Screening of novel Midkine binding protein by BioID2-based proximity labeling

Midkine (MK), a heparin-binding growth factor, is associated with the poor prognosis of the pediatric tumor, neuroblastoma. MK would be a druggable target as many studies showed inhibition of its function in various cancers suppressed tumor developments. To establish the therapy targeting MK, identification of its binding partners, and elucidation of its intracellular signaling are needed. It was reported that exogenous MK induced phosphorylation of ribosomal protein S6 (RPS6) downstream of mTOR signaling. Using RPS6 phosphorylation as a marker of MK response, we searched for MK reactive cell lines. We found that MK cell lines expressing less MK tended to respond better to MK. Next, using an MK reactive neuroblastoma cell line, MK-knocked down SH-SY5Y cells, we employed a proximity-dependent biotin identification method, which was invented to evaluate protein-protein interactions by biotinylation. We confirmed that secreted MK fused to the biotin ligase BioID2 (MK-BioID2) was able to biotinylate proteins from the cells. Biotinylated proteins were identified by liquid chromatography-mass spectrometry analyses. Twenty five proteins were found to be overlapped after three independent experiments, among which insulin-like growth binding protein 2 (IGFBP2) was further analyzed. IGFBP2 was indeed detected with immunoblotting after streptavidin pull down of MK-BioID2 labeled cell extract of MK-knocked down SH-SY5Y cells. Our study suggests that the BioID2 method is useful to identify binding partners of growth factors.

PCA-based unsupervised feature extraction for gene expression analysis of COVID-19 patients

Coronavirus disease 2019 (COVID-19) is raging worldwide. This potentially fatal infectious disease is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the complete mechanism of COVID-19 is not well understood. Therefore, we analyzed gene expression profiles of COVID-19 patients to identify disease-related genes through an innovative machine learning method that enables a data-driven strategy for gene selection from a data set with a small number of samples and many candidates. Principal-component-analysis-based unsupervised feature extraction (PCAUFE) was applied to the RNA expression profiles of 16 COVID-19 patients and 18 healthy control subjects. The results identified 123 genes as critical for COVID-19 progression from 60,683 candidate probes, including immune-related genes. The 123 genes were enriched in binding sites for transcription factors NFKB1 and RELA, which are involved in various biological phenomena such as immune response and cell survival: the primary mediator of canonical nuclear factor-kappa B (NF-κB) activity is the heterodimer RelA-p50. The genes were also enriched in histone modification H3K36me3, and they largely overlapped the target genes of NFKB1 and RELA. We found that the overlapping genes were downregulated in COVID-19 patients. These results suggest that canonical NF-κB activity was suppressed by H3K36me3 in COVID-19 patient blood.

Extra-virgin olive oil and the gut-brain axis: influence on gut microbiota, mucosal immunity, and cardiometabolic and cognitive health

Extra-virgin olive oil (EVOO), a popular functional food and major source of fat in the Mediterranean diet, possesses a variety of healthful components, including monounsaturated fatty acids and bioactive phenolic compounds that, individually and collectively, exert beneficial effects on cardiometabolic markers of health and act as neuroprotective agents through their anti-inflammatory and antioxidant activities. The gut microbiota and health of the intestinal environment are now considered important factors in the development of obesity, metabolic disease, and even certain neurodegenerative conditions via the gut-brain axis. Recently, data are emerging which demonstrate that the health-promoting benefits of EVOO may also extend to the gut microbiota. In this review, we aimed to examine findings from recent studies regarding the impact of EVOO on gut microbiota and intestinal health and explore how modulations in composition of gut microbiota, production of microbially produced products, and activity and functioning of the mucosal immune system may lead to favorable outcomes in cardiovascular, metabolic, and cognitive health.

Gut microbial composition of elderly women born in the Japanese longevity village Ogimi

Ogimi is one of Japan’s longevity villages and is located in Okinawa Prefecture. In this study, we focused on the elderly women living in the village, classified them into two groups based on whether or not they lived in Ogimi during the first 3 years of their lives, and compared the gut microbiota between the two groups. There were no differences in alpha and beta diversity; however, we found that the elderly women who lived in Ogimi during the first 3 years of their lives had a higher rate of Akkermansia muciniphila colonization in their guts.

