PAK1-mediated MORC2 phosphorylation promotes gastric tumorigenesis

A select inhibitor of MORC2 encapsulated by chimeric membranecoated DNA nanocage target alleviation TNBC progression

Triple-negative breast cancer (TNBC) is the most malignant type of breast cancer and lacks effective targeted therapeutic drugs, resulting in a high recurrence rate and worse outcome. In this study, bioinformatic analysis and a series of experiments demonstrated that MOCR2 was highly expressed in TNBC and closely associated with poor prognosis, indicating that MOCR2 may be a potential therapeutic target for TNBC. Subsequently, Angoline was identified as an inhibitor of MORC2 protein by high-throughput screening and can significantly kill the TNBC cells by blocking cell cycle and inducing apoptosis. Furthermore, the biomimetic nanodrug delivery system (PMD) was designed by encapsulating tetrahedral DNA nanostructures with biomimetic cell membrane, and it can efficiently evade the phagocytosis of immune system and target TNBC tissue. Additionally, PMD can markedly enhance the killing effect of Angoline on TNBC tumors. Therefore, PMD-enveloped Angoline provide a highly effective targeted therapeutic regimen for TNBC and may improve the outcome for patients with TNBC.

Biological functions and molecular mechanisms of MORC2 in human diseases

Microrchidia family CW-type zinc finger 2 (MORC2) is a nuclear protein that has been highly conserved throughout evolution. MORC2 consists of an ATPase domain at the N-terminus, a CW-type zinc finger domain in the middle, and coiled-coil domains at the C-terminus. MORC2 is involved in various important biological processes such as transcriptional regulation, chromatin remodeling, DNA damage repair, and metabolism. Recent studies suggest that MORC2 may serve as a potential biomarker and therapeutic target for hereditary neurological diseases and cancers. However, the exact molecular functions and pathogenic mechanisms of MORC2 in human diseases remain to be explored. In this review, we provide an overview of recent advancements in understanding the molecular functions of MORC2, as well as the characteristics and mechanisms of MORC2-related diseases, which will be valuable for future studies.

MORC2 phosphorylation fine tunes its DNA compaction activity

Variants in the poorly characterised oncoprotein, MORC2, a chromatin remodelling ATPase, lead to defects in epigenetic regulation and DNA damage response. The C-terminal domain (CTD) of MORC2, frequently phosphorylated in DNA damage, promotes cancer progression, but its role in chromatin remodelling remains unclear. Here, we report a molecular characterisation of full-length, phosphorylated MORC2, demonstrating its preference for binding open chromatin and functioning as a DNA sliding clamp. We identified a phosphate interacting motif within the CTD that dictates ATP hydrolysis rate and cooperative DNA binding. The DNA binding impacts several structural domains within the ATPase region. We provide the first visual proof that MORC2 induces chromatin remodelling through ATP hydrolysis-dependent DNA compaction, regulated by its phosphorylation state. These findings highlight phosphorylation of MORC2 CTD as a key modulator of chromatin remodelling, presenting it as a potential therapeutic target.

Oncogenic MORC2 in cancer development and beyond

Microrchidia CW-type zinc finger 2 (MORC2) is a member of the MORC superfamily of nuclear proteins. Growing evidence has shown that MORC2 not only participates in gene transcription and chromatin remodeling but also plays a key in human disease and tumor development by regulating the expression of downstream oncogenes or tumor suppressors. The present review provides an updated overview of MORC2 in the aspect of cancer hallmark and therapeutic resistance and summarizes its upstream regulators and downstream target genes. This systematic review may provide a favorable theoretical basis for emerging players of MORC2 in tumor development and new insight into the potential clinical application of basic science discoveries in the future.

Novel Insights into the Role of Chromatin Remodeler MORC2 in Cancer

A newly discovered chromatin remodeler, MORC2, is a Microrchidia (MORC) family member. MORC2 acts as a chromatin remodeler by binding to the DNA and changing chromatin conformation using its ATPase domain. MORC2 is highly expressed in a variety of human cancers. It controls diverse signaling pathways essential for cancer development through its target genes and interacting partners. MORC2 promotes cancer cells' growth, invasion, and migration by regulating the expression of genes involved in these processes. MORC2 is localized primarily in the nucleus and is also found in the cytoplasm. In the cytoplasm, MORC2 interacts with adenosine triphosphate (ATP)-citrate lyase (ACLY) to promote lipogenesis and cholesterogenesis in cancer. In the nucleus, MORC2 interacts with the transcription factor c-Myc to control the transcription of genes involved in glucose metabolism to drive cancer cell migration and invasion. Furthermore, MORC2 recruits on to the promoters of tumor suppressor genes to repress their transcription and expression to promote oncogenesis. In addition to its crucial function in oncogenesis, it plays a vital role in DNA repair. Overall, this review concisely summarizes the current knowledge about MORC2-regulated molecular pathways involved in cancer.

High Expression of MORC2 is Associated with Poor Clinical Outcomes and Immune Infiltrates in Colon Adenocarcinoma

Purpose

Microrchidia 2 (MORC2) is a universally expressed molecule that has recently been identified as a chromatin modulator and elevated in many malignancies. However, its prognostic value and immunological role of MORC2 in colon adenocarcinoma (COAD) have never been illustrated.

Methods

The clinical parameters and MORC2 expression datasets of COAD patients were obtained from The Cancer Genome Atlas (TCGA). Cancer and adjacent tissue specimens from surgically resected COAD patients were collected, and quantitative real-time PCR was used to detect MORC2 expression. Differentially expressed genes related to MORC2 were discovered and used for functional enrichment analysis. The diagnostic and prognostic values of MORC2 in COAD were conducted using receiver operating characteristics (ROC), Kaplan-Meier survival curve analysis, PrognoScan, Gene Expression Profiling Interactive Analysis (GEPIA) public databases and nomograms. Eventually, the association of MORC2 with tumor microenvironment was analyzed by using TIMER and GSVA package of R (v3.6.3).

