Loss of heterozygosity on chromosomes 10q, 9p, 17p and 13q in Malays with malignant glioma

Cell biology of glioblastoma multiforme: from basic science to diagnosis and treatment

First described in the 1800s, glioblastoma multiforme (GBM), a class IV neoplasm with astrocytic differentiation, as per the revised 2016 World Health Organization classification of tumors of the central nervous system (CNS) is the most common malignant tumor of the CNS. GBM has an extremely wide set of alterations, both genetic and epigenetic, which yield a great number of mutation subgroups, some of which have an established role in independent patient survival and treatment response. All of those components not only represent a closed cycle but are also relevant to the tumor biological behavior and resistance to treatment as they form the pathobiological behavior and clinical course. The presence of different triggering mutations on the background of the presence of key mutations in the GBM stem cells (GBMsc) further separates GBM as primary arising de novo from neural stem cell precursors developing into GBMsc and secondary, by means of aggregated mutations. Some of the change in cellular biology in GBM can be observed via light microscope as they form the cellular and tissue hallmarks of the condition. Changes in genetic information, resulting in alteration, suppression and expression of genes compared to their physiological levels in healthy astrocytes lead to not only cellular, but also extracellular matrix reorganization. These changes result in a multiform number of micromorphological and purely immunological/biochemical forms. Therefore, in the twenty-first century the term multiforme, previously outcast from nomenclatures, has gained new popularity on the background of genotypic diversity in this neoplastic entry.

Characterization of Salt-Induced Epigenetic Segregation by Genome-Wide Loss of Heterozygosity and its Association with Salt Tolerance in Rice (Oryza sativa L.)

In a breeding effort to develop salt tolerant (ST) rice varieties by designed QTL pyramiding, large numbers of progenies derived from four crosses between salt- or drought- tolerant BC2F5 IR64 introgression lines, were subjected to severe salt stress, resulting in 422 ST plants. The progeny testing of the selected F3 lines under more severe salt stress resulted in identification of 16 promising homozygous lines with high levels of ST. Genetic characterization of the 422 ST F3 progeny and 318 random F2 plants from the same four crosses using 105 segregating SSR markers lead to three interesting discoveries: (1) salt stress can induce genome-wide epigenetic segregation (ES) characterized by complete loss of heterozygosity (LOH) and nearly complete loss of an allele (LOA) in the F3 progenies of four rice populations in a single generation; (2) ∼25% of the stress-induced ES loci were transgenerational and inherited from their salt- and drought- selected parents; and (3) the salt-induced LOH and LOA loci (regions) appeared to contain genes/alleles associated with ST and/or drought tolerance. 32 genomic regions that showed one or more types of salt-induced ES in the random and salt-selected progenies from these crosses. The same or different types of ES were detected with two large genomic regions on chromosomes 1 and 6 where more and the strongest ES were found across different populations. 14 genomic regions were found where the salt-induced ES regions were overlapping with QTL affecting ST related traits. The discovery of the three types of salt-induced ES showed several interesting characteristics and had important implications in evolution and future breeding for developing stress-resilient rice and crops.

Lack of association between LOH in the 9p region and clinicopathologic parameters in primary breast cancer

Previous studies have suggested the involvement of the 9p region in the genesis and progression of several types of cancer. To perform a more in-depth investigation of the 9p region in samples from breast carcinomas, we analyzed loss of heterozygosity (LOH) in 230 patients with primary breast cancer using five microsatellite markers spanning a genomic region of approximately 16.2 megabases. Genomic DNA was obtained from frozen tumor tissue, and peripheral blood was used as a normal reference. Among all samples, 171 (74%) were informative for at least 1 marker and 44 (25.73%) showed LOH. The LOH rates detected for all markers ranged from 10.29% (D9S169) to 15.97% (D9S1749). Among the informative cases for intragenic markers D9S1748 (CDKN2A) and D9S1749 (MTAP), we noticed a concordant loss of 90% (9/10). Associations between LOH frequencies and clinicopathologic parameters were found between marker D9S200 and tumor grade (P < 0.05), and between marker D9S1748 and estrogen receptor (ER) status (P < 0.05). In conclusion, our results agree with other data from the literature that point to LOH as a secondary mechanism of tumor suppressor inactivation on 9p in breast cancer, showing lower frequencies than those observed in other types of cancer. On the other hand, our results point to an interesting association between the concordant loss of genes CDKN2A and MTAP, which was not sufficiently explored in primary breast cancer.

Radiation-induced glioblastoma in a medulloblastoma patient: a case report with molecular features

We report a case of glioblastoma (GBM) occurring 8 years after radiation therapy for a medulloblastoma. A 15-year-old boy underwent surgery and radiotherapy for a medulloblastoma and 8 years later he developed a second tumor at the same site. The second lesion showed different histological and molecular features, was diagnosed as a glioblastoma and fulfilled the criteria of radiation-induced neoplasm. Mutational analysis of the p53 gene showed a C to G transition at codon 176 in tumor DNA. LOH was detected at 17p and 19q. The tumor also showed O6-methylguanine-DNA methyl-transferase (MGMT) promoter methylation and no amplification of EGF receptor. In conclusion, the radiation-induced MGMT hyper-methylation and p53 mutations may have a role in the development of a subgroup of radio-induced glioma (RIG), suggesting that these molecular alterations directly cooperate in the genesis of the post-irradiation GBM. Moreover RIGs seem to be a heterogeneous group of tumors that may resemble either primary or secondary GBM.

History of neurosciences at the School of Medical Sciences, Universiti Sains Malaysia

Universiti Sains Malaysia is the only institution in Malaysia which incorporates all fields of the neurosciences under one roof. The integration of basic and clinical neurosciences has made it possible for this institution to become an excellent academic and research centre. This article describes the history, academic contributions and scientific progress of neurosciences at Universiti Sains Malaysia.

LGI1: a gene involved in epileptogenesis and glioma progression?

The leucine-rich, glioma inactivated gene 1 (LGI1) gene on human chromosome 10q24 was first identified as a candidate tumor suppressor gene for glioma. Surprisingly, mutations in LGI1 were also shown to cause an idiopathic epilepsy syndrome, autosomal dominant lateral temporal lobe epilepsy (ADLTE). LGI1 is one of the only two currently known non-ion channel genes whose mutations cause idiopathic epilepsy in humans. In this review we summarize the current data on structure and function of the LGI1 protein and discuss clinical aspects of ADLTE and their correlation with LGI1. We also propose that the evidence supporting the tumor suppressor role of LGI1 in malignant gliomas is weak and that further work is necessary to establish LGI1 role in glial cells.