Increased expression of mdig predicts poorer survival of the breast cancer patients

Epigenetic regulation of breast cancer metastasis

Breast cancer is the most frequently diagnosed malignancy and the second leading cause of cancer-related mortality among women worldwide. Recurrent metastasis is associated with poor patient outcomes and poses a significant challenge in breast cancer therapies. Cancer cells adapting to a new tissue microenvironment is the key event in distant metastasis development, where the disseminating tumor cells are likely to acquire genetic and epigenetic alterations during the process of metastatic colonization. Despite several decades of research in this field, the exact mechanisms governing metastasis are not fully understood. However, emerging body of evidence indicates that in addition to genetic changes, epigenetic reprogramming of cancer cells and the metastatic niche are paramount toward successful metastasis. Here, we review and discuss the latest knowledge about the salient attributes of metastasis and epigenetic regulation in breast cancer and crucial research domains that need further investigation.

MicroRNA-140-3p inhibits proliferation and promotes apoptosis in non-small cell lung cancer by targeting MDIG

BACKGROUND

MicroRNAs (miRNAs) are associated with cancer progression. MiR-140-3p is a tumor suppressor. Nevertheless, its function in non-small cell lung cancer (NSCLC) is unclear.

METHODS

MiR-140-3p expression in NSCLC clinical specimens was examined using the TCGA database and real-time PCR. NSCLC cell proliferation and apoptosis were investigated after the miRNA overexpression. Then, mineral dust-induced gene (MDIG) levels in NSCLC clinical specimens were monitored by real-time PCR and western blotting. Bioinformatics predicated the binding of miR-140-3p to MDIG, and their relationship was validated by luciferase reporter assay. The miR-140-3p/MDIG axis was further validated through rescue experiments. The involvement of STAT3 signaling in the actions of miR-140-3p/MDIG axis was investigated.

RESULTS

MiR-140-3p was decreased in NSCLC tissues and negatively correlated with MDIG expression. Additionally, it was also lower in high-grade specimens than in low-grade ones. MiR-140-3p restrained cell proliferation, facilitated apoptosis, and inhibited STAT3 signaling in NSCLC. Interestingly, MDIG was a target of this miRNA. Furthermore, MDIG upregulation abolished miR-140-3p's effect on cell proliferation, apoptosis, and STAT3 pathway in NSCLC cells.

CONCLUSION

MiR-140-3p restrained NSCLC development through the regulation of the STAT3 pathway by targeting MDIG. This axis may be a promising target for NSCLC treatment.

Deletion of mdig enhances H3K36me3 and metastatic potential of the triple negative breast cancer cells

In this report, we provide evidence showing diminished expression of the mineral dust-induced gene (mdig), a previously identified oncogenic gene, in human triple negative breast cancer (TNBC). Using a mouse model of orthotopic xenograft of the TNBC MDA-MB-231 cells, we demonstrate that mdig promotes the growth of primary tumors but inhibits metastasis of these cells in vivo. Knockout of mdig resulted in an enhancement of H3K36me3 in the genome and upregulation of some X chromosome-linked genes for cell motility, invasion, and metastasis. Silencing MAGED2, one of the most upregulated and H3K36me3-enriched genes resulted from mdig depletion, can partially reverse the invasive migration of the mdig knockout cells. The anti-metastatic and inhibitory role of mdig on H3K36me3 was cross-validated in another cell line, A549 lung cancer cells. Together, our data suggest that mdig is antagonist against H3K36me3 that enforces expression of genes, such as MAGED2, for cell invasion and metastasis.

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Loss of mdig expression in TNBC and metastatic breast cancer

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Knockout of mdig enforces metastasis of the TNBC cells

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Mdig antagonizes H3K36me3 that promotes expression of X-linked metastatic genes

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Silencing MAGED2 reduces invasive migration of the mdig knockout cells

Epigenetics and environment in breast cancer: New paradigms for anti-cancer therapies

Breast cancer remains the most frequently diagnosed cancer in women worldwide. Delayed presentation of the disease, late stage at diagnosis, limited therapeutic options, metastasis, and relapse are the major factors contributing to breast cancer mortality. The development and progression of breast cancer is a complex and multi-step process that incorporates an accumulation of several genetic and epigenetic alterations. External environmental factors and internal cellular microenvironmental cues influence the occurrence of these alterations that drives tumorigenesis. Here, we discuss state-of-the-art information on the epigenetics of breast cancer and how environmental risk factors orchestrate major epigenetic events, emphasizing the necessity for a multidisciplinary approach toward a better understanding of the gene-environment interactions implicated in breast cancer. Since epigenetic modifications are reversible and are susceptible to extrinsic and intrinsic stimuli, they offer potential avenues that can be targeted for designing robust breast cancer therapies.

