Coexisting FGFR3 p.K650T mutation in two FGFR3-TACC3 fusion glioma cases

Clinico-pathological and epigenetic heterogeneity of diffuse gliomas with FGFR3::TACC3 fusion

BACKGROUND

Gliomas with FGFR3::TACC3 fusion mainly occur in adults, display pathological features of glioblastomas (GB) and are usually classified as glioblastoma, IDH-wildtype. However, cases demonstrating pathological features of low-grade glioma (LGG) lead to difficulties in classification and clinical management. We report a series of 8 GB and 14 LGG with FGFR3:TACC3 fusion in order to better characterize them.

METHODS

Centralized pathological examination, search for TERT promoter mutation and DNA-methylation profiling were performed in all cases. Search for prognostic factors was done by the Kaplan-Meir method.

RESULTS

TERT promoter mutation was recorded in all GB and 6/14 LGG. Among the 7 cases with a methylation score > 0.9 in the classifier (v12.5), 2 were classified as glioblastoma, 4 as ganglioglioma (GG) and 1 as dysembryoplastic neuroepithelial tumor (DNET). t-SNE analysis showed that the 22 cases clustered into three groups: one included 12 cases close to glioblastoma, IDH-wildtype methylation class (MC), 5 cases each clustered with GG or DNET MC but none with PLNTY MC. Unsupervised clustering analysis revealed four groups, two of them being clearly distinct: 5 cases shared age (< 40), pathological features of LGG, lack of TERT promoter mutation, FGFR3(Exon 17)::TACC3(Exon 10) fusion type and LGG MC. In contrast, 4 cases shared age (> 40), pathological features of glioblastoma, and were TERT-mutated. Relevant factors associated with a better prognosis were age < 40 and lack of TERT promoter mutation.

CONCLUSION

Among gliomas with FGFR3::TACC3 fusion, age, TERT promoter mutation, pathological features, DNA-methylation profiling and fusion subtype are of interest to determine patients' risk.

Infiltrating gliomas with FGFR alterations: Histologic features, genetic alterations, and potential clinical implications

BACKGROUND

Fibroblast growth factor receptors (FGFRs) are frequently altered in cancers and present a potential therapeutic avenue. However, the type and prevalence of FGFR alterations in infiltrating gliomas (IGs) needs further investigation.

OBJECTIVE

To understand the prevalence/type of FGFR alterations in IGs.

METHODS

We reviewed clinicopathologic and genomic alterations of FGFR-mutant gliomas in a cohort of 387 patients. Tumors were examined by DNA next-generation sequencing for somatic mutations with a panel interrogating 205-genes. For comparison, cBioPortal databases were queried to identify FGFR-altered IGs.

RESULTS

Fourteen patients (3.6%) with FGFR-mutant tumors were identified including 11 glioblastomas, Isocitrate dehydrogenase (IDH) - wildtype (GBM-IDH-WT), 2 oligodendrogliomas, and 1 astrocytoma IDH-mutant. FGFR-altered IGs showed endocrinoid capillaries, microvascular proliferation, necrosis, oligodendroglioma-like cells, fibrin thrombi, microcalcifications, and nodular growth. FGFR3 was the most commonly altered FGFR gene (64.3%). The most common additional mutations in FGFR-altered IGs were TERTp, CDKN2A/B, PTEN, CDK4, MDM2, and TP53. FGFR3 alterations were only observed in GBM-IDH-WT. EGFR alterations were rarely identified in FGFR3-altered gliomas.

CONCLUSIONS

Histologic features correlate with FGFR alterations in IGs. FGFR3-TACC3 fusion and FGFR3 amplification are the most common FGFR alterations in IGs. FGFR alterations are a rare, but potentially viable, therapeutic target in asubset of IGs.

Extra-CNS and dural metastases in FGFR3::TACC3 fusion+ adult glioblastoma, IDH-wildtype

BACKGROUND

Adult glioblastomas (GBMs), IDH-wildtype, WHO grade 4 with FGFR3::TACC3 fusion have a better prognosis than standard GBMs. Whether this extended survival leads to late biological consequences is unknown. Although constituting only 4% of all GBMs, FGFR3::TACC3 fusion-positive GBMs manifest recurrent morphological features that allow prediction of this subtype, possibly affecting trial eligibility and/or targeted therapies. However, we have previously shown that an identical histological pattern can be present in wildtype examples, and conversely, occasional FGFR3::TACC3 fusion-positive tumors lack this stereotypic morphology; thus, ultimately molecular characterization is required. We now report for the first time an adult with FGFR3::TACC3 fusion-positive GBM showing archetypal histological features who developed extracranial metastases to provide further insight into potential behavior of the GBM type.

METHODS

Report of a 70-year-old man with left parietal GBM who developed 2 subsequent metastases, all 3 of which were assessed by next-generation sequencing (NGS) and DNA methylation.

