Hippo Signaling Suppresses Cell Ploidy and Tumorigenesis through Skp2

Advances towards potential cancer therapeutics targeting Hippo signaling

Decades of research into the Hippo signaling pathway have greatly advanced our understanding of its roles in organ growth, tissue regeneration, and tumorigenesis. The Hippo pathway is frequently dysregulated in human cancers and is recognized as a prominent cancer signaling pathway. Hence, the Hippo pathway represents an ideal molecular target for cancer therapies. This review will highlight recent advancements in targeting the Hippo pathway for cancer treatment and discuss the potential opportunities for developing new therapeutic modalities.

A patent review of SCF E3 ligases inhibitors for cancer：Structural design, pharmacological activities and structure-activity relationship

Currently, as the largest family of E3 ubiquitin ligases, Skp1-Cullin 1-F-box (SCF) E3 ligase complexes have attracted extensive attention. Among SCF complexes, Skp2, β-TrCP, and FBXW7 have undergone extensive research on their structures and functions. Previous studies suggest Skp2, β-TrCP, and FBXW7 are overexpressed in numerous cancers. Thus, the SCF E3 ligase complex has become a significant target for the development of anti-cancer drugs. Over the past few decades, a variety of anti-tumor inhibitors targeting the SCF E3 ligase complex have been attempted. However, since almost none of the SCF E3 ligase inhibitors passed clinical trials, the design and synthesis of the new inhibitors are needed. Here, we will introduce the structure and function of Skp2, β-TrCP, and FBXW7, their connections with cancer development, the relevant in vitro and in vivo activities, selectivity, structure-activity relationships, and the therapeutic or preventive application of small molecule inhibitors targeting these three F-box proteins reported in the patent (2010-present). This information will help develop drugs targeting the SCF E3 ubiquitin ligase, providing new strategies for future cancer treatments.

Transient proliferation by reversible YAP and mitogen-control of the cyclin D1/p27 ratio

Hippo-YAP signaling orchestrates epithelial tissue repair and is therefore an attractive target in regenerative medicine. Yet it is unresolved how YAP integrates with mitogen signaling and contact inhibition to control the underlying transient proliferative response. Here we show that reduced contact inhibition, increased mitogen signaling, and YAP-TEAD activation converge on increasing the nuclear cyclin D1/p27 protein ratio during G1 phase, towards a threshold ratio that dictates whether individual cells enter or exit the cell cycle. YAP increases this ratio indirectly, in concert with mitogen signaling, by increasing EGFR and other receptors that signal primarily through ERK. After a delay, contact inhibition suppresses YAP activity which gradually downregulates mitogen signaling and the cyclin D1/p27 ratio. Increasing YAP activity by ablating the suppressor Merlin/NF2 reveals a balancing mechanism in which YAP suppression and contact inhibition of proliferation can be recovered but only at higher local cell density. Thus, critical for tissue repair, robust proliferation responses result from the YAP-induced and receptor-mediated prolonged increase in the cyclin D1/p27 ratio, which is only reversed by delayed suppression of receptor signaling after contact inhibition of YAP.

Hippo cooperates with p53 to regulate lung airway mucous cell metaplasia

Airway mucous cell metaplasia is a significant feature of many chronic airway diseases, such as chronic obstructive pulmonary disease, cystic fibrosis and asthma. However, the mechanisms underlying this process remain poorly understood. Here, we employed in vivo mouse genetic models to demonstrate that Hippo and p53 (encoded by Trp53) cooperate to modulate the differentiation of club cells into goblet cells. We revealed that ablation of Mst1 (Stk4) and Mst2 (Stk3), encoding the core components of Hippo signaling, significantly reduces mucous metaplasia in the lung airways in a lipopolysaccharide (LPS)-induced lung inflammation murine model while promoting club cell proliferation in a Yap (Yap1)-dependent manner. Additionally, we showed that deleting Mst1/2 is sufficient to suppress p53 deficiency-mediated goblet cell metaplasia. Finally, single-cell RNA-sequencing analysis revealed downregulation of YAP and p53 signaling in goblet cells in human airways. These findings underscore the important role of Hippo and p53 signaling in regulating airway mucous metaplasia.

Targeting the Hippo/YAP1 signaling pathway in hepatocellular carcinoma: From mechanisms to therapeutic drugs (Review)

The Hippo signaling pathway plays a pivotal role in regulating cell growth and organ size. Its regulatory effects on hepatocellular carcinoma (HCC) encompass diverse aspects, including cell proliferation, invasion and metastasis, tumor drug resistance, metabolic reprogramming, immunomodulatory effects and autophagy. Yes‑associated protein 1 (YAP1), a potent transcriptional coactivator and a major downstream target tightly controlled by the Hippo pathway, is influenced by various molecules and pathways. The expression of YAP1 in different cell types within the liver tumor microenvironment exerts varying effects on tumor outcomes, warranting careful consideration. Therefore, research on YAP1‑targeted therapies merits attention. This review discusses the composition and regulation mechanism of the Hippo/YAP1 signaling pathway and its relationship with HCC, offering insights for future research and cancer prevention strategies.

Yes-associated protein inhibition ameliorates carbon tetrachloride-induced acute liver injury in mice by reducing VDR

Carbon tetrachloride (CCl4) has a wide range of toxic effects, especially causing acute liver injury (ALI), in which rapid compensation for hepatocyte loss ensures liver survival, but proliferation of surviving hepatocytes (known as endoreplication) may imply impaired residual function. Yes-associated protein (YAP) drives hepatocytes to undergo endoreplication and ploidy, the underlying mechanisms of which remain a mystery. In the present study, we uncover during CCl4-mediated ALI accompanied by increased hepatocytes proliferation and YAP activation. Notably, bioinformatics analyses elucidate that hepatic-specific deletion of YAP substantially ameliorated CCl4-induced hepatic proliferation, effectively decreased the vitamin D receptor (VDR) expression. Additionally, a mouse model of acute liver injury substantiated that inhibition of YAP could suppress hepatocytes proliferation via VDR. Furthermore, we also disclosed that the VDR agonist nullifies CCl4-induced ALI alleviated by the YAP inhibitor in vivo. Importantly, hepatocytes were isolated from mice, and it was spotlighted that the anti-proliferative impact of the YAP inhibitor was abolished by the activation of VDR within these hepatocytes. Similarly, primary hepatic stellate cells (HSCs) were isolated and it was manifested that YAP inhibitor suppressed HSC activation via VDR during acute liver injury. Our findings further elucidate the YAP's role in ALI and may provide new avenues for protection against CCl4-drived acute liver injury.

ESRP2-microRNA-122 axis directs the postnatal onset of liver polyploidization and maturation

Hepatocyte polyploidy and maturity are critical to acquiring specialized liver functions. Multiple intra- and extracellular factors influence ploidy, but how they cooperate temporally to steer liver polyploidization and maturation or how post-transcriptional mechanisms integrate into these paradigms is unknown. Here, we identified an important regulatory hierarchy in which postnatal activation of Epithelial-Splicing-Regulatory-Protein-2 (ESRP2) stimulates biogenesis of liver-specific microRNA (miR-122), thereby facilitating polyploidization, maturation, and functional competence of hepatocytes. By determining transcriptome-wide protein-RNA interactions in vivo and integrating them with single-cell and bulk hepatocyte RNA-seq datasets, we delineate an ESRP2-driven RNA processing program that drives sequential replacement of fetal-to-adult transcript isoforms. Specifically, ESRP2 binds the primary miR-122 host gene transcript to promote its processing/biogenesis. Combining constitutive and inducible ESRP2 gain- and loss-of-function mice models with miR-122 rescue experiments, we demonstrate that timed activation of ESRP2 augments miR-122-driven program of cytokinesis failure, ensuring proper onset and extent of hepatocyte polyploidization.

