Microrchidia 2/histone deacetylase 1 complex regulates E-cadherin gene expression and function.

Although Microrchidia 2 (MORC2) is widely overexpressed in human malignancies and linked to cancer cell proliferation, metabolism, and metastasis, the mechanism of action of MORC2 in cancer cell migration and invasion is yet undeciphered. Here, we identified for the first time that MORC2, a chromatin remodeler, regulates E-cadherin expression and, subsequently regulates breast cancer cell migration and invasion. We observed a negative correlation between the expression levels of MORC2 and E-cadherin in breast cancer. Furthermore, the overexpression of MORC2 resulted in decreased expression levels of E-cadherin. In addition, co-immunoprecipitation and chromatin immunoprecipitation assays revealed that MORC2 interacts with HDAC1 and gets recruited onto the E-cadherin promoter to inhibit its transcription, thereby suppress its expression. Consequently, knockdown of HDAC1 in MORC2-overexpressing cells led to reduced cancer cell migration and invasion. Interestingly, we noticed that MORC2-regulated glucose metabolism via c-Myc, and LDHA, also modulates the expression of E-cadherin. Collectively, these results demonstrate for the first time a mechanistic role for MORC2 as an upstream regulator of E-cadherin expression and its associated functions in breast cancer.

Zinc transporter LIV1: A promising cell surface target for triple negative breast cancer.

Breast cancer is one of the leading causes contributing to the global cancer burden. The triple negative breast cancer (TNBC) molecular subtype accounts for the most aggressive type. Despite progression in therapeutic options and prognosis in breast cancer treatment options, there remains a high rate of distant relapse. With advancements in understanding the role of zinc and zinc carriers in the prognosis and treatment of the disease, the scope of precision treatment/targeted therapy has been expanded. Zinc levels and zinc transporters play a vital role in maintaining cellular homeostasis, tumor surveillance, apoptosis, and immune function. This review focuses on the zinc transporter, LIV1, as an essential target for breast cancer prognosis and emerging treatment options. Previous studies give an insight into the role of LIV1 in fulfilling the most important hallmarks of cancer such as apoptosis, metastasis, invasion, and evading the immune system. Normal tissue expression of LIV1 is limited. Higher expression of LIV1 has been linked to Epithelial-Mesenchymal Transition, histological grade of cancer, and early node metastasis. LIV1 was found to be one of the attractive targets in the therapeutic hunt for TNBCs. TNBCs are an immunogenic breast cancer subtype. As zinc transporters are known to serve as the metabolic gatekeepers of immune cells, this review bridges tumor infiltrating lymphocytes, TNBC and LIV1. In addition, the suitability of LIV1 as an antibody-drug conjugate (Seattle genetics [SGN]-LIV1A) target in TNBC, represents a promising strategy for patients. Early clinical trial results reveal that this novel agent reduces tumor burden by inducing mitotic arrest, immunomodulation, and immunogenic cell death, warranting further investigation of SGN-LIV1A in combination with immuno-oncology agents. Priming the patient's immune response in combination with SGN-LIV1A could eventually change the landscape for the TNBC patient population.

MTA1 coregulator regulates LDHA expression and function in breast cancer.

Metastasis Associated Protein1 (MTA1) is a chromatin modifier and its expression is significantly associated with prognosis of many cancers. However, its role in glucose metabolism remains unexplored. Here, we report that MTA1 has a significant role in glucose metabolism where MTA1 regulates the LDHA expression and activity and subsequently its function in breast cancer motility. The results showed that MTA1 expression is positively correlated with the LDHA expression levels in breast cancer patients. Further, it was found that MTA1 is necessary for the optimal expression of LDHA. The underlying molecular mechanism involves the interaction of MTA1 with c-Myc and recruitment of MTA1-c-Myc complex on to the LDHA promoter to regulate its transcription. Consequently, the LDHA knock down using LDHA specific siRNA in MCF7 cells stably expressing MTA1 reduced the migration of MCF7 cells. Altogether these findings revealed the regulatory role for MTA1 in LDHA expression and its resulting biological function.

Multiple coregulatory control of tyrosine hydroxylase gene transcription.