Results

MORC2 expression was upregulated in COAD tissues, and the RT-qPCR results further verified the reliability of our differential analysis at the transcriptional level. Additionally, higher expression of MORC2 was correlated to a poor prognosis for COAD patients. MORC2 was an independent prognostic factor for COAD and could be a diagnostic factor for early COAD. Furthermore, MORC2 expression was positively correlated with immune cells such as NK cells, TFH cells and so on.

Conclusion

The findings demonstrated that overexpression of MORC2 was correlated with worse prognosis and immune infiltrates of COAD. MORC2 can serve as a reliable diagnostic and prognostic biomarker and a target of immunotherapy for COAD patients.

Endocytosis in cancer and cancer therapy

Endocytosis is a complex process whereby cell surface proteins, lipids and fluid from the extracellular environment are packaged, sorted and internalized into cells. Endocytosis is also a mechanism of drug internalization into cells. There are multiple routes of endocytosis that determine the fate of molecules, from degradation in the lysosomes to recycling back to the plasma membrane. The overall rates of endocytosis and temporal regulation of molecules transiting through endocytic pathways are also intricately linked with signalling outcomes. This process relies on an array of factors, such as intrinsic amino acid motifs and post-translational modifications. Endocytosis is frequently disrupted in cancer. These disruptions lead to inappropriate retention of receptor tyrosine kinases on the tumour cell membrane, changes in the recycling of oncogenic molecules, defective signalling feedback loops and loss of cell polarity. In the past decade, endocytosis has emerged as a pivotal regulator of nutrient scavenging, response to and regulation of immune surveillance and tumour immune evasion, tumour metastasis and therapeutic drug delivery. This Review summarizes and integrates these advances into the understanding of endocytosis in cancer. The potential to regulate these pathways in the clinic to improve cancer therapy is also discussed.

p21-Activated Kinase: Role in Gastrointestinal Cancer and Beyond

Simple Summary

Gastrointestinal tumors are the most common tumors with a high mortality rate worldwide. Numerous protein kinases have been studied in anticipation of finding viable tumor therapeutic targets, including PAK. PAK is a serine/threonine kinase that plays an important role in the malignant phenotype of tumors. The function of PAK in tumors is highlighted in cell proliferation, survival, motility, tumor cell plasticity and the tumor microenvironment, therefore providing a new possible target for clinical tumor therapy. Based on the current research works of PAK, we summarize and analyze the PAK features and signaling pathways in cells, especially the role of PAK in gastrointestinal tumors, thereby hoping to provide a theoretical basis for both the future studies of PAK and potential tumor therapeutic targets.

Abstract

Gastrointestinal tumors are the most common tumors, and they are leading cause of cancer deaths worldwide, but their mechanisms are still unclear, which need to be clarified to discover therapeutic targets. p21-activating kinase (PAK), a serine/threonine kinase that is downstream of Rho GTPase, plays an important role in cellular signaling networks. According to the structural characteristics and activation mechanisms of them, PAKs are divided into two groups, both of which are involved in the biological processes that are critical to cells, including proliferation, migration, survival, transformation and metabolism. The biological functions of PAKs depend on a large number of interacting proteins and the signaling pathways they participate in. The role of PAKs in tumors is manifested in their abnormality and the consequential changes in the signaling pathways. Once they are overexpressed or overactivated, PAKs lead to tumorigenesis or a malignant phenotype, especially in tumor invasion and metastasis. Recently, the involvement of PAKs in cellular plasticity, stemness and the tumor microenvironment have attracted attention. Here, we summarize the biological characteristics and key signaling pathways of PAKs, and further analyze their mechanisms in gastrointestinal tumors and others, which will reveal new therapeutic targets and a theoretical basis for the clinical treatment of gastrointestinal cancer.

MORC2/β-catenin signaling axis promotes proliferation and migration of breast cancer cells

Although Microrchidia 2 (MORC2) is overexpressed in many types of human cancer, its role in breast cancer progression remains unknown. Here, we report that the chromatin remodeler MORC2 expression positively correlates with β-catenin expression in breast cancer cell lines and patients. Overexpression of MORC2 augmented the expression of β-catenin and its target genes, cyclin D1 and c-Myc. Consistent with these results, we found MORC2 knockdown resulted in decreased expression of β-catenin and its target genes. Surprisingly, we observed that c-Myc, the target gene of β-catenin, regulated the MORC2-β-catenin signaling axis through a feedback mechanism. We demonstrated that MORC2 regulates β-catenin expression and function by modulating the phosphorylation of AKT. In addition, we observed reduced proliferation and migration of MORC2 overexpressing breast cancer cells upon β-catenin inhibition. Overall, our results demonstrate that MORC2 promotes breast cancer cell proliferation and migration by regulating β-catenin signaling.

Structural and Functional Attributes of Microrchidia Family of Chromatin Remodelers

Chromatin remodelers affect the spatio-temporal dynamics of global gene-expression by structurally modulating and/or reorganizing the chromatin. Microrchidia (MORC) family is a relatively new addition to the four well studied families of chromatin remodeling proteins. In this review, we discuss the current understanding of the structural aspects of human MORCs as well as their epigenetic functions. From a molecular and systems-level perspective, we explore their participation in phase-separated structures, possible influence on various biological processes through protein-protein interactions, and potential extra-nuclear roles. We describe how dysregulation/dysfunction of MORCs can lead to various pathological conditions. We conclude by emphasizing the importance of undertaking integrated efforts to obtain a holistic understanding of the various biological roles of MORCs.

The role of cell division control protein 42 in tumor and non-tumor diseases: A systematic review

Rho-GTPases control a variety of cellular functions mainly by regulating microtubule and actin dynamics, affecting the cytoskeleton, and are important regulators of the structural plasticity of dendrites and spines. Members of the Rho-GTPase family include Ras-related C3 botulinum toxin substrate 1 (Rac1), RhoA (Ras homologous), and cell division control protein 42 (Cdc42). Cdc42 is involved in the regulation of a variety of tumor and non-tumor diseases through a cascade of multiple signaling pathways. Active Cdc42 can regulate intercellular adhesion, cytoskeleton formation, and cell cycle, thus affecting cell proliferation, transformation, and dynamic balance as well as migration and invasion of tumor cells by regulating the expression of effector proteins. Here we discuss the role of Cdc42 in promoting metastasis, invasion, epithelial-mesenchymal transformation and angiogenesis in malignant tumors. The significant role of Cdc42 in non-tumor diseases is also discussed. Since Cdc42 plays a central role in the development of various diseases, small molecule inhibitors targeting Cdc42 have important clinical significance in the prevention and treatment of these diseases.