Strategic advancement of E3 ubiquitin ligase in the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) presents a significant global health challenge due to its high incidence, poor prognosis, and limited treatment options. As a pivotal regulator of protein stability, E3 ubiquitin ligase plays a crucial role in tumorigenesis and development. This review provides an overview of the latest research on the involvement of E3 ubiquitin ligase in hepatocellular carcinoma and elucidates its significance in hepatocellular carcinoma cell proliferation, invasion, and evasion from immune surveillance. Special attention is given to the functions of RING, HECT, and RBR E3 ubiquitin ligases and their association with hepatocellular carcinoma progression. By dissecting the molecular mechanisms and regulatory networks governed by E3 ubiquitin ligase, several potential therapeutic strategies are proposed: including the development of specific inhibitors targeting E3 ligases; augmentation of their tumor suppressor activity through drug or gene therapy; utilization of E3 ubiquitin ligase to modulate immune checkpoint proteins for improved efficacy of immunotherapy; combination strategies integrating traditional therapies with E3 ubiquitin ligase inhibitors; as well as biomarker development based on E3 ubiquitin ligase activity. Furthermore, this review discusses the prospect of overcoming drug resistance in hepatocellular carcinoma treatment through these novel approaches. Overall, this review establishes a theoretical foundation and offers fresh insights into harnessing the potential of E3 ubiquitin ligase for treating hepatocellular carcinoma while highlighting future research directions that pave the way for clinical translation studies and new drug discoveries.

Surviving the Storm: The Role of Poly- and Depolyploidization in Tissues and Tumors

Polyploidization and depolyploidization are critical processes in the normal development and tissue homeostasis of diploid organisms. Recent investigations have revealed that polyaneuploid cancer cells (PACCs) exploit this ploidy variation as a survival strategy against anticancer treatment and for the repopulation of tumors. Unscheduled polyploidization and chromosomal instability in PACCs enhance malignancy and treatment resistance. However, their inability to undergo mitosis causes catastrophic cellular death in most PACCs. Adaptive ploid reversal mechanisms, such as multipolar mitosis, centrosome clustering, meiosis-like division, and amitosis, counteract this lethal outcome and drive cancer relapse. The purpose of this work is to focus on PACCs induced by cytotoxic therapy, highlighting the latest discoveries in ploidy dynamics in physiological and pathological contexts. Specifically, by emphasizing the role of "poly-depolyploidization" in tumor progression, the aim is to identify novel therapeutic targets or paradigms for combating diseases associated with aberrant ploidies.

Polyploidy in Cancer: Causal Mechanisms, Cancer-Specific Consequences, and Emerging Treatments

Drug resistance is the major determinant for metastatic disease and fatalities, across all cancers. Depending on the tissue of origin and the therapeutic course, a variety of biological mechanisms can support and sustain drug resistance. Although genetic mutations and gene silencing through epigenetic mechanisms are major culprits in targeted therapy, drug efflux and polyploidization are more global mechanisms that prevail in a broad range of pathologies, in response to a variety of treatments. There is an unmet need to identify patients at risk for polyploidy, understand the mechanisms underlying polyploidization, and to develop strategies to predict, limit, and reverse polyploidy thus enhancing efficacy of standard-of-care therapy that improve better outcomes. This literature review provides an overview of polyploidy in cancer and offers perspective on patient monitoring and actionable therapy.

Targeting RCC1 to block the human soft-tissue sarcoma by disrupting nucleo-cytoplasmic trafficking of Skp2

Soft-tissue sarcomas (STS) emerges as formidable challenges in clinics due to the complex genetic heterogeneity, high rates of local recurrence and metastasis. Exploring specific targets and biomarkers would benefit the prognosis and treatment of STS. Here, we identified RCC1, a guanine-nucleotide exchange factor for Ran, as an oncogene and a potential intervention target in STS. Bioinformatics analysis indicated that RCC1 is highly expressed and correlated with poor prognosis in STS. Functional studies showed that RCC1 knockdown significantly inhibited the cell cycle transition, proliferation and migration of STS cells in vitro, and the growth of STS xenografts in mice. Mechanistically, we identified Skp2 as a downstream target of RCC1 in STS. Loss of RCC1 substantially diminished Skp2 abundance by compromising its protein stability, resulting in the upregulation of p27Kip1 and G1/S transition arrest. Specifically, RCC1 might facilitate the nucleo-cytoplasmic trafficking of Skp2 via direct interaction. As a result, the cytoplasmic retention of Skp2 would further protect it from ubiquitination and degradation. Notably, recovery of Skp2 expression largely reversed the phenotypes induced by RCC1 knockdown in STS cells. Collectively, this study unveils a novel RCC1-Skp2-p27Kip1 axis in STS oncogenesis, which holds promise for improving prognosis and treatment of this formidable malignancy.

Hippo-YAP/TAZ signaling in breast cancer: Reciprocal regulation of microRNAs and implications in precision medicine

Breast cancer is a molecularly heterogeneous disease and the most common female malignancy. In recent years, therapy approaches have evolved to accommodate molecular diversity, with a focus on more biologically based therapies to minimize negative consequences. To regulate cell fate in human breast cells, the Hippo signaling pathway has been associated with the alpha subtype of estrogen receptors. This pathway regulates tissue size, regeneration, and healing, as well as the survival of tissue-specific stem cells, proliferation, and apoptosis in a variety of organs, allowing for cell differentiation. Hippo signaling is mediated by the kinases MST1, MST2, LATS1, and LATS2, as well as the adaptor proteins SAV1 and MOB. These kinases phosphorylate the downstream effectors of the Hippo pathway, yes-associated protein (YAP), and transcriptional coactivator with PDZ-binding motif (TAZ), suppressing the expression of their downstream target genes. The Hippo signaling pathway kinase cascade plays a significant role in all cancers. Understanding the principles of this kinase cascade would prevent the occurrence of breast cancer. In recent years, small noncoding RNAs, or microRNAs, have been implicated in the development of several malignancies, including breast cancer. The interconnections between miRNAs and Hippo signaling pathway core proteins in the breast, on the other hand, remain poorly understood. In this review, we focused on highlighting the Hippo signaling system, its key parts, its importance in breast cancer, and its regulation by miRNAs and other related pathways.

Role of Hippo pathway dysregulation from gastrointestinal premalignant lesions to cancer

BACKGROUND

First identified in Drosophila melanogaster, the Hippo pathway is considered a major regulatory cascade controlling tissue homeostasis and organ development. Hippo signaling components include kinases whose activity regulates YAP and TAZ final effectors. In response to upstream stimuli, YAP and TAZ control transcriptional programs involved in cell proliferation, cytoskeletal reorganization and stemness.

MAIN TEXT

While fine tuning of Hippo cascade components is essential for maintaining the balance between proliferative and non-proliferative signals, pathway signaling is frequently dysregulated in gastrointestinal cancers. Also, YAP/TAZ aberrant activation has been described in conditions characterized by chronic inflammation that precede cancer development, suggesting a role of Hippo effectors in triggering carcinogenesis. In this review, we summarize the architecture of the Hippo pathway and discuss the involvement of signaling cascade unbalances in premalignant lesions of the gastrointestinal tract, providing a focus on the underlying molecular mechanisms.

CONCLUSIONS

The biology of premalignant Hippo signaling dysregulation needs further investigation in order to elucidate the evolutionary trajectories triggering cancer inititation and develop effective early therapeutic strategies targeting the Hippo/YAP pathway.

Skp2: A critical molecule for ubiquitination and its role in cancer

The ubiquitin-proteasome system (UPS) is a multi-step process that serves as the primary pathway for protein degradation within cells. UPS activity also plays a crucial role in regulating various life processes, including the cell cycle, signal transduction, DNA repair, and others. The F-box protein Skp2, a crucial member of the UPS, plays a central role in the development of various diseases. Skp2 controls cancer cell growth and drug resistance by ubiquitinating modifications to a variety of proteins. This review emphasizes the multifaceted role of Skp2 in a wide range of cancers and the mechanisms involved, highlighting the potential of Skp2 as a therapeutic target in cancer. Additionally, we describe the impactful influence exerted by Skp2 in various other diseases beyond cancer.