JMJD family proteins in cancer and inflammation

The occurrence of cancer entails a series of genetic mutations that favor uncontrollable tumor growth. It is believed that various factors collectively contribute to cancer, and there is no one single explanation for tumorigenesis. Epigenetic changes such as the dysregulation of enzymes modifying DNA or histones are actively involved in oncogenesis and inflammatory response. The methylation of lysine residues on histone proteins represents a class of post-translational modifications. The human Jumonji C domain-containing (JMJD) protein family consists of more than 30 members. The JMJD proteins have long been identified with histone lysine demethylases (KDM) and histone arginine demethylases activities and thus could function as epigenetic modulators in physiological processes and diseases. Importantly, growing evidence has demonstrated the aberrant expression of JMJD proteins in cancer and inflammatory diseases, which might serve as an underlying mechanism for the initiation and progression of such diseases. Here, we discuss the role of key JMJD proteins in cancer and inflammation, including the intensively studied histone lysine demethylases, as well as the understudied group of JMJD members. In particular, we focused on epigenetic changes induced by each JMJD member and summarized recent research progress evaluating their therapeutic potential for the treatment of cancer and inflammatory diseases.

Depletion of Mdig Changes Proteomic Profiling in Triple Negative Breast Cancer Cells

Triple-negative breast cancers are highly aggressive with an overall poor prognosis and limited therapeutic options. We had previously investigated the role of mdig, an oncogenic gene induced by some environmental risk factors, on the pathogenesis of breast cancer. However, a comprehensive analysis of the proteomic profile affected by mdig in triple-negative breast cancer has not been determined yet. Using label-free bottom-up quantitative proteomics, we compared wildtype control and mdig knockout MDA-MB-231 cells and identified the proteins and pathways that are significantly altered with mdig deletion. A total of 904 differentially expressed (p < 0.005) proteins were identified in the KO cells. Approximately 30 pathways and networks linked to the pathogenicity of breast cancer were either up- or downregulated, such as EIF2 signaling, the unfolded protein response, and isoleucine degradation I. Ingenuity Pathway Analysis established that the differentially expressed proteins have relevant biological actions in cell growth, motility, and malignancy. These data provide the first insight into protein expression patterns in breast cancer associated with a complete disruption of the mdig gene and yielded substantial information on the key proteins, biological processes, and pathways modulated by mdig that contribute to breast cancer tumorigenicity and invasiveness.

MDIG, a 2‑oxoglutarate‑dependent oxygenase, acts as an oncogene and predicts the prognosis of multiple types of cancer

Recent studies have indicated that mineral dust‑induced gene (MDIG) is an oncogene induced by environmental factors, which has a key role in the development and progression of various tumor types, through epigenetic modifications; however, there are no previous pan‑cancer analyses of MDIG. In the present study, a comprehensive pan‑cancer analysis of MDIG was performed using public databases. The results demonstrated that MDIG was upregulated in tumor tissue samples compared with normal tissue, that it was present in all cancer cell lines and it was closely associated with the prognosis of patients with different tumor types. Furthermore, MDIG expression was closely associated with the immunological characteristics of the tumor microenvironment (TME), such as the frequency of tumor‑infiltrating immune cells, TME‑relevant signatures, immunostimulatory genes, immune checkpoint genes, chemokine receptor genes, tumor mutational burden and microsatellite instability. In parallel, high expression of MDIG was associated with improved overall survival of patients and this was verified in a cohort of patients who had received anti‑programmed cell death 1 ligand 1 treatment. Furthermore, high expression of MDIG led to multiple drug resistance in The Cancer Genome Atlas‑lung adenocarcinoma cohort. In addition, gene set variant analysis and gene set enrichment analysis indicated that MDIG was involved in cell cycle regulation. In vitro experiments suggested that MDIG promoted cell proliferation through the mTOR complex 2/Akt and pyruvate dehydrogenase kinase 1/Akt signaling pathways. In summary, the present study suggests that MDIG may be a prognostic biomarker and therapeutic target for various cancer types.

