ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 found. Globally, 14 subtypes of KRAS mutations were detected, the most common being G12C (103, 31.79%), G12V (79, 24.38%), and G12D (45, 13.89%). Conclusion: KRAS mutations occurred in 23.9% of the patients enrolled in the study, and KRAS G12C was the most common one, detected in 103 patients (7.6%); these figures are slightly lower in comparison to those reported for other Caucasian populations. PS-15-006 Increased expression of the CST2 gene is associated with lym- phatic dissemination of prostate cancer V. Pavlov*, E. Pudova, A. Kobelyatskaya, A. Snezhkina, I. Katunina, K. Nyushko, D. Kalinin, K. Sergey, M. Fedorova, G. Krasnov, A. Kudryavtseva *Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia Background & objectives: Locally advanced prostate cancer (LAPC) is characterized by invasion of the prostatic capsule, in which lymphatic dissemination is also frequently observed. For this category of patients, the search for reliable prognostic markers for choosing further treat- ment tactics is especially relevant. Methods: Total RNA was obtained from 73 LAPC samples, from which libraries were prepared and RNA-Seq on the Illumina platform was performed. Differential expression analysis was performed between samples with (N1 group) and without lymphatic dissemination (N0 group) in R (edgeR). Validation of gene expression was performed by qPCR on an independent sample of LAPC patients based on 37 FFPE samples. Results: According to the obtained RNA-Seq data bioinformatic analysis results, a statistically significant increase in the differen- tial expression of the CST2 gene in the N1 group by 3.27 times was found (LogFC = 1.71; FDR-value QLF test = 0.01). Spear- man’s rank correlation analysis showed a correlation between CST2 gene expression and lymphatic dissemination (rs=0.47; p-value = 0.00009). Based on the results of CST2 gene relative expression validation in an independent sample of LAPC patients, a statisti- cally significant increase in expression in the N1 group by 3.24 times (p-value = 0.002) was also confirmed. Conclusion: Thus, based on the study, it was shown that an increased level of CST2 gene expression is statistically signifi- cantly associated with lymphatic dissemination and can be consid- ered as a potential prognostic marker in prostate cancer. This research was financially supported by the Russian Science Foundation, grant 18-75-10127. PS-15-007 NTRK fusion genes in cholangiocarcinoma T. Vesterinen*, S. Boyd, S. Kytölä, J. Arola *HUS Diagnostic Center, HUSLAB, Helsinki University Hospital and University of Helsinki, Finland Background & objectives: Cholangiocarcinoma (CCA) is an uncom- mon and aggressive adenocarcinoma with poor long-term survival. As current treatment options for CCA patients are restricted and systemic, new therapies are urgently needed. Here we studied if NTRK fusion genes exist in CCAs. Methods: CCA cohort retrieved from Helsinki Biobank (Finland) included 93 primary CCAs and 25 metastatic samples. Tumours were histologically re-evaluated, processed into TMAs and labelled with pan-TRK antibody (clone EPR17341, Roche Tissue Diagnos- tics, Tucson, AZ). Tumours expressing TRK were further analysed with Idylla GeneFusion Assay (Biocartis, Mechelen, Belgium) and FusionPlex Comprehensive Thyroid and Lung (CTL) panel (Invitae Corporation, San Francisco, CA). Results: Altogether 9 primary tumours showed TRK expres- sion in immunohistochemistry (IHC), indicating putative NTRK fusion. Metastatic samples showed no expression. The amount of TRK positive cells was low with an average value of 15 cells per tumour (median 4, range 1-100). In 7 of the tumours the expression was nuclear and 2 tumours showed cytoplasmic expression. Real-time RT-PCR-based Idylla GeneFusion Assay was performed to all 9 tumours. It identified NTRK3 expression imbalance in the tumour with cytoplasmic TRK expression. No other fusions were detected. Next-generation sequencing (NGS)- based FusionPlex CTL panel was performed for 8 tumours. No NTRK fusions were detected. Conclusion: We identified NTRK3 expression imbalance in one (1.1%) of 93 CCA tumours but this could not be confirmed with NGS. Our results show limited specificity of pan-TRK IHC to identify NTRK fusions. Pan-TRK IHC can thus be utilized as a screening technique for NTRK fusions in CCA, but positive samples require confirmatory testing with RNA-based methods. As there is a tumour agnostic oncological treatment for patients with an NTRK fusion, also CCA patients should be screened for this gene rearrangement. Funding: This work was supported by the Cancer Foundation Finland [no grant number], the Helsinki University Hospital Research Fund [grant number TYH2019205] and Bayer Oy. PS-15-008 Analysis of PINK1 immunoexpression in primary lung ade- nocarcinomas revealed a group of patients with a poorer prognosis I. Fernandez-Vega*, D. Corte-Torres, A. Vallina, J.C. Celis Pinto, M. Rubiera, S. Fernández Menéndez, K.M. Piña Batista *Hospital Universitario Central de Asturias; Universidad de Oviedo, Faculty of Medicine, Spain Background & objectives: In lung adenocarcinoma, high PINK1 expression was correlated with poor response to chemotherapy. Our aim was to study the immunoexpression of PINK1 in samples from lung adenocarcinoma and their respective brain metastases and its pos- sible clinical relevance. Methods: Twenty-six consecutive patients with lung adenocarcinoma and subsequent brain metastasis surgically removed between 2007 and 2019 were studied. Tissue arrays were produced using a 2 mm diameter needle. Immunohistochemical studies were conducted and analysed by the H-Score method. Statistical analysis of these findings was carried out using the SPSSv25; p<0.05 program. Results: Positive immunoexpression for PINK1 was detected in more than 90% of both primary tumours and their brain metastasis without significant differences (70,91 ± 43,46 vs 77,61 ± 43,69; p= 0,565). More than 80 points of PINK1 immunoexpression in primary lung adenocarcinoma showed a group of patients with a significant lower overall survival (46,63 ± 17,44 vs 98,79 ± 15,02 weeks; p= 0,018) and post-metastasic survival (18,86 ± 6,61 vs 84,78 ± 14,88 weeks; p= 0,002). Conclusion: Non-significant differences for PINK1 were noted between primary and metastatic adenocarcinoma samples. More than 80 points of PINK1 immunoexpression in primary lung adenocarcinoma revealed a group of patients with a poorer prognosis. Funding: A competitive grant to IFV in the intramural call for the promotion of research projects of the Institute of Health Research of the Principality of Asturias, ISPA (2020-2022). S142