Despite ubiquitous expression and a high level of metastasis-associated protein 1 (MTA1) coregulator, the physiological role of the MTA1 coactivator remains unknown. We found that MTA1 is a bona fide coactivator and stimulator of tyrosine hydroxylase (TH) transcription in neuronal cells and that MTA1-null mice had lower TH expression in the striatum and substantial nigra. MTA1 physically achieves these functions by interacting directly with DJ1 (Parkinson disease 7) and in turn recruits the DJ1/MTA1/RNA polymerase II complex to the bicoid binding element (BBE) in the TH promoter. Furthermore, we found that the MTA1/DJ1 complex is required for optimum stimulation of the TH expression by paired like homeodomain transcription factor (Pitx3) homeodomain transcription factor and that the MTA1/DJ1 complex is recruited to the TH gene chromatin via the direct interaction of MTA1 with Pitx3. These findings reveal a role for MTA1 as an upstream coactivator of TH and advance the notion of polygenic regulation of a disease-causing gene by coordinated interactions of three regulatory proteins.

Bidirectional autoregulatory mechanism of metastasis-associated protein 1-alternative reading frame pathway in oncogenesis.

Although metastasis-associated protein 1 (MTA1), a component of the nucleosome remodeling and histone deacetylation complex, is widely up-regulated in human cancers and correlates with tumor metastasis, its regulatory mechanism and related signaling pathways remain unknown. Here, we report a previously unrecognized bidirectional autoregulatory loop between MTA1 and tumor suppressor alternative reading frame (ARF). MTA1 transactivates ARF transcription by recruiting the transcription factor c-Jun onto the ARF promoter in a p53-independent manner. ARF, in turn, negatively regulates MTA1 expression independently of p53 and c-Myc. In this context, ARF interacts with transcription factor specificity protein 1 (SP1) and promotes its proteasomal degradation by enhancing its interaction with proteasome subunit regulatory particle ATPase 6, thereby abrogating the ability of SP1 to stimulate MTA1 transcription. ARF also physically associates with MTA1 and affects its protein stability. Thus, MTA1-mediated activation of ARF and ARF-mediated functional inhibition of MTA1 represent a p53-independent bidirectional autoregulatory mechanism in which these two opposites act in concert to regulate cell homeostasis and oncogenesis, depending on the cellular context and the environment.

Signaling-dependent phosphorylation of mitotic centromere-associated kinesin regulates microtubule depolymerization and its centrosomal localization.

BACKGROUND: Although PAK1 regulates cytoskeleton and microtubule dynamics, its role in controlling the functions of MCAK remains unknown. RESULTS: PAK1 phosphorylates MCAK and thereby regulates both its localization and function. CONCLUSION: MCAK is a cognate substrate of PAK1. SIGNIFICANCE: This study provides a novel mechanistic insight into PAK1 regulation of MCAK functions. Although p21-activated kinase 1 (PAK1) and microtubule (MT) dynamics regulate numerous fundamental processes including cytoskeleton remodeling, directional motility, and mitotic functions, the significance of PAK1 signaling in regulating the functions of MT-destabilizing protein mitotic centromere-associated kinesin (MCAK) remains unknown. Here we found that MCAK is a cognate substrate of PAK1 wherein PAK1 phosphorylates MCAK on serines 192 and 111 both in vivo and in vitro. Furthermore, we found that PAK1 phosphorylation of MCAK on serines 192 and 111 preferentially regulates its microtubule depolymerization activity and localization to centrosomes, respectively, in the mammalian cells.

Metastasis-associated protein 1/histone deacetylase 4-nucleosome remodeling and deacetylase complex regulates phosphatase and tensin homolog gene expression and function.