Potent and broad anticancer activities of leaf extracts from Melia azedarach L. of the subtropical Okinawa islands

Plant extracts have been traditionally used for various therapeutic applications. By conducting an initial screening of several subtropical plants, in this study, we evaluated the anticancer activities of Melia azedarach L. The extract from Melia azedarach L. leaves (MLE) show high cytotoxic effects on cancer cells and in vivo mouse and dog tumor models. During the initial screening, MLE showed strong antiproliferative activity against HT-29 colon, A549 lung, and MKN1 gastric cancer cells. In subsequent tests, using 39 human tumor cell lines, we confirmed the potent anticancer activities of MLE. The anticancer activity of MLE was also confirmed in vivo. MLE markedly inhibited the growth of transplanted gastric MKN1 cancer xenografts in mice. To elucidate the mechanism underlying the anticancer effects of MLE, MLE-treated MKN1 cells were observed using an electron microscope; MLE treatment induced autophagy. Furthermore, western blot analysis of proteins in lysates of MLE-treated cells revealed induction of light chain 3 (LC3)-II autophagosomal proteins. Thus, MLE appeared to suppress MKN1 cell proliferation by inducing autophagy. In addition, in the mouse macrophage cell line J774A.1, MLE treatment induced TNF-α production, which might play a role in tumor growth suppression in vivo. We also performed a preclinical evaluation of MLE treatment on dogs with various cancers in veterinary hospitals. Dogs with various types of cancers showed a mean recovery of 76% when treated with MLE. Finally, we tried to identify the active substances present in MLE. All the active fractions obtained by reverse-phase chromatography contained azedarachin B-related moieties, such as 3-deacetyl-12-hydroxy-amoorastatin, 12-hydroxy-amoorastatin, and 12-hydroxyamoorastaton. In conclusion, MLE contains substances with promising anticancer effects, suggesting their future use as safe and effective anticancer agents.

Two-dimensional NMR data of a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans and schizophyllan from Schizophyllum commune

This article contains two-dimensional (2D) NMR experimental data, obtained by the Bruker BioSpin 500 MHz NMR spectrometer (Germany) which can used for the determination of primary structures of schizophyllan from Schizophyllum commune (SPG) and a water-soluble β-(1→3, 1→6)-glucan from Aureobasidium pullulans. Data include analyzed the 2D NMR spectra of these β-glucans, which are related to the subject of an article in Carbohydrate Polymers, entitled “NMR spectroscopic structural characterization of a water-soluble β-(1→3, 1→6)-glucan from A. pullulans” (Kono et al., 2017) [1]. Data can help to assign the ¹H and ¹³C chemical shifts of the structurally complex polysaccharides.

The CCR4-NOT deadenylase activity contributes to generation of induced pluripotent stem cells

Somatic cells can be reprogrammed as induced pluripotent stem cells (iPSCs) by introduction of the transcription factors, OCT3/4, KLF4, SOX2, and c-MYC. The CCR4-NOT complex is the major deadenylase in eukaryotes. Its subunits Cnot1, Cnot2, and Cnot3 maintain pluripotency and self-renewal of mouse and human embryonic stem (ES) cells and contribute to the transition from partial to full iPSCs. However, little is known about how the CCR4-NOT complex post-transcriptionally regulates the reprogramming process. Here, we show that the CCR4-NOT deadenylase subunits Cnot6, Cnot6l, Cnot7, and Cnot8, participate in regulating iPSC generation. Cnot1 knockdown suppresses expression levels of Cnot6, Cnot6l, Cnot7, and Cnot8 in mouse embryonic fibroblasts (MEFs) and decreases the number of alkaline phosphatase (ALP)-positive colonies after iPSC induction. Intriguingly, Cnot1 depletion allows Eomes and p21 mRNAs to persist, increasing their expression levels. Both mRNAs have longer poly(A) tails in Cnot1-depleted cells. Conversely, forced expression of a combination of Cnot6, Cnot6l, Cnot7, and Cnot8 increases the number of ALP-positive colonies after iPSC induction and decreases expression levels of Eomes and p21 mRNAs. Based on these observations, we propose that the CCR4-NOT deadenylase activity contributes to iPSC induction.

