Mdm2 and Mdmx, both major repressors of p53 in human cancers, are predominantly localized to the nucleus and cytoplasm, respectively. The mechanism by which subcellular localization of Mdmx is regulated remains unclear. In this study, we identify the E3 ligase Peli1 as a major binding partner and regulator of Mdmx in human cells. Peli1 bound Mdmx in vitro and in vivo and promoted high levels of ubiquitination of Mdmx. Peli1-mediated ubiquitination was degradation-independent, promoting cytoplasmic localization of Mdmx which in turn resulted in p53 activation. Consistent with this, knockdown or knockout Peli1 in human cancer cells induced nuclear localization of Mdmx and suppressed p53 activity. Myc-induced tumorigenesis was accelerated in Peli1-null mice and associated with downregulation of p53 function. Clinical samples of human cutaneous melanoma had decreased Peli1 expression which was associated with poor overall survival. Together, these results demonstrate that Peli1 acts as a critical factor for the Mdmx-p53 axis by modulating the subcellular localization and activity of Mdmx, thus revealing a novel mechanism of Mdmx deregulation in human cancers.

Equilibrium between immune activation and suppression may be necessary to maintain immune homeostasis, because proinflammatory effector T cells (defined as antiregulatory T cells) counteract the functions of regulatory immune cells. These self-reactive T cells recognize human leukocyte antigen (HLA)–restricted epitopes derived from proteins expressed by regulatory immune cells such as IDO, PD-L1, PD-L2, or arginase. The activation of such proinflammatory effector T cells offers a novel way to directly target the tumor microenvironment, potentially giving them considerable clinical value, especially in patients with cancer. Vaccination against genetically stable cells with regular HLA expression is an attractive way to directly target immunosuppressive cells in addition to attracting proinflammatory cells into the tumor microenvironment. Importantly, vaccination toward IDO or PD-L1 to potentiate such T cells have proven safe, with minimal toxicity in the clinical phase I trials conducted thus far. Cancer Res; 1–4. ©2018 AACR.

ZEB1 is a prime element of a network of transcription factors that controls epithelial-to-mesenchymal transition (EMT), a reversible embryonic transdifferentiation program that allows partial or complete transition from an epithelial to a mesenchymal state. Aberrant expression of ZEB1 has been reported in a variety of human cancers, where it is generally believed to foster migration, invasion, and metastasis. Over the past few years, in vitro and in vivo observations have highlighted unsuspected intrinsic oncogenic functions of ZEB1 that impact tumorigenesis from its earliest stages. Located downstream of regulatory processes that integrate microenvironmental signals and directly implicated in feedback loops controlled by miRNAs, ZEB1 appears to be a central switch that determines cell fate. Its expression fosters malignant transformation through the mitigation of critical oncosuppressive pathways and through the conferment of stemness properties. ZEB1 is also a key determinant of cell plasticity, endowing cells with the capacity to withstand an aberrant mitogenic activity, with a profound impact on the genetic history of tumorigenesis, and to adapt to the multiple constraints encountered over the course of tumor development. Cancer Res; 78(1); 1–6. ©2017 AACR.

CAR-T Cell Therapy is a groundbreaking new cancer treatment that recently received FDA approval. But what is it exactly? Here, we explain.