Regulation of Hippo-YAP/CTGF signaling by combining an HDAC inhibitor and 5-fluorouracil in gastric cancer cells

Histone deacetylase (HDAC) inhibitors diminish carcinogenesis, metastasis, and cancer cell proliferation by inducing death in cancer cells. Tissue regeneration and organ development are highly dependent on the Hippo signaling pathway. Targeting the dysregulated hippo pathway is an excellent approach for cancer treatment. According to the results of this study, the combination of panobinostat, a histone deacetylase inhibitor, and 5-fluorouracil (5-FU), a chemotherapy drug, can act synergistically to induce apoptosis in gastric cancer cells. The combination of panobinostat and 5-FU was more effective in inhibiting cell viability than either treatment alone by elevating the protein levels of cleaved PARP and cleaved caspase-9. By specifically targeting E-cadherin, vimentin, and MMP-9, the combination of panobinostat and 5-FU significantly inhibited cell migration. Additionally, panobinostat significantly increased the anticancer effects of 5-FU by activating Hippo signaling (Mst 1 and 2, Sav1, and Mob1) and inhibiting the Akt signaling pathway. As a consequence, there was a decrease in the amount of Yap protein. The combination therapy of panobinostat with 5-FU dramatically slowed the spread of gastric cancer in a xenograft animal model by deactivating the Akt pathway and supporting the Hippo pathway. Since combination treatment exhibits much higher anti-tumor potential than 5-FU alone, panobinostat effectively potentiates the anti-tumor efficacy of 5-FU. As a result, it is believed that panobinostat and 5-FU combination therapy will be useful as supplemental chemotherapy in the future.

Vasculature is getting Hip(po): Hippo signaling in vascular development and disease

The Hippo signaling pathway regulates developmental organ growth, regeneration, and cell fate decisions. Although the role of the Hippo pathway, and its transcriptional effectors YAP and TAZ, has been well documented in many cell types and species, only recently have the roles for this pathway come to light in vascular development and disease. Experiments in mice, zebrafish, and in vitro have uncovered roles for the Hippo pathway, YAP, and TAZ in vasculogenesis, angiogenesis, and lymphangiogenesis. In addition, the Hippo pathway has been implicated in vascular cancers and cardiovascular diseases, thus identifying it as a potential therapeutic target for the treatment of these conditions. However, despite recent advances, Hippo's role in the vasculature is still underappreciated compared with its role in epithelial tissues. In this review, we appraise our current understanding of the Hippo pathway in blood and lymphatic vessel development and highlight the current knowledge gaps and opportunities for further research.

Immunosensitivity mediated by downregulated AKT1-SKP2 induces anti-PD-1-associated thyroid immune injury

BACKGROUND

Immune checkpoint inhibitors evoke the immune system, which may cause immune-related adverse effects. The predictors and mechanisms of anti-PD-1-associated thyroid immune injury remain unclear.

METHODS

A retrospective analysis is conducted on 518 patients treated with anti PD-1/PD-L1. Firstly, the differences between anti PD-1 and anti PD-L1 are compared on the risk of thyroid immune injury. Then, the predictors of the risk and thyroid function for anti PD-1 related thyroid immune injury are analyzed. Furthermore, the in vitro mechanism of normal thyroid cells (NTHY) is studied. First, the effect of anti PD-1 on the cell viability and immune sensitivity of thyroid cells is observed. Cell viability includes cell proliferation, apoptosis, cell cycle, T4 secretion, while immune sensitivity includes molecular expression and CD8 + T cell aggregation and killing towards NTHY. Then the differentially expressed proteins (DEPs) are screened by protein mass spectrometry. Enrichment of KEGG pathway and annotation of GO function on DEPs are conducted. Human protein-protein interactions are obtained from STRING database. The network is constructed and analyzed using Cytoscape software. In vitro, key proteins and their pathways are validated through overexpression plasmids or inhibitors. The recovery experiment and the immuno-coprecipitation experiment are designed to support the results. In vivo, the key proteins are detected in the thyroid tissue of mice fed with anti PD-1, as well as in the thyroid tissue of patients with Hashimoto's thyroiditis.

RESULTS

Thyroid irAE is associated with female, IgG, FT4, TPOAb, TGAb, TSHI, TFQI, and TSH. Peripheral lymphocytes are associated with thyroid function. In vitro, the NIVO group shows prologed G1 phase, decreased FT4, downregulated PD-L1, upregulated IFN-γ, and more CD8 + T cell infiltration and cytotoxicity. AKT1-SKP2 is chosen as the key protein. AKT1 overexpression and SKP2 inhibitor replies to NIVO and AKT1 overexpression, respectively. Immunoprecipitation shows SKP2 and PD-L1 interaction.

CONCLUSION

Female, impaired thyroid hormone sensitivity and IgG4 contribute to the risk of thyroid irAE, while peripheral blood lymphocyte characteristics affect thyroid function. Anti-PD-1 induces thyroid irAE by downregulating AKT1-SKP2 to enhance thyroid immunosensitivity.

Diacylglycerol lipase alpha promotes hepatocellular carcinoma progression and induces lenvatinib resistance by enhancing YAP activity

As an important hydrolytic enzyme that yields 2-AG and free fatty acids, diacylglycerol lipase alpha (DAGLA) is involved in exacerbating malignant phenotypes and cancer progression, but the role of the DAGLA/2-AG axis in HCC progression remains unclear. Here, we found that the upregulation of components of the DAGLA/2-AG axis in HCC samples is correlated with tumour stage and patient prognosis. In vitro and in vivo experiments demonstrated that the DAGLA/2-AG axis promoted HCC progression by regulating cell proliferation, invasion and metastasis. Mechanistically, the DAGLA/2AG axis significantly inhibited LATS1 and YAP phosphorylation, promoted YAP nuclear translocation and activity, and ultimately led to TEAD2 upregulation and increased PHLDA2 expression, which could be enhanced by DAGLA/2AG-induced activation of the PI3K/AKT pathway. More importantly, DAGLA induced resistance to lenvatinib therapy during HCC treatment. Our study demonstrates that inhibiting the DAGLA/2-AG axis could be a novel therapeutic strategy to inhibit HCC progression and enhance the therapeutic effects of TKIs, which warrant further clinical studies.

Whole-Genome Doubling as a source of cancer: how, when, where, and why?

Chromosome instability is a well-known hallmark of cancer, leading to increased genetic plasticity of tumoral cells, which favors cancer aggressiveness, and poor prognosis. One of the main sources of chromosomal instability are events that lead to a Whole-Genome Duplication (WGD) and the subsequently generated cell polyploidy. In recent years, several studies showed that WGD occurs at the early stages of cell transformation, which allows cells to later become aneuploid, thus leading to cancer progression. On the other hand, other studies convey that polyploidy plays a tumor suppressor role, by inducing cell cycle arrest, cell senescence, apoptosis, and even prompting cell differentiation, depending on the tissue cell type. There is still a gap in understanding how cells that underwent WGD can overcome the deleterious effect on cell fitness and evolve to become tumoral. Some laboratories in the chromosomal instability field recently explored this paradox, finding biomarkers that modulate polyploid cells to become oncogenic. This review brings a historical view of how WGD and polyploidy impact cell fitness and cancer progression, and bring together the last studies that describe the genes helping cells to adapt to polyploidy.

SARM1 promotes the neuroinflammation and demyelination through IGFBP2/NF-κB pathway in experimental autoimmune encephalomyelitis mice

AIM

Multiple sclerosis (MS) is an autoimmune disease, and its typical characteristics are neuroinflammation and the demyelination of neurons in the central nervous system (CNS). Sterile alpha and TIR motif containing 1 (SARM1) is an essential factor mediating axonal degeneration and SARM1 deletion reduces the neuroinflammation in spinal cord injury. This study aimed to explore the roles of SARM1 and its underlying mechanisms in MS.

METHODS

Experimental autoimmune encephalomyelitis (EAE, a model of MS) model was established. Immunostaining, western blot, electron microscope, and HE staining were used to examine the pathological manifestations such as inflammation, demyelination, and neuronal death in SARM1^f/f EAE mice and SARM1^Nestin -CKO EAE mice. In addition, RNA-seq, real-time PCR and double-immunostaining were used to examine the underlying mechanism of SARM1 in EAE mice.

