Mutation characteristics of osteosarcoma: a single center study of 64 cases using next-generation sequencing / 中华病理学杂志

Objective: To investigate the distribution and characteristics of gene mutations in osteosarcoma, and to analyze the frequency and types of detectable mutations, and to identify potential targets for individualized treatment of osteosarcoma. Methods: The fresh tissue or paraffin-embedded tissue samples of 64 cases of osteosarcoma that were surgically resected or biopsied and then subject to next generation sequencing, were collected from Beijing Jishuitan Hospital, China from November 2018 to December 2021. The tumor DNA was extracted to detect the somatic and germline mutations using targeted sequencing technology. Results: Among the 64 patients, 41 were males and 23 were females. The patient age ranged from 6 to 65 years with a median age of 17 years, including 36 children (under 18 years old) and 28 adults. There were 52 cases of conventional osteosarcoma, 3 cases of telangiectatic osteosarcoma, 7 cases of secondary osteosarcoma, and 2 cases of parosteosarcoma. The detection rate of gene mutations was overall 84.4% (54/64). There were 324 variations in 180 mutated genes, including 125 genes with copy number variations, 109 single nucleotide variants, 83 insertions or deletions, and 7 gene fusions. The most common mutated genes were TP53, VEGFA, CCND3, ATRX, MYC, RB1, PTEN, GLI1, CDK4 and PTPRD. Among them, TP53 had the highest mutation rate (21/64, 32.8%), single nucleotide variant was the main mutation type (14/23, 60.9%), and 2 cases carried the TP53 germline mutation. VEGFA and CCND3 showed copy number amplification simultaneously in 7 cases. Conclusions: The high-frequency mutation of TP53 suggests that it plays an important role in the pathogenesis and development of osteosarcoma. VEGFA, CCND3 and ATRX are mutated genes in osteosarcoma and worthy of further studies. Combination of pathologic diagnosis and next generation sequencing with clinical practice can guide individualized treatment for patients with refractory, recurrent and metastatic osteosarcoma.

Mutation of isocitrate dehydrogenase gene in Chinese patients with glioma / 中华病理学杂志

<p><b>OBJECTIVE</b>To investigate mutation status of isocitrate dehydrogenase (IDH) 1 and IDH2 genes in Chinese patients with gliomas in correlation with clinicopathological characteristics.</p><p><b>METHODS</b>Formalin-fixed and paraffin-embedded (FFPE) tissue samples of 234 gliomas were collected including the matched blood samples in 30 patients. DNA was extracted, followed by PCR-Sanger sequencing to detect IDH1 and IDH2 gene mutations. Immunohistochemistry was performed using mutation-specific antibody recognizing IDH1R132H mutation. Immunostains for p53 and epidermal growth factor receptor (EGFR) were also performed. Oligodendroglial tumors with IDH mutation were double stained with IDH1R132H and GFAP by immunofluorescence to investigate the location of IDH1R132H expression.</p><p><b>RESULTS</b>(1) By IDH1 heterozygous somatic mutation analysis, Arg132His (c: G395A) was found in 31.6% (74 of 234) of the cases. IDH mutations were more frequent in oligoastrocytomas (9/13), anaplastic oligoastrocytomas (7/11), oligodendrogliomas(18/26, 69.2%), anaplastic oligodendrogliomas (8/10), and less frequent in diffuse astrocytomas (17/47, 36.2%), anaplastic astrocytomas (5/18), and glioblastomas (10/69, 14.5%). The mutation rate inversely correlated with the tumor grade in a linear fashion in astrocytic tumors (P = 0.007). Primary glioblastomas were characterized by a lower frequency of mutations than secondary glioblastomas (5/55 vs. 5/14, P = 0.036); IDH mutation was not detected in pilocytic astrocytoma and ependymoma. No IDH2 mutation was identified in this study cohort. (2) Immunohistochemistry of IDH1R132H demonstrated a strong cytoplasmic staining in 80 cases, which was highly correlated with IDH mutation status (P = 0.001). IDH1R132H was highly specific to tumor cells. (3) p53 immunostain was significantly correlated the IDH mutation in diffuse astrocytoma, anaplastic astrocytoma and secondary glioblastomas (P = 0.007, 0.026, 0.038 respectively). (4) No correlation between EGFR and IDH mutation was found.</p><p><b>CONCLUSIONS</b>High prevalence of IDH heterozygous somatic mutation occurs in the earlier stage of gliomas, which can be detected by mutation-specific antibody IDH1R132H. Furthermore, evaluation of p53 and EGFR expression combined with IDH mutation analysis may significantly aid in the diagnosis and differential diagnoses of gliomas in Chinese patients.</p>