The new role for an old guy: MYC as an immunoplayer

Targeting MYC at the intersection between cancer metabolism and oncoimmunology

MYC activation is a known hallmark of cancer as it governs the gene targets involved in various facets of cancer progression. Of interest, MYC governs oncometabolism through the interactions with its partners and cofactors, as well as cancer immunity via its gene targets. Recent investigations have taken interest in characterizing these interactions through multi-Omic approaches, to better understand the vastness of the MYC network. Of the several gene targets of MYC involved in either oncometabolism or oncoimmunology, few of them overlap in function. Prominent interactions have been observed with MYC and HIF-1α, in promoting glucose and glutamine metabolism and activation of antigen presentation on regulatory T cells, and its subsequent metabolic reprogramming. This review explores existing knowledge of the role of MYC in oncometabolism and oncoimmunology. It also unravels how MYC governs transcription and influences cellular metabolism to facilitate the induction of pro- or anti-tumoral immunity. Moreover, considering the significant roles MYC holds in cancer development, the present study discusses effective direct or indirect therapeutic strategies to combat MYC-driven cancer progression.

The role of ubiquitin pathway-mediated regulation of immune checkpoints in cancer immunotherapy

With the continuous cognition of the relationship between tumor cells and tumor immune microenvironment, immunotherapy based on the immune checkpoint blockade has achieved great breakthroughs, led to improved clinical outcomes, and prolonged survival for cancer patients in recent years. Nevertheless, the de novo or acquired resistance to immunotherapy has greatly counteracted the efficacy, leading to a 20%-40% overall response rate. Thus, further in-depth understanding of the regulation of the tumor microenvironment and antitumor immunity is urgently warranted. Ubiquitination-mediated protein degradation plays vital roles in protein stabilization, activation, and dynamics as well as in cellular homeostasis modulation. The dysregulated ubiquitination and deubiquitination are closely related to the changes in physiological and pathological processes, which subsequently result in a variety of diseases including cancer. In this review, the authors first summarize the current knowledge about the involvement of the ubiquitin-proteasome system in tumor development with the ubiquitin conjugation-regulated stability of p53, phosphatase and tensin homolog, and Myc protein as examples, then dissect the potential implications of ubiquitination-mediated immune checkpoints degradation in tumor microenvironment and immune responses, and finally discuss the effects of therapeutically targeting the ubiquitin-proteasome pathway on immunotherapy, with the goal of providing deep insights into the exploitation of more precise and effective combinational therapy against cancer.

The Diminishment of Novel Endometrial Carcinoma-Derived Stem-like Cells by Targeting Mitochondrial Bioenergetics and MYC

Cancer stem cells (CSCs) are a small subpopulation of tumor cells harboring properties that include self-renewal, multi-lineage differentiation, tumor reconstitution, drug resistance and invasiveness, making them key players in tumor relapse. In the present paper, we develop new CSC models and analyze the molecular pathways involved in survival to identify targets for the establishment of novel therapies. Endometrial carcinoma-derived stem-like cells (ECSCs) were isolated from carcinogenic gynecological tissue and analyzed regarding their expression of prominent CSC markers. Further, they were treated with the MYC-signaling inhibitor KJ-Pyr-9, chemotherapeutic agent carboplatin and type II diabetes medication metformin. ECSC populations express common CSC markers, such as Prominin-1 and CD44 antigen as well as epithelial-to-mesenchymal transition markers, Twist, Snail and Slug, and exhibit the ability to form free-floating spheres. The inhibition of MYC signaling and treatment with carboplatin as well as metformin significantly reduced the cell survival of ECSC-like cells. Further, treatment with metformin significantly decreased the mitochondrial membrane potential of ECSC-like cells, while the extracellular lactate concentration was increased. The established ECSC-like populations represent promising in vitro models to further study the contribution of ECSCs to endometrial carcinogenesis. Targeting MYC signaling as well as mitochondrial bioenergetics has shown promising results in the diminishment of ECSCs, although molecular signaling pathways need further investigations.

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.

Obscure Involvement of MYC in Neurodegenerative Diseases and Neuronal Repair

MYC is well known as a potent oncogene involved in regulating cell cycle and metabolism. Augmented MYC expression leads to cell cycle dysregulation, intense cell proliferation, and carcinogenesis. Surprisingly, its increased expression in neurons does not induce their proliferation, but leads to neuronal cell death and consequent development of a neurodegenerative phenotype. Interestingly, while cancer and neurodegenerative diseases such as Alzheimer's disease are placed at the opposite sides of cell division spectrum, both start with cell cycle dysregulation and stimulation of proliferation. It seems that MYC action directed toward neuron cell proliferation and neural tissue repair collides with evolutional loss of regenerative capacity of CNS neurons in order to strengthen synaptic structure, to protect our cognitive abilities and therefore character. Accordingly, there are abundant mechanisms that block its expression and action specifically in the brain. Moreover, while MYC expression in brain neurons during neurodegenerative processes is related to their death, there are obvious evidences that MYC action after physical injury is beneficial in case of peripheral nerve recovery. MYC might be a useful tool to repair brain cells upon development of neurodegenerative disease or CNS trauma, including stroke and traumatic brain and spinal cord injury, as even imperfect axonal growth and regeneration strategies will likely be of profound benefit. Understanding complex control of MYC action in the brain might have important therapeutic significance, but also it may contribute to the comprehension of development of neurodegenerative diseases.

Low Expression of IL-15 and NKT in Tumor Microenvironment Predicts Poor Outcome of MYCN-Non-Amplified Neuroblastoma

Immune tumor microenvironment (TME) in neuroblastoma (NBL) contributes to tumor behavior and treatment response. T cells and natural killer (NK) cells have been shown to play important roles in the neuroblastoma TME. However, few reports address the clinical relevance of natural killer T cells (NKTs) and interleukin-15 (IL-15), one of the crucial cytokines controlling the activation and expansion of NK/NKT cells, in NBL. In this study, we examined NKT immunoscores and IL-15 expression in both MYCN-amplified and MYCN-non-amplified NBL to correlate with clinical outcomes such as event-free survival (EFS) and overall survival (OS). From Gene Expression Omnibus (GEO) datasets GSE45480 (n = 643) and GSE49711 (n = 493), we found that NKT immunoscore and IL-15 expression were both significantly lower in MYCN-amplified NBL, and similar results were observed using our clinical NBL samples (n = 53). Moreover, NBL patients (GEO dataset GSE49711 and our clinical samples) with both lower NKT immunoscore and IL-15 expression exhibited decreased EFS and OS regardless of MYCN gene amplification status. Multivariate analysis further showed that the combination of low NKT immunoscore and low IL-15 expression level was an independent prognostic factor for poor EFS and OS in our NBL patients. These findings provide the rationale for the development of strategy to incorporate IL-15 and NKT cell therapy into the treatment regimen for neuroblastoma.

MYC as a target for cancer treatment

The MYC gene which consists of 3 paralogs, C-MYC, N-MYC and L-MYC, is one of the most frequently deregulated driver genes in human cancer. Because of its high prevalence of deregulation and its causal role in cancer formation, maintenance and progression, targeting MYC is theoretically an attractive strategy for treating cancer. As a potential anticancer target, MYC was traditionally regarded as undruggable due to the absence of a suitable pocket for high-affinity binding by low molecular weight inhibitors. In recent years however, several compounds that directly or indirectly inhibit MYC have been shown to have anticancer activity in preclinical tumor models. Amongst the most detailed investigated strategies for targeting MYC are inhibition of its binding to its obligate interaction partner MAX, prevention of MYC expression and blocking of genes exhibiting synthetic lethality with overexpression of MYC. One of the most extensively investigated MYC inhibitors is a peptide/mini-protein known as OmoMYC. OmoMYC, which acts by blocking the binding of all 3 forms of MYC to their target promoters, has been shown to exhibit anticancer activity in a diverse range of preclinical models, with minimal side effects. Based on its broad efficacy and limited toxicity, OmoMYC is currently being developed for evaluation in clinical trials. Although no compound directly targeting MYC has yet progressed to clinical testing, APTO-253, which partly acts by decreasing expression of MYC, is currently undergoing a phase I clinical trial in patients with relapsed/refractory acute myeloid leukemia or myelodysplastic syndrome.