NF-kB2 induces senescence bypass in melanoma via a direct transcriptional activation of EZH2

FGFR4 and EZH2 inhibitors synergistically induce hepatocellular carcinoma apoptosis via repressing YAP signaling

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers worldwide, but current treatment options remain limited and cause serious life-threatening side effects. Aberrant FGFR4 signaling has been validated as an oncogenic driver of HCC, and EZH2, the catalytic subunit of the PRC2 complex, is a potential factor that contributes to acquired drug resistance in many tumors, including HCC. However, the functional relationship between these two carcinogenic factors, especially their significance for HCC treatment, remains unclear. In this study, we systematically evaluated the feasibility of a combination therapy targeting FGFR4 and EZH2 for HCC.

METHODS

RNA sequencing data of patients with Liver hepatocellular carcinoma (LIHC) from The Cancer Genome Atlas (TCGA) were analyzed to determine FGFR4 and EZH2 expression and their interaction with prognosis. Moreover, the HCC cell lines, zebrafish/mouse HCC xenografts and zebrafish HCC primary tumors were treated with FGFR4 inhibitor (Roblitinib) and/or EZH2 inhibitor (CPI-169) and then subjected to cell proliferation, viability, apoptosis, and tumor growth analyses to evaluate the feasibility of combination therapy for HCC both in vitro and in vivo. Furthermore, RNA-Seq was performed in combination with ChIP-Seq data analysis to investigate the critical mechanism underlying the combination treatment with Roblitinib and CPI-169.

RESULTS

EZH2 accumulated through the non-canonical NF-kB signaling in response to FGFR4 inhibitor treatment, and the elevated EZH2 levels led to the antagonism of HCC against Roblitinib (FGFR4 inhibitor). Notably, knockdown of EZH2 sensitized HCC cells to Roblitinib, while the combination treatment of Roblitinib and CPI-169 (EZH2 inhibitor) synergistically induced the HCC cell apoptosis in vitro and suppressed the zebrafish/mouse HCC xenografts and zebrafish HCC primary tumors development in vivo. Moreover, Roblitinib and CPI-169 synergistically inhibited HCC development via repressing YAP signaling.

CONCLUSIONS

Collectively, our study highlighted the potential of the therapeutic combination of FGFR4 and EZH2 inhibitors, which would provide new references for the further development of clinical treatment strategies for HCC.

GSK343, an Inhibitor of Enhancer of Zeste Homolog 2, Reduces Glioblastoma Progression through Inflammatory Process Modulation: Focus on Canonical and Non-Canonical NF-κB/IκBα Pathways

Glioblastoma (GB) is a tumor of the central nervous system characterized by high proliferation and invasiveness. The standard treatment for GB includes radiotherapy and chemotherapy; however, new therapies are needed. Particular attention was given to the role of histone methyltransferase enhancer of zeste-homolog-2 (EZH2) in GB. Recently, several EZH2-inhibitors have been developed, particularly GSK343 is well-known to regulate apoptosis and autophagy processes; however, its abilities to modulate canonical/non-canonical NF-κB/IκBα pathways or an immune response in GB have not yet been investigated. Therefore, this study investigated for the first time the effect of GSK343 on canonical/non-canonical NF-κB/IκBα pathways and the immune response, by an in vitro, in vivo and ex vivo model of GB. In vitro results demonstrated that GSK343 treatments 1, 10 and 25 μM significantly reduced GB cell viability, showing the modulation of canonical/non-canonical NF-κB/IκBα pathway activation. In vivo GSK343 reduced subcutaneous tumor mass, regulating canonical/non-canonical NF-κB/IκBα pathway activation and the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD). Ex vivo results confirmed the anti-proliferative effect of GSK343 and also demonstrated its ability to regulate immune response through CXCL9, CXCL10 and CXCL11 expression in GB. Thus, GSK343 could represent a therapeutic strategy to counteract GB progression, thanks to its ability to modulate canonical/non-canonical NF-κB/IκBα pathways and immune response.

