Mutational analysis of primary and metastatic colorectal cancer samples underlying the resistance to cetuximab-based therapy

Radim Nemecek,1 Jitka Berkovcova,2 Lenka Radova,3 Tomas Kazda,4 Jitka Mlcochova,3 Petra Vychytilova-Faltejskova,1,3 Ondrej Slaby,1,3 Marek Svoboda1 1Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Institute, Masaryk University, Brno, Czech Republic; 2Department of Oncological and Experimental Pathology, Masaryk Memorial Cancer Institute, Brno, Czech Republic; 3Central European Institute of Technology, Masaryk University, Brno, Czech Republic; 4Department of Radiation Oncology, Masaryk Memorial Cancer Institute, Masaryk University, Brno, Czech Republic Purpose: Although several molecular markers predicting resistance to cetuximab- or panitumumab-based therapy of metastatic colorectal cancer were described, mutations in RAS proto-oncogenes remain the only predictors being used in daily clinical practice. However, 35%–45% of wild-type RAS patients still do not respond to this anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody-based therapy, and therefore the definition of other predictors forms an important clinical need. The aim of the present retrospective single-institutional study was to evaluate potential genes responsible for resistance to anti-EGFR therapy in relation to mutational analysis of primary versus metastatic lesions. Patients and methods: Twenty-four paired primary and corresponding metastatic tissue samples from eight nonresponding and four responding metastatic colorectal cancer patients treated with cetuximab-based therapy were sequenced using a next-generation sequencing panel of 26 genes involved in EGFR signaling pathway and colorectal carcinogenesis. Results: Mutational status of primary tumors and metastatic lesions was highly concordant in TP53, APC, CTNNB1, KRAS, PIK3CA, PTEN, and FBXW7 genes. Metastatic samples harbor significantly more mutations than primary tumors. Potentially negative predictive value of FBXW7 mutations in relationship to anti-EGFR treatment outcomes was confirmed. Finally, new occurrences of activating KRAS mutations were identified in a group of patients initially determined as wild-type RAS by routinely used qPCR-based RAS mutational tests. All newly detected activating KRAS mutations most likely led to cetuximab treatment failure. Conclusion: The results of the present study suggest a need of careful consideration of previously published results of anti-EGFR-targeted therapy with regard to potentially inaccurate diagnostic tools used in the past. Based on our findings, we recommend more extensive use of next-generation sequencing testing in daily clinical practice, as it brings a significant added value in terms of validity of the diagnostic procedure. Keywords: colorectal cancer, cetuximab, resistance to anti-EGFR therapy, next-generation sequencing, FBXW7, KRA

Decreased expression levels of PIWIL1, PIWIL2, and PIWIL4 are associated with worse survival in renal cell carcinoma patients

Robert Iliev,1,2 Michal Stanik,3 Michal Fedorko,4 Alexandr Poprach,1 Petra Vychytilova-Faltejskova,1,2 Katerina Slaba,2 Marek Svoboda,1 Pavel Fabian,5 Dalibor Pacik,1 Jan Dolezel,2 Ondrej Slaby3,4 1Department of Comprehensive Cancer Care, Masaryk Memorial Cancer Institute, 2Central European Institute of Technology, Masaryk University, 3Department of Urologic Oncology, Masaryk Memorial Cancer Institute, 4Department of Urology, University Hospital Brno, Masaryk University Brno, 5Department of Diagnostic and Experimental Pathology, Masaryk Memorial Cancer Institute, Brno, Czech RepublicAbstract: Piwi-interacting RNAs (piRNAs) are a newly discovered class of small non-coding RNAs involved in silencing of transposable elements and in sequence-specific chromatin modifications. PIWI proteins (PIWIL) belong to the family of Argonaute genes/proteins, bind piRNAs and their functioning have been described mainly in germ-line cells and more recently also in stem cells and cancer cells. There are four PIWI proteins PIWIL1, PIWIL2, PIWIL3, and PIWIL4 discovered in human till now. Recent studies suggested that deregulated the expression of Piwi proteins and selected piRNAs is common to many types of cancers. We found significantly lower expression of PIWIL1 (P<0.0001) and piR-823 (P=0.0001) in tumor tissue in comparison to paired renal parenchyma. Further, we observed progressive decrease in PIWIL1 (P=0.0228), PIWIL2 (P=0.0015), and PIWIL4 (P=0.0028) expression levels together with increasing clinical stage. PIWIL2 (P=0.0073) and PIWIL4 (P=0.0001) expression progressively decreased also with increasing Fuhrman grade. Most importantly, low-expression levels of PIWIL1 (P=0.009), PIWIL2 (P<0.0001), and PIWIL4 (P=0.0065) were significantly associated with worse overall survival in renal cell carcinoma (RCC) patients. Our results suggest the involvement of PIWIL genes and piR-823 in RCC pathogenesis, and indicate PIWIL1, PIWIL2, and PIWIL4 as potential prognostic biomarkers in patients with RCC. Keywords: kidney cancer, PIWIL, piRN