RESULTS

SARM1 was upregulated in neurons of the spinal cords of EAE mice. SARM1 knockout in CNS ameliorated EAE with less neuroinflammation, demyelination, and dead neurons. Mechanically, SARM1 knockout resulted in the reduction of insulin-like growth factor (IGF)-binding protein 2 (IGFBP2) in neurons of EAE mice, which might inhibit the neuroinflammation through inhibiting NF-κB signaling. Finally, activation of NF-κB partially aggravated the neuroinflammation and demyelination deficits of SARM1^Nestin -CKO EAE mice.

CONCLUSIONS

These results identified the unknown role of SARM1 in the promotion of neuroinflammation and demyelination and revealed a novel drug target pathway of SARM1/IGFBP2/NF-κB for MS.

Normalization of hepatic ChREBP activity does not protect against liver disease progression in a mouse model for Glycogen Storage Disease type Ia

BACKGROUND

Glycogen storage disease type 1a (GSD Ia) is an inborn error of metabolism caused by a defect in glucose-6-phosphatase (G6PC1) activity, which induces severe hepatomegaly and increases the risk for liver cancer. Hepatic GSD Ia is characterized by constitutive activation of Carbohydrate Response Element Binding Protein (ChREBP), a glucose-sensitive transcription factor. Previously, we showed that ChREBP activation limits non-alcoholic fatty liver disease (NAFLD) in hepatic GSD Ia. As ChREBP has been proposed as a pro-oncogenic molecular switch that supports tumour progression, we hypothesized that ChREBP normalization protects against liver disease progression in hepatic GSD Ia.

METHODS

Hepatocyte-specific G6pc knockout (L-G6pc^-/-) mice were treated with AAV-shChREBP to normalize hepatic ChREBP activity.

RESULTS

Hepatic ChREBP normalization in GSD Ia mice induced dysplastic liver growth, massively increased hepatocyte size, and was associated with increased hepatic inflammation. Furthermore, nuclear levels of the oncoprotein Yes Associated Protein (YAP) were increased and its transcriptional targets were induced in ChREBP-normalized GSD Ia mice. Hepatic ChREBP normalization furthermore induced DNA damage and mitotic activity in GSD Ia mice, while gene signatures of chromosomal instability, the cytosolic DNA-sensing cGAS-STING pathway, senescence, and hepatocyte dedifferentiation emerged.

CONCLUSIONS

In conclusion, our findings indicate that ChREBP activity limits hepatomegaly while decelerating liver disease progression and protecting against chromosomal instability in hepatic GSD Ia. These results disqualify ChREBP as a therapeutic target for treatment of liver disease in GSD Ia. In addition, they underline the importance of establishing the context-specific roles of hepatic ChREBP to define its therapeutic potential to prevent or treat advanced liver disease.

The Ubiquitin-Proteasome System in Tumor Metabolism

Metabolic reprogramming, which is considered a hallmark of cancer, can maintain the homeostasis of the tumor environment and promote the proliferation, survival, and metastasis of cancer cells. For instance, increased glucose uptake and high glucose consumption, known as the "Warburg effect," play an essential part in tumor metabolic reprogramming. In addition, fatty acids are harnessed to satisfy the increased requirement for the phospholipid components of biological membranes and energy. Moreover, the anabolism/catabolism of amino acids, such as glutamine, cystine, and serine, provides nitrogen donors for biosynthesis processes, development of the tumor inflammatory environment, and signal transduction. The ubiquitin-proteasome system (UPS) has been widely reported to be involved in various cellular biological activities. A potential role of UPS in the metabolic regulation of tumor cells has also been reported, but the specific regulatory mechanism has not been elucidated. Here, we review the role of ubiquitination and deubiquitination modification on major metabolic enzymes and important signaling pathways in tumor metabolism to inspire new strategies for the clinical treatment of cancer.

Cisplatin-Resistant Ovarian Cancer Cells Reveal a Polyploid Phenotype with Remarkable Activation of Nuclear Processes

Background

Tumor recurrence as one of the main causes of cancer death is a big barrier to cancer complete treatment. Various studies denote the possible role of therapeutics in tumor relapse. Cisplatin as one of the generally used chemotherapy agents is supposed to be the source of therapy resistance through formation of polyploid giant cancer cells (PGCCs). Nevertheless, the mechanisms by which PGCCs promote tumor relapse are not fully understood.

Materials and Methods

In this study, we performed experimental and bioinformatic investigations to recognize the mechanisms related to cisplatin resistance. A2780 and SCOV-3 cell lines were treated with cisplatin for 72 hours and were evaluated for their morphology by fluorescent microscopy and DNA content analysis. Furthermore, a microarray dataset of cisplatin-resistant ovarian cancer cells was re-analyzed to determine the significantly altered genes and signaling pathways.

Results

Although cisplatin led to death of considerable fraction of cells in both cell lines, a significant number of survived cells became polyploid. On the other hand, our high throughput analysis determined significant change in expression of 1930 genes which mainly related to gene regulatory mechanisms and nuclear processes. Besides, mTOR, hypoxia, Hippo, and 14-3-3 signaling pathways previously shown to have role in PGCCs were determined.

Conclusion

Taken together, results of this study demonstrated some key biological mechanisms related to cisplatin-resistant polyploid cancer cells.

Extracellular matrix remodeling in tumor progression and immune escape: from mechanisms to treatments

The malignant tumor is a multi-etiological, systemic and complex disease characterized by uncontrolled cell proliferation and distant metastasis. Anticancer treatments including adjuvant therapies and targeted therapies are effective in eliminating cancer cells but in a limited number of patients. Increasing evidence suggests that the extracellular matrix (ECM) plays an important role in tumor development through changes in macromolecule components, degradation enzymes and stiffness. These variations are under the control of cellular components in tumor tissue via the aberrant activation of signaling pathways, the interaction of the ECM components to multiple surface receptors, and mechanical impact. Additionally, the ECM shaped by cancer regulates immune cells which results in an immune suppressive microenvironment and hinders the efficacy of immunotherapies. Thus, the ECM acts as a barrier to protect cancer from treatments and supports tumor progression. Nevertheless, the profound regulatory network of the ECM remodeling hampers the design of individualized antitumor treatment. Here, we elaborate on the composition of the malignant ECM, and discuss the specific mechanisms of the ECM remodeling. Precisely, we highlight the impact of the ECM remodeling on tumor development, including proliferation, anoikis, metastasis, angiogenesis, lymphangiogenesis, and immune escape. Finally, we emphasize ECM "normalization" as a potential strategy for anti-malignant treatment.

PRMT5 determines the pattern of polyploidization and prevents liver from cirrhosis and carcinogenesis

Human hepatocellular carcinoma (HCC) occurs almost exclusively in cirrhotic livers. Here, we report that hepatic loss of protein arginine methyltransferase 5 (PRMT5) in mice is sufficient to cause cirrhosis and HCC in a clinically relevant way. Furthermore, pathological polyploidization induced by hepatic loss of PRMT5 promotes liver cirrhosis and hepatic tumorigenesis in aged liver. The loss of PRMT5 leads to hyper-accumulation of P21 and endoreplication-dependent formation of pathological mono-nuclear polyploid hepatocytes. PRMT5 and symmetric dimethylation at histone H4 arginine 3 (H4R3me2s) directly associate with chromatin of P21 to suppress its transcription. More importantly, loss of P21 rescues the pathological mono-nuclear polyploidy and prevents PRMT5-deficiency-induced liver cirrhosis and HCC. Thus, our results indicate that PRMT5-mediated symmetric dimethylation at histone H4 arginine 3 (H4R3me2s) is crucial for preventing pathological polyploidization, liver cirrhosis and tumorigenesis in mouse liver.

Possible Future Avenues for Rheumatoid Arthritis Therapeutics: Hippo Pathway

Rheumatoid arthritis (RA) is a persistent systemic autoimmune disease with the hallmarks of swelling of the joint, joint tenderness, and progressive joint destruction, which may cause synovial inflammation and pannus as a basic pathological change, resulting in joint malformations and serious disorders. At present, the precise etiology and mechanism of pathogenesis of RA are unknown. The imbalance of immune homeostasis is the origin of RA. Hippo pathway is widely expressed in a range of cell lineages and plays a fundamental role in maintaining the immune steady state and may be involved in the pathogenic mechanism of RA. This study reviews the progress of Hippo pathway and its main members in the pathogenesis of RA from three aspects: regulating the maintenance of autoimmune homeostasis, promoting the pathogenicity of synovial fibroblasts and regulating the differentiation of osteoclasts. The study also presents a new way to recognize the pathogenesis of rheumatoid arthritis, which is favorable for finding a new way for treating the rheumatoid arthritis.