Expression of midkine in normal human skin, dermatitis and neoplasms: association with differentiation of keratinocytes

Midkine is a 13-kDa heparin-binding growth factor. It promotes growth, survival, migration and gene expression of various target cells and play roles in many diseases. In normal adult tissues, midkine expression is highly restricted; however, midkine expression levels are high in various malignant tumors. The major biological roles of midkine can be categorized into three areas, namely, the nervous system, cancer and inflammation. Thus far, midkine has not been studied extensively in diseased human skin. We performed immunohistochemistry tests by using anti-midkine antibodies to study the expression of midkine in normal skin and skin samples of 26 different cutaneous diseases. In addition, we investigated the expression pattern of the midkine gene in cultured keratinocytes. In normal skin, midkine expression was observed in the secretory coils of the eccrine sweat glands, outer root sheath and inner root sheath. Among the cutaneous tumors, the majority of keratinocyte-derived neoplasms were positive for midkine. Tumors that were not derived from keratinocytes were negative for midkine. In cultured keratinocytes, the midkine gene was expressed earlier than the genes required for keratinization, for example, cytokeratin 10 and transglutaminase 1. Because midkine is expressed in the keratinized areas of normal skin, neoplasms and inflammation, it may play a role as a modulator of keratinization in the skin.

The growth factor midkine regulates the renin-angiotensin system in mice

The renin-angiotensin system plays a pivotal role in regulating blood pressure and is involved in the pathogenesis of kidney disorders and other diseases. Here, we report that the growth factor midkine is what we believe to be a novel regulator of the renin-angiotensin system. The hypertension induced in mice by 5/6 nephrectomy was accompanied by renal damage and elevated plasma angiotensin II levels and was ameliorated by an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin receptor blocker. Notably, ACE activity in the lung, midkine expression in the lung, and midkine levels in the plasma were all increased after 5/6 nephrectomy. Exposure to midkine protein enhanced ACE expression in primary cultured human lung microvascular endothelial cells. Furthermore, hypertension was not induced and renal damage was less severe in midkine-deficient mice. Supplemental administration of midkine protein to midkine-deficient mice restored ACE expression in the lung and hypertension after 5/6 nephrectomy. Oxidative stress might be involved in midkine expression, since expression of NADH/NADPH oxidase-1, -2, and -4 was induced in the lung after 5/6 nephrectomy. Indeed, the antioxidative reagent tempol reduced midkine expression and plasma angiotensin II levels and consequently ameliorated hypertension. These results suggest that midkine regulates the renin-angiotensin system and mediates the kidney-lung interaction after 5/6 nephrectomy.

Plasma midkine level is a prognostic factor for human neuroblastoma

Neuroblastoma is the third-most-common solid tumor of childhood. To date, no reliable blood marker for neuroblastoma has been established. The growth factor midkine is highly expressed in human carcinomas and its knockdown leads to tumor growth suppression in animal models. The present study evaluated the plasma midkine level in human neuroblastoma patients. Plasma samples were obtained from patients found through mass screening, as well as from sporadic neuroblastoma patients. The total number of cases examined was 756. Among them, prognostic information was available for 175 sporadic cases and 287 mass-screening cases. Midkine levels were significantly higher in neuroblastoma patients, including both mass-screening cases and sporadic cases, than in non-tumor controls (P < 0.0001). The midkine level was significantly correlated with the statuses of MYCN amplification, TRKA expression, ploidy, stage and age (P < 0.0001, < 0.0001, = 0.004, < 0.0001 and < 0.0001, respectively), which are known prognostic factors for neuroblastoma. There was a striking correlation between high plasma midkine level and poor prognosis (P < 0.0001). Within sporadic cases, the midkine level was also strikingly higher than in non-tumor controls (P < 0.0001), and correlated with the statuses of MYCN amplification and stage (P = 0.0005 and = 0.003, respectively). There was a significant correlation between high plasma midkine level and poor prognosis (P = 0.04). Taken together, the present data indicate that plasma midkine level is a prognostic factor for human neuroblastoma.

