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Glioblastoma (GBM) is the most common and lethal brain tumor. Characterization of GBM with poor prognosis although new treatment modalities hasn’t been changed up to date. New molecular targets in order to overcome resistance and recurrence are needed. Autophagy, a self-catabolic process, has two converse role in tumorigenesis, acting both as a tumor suppressor and a protector of cancer cell survival, tumor dormancy, progression, and therapeutic resistance. Autophagy with its dual role become target of cancer therapy. Midkine (MK), a growth factor with cytokine activity, is expressed highly during embryogenesis, but interestingly, MK is not detectable in healthy adults and only re-appears in the body as a part of the pathogenesis of diseases such as cancer. MK promotes proliferation, migration, anti-apoptotic manner, mitogenesis, transforming, and angiogenesis in various cells. In the central nervous system. High MK expression correlates with the progression of human astrocytomas, MK mRNA and protein expression levels were higher in high-grade astrocytomas as GBMs than in low-grade astrocytomas. MK correlates with the poor prognosis of GBM. This review is focused on the relationship between MK and autophagy in GBM and GBM treatment and pro­mising usage of MK in order to switch autophagy to cell death.

Endometriosis is an enigmatic disease, the etiology of which is poorly understood. The lesion of endometriosis is preferentially located in the peritoneum around the ovary. We therefore speculated that some local factor derived from the ovary is involved in the development of endometriosis. Relatively high concentrations (higher than 200 ng/ml) of midkine are detected in follicular fluids in the ovary, implying its roles in the follicular growth. In contrast, concentrations of midkine in peritoneal fluid are around 1 ng/ml. Midkine concentrations in peritoneal fluid increase after ovulation, suggesting that midkine in follicular fluid erupting at ovulation contribute to the concentrations in peritoneal fluid. Interestingly, midkine (higher than 100 ng/ml) stimulates the proliferation of endometriotic stromal cells. Therefore, it is plausible that endometriotic lesions are stimulated to grow by directly exposed to midkine in follicular fluid at the time of ovulation. In addition, midkine concentrations in peritoneal fluid are higher in women with advanced endometriosis compared to those with no or minimal endometriosis, further suggesting the involvement of MK in endometriosis.

Since its discovery almost 25 years ago, numerous functions have been reported for the growth factor midkine in different cellular contexts. In this chapter, we will discuss approaches to understand the function of midkine in the developing nervous system of vertebrates. Functional studies in several animal models have revealed midkine’s role in important cell fate decisions during embryonic neurogenesis. Among these models, zebrafish has been particularly useful for the analysis of midkine, as a genome duplication during teleost evolution resulted in two midkine genes with non-overlapping expression and activities, allowing a detailed dissection of functional aspects during neurogenesis. In zebrafish, the knock-down of midkine results in the absence of distinct cell types in the developing spinal cord, highlighting its importance in cell fate specification during neural patterning. In humans, midkine and its putative receptor Anaplastic Lymphoma Kinase (ALK) are implicated in a variety of neurological disorders including cancers of neural origin. Therefore, studies that aim at understanding midkines’ function and activity in the developing nervous system could become extremely helpful for understanding the molecular mechanisms underlying these diseases. This in turn could lead to the development of novel strategies that use midkine and its associated factors as promising therapeutic targets.

The determination of human midkine plays a key role in medical research and diagnostics. Monoclonal and polyclonal antibodies have been generated and used for immunological midkine detection due to their high specificity and sensitivity. Different antibody-based methods with various applications have been described in literature for human midkine detection, e.g. immunohistochemistry, Western blot detection and enzyme-linked immunosorbent assays (ELISA) techniques. In particular, ELISAs are a common tool for the quantitative midkine determination in human specimen because they are easy to handle and require low technical support. The study of the authors (BioGenes GmbH) included a comparison of different commercial ELISA kits concerning the determination of different midkine standards as well as human serum measurements. As a result, differences in the assay reactivity were observed depending on the used MK standard preparations. Furthermore, the measured midkine serum levels were highly variable and depended on the patient and on the ELISA kit used. In conclusion, the ELISA quantification of midkine is regarded as difficult and requires a well adjusted system of immunological reagents. Midkine levels determined with different midkine ELISAs are only partially comparable.