Molecular Signatures of JMJD10/MINA53 in Gastric Cancer

The JMJD10 gene and its encoded protein MYC-induced nuclear antigen (MINA53) are associated with multiple cancers. Besides having both an oncogenic and tumor suppressor function, the intricate role of JMJD10 in cancer is complex as it depends on the cancer type. In particular, the functional role of JMJD10/MINA53 in gastric cancer has been poorly understood. In this study, we have unraveled the molecular signatures and functional roles of JMJD10/MINA53 in gastric cancer by multiple approaches, i.e., multi-omics bioinformatics study, analysis of human gastric cancer tissues, and studies in vitro using knockdown or overexpression strategies in gastric cancer cell lines. The results indicated that the JMJD10 gene and MINA53 protein are commonly overexpressed in cancer patients. JMJD10/MINA53 is involved in the regulation of proliferation and survival of gastric cancer by controlling cell cycle gene expression. These processes are highly associated with MINA53 enzymatic activity in the regulation of H3K9me3 methylation status and controlling activation of AP-1 signaling pathways. This highlights the oncogenic role of JMJD10/MINA53 in gastric cancer and opens the opportunity to develop therapeutic targeting of JMJD10/MINA53 in gastric cancer.

Mdig promotes oncogenic gene expression through antagonizing repressive histone methylation markers

The mineral dust-induced gene (mdig) is overexpressed in a number of human cancers, suggesting critical roles of this gene played on the pathogenesis of cancers. Unlike several other JmjC-domain containing proteins that exhibit histone demethylase activity, it remains enigmatic whether mdig is involved in the demethylation processes of the histone proteins. Methods: To provide direct evidence suggesting contribution of mdig to the demethylation of histone proteins, we recently examined the histone methylation profiles in human bronchial epithelial cells as well as two cancer cell lines with mdig knockout through CRISPR-Cas9 gene editing. Results: Global histone methylation analysis revealed a pronounced increase of the repressive histone trimethylation in three different cell types with mdig depletion, including trimethylation of lysines 9 and 27 on histone H3 (H3K9me3, H3K27me3) and trimethylation of lysine 20 of histone H4 (H4K20me3). Importantly, data from both ChIP-seq and RNA-seq suggested that genetic disruption of mdig enriches repressive histone trimethylation and inhibits expression of target genes in the oncogenic pathways of cell growth, stemness of the cells, tissue fibrosis, and cell motility. Conclusion: Taken together, our study provides the first insight into the molecular effects of mdig as an antagonist for repressive histone methylation markers and suggests that targeting mdig may represent a new area to explore in cancer therapy.

MDIG promotes cisplatin resistance of lung adenocarcinoma by regulating ABC transporter expression via activation of the WNT/β-catenin signaling pathway

Mineral dust-induced gene (MDIG) is a proto- oncogene associated with lung cancer that serves a key role in the biological processes of tumorigenesis. The aim of the present study was to determine whether MDIG is involved in cisplatin (DDP) resistance in lung adenocarcinoma, and to investigate the associated molecular mechanism. In the present study, MDIG-knockdown and MDIG-overexpressing A549 cells and DDP-resistant A549/DDP cells were initially constructed, and then the mRNA and protein expression levels of MDIG and ATP-binding cassette (ABC) transporters (ABCB1, ABCC1, ABCG2), and the expression levels of the major associated proteins in the WNT/β-catenin pathway were determined by reverse transcription-quantitative PCR and Western blotting experiments. The results revealed that the mRNA and protein expression levels of MDIG in A549/DDP cells were significantly higher compared with those in A549 cells, and that the protein expression levels of MDIG increased in a dose-dependent manner with increasing DDP concentrations. Overexpression of MDIG in A549 and A549/DDP cells led to an increase in the IC₅₀ value, whereas silencing of MDIG led to a clear reduction in the IC₅₀ value. The overexpression of MDIG in the A549 and A549/DDP cells markedly upregulated the mRNA and protein expression levels of ABCB1, ABCC1, ABCG2, WNT family member 5A, WNT family member 3A and active β-catenin, and these were markedly decreased following MDIG silencing. Taken together, these results demonstrated that the DDP resistance of lung adenocarcinoma may be associated with an upregulation of MDIG expression, and that the expression levels of MDIG are positively associated with the degree of DDP resistance. Furthermore, MDIG promoted the expression of ABC transporters in tumor cells by activating the WNT/β-catenin signaling pathway, which may, in turn, lead to DDP resistance in lung adenocarcinoma.