Midkine and its clinical significance in endometrial carcinoma

Midkine (MK) is a secreted heparin-binding growth factor. Several types of human cancer have increased MK expression with elevated serum levels. The purpose of this study was to determine whether MK was expressed in endometrial carcinoma and to evaluate the clinicopathological significance of serum MK in patients with endometrial carcinoma. Immunohistochemical expression of MK was evaluated in 85 endometrial carcinoma samples and 33 controls. MK expression was significantly higher in the carcinomas than in normal endometrium (P < 0.001). Interestingly, MK expression was highest at the margins of invasion and low in the superficial areas of the tumor samples. Using ELISA, we compared serum MK concentration in 120 endometrial carcinoma patients with the concentration in 46 patients with benign gynecologic tumors. Serum MK value in patients with cancer was significantly higher than that in the patients with benign diseases (P = 0.01). Patients with positive lymph node metastasis or recurrence, or cancer death, had a higher serum MK level (P = 0.008, P = 0.009, respectively). In conclusion, MK immunoreactivity in endometrial carcinoma is significantly higher than in normal endometrium. Additionally, preoperative serum MK levels are significantly correlated with prognosis and the presence of lymph node metastasis. Thus, MK may be a useful serum biomarker for identifying high risk patients of endometrial carcinoma.

Expression of the heparin-binding growth factor midkine in the cerebrospinal fluid of patients with neurological disorders

OBJECTIVE

This study was to clarify the roles of midkine (MK) in the brain.

METHODS

We determined cerebrospinal fluid MK levels in patients with neurological disorders by enzyme-linked immunoassay and immunostained autopsied brain samples in patients with meningitis.

RESULTS

MK levels were 0.37+/-0.21 ng/ml in controls (n=46, mean +/- S.D.), 0.67+/-0.19 ng/ml in patients with cerebral infarction (n=8), 1.78+/-1.32 ng/ml in patients with meningitis (n=25; ANOVA and post-hoc Fisher's PLSD test, p<0.0001), 0.31+/-0.25 ng/ml in patients with human T-lymphotrophic virus type I-associated myelopathy/tropical spastic paraparesis (n=29), and 0.42+/-0.17 ng/ml in patients with amyotrophic lateral sclerosis (n=8). The regression equations were Y=0.005X+0.498 (Y, CSF MK level; X, cell number) and Y=0.007X+0.326 (Y, MK level; X, protein level) for all CSF samples. Autopsy brain samples from patients with meningitis expressed MK weakly in mononuclear cells on immunohistochemical examination. Western blot and polymerase chain reaction analyses showed that leukocytes were MK positive. CSF MK levels were not high in patients with cerebral infarction but were increased in patients with meningitis. CSF MK levels were high in normal controls, compared to those of other cytokines. MK was expressed in choroid plexus of normal brain and released there.

CONCLUSION

Our findings suggested that MK may maintain normal adult brain as a neurotrophic factor, and that MK may be released from leucocytes in brain of patients with meningitis as an immunological mediator.

Midkine and LDL-receptor-related protein 1 contribute to the anchorage-independent cell growth of cancer cells

The growth factor midkine (MK) is highly associated with cancer progression. Knockdown of MK expression strikingly suppresses tumor growth in nude mice. Thus, MK is a candidate target for cancer treatment. LDL-receptor-related protein 1 (LRP1) is a receptor for MK. We found that among the four ligand-binding domains of LRP1, the N-terminal half of the second domain (designated as MK-TRAP) had the strongest affinity to MK. MK-TRAP bound to MK, but not to HB-GAM/pleiotrophin, basic fibroblast growth factor or platelet-derived growth factor (PDGF)-BB. Exogenous MK-TRAP inhibited the binding between MK and LRP1. G401 cells that transiently or stably overexpress MK-TRAP showed decreased cell growth in monolayer culture and reduced colony formation in soft agar, which could be rescued by exogenous MK administration. MK-TRAP collected from conditioned medium also inhibited anchorage-independent growth of G401 cells and CMT-93 cells. Anti-MK antibody also inhibited the anchorage-independent growth. CMT-93 cells stably expressing MK-TRAP formed smaller tumors in a xenograft nude mouse model than control cells. Moreover, GST-RAP, a potent inhibitor of LRP1, inhibited the anchorage-independent growth of control G401 cells but not that of MK-TRAP stable transformants. Collectively, these data demonstrate a crucial role of MK-LRP1 signaling in anchorage-independent cell growth.

