The amino acid sequence enriched with proline (P), glutamic acid (E), serine (S), and threonine (T) (PEST) is a signal‐transducing agent providing unique features to its substrate nuclear proteins (PEST‐NPs). The PEST motif is responsible for particular posttranslational modifications (PTMs). These PTMs impart distinct properties to PEST‐NPs that are responsible for their activation/inhibition, intracellular localization, and stability/degradation. PEST‐NPs participate in cancer metabolism, immunity, and protein transcription as oncogenes or as tumor suppressors. Gene‐based therapeutics are getting the attention of researchers because of their cell specificity. PEST‐NPs are good targets to explore as cancer therapeutics. Insights into PTMs of PEST‐NPs demonstrate that these proteins not only interact with each other but also recruit other proteins to/from their active site to promote/inhibit tumors. Thus, the role of PEST‐NPs in cancer biology is multivariate. It is hard to obtain therapeutic objectives with single gene therapy. An especially designed combination gene therapy might be a promising strategy in cancer treatment. This review highlights the multifaceted behavior of PEST‐NPs in cancer biology. We have summarized a number of studies to address the influence of structure and PEST‐mediated PTMs on activation, localization, stability, and protein–protein interactions of PEST‐NPs. We also recommend researchers to adopt a pragmatic approach in gene‐based cancer therapy. 1.PEST (proline, glutamic acid, serine, and threonine) motif is responsible for particular posttranslational modifications (PTMs) in their substrate nuclear proteins. 2.Insights into PTMs of nuclear proteins demonstrate that these proteins not only interact with each other but also recruit other proteins to/from their active site to promote/inhibit tumors. 3.PEST sequence enriched nuclear proteins (PEST‐NPs) are multivariate in their behavior.