Investigation of the Effects of Alterations in the Glutamate Receptor, GRIK2 on Osteosarcoma Tumourigenesis
Year: 2019
Type: dissertation
Abstract: Over the past two decades, osteosarcoma survival rates have remained stagnant, and the discovery of novel molecular alterations is necessary in clinical research. Osteosarcoma tumours were analyzed for copy number alterations on a SNP array, and recurrent copy number losses were observed in 14% of samples in the 6q16.3, suggesting this region may be important in the disease. Focal deletions were adjacent to the GRIK2 gene which encodes an ionotropic glutamate receptor, and members of other glutamate receptor families have been linked to osteosarcoma through genome wide association studies. The mechanistic relationship between the receptors and the disease is unclear, although glutamate receptors are expressed in bone cells and may disrupt the bone remodelling process, which has been hypothesized to lead to tumour formation. The goal of this study was to investigate the relationship between the focal deletions and the expression, function and regulation of the GRIK2 gene in osteosarcoma. The focal deletions overlapped with non-coding regulatory elements in the 5’ intergenic space of GRIK2, and a similar trend was observed in a larger dataset that acted as a validation tool. Expression levels of GRIK2 varied in tumour samples, and there was a subset of samples with high expression that included four tumours with homozygous deletions suggesting a potential link between the deletions and expression. The functional role of GRIK2 was examined in vitro by gene overexpression experiments, and an anti-tumour phenotype was observed in cells with high GRIK2 that was marked by decreased proliferation and migration, and increased incidences of apoptosis. Additionally, the effect of deletions on GRIK2 expression regulation was examined by gene editing experiments. Targeted deletion of the SETDB1 histone methyltransferase binding sequence increased GRIK2 gene and protein levels. In conjunction with higher GRIK2 expression, levels of the repressive H3K9Me3 were decreased. The focal deletions may be involved in shifting GRIK2 from a repressed to an active state, which was associated with a less aggressive phenotype. This study has also demonstrated the potential utility of regulatory elements as possible therapeutic targets as these sequences could play roles in cancer initiation and growth.
Source: TSpace (University of Toronto)
Author: Justin Mayers
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3089206204