Metastasis-associated protein 1 (MTA1) is widely overexpressed in human cancers and is associated with malignant phenotypic changes contributing to morbidity in the associated diseases. Here we discovered for the first time that MTA1, a master chromatin modifier, transcriptionally represses the expression of phosphatase and tensin homolog (PTEN), a tumor suppressor gene, by recruiting class II histone deacetylase 4 (HDAC4) along with the transcription factor Yin-Yang 1 (YY1) onto the PTEN promoter. We also found evidence of an inverse correlation between the expression levels of MTA1 and PTEN in physiologically relevant breast cancer microarray datasets. We found that MTA1 up-regulation leads to a decreased expression of PTEN protein and stimulation of PI3K as well as phosphorylation of its signaling targets. Accordingly, selective down-regulation of MTA1 in breast cancer cells increases PTEN expression and inhibits stimulation of the PI3K/AKT signaling. Collectively, these findings provide a mechanistic role for MTA1 in transcriptional repression of PTEN, leading to modulation of the resulting signaling pathways.

Metastasis-associated protein 1 drives tumor cell migration and invasion through transcriptional repression of RING finger protein 144A.

Metastasis-associated protein 1 (MTA1), a component of the nucleosome-remodeling and histone deacetylase complex, is widely up-regulated in human cancers and significantly correlated with tumor invasion and metastasis, but the mechanisms involved remain largely unknown. Here, we report that MTA1 transcriptionally represses the expression of RING finger protein 144A (RNF144A), an uncharacterized gene whose protein product possesses potential E3 ubiquitin ligase activity, by recruiting the histone deacetylase 2 (HDAC2) and CCAAT/enhancer-binding protein α (c/EBPα) co-repressor complex onto human RNF144A promoter. Furthermore, an inverse correlation between the expression levels of MTA1 and RNF144A was demonstrated in publicly available breast cancer microarray datasets and the MCF10 breast cancer progression model system. To address functional aspects of MTA1 regulation of RNF144A, we demonstrate that RNF144A is a novel suppressor of cancer migration and invasion, two requisite steps of metastasis in vivo, and knockdown of endogenous RNF144A by small interfering RNAs accelerates the migration and invasion of MTA1-overexpressing cells. These results suggest that RNF144A is partially responsible for MTA1-mediated migration and invasion and that MTA1 overexpression in highly metastatic cancer cells drives cell migration and invasion by, at least in part, interfering with the suppressive function of RNF144A through transcriptional repression of RNF144A expression. Together, these findings provide novel mechanistic insights into regulation of tumor progression and metastasis by MTA1 and highlight a previously unrecognized role of RNF144A in MTA1-driven cancer cell migration and invasion.

Mechanism of MTA1 protein overexpression-linked invasion: MTA1 regulation of hyaluronan-mediated motility receptor (HMMR) expression and function.

Even though the hyaluronan-mediated motility receptor (HMMR), a cell surface oncogenic protein, is widely up-regulated in human cancers and correlates well with cell motility and invasion, the underlying molecular and nature of its putative upstream regulation remain unknown. Here, we found for the first time that MTA1 (metastatic tumor antigen 1), a master chromatin modifier, regulates the expression of HMMR and, consequently, its function in breast cancer cell motility and invasiveness. We recognized a positive correlation between the levels of MTA1 and HMMR in human cancer. Furthermore, MTA1 is required for optimal expression of HMMR. The underlying mechanism includes interaction of the MTA1·RNA polymerase II·c-Jun coactivator complex with the HMMR promoter to stimulates its transcription. Accordingly, selective siRNA-mediated knockdown of HMMR in breast cancer cells substantially reduces the invasion and migration of cells. These findings reveal a regulatory role for MTA1 as an upstream coactivator of HMMR expression and resulting biological phenotypes.

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.

MORC2 and MAX contributes to the expression of glycolytic enzymes, breast cancer cell proliferation and migration.

Cancer cell proliferation is a high energy demanding process, where the cancer cells acquire energy by high rates of glycolysis, and this phenomenon is known as the "Warburg effect". Microrchidia 2 (MORC2), an emerging chromatin remodeler, is over expressed in several cancers including breast cancer and found to promote cancer cell proliferation. However, the role of MORC2 in glucose metabolism in cancer cells remains unexplored. In this study, we report that MORC2 interacts indirectly with the genes involved in glucose metabolism via transcription factors MAX (MYC-associated factor X) and MYC. We also found that MORC2 co-localizes and interacts with MAX. Further, we observed a positive correlation of expression of MORC2 with glycolytic enzymes Hexokinase 1 (HK1), Lactate dehydrogenase A (LDHA) and Phosphofructokinase platelet (PFKP) type in multiple cancers. Surprisingly, the knockdown of either MORC2 or MAX not only decreased the expression of glycolytic enzymes but also inhibited breast cancer cell proliferation and migration. Together, these results demonstrate the involvement of the MORC2/MAX signaling axis in the expression of glycolytic enzymes and breast cancer cell proliferation and migration.