MORC protein family-related signature within human disease and cancer

The microrchidia (MORC) family of proteins is a highly conserved nuclear protein superfamily, whose members contain common domain structures (GHKL-ATPase, CW-type zinc finger and coiled-coil domain) yet exhibit diverse biological functions. Despite the advancing research in previous decades, much of which focuses on their role as epigenetic regulators and in chromatin remodeling, relatively little is known about the role of MORCs in tumorigenesis and pathogenesis. MORCs were first identified as epigenetic regulators and chromatin remodelers in germ cell development. Currently, MORCs are regarded as disease genes that are involved in various human disorders and oncogenes in cancer progression and are expected to be the important biomarkers for diagnosis and treatment. A new paradigm of expanded MORC family function has raised questions regarding the regulation of MORCs and their biological role at the subcellular level. Here, we systematically review the progress of researching MORC members with respect to their domain architectures, diverse biological functions, and distribution characteristics and discuss the emerging roles of the aberrant expression or mutation of MORC family members in human disorders and cancer development. Furthermore, the illustration of related mechanisms of the MORC family has made MORCs promising targets for developing diagnostic tools and therapeutic treatments for human diseases, including cancers.

The role of MORC3 in silencing transposable elements in mouse embryonic stem cells

BACKGROUND

Microrchidia proteins (MORCs) are involved in epigenetic gene silencing in a variety of eukaryotic organisms. Deletion of MORCs result in several developmental abnormalities and their dysregulation has been implicated in developmental disease and multiple cancers. Specifically, mammalian MORC3 mutations are associated with immune system defects and human cancers such as bladder, uterine, stomach, lung, and diffuse large B cell lymphomas. While previous studies have shown that MORC3 binds to H3K4me3 in vitro and overlaps with H3K4me3 ChIP-seq peaks in mouse embryonic stem cells, the mechanism by which MORC3 regulates gene expression is unknown.

RESULTS

In this study, we identified that mutation in Morc3 results in a suppressor of variegation phenotype in a Modifiers of murine metastable epialleles Dominant (MommeD) screen. We also find that MORC3 functions as an epigenetic silencer of transposable elements (TEs) in mouse embryonic stem cells (mESCs). Loss of Morc3 results in upregulation of TEs, specifically those belonging to the LTR class of retrotransposons also referred to as endogenous retroviruses (ERVs). Using ChIP-seq we found that MORC3, in addition to its known localization at H3K4me3 sites, also binds to ERVs, suggesting a direct role in regulating their expression. Previous studies have shown that these ERVs are marked by the repressive histone mark H3K9me3 which plays a key role in their silencing. However, we found that levels of H3K9me3 showed only minor losses in Morc3 mutant mES cells. Instead, we found that loss of Morc3 resulted in increased chromatin accessibility at ERVs as measured by ATAC-seq.

CONCLUSIONS

Our results reveal MORC3 as a novel regulator of ERV silencing in mouse embryonic stem cells. The relatively minor changes of H3K9me3 in the Morc3 mutant suggests that MORC3 acts mainly downstream of, or in a parallel pathway with, the TRIM28/SETDB1 complex that deposits H3K9me3 at these loci. The increased chromatin accessibility of ERVs in the Morc3 mutant suggests that MORC3 may act at the level of chromatin compaction to effect TE silencing.

MORC2 Interactome: Its Involvement in Metabolism and Cancer

Microrchidia 2 (MORC2) is an emerging chromatin modifier with a role in chromatin remodeling and epigenetic regulation. MORC2 is found to be upregulated in most cancers, playing a significant role in tumorigenesis and tumor metastasis. Recent studies have demonstrated that MORC2 is a scaffolding protein, which interacts with the proteins involved in DNA repair, chromatin remodeling, lipogenesis, and glucose metabolism. In this review, we discuss the domain architecture and cellular and subcellular localization of MORC2. Further, we highlight MORC2-specific interacting partners involved in metabolic reprogramming and other pathological functions such as cancer progression and metastasis.

Regulation of Formation, Stemness and Therapeutic Resistance of Cancer Stem Cells

Over the past 20 years cancer stem cells (CSCs) have been proposed as key players in the tumorigenesis and progression, which are closely related to the initiation, metastasis and therapeutic resistance of cancer. Evidences have been provided that both genetic and epigenetic factors contribute to the regulation of the formation and stemness maintenance as well as the therapeutic resistance of CSCs via affecting various signal pathways. In addition, the interaction between CSCs and tumor microenvironment has also been revealed to be involved in the above-described processes. With the aim of targeting CSCs to improve treatment outcome, we herein discuss the mechanisms that orchestrate the characteristic of CSCs by the three elements and potential therapeutic strategies. We also summarize how several key regulatory factors function in the regulation of not only the formation and stemness maintenance, but also the therapeutic resistance of CSCs. Thus, future studies focusing on these key factors would be helpful for the development of novel drugs targeting CSCs.

DOCK7 protects against replication stress by promoting RPA stability on chromatin

RPA is a critical factor for DNA replication and replication stress response. Surprisingly, we found that chromatin RPA stability is tightly regulated. We report that the GDP/GTP exchange factor DOCK7 acts as a critical replication stress regulator to promote RPA stability on chromatin. DOCK7 is phosphorylated by ATR and then recruited by MDC1 to the chromatin and replication fork during replication stress. DOCK7-mediated Rac1/Cdc42 activation leads to the activation of PAK1, which subsequently phosphorylates RPA1 at S135 and T180 to stabilize chromatin-loaded RPA1 and ensure proper replication stress response. Moreover, DOCK7 is overexpressed in ovarian cancer and depleting DOCK7 sensitizes cancer cells to camptothecin. Taken together, our results highlight a novel role for DOCK7 in regulation of the replication stress response and highlight potential therapeutic targets to overcome chemoresistance in cancer.