Small-molecule compounds inhibiting S-phase kinase-associated protein 2: A review

S-phase kinase-associated protein 2 (Skp2) is a substrate-specific adaptor in Skp1-CUL1-ROC1-F-box E3 ubiquitin ligases and widely regarded as an oncogene. Therefore, Skp2 has remained as an active anticancer research topic since its discovery. Accordingly, the structure of Skp2 has been solved and numerous Skp2 inhibiting compounds have been identified. In this review, we would describe the structural features of Skp2, introduce the ubiquitination function of SCF^Skp2, and summarize the diverse natural and synthetic Skp2 inhibiting compounds reported to date. The IC₅₀ data of the Skp2 inhibitors or inhibiting compounds in various kinds of tumors at cellular levels implied that the cancer type, stage and pathological mechanisms should be taken into consideration when selecting Skp2-inhibiting compound for cancer treatment.

The Effect of Circumscribed Exposure to the Pan-Aurora Kinase Inhibitor VX-680 on Proliferating Euploid Cells

Small molecule inhibitors of aurora kinases are currently being investigated in oncology clinical trials. The long-term effects of these inhibitors on proliferating euploid cells have not been adequately studied. We examined the effect of the reversible pan-aurora kinase inhibitor VX-680 on p53-competent human euploid cells. Circumscribed treatment with VX-680 blocked cytokinesis and arrested cells in G1 or a G1-like status. Approximately 70% of proliferatively arrested cells had 4N DNA content and abnormal nuclei. The remaining 30% of cells possessed 2N DNA content and normal nuclei. The proliferative arrest was not due to the activation of the tumor suppressor Rb and was instead associated with rapid induction of the p53–p21 pathway and p16. The induction was particularly evident in cells with nuclear abnormalities but was independent of activation of the DNA damage response. All of these effects were correlated with the potent inhibition of aurora kinase B. After release from VX-680, the cells with normal nuclei robustly resumed proliferation whereas the cells with abnormal nuclei underwent senescence. Irrespective of their nuclear morphology or DNA content, cells pre-treated with VX-680 failed to grow in soft agar or form tumors in mice. Our findings indicate that an intermittent treatment strategy might minimize the on-target side effects of Aurora Kinase B (AURKB) inhibitory therapies. The strategy allows a significant fraction of dividing normal cells to resume proliferation.

Tubular cell polyploidy protects from lethal acute kidney injury but promotes consequent chronic kidney disease

Acute kidney injury (AKI) is frequent, often fatal and, for lack of specific therapies, can leave survivors with chronic kidney disease (CKD). We characterize the distribution of tubular cells (TC) undergoing polyploidy along AKI by DNA content analysis and single cell RNA-sequencing. Furthermore, we study the functional roles of polyploidization using transgenic models and drug interventions. We identify YAP1-driven TC polyploidization outside the site of injury as a rapid way to sustain residual kidney function early during AKI. This survival mechanism comes at the cost of senescence of polyploid TC promoting interstitial fibrosis and CKD in AKI survivors. However, targeting TC polyploidization after the early AKI phase can prevent AKI-CKD transition without influencing AKI lethality. Senolytic treatment prevents CKD by blocking repeated TC polyploidization cycles. These results revise the current pathophysiological concept of how the kidney responds to acute injury and identify a novel druggable target to improve prognosis in AKI survivors.

Acute kidney injury is frequent, often fatal and can leave survivors with chronic kidney disease. Here the authors show that tubular cell polyploidy reduces early fatality sustaining residual function but promotes chronic kidney disease, which can be prevented by blocking YAP1

Emerging roles of the RNA modifications N6-methyladenosine and adenosine-to-inosine in cardiovascular diseases

Cardiovascular diseases lead the mortality and morbidity disease metrics worldwide. A multitude of chemical base modifications in ribonucleic acids (RNAs) have been linked with key events of cardiovascular diseases and metabolic disorders. Named either RNA epigenetics or epitranscriptomics, the post-transcriptional RNA modifications, their regulatory pathways, components, and downstream effects substantially contribute to the ways our genetic code is interpreted. Here we review the accumulated discoveries to date regarding the roles of the two most common epitranscriptomic modifications, N6-methyl-adenosine (m6A) and adenosine-to-inosine (A-to-I) editing, in cardiovascular disease.

Structural basis and molecular mechanism of biased GPBAR signaling in regulating NSCLC cell growth via YAP activity

The G protein-coupled bile acid receptor (GPBAR) is the membrane receptor for bile acids and a driving force of the liver-bile acid-microbiota-organ axis to regulate metabolism and other pathophysiological processes. Although GPBAR is an important therapeutic target for a spectrum of metabolic and neurodegenerative diseases, its activation has also been found to be linked to carcinogenesis, leading to potential side effects. Here, via functional screening, we found that two specific GPBAR agonists, R399 and INT-777, demonstrated strikingly different regulatory effects on the growth and apoptosis of non-small cell lung cancer (NSCLC) cells both in vitro and in vivo. Further mechanistic investigation showed that R399-induced GPBAR activation displayed an obvious bias for β-arrestin 1 signaling, thus promoting YAP signaling activation to stimulate cell proliferation. Conversely, INT-777 preferentially activated GPBAR-Gs signaling, thus inactivating YAP to inhibit cell proliferation and induce apoptosis. Phosphorylation of GPBAR by GRK2 at S310/S321/S323/S324 sites contributed to R399-induced GPBAR-β-arrestin 1 association. The cryoelectron microscopy (cryo-EM) structure of the R399-bound GPBAR-Gs complex enabled us to identify key interaction residues and pivotal conformational changes in GPBAR responsible for the arrestin signaling bias and cancer cell proliferation. In summary, we demonstrate that different agonists can regulate distinct functions of cell growth and apoptosis through biased GPBAR signaling and control of YAP activity in a NSCLC cell model. The delineated mechanism and structural basis may facilitate the rational design of GPBAR-targeting drugs with both metabolic and anticancer benefits.

Polyploidization of Hepatocytes: Insights into the Pathogenesis of Liver Diseases

Polyploidization is a process by which cells are induced to possess more than two sets of chromosomes. Although polyploidization is not frequent in mammals, it is closely associated with development and differentiation of specific tissues and organs. The liver is one of the mammalian organs that displays ploidy dynamics in physiological homeostasis during its development. The ratio of polyploid hepatocytes increases significantly in response to hepatic injury from aging, viral infection, iron overload, surgical resection, or metabolic overload, such as that from non-alcoholic fatty liver diseases (NAFLDs). One of the unique features of NAFLD is the marked heterogeneity of hepatocyte nuclear size, which is strongly associated with an adverse liver-related outcome, such as hepatocellular carcinoma, liver transplantation, and liver-related death. Thus, hepatic polyploidization has been suggested as a potential driver in the progression of NAFLDs that are involved in the control of the multiple pathogenicity of the diseases. However, the importance of polyploidy in diverse pathophysiological contexts remains elusive. Recently, several studies reported successful improvement of symptoms of NAFLDs by reducing pathological polyploidy or by controlling cell cycle progression in animal models, suggesting that better understanding the mechanisms of pathological hepatic polyploidy may provide insights into the treatment of hepatic disorders.

