Cross-Talk between p53 and Wnt Signaling in Cancer.

Targeting cancer hallmarks is a cardinal strategy to improve antineoplastic treatment. However, cross-talk between signaling pathways and key oncogenic processes frequently convey resistance to targeted therapies. The p53 and Wnt pathway play vital roles for the biology of many tumors, as they are critically involved in cancer onset and progression. Over recent decades, a high level of interaction between the two pathways has been revealed. Here, we provide a comprehensive overview of molecular interactions between the p53 and Wnt pathway discovered in cancer, including complex feedback loops and reciprocal transactivation. The mutational landscape of genes associated with p53 and Wnt signaling is described, including mutual exclusive and co-occurring genetic alterations. Finally, we summarize the functional consequences of this cross-talk for cancer phenotypes, such as invasiveness, metastasis or drug resistance, and discuss potential strategies to pharmacologically target the p53-Wnt interaction.

Predicting response to neoadjuvant chemoradiotherapy in rectal cancer: from biomarkers to tumor models.

Colorectal cancer (CRC) is a major contributor to cancer-associated morbidity worldwide and over one-third of CRC is located in the rectum. Neoadjuvant chemoradiotherapy (nCRT) followed by surgical resection is commonly applied to treat locally advanced rectal cancer (LARC). In this review, we summarize current and novel concepts of neoadjuvant therapy for LARC such as total neoadjuvant therapy and describe how these developments impact treatment response. Moreover, as response to nCRT is highly divergent in rectal cancers, we discuss the role of potential predictive biomarkers. We review recent advances in biomarker discovery, from a clinical as well as a histopathological and molecular perspective. Furthermore, the role of emerging predictive biomarkers derived from the tumor environment such as immune cell composition and gut microbiome is presented. Finally, we describe how different tumor models such as patient-derived cancer organoids are used to identify novel predictive biomarkers for chemoradiotherapy (CRT) in rectal cancer.

KDM6A Depletion in Breast Epithelial Cells Leads to Reduced Sensitivity to Anticancer Agents and Increased TGFß Activity.

KDM6A, an X chromosome-linked histone lysine demethylase, was reported to be frequently mutated in many tumor types including breast and bladder cancer. However, the functional role of KDM6A is not fully understood. Using MCF10A as a model of non-tumorigenic epithelial breast cells, we found that silencing KDM6A promoted cell migration and transformation demonstrated by the formation of tumor-like acini in three-dimensional culture. KDM6A loss reduced the sensitivity of MCF10A cells to therapeutic agents commonly used to treat patients with triple-negative breast cancer and also induced TGFß extracellular secretion leading to suppressed expression of cytotoxic genes in normal human CD8+ T cells in vitro. Interestingly, when cells were treated with TGFß, de novo synthesis of KDM6A protein was suppressed while TGFB1 transcription was enhanced, indicating a TGFß/KDM6A-negative regulatory axis. Furthermore, both KDM6A deficiency and TGFß treatment promoted disorganized acinar structures in three-dimensional culture, as well as transcriptional profiles associated with epithelial-to-mesenchymal transition and metastasis, suggesting KDM6A depletion and TGFß drive tumor progression. IMPLICATIONS: Our study provides the preclinical rationale for evaluating KDM6A and TGFß in breast tumor samples as predictors for response to chemo and immunotherapy, informing personalized therapy based on these findings.

Exposure of ß6/ß7-Loop in Zn/Cu Superoxide Dismutase (SOD1) Is Coupled to Metal Loss and Is Transiently Reversible During Misfolding.

Upon losing its structural integrity (misfolding), SOD1 acquires neurotoxic properties to become a pathogenic protein in ALS, a neurodegenerative disease targeting motor neurons; understanding the mechanism of misfolding may enable new treatment strategies for ALS. Here, we reported a monoclonal antibody, SE21, targeting the ß6/ß7-loop region of SOD1. The exposure of this region is coupled to metal loss and is entirely reversible during the early stages of misfolding. By using SE21 mAb, we demonstrated that, in apo-SOD1 incubated under the misfolding-promoting conditions, the reversible phase, during which SOD1 is capable of restoring its nativelike conformation in the presence of metals, is followed by an irreversible structural transition, autocatalytic in nature, which takes place prior to the onset of SOD1 aggregation and results in the formation of atypical apo-SOD1 that is unable to bind metals. The reversible phase defines a window of opportunity for pharmacological intervention using metal mimetics that stabilize SOD1 structure in its nativelike conformation to attenuate the spreading of the misfolding signal and disease progression by preventing the exposure of pathogenic SOD1 epitopes. Phenotypically similar apo-SOD1 species with impaired metal binding properties may also be produced via oxidation of Cys111, underscoring the diversity of SOD1 misfolding pathways.

Primate differential redoxome (PDR) - A paradigm for understanding neurodegenerative diseases.

Despite different phenotypic manifestations, mounting evidence points to similarities in the molecular basis of major neurodegenerative diseases (ND). CNS has evolved to be robust against hazard of ROS, a common perturbation aerobic organisms are confronted with. The trade-off of robustness is system's fragility against rare and unexpected perturbations. Identifying the points of CNS fragility is key for understanding etiology of ND. We postulated that the 'primate differential redoxome' (PDR), an assembly of proteins that contain cysteine residues present only in the primate orthologues of mammals, is likely to associate with an added level of regulatory functionalities that enhanced CNS robustness against ROS and facilitated evolution. The PDR contains multiple deterministic and susceptibility factors of major ND, which cluster to form coordinated redox networks regulating various cellular processes. The PDR analysis revealed a potential CNS fragility point, which appears to associates with a non-redundant PINK1-PRKN-SQSTM1(p62) axis coordinating protein homeostasis and mitophagy.