The chromatin modifier MORC2 affects glucose metabolism by regulating the expression of lactate dehydrogenase A through a feed forward loop with c-Myc

Microrchidia family CW-type zinc finger 2 (MORC2) is a recently identified chromatin modifier with an emerging role in cancer metastasis. However, its role in glucose metabolism, a hallmark of malignancy, remains to be explored. We found that MORC2 is a glucose-inducible gene and a target of c-Myc. Our meta-analysis revealed that MORC2 expression is positively correlated with the expression of enzymes involved in glucose metabolism in breast cancer patients. Furthermore, overexpression of MORC2 in MCF-7 and BT-549 cells augmented the expression and activity of a key glucose metabolism enzyme, lactate dehydrogenase A (LDHA). Conversely, selective knockdown of MORC2 by siRNA markedly decreased LDHA expression and activity and in turn reduced cancer cell migration. Collectively, these findings provide evidence that MORC2, a glucose-inducible gene, modulates the migration of breast cancer cells through the MORC2-c-Myc-LDHA axis.

P21-Activated Kinase 1: Emerging biological functions and potential therapeutic targets in Cancer

The p21-Activated kinase 1 (PAK1), a member of serine-threonine kinases family, was initially identified as an interactor of the Rho GTPases RAC1 and CDC42, which affect a wide range of processes associated with cell motility, survival, metabolism, cell cycle, proliferation, transformation, stress, inflammation, and gene expression. Recently, the PAK1 has emerged as a potential therapeutic target in cancer due to its role in many oncogenic signaling pathways. Many PAK1 inhibitors have been developed as potential preclinical agents for cancer therapy. Here, we provide an overview of essential roles that PAK1 plays in cancer, including its structure and autoactivation mechanism, its crucial function from onset to progression to metastasis, metabolism, immune escape and even drug resistance in cancer; endogenous regulators; and cancer-related pathways. We also summarize the reported PAK1 small-molecule inhibitors based on their structure types and their potential application in cancer. In addition, we provide overviews on current progress and future challenges of PAK1 in cancer, hoping to provide new ideas for the diagnosis and treatment of cancer.

Bioinformatic analysis of the potential molecular mechanism of PAK7 expression in glioblastoma

The present study aimed to determine the potential molecular mechanisms underlying p21 (RAC1)-activated kinase 7 (PAK7) expression in glioblastoma (GBM) and evaluate candidate prognosis biomarkers for GBM. Gene expression data from patients with GBM, including 144 tumor samples and 5 normal brain samples, were downloaded. Long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) were explored via re-annotation. The differentially expressed genes (DEGs), including differentially expressed mRNAs and differentially expressed lncRNAs, were investigated and subjected to pathway analysis via gene set enrichment analysis. The miRNA-lncRNA-mRNA interaction [competing endogenous RNA (ceRNA)] network was investigated and survival analysis, including of overall survival (OS), was performed on lncRNAs/mRNAs to reveal prognostic markers for GBM. A total of 954 upregulated and 1,234 downregulated DEGs were investigated between GBM samples and control samples. These DEGs, including PAK7, were mainly enriched in pathways such as axon guidance. ceRNA network analysis revealed several outstanding ceRNA relationships, including miR-185-5p-LINC00599-PAK7. Moreover, paraneoplastic antigen Ma family member 5 (PNMA5) and somatostatin receptor 1 (SSTR1) were the two outstanding prognostic genes associated with OS. PAK7 may participate in the tumorigenesis of GBM by regulating axon guidance, and miR-185-5p may play an important role in GBM progression by sponging LINC00599 to prevent interactions with PAK7. PNMA5 and SSTR1 may serve as novel prognostic markers for GBM.

PAK1 silencing is synthetic lethal with CDK4/6 inhibition in gastric cancer cells via regulating PDK1 expression

Gastric cancer (GC) is one of the most common malignancies worldwide. The prognosis of GC is unsatisfied owning to widespread metastasis. P21-activated kinase 1 (PAK1), a member of serine/threonine kinases, is associated with the progression of multiple types of human cancers. Here, we demonstrated that CDK4/6 inhibitor reduced GC cell viability and decreased PAK1 expression. Consistently, PAK1 ablation increased GC cell sensitivity exposed to CDK4/6 inhibitor and promoted DNA damage. We also revealed PAK1 depletion notably affected PDK1-AKT pathway, and PDK1 overexpression totally abrogated the effect of PAK1 deletion on DNA damage in GC cells. Additionally, PDK1 overexpression also rescued the increased GC cell sensitivity towards CDK4/6 inhibitor and the cell cycle arrest caused by PAK1 depletion. Our findings, therefore, suggested that PAK1 silencing increased sensitivity to CDK4/6 inhibition in gastric cancer cells via PDK1-AKT pathway. We, therefore, thought PAK1 as a promising therapeutic target for the treatment of CDK4/6 inhibitor-resistant gastric cancer.

Autoimmune Hepatitis and Stellate Cells: An Insight into the Role of Autophagy

Autoimmune hepatitis is a necroinflammatory process of liver, featuring interface hepatitis by T cells, macrophages and plasma cells that invade to periportal parenchyma. In this process, a variety of cytokines are secreted and liver tissues undergo fibrogenesis, resulting in the apoptosis of hepatocytes. Autophagy is a complementary mechanism for restraining intracellular pathogens to which the innate immune system does not provide efficient endocytosis. Hepatocytes with their particular regenerative features are normally in a quiescent state, and, autophagy controls the accumulation of excess products, therefore the liver serves as a basic model for the study of autophagy. Impairment of autophagy in the liver causes the accumulation of damaged organelles, misfolded proteins and exceeded lipids in hepatocytes as seen in metabolic diseases. In this review, we introduce autoimmune hepatitis in association with autophagy signaling. We also discuss some genes and proteins of autophagy, their regulatory roles in the activation of hepatic stellate cells and the importance of lipophagy and tyrosine kinase in hepatic fibrogenesis. In order to provide a comprehensive overview of the regulatory role of autophagy in autoimmune hepatitis, the pathway analysis of autophagy in autoimmune hepatitis is also included in this article.