Molecular Mechanisms and Biomarkers Associated with Chemotherapy-Induced AKI

Acute kidney injury (AKI) is a life-threatening condition characterized by a rapid and transient decrease in kidney function. AKI is part of an array of conditions collectively defined as acute kidney diseases (AKD). In AKD, persistent kidney damage and dysfunction lead to chronic kidney disease (CKD) over time. A variety of insults can trigger AKI; however, chemotherapy-associated nephrotoxicity is increasingly recognized as a significant side effect of chemotherapy. New biomarkers are urgently needed to identify patients at high risk of developing chemotherapy-associated nephrotoxicity and subsequent AKI. However, a lack of understanding of cellular mechanisms that trigger chemotherapy-related nephrotoxicity has hindered the identification of effective biomarkers to date. In this review, we aim to (1) describe the known and potential mechanisms related to chemotherapy-induced AKI; (2) summarize the available biomarkers for early AKI detection, and (3) raise awareness of chemotherapy-induced AKI.

Menin directs regionalized decidual transformation through epigenetically setting PTX3 to balance FGF and BMP signaling

During decidualization in rodents, uterine stroma undergoes extensive reprograming into distinct cells, forming the discrete regions defined as the primary decidual zone (PDZ), the secondary decidual zone (SDZ) and the layer of undifferentiated stromal cells respectively. Here we show that uterine deletion of Men1, a member of the histone H3K4 methyltransferase complex, disrupts the terminal differentiation of stroma, resulting in chaotic decidualization and pregnancy failure. Genome-wide epigenetic profile reveals that Men1 binding in chromatin recapitulates H3K4me3 distribution. Further transcriptomic investigation demonstrates that Men1 directly regulates the expression of PTX3, an extra-cellular trap for FGF2 in decidual cells. Decreased Ptx3 upon Men1 ablation leads to aberrant activation of ERK1/2 in the SDZ due to the unrestrained FGF2 signal emanated from undifferentiated stromal cells, which blunt BMP2 induction and decidualization. In brief, our study provides genetic and molecular mechanisms for epigenetic rewiring mediated decidual regionalization by Men1 and sheds new light on pregnancy maintenance.

The decidualization of endometrial stroma is critical for pregnancy maintenance. Here the authors reveal that Menin ensures the expression of PTX3 through H3K4me3 modification, to balance the BMP and FGF signal in the decidua for normal pregnancy.

PI3K signaling specifies proximal-distal fate by driving a developmental gene regulatory network in SOX9+ mouse lung progenitors

The tips of the developing respiratory buds are home to important progenitor cells marked by the expression of SOX9 and ID2. Early in embryonic development (prior to E13.5), SOX9+progenitors are multipotent, generating both airway and alveolar epithelium, but are selective progenitors of alveolar epithelial cells later in development. Transcription factors, including Sox9, Etv5, Irx, Mycn, and Foxp1/2 interact in complex gene regulatory networks to control proliferation and differentiation of SOX9+progenitors. Molecular mechanisms by which these transcription factors and other signaling pathways control chromatin state to establish and maintain cell-type identity are not well-defined. Herein, we analyze paired gene expression (RNA-Seq) and chromatin accessibility (ATAC-Seq) data from SOX9+ epithelial progenitor cells (EPCs) during embryonic development in Mus musculus. Widespread changes in chromatin accessibility were observed between E11.5 and E16.5, particularly at distal cis-regulatory elements (e.g. enhancers). Gene regulatory network (GRN) inference identified a common SOX9+ progenitor GRN, implicating phosphoinositide 3-kinase (PI3K) signaling in the developmental regulation of SOX9+ progenitor cells. Consistent with this model, conditional ablation of PI3K signaling in the developing lung epithelium in mouse resulted in an expansion of the SOX9+ EPC population and impaired airway epithelial cell differentiation. These data demonstrate that PI3K signaling is required for epithelial patterning during lung organogenesis, and emphasize the combinatorial power of paired RNA and ATAC seq in defining regulatory networks in development.

miR-378d suppresses malignant phenotype of ESCC cells through AKT signaling

Background

Post-resistance progress in paclitaxel (PTX) treatment remains a major challenge in tumor treatment. A high dose of PTX was used for cell lines to analyze the changes in molecular expression. The miR-378d was sharply reduced in surviving cells, but the role of miR-378d in Esophageal squamous cell carcinoma (ESCC) remained unclear.

Methods

We analyzed the relationship between miR-378d expression and the clinicopathological features of ESCC. We constructed miR-378d silent expression cell lines to study phenotypes and molecular mechanisms.

Results

The miR-378d expression was associated with good prognosis in patients with ESCC. miR-378d inhibition promoted chemo-resistance, monoclonal formation, EMT, migration, invasion, stemness, and metastasis of ESCC cells. miR-378d can target downregulated AKT1.

Conclusions

Therefore, miR-378d expression is a good prognostic factor of patients with ESCC and regulates the malignant phenotype of tumor cells through AKT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02403-y.

The Hippo Signaling Pathway in Cancer: A Cell Cycle Perspective

Simple Summary

Cancer is increasingly viewed as a cell cycle disease in that the dysregulation of the cell cycle machinery is a common feature in cancer. The Hippo signaling pathway consists of a core kinase cascade as well as extended regulators, which together control organ size and tissue homeostasis. The aberrant expression of cell cycle regulators and/or Hippo pathway components contributes to cancer development, and for this reason, we specifically focus on delineating the roles of the Hippo pathway in the cell cycle. Improving our understanding of the Hippo pathway from a cell cycle perspective could be used as a powerful weapon in the cancer battlefield.

Abstract

Cell cycle progression is an elaborate process that requires stringent control for normal cellular function. Defects in cell cycle control, however, contribute to genomic instability and have become a characteristic phenomenon in cancers. Over the years, advancement in the understanding of disrupted cell cycle regulation in tumors has led to the development of powerful anti-cancer drugs. Therefore, an in-depth exploration of cell cycle dysregulation in cancers could provide therapeutic avenues for cancer treatment. The Hippo pathway is an evolutionarily conserved regulator network that controls organ size, and its dysregulation is implicated in various types of cancers. Although the role of the Hippo pathway in oncogenesis has been widely investigated, its role in cell cycle regulation has not been comprehensively scrutinized. Here, we specifically focus on delineating the involvement of the Hippo pathway in cell cycle regulation. To that end, we first compare the structural as well as functional conservation of the core Hippo pathway in yeasts, flies, and mammals. Then, we detail the multi-faceted aspects in which the core components of the mammalian Hippo pathway and their regulators affect the cell cycle, particularly with regard to the regulation of E2F activity, the G1 tetraploidy checkpoint, DNA synthesis, DNA damage checkpoint, centrosome dynamics, and mitosis. Finally, we briefly discuss how a collective understanding of cell cycle regulation and the Hippo pathway could be weaponized in combating cancer.

CircCRIM1 Promotes Hepatocellular Carcinoma Proliferation and Angiogenesis by Sponging miR-378a-3p and Regulating SKP2 Expression

Mounting evidence has demonstrated that circular RNAs have an important function in tumorigenesis and cancer evolvement. CircCRIM1 has been shown to be a poor prognostic element in multiple human malignancies. However, the clinical significance and mechanism of circCRIM1 in hepatocellular carcinoma (HCC) is still unclear. The present study confirmed the expression level of circCRIM1 using quantitative real-time PCR. In addition, circCRIM1 siRNA and overexpression vectors were used for transfection into LM3 or Huh7 cells to down- or up-regulate the expression of circCRIM1. In vitro and in vivo experiments were performed to explore the function of circCRIM1 in HCC. RNA pull-down, RNA immunoprecipitation, fluorescent in situ hybridization, and luciferase reporter assays were conducted to confirm the relationship between miR-378a-3p and circCRIM1 or S-phase kinase-associated protein 2 (SKP2) in HCC. Then, circCRIM1 was up-regulated in HCC and its expression level was significantly associated with poor prognosis and clinicopathologic characteristics. CircCRIM1 enhanced the proliferation and angiogenesis of HCC cells in vitro and promoted xenograft growth in vivo. Moreover, circCRIM1 upregulated the expression of SKP2 by functioning as a sponge for miR-378a-3p. These findings suggest that circCRIM1 boosts the HCC progression via the miR-378-3p/SKP2 axis and may act as a crucial epigenetic therapeutic molecule target in HCC.

