Neira, José L.

Activation of oncogenes, such as through mutations in Kirsten rat sarcoma viral oncogene homolog (KRAS), triggers profound disruptions in cellular homeostasis that set off a cascade of stress responses. These responses enable cells to cope with the array of challenges encountered during tumorigenesis by activating defense mechanisms that promote adaptation and survival. Key components of this oncogenic stress response include heat shock proteins, the ubiquitin-proteasome system, autophagy, nuclear factor erythroid 2-related factor 2–antioxidant response element signaling, DNA damage response proteins, p53, redox-regulating proteins, and stress granules. This review concentrates on KRAS-driven oncogenic transformation, as KRAS mutations are among the most common in human cancers, accounting for over 90% of pancreatic ductal adenocarcinoma cases, around 30% of lung cancers, and approximately 50% of colorectal cancers. We examine the intricate molecular interplay between oncogenic stress and the associated cellular defense mechanisms, emphasizing the key molecular events that follow KRAS activation. Importantly, the very pathways that allow cancer cells to adapt to oncogenic stress also offer novel therapeutic opportunities. By selectively targeting pivotal regulators within these stress response pathways, we can potentially disrupt the survival mechanisms of cancer cells. This strategy not only promises to enhance the effectiveness of existing treatments but also paves the way for the development of innovative therapies designed to combat tumor progression. In essence, exploiting oncogenic stress responses represents an original and promising therapeutic approach in the fight against cancer.

Significance We describe the interaction between an intrinsically disordered protein (IDP), NUPR1, and the well-folded C-terminal region of RING1B protein of the Polycomb complex, involving residues Ala33 and Thr68 of the IDP. These observations are significant because they raise the possibility that NUPR1 aids the function of the members of the Polycomb complex, playing an active role in carcinogenesis.

We have previously demonstrated a crucial role of nuclear protein 1 (NUPR1) in tumor development and progression. In this work, we report the functional characterization of a novel Nupr1‐like isoform (NUPR1L) and its functional interaction with the protumoral factor NUPR1. Through the use of primary sequence analysis, threading, and homology‐based molecular modeling, as well as expression and immunolocalization, studies reveal that NUPR1L displays properties, which are similar to member of the HMG‐like family of chromatin regulators, including its ability to translocate to the cell nucleus and bind to DNA. Analysis of the NUPR1L promoter showed the presence of two p53‐response elements at positions −37 and −7, respectively. Experiments using reporter assays combined with site‐directed mutagenesis and using cells with controllable p53 expression demonstrate that both of these sequences are responsible for the regulation of NUPR1L expression by p53. Congruently, NUPR1L gene expression is activated in response to DNA damage induced by oxaliplatin treatment or cell cycle arrest induced by serum starvation, two well‐validated methods to achieve p53 activation. Interestingly, expression of NUPR1L downregulates the expression of NUPR1, its closely related protumoral isoform, by a mechanism that involves the inhibition of its promoter activity. At the cellular level, overexpression of NUPR1L induces G1 cell cycle arrest and a decrease in their cell viability, an effect that is mediated, at least in part, by downregulating NUPR1 expression. Combined, these experiments constitute the first functional characterization of NUPR1L as a new p53‐induced gene, which negatively regulates the protumoral factor NUPR1. J. Cell. Physiol. 230: 2936–2950, 2015. © 2015 Wiley Periodicals, Inc.