Dimerization of MORC2 through its C-terminal coiled-coil domain enhances chromatin dynamics and promotes DNA repair

Decondesation of the highly compacted chromatin architecture is essential for efficient DNA repair, but how this is achieved remains largely unknown. Here, we report that microrchidia family CW-type zinc finger protein 2 (MORC2), a newly identified ATPase-dependent chromatin remodeling enzyme, is required for nucleosome destabilization after DNA damage through loosening the histone-DNA interaction. Depletion of MORC2 attenuates phosphorylated histone H2AX (γH2AX) focal formation, compromises the recruitment of DNA repair proteins, BRCA1, 53BP1, and Rad51, to sites of DNA damage, and consequently reduces cell survival following treatment with DNA-damaging chemotherapeutic drug camptothecin (CPT). Furthermore, we demonstrate that MORC2 can form a homodimer through its C-terminal coiled-coil (CC) domain, a process that is enhanced in response to CPT-induced DNA damage. Deletion of the C-terminal CC domain in MORC2 disrupts its homodimer formation and impairs its ability to destabilize histone-DNA interaction after DNA damage. Consistently, expression of dimerization-defective MORC2 mutant results in impaired the recruitment of DNA repair proteins to damaged chromatin and decreased cell survival after CPT treatment. Together, these findings uncover a new mechanism for MORC2 in modulating chromatin dynamics and DDR signaling through its c-terminal dimerization.

MORC2 regulates C/EBPα-mediated cell differentiation via sumoylation

The expression and activity of CCAAT/enhancer-binding protein α (C/EBPα) are involved in sumoylation modification, which is critical to divert normal cells from differentiation to proliferation. However, the role and underlying mechanism of C/EBPα in cancer is poorly understood. Human MORC2 (microrchidia family CW-type zinc-finger 2), is a member of the MORC proteins family containing a CW-type zinc-finger domain. Here, we found that MORC2 interacted with TE-III domain of C/EBPα, and the overexpression of MORC2 promoted wild-type C/EBPα sumoylation and its subsequent degradation, which didn’t significantly observe in mutant C/EBPα-K161R. Furthermore, the overexpression of MORC2 inhibited C/EBPα-mediated C2C12 cell differentiation to maintain cell cycle progression. Moreover, the striking correlation between the decreased C/EBPα expression and the increased MORC2 expression was also observed in the poor differentiation status of gastric cancer tissues. Most notably, the high expression of MORC2 is correlated  with an aggressive phenotype of clinical gastric cancer and shorter overall survival of patients. Taken together, our findings demonstrated that MORC2 expression regulated C/EBPα-mediated the axis of differentiation/proliferation via sumoylation modification, and affected its protein stability, causing cell proliferation and tumorigenesis.

MORC2 promotes development of an aggressive colorectal cancer phenotype through inhibition of NDRG1

MORC2 (microrchidia family CW‐type zinc finger 2) is a newly identified chromatin remodeling protein that functions in diverse biological processes including gene transcription. NDRG1 is a metastasis suppressor and a prognostic biomarker for colorectal cancer (CRC). However, the relationship between MORC2 and NDRG1 transcriptional regulation and the roles of MORC2 in CRC remain elusive. Here, we showed that MORC2 downregulated NDRG1 mRNA, protein levels, and promoter activity in CRC cells. We also found that MORC2 bound to the −446 to −213 bp region of the NDRG1 promoter. Mechanistically, histone deacetylase sirtuin 1 (SIRT1) was involved in NDRG1 transcriptional regulation. MORC2 was able to interact with SIRT1 and inhibit NDRG1 promoter activity cumulatively with SIRT1. MORC2 overexpression led to a decrease of H3Ac and H4Ac of the NDRG1 promoter. Importantly, we showed that NDRG1 was essential in MORC2‐mediated promotion of CRC cell migration and invasion in vitro, as well as lung metastasis of CRC cells in vivo. Moreover, MORC2 expression correlated negatively with NDRG1 expression in CRC patients. High expression of MORC2 was significantly associated with lymph node metastasis (P = 0.019) and poor pTNM stage (P = 0.02) and the expression of MORC2 correlated with poor prognosis in colon cancer patients. Our findings thus contribute to the knowledge of the regulatory mechanism of MORC2 in downregulating NDRG1, and suggest MORC2 as a potential therapeutic target for CRC.

Cancer-Associated MORC2-Mutant M276I Regulates an hnRNPM-Mediated CD44 Splicing Switch to Promote Invasion and Metastasis in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most lethal subtype of breast cancer, with a high propensity for distant metastasis and limited treatment options, yet its molecular underpinnings remain largely unknown. Microrchidia family CW-type zinc finger 2 (MORC2) is a newly identified chromatin remodeling protein whose mutations have been causally implicated in several neurologic disorders. Here, we report that a cancer-associated substitution of methionine to isoleucine at residue 276 (M276I) of MORC2 confers gain-of-function properties in the metastatic progression of TNBC. Expression of mutant MORC2 in TNBC cells increased cell migration, invasion, and lung metastasis without affecting cell proliferation and primary tumor growth compared with its wild-type counterpart. The M276I mutation enhanced binding of MORC2 to heterogeneous nuclear ribonucleoprotein M (hnRNPM), a component of the spliceosome machinery. This interaction promoted an hnRNPM-mediated splicing switch of CD44 from the epithelial isoform (CD44v) to the mesenchymal isoform (CD44s), ultimately driving epithelial-mesenchymal transition (EMT). Knockdown of hnRNPM reduced the binding of mutant MORC2 to CD44 pre-mRNA and reversed the mutant MORC2-induced CD44 splicing switch and EMT, consequently impairing the migratory, invasive, and lung metastatic potential of mutant MORC2-expressing cells. Collectively, these findings provide the first functional evidence for the M276I mutation in promoting TNBC progression. They also establish the first mechanistic connection between MORC2 and RNA splicing and highlight the importance of deciphering unique patient-derived mutations for optimizing clinical outcomes of this highly heterogeneous disease.Significance: A gain-of-function effect of a single mutation on MORC2 promotes metastasis of triple-negative breast cancer by regulating CD44 splicing. Cancer Res; 78(20); 5780-92. ©2018 AACR.