Loss of SPTBN1 Suppresses Autophagy Via SETD7-mediated YAP Methylation in Hepatocellular Carcinoma Initiation and Development

BACKGROUND & AIMS

Loss of Spectrin beta, non-erythrocytic 1 (SPTBN1) plays an important role in the carcinogenesis of hepatocellular carcinoma (HCC); however, the mechanisms underlying its involvement remain poorly understood. Defects in autophagy contribute to hepatic tumor formation. Hence, in this study, we explored the role and mechanism of SPTBN1 in the autophagy of hepatic stem cells (HSCs) and HCC cells.

METHODS

Expansion, autophagy, and malignant transformation of HSCs were detected in the injured liver of Sptbn1^+/- mice induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine treatment. Hippo pathway and Yes-associated protein (YAP) stabilization were examined in isolated HSCs, Huh-7, and PLC/PRF/5 HCC cells and hepatocytes with or without loss of SPTBN1.

RESULTS

We found that heterozygous SPTBN1 knockout accelerated liver tumor development with 3,5-diethoxycarbonyl-1,4-dihydrocollidine induction. Rapamycin promoted autophagy in murine HSCs and reversed the increased malignant transformation induced by heterozygous SPTBN1 deletion. Loss of SPTBN1 also decreased autophagy and increased YAP stability and nuclear localization in human HCC cells and tissues, whereas YAP inhibition attenuated the effects of SPTBN1 deficiency on autophagy. Finally, we found that SPTBN1 positively regulated the expression of suppressor of variegation 3-9-enhancer of zeste-trithorax domain containing lysine methyltransferase 7 to promote YAP methylation, which may lead to YAP degradation and inactivation.

CONCLUSIONS

Our findings provide the first demonstration that loss of SPTBN1 impairs autophagy of HSCs to promote expansion and malignant transformation during hepatocarcinogenesis. SPTBN1 also cooperates with suppressor of variegation 3-9-enhancer of zeste-trithorax domain containing lysine methyltransferase 7 to inactive YAP, resulting in enhanced autophagy of HCC cells. These results may open new avenues targeting SPTBN1 for the prevention and treatment of HCC.

Polyploidy control in hepatic health and disease

A balanced increase in DNA content (ploidy) is observed in some human cell types, including bone-resorbing osteoclasts, platelet-producing megakaryocytes, cardiomyocytes or hepatocytes. The impact of increased hepatocyte ploidy on normal physiology and diverse liver pathologies is still poorly understood. Recent findings suggest swift genetic adaptation to hepatotoxic stress and the protection from malignant transformation as beneficial effects. Herein, we discuss the molecular mechanisms regulating hepatocyte polyploidisation and its implication for different liver diseases and hepatocellular carcinoma. We report on centrosomes' role in limiting polyploidy by activating the p53 signalling network (via the PIDDosome multiprotein complex) and we discuss the role of this pathway in liver disease. Increased hepatocyte ploidy is a hallmark of hepatic inflammation and may play a protective role against liver cancer. Our evolving understanding of hepatocyte ploidy is discussed from the perspective of its potential clinical application for risk stratification, prognosis, and novel therapeutic strategies in liver disease and hepatocellular carcinoma.

Glycogen accumulation and phase separation drives liver tumor initiation

Glucose consumption is generally increased in tumor cells to support tumor growth. Interestingly, we report that glycogen accumulation is a key initiating oncogenic event during liver malignant transformation. We found that glucose-6-phosphatase (G6PC) catalyzing the last step of glycogenolysis is frequently downregulated to augment glucose storage in pre-malignant cells. Accumulated glycogen undergoes liquid-liquid phase separation, which results in the assembly of the Laforin-Mst1/2 complex and consequently sequesters Hippo kinases Mst1/2 in glycogen liquid droplets to relieve their inhibition on Yap. Moreover, G6PC or another glycogenolysis enzyme-liver glycogen phosphorylase (PYGL) deficiency in both human and mice results in glycogen storage disease along with liver enlargement and tumorigenesis in a Yap-dependent manner. Consistently, elimination of glycogen accumulation abrogates liver growth and cancer incidence, whereas increasing glycogen storage accelerates tumorigenesis. Thus, we concluded that cancer-initiating cells adapt a glycogen storing mode, which blocks Hippo signaling through glycogen phase separation to augment tumor incidence.

Astrocytic YAP prevents the demyelination through promoting expression of cholesterol synthesis genes in experimental autoimmune encephalomyelitis

Cholesterols are the main components of myelin, and are mainly synthesized in astrocytes and transported to oligodendrocytes and neurons in the adult brain. It has been reported that Hippo/yes-associated protein (YAP) pathways are involved in cholesterol synthesis in the liver, however, it remains unknown whether YAP signaling can prevent the demyelination through promoting cholesterol synthesis in experimental autoimmune encephalomyelitis (EAE), a commonly used animal model of multiple sclerosis characterized by neuroinflammation and demyelination. Here, we found that YAP was upregulated and activated in astrocytes of spinal cords of EAE mice through suppression of the Hippo pathway. YAP deletion in astrocytes aggravated EAE with earlier onset, severer inflammatory infiltration, demyelination, and more loss of neurons. Furthermore, we found that the neuroinflammation was aggravated and the proliferation of astrocytes was decreased in YAPGFAP-CKO EAE mice. Mechanically, RNA-seq revealed that the expression of cholesterol-synthesis pathway genes such as HMGCS1 were decreased in YAP-/- astrocytes. qPCR, western blot, and immunostaining further confirmed the more significant reduction of HMGCS1 in spinal cord astrocytes of YAPGFAP-CKO EAE mice. Interestingly, upregulation of cholesterol-synthesis pathways by diarylpropionitrile (DPN) (an ERβ-ligand, to upregulate the expression of HMGCS1) treatment partially rescued the demyelination deficits in YAPGFAP-CKO EAE mice. Finally, activation of YAP by XMU-MP-1 treatment promoted the expression of HMGCS1 in astrocytes and partially rescued the demyelination and inflammatory infiltration deficits in EAE mice. These findings identify unrecognized functions of astrocytic YAP in the prevention of demyelination through promoting cholesterol synthesis in EAE, and reveal a novel pathway of YAP/HMGCS1 for cholesterol synthesis in EAE pathology.

Polyploidy in development and tumor models in Drosophila

Polyploidy, a cell status defined as more than two sets of genomic DNA, is a conserved strategy across species that can increase cell size and biosynthetic production, but the functional aspects of polyploidy are nuanced and vary across cell types. Throughout Drosophila developmental stages (embryo, larva, pupa and adult), polyploid cells are present in numerous organs and help orchestrate development while contributing to normal growth, well-being and homeostasis of the organism. Conversely, increasing evidence has shown that polyploid cells are prevalent in Drosophila tumors and play important roles in tumor growth and invasiveness. Here, we summarize the genes and pathways involved in polyploidy during normal and tumorigenic development, the mechanisms underlying polyploidization, and the functional aspects of polyploidy in development, homeostasis and tumorigenesis in the Drosophila model.

cGAS-STING Signaling Pathway and Liver Disease: From Basic Research to Clinical Practice

The cGAS-STING signaling pathway is an autoimmune inflammatory pathway that can trigger the expression of a series of inflammatory factors represented by type 1 interferon. Recent studies have found that the cGAS-STING signaling pathway played a significant role in liver physiology and was closely related to the progress of liver diseases. For example, activating the cGAS-STING signaling pathway could significantly inhibit hepatitis B virus (HBV) replication in vivo. Moreover, the cGAS-STING signaling pathway was also closely associated with tumor immunity in hepatocellular carcinoma (HCC). This review summarized the role of the cGAS-STING signaling pathway in several common liver diseases, especially the current application of the cGAS-STING signaling pathway in liver disease treatment, and prospected its future research, which provided a new idea for understanding and treating liver diseases.

