Abstract Thyroid diseases have a complex and multifactorial aetiology. Despite the numerous studies on the signals referable to the malignant transition, still remain elusive the molecular mechanisms concerning the role of oxidative stress. Based on its strong oxidative power, H2O2 could be responsible for the high level of oxidative DNA damage observed in cancerous thyroid tissue and hyper-activation of mitogen-activated protein kinase (MAPK), and PI3K/Akt, that mediate ErbB signaling. Increased levels of 8-oxoG DNA adducts have been detected in the early stages of thyroid cancer. These DNA lesions are efficiently recognized and removed by the base excision repair (BER) pathway initiated by 8-oxoG glycosylase1 (OGG1). This study investigated the relationship between the EGFR and OGG1-BER pathways and their mutual regulation following oxidative stress stimulus by H2O2 in human thyrocytes. We clarified the modulation of ErbB receptors and their downstream pathways (PI3K / Akt and MAPK / ERK) under oxidative stress (from H2O2) at the level of gene and protein expression, according to the mechanism defined in a non-pathological cell system, Nthy-ori 3-1. Later, on the basis of the obtained results of gene expression cluster analysis in normal cells, we assessed the dysregulation of the relationships in a model of papillary thyroid cancer with RET/TPC rearrangement (TPC-1). Our observations demonstrated that a H2O2 stress may induce a physiological cross-regulation between ErbB and OGG1-BER pathways in normal thyroid cells (while this is dysregulated in the TPC-1 cells. Gene expression data also delineated that MUTYH gene could play a physiological role in cross-talk between ErbB and BER pathways and this function is instead lost in cancer cells. Overall our data about OGG1 protein expression suggest that the alternative splicing mechanisms may lead to different protein isoforms, physiologically regulated in response to ErbB modulation, and that these could be dysregulated in the progression of thyroid malignancies with RET/TPC rearrangement.

Background: Colorectal adenoma undergoes neoplastic progression via the normal epithelium-adenoma-adenocarcinoma sequence as reported in the Vogelgram. The risk of developing cancer is strongly associated with the number and size of adenoma and with the subtype. Currently, adenomatous polyps can be distinguished on the basis of histology: the prevalence are tubular, 5-15% are villous and tubular/villous. Considering the increased risk for malignant transformation described for tubular/villous adenomas, patients diagnosed with adenomatous polyposis are at increased risk of developing CRC. The Wnt/β-catenin pathway plays a key role in the onset of colorectal adenoma, in particular intestinal cells first acquire loss-of-function mutations in APC gene that induce the formation of adenomas. Methods: Wnt/β-catenin pathway APC, Wnt3a, Wnt5a, LEF1, BCL9 genes and protein expression analyses were conducted by qRT-PCR and western blot in 68 colonic samples (polyps and adjacent mucosa) from 41 patients, of which 17 affected by FAP. Ten normal colonic mucosal samples were collected from 10 healthy donors. Results: In this study both APC gene and protein resulted less expressed in colon tumor compared to the adjacent colonic mucosa. Conversely, activated β-catenin was more expressed in polyps than in the adjacent mucosa. All results confirmed literature data on carcinomas. A statistically significant correlation between Wnt3a and BCL9 both in polyps and in the adjacent mucosa underlies that the canonical Wnt pathway is activated in early colon carcinogenesis and that the adjacent mucosa is already altered. Conclusion: This is the first study analyzing the difference in expression of Wnt/β-catenin pathway in human colorectal adenomas. Understanding the progression from adenomas to colorectal carcinomas is essential for the development of new therapeutic strategies and improving clinical outcomes.