Midkine as a novel target for antibody therapy in osteosarcoma

Osteosarcoma is a malignant tumor with poor prognosis, and lack of accurate prognostic factors is one of the reasons that make this tumor difficult to cure. The heparin-binding growth factor, midkine is involved in generation and progression of many types of tumors. However, the relationship between midkine and osteosarcoma has been unclear. We show here that midkine is overexpressed in osteosarcoma and the level of midkine expression is correlated with prognosis (P<0.05; log-rank test). Treatment with functional antibodies against midkine suppresses growth of osteosarcoma cell lines, 9N2, 3N1, Saos-2, and NOS-1, to 25-65% of untreated controls. Our results suggest that midkine is useful as a prognostic marker, and is a candidate therapeutic target for osetosarcomas.

Protein tyrosine phosphatase receptor type Z is inactivated by ligand-induced oligomerization

Receptor-type protein tyrosine phosphatases (RPTPs) are considered to transduce extracellular signals across the membrane through changes in their PTP activity, however, our understanding of the regulatory mechanism is still limited. Here, we show that pleiotrophin (PTN), a natural ligand for protein tyrosine phosphatase receptor type Z (Ptprz) (also called PTPzeta/RPTPbeta), inactivates Ptprz through oligomerization and increases the tyrosine phosphorylation of substrates for Ptprz, G protein-coupled receptor kinase-interactor 1 (Git1) and membrane associated guanylate kinase, WW and PDZ domain containing 1 (Magi1). Oligomerization of Ptprz by an artificial dimerizer or polyclonal antibodies against its extracellular region also leads to inactivation, indicating that Ptprz is active in the monomeric form and inactivated by ligand-induced oligomerization.

Doxorubicin-Conjugated Anti-Midkine Monoclonal Antibody as a Potential Anti-Tumor Drug

BACKGROUND

Midkine is a heparin-binding growth factor preferentially expressed in tumor cells. The present study was performed to utilize anti-midkine antibody for tumor therapy.

METHODS

A monoclonal antibody to midkine was raised by immunizing mice deficient in the midkine gene. The binding site of the antibody was studied by using N-terminal half and C-terminal half of midkine, both of which were chemically synthesized. Doxorubicin (DOX)-conjugate of the antibody was produced by chemical conjugation. The effects of the antibody and the conjugate on cell growth were examined using a midkine-secreting tumor cell, i.e. human hepatocellular carcinoma cell (HepG2).

RESULTS

The monoclonal antibody bound to the N-terminal half of midkine. The antibody did not inhibit the growth of HepG2 cells probably because the active domain of midkine is in the C-terminal half. We produced the antibody conjugated with DOX with the hope that the conjugate would be internalized accompanied with midkine. Indeed, the antibody-DOX conjugate significantly inhibited the growth of HepG2 cells compared with DOX-conjugated control IgG.

CONCLUSION

The result raises the possibility of using anti-midkine antibody conjugated with DOX for cancer therapy.

Midkine protects hepatocellular carcinoma cells against TRAIL-mediated apoptosis through down-regulation of caspase-3 activity

BACKGROUND

It is believed that midkine (MK), a heparin-binding growth factor, plays an important role in carcinogenesis. However, the biologic mechanism of MK in hepatocellular carcinoma has not been clarified to date. The objective of the current study was to investigate the antiapoptotic role of MK in a human hepatoma cell line.

METHODS

The human hepatoma cell line HepG2 was used to study the antiapoptotic effect of MK. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/actinomycin D (ActD)-induced apoptosis was detected using a 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphophenyl)-2H-tetrazolium monosodium salt (WST-8) assay, a caspase-3 activity assay, a caspase-8 activity assay, and flow cytometric analysis.

RESULTS

TRAIL had a potent, dose-dependent inductive effect on cell death in HepG2 cells