MORC2, a novel oncogene, is upregulated in liver cancer and contributes to proliferation, metastasis and chemoresistance

Microrchidia 2 (MORC2) is important in DNA damage repair and lipogenesis, however, the clinical and functional role of MORC2 in liver cancer remains to be fully elucidated. The aim the present study was to clarify the role of MORC2 in liver cancer. Expression profile analysis, immunohistochemical staining, reverse transcription-quantitative polymerase chain reaction analysis and western blot analysis were performed to evaluate the levels of MORC2 in liver cancer patient specimens and cell lines; subsequently the expression of MORC2 was suppressed or increased in liver cancer cells and the effects of MORC2 on the cancerous transformation of liver cancer cells were examined in vitro and in vivo. MORC2 was upregulated in liver cancer tissues, and the upregulation was associated with certain clinicopathologic features of patients with liver cancer. MORC2 knockdown caused marked inhibition of liver cancer cell proliferation and clonogenicity, whereas the overexpression of MORC2 substantially promoted liver cancer cell proliferation. In addition, the knockdown of MORC2 inhibited the migratory and invasive ability of liver cancer cells, whereas increased migration and invasion rates were observed in cells with ectopic expression of MORC2. In a model of nude mice, the overexpression of MORC2 promoted tumorigenicity and markedly enhanced pulmonary metastasis of liver cancer. Furthermore, MORC2 regulated apoptosis and its expression level had an effect on the sensitivity of liver cancer cells to doxorubicin, 5-fluorouracil and cisplatin. Mechanically, MORC2 modulated the mitochondrial apoptotic pathway, possibly in a p53-dependent manner, and its dysregulation also resulted in the abnormal activation of the Hippo pathway. For the first time, to the best of our knowledge, the present study confirmed that MORC2 was a novel oncogene in liver cancer. These results provide useful insight into the mechanism underlying the tumorigenesis and progression of liver cancer, and offers clues into potential novel liver cancer therapies.

Aberrant high expression level of MORC2 is a common character in multiple cancers

Microrchidia 2 (MORC2) plays important roles in DNA damage repair and lipogenesis, but the clinical and functional role of MORC2 in cancer remains largely unexplored. In this study, we showed that MORC2 was widely expressed in human tissues while significantly up-regulated in most cancer types using immunohistochemical staining and analysis of messenger RNA expression profile of more than 2000 human tissue samples from 15 different organs (lung, prostate, liver, breast, brain, stomach, colon/rectum, pancreas, ovary, endometrium, skin, nasopharynx, kidney, esophagus, and bladder). We also found that the MORC2 expression level in high-grade cancer tissues was much more elevated and associated with unfavorable pathological characteristics, poor overall survival, and disease-free survival in several kinds of cancers such as non-small cell lung cancer and breast cancer. Gene set enrichment analysis was used to predict the genes modulated by MORC2, and the results showed that dysregulation of MORC2 in tumor may take part in the cell cycle regulation and genomic instability. We observed that MORC2 knockdown would arrest the cell cycle progress, and the genome of tumors with high MORC2 expression contained more point mutations and gene copy number variation, which validates our gene set enrichment analysis results. The results also showed that MORC2 knockdown would significantly inhibit the proliferation, colony forming, migration, and invasion in multiple cancer cell lines. Taken together, these results highlight the importance of MORC2 in tumorigenesis and cancer progression, and it may act as a potential diagnostic marker and therapeutic target for these diseases.

Regulating Cdc42 and Its Signaling Pathways in Cancer: Small Molecules and MicroRNA as New Treatment Candidates

Despite great improvements in the diagnosis and treatment of neoplasms, metastatic disease is still the leading cause of death in cancer patients, with mortality rates still rising. Given this background, new ways to treat cancer will be important for development of improved cancer control strategies. Cdc42 is a member of the Rho GTPase family and plays an important role in cell-to-cell adhesion, formation of cytoskeletal structures, and cell cycle regulation. It thus influences cellular proliferation, transformation, and homeostasis, as well as the cellular migration and invasion processes underlying tumor formation. Cdc42 acts as a collection point for signal transduction and regulates multiple signaling pathways. Moreover, recent studies show that in most human cancers Cdc42 is abnormally expressed and promoting neoplastic growth and metastasis. Regarding possible new treatments for cancer, miRNA and small molecules targeting Cdc42 and related pathways have been recently found to be effective on cancer. In this review, we analyze the newly recognized regulation mechanisms for Cdc42 and Cdc42-related signal pathways, and particularly new treatments using small molecules and miRNAs to inhibit the abnormal overexpression of Cdc42 that may slow down the metastasis process, improve cancer therapy and lead to novel strategies for development of antineoplastic drugs.

p21 Activated kinase 1: Nuclear activity and its role during DNA damage repair

p21-activated kinase 1 (PAK1) is a serine/threonine kinase activated by the small GTPases Rac1 and Cdc42. It is located in the chromosome 11q13 and is amplified and/or overexpressed in several human cancer types including 25-30% of breast tumors. This enzyme plays a pivotal role in the control of a number of fundamental cellular processes by phosphorylating its downstream substrates. In addition to its role in the cytoplasm, it is well documented that PAK1 also plays crucial roles in the nucleus participating in mitotic events and gene expression through its association and/or phosphorylation of several transcription factors, transcriptional co-regulators and cell cycle-related proteins, including Aurora kinase A (AURKA), polo-like kinase 1 (PLK1), the forkhead transcription factor (FKHR), estrogen receptor α (ERα), and Snail. More recently, PAK signaling has emerged as a component of the DNA damage response (DDR) as PAK1 activity influences the cellular sensitivity to ionizing radiation and promotes the expression of several genes involved in the Fanconi Anemia/BRCA pathway. This review will focus on the nuclear functions of PAK1 and its role in the regulation of DNA damage repair.

