PTEN Mutation Analysis in Two Genetic Subtypes of High-Grade Oligodendroglial Tumors: PTEN is Only Occasionally Mutated in One of the Two Genetic Subtypes

We recently identified two genetic subtypes of high-grade oligodendroglial tumors (HG-OT): 1p−/19q− HG-OT are characterized by a loss of chromosome 1p32–36 (del(1)(p32–p36) and/or a del(19)(q13.3); whereas +7/−10 HG-OT harbor a gain of chromosome 7 (+7) and/or a −10 without a loss of 1p32–36 and 19q13.3. Because a −10 and a +7 are most frequently detected in glioblastomas (GBM), the genotype of +7/−10 HG-OT suggests that these tumors are GBM with a prominent oligodendroglial phenotype rather than anaplastic oligodendrogliomas. PTEN is a tumor suppressor gene, located at 10q23.3, which is involved in tumor progression of GBM and other neoplasms. In this study, we screened for PTEN mutations in six low-grade oligodendroglial tumors (LG-OT), five 1p−/19q− HG-OT, seven +7/−10 HG-OT, and nine xenografted GBM. PTEN mutations were detected in none of the LG-OT and 1p−/19q− HG-OT, once in +7/−10 HG-OT, and frequently in GBM. As one of the +7/−10 HG-OT harbored a PTEN mutation, this demonstrates that PTEN can be involved in the oncogenesis of this genetic subtype of HG-OT. The lower frequency of PTEN mutations in +7/−10 HG-OT compared to GBM suggests that these tumors are of a distinct tumor type rather than GBM. Published by Elsevier Science Inc.