Expression of methylthioadenosine phosphorylase (MTAP) in pilocytic astrocytomas

BACKGROUND/OBJECTIVES Pilocytic astrocytomas (PAs) are the most frequent astrocytomas in children and adolescents. Methilthioadenosine phosphorylase(MTAP) is a tumor-suppressor gene, the loss of expression of which is associated with a poor prognosis and better response to specific chemotherapy in leukemia and non-small-cell lung cancer. The expression of MTAP in brain tumors remains largely unknown and its biological role in PA is still unexplored. Our aims were to describe the immunohistochemical MTAP expression in a series of PAs and relate it to the clinicopathological features of the patients. METHODS We assessed MTAP expression on immunohistochemistry in 69 pediatric and adult patients with PA in a tissue microarray platform. RESULTS Retained expression of MTAP was seen in >85% of the tumors compared to in the nonneoplastic adjacent tissue. Only 3 supratentorial tumors showed a complete loss of MTAP expression. No significant association with clinicopathological features or overall survival of the patients was found. CONCLUSIONS MTAP expression is retained in PAs and is not an outcome predictor for these tumors. Nevertheless, a subset of patients with PAs exhibiting a loss of MTAP could potentially benefit from treatment with specific chemotherapy, especially when lesions are recurrent or surgical resection is not recommended.This study was partially supported by the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (2012/19590-0) and an HCB program of financial support (Programa de Apoio e Incentivo a Pesquisa)

Loss of MTAP expression is a negative prognostic marker in Ewing sarcoma family of tumors.

AIM: The Ewing sarcoma family of tumors (ESFT) is a group of malignant small round cell neoplasms of bones and soft tissues closely histogenetically related. Methylthioadenosine phosphorylase (MTAP) deficiency has been recently associated with increased tumor aggressiveness and poor outcomes in different types of neoplasms. However, the expression of this biomarker and its biological role in ESFT remain largely unknown. METHODS: Immunohistochemical expression of MTAP was accessed in 112 patients with ESFT in a tissue microarray platform and associated with clinicopathological parameters and overall survival(OS). RESULTS: Loss of MTAP expression was significantly associated with lower OS in both univariate and multivariate analyses. CONCLUSION: Loss of MTAP expression is an independent negative prognostic biomarker in ESFT.Fundação de Amparo á Pesquisa do Estado de São Paulo (FAPESP) and CNPq grants to RM Reis. WP Menezes is recipient of a FAPESP fellowship (2016/06833–2). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.info:eu-repo/semantics/publishedVersio