Methylthioadenosine phosphorylase inactivation depends on gene deletion in laryngeal squamous cell carcinoma

Development of head and neck pathology in Europe

This review gives a brief history of the development of head and neck pathology in Europe from a humble beginning in the 1930s to the explosive activities the last 15 years. During the decades before the introduction of immunohistochemistry in the 1980s, head and neck pathology grew as a subspeciality in many European countries. In the late 1940s, the Institute of Laryngology and Otology with its own pathology laboratory was founded in London, and in 1964 the World Health Organization (WHO) International Reference Centre for the Histological Classification of Salivary Tumours was established at the Bland-Sutton Institute of Pathology, also in London. International collaboration, and very much so in Europe, led to the publication of the first WHO Classification of Salivary Gland Tumours in 1972. In the 1960s, a salivary gland register was organised in Hamburg and in Cologne the microlaryngoscopy was invented enabling microscopic endoscopic examination and rather shortly afterwards a carbon dioxide laser attached to the microscope became established and laryngeal lesions could be treated by laser vaporisation. During the last three decades, the use of immunohistochemistry supplemented with cytogenetic and refined molecular techniques has greatly facilitated the pathological diagnostics of head and neck lesions and has had a huge impact on research. Collaboration between different European centres has drastically increased partly due to establishment of scientific societies such as the Head and Neck Working Group (HNWG) within the European Society of Pathology and the International Head and Neck Scientific Group (IHNSG). A very large number of European pathologists have contributed to the 2nd, 3rd and 4th WHO books, and are involved in the upcoming 5th edition. Accredited educational meetings and courses are nowadays regularly arranged in Europe. Numerous textbooks on head and neck pathology have been written and edited by European pathologists. The increased collaboration has created larger series of tumours for research and new entities, mainly defined by their genetic abnormalities, are continuously emerging from Europe, particularly regarding salivary gland neoplasms and "undifferentiated" sinonasal tumours. These findings have led to a better and more precise classification and open the possibilities for new treatment strategies.

Deletion and downregulation of MTAP contribute to the motility of esophageal squamous carcinoma cells

Esophageal squamous cell carcinoma (ESCC) is among the most common malignancies, with a low 5-year overall survival rate. In previous studies, we and others have found that 9p21.3 was the most frequently deleted region in ESCC. The MTAP gene, which is located close to CDKN2A/B in 9p21.3, encodes methylthioadenosine phosphorylase. This enzyme plays an important role during the process of adenosine transfer. In the present study, we found that MTAP is deleted at the genomic level in 19.1% (64/341) of primary ESCC tumors, and decreased mRNA and protein expression were present in 31.1% (28/90) and 33.3% (6/18) of ESCCs, respectively. Further statistical analysis showed a positive correlation between deletion and decreased mRNA expression of MTAP in the ESCC tissues tested (coefficient: 0.826; P=1.17×10⁻²³). Knockdown of MTAP expression using small interfering RNA-mediated silencing promoted the invasion and migration of ESCC cells. Also, overexpression of MATP using pcDNA3.1-MTAP plasmid decreased the cell invasion and migration. At the molecular level, MTAP knockdown downregulated E-cadherin and p-GSK3β but upregulated Slug expression. Our results indicated that MTAP deletion results in the decreased expression in ESCCs and that it plays a role in promoting the mobility and inducing the epithelial-to-mesenchymal transition of ESCC cells via the GSK3β/Slug/E-cadherin axis. The data suggest that MTAP might function as a tumor suppressor gene in ESCC.

Characterization of MTAP Gene Expression in Breast Cancer Patients and Cell Lines

MTAP is a ubiquitously expressed gene important for adenine and methionine salvage. The gene is located at 9p21, a chromosome region often deleted in breast carcinomas, similar to CDKN2A, a recognized tumor suppressor gene. Several research groups have shown that MTAP acts as a tumor suppressor, and some therapeutic approaches were proposed based on a tumors´ MTAP status. We analyzed MTAP and CDKN2A gene (RT-qPCR) and protein (western-blotting) expression in seven breast cancer cell lines and evaluated their promoter methylation patterns to better characterize the contribution of these genes to breast cancer. Cytotoxicity assays with inhibitors of de novo adenine synthesis (5-FU, AZA and MTX) after MTAP gene knockdown showed an increased sensitivity, mainly to 5-FU. MTAP expression was also evaluated in two groups of samples from breast cancer patients, fresh tumors and paired normal breast tissue, and from formalin-fixed paraffin embedded (FFPE) core breast cancer samples diagnosed as Luminal-A tumors and triple negative breast tumors (TNBC). The difference of MTAP expression between fresh tumors and normal tissues was not statistically significant. However, MTAP expression was significantly higher in Luminal-A breast tumors than in TNBC, suggesting the lack of expression in more aggressive breast tumors and the possibility of using the new approaches based on MTAP status in TNBC.