Redox signaling at the crossroads of human health and disease

Redox biology is at the core of life sciences, accompanied by the close correlation of redox processes with biological activities. Redox homeostasis is a prerequisite for human health, in which the physiological levels of nonradical reactive oxygen species (ROS) function as the primary second messengers to modulate physiological redox signaling by orchestrating multiple redox sensors. However, excessive ROS accumulation, termed oxidative stress (OS), leads to biomolecule damage and subsequent occurrence of various diseases such as type 2 diabetes, atherosclerosis, and cancer. Herein, starting with the evolution of redox biology, we reveal the roles of ROS as multifaceted physiological modulators to mediate redox signaling and sustain redox homeostasis. In addition, we also emphasize the detailed OS mechanisms involved in the initiation and development of several important diseases. ROS as a double‐edged sword in disease progression suggest two different therapeutic strategies to treat redox‐relevant diseases, in which targeting ROS sources and redox‐related effectors to manipulate redox homeostasis will largely promote precision medicine. Therefore, a comprehensive understanding of the redox signaling networks under physiological and pathological conditions will facilitate the development of redox medicine and benefit patients with redox‐relevant diseases.

Merkel Cell Polyomavirus Small T Antigen Activates Noncanonical NF-κB Signaling to Promote Tumorigenesis

Multiple human polyomaviruses (HPyV) can infect the skin, but only Merkel cell polyomavirus (MCPyV) has been implicated in the development of a cancer, Merkel cell carcinoma (MCC). While expression of HPyV6, HPyV7, and MCPyV small T antigens (sT), all induced a senescence-associated secretory phenotype (SASP), MCPyV sT uniquely activated noncanonical NF-κB (ncNF-κB), instead of canonical NF-κB signaling, to evade p53-mediated cellular senescence. Through its large T stabilization domain, MCPyV sT activated ncNF-κB signaling both by inducing H3K4 trimethylation-mediated increases of NFKB2 and RELB transcription and also by promoting NFKB2 stabilization and activation through FBXW7 inhibition. Noncanonical NF-κB signaling was required for SASP cytokine secretion, which promoted the proliferation of MCPyV sT-expressing cells through autocrine signaling. Virus-positive MCC cell lines and tumors showed ncNF-κB pathway activation and SASP gene expression, and the inhibition of ncNF-κB signaling prevented VP-MCC cell growth in vitro and in xenografts. We identify MCPyV sT-induced ncNF-κB signaling as an essential tumorigenic pathway in MCC. IMPLICATIONS: This work is the first to identify the activation of ncNF-κB signaling by any polyomavirus and its critical role in MCC tumorigenesis.

NVD-BM-mediated genetic biosensor triggers accumulation of 7-dehydrocholesterol and inhibits melanoma via Akt1/NF-ĸB signaling

Aberrant activation of the cholesterol biosynthesis supports tumor cell growth. In recent years, significant progress has been made by targeting rate-limiting enzymes in cholesterol biosynthesis pathways to prevent carcinogenesis. However, precise mechanisms behind cholesterol degradation in cancer cells have not been comprehensively investigated. Here, we report that codon optimization of the orthologous cholesterol 7-desaturase, NVD-BM from Bombyx mori, significantly slowed melanoma cell proliferation and migration, and inhibited cancer cell engraftment in nude mice, by converting cholesterol to toxic 7-dehydrocholesterol. Based on these observations, we established a synthetic genetic circuit to induce melanoma cell regression by sensing tumor specific signals in melanoma cells. The dual-input signals, RELA proto-oncogene (RELA) and signal transducer and activator of transcription 1 (STAT1), activated NVD-BM expression and repressed melanoma cell proliferation and migration. Mechanically, we observed that NVD-BM decreased Akt1-ser473 phosphorylation and inhibited cytoplasmic RELA translocation. Taken together, NVD-BM was identified as a tumor suppressor in malignant melanoma, and we established a dual-input biosensor to promote cancer cell regression, via Akt1/NF-κB signaling. Our results demonstrate the potential therapeutic effects of cholesterol 7-desaturase in melanoma metabolism, and provides insights for genetic circuits targeting 7-dehydrocholesterol accumulation in tumors.