New discoveries of mdig in the epigenetic regulation of cancers

Mineral dust-induced gene (mdig) encodes a member of the evolutionarily conserved JmjC family proteins that play fundamental roles in regulating chromatin-based processes as well as transcription of the genes in eukaryotic cells. This gene is also named as myc-induced nuclear antigen 53 (MINA), nucleolar protein 52 (NO52) and ribosomal oxygenase 2 (RIOX2). Increased expression of mdig had been noted in a number of human cancers, esp. lung cancer. Emerging evidence suggests that the oncogenic activity of mdig is most likely achieved through its regulation on the demethylation of histone proteins, despite it lacks the structural identities of the demethylases. Here, we discuss the latest discoveries on the characteristics of the mdig protein and its roles in a wide variety of normal and carcinogenic processes. We will also provide perspectives on how mdig is involved in the maintenance and differentiation of the embryonic stem cells, somatic stem cells and cancer stem cells.

The emerging roles of ribosomal histidyl hydroxylases in cell biology, physiology and disease

Hydroxylation is a novel protein modification catalyzed by a family of oxygenases that depend on fundamental nutrients and metabolites for activity. Protein hydroxylases have been implicated in a variety of key cellular processes that play important roles in both normal homeostasis and pathogenesis. Here, in this review, we summarize the current literature on a highly conserved sub-family of oxygenases that catalyze protein histidyl hydroxylation. We discuss the evidence supporting the biochemical assignment of these emerging enzymes as ribosomal protein hydroxylases, and provide an overview of their role in immunology, bone development, and cancer.

Loss of mdig expression enhances DNA and histone methylation and metastasis of aggressive breast cancer

We previously reported that expression of an environmentally induced gene, mineral dust-induced gene (mdig), predicts overall survival in breast cancer patients. In the present report, we further demonstrate the differential roles of mdig between earlier- and later-stage breast cancers. In noncancerous breast, mdig is a proliferation factor for cell growth and cell motility. In breast cancer, however, higher levels of mdig negatively regulate the migration and invasion of cancer cells. Assessment of global DNA methylation, chromatin accessibility and H3K9me3 heterochromatin signature suggests that silencing mdig enhances DNA and histone methylation. Through immunostaining and data mining, we found that mdig is significantly upregulated in noninvasive and/or earlier-stage breast cancers. In contrast, in triple-negative and other invasive breast cancers, diminished mdig expression was noted, indicating that the loss of mdig expression could be an important feature of aggressive breast cancers. Taken together, our data suggest that mdig is a new biomarker that likely promotes tumor growth in the early stages of breast cancer while acting as a tumor suppressor to inhibit invasion and metastasis in later-stage tumors.

Differential expression of an environmentally-induced gene appears to influence the growth of breast cancer tumors, thus providing a valuable biomarker and therapeutic target. Environmental factors can influence cancerous tumor development by interfering with epigenetic processes such as DNA and histone methylation. For example, the mineral dust induced gene (mdig) is over-expressed in coal miners who are susceptible to lung cancer. Now, Fei Chen, a pioneer in toxicology and carcinogenesis research at the Wayne State University in Detroit, USA, and his team have demonstrated that mdig also plays important roles in breast cancer. The gene is upregulated in early, non-invasive tumors, where it regulates cell growth, motility and invasion by influencing DNA and histone methylation. However, mdig expression drops in later stage or more aggressive tumor types. When the researchers abrogated mdig expression completely, they observed an enhanced DNA and histone methylation, suggesting the gene has a demethylase role and is implicated in regulating the epigenetic landscape under neoplastic conditions.