SUMOylation and SUMO-interacting motif (SIM) of metastasis tumor antigen 1 (MTA1) synergistically regulate its transcriptional repressor function.

Metastasis tumor antigen 1 (MTA1), a component of the Mi-2·nucleosome remodeling and deacetylase complex, plays a crucial role in gene transcription, but the mechanism involved remains largely unknown. Here, we report that MTA1 is a substrate for small ubiquitin-related modifier 2/3 (SUMO2/3) in vivo. Protein inhibitor of activated STAT (PIAS) proteins enhance SUMOylation of MTA1 and may participate in paralog-selective SUMOylation, whereas sentrin/SUMO-specific protease 1 (SENP1) and 2 may act as deSUMOylation enzymes for MTA1. Moreover, MTA1 contains a functional SUMO-interacting motif (SIM) at its C terminus, and SIM is required for the efficient SUMOylation of MTA1. SUMO conjugation on Lys-509, which is located within the SUMO consensus site, together with SIM synergistically regulates the co-repressor activity of MTA1 on PS2 transcription, probably by recruiting HDAC2 onto the PS2 promoter. Interestingly, MTA1 may up-regulate the expression of SUMO2 via interaction with RNA polymerase II and SP1 at the SUMO2 promoter. These findings not only provide novel mechanistic insights into the regulation of the transcriptional repressor function of MTA1 by SUMOylation and SIM but also uncover a potential function of MTA1 in modulating the SUMOylation pathway.

MTA1 coregulation of transglutaminase 2 expression and function during inflammatory response.

Although both metastatic tumor antigen 1 (MTA1), a master chromatin modifier, and transglutaminase 2 (TG2), a multifunctional enzyme, are known to be activated during inflammation, it remains unknown whether these molecules regulate inflammatory response in a coordinated manner. Here we investigated the role of MTA1 in the regulation of TG2 expression in bacterial lipopolysaccharide (LPS)-stimulated mammalian cells. While studying the impact of MTA1 status on global gene expression, we unexpectedly discovered that MTA1 depletion impairs the basal as well as the LPS-induced expression of TG2 in multiple experimental systems. We found that TG2 is a chromatin target of MTA1 and of NF-κB signaling in LPS-stimulated cells. In addition, LPS-mediated stimulation of TG2 expression is accompanied by the enhanced recruitment of MTA1, p65RelA, and RNA polymerase II to the NF-κB consensus sites in the TG2 promoter. Interestingly, both the recruitment of p65 and TG2 expression are effectively blocked by a pharmacological inhibitor of the NF-κB pathway. These findings reveal an obligatory coregulatory role of MTA1 in the regulation of TG2 expression and of the MTA1-TG2 pathway, at least in part, in LPS modulation of the NF-κB signaling in stimulated macrophages.

Inflammatory response to liver fluke Opisthorchis viverrini in mice depends on host master coregulator MTA1, a marker for parasite-induced cholangiocarcinoma in humans.

