Scientists have discovered various prognostic gene signatures (GSs) in different cancer types. Surprisingly, although different GSs from the same cancer type can be used to measure similar biological characteristics, often rarely is there a gene shared by different GSs. To explain such a paradox, we hypothesized that GSs from the same cancer type may be regulated by common regulatory motifs. To test this hypothesis, we carried out a comprehensive motif analysis on the prognostic GSs from five cancer types. We demonstrated that GSs from individual cancer type as well as across cancer types share regulatory motifs. We also observed that transcription factors that likely bind to these shared motifs have prognostic functions in cancers. Moreover, 75% of the predicted cofactors of these transcription factors may have cancer-related functions and some cofactors even have prognostic functions. In addition, there exist common microRNAs that regulate different GSs from individual cancer types and across cancer types, several of which are prognostic biomarkers for the corresponding cancer types. Our study suggested the existence of common regulatory mechanisms shared by GSs from individual cancer types and across cancer types, which shed light on the discovery of new prognostic GSs in cancers and the understanding of the regulatory mechanisms of cancers.
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