Phylogenetic and genomic analyses of the ribosomal oxygenases Riox1 (No66) and Riox2 (Mina53) provide new insights into their evolution

BACKGROUND

Translation of specific mRNAs can be highly regulated in different cells, tissues or under pathological conditions. Ribosome heterogeneity can originate from variable expression or post-translational modifications of ribosomal proteins. The ribosomal oxygenases RIOX1 (NO66) and RIOX2 (MINA53) modify ribosomal proteins by histidine hydroxylation. A similar mechanism is present in prokaryotes. Thus, ribosome hydroxylation may be a well-conserved regulatory mechanism with implications in disease and development. However, little is known about the evolutionary history of Riox1 and Riox2 genes and their encoded proteins across eukaryotic taxa.

RESULTS

In this study, we have analysed Riox1 and Riox2 orthologous genes from 49 metazoen species and have constructed phylogenomic trees for both genes. Our genomic and phylogenetic analyses revealed that Arthropoda, Annelida, Nematoda and Mollusca lack the Riox2 gene, although in the early phylum Cnidaria both genes, Riox1 and Riox2, are present and expressed. Riox1 is an intronless single-exon-gene in several species, including humans. In contrast to Riox2, Riox1 is ubiquitously present throughout the animal kingdom suggesting that Riox1 is the phylogenetically older gene from which Riox2 has evolved. Both proteins have maintained a unique protein architecture with conservation of active sites within the JmjC domains, a dimerization domain, and a winged-helix domain. In addition, Riox1 proteins possess a unique N-terminal extension domain. Immunofluorescence analyses in Hela cells and in Hydra vulgaris identified a nucleolar localisation signal within the extended N-terminal domain of human RIOX1 and an altered subnuclear localisation for the Hydra Riox2.

CONCLUSIONS

Conserved active site residues and uniform protein domain architecture suggest a consistent enzymatic activity within the Riox orthologs throughout evolution. However, differences in genomic architecture, like single exon genes and alterations in subnuclear localisation, as described for Hydra, point towards adaption mechanisms that may correlate with taxa- or species-specific requirements. The diversification of Riox1/Riox2 gene structures throughout evolution suggest that functional requirements in expression of protein isoforms and/or subcellular localisation of proteins may have evolved by adaptation to lifestyle.

Pathological and prognostic role of mdig in pancreatic cancer

Pancreatic cancer is a highly aggressive malignant disease having very limited therapeutic options that ultimately results in its poor prognosis. It is still elusive on the etiology and tumorigenic mechanisms of pancreatic cancer. In the present report, we provide evidence showing involvement of the mineral dust-induced gene (mdig) in the pathogenesis and prognosis of the pancreatic cancer. Using immunohistochemistry approach on human pancreatic cancer tissue microarray, we found differential expression of mdig in pancreatic adenocarcinoma and normal pancreas. Based on the staining intensities of mdig in these tissue samples, we found that 12% of the cancer tissues were strongly positive for mdig, 39% and 31% were moderately and weakly positive respectively. Several alternatively spliced mdig mRNAs were detected in the selected pancreatic cancer cell lines. Through R2 platform for the patient survival analysis (http://r2.amc.nl), we found that enrichment of some specific exon of mdig predicates different survival rate of the pancreatic cancer patients. In summary, our findings may help in assessing the role of mdig in the pathogenesis of the pancreatic cancer and the prognosis of the pancreatic cancer patients.

Proteomic Characterization of the World Trade Center dust-activated mdig and c-myc signaling circuit linked to multiple myeloma

Several epidemiological studies suggested an increased incidence rate of multiple myeloma (MM) among first responders and other individuals who exposed to World Trade Center (WTC) dust. In this report, we provided evidence showing that WTC dust is potent in inducing mdig protein and/or mRNA in bronchial epithelial cells, B cells and MM cell lines. An increased mdig expression in MM bone marrow was observed, which is associated with the disease progression and prognosis of the MM patients. Through integrative genomics and proteomics approaches, we further demonstrated that mdig directly interacts with c-myc and JAK1 in MM cell lines, which contributes to hyperactivation of the IL-6-JAK-STAT3 signaling important for the pathogenesis of MM. Genetic silencing of mdig reduced activity of the major downstream effectors in the IL-6-JAK-STAT3 pathway. Taken together, these data suggest that WTC dust may be one of the key etiological factors for those who had been exposed for the development of MM by activating mdig and c-myc signaling circuit linked to the IL-6-JAK-STAT3 pathway essential for the tumorigenesis of the malignant plasma cells.