Elevated midkine transcription in human tumors but not in normal tissues suggests a possible use of the transcriptional unit to activate an exogenous gene preferentially in tumors. The restricted expression in tumors, mediated by the midkine promoter region, enabled us to examine a potential gene therapy for cancer. Advantages of the midkine regulatory sequences that can activate foreign gene expressions have been evidenced in a number of preclinical investigations. A promoter region of the midkine gene linked with a reporter gene showed that the 5′-side control region efficiently drove the reporter transcript in many kinds of human tumors and that the transcriptional activity was stronger than that of the SV40 T antigen promoter. Transduction of human tumors with the midkine regulatory region linked with a suicide gene increased susceptibility of the tumors to a responding prodrug. Replication-competent adenoviruses genetically modified with the midkine regulatory sequences showed preferential viral replication in tumors and subsequently cell death of the targeted tumors. The midkine promoter is thus a valuable tool to activate a therapeutic gene or viral replication in tumors and is perhaps an indispensable unit for gene medicine, which is hopefully available as novel therapeutics for intractable cancer in future.

Cerebrovascular disease is the leading cause of death and disability in Japan and most Western countries. Gene transfer techniques may be applicable to the treatment of serious types of stroke, since several experimental studies have revealed the usefulness of gene therapy in the prevention of vasospasm after subarachnoid hemorrhage, reduction of infarct size and improvement of neuronal functions. Midkine is reported to have anti-apoptotic effects, and the gene transfer of midkine to the ischemic brain may provide neuroprotective effects. Furthermore, chemotactic effects of midkine could be utilized for the neurogenesis and functional recovery. We describe the novel possibility of the stroke treatment using midkine gene transfer.

The heparin-binding growth and differentiation factor/mitogen, midkine, was shown to play a critical role in embryonic development, prenatal differentiation and tumorigenesis, specifically as a regulator of the epithelial-mesenchymal transition/transdifferentiation. Along with other growth factors/mitogens, midkine was reported to activate the key signaling pathways leading to ability tumor cells to migrate and support cell invasiveness. Midkine was also found to act as an anti-apoptotic and pro-survival factor. In this report, we showed the interplay between the midkine- and p63-dependent signaling pathways potentially leading to the epithelial-mesenchymal transdifferentation. We showed that the midkine transcription is regulated by p63 supported by promoter/reporter and chromatin immunoprecipitation assays. We further showed that midkine induces expression of ΔNp63 isotypes potentially leading to cell migration and cell invasiveness through the Stat3-dependent activation of the ΔNp63 promoter activity. Overall, we suggest a novel feedback loop mechanism underlying crosstalk between midkine and p63 pathways during epithelial-mesenchymal transdifferentation.

Midkine (MK) and pleotrophin (PTN) are members of a family of heparin-binding growth factors that promotes the proliferation, differentiation, survival, adhesion, migration, and other activities of responding cells, they have become promising molecular targets for the treatment of diseases including malignancy and immune mediated inflammatory diseases. MK is involved in the regulation of organ development and the etiology of many diseases. This chapter focuses on both cell protective and cytokine like effects of MK in different inflammatory conditions at the cellular/systemic levels.

Prostate cancer is the most common malignancy in the developed countries. Midkine is expressed in prostate cancer but not in normal prostate, indicating that midkine can be used as a biomarker for diagnosis of prostate cancer. The levels of midkine expression are higher in the late stage and metastatic prostate tumors compared to the early stage prostate tumors, hinting at a potential use of midkine as a prognostic biomarker. However, no study has been conducted to evaluate serum midkine levels in diagnosis or prognosis of prostate cancer. Midkine expression is increased in several castration resistant prostate cancer cell lines, suggesting a possible role of midkine in development of castration resistant prostate cancer. Midkine expression is upregulated by several growth factors and cytokines including tumor necrosis factor α and androgens. Midkine has been shown to activate extracellular signal regulated kinase (ERK1/2) and p38 pathways, which is associated with cellular survival in LNCaP cells. Midkine siRNA and antisense oligos have been shown to inhibit PC3 cell growth in vitro and in vivo, which appears to synergize with chemotherapeutical drug paclitaxel. C-terminal peptides, small molecular weight compounds, and humanized monoclonal neutralizing antibodies hold potential in the prevention and treatment of prostate cancer.

Peer-reviewed articles published through 15th May 2011 were reviewed within three databases. Out of 7.560 articles, 26 studies were selected in this systematic review, which summarize the state of art on circulating midkine in cancer, inflammatory and infectious diseases, emphasizing its possible application as disease marker.