Roles of NF-κB Signaling in the Regulation of miRNAs Impacting on Inflammation in Cancer

The NF-κB family of transcription factors regulate the expression of genes encoding proteins and microRNAs (miRNA, miR) precursors that may either positively or negatively regulate a variety of biological processes such as cell cycle progression, cell survival, and cell differentiation. The NF-κB-miRNA transcriptional regulatory network has been implicated in the regulation of proinflammatory, immune, and stress-like responses. Gene regulation by miRNAs has emerged as an additional epigenetic mechanism at the post-transcriptional level. The expression of miRNAs can be regulated by specific transcription factors (TFs), including the NF-κB TF family, and vice versa. The interplay between TFs and miRNAs creates positive or negative feedback loops and also regulatory networks, which can control cell fate. In the current review, we discuss the impact of NF-κB-miRNA interplay and feedback loops and networks impacting on inflammation in cancer. We provide several paradigms of specific NF-κB-miRNA networks that can regulate inflammation linked to cancer. For example, the NF-κB-miR-146 and NF-κB-miR-155 networks fine-tune the activity, intensity, and duration of inflammation, while the NF-κB-miR-21 and NF-κB-miR-181b-1 amplifying loops link inflammation to cancer; and p53- or NF-κB-regulated miRNAs interconnect these pathways and may shift the balance to cancer development or tumor suppression. The availability of genomic data may be useful to verify and find novel interactions, and provide a catalogue of 162 miRNAs targeting and 40 miRNAs possibly regulated by NF-κB. We propose that studying active TF-miRNA transcriptional regulatory networks such as NF-κB-miRNA networks in specific cancer types can contribute to our further understanding of the regulatory interplay between inflammation and cancer, and also perhaps lead to the development of pharmacologically novel therapeutic approaches to combat cancer.

Melanocytic Nevi and the Genetic and Epigenetic Control of Oncogene-Induced Senescence

Melanocytic nevi represent benign clonal proliferations of the melanocytes in the skin that usually remain stable in size and behavior or disappear during life. Infrequently, melanocytic nevi undergo malignant transformation to melanoma. Understanding molecular and cellular mechanisms underlying oncogene-induced senescence should help identify pathways underlying melanoma development, leading to the development of new strategies for melanoma prevention and early detection.

Groth B, Hersey P. EZH2 as a mediator of treatment resistance in melanoma

Direct treatments of cancer such as chemotherapy, radiotherapy and targeted therapy have been shown to depend on recruitment of the immune system for their effectiveness. Recent studies have shown that development of resistance to direct therapies such as BRAF inhibitors in melanoma is associated with suppression of immune responses. We point to emerging data that implicate activation of the polycomb repressive complex 2 (PRC2) and its catalytic component-enhancer of zeste homolog 2 (EZH2)-in progression of melanoma and suppression of immune responses. EZH2 appears to have an important role in differentiation of CD4 T cells and particularly in the function of T regulatory cells, which suppress immune responses to melanoma. We review mechanisms of EZH2 activation at the genomic level and from activation of the MAP kinase, E2F or NF-kB2 pathways. These studies are consistent with activation of EZH2 as a common mechanism for induction of immune suppression in patients failing direct therapies and suggest EZH2 inhibitors may have a role in combination with immunotherapy and targeted therapies to prevent development of immunosuppression.

The Wnts of change: How Wnts regulate phenotype switching in melanoma

The outgrowth of metastatic and therapy-resistant subpopulations in cancer remains a critical barrier for the successful treatment of this disease. In melanoma, invasion and proliferation are uncoupled, such that highly proliferative melanoma cells are less likely to be invasive, and vice versa. The transition between each state is likely a dynamic rather than a static, permanent change. This is referred to as "phenotype switching". Wnt signaling pathways drive phenotypic changes and promote therapy resistance in melanoma, as well as play roles in the modulation of the immune microenvironment. Three Wnt signaling pathways play a role in melanoma progression, canonical (β-catenin dependent), polar cell polarity (PCP), and the Wnt/Ca²⁺ pathway. Here we summarize phenotype plasticity and its role in therapy resistance and immune evasion. Targeting the Wnt signaling pathways may be an effective way to overcome tumor plasticity in melanoma.