The proteomic investigation reveals interaction of mdig protein with the machinery of DNA double-strand break repair

To investigate how mineral dust-induced gene (mdig, also named as mina53, MINA, or NO52) promotes carcinogenesis through inducing active chromatin, we performed proteomics analyses for the interacting proteins that were co-immunoprecipitated by anti-mdig antibody from either the lung cancer cell line A549 cells or the human bronchial epithelial cell line BEAS-2B cells. On SDS-PAGE gels, three to five unique protein bands were consistently observed in the complexes pulled-down by mdig antibody, but not the control IgG. In addition to the mdig protein, several DNA repair or chromatin binding proteins, including XRCC5, XRCC6, RBBP4, CBX8, PRMT5, and TDRD, were identified in the complexes by the proteomics analyses using both Orbitrap Fusion and Orbitrap XL nanoESI-MS/MS in four independent experiments. The interaction of mdig with some of these proteins was further validated by co-immunoprecipitation using antibodies against mdig and its partner proteins, respectively. These data, thus, provide evidence suggesting that mdig accomplishes its functions on chromatin, DNA repair and cell growth through interacting with the partner proteins.

Transforming growth factor-β and Notch ligands act as opposing environmental cues in regulating the plasticity of type 3 innate lymphoid cells

Group 3 innate lymphoid cells (ILC3s) are composed of subsets that are either positive or negative for the natural cytotoxicity receptor (NCR) NKp46 (encoded by Ncr1). ILC3s are located at mucosal sites, such as in the intestine and lung, where they are exposed to billions of commensal microbes and potentially harmful pathogens. Together with T cells, the various ILC3 subsets maintain the balance between homeostasis and immune activation. Through genetic mapping, we identified a previously uncharacterized subset of NCR(-) ILC3s in mice that transiently express Ncr1, demonstrating previously undescribed heterogeneity within the ILC3 population. In addition, we showed that sustained Notch signaling was required for the maintenance of the NCR(+) phenotype and that the cytokine transforming growth factor-β (TGF-β) impaired the development of NCR(+) ILC3s. Thus, the plasticity of ILC3s is regulated by the balance between the opposing effects of Notch and TGF-β signaling, maintaining homeostasis in the face of continual challenges.

Complementarity and redundancy of IL-22-producing innate lymphoid cells

Intestinal T cells and group 3 innate lymphoid cells (ILC3 cells) control the composition of the microbiota and gut immune responses. Within the gut, ILC3 subsets coexist that either express or lack the natural cytoxicity receptor (NCR) NKp46. We identified here the transcriptional signature associated with the transcription factor T-bet-dependent differentiation of NCR(-) ILC3 cells into NCR(+) ILC3 cells. Contrary to the prevailing view, we found by conditional deletion of the key ILC3 genes Stat3, Il22, Tbx21 and Mcl1 that NCR(+) ILC3 cells were redundant for the control of mouse colonic infection with Citrobacter rodentium in the presence of T cells. However, NCR(+) ILC3 cells were essential for cecal homeostasis. Our data show that interplay between intestinal ILC3 cells and adaptive lymphocytes results in robust complementary failsafe mechanisms that ensure gut homeostasis.

