive properties in both ER-positive and -negative tumors. In double-negative tumor samples, only CD44 had a significant and strong correlation with stage, lymph node involvement, and metastasis (P < 0.05, P < 0.005, and P < 0.05, respectively). As a conclusion, a decrease in CDH1, CDH13, and TIMP3 expression levels with an increase in CD44 can be used as an indicator for invasion in both ER-positive and -negative breast tumors. In double-negative tumor tissues, CD44 can be considered a marker for aggressive properties. (Cancer Sci 2009; 100: 2341-2345)