MORC2B is essential for meiotic progression and fertility

The microrchidia (MORC) family proteins are chromatin-remodelling factors and function in diverse biological processes such as DNA damage response and transposon silencing. Here, we report that mouse Morc2b encodes a functional germ cell-specific member of the MORC protein family. Morc2b arose specifically in the rodent lineage through retrotransposition of Morc2a during evolution. Inactivation of Morc2b leads to meiotic arrest and sterility in both sexes. Morc2b-deficient spermatocytes and oocytes exhibit failures in chromosomal synapsis, blockades in meiotic recombination, and increased apoptosis. Loss of MORC2B causes mis-regulated expression of meiosis-specific genes. Furthermore, we find that MORC2B interacts with MORC2A, its sequence paralogue. Our results demonstrate that Morc2b, a relatively recent gene, has evolved an essential role in meiosis and fertility.

In sexually reproducing organisms, meiosis, a process unique to germ cells, produces haploid gametes. Abnormalities in meiosis can lead to infertility, loss of pregnancy, or genetic diseases such as Down syndrome. The meiotic processes are tightly regulated by a large number of genes including many meiosis-specific ones. The majority of meiosis-specific factors are conserved, however, species-specific factors have evolved. Here we report functional studies of a rodent lineage–specific gene named Morc2b. Morc2b belongs to a family of chromatin-remodelling factors. Morc2b is specifically expressed in germ cells. Disruption of Morc2b causes meiotic arrest and infertility in both sexes. Notably, MORC2B regulates the expression of a number of meiosis-specific genes. Interestingly, MORC2B interacts with its sequence homologue MORC2A. These functional studies have uncovered a new protein complex in the regulation of key meiotic processes and suggested the presence of continued selection pressure for evolution of new meiosis-specific factors.

Aquaporin 3 promotes the stem-like properties of gastric cancer cells via Wnt/GSK-3β/β-catenin pathway

Cancer stem cells (CSCs) are believed to contribute to the tumor growth in gastric carcinoma (GC), a common lethal malignancy. This study investigated the effect of aquaporin 3 (AQP3) on stem-like properties of human GC cells. Elevated AQP3 expression was associated with CD44 expression in human GC specimens. Expression of AQP3 and that of CD44 positively correlated with Lauren classification, lymph node metastasis, and lymphovascular invasion. Altering the AQP3 expression had pronounced effects on the tumorigenic potential and self-renewal capacity of the gastric cancer cell lines SGC7901, MGC803, and AGS, both in vitro and in vivo. Overexpression of AQP3 induced CD44 expression and activation of the β-catenin signaling pathway, whereas silencing AQP3 expression using short hairpin RNA had the opposite effect. Furthermore, pharmacological inhibition of GSK-3β using LiCl impaired the effect of AQP3 knockdown in CSCs, whereas the inhibition of the Wnt/β-catenin pathway by XAV939 blocked the effect of AQP3 overexpression. These results demonstrate that AQP3 promotes stem-like properties of human GC cells by activating the Wnt/GSK-3β/β-catenin signaling pathway.

Chromatin remodeling protein MORC2 promotes breast cancer invasion and metastasis through a PRD domain-mediated interaction with CTNND1

MORC family CW-type zinc finger 2 (MORC2) is a newly identified chromatin remodeling protein with emerging roles in the regulation of DNA damage response and gene transcription, but its mechanistic role in breast cancer development and progression remains unexplored. Here, we show that MORC2 promoted breast cancer invasion and metastasis and these effects depended on a proline-rich domain (PRD) within its carboxy-terminal region spanning residues 601–734. Induced expression of wild-type MORC2 did not significantly affect cell proliferation and cell-cycle progression, but promoted breast cancer cell migration and invasion in vitro and metastatic lung colonization in vivo. The PRD domain was dispensable for the protein stability and subcellular localization of MORC2, but depletion of the PRD domain substantially suppressed MORC2-mediated migration, invasion, and metastasis. Proteomic and biochemical analyses further demonstrated that wild-type MORC2, but not PRD deletion mutant, interacted with catenin delta 1 (CTNND1), a cadherin-associated protein that participates in tumor invasion and metastasis. Moreover, knockdown of endogenous CTNND1 by short hairpin RNAs suppressed the migratory and invasive potential of MORC2-expressing cells. Taken together, these results suggest that MORC2 promotes breast cancer invasion and metastasis through its PRD domain-mediated interaction with CTNND1.

MORC Proteins: Novel Players in Plant and Animal Health

Microrchidia (MORC) proteins comprise a family of proteins that have been identified in prokaryotes and eukaryotes. They are defined by two hallmark domains: a GHKL-type ATPase and an S5 fold. MORC proteins in plants were first discovered via a genetic screen for Arabidopsis mutants compromised for resistance to a viral pathogen. Subsequent studies expanded their role in plant immunity and revealed their involvement in gene silencing and transposable element repression. Emerging data suggest that MORC proteins also participate in pathogen-induced chromatin remodeling and epigenetic gene regulation. In addition, biochemical analyses recently demonstrated that plant MORCs have topoisomerase II (topo II)-like DNA modifying activities that may be important for their function. Interestingly, animal MORC proteins exhibit many parallels with their plant counterparts, as they have been implicated in disease development and gene silencing. In addition, human MORCs, like plant MORCs, bind salicylic acid and this inhibits some of their topo II-like activities. In this review, we will focus primarily on plant MORCs, although relevant comparisons with animal MORCs will be provided.