UNLABELLED: Based on the recently established role for the master coregulator MTA1 and MTA1-containing nuclear remodeling complexes in oncogenesis and inflammation, we explored the links between parasitism by the carcinogenic liver fluke Opisthorchis viverrini and this coregulator using both an Mta1(-/-) mouse model of infection and a tissue microarray of liver fluke-induced human cholangiocarcinomas (CCAs). Intense foci of inflammation and periductal fibrosis in the liver and kidneys of wild-type Mta1(+/+) mice were evident at 23 days postinfection with O. viverrini. In contrast, little inflammatory response was observed in the same organs of infected Mta1(-/-) mice. Livers of infected Mta1(+/+) mice revealed strong up-regulation of fibrosis-associated markers such as cytokeratins 18 and 19 and annexin 2, as determined both by immunostaining and by reverse-transcription polymerase chain reaction compared with infected Mta1(-/-) mice. CD4 expression was up-regulated by infection in the livers of both experimental groups; however, its levels were several-fold higher in the Mta1(+/+) mice than in infected Mta1(-/-) mice. Mta1(-/-) infected mice also exhibited significantly higher systemic and hepatic levels of host cytokines such as interleukin (IL)-12p70, IL-10, and interferon-γ compared with the levels of these cytokines in the Mta1(+/+) mice, suggesting an essential role of MTA1 in the cross-regulation of the Th1 and Th2 responses, presumably due to chromatin remodeling of the target chromatin genes. Immunohistochemical analysis of ≈ 300 liver tissue cores from confirmed cases of O. viverrini-induced CCA showed that MTA1 expression was elevated in >80% of the specimens. CONCLUSION: These findings suggest that MTA1 status plays an important role in conferring an optimal cytokine response in mice following infection with O. viverrini and is a major player in parasite-induced CCA in humans.

The metastasis-associated protein-1 gene encodes a host permissive factor for schistosomiasis, a leading global cause of inflammation and cancer.

UNLABELLED: Schistosoma haematobium is responsible for two-thirds of the world's 200 million to 400 million cases of human schistosomiasis. It is a group 1 carcinogen and a leading cause of bladder cancer that occurs after years of chronic inflammation, fibrosis, and hyperproliferation in the host liver. The coevolution of blood flukes of the genus Schistosoma and their human hosts is paradigmatic of long-term parasite development, survival, and maintenance in mammals. However, the contribution of host genes, especially those discrete from the immune system, necessary for parasite establishment and development remains poorly understood. This study investigated the role of metastasis-associated protein-1 gene (Mta1) product in the survival of S. haematobium and productive infection in the host. Using a Mta-1 null mouse model, here we provide genetic evidence to suggest that MTA1 expression positively influences survival and/or maturation of schistosomes in the host to patency, as we reproducibly recovered significantly fewer S. haematobium worms and eggs from Mta1-/- mice than wild-type mice. In addition, we found a distinct loss of cytokine interdependence and aberrant Th1 and Th2 cytokine responses in the Mta1-/- mice compared to age-matched wild-type mice. Thus, utilizing this Mta1-null mouse model, we identified a distinct contribution of the mammalian MTA1 in establishing a productive host-parasite interaction and thus revealed a host factor critical for the optimal survival of schistosomes and successful parasitism. Moreover, MTA1 appears to play a significant role in driving inflammatory responses to schistosome egg-induced hepatic granulomata reactions, and thus offers a survival cue for parasitism as well as an obligatory contribution of liver in schistosomiasis. CONCLUSION: These findings raise the possibility to develop intervention strategies targeting MTA1 to reduce the global burden of schistosomiasis, inflammation, and neoplasia.

Acetylation-dependent oncogenic activity of metastasis-associated protein 1 co-regulator.

High expression of metastasis-associated protein 1 co-regulator (MTA1), a component of the nuclear remodelling and histone deacetylase complex, has been associated with human tumours. However, the precise role of MTA1 in tumorigenesis remains unknown. In this study, we show that induced levels of MTA1 are sufficient to transform Rat1 fibroblasts and that the transforming potential of MTA1 is dependent on its acetylation at Lys626. Underlying mechanisms of MTA1-mediated transformation include activation of the Ras-Raf pathway by MTA1 but not by acetylation-inactive MTA1; this was due to the repression of Galphai2 transcription, which negatively influences Ras activation. We observed that acetylated MTA1-histone deacetylase (HDAC) interaction was required for the recruitment of the MTA1-HDAC complex to the Galphai2 regulatory element and consequently for the repression of Galphai2 transcription and expression leading to activation of the Ras-Raf pathway. The findings presented in this study provide for the first time--to the best of our knowledge--evidence of acetylation-dependent oncogenic activity of a cancer-relevant gene product.