In the adult skeleton bone remodeling, the continuous turnover of bone matrix and mineral by bone resorption and bone formation, needs to be in balance to maintain bone mass. This balance is ensured by the coordinated activities of osteoclasts (bone-resorbing cells) and osteoblasts (bone-forming cells), which are regulated by numerous factors, including systemic hormones, the mechanical environment, and locally released growth factors. One of these growth factors is midkine (Mdk), which has been shown to play a remarkable role in bone remodeling. In previous studies, Mdk has already been shown to play a role in bone development. Thus, it has been demonstrated to be expressed in bone formation and fracture Midkine and bone formationbone formation and mechanically induced bone remodeling, thereby raising the possibility that Mdk-specific antagonists might represent a therapeutic option for low bone mass diseases, such as osteoporosis.

The kidneys are a crucial part of the urinary system that perform primarily homeostatic functions, including maintaining acid–base balance and regulating blood pressure. Both acute kidney injuries (AKIs) and chronic kidney diseases (CKDs) are involved in the progression of various other diseases, such as cardiovascular and cerebrovascular diseases and acute lung injury, eventually resulting in higher mortality and mobility. Midkine (MK), which is induced by retinoic acid, regulates the balance of epithelial and stromal progenitor cell populations of the metanephric mesenchyme during nephrogenesis. In adults, MK is expressed in damaged tissues and involved in the reparative process. MK enhances the migration of inflammatory cells directly and also through the induction of chemokines in kidney disease. The upregulation of chemokines such as macrophage inflammatory protein-2 (MIP-2) for neutrophils and macrophage chemotactic protein-1 (MCP-1) for macrophages in acute and/or chronic kidney damage is diminished in the MK-deficient mice and wild mice treated by MK inhibitors. Since MK is also a regulator of the renin-angiotensin system, it might be a key molecule involved in the induction of hypertension in chronic nephrititis. MK is attracting much attention in relation to kidney diseases, for which its inhibition is expected to be an effective treatment.

Midkine (MK) is strongly expressed during the midgestation period of embryogenesis, while its expression is nearly undetectable in the normal adult brain. However, recent evidences suggest that MK may play various roles in the pathological phenomena of the adult brain. MK binds strongly to Abeta peptides and neutralizes its cytotoxic activity. The findings about elevated MK levels in brain and serum of patients with Alzheimer disease (AD) suggest that MK may be induced to counteract Abeta-related pathophysiology in AD. On the other hand, MK was found to promote the survival of mouse mesencephalic (mainly dopaminergic) neurons in culture. Midkine-deficient (Mdk(−/−)) mice transiently exhibited a delay in postnatal hippocampal development with a working memory deficit and increased anxiety only at the age of 4 weeks. Adult Mdk(−/−) mice exhibited a hypodopaminergic state in the striatum, the prepulse inhibition deficits, and social interaction impairments. These findings suggested that midkine may contribute to the pathophysiology of dopamine-related disorders including schizophrenia and Parkinson’s disease.

Midkine (MK) is known to be overexpressed in various human malignant tumors, although its expression is low or undetectable in normal adult tissues. Its detection in the tumors or in the blood has been associated with poor disease outcome while its blockade was found to contribute to tumor regression. Recent investigations on the immunogenic properties of MK have showed that it contains appropriate sequences to stimulate specific CD8 and CD4 T lymphocytes. CD8 T cells were identified in humans by in vitro amplification or in transgenic mice by immunization. They were cytotoxic and recognized MK-expressing tumors. CD4 T cells specific for MK appear to recognize it in association with multiple HLA class II molecules. In light of these observations, MK provides an innovative opportunity to design specific vaccines that target many tumors. In addition, considering the multiple functions and the wide expression of MK, these vaccines would exhibit multiple advantages that are discussed in this paper.

The immune system of humans can be viewed as two parallel and communicating units, i.e. innate and adaptive immunity. Innate immunity provides a readily available, sometimes inducible, and less specific defense against potentially harmful pathogens of the environment. Adaptive immunity is slower, highly specific via production of immunoglobulins, and has an immunologic memory (e.g. as seen in vaccination). The mechanisms and functions of innate immunity have caught increasing attention in recent years. An important part, executing antimicrobial activity of innate immunity, is antimicrobial polypeptides (AMPs). Midkine shares several features with AMPs, including cationicity at physiological pH, heparin-binding properties, domains containing anti-parallel β-sheets (similar to the classical AMPs β-defensins), and expression by epithelial cells. In addition, midkine recruits and activates neutrophils, and acts as a growth factor, features shared with many AMPs. Recently, midkine was shown to have strong bactericidal activity against both gram-positive and gram-negative bacteria in vitro, an activity exerted through membrane-disrupting properties. Bactericidal activity was also found in the early midkine-orthologue Miple2 of Drosophila melanogaster, indicating conserved antibacterial activity in this small family of molecules during evolution. In this review, we discuss midkine in the context of innate immunity in general and particularly as an AMP.

