The KRAB ‐ ZNF (Krüppel‐associated box domain zinc finger) gene family is composed of a large number of highly homologous genes, gene isoforms, and pseudogenes. The proteins encoded by these genes, whose expression is often tissue‐specific, act as epigenetic suppressors contributing to the addition of repressive chromatin marks and DNA methylation. Due to its high complexity, the KRAB ‐ ZNF family has not been studied in sufficient detail, and the involvement of its members in carcinogenesis remains mostly unexplored. In this study, we aimed to provide a comprehensive description of cancer‐associated KRAB ‐ ZNF s using publicly available The Cancer Genome Atlas pan‐cancer datasets. We analyzed 6727 tumor and normal tissue samples from 16 cancer types. Here, we showed that a small but distinctive cluster of 16 KRAB ‐ ZNF s is commonly upregulated across multiple cancer cohorts in comparison to normal samples. We confirmed these observations in the independent panels of lung and breast cancer cell lines and tissues. This upregulation was also observed for most of the KRAB ‐ ZNF splicing variants, whose expression is simultaneously upregulated in tumors compared to normal tissues. Finally, by analyzing the clinicopathological data for breast and lung cancers, we demonstrated that the expression of cancer‐associated KRAB ‐ ZNF s correlates with patient survival, tumor histology, and molecular subtyping. Altogether, our study allowed the identification and characterization of KRAB ‐ ZNF factors that may have an essential function in cancer biology and thus potential to become novel oncologic biomarkers and treatment targets.

Summary Krüppel-associated box domain zinc finger protein (KRAB ZNF) explorer is a web-based tool for comprehensive characterization of the mRNA expression status of KRAB-ZNF transcription factors in the data from The Cancer Genome Atlas study. Key functionalities cover a comparative analysis of KRAB-ZNF expression between normal and cancer tissues, an association of KRAB-ZNF expression with various pathological features, including survival analysis, association with global DNA methylation status, analyses of KRAB-ZNF isoform expressions and analysis of KRAB-ZNF levels in normal tissues. Availability and implementation KRAB ZNF explorer is available at http://mi2.mini.pw.edu.pl: 8080/KRAB_ZNF/. The source code for shiny application is available at: https://github.com/MI2DataLab/KRAB_ZNF/tree/master/app and the source code for analyses and precalculations are available at: https://github.com/MI2DataLab/KRAB_ZNF/tree/master/work