RESULTS

Biopsy-proven dural metastases occurred at 8 months and cervical lymph node metastasis at 12-month post-diagnosis before the patient succumbed at 23 months. By NGS, all 3 tumors showed FGFR3::TACC3 fusion as well as an additional PDZD2::TERT fusion of uncertain significance. DNA methylation profiling demonstrated mesenchymal subtype in the initial biopsy and RTKII subtype in subsequent dural and lymph node metastases, indicating intratumor spatial heterogeneity or temporal evolution.

CONCLUSION

Rarely, FGFR3::TACC3 fusion-positive GBM patients may develop dural and extracranial metastatic spread, the latter with subclass switching on epigenomic analysis.

Glioblastoma, IDH-Wild Type With FGFR3-TACC3 Fusion: When Morphology May Reliably Predict the Molecular Profile of a Tumor. A Case Report and Literature Review

It has been reported that in-frame FGFR3-TACC3 fusions confer to glioblastomas, IDH-wild type (GBMs, IDHwt) some unusual morphologic features, including monomorphous rounded cells with ovoid nuclei, nuclear palisading, endocrinoid network of “chicken-wire” vessels, microcalcifications and desmoplastic stroma, whose observation may predict the molecular profile of the tumor. We herein present a case of recurrent GBMs, IDHwt, exhibiting some of the above-mentioned morphological features and a molecularly-proven FGFR3-TACC3 fusion. A 56-year-old man presented to our hospital for a recurrent GBM, IDHwt, surgically treated at another center. Histologically, the tumor, in addition to the conventional GBM morphology, exhibited the following peculiar morphologic features: (1) monomorphous neoplastic cells with rounded nuclei and scant pale cytoplasm; (2) thin capillary-like vessels with “chicken-wire” pattern; (3) nuclear palisading; (4) formation of vague perivascular pseudorosettes; (5) spindled tumor cells embedded in a loose, myxoid background. Based on this unusual morphology, molecular analyses were performed and an FGFR3 exon17-TACC3 exon 10 fusion was found. The present case contributes to widening the morphologic spectrum of FGFR3-TACC3-fused GBM, IDHwt and emphasizes that pathologists, in the presence of a GBM, IDHwt with unconventional morphology, should promptly search for this fusion gene.

HSP90-CDC37 functions as a chaperone for the oncogenic FGFR3-TACC3 fusion

The FGFR3-TACC3 (F3-T3) fusion gene was discovered as an oncogenic molecule in glioblastoma and bladder cancers, and has subsequently been found in many cancer types. Notably, F3-T3 was found to be highly expressed in both untreated and matched recurrence glioblastoma under the concurrent radiotherapy and temozolomide (TMZ) treatment, suggesting that targeting F3-T3 is a valid strategy for treatment. Here, we show that the F3-T3 protein is a client of heat shock protein 90 (HSP90), forming a ternary complex with the cell division cycle 37 (CDC37). Deprivation of HSP90 or CDC37 disrupts the formation of the ternary complex, which destabilizes glycosylated F3-T3, and thereby suppresses F3-T3 oncogenic activity. Gliomas harboring F3-T3 are resistant to TMZ chemotherapy. HSP90 inhibitors sensitized F3-T3 glioma cells to TMZ via the inhibition of F3-T3 activation and potentiated TMZ-induced DNA damage. These results demonstrate that F3-T3 oncogenic function is dependent on the HSP90 chaperone system and suggests a new clinical option for targeting this genetic aberration in cancer.

Case Report: Identification of Multiple TERT and FGFR2 Gene Fusions in a Pineal Region Glioblastoma Case

As an oncogenic somatic variant, telomerase reverse transcriptase promoter (TERTp) mutations are frequently observed in adult glioblastoma (GBM). Alternatively, we report the first case of glioblastoma with TERT amplification accompanied by multiple TERT and FGFR2 gene fusions instead of TERTp mutation. A 55-year-old woman presented with dizziness, headache, and diplopia for three weeks. Magnetic resonance imaging (MRI) demonstrated a heterogeneously enhancing lobulated mass centered in the pineal region. Partial tumor resection and ventriculoperitoneal shunt were achieved, and the residual tumor was then treated with standard radiation. The tumor was diagnosed as GBM, IDH-wild type, WHO grade IV, and the Ki67 proliferation index was high (30–40%). Intriguingly, TERT amplification without TERTp mutation was identified via next generation sequencing (NGS). Further analysis revealed multiple TERT (TERT–NUBPL, MARCH6–TERT, and CJD4–TERT) and FGFR2 (CXCL17–FGFR2, SIPA1L3–FGFR2, FGFR2–SIPA1L3, and FGFR2–CEACAM1) gene fusions. After the surgery, the patient’s condition deteriorated rapidly due to the malignant nature of the tumor and she died with an overall survival of 3 months. Our report provides the molecular clue for a novel telomerase activation and maintenance mechanism in GBM.

FGFR3 overexpression is a useful detection tool for FGFR3 fusions and sequence variations in glioma

Background

Fibroblast growth factor receptor (FGFR) inhibitors are currently used in clinical development. A subset of glioblastomas carries gene fusion of FGFR3 and transforming acidic coiled-coil protein 3. The prevalence of other FGFR3 alterations in glioma is currently unclear.

Methods

We performed RT-PCR in 101 glioblastoma samples to detect FGFR3-TACC3 fusions ("RT-PCR cohort") and correlated results with FGFR3 immunohistochemistry (IHC). Further, we applied FGFR3 IHC in 552 tissue microarray glioma samples ("TMA cohort") and validated these results in two external cohorts with 319 patients. Gene panel sequencing was carried out in 88 samples ("NGS cohort") to identify other possible FGFR3 alterations. Molecular modeling was performed on newly detected mutations.

Results

In the "RT-PCR cohort," we identified FGFR3-TACC3 fusions in 2/101 glioblastomas. Positive IHC staining was observed in 73/1024 tumor samples of which 10 were strongly positive. In the "NGS cohort," we identified FGFR3 fusions in 9/88 cases, FGFR3 amplification in 2/88 cases, and FGFR3 gene mutations in 7/88 cases in targeted sequencing. All FGFR3 fusions and amplifications and a novel FGFR3 K649R missense mutation were associated with FGFR3 overexpression (sensitivity and specificity of 93% and 95%, respectively, at cutoff IHC score > 7). Modeling of these data indicated that Tyr647, a residue phosphorylated as a part of FGFR3 activation, is affected by the K649R mutation.

Conclusions

FGFR3 IHC is a useful screening tool for the detection of FGFR3 alterations and could be included in the workflow for isocitrate dehydrogenase (IDH) wild-type glioma diagnostics. Samples with positive FGFR3 staining could then be selected for NGS-based diagnostic tools.

Targeted Therapy with Anlotinib for a Patient with an Oncogenic FGFR3-TACC3 Fusion and Recurrent Glioblastoma

We describe a case of recurrent glioblastoma treated with anlotinib in this report. The patient was administered anlotinib 12 mg p.o. once every day (days 1-14, with a 21-day cycle) (anlotinib clinical study NCT04004975) and oral temozolomide chemotherapy 100 mg/m² (days 1-7, days 15-21, 28-day cycle; 12 cycles). After 2 months of therapy, the patient achieved a partial response that has been maintained for >17 months of follow-up. Molecular characterization confirmed the presence of a TERT promoter mutation, wild-type IDH1/2, an FGFR3-TACC3 fusion, and FGFR3 amplification in the patient. Anlotinib is a multitarget tyrosine kinase inhibitor that was originally designed to inhibit VEGFR2/3, FGFR1-4, PDGFRα/β, and c-Kit. Patients with TERT promoter mutations and high-grade IDH-wild-type glioma have shorter overall survival than patients with IDH-wild-type glioma without TERT promoter mutations. However, this patient had a favorable clinic outcome, and FGFR3-TACC3 fusion may be a new marker for treatment of glioma with anlotinib. KEY POINTS: This case study is believed to be the first report that FGFR3-TACC3 fusion could be a novel indication to treat recurrent glioblastoma with the drug anlotinib. This case exhibited an exceptional response (maintained partial response >17 months) after 2-month combined therapy of anlotinib and oral temozolomide chemotherapy. This case also underscores the importance of molecular diagnosis for clinically complex cases. Tumor tissue-based assessment of molecular biomarkers in brain tumors has been successfully translated into clinical application.

LncRNA CCAT2 promotes angiogenesis in glioma through activation of VEGFA signalling by sponging miR-424

Glioma is characterized by high morbidity, high mortality and poor prognosis. Recent studies exhibited that lncRNA CCAT2 is overexpressed in glioma and promotes glioma progression, but the specific molecular biological mechanism remains to be determined. We performed qRT-PCR to evaluate the expression of related genes, Western blotting analysis to measure protein levels, colony formation assay to detect the proliferative ability of glioma cells, flow cytometry to measure cell apoptosis, bioinformatics analysis and dual luciferase assay to verify the binding sites and the targeted regulatory relationship in A172 and U251 cell lines and tube formation assay to determine endothelial angiogenesis. LncRNA CCAT2 and VEGFA were highly expressed, while miR-424 was expressed at low levels in NHA cells. Furthermore, knockdown of lncRNA CCAT2 decreased cell proliferation, increased cell apoptosis and inhibited endothelial angiogenesis in glioma. Moreover, lncRNA CCAT2 shared a complementary sequence with miR-424 which in turn directly bound to the 3'-UTR of VEGFA. Further investigation indicated that lncRNA CCAT2 promoted cell proliferation and endothelial angiogenesis by inducing the PI3K/AKT signalling pathway in glioma. The oncogenic lncRNA CCAT2 is highly associated with the development of glioma and exerts its function by upregulating VEGFA via miR-424.