Combined intermittent fasting and ERK inhibition enhance the anti-tumor effects of chemotherapy via the GSK3β-SIRT7 axis

Dietary interventions such as intermittent fasting (IF) have emerged as an attractive strategy for cancer therapies; therefore, understanding the underlying molecular mechanisms is pivotal. Here, we find SIRT7 decline markedly attenuates the anti-tumor effect of IF. Mechanistically, AMP-activated protein kinase (AMPK) phosphorylating SIRT7 at T263 triggers further phosphorylation at T255/S259 by glycogen synthase kinase 3β (GSK3β), which stabilizes SIRT7 by decoupling E3 ligase UBR5. SIRT7 hyperphosphorylation achieves anti-tumor activity by disrupting the SKP2-SCF E3 ligase, thus preventing SKP2-mediated K63-linked AKT polyubiquitination and subsequent activation. In contrast, GSK3β-SIRT7 axis is inhibited by EGF/ERK2 signaling, with ERK2 inactivating GSK3β, thus accelerating SIRT7 degradation. Unfavorably, glucose deprivation or chemotherapy hijacks the GSK3β-SIRT7 axis via ERK2, thus activating AKT and ensuring survival. Notably, Trametinib, an FDA-approved MEK inhibitor, enhances the efficacy of combination therapy with doxorubicin and IF. Overall, we have revealed the GSK3β-SIRT7 axis that must be fine-tuned in the face of the energetic and oncogenic stresses in malignancy.

The combination of intermittent fasting and chemotherapy can improve the response to treatment. Here, the authors show that SIRT7 activation is required to inactivate Akt during intermittent fasting and that the combination of intermittent fasting and inhibitors that block the Erk pathway can improve efficacy of treatment.

Cellular feedback dynamics and multilevel regulation driven by the hippo pathway

The Hippo pathway is a dynamic cellular signalling nexus that regulates differentiation and controls cell proliferation and death. If the Hippo pathway is not precisely regulated, the functionality of the upstream kinase module is impaired, which increases nuclear localisation and activity of the central effectors, the transcriptional co-regulators YAP and TAZ. Pathological YAP and TAZ hyperactivity consequently cause cancer, fibrosis and developmental defects. The Hippo pathway controls an array of fundamental cellular processes, including adhesion, migration, mitosis, polarity and secretion of a range of biologically active components. Recent studies highlight that spatio-temporal regulation of Hippo pathway components are central to precisely controlling its context-dependent dynamic activity. Several levels of feedback are integrated into the Hippo pathway, which is further synergized with interactors outside of the pathway that directly regulate specific Hippo pathway components. Likewise, Hippo core kinases also ‘moonlight’ by phosphorylating multiple substrates beyond the Hippo pathway and thereby integrates further flexibility and robustness in the cellular decision-making process. This topic is still in its infancy but promises to reveal new fundamental insights into the cellular regulation of this therapeutically important pathway. We here highlight recent advances emphasising feedback dynamics and multilevel regulation of the Hippo pathway with a focus on mitosis and cell migration, as well as discuss potential productive future research avenues that might reveal novel insights into the overall dynamics of the pathway.

Coregulation of pathways in lung cancer patients with EGFR mutation: therapeutic opportunities

Epidermal growth factor receptor (EGFR) mutations in lung adenocarcinoma are a frequent class of driver mutations. Single EGFR tyrosine kinase inhibitor (TKI) provides substantial clinical benefit, but almost nil radiographic complete responses. Patients invariably progress, although survival can reach several years with post-treatment therapies, including EGFR TKIs, chemotherapy or other procedures. Endeavours have been clinically oriented to manage the acquisition of EGFR TKI-resistant mutations; however, basic principles on cancer evolution have not been considered in clinical trials. For years, evidence has displayed rapidly adaptive mechanisms of resistance to selective monotherapy, posing several dilemmas for the practitioner. Strict adherence to non-small cell lung cancer (NSCLC) guidelines is not always practical for addressing the clinical progression that EGFR-mutant lung adenocarcinoma patients suffer. The purpose of this review is to highlight regulatory mechanisms and signalling pathways that cause therapy-induced resistance to EGFR TKIs. It suggests combinatorial therapies that target EGFR, as well as potential mechanisms underlying EGFR-mutant NSCLC, alerting the reader to clinical opportunities that may lead to a deeper and more durable response. Molecular reprogramming contributes to EGFR TKI resistance, and the compiled information is relevant in understanding the development of new combined targeted strategies in EGFR-mutant NSCLC.

m6A Methyltransferase 3 Promotes the Proliferation and Migration of Gastric Cancer Cells through the m6A Modification of YAP1

Gastric cancer is the most common gastrointestinal tumor with an increasing incidence. Furthermore, advanced gastric cancer is more common, but the mechanism underlying the proliferation and metastasis of gastric cancer has not been thoroughly explored. N6-methyladenosine (m6A) methyltransferase 3 (METTL3) may be involved in the proliferation and metastasis of gastric cancer. Therefore, Yes-associated protein 1 (YAP1) in the Hippo pathway was selected as the target, and the relationship between METTL3 and the proliferation and metastasis of gastric cancer was proved through a series of experiments. This research showed that the expression of m6A and METTL3 was upregulated in human gastric cancer tissues and gastric cancer cell lines. After lentiviral transfection, METTL3 silencing in AGS (human gastric adenocarcinoma cell line AGS) and MKN-45 (human gastric cancer cell line MKN-45) gastric cancer cell lines directly inhibited the proliferation, aggressiveness, and migration of gastric cancer cells. Mechanically, the inhibition of the YAP1-TEAD signaling pathway by peptide 17 reduces m6A methylation and the total mRNA level of YAP1. It also eliminates the promoting effect of METTL3 on the proliferation and migration of gastric cancer cells. In turn, the overexpression of YAP1 eliminates the inhibitory effect of METTL3 silencing on the proliferation, migration, and invasion of gastric cancer cells. This article proved that m6A methyltransferase METTL3 promoted the proliferation and migration of gastric cancer cells through the m6A modification of YAP1.

Oncogenic PAX6 elicits CDK4/6 inhibitor resistance by epigenetically inactivating the LATS2-Hippo signaling pathway

Intrinsic resistance to CDK4/6 inhibitors hinders their clinical utility in cancer treatment. Furthermore, the predictive markers of CDK4/6 inhibitors in gastric cancer (GC) remain incompletely described. Here, we found that PAX6 expression was negatively correlated with the response to palbociclib in vitro and in vivo in GC. We observed that the PAX6 expression level was negatively correlated with the overall survival of GC patients and further showed that PAX6 can promote GC cell proliferation and the cell cycle. The cell cycle is regulated by the interaction of cyclins with their partner serine/threonine cyclin-dependent kinases (CDKs), and the G1/S-phase transition is the main target of CDK4/6 inhibitors. Therefore, we tested whether PAX6 expression was correlated with the GC response to palbociclib. We found that PAX6 hypermethylates the promoter of LATS2 and inactivates the Hippo pathway, which upregulates cyclin D1 (CCND1) expression. This results in a suppressed response to palbociclib in GC. Furthermore, we found that the induction of the Hippo signaling pathway or treatment with a DNA methylation inhibitor could overcome PAX6-induced palbociclib resistance in GC. These findings uncover a tumor promoter function of PAX6 in GC and establish overexpressed PAX6 as a mechanism of resistance to palbociclib.

Context-dependent effects of whole-genome duplication during mammary tumor recurrence

Whole-genome duplication (WGD) generates polyploid cells possessing more than two copies of the genome and is among the most common genetic abnormalities in cancer. The frequency of WGD increases in advanced and metastatic tumors, and WGD is associated with poor prognosis in diverse tumor types, suggesting a functional role for polyploidy in tumor progression. Experimental evidence suggests that polyploidy has both tumor-promoting and suppressing effects, but how polyploidy regulates tumor progression remains unclear. Using a genetically engineered mouse model of Her2-driven breast cancer, we explored the prevalence and consequences of whole-genome duplication during tumor growth and recurrence. While primary tumors in this model are invariably diploid, nearly 40% of recurrent tumors undergo WGD. WGD in recurrent tumors was associated with increased chromosomal instability, decreased proliferation and increased survival in stress conditions. The effects of WGD on tumor growth were dependent on tumor stage. Surprisingly, in recurrent tumor cells WGD slowed tumor formation, growth rate and opposed the process of recurrence, while WGD promoted the growth of primary tumors. These findings highlight the importance of identifying conditions that promote the growth of polyploid tumors, including the cooperating genetic mutations that allow cells to overcome the barriers to WGD tumor cell growth and proliferation.