Oncoprotein mdig contributes to silica-induced pulmonary fibrosis by altering balance between Th17 and Treg T cells

Mineral dust-induced gene (mdig, also named Mina53) was first identified from alveolar macrophages of the coal miners with chronic lung inflammation or fibrosis, but how this gene is involved in lung diseases is poorly understood. Here we show that heterozygotic knockout of mdig (mdig+/-) ameliorates silica-induced lung fibrosis by altering the balance between Th17 cells and Treg cells. Relative to the wild type (WT) mice, infiltration of the macrophages and Th17 cells was reduced in lungs from silica-exposed mdig+/- mice. In contrast, an increased infiltration of the T regulatory (Treg) cells to the lung intestitium was observed in the mdig+/- mice treated with silica. Both the number of Th17 cells in the lung lymph nodes and the level of IL-17 in the bronchoalveolar lavage fluids were decreased in the mdig+/- mice in response to silica. Thus, these results suggest that mdig may contribute to silica-induced lung fibrosis by altering the balance between Th17 and Treg cells. Genetic deficiency of mdig impairs Th17 cell infiltration and function, but favors infiltration of the Treg cells, the immune suppressive T cells that are able to limit the inflammatory responses by repressing the Th17 cells and macrophages.

Current understanding of mdig/MINA in human cancers

Mineral dust-induced gene, mdig has recently been identified and is known to be overexpressed in a majority of human cancers and holds predictive power in the poor prognosis of the disease. Mdig is an environmentally expressed gene that is involved in cell proliferation, neoplastic transformation and immune regulation. With the advancement in deciphering the prognostic role of mdig in human cancers, our understanding on how mdig renders a normal cell to undergo malignant transformation is still very limited. This article reviews the current knowledge of the mdig gene in context to human neoplasias and its relation to the clinico-pathologic factors predicting the outcome of the disease in patients. It also emphasizes on the promising role of mdig that can serve as a potential candidate for biomarker discovery and as a therapeutic target in inflammation and cancers. Considering the recent advances in understanding the underlying mechanisms of tumor formation, more preclinical and clinical research is required to validate the potential of using mdig as a novel biological target of therapeutic and diagnostic value.

Carcinogenic metalloid arsenic induces expression of mdig oncogene through JNK and STAT3 activation

Environmental or occupational exposure to arsenic, a chemical element classified as metalloid, has been associated with cancer of the lung, skin, bladder, liver, etc. Mdig (mineral dust-induced gene) is a newly identified oncogene linked to occupational lung diseases and lung cancer. It is unclear whether mdig is also involved in arsenic-induced malignant transformation of the lung cells. By using human bronchial epithelial cells and human lung cancer cell lines, we showed that arsenic was able to induce expression of mdig. We further demonstrated that this mdig induction by arsenic was partially dependent on the JNK and STAT3 signaling pathways. Disruption of the JNK or STAT3 by either chemical inhibitors or siRNAs diminished arsenic-induced accumulation of mdig mRNA and protein. Furthermore, we also showed that microRNA-21 (miR-21) and Akt were down-stream effectors of the JNK and STAT3 signaling pathways in arsenic-induced mdig expression. Transfection of the cells with anti-miR-21 or pre-treatment of the cells with Akt inhibitor blunted mdig induction by arsenic. Clinically, the levels of mdig can be applied to predict the disease progression, the first progression (FP), in non-small cell lung cancer (NSCLC) patients. Taken together, our data suggest that mdig may play important roles on the pathogenesis of arsenic-induced lung cancer and that JNK and STAT3 signaling pathways are essential in mediating arsenic-induced mdig expression.

Paradoxical roles of mineral dust induced gene on cell proliferation and migration/invasion

Increased expression of mineral dust-induced gene (mdig, also named as mina53, MINA, or NO52) has been observed in a number of human cancers. The mechanism of how mdig contribute to the pathogenesis of cancer remains to be fully elucidated. In this report, we demonstrated that overexpression of mdig decreased the nuclear staining signal by 4′,6-diamidino-2-phenylindole (DAPI), along with a considerable enhancement in cell proliferation. Silencing mdig by shRNA resulted in a statistically significant decrease of cell proliferation. Intriguingly, mdig overexpression reduced the capacity of the cells in migration and invasion in vitro, whereas silencing mdig by shRNA/siRNA enhanced migration and invasion. Clinically, we found that increased expression of mdig in cancer tissues correlates with poorer overall survival of the lung cancer patients, esp., for those without lymph node metastasis. Taken together, our results suggest that mdig plays opposite roles on cell growth and motility, which possibly indicates the paradoxical effect of mdig at the different stages of carcinogenesis.