RNA-Binding Protein ZFP36L1 Suppresses Hypoxia and Cell-Cycle Signaling.

ZFP36L1 is a tandem zinc-finger RNA-binding protein that recognizes conserved adenylate-uridylate-rich elements (ARE) located in 3'untranslated regions (UTR) to mediate mRNA decay. We hypothesized that ZFP36L1 is a negative regulator of a posttranscriptional hub involved in mRNA half-life regulation of cancer-related transcripts. Analysis of in silico data revealed that ZFP36L1 was significantly mutated, epigenetically silenced, and downregulated in a variety of cancers. Forced expression of ZFP36L1 in cancer cells markedly reduced cell proliferation in vitro and in vivo, whereas silencing of ZFP36L1 enhanced tumor cell growth. To identify direct downstream targets of ZFP36L1, systematic screening using RNA pull-down of wild-type and mutant ZFP36L1 as well as whole transcriptome sequencing of bladder cancer cells {plus minus} tet-on ZFP36L1 was performed. A network of 1,410 genes was identified as potential direct targets of ZFP36L1. These targets included a number of key oncogenic transcripts such as HIF1A, CCND1, and E2F1. ZFP36L1 specifically bound to the 3'UTRs of these targets for mRNA degradation, thus suppressing their expression. Dual luciferase reporter assays and RNA electrophoretic mobility shift assays showed that wild-type, but not zinc-finger mutant ZFP36L1, bound to HIF1A 3'UTR and mediated HIF1A mRNA degradation, leading to reduced expression of HIF1A and its downstream targets. Collectively, our findings reveal an indispensable role of ZFP36L1 as a posttranscriptional safeguard against aberrant hypoxic signaling and abnormal cell-cycle progression. SIGNIFICANCE: RNA-binding protein ZFP36L1 functions as a tumor suppressor by regulating the mRNA stability of a number of mRNAs involved in hypoxia and cell-cycle signaling.

SOX7 regulates MAPK/ERK-BIM mediated apoptosis in cancer cells.

Apoptosis of cancer cells occurs by a complex gene regulatory network. Here we showed that SOX7 was significantly downregulated in different cancer types, especially in lung and breast cancers. Low expression of SOX7 was associated with advantage stage of cancer with shorter overall survival. Cancer cells with loss of SOX7 promoted cell survival and colony formation, suppressed cellular apoptosis and produced a drug resistant phenotype against a variety of chemo/targeting therapeutic agents. Mechanistically, SOX7 induced cellular apoptosis through upregulation of genes associated with both P38 and apoptotic signaling pathway, as well as preventing the proteasome mediated degradation of pro-apoptotic protein BIM. Treatment of either a proteasome inhibitor MG132 or bortezomib, or with a p-ERK/MEK inhibitor U0126 attenuate the SOX7 promoted BIM degradation. We identified Panobinostat, an FDA approved pan-HDAC inhibitor, could elevate and restore SOX7 expression in SOX7 silenced lung cancer cells. Taken together, these data revealed an unappreciated role of SOX7 in regulation of cellular apoptosis through control of MAPK/ERK-BIM signaling.

LNK suppresses interferon signaling in melanoma.

LNK (SH2B3) is a key negative regulator of JAK-STAT signaling which has been extensively studied in malignant hematopoietic diseases. We found that LNK is significantly elevated in cutaneous melanoma; this elevation is correlated with hyperactive signaling of the RAS-RAF-MEK pathway. Elevated LNK enhances cell growth and survival in adverse conditions. Forced expression of LNK inhibits signaling by interferon-STAT1 and suppresses interferon (IFN) induced cell cycle arrest and cell apoptosis. In contrast, silencing LNK expression by either shRNA or CRISPR-Cas9 potentiates the killing effect of IFN. The IFN-LNK signaling is tightly regulated by a negative feedback mechanism; melanoma cells exposed to IFN upregulate expression of LNK to prevent overactivation of this signaling pathway. Our study reveals an unappreciated function of LNK in melanoma and highlights the critical role of the IFN-STAT1-LNK signaling axis in this potentially devastating disease. LNK may be further explored as a potential therapeutic target for melanoma immunotherapy.

Molecular mechanism and therapeutic implications of selinexor (KPT-330) in liposarcoma.

Exportin-1 mediates nuclear export of multiple tumor suppressor and growth regulatory proteins. Aberrant expression of exportin-1 is noted in human malignancies, resulting in cytoplasmic mislocalization of its target proteins. We investigated the efficacy of selinexor against liposarcoma cells both in vitro and in vivo. Exportin-1 was highly expressed in liposarcoma samples and cell lines as determined by immunohistochemistry, western blot, and immunofluorescence assay. Knockdown of endogenous exportin-1 inhibited proliferation of liposarcoma cells. Selinexor also significantly decreased cell proliferation as well as induced cell cycle arrest and apoptosis of liposarcoma cells. The drug also significantly decreased tumor volumes and weights of liposarcoma xenografts. Importantly, selinexor inhibited insulin-like growth factor 1 (IGF1) activation of IGF-1R/AKT pathway through upregulation of insulin-like growth factor binding protein 5 (IGFBP5). Further, overexpression and knockdown experiments showed that IGFBP5 acts as a tumor suppressor and its expression was restored upon selinexor treatment of liposarcoma cells. Selinexor decreased aurora kinase A and B levels in these cells and inhibitors of these kinases suppressed the growth of the liposarcoma cells. Overall, our study showed that selinexor treatment restored tumor suppressive function of IGFBP5 and inhibited aurora kinase A and B in liposarcoma cells supporting the usefulness of selinexor as a potential therapeutic strategy for the treatment of this cancer.