Molecular Profiling of Endometrial Cancer: An Exploratory Study in Aotearoa, New Zealand

Background: Aotearoa, New Zealand, has one of the fastest-rising rates of endometrial cancer (EC) worldwide, increasing particularly in younger Māori and Pasifika women. There is a move towards using molecular profiling to direct treatment for each EC subtype. Aim: This study aimed to explore the molecular profiling of primary EC tissue in Aotearoa. Methods: We used the PORTEC guidelines for the molecular subtyping of 90 patients’ samples into four categories: POLE-mutated, p53 abnormal, mismatch repair deficient (MMRd) and no specific molecular profile (NSMP). The CTNNB1 mutation and L1CAM expression were also included in the analysis. POLE and CTNNB1 mutations were analysed using targeted next-generation sequencing (NGS). Novel mutations were assessed using VarSome. MMRd, L1CAM and p53 abnormalities were analysed using immunohistochemistry. Results: In total, 15 samples were MMRd, 9 were p53 abnormal, 8 were POLE-mutated and the rest (56) were NSMP. Eleven samples had exon 3 CTNNB1 mutations and eleven novel POLE mutations were described. Conclusion: Surrogate markers for POLE mutations should be investigated. The validation of POLE variants and CTNNB1 mutations as part of an Aotearoa-based molecular panel is warranted.

Tertiary lymphoid structures critical for prognosis in endometrial cancer patients - a TransPORTEC study

B-cells play a key role in cancer suppression, particularly when aggregated in tertiary lymphoid structures (TLS). Here, we investigated the role of B-cells and TLS in endometrial cancer (EC). Single cell RNA-sequencing of B-cells showed presence of activated/memory B-cells, cycling/germinal center B-cells and antibody-secreting cells. Differential gene expression analysis showed association of TLS with L1CAM overexpression. Immunohistochemistry and co-immunofluorescence showed L1CAM expression in mature TLS localized in the myometrial wall or at the tumor invasive border, independent of L1CAM expression the tumor. Using L1CAM as a marker, 378 of the 411 molecularly classified ECs from the PORTEC-3 biobank were evaluated. TLS were found in 19%, predominantly in mismatch-repair deficient and polymerase-epsilon mutant EC. Multivariable Cox regression analysis showed strong favorable prognostic impact of TLS, independent of clinicopathological and molecular factors. Our data suggests a pivotal role of TLS in outcome of EC patients, and establishes L1CAM as a simple biomarker.Statement of significance Tertiary lymphoid structures have a pivotal role in the immune response against endometrial cancer. Presence of mature tertiary lymphoid structures can be easily assessed using L1CAM immunohistochemistry and has independent favorable predictive value for recurrence and endometrial cancer-specific survival.

LINC-29. IMPACT OF RELA FUSION ON OUTCOMES OF CHILDHOOD SUPRATENTORIAL EPENDYMOMAS (ST-EPEN)

BACKGROUND Ependymomas are heterogenous group of tumours with variable clinical course and diverse molecular features. RELA fusion status has been reported to have prognostic impact in ST-EPEN. Our retrospective study analysed the prevalence and clinical impact of RELA fusion in childhood ST-EPEN at our centre. STUDY METHODS FFPE tissues of all childhood ST-EPEN diagnosed during 2011–2017 were evaluated for RELA fusion 1/2 by RT-PCR. Children were treated as per guidelines by the Neuro-oncology multidisciplinary team. Outcomes were correlated with RELA fusion, histological features and immunohistochemical parameters(L1CAM expression and Mib-1 index). Only patients with therapy details were included. RESULTS A total of 37 patients(0–50 years) with ST-EPEN were included(median age-10.2 years; boy:girl ratio-1.4:1)for analysis. Histological grade II, II/III and III was seen in 4(11%),2(5%) and 31(84%) patients respectively. Mib-1 index was assessable in 33 patients of which, 9 patients (24%) had a Mib-1 index >20%. RELA fusion was detected in 13(35%)tumors. The 3-year and 5-year EFS/OS of the overall cohort was 64.2%/83.6% and 60.1%/73.1% respectively. The 3-year/5-year EFS of RELA-positive tumors was inferior compared to RELA-negative tumours (53.8%/36% v/s 62.6%/53.6%; p=0.391). The 3-year/5-year EFS of tumors expressing L1CAM versus negative-expression was comparable (61.1%/55%v/s59.8%/47.9%;p=0.44). Presence of Mib-1>20% correlated with inferior survival (5-year EFS:81.1%vs22.2%; p<0.01). CONCLUSIONS ST-EPEN with RELA fusion had trend towards increased relapse/progression. High Mib-1 correlated with poor survival. RELA fusion status needs to be studied in a larger cohort prospectively to confirm its clinical impact.

Harmonization of L1CAM expression facilitates axon outgrowth and guidance of a motor neuron

ABSTRACTBrain development requires precise regulation of axon outgrowth, guidance and termination by multiple signaling and adhesion molecules. How the expression of these neurodevelopmental regulators is transcriptionally controlled is poorly understood. The Caenorhabditis elegans SMD motor neurons terminate axon outgrowth upon sexual maturity and partially retract their axons during early adulthood. Here we show that C-terminal binding protein 1 (CTBP-1), a transcriptional corepressor, is required for correct SMD axonal development. Loss of CTBP-1 causes multiple defects in SMD axon development: premature outgrowth, defective guidance, delayed termination and absence of retraction. CTBP-1 controls SMD axon guidance by repressing the expression of SAX-7, an L1 cell adhesion molecule (L1CAM). CTBP-1-regulated repression is crucial because deregulated SAX-7/L1CAM causes severely aberrant SMD axons. We found that axonal defects caused by deregulated SAX-7/L1CAM are dependent on a distinct L1CAM, called LAD-2, which itself plays a parallel role in SMD axon guidance. Our results reveal that harmonization of L1CAM expression controls the development and maturation of a single neuron.

L1CAM Expression in Recurrent Estrogen Positive/HER2 Negative Breast Cancer

Background: We investigate L1CAM expression in ER positive/HER2 negative breast carcinomas. The finding of a potential correlation between high L1CAM expression and recurrent/metastatic disease in luminal A and B breast carcinomas may be helpful for risk stratification and open opportunities for targeted therapies.Methods: 304 cases comprising 152 cases of ER positive, PR positive/negative and HER2 negative recurrent/metastatic breast carcinomas and 152 non-recurrent controls were included. ER, PR, HER-2, Ki-67 status, Nottingham grade, tumor size, tumor stage, number of foci, lymph node status, lymphovascular invasion, phenotype, laterality, age at diagnosis and first distant or local recurrence were recorded. Results: L1CAM positive cases showed increased specificity for recurrence and these patients were significantly younger than L1CAM negative ones. Compared to L1CAM negative recurrent cases, L1CAM positive ones had a noticeably higher Ki-67, tended to be larger and recurred sooner. All L1CAM positive recurrent/metastatic cases were of the luminal B subtype compared to 67.3% of the L1CAM negative cases. Conclusions: L1CAM is highly specific for recurrence in a subset of breast cancer patients and may be associated with more aggressive behavior, particularly in luminal B breast cancers with higher Ki-67 expression. Further investigation about the prognostic value of L1CAM is warranted.