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The molecular characteristics of low-grade and high-grade areas in desmoplastic infantile astrocytoma / ganglioglioma [methylation array]

ABSTRACT: A distinctive feature of the histopathology of desmoplastic infantile astrocytomas and gangliogliomas (DIA/DIGs) is a combination of low-grade and high-grade areas. In this study, we test the hypothesis that low-grade and high-grade areas in DIA/DIGs have distinct molecular characteristics. Tissue samples from microdissected low-grade and high-grade areas in 12 DIA/DIGs were analyzed by DNA methylome profiling, whole exome sequencing, RNA sequencing, and immunohistochemistry. Copy number variants among the tumours and between the two morphologically distinct areas were infrequent. No recurrent genetic alterations were identified across the tumor series, and high-grade areas did not have additional genetic alterations to explain their distinct morphology or biological behaviour. However, high-grade areas showed relative hypomethylation in genes downstream of the transcription factors SOX9 and LEF1 and evidence of a core SOX9 transcription network alongside activation of the BMP, WNT, and MAPK signalling pathways. This study contributes to our knowledge of molecular genetic alterations in DIA/DIGs, uncovers molecular differences between the two distinct cell populations in these tumours, and suggests potential therapeutic targets among the more proliferative cell population in DIA/DIGs.

ORGANISM(S): Homo sapiens

PROVIDER: GSE193196 | GEO | 2022/05/24

REPOSITORIES: GEO

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Project description:Objective: Ovarian tumors of low-malignant potential (LMP) and low-grade serous ovarian carcinomas are thought to represent different stages on a tumorigenic continuum and to develop along pathways distinct from that of high-grade serous ovarian carcinoma. Past studies have utilized gene expression profiles to support this theory. The objective of the current study was to identify new genes whose expression profiles in LMP ovarian tumors and low-grade ovarian carcinomas differ from that in high-grade ovarian carcinomas. Methods: We used RNA from 3 normal human ovarian surface epithelia (HOSE) and from 10 low-grade and 10 high-grade serous ovarian carcinoma samples to perform gene expression profiling. Using real-time reverse-transcription polymerase chain reaction (RT-PCR), we evaluated changes in PAX2 mRNA expression in cDNA created from RNA extracted from an independent set of ovarian tissue samples (7 LMP tumors and 17 low-grade and 23 high-grade serous carcinomas). We also examined PAX2 expression using Western blot analysis of protein extracted from a set of ovarian LMP and low- and high-grade carcinoma tissue samples. Additionally, we used immunohistochemistry (IHC) to validate PAX2 overexpression in a third independent set of paraffin ovarian tissue sections from 17 LMP tumors and 16 low- and 257 high-grade carcinomas. Results: Gene profiling revealed higher expression of PAX2 in low-grade than in high-grade ovarian carcinomas. Real-time RT-PCR demonstrated a statistically significant difference in median PAX2 mRNA expression, expressed as fold change, among ovarian LMP tumor (1837.38), low-grade (183.12), and high-grade (3.72) carcinoma samples (p=0.015). Western blot analysis revealed strong PAX2 expression in ovarian LMP and low-grade carcinoma samples but no PAX2 protein expression in high-grade carcinomas. On IHC, more LMP tumor and low-grade carcinoma samples expressed moderate to high levels of PAX2 than did high-grade ovarian carcinoma samples. The numbers of samples with strong nuclear staining was significantly higher for ovarian LMP tumors (10 of 17, p<0.001) and low-grade serous carcinomas (10 of 16, p<0.001) than for high-grade carcinomas (27 of 257). Discussion: Our identification and validation of higher PAX2 expression in ovarian LMP tumors and low-grade serous carcinomas than in high-grade carcinomas supports the two-tiered hypothesis that the first two are on a continuum and are distinct from high-grade ovarian carcinomas. PAX2 may represent a potential biomarker and future therapeutic target for individualizing chemotherapy for ovarian LMP tumors and low-grade carcinomas in the future. Experiment Overall Design: We used RNA from 3 normal human ovarian surface epithelia (HOSE) and from 10 low-grade and 10 high-grade serous ovarian carcinoma samples to perform gene expression profiling. Using real-time reverse-transcription polymerase chain reaction (RT-PCR), we evaluated changes in PAX2 mRNA expression in cDNA created from RNA extracted from an independent set of ovarian tissue samples (7 LMP tumors and 17 low-grade and 23 high-grade serous carcinomas). We also examined PAX2 expression using Western blot analysis of protein extracted from a set of ovarian LMP and low- and high-grade carcinoma tissue samples. Additionally, we used immunohistochemistry (IHC) to validate PAX2 overexpression in a third independent set of paraffin ovarian tissue sections from 17 LMP tumors and 16 low- and 257 high-grade carcinomas.

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The molecular characteristics of low-grade and high-grade areas in desmoplastic infantile astrocytoma / ganglioglioma [methylation array]

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