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Proteomic analysis of transitional cell carcinoma-like variant of tubo-ovarian high-grade serous carcinoma.

ABSTRACT: The current World Health Organization classification does not distinguish transitional cell carcinoma of the ovary (TCC) from conventional tubo-ovarian high-grade serous carcinoma (HGSC), despite evidence suggesting improved prognosis for patients with TCC; instead, it is considered a morphologic variant of HGSC. The immunohistochemical (IHC) markers applied to date do not distinguish between TCC and HGSC. Therefore, we sought to compare the proteomic profiles of TCC and conventional HGSC to identify proteins enriched in TCC. Prognostic biomarkers in HGSC have proven to be elusive, and our aim was to identify biomarkers of TCC as a way of reliably and reproducibly identifying patients with a favorable prognosis and better response to chemotherapy compared with those with conventional HGSC. Quantitative global proteome analysis was performed on archival material of 12 cases of TCC and 16 cases of HGSC using SP3 (single-pot, solid phase-enhanced, sample preparation)-Clinical Tissue Proteomics, a recently described protocol for full-proteome analysis from formalin-fixed paraffin-embedded tissues. We identified 430 proteins that were significantly enriched in TCC over HGSC. Unsupervised co-clustering perfectly distinguished TCC from HGSC based on protein expression. Pathway analysis showed that proteins associated with cell death, necrosis, and apoptosis were highly expressed in TCCs, whereas proteins associated with DNA homologous recombination, cell mitosis, proliferation and survival, and cell cycle progression pathways had reduced expression. From the proteomic analysis, three potential biomarkers for TCC were identified, claudin-4 (CLDN4), ubiquitin carboxyl-terminal esterase L1 (UCHL1), and minichromosome maintenance protein 7 (MCM7), and tested by IHC analysis on tissue microarrays. In agreement with the proteomic analysis, IHC expression of those proteins was stronger in TCC than in HGSC (p < 0.0001). Using global proteomic analysis, we are able to distinguish TCC from conventional HGSC. Follow-up studies will be necessary to confirm that these molecular and morphologic differences are clinically significant.

SUBMITTER: Tessier-Cloutier B

PROVIDER: S-EPMC8204941 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:While TP53 mutation is widely considered to be a defining feature of tubo-ovarian high-grade serous carcinoma (HGSC), rare TP53-mutation-negative cases have been reported. To gain further insight into this rare subset, a retrospective review was conducted on 25 TP53-wildtype tubo-ovarian HGSCs, constituting 2.5% of 987 HGSCs profiled by the MSK-IMPACT sequencing platform. Consistent with serous differentiation, positive staining for Pax8 and WT1 was present in virtually all TP53-wildtype HGSCs. Other characteristic features of HGSC, such as serous tubal intraepithelial carcinoma, or genetic alterations of CCNE1 and BRCA1/2 were identified in these tumors, furthering supporting their classification as bona fide HGSC, despite lacking TP53 mutations. Overall, the level of chromosomal instability of TP53-wildtype HGSCs was intermediate between low-grade serous carcinoma (LGSC) and TP53-mutated HGSC. Morphologic assessment by observers blinded to mutation status revealed a significant subset of tumors with Grade 2 nuclear atypia (which exceeds the degree of atypia allowed for LGSC, but less than typically encountered for HGSC) combined with micropapillary features (6/19, 32%, chemotherapy-naive TP53-wildtype HGSCs compared to 0/21, 0%, TP53-mutated HGSCs; p = 0.007). Some TP53-wildtype HGSCs harbored driver mutations in KRAS (n = 3), BRAF (n = 1) or NRAS (n = 2). Overall, 10 (40%) cases had "LGSC-like" morphology (i.e., Grade 2 nuclear atypia and micropapillary features) and/or RAS/RAF mutation, and most of these showed a wildtype p53 pattern of expression by immunohistochemistry (7/9, 78%). The remaining TP53-wildtype HGSCs (n = 15, 60%) exhibited severe nuclear atypia (Grade 3) and were morphologically indistinguishable from conventional TP53-mutated HGSC. Despite lacking genetic alterations of TP53, these "usual HGSC-like" tumors often showed evidence of p53 dysfunction, including downregulation of expression ('null' or equivocal p53 staining in 9/14, 64%) or MDM2 amplification (n = 2). Our results support the existence of TP53-wildtype HGSCs, which comprise a heterogeneous group of tumors which may arise via distinct pathogenic mechanisms.

Project description:CCNE1 amplification is a recurrent alteration associated with unfavourable outcome in tubo-ovarian high-grade serous carcinoma (HGSC). We aimed to investigate whether immunohistochemistry (IHC) can be used to identify CCNE1 amplification status and to validate whether CCNE1 high-level amplification and overexpression are prognostic in HGSC. A testing set of 528 HGSC samples stained with two optimised IHC assays (clones EP126 and HE12) was subjected to digital image analysis and visual scoring. DNA and RNA chromogenic in situ hybridisation for CCNE1 were performed. IHC cut-off was determined by receiver operating characteristics (ROC). Survival analyses (endpoint ovarian cancer specific survival) were performed and validated in an independent validation set of 764 HGSC. Finally, combined amplification/expression status was evaluated in cases with complete data (n = 1114). CCNE1 high-level amplification was present in 11.2% of patients in the testing set and 10.2% in the combined cohort. The optimal cut-off for IHC to predict CCNE1 high-level amplification was 60% positive tumour cells with at least 5% strong staining cells (sensitivity 81.6%, specificity 77.4%). CCNE1 high-level amplification and overexpression were associated with survival in the testing and validation set. Combined CCNE1 high-level amplification and overexpression was present in 8.3% of patients, mutually exclusive to germline BRCA1/2 mutation and significantly associated with a higher risk of death in multivariate analysis adjusted for age, stage and cohort (hazard ratio = 1.78, 95 CI% 1.38-2.26, p < 0.0001). CCNE1 high-level amplification combined with overexpression identifies patients with a sufficiently poor prognosis that treatment alternatives are urgently needed. Given that this combination is mutually exclusive to BRCA1/2 germline mutations, a predictive marker for PARP inhibition, CCNE1 high-level amplification combined with overexpression may serve as a negative predictive test for sensitivity to PARP inhibitors.

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Proteomic analysis of transitional cell carcinoma-like variant of tubo-ovarian high-grade serous carcinoma.

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