Growth hormone-releasing hormone receptor antagonists inhibit human gastric cancer through downregulation of PAK1-STAT3/NF-κB signaling

Gastric cancer (GC) ranks as the fourth most frequent in incidence and second in mortality among all cancers worldwide. The development of effective treatment approaches is an urgent requirement. Growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) have been found to be present in a variety of tumoral tissues and cell lines. Therefore the inhibition of GHRH-R was proposed as a promising approach for the treatment of these cancers. However, little is known about GHRH-R and the relevant therapy in human GC. By survival analyses of multiple cohorts of GC patients, we identified that increased GHRH-R in tumor specimens correlates with poor survival and is an independent predictor of patient prognosis. We next showed that MIA-602, a highly potent GHRH-R antagonist, effectively inhibited GC growth in cultured cells. Further, this inhibitory effect was verified in multiple models of human GC cell lines xenografted into nude mice. Mechanistically, GHRH-R antagonists target GHRH-R and down-regulate the p21-activated kinase 1 (PAK1)-mediated signal transducer and activator of transcription 3 (STAT3)/nuclear factor-κB (NF-κB) inflammatory pathway. Overall, our studies establish GHRH-R as a potential molecular target in human GC and suggest treatment with GHRH-R antagonist as a promising therapeutic intervention for this cancer.

The Emerging Role of MORC Family Proteins in Cancer Development and Bone Homeostasis

Microrchidia (MORC or MORC family CW-type zinc finger protein), a highly conserved nuclear protein superfamily, is an interesting new player in signaling-dependent chromatin remodeling and epigenetic regulation. MORC family proteins consist of MORC1, MORC2, MORC3, and MORC4 which display common structural determinants such as CW-type zinc finger and coiled-coil domains. They also exhibit unique structural motifs and tissue-specific expression profiles. MORC1 was first discovered as a key regulator for male meiosis and spermatogenesis. Accumulating biochemical and functional analyses unveil MORC proteins as key regulators for cancer development. More recently, using an ENU mutagenesis mouse model, MORC3 was found to play a role in regulating bone and calcium homeostasis. Here we discuss recent research progress on the emerging role of MORC proteins in cancer development and bone metabolism. Unravelling the cellular and molecular mechanisms by which MORC proteins carry out their functions in a tissue specific manner are important subjects for future investigation. J. Cell. Physiol. 232: 928-934, 2017. © 2016 Wiley Periodicals, Inc.

PAKs in Human Cancer Progression: From Inception to Cancer Therapeutic to Future Oncobiology

Since the initial recognition of a mechanistic role of p21-activated kinase 1 (PAK1) in breast cancer invasion, PAK1 has emerged as one of the widely overexpressed or hyperactivated kinases in human cancer at-large, allowing the PAK family to make in-roads in cancer biology, tumorigenesis, and cancer therapeutics. Much of our current understanding of the PAK family in cancer progression relates to a central role of the PAK family in the integration of cancer-promoting signals from cell membrane receptors as well as function as a key nexus-modifier of complex, cytoplasmic signaling network. Another core aspect of PAK signaling that highlights its importance in cancer progression is through PAK's central role in the cross talk with signaling and interacting proteins, as well as PAK's position as a key player in the phosphorylation of effector substrates to engage downstream components that ultimately leads to the development cancerous phenotypes. Here we provide a comprehensive review of the recent advances in PAK cancer research and its downstream substrates in the context of invasion, nuclear signaling and localization, gene expression, and DNA damage response. We discuss how a deeper understanding of PAK1's pathobiology over the years has widened research interest to the PAK family and human cancer, and positioning the PAK family as a promising cancer therapeutic target either alone or in combination with other therapies. With many landmark findings and leaps in the progress of PAK cancer research since the infancy of this field nearly 20 years ago, we also discuss postulated advances in the coming decade as the PAK family continues to shape the future of oncobiology.

Mutations in the MORC2 gene cause axonal Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) is a complex disorder with wide genetic heterogeneity. Here we present a new axonal Charcot-Marie-Tooth disease form, associated with the gene microrchidia family CW-type zinc finger 2 (MORC2). Whole-exome sequencing in a family with autosomal dominant segregation identified the novel MORC2 p.R190W change in four patients. Further mutational screening in our axonal Charcot-Marie-Tooth disease clinical series detected two additional sporadic cases, one patient who also carried the same MORC2 p.R190W mutation and another patient that harboured a MORC2 p.S25L mutation. Genetic and in silico studies strongly supported the pathogenicity of these sequence variants. The phenotype was variable and included patients with congenital or infantile onset, as well as others whose symptoms started in the second decade. The patients with early onset developed a spinal muscular atrophy-like picture, whereas in the later onset cases, the initial symptoms were cramps, distal weakness and sensory impairment. Weakness and atrophy progressed in a random and asymmetric fashion and involved limb girdle muscles, leading to a severe incapacity in adulthood. Sensory loss was always prominent and proportional to disease severity. Electrophysiological studies were consistent with an asymmetric axonal motor and sensory neuropathy, while fasciculations and myokymia were recorded rather frequently by needle electromyography. Sural nerve biopsy revealed pronounced multifocal depletion of myelinated fibres with some regenerative clusters and occasional small onion bulbs. Morc2 is expressed in both axons and Schwann cells of mouse peripheral nerve. Different roles in biological processes have been described for MORC2. As the silencing of Charcot-Marie-Tooth disease genes have been associated with DNA damage response, it is tempting to speculate that a deregulation of this pathway may be linked to the axonal degeneration observed in MORC2 neuropathy, thus adding a new pathogenic mechanism to the long list of causes of Charcot-Marie-Tooth disease.

Microchidia protein 2, MORC2, downregulates the cytoskeleton adapter protein, ArgBP2, via histone methylation in gastric cancer cells

ArgBP2 is an adapter protein that plays an important role in actin-dependent processes such as cell adhesion and migration. However, its function and regulation mechanisms in gastric cancer have not yet been investigated. Here, we showed the low expression of ArgBP2 mRNA level in gastric tumor samples and its repressive function in the proliferation, migration, and invasion of gastric cancer cells. Then, we cloned and identified ArgBP2 promoter and verified that MORC2 bound to the promoter. Moreover, we demonstrated that MORC2 enhanced the recruitment of EZH2, which promoted the tri-methylation of H3K27, leading to the transcriptional repression of ArgBP2. Our results might thus contribute to understanding the molecular mechanisms of ArgBP2 regulation and suggesting ArgBP2 as a potential therapeutic target for gastric cancer.