Midkine (MK) is a heparin-binding cytokine or growth factor and promotes survival, growth, migration, gene expression and other activities of target cells. MK is rich in both basic amino acids and cysteine and has about 50% sequence identity with pleiotrophin (PTN). MK is largely composed of two domains, both of which contain three antiparallel β-sheets. The MK receptor is a molecular complex containing proteoglycans, low density lipoprotein receptor-related protein, integrins and other molecules. MK is strongly expressed during embryogenesis especially in the midgestation period. MK is involved in neurogenesis, epithelial-mesenchymal interactions and mesoderm remodeling. Mice deficient in the MK gene (Mdk) exhibit only slight abnormalities during development and reproduction, while mice doubly deficient in both MK and PTN exhibit severe abnormalities including female infertility. In adult tissue, MK is generally not expressed, but its expression is induced after injury. The induced MK either promotes tissue repair as in the brain and heart or enhances inflammatory responses as in the kidney. MK expression is also upregulated in most malignant tumors and enhances tumor invasion and resistance to chemotherapy. Thus both MK and its inhibitors are expected to be valuable as therapeutics.

Midkine (MK) is expressed in synovial tissues of patients with rheumatoid arthritis, and MK concentration are elevated in synovial fluid and serum of the vast majority of patients with the disease. Serum MK levels might aid the diagnosis of rheumatoid arthritis, since 71.9% of patients that test negative for rheumatoid factor exhibited elevated levels. Mice deficient in the MK gene showed less symptom upon antibody-induced arthritis than did wild-type mice, indicating MK to be involved in the disease. MK is considered to contribute to the pathogenesis by enhancing the migration of inflammatory leukocytes, suppressing regulatory T cells, promoting the differentiation of osteoclasts and suppressing osteoblasts. In experiments in vitro, MK alone promoted osteoclastic differentiation from human macrophage-like cells, and MK and receptor activator of NF-ĸB ligand (RANKL) in combination promoted the differentiation of mouse macrophages. Inhibitors of MK might be useful for treating rheumatoid arthritis. Chondroitin sulfate E and siRNA to MK have already been shown to partially suppress antibody-induced arthritis.

Cardiovascular diseases are a burden on the healthcare and economy of developed countries, because they are among the leading causes of morbidity and mortality. Percutaneous coronary intervention, including stenting, is now an established treatment for coronary artery disease. However, the stent treatment has long been compromised by the limitation of restenosis. The pathology of neointima formation, the fundamental process of vascular restenosis, consists of several sequential steps, i.e., endothelial injury, thrombosis, inflammatory cell adherence to the vessel wall, cytokine and chemokine release, and smooth muscle cell migration and proliferation. To overcome the problem of restenosis, the drug-eluting stent was recently developed. However, this has led to the new concern of late or very late thromboses due to impaired reendothelialization. In this context, the growth factor midkine (MK) shows various interesting characteristics. MK is expressed in the neointima. MK promotes the migration of inflammatory cells as well as smooth muscle cells, and thereby contributes to neointima pathogenesis. MK-deficient mice show reduction in neointima formation. Moreover, MK knockdown can suppress restenosis. Although it remains to be determined whether MK knockdown affects reendothelialization, MK appears to be an attractive molecular target for the next generation of drug-eluting stents.

Midkine (MK), a heparin-binding growth factor, has been demonstrated frequently and highly expressed in a variety of human carcinomas, including hepatocellular carcinoma (HCC). There is mounting evidence indicating that MK plays a significant role in carcinogenesis-related activities, such as proliferation, migration, anti-apoptosis, mitogenesis, transformation, and angiogenesis. Futhermore, siRNA, anti-sense oligonucleotides or antibody to MK has yielded great effects in anti-prolierative activities to HCC cells. Therefore, MK appears to be a potential molecular target for therapy of HCC.

Osteosarcoma is a malignant tumour arising from transformed cells of mesenchymal origin. It is the most common malignant bone tumour of the teenage years. Because there is no prognostic marker available except metastasis and because molecular therapy has not yet been developed in osteosarcoma, the search continues for useful biomarkers and effective molecular targets for this disease.