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 defected in glioblastomas (GBM), the genotype of +7/-10 HG-OT suggests that these tumors are GEM 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 GEM and other neoplasms. In this study, we screened for PTEN mutations in six low-grade oligodendroglial tumors (LG-OT), five 1p-/19q- HG-seven +7/-10 HG-OT, and nine xenografted GEM. PTEN mutations were detected in none of the LG-OT and 1p-/19q- HG-OT, once in +7/-10 HG-OT, and frequently in GEM. As one of the + 7/-10 HG-OT harbored a PTEN mutation, this demonstrates that PTEN can be involved in the oncogencsis of this genetic subtype of HG-OT. The lower frequency of PTEN mutations in +7/-10 HG-OT compared to GEM suggests that these tumors are of a distinct tumor type rather than GEM. Published by Elsevier Science Inc.