Genomic and transcriptomic somatic alterations of hepatocellular carcinoma in non-cirrhotic livers

Background: Liver cancer is the second leading cause of cancer-related deaths worldwide. Hepatocellular carcinoma (HCC) risk factors include chronic hepatitis, cirrhosis, and alcohol abuse, whereby tumorigenesis is induced through inflammation and subsequent fibrotic response. However, a subset of HCC arises in non-cirrhotic livers. We characterized the genomic and transcriptomic landscape of non-cirrhotic HCC to identify features underlying the disease's development and progression. Methods: Whole genome and transcriptome sequencing was performed on 30 surgically resectable tumors comprised of primarily of non-cirrhotic HCC and adjacent normal tissue. Using somatic variants, capture reagents were created and employed on an additional 87 cases of mixed cirrhotic/non-cirrhotic HCC. Cases were analyzed to identify viral integrations, single nucleotide variants (SNVs), insertions and deletions (INDELS), copy number variants, loss of heterozygosity, gene fusions, structural variants, and differential gene expression. Results: We detected 3,750 SNVs/INDELS and extensive CNVs and expression changes. Recurrent TERT promoter mutations occurred in >52% of non-cirrhotic discovery samples. Frequently mutated genes included TP53, CTNNB1, and APOB. Cytochrome P450 mediated metabolism was significantly downregulated. Structural variants were observed at MACROD2, WDPCP, and NCKAP5 in >20% of samples. Furthermore, NR1H4 fusions involving gene partners EWSR1, GNPTAB, and FNIP1 were detected and validated in 2 non-cirrhotic samples. Conclusion: Genomic analysis can elucidate mechanisms that may contribute to non-cirrhotic HCC tumorigenesis. The comparable mutational landscape between cirrhotic and non-cirrhotic HCC supports previous work suggesting a convergence at the genomic level during disease progression. It is therefore possible genomic-based treatments can be applied to both HCC subtypes with progressed disease.

TERT Promoter Mutations Increase Sense and Antisense Transcription from the TERT Promoter

Background: Chief among mechanisms of telomerase reverse transcriptase (TERT) reactivation is the appearance of mutations in the TERT promoter. The two main TERT promoter mutations are C>T transitions located −146C>T and −124C>T upstream from the translational start site. They generate a novel Ets/TCF binding site. Both mutations are mutually exclusive and −124C>T is strikingly overrepresented in most cancers. We investigated whether this mutational bias and mutual exclusion could be due to transcriptional constraints. Methods: We compared sense and antisense transcription of a panel of TERT promoter-luciferase vectors harboring the −124C>T and -146C>T mutations alone or together. lncRNA TAPAS levels were measured by RT-PCR. Results: Both mutations generally increased TERT transcription by 2–4-fold regardless of upstream and downstream regulatory elements. The double mutant increased transcription in an additive fashion, arguing against a direct transcriptional constraint. The −146C>T mutation, alone or in combination with −124C>T, also unleashed antisense transcription. In line with this finding, lncRNA TAPAS was higher in cells with mutated TERT promoter (T98G and U87) than in cells with wild-type promoter, suggesting that lncRNA TAPAS may balance the effect of TERT promoter mutations. Conclusions: −146C>T and −124C>T TERT promoter mutations increase TERT sense and antisense transcription, and the double mutant features higher transcription levels. Increased antisense transcription may contain TERT expression within sustainable levels.

TERT Promoter Mutations and rs2853669 Polymorphism: Useful Markers for Clinical Outcome Stratification of Patients With Oral Cavity Squamous Cell Carcinoma

ObjectiveTo date, no useful prognostic biomarker exists for patients with oral squamous cell carcinoma (OCSCC), a tumour with uncertain biological behaviour and subsequent unpredictable clinical course. We aim to investigate the prognostic significance of two recurrent somatic mutations (-124 C>T and -146 C>T) within the promoter of telomerase reverse transcriptase (TERT) gene and the impact of TERT single nucleotide polymorphism (SNP) rs2853669 in patients surgically treated for OCSCC.MethodsThe genetic frequencies of rs2853669, -124 C>T and -146 C>T as well as the telomere length were investigated in 144 tumours and 57 normal adjacent mucosal (AM) specimens from OCSCC patients.ResultsForty-five tumours harboured TERT promoter mutations (31.3%), with -124 C>T and -146 C>T accounting for 64.4% and 35.6% of the alterations respectively. Patients with -124 C>T TERT promoter mutated tumours had the shortest telomeres in the AM (p=0.016) and showed higher risk of local recurrence (hazard ratio [HR]:2.75, p=0.0143), death (HR:2.71, p=0.0079) and disease progression (HR:2.71, p=0.0024) with the effect being potentiated by the co-occurrence of T/T genotype of rs2853669.Conclusion-124 C>T TERT promoter mutation as well as the T/T genotype of the rs2853669 SNP are attractive independent prognostic biomarkers in patients surgically treated for OCSCC, with the coexistence of these genetic variants showing a synergistic impact on the aggressiveness of the disease.

A Genetic Model for Central Chondrosarcoma Evolution Correlates with Patient Outcome

The treatment options for central chondrosarcoma are limited, and prognoses are generally unreliable. The presence and absence of mutations in IDH1, and IDH2 are defining events, and TERT mutations have been recently been associated with poor outcome. Despite this, molecular biomarkers are lacking. Here, analysing data from 356 patients, comprising results from whole genome sequencing (n=68), digital droplet PCR (n=346), and methylation arrays (n=57), we present a comprehensive genetic analysis of chondrosarcoma and suggest its clinical utility. Methylation profiles, TERT promoter mutations, genome doubling with prior haploidisation, and age at diagnosis of high grade, distinguish IDH1-mutant, IDH2-mutant and IDH wildtype tumours. The majority of IDH2-mutant tumours harbour TERT mutations, though a significant reduction in survival is only found in the less common mutational combination of IDH1 and TERT. We suggest that diagnostic testing for IDH1, IDH2 and TERT mutations could guide clinical monitoring and prognostication.

BIOM-21. THE SIGNIFICANCE OF TERT PROMOTER MUTATIONS, TELOMERE LENGTH AND MGMT PROMOTER METHYLATION IN NEWLY DIAGNOSED AND RECURRENT IDH-WILDTYPE GLIOBLASTOMA (GBM): A LARGE MONO-INSTITUTIONAL STUDY

BACKGROUND the significance of TERT promoter mutations, telomere length and their interactions with MGMT methylation status in patients with IDH-wildtype GBM patients remain unclear. We performed a monoinstitutional study to better investigate their impact and their interaction on clinical outcomes. METHODS TERTmutations (C228T and C250T), relative telomere length (RTL) and MGMT methylation were assessed in 278 newly-diagnosed and in 65 recurrent IDH-wildtype GBM PTS which were treated from Dec2016 to Jan2020. We explored association between gene characteristics and neuroradiological response, PFS, OS. Telomere length was measured by monochrome multiplex PCR and RTL values were calculated as a telomere/single-copy gene ratio. RESULTS characteristics of newly diagnosed GBM PTS were: median age 63 ys, ECOG PS0-1 in 71% of PTS, radical surgery in 38%, 78% received radiation therapy plus TMZ, MGMTmet in 53%, TERT promoter was mutated in 80% (75% C228T, 25% C250T), median RTL was 1.57 (range 0.4-11.37). ORR was reported in 15% of PTS, medianOS was 15 ms (95% CI 13-18 ms), medianPFS was 8 ms (95% CI 7-9 ms). At multivariable analysis, TERT mutations and RTL were not associated with clinical outcomes; about OS, TERT mutations and RTL reported a HR of 1.05 (95% CI 0.64-1.64) and 0.99 (95% CI 0.89-1.10), respectively; MGMTmet tumors showed significant improved PFS and OS with a HR of 0.54(95% CI 0.40-0.71) and 0.47 (95% CI 0.34-0.64), respectively. All interactions among MGMT-status, TERT-mutation status and RTL were not statistically significant. Characteristics of recurrent GBM PTS were: median age 55 ys, ECOG PS0-1 in 60% of PTS, MGMTmet in 37%, TERT mutations in 75% (75% C228T, 25% C250T), RTL was 1.67 (range 0.68-8.87). At multivariable analysis, only MGMTmet tumors resulted significantly associated to prolonged OS(HR0.16;95%CI0.07-0.40). No gene interaction was significant. CONCLUSIONS we analyzed the impact of TERT mutations, RTL and MGMT in newly diagnosed and recurrent IDH-wildtype GBM PTS. TERT status and RTL were not associated with clinical outcomes. MGMT was the only prognostic factor. No significant interaction was demonstrated between TERT mutations, RTL and MGMT

PATH-41. POLYMORPHOUS LOW-GRADE NEUROEPITHELIAL TUMOR OF THE YOUNG WITH FGFR3-TACC3 FUSION MIMICKING HIGH-GRADE GLIOMA: CASE REPORT AND SERIES OF HIGH-GRADE CORRELATES

BACKGROUND Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently-described entity that can occasionally histologically and molecularly mimic high-grade glioma. The histologic and molecular features that predict aggressive behavior in FGFR3-TACC3 altered tumors are unclear. CASES We present a rare case of an indolent neuroepithelial neoplasm in a 59-year-old female with imaging initially suggestive of high-grade glioma and analyze common molecular features between this case and a series of high-grade gliomas. After total resection, pathology of the case patient revealed predominantly low-grade cytomorphology, abundant microcalcifications, unusual neovascularization, and a low proliferation index. The lesion was diffusely CD34 immunoreactive and harbored both an FGFR3-TACC3 fusion and a TERT promoter mutation. Based on the overall histologic and molecular profile, a diagnosis of PLNTY was favored. The patient was thereafter observed without adjuvant therapy with no evidence of progression at 15-month follow-up. In contrast, a series of eight adult patients with glioblastomas harboring FGFR3-TACC3 fusions and correspondingly aggressive clinical courses are also presented. Common molecular findings included IDH-wildtype status, absence of 1p19q codeletion, and CDKN2A loss. TERT promoter mutations and lack of MGMT promoter methylation were also frequently observed. These patients demonstrated a median 15-month overall survival and a 6-month progression-free survival. CONCLUSIONS PLNTY is a rare low-grade entity that can display characteristics of high-grade glioma, particularly in adults. The potential for a unique entity mimicking PLNTY which may act as a precursor lesion for a more malignant phenotype should be considered in cases with FGFR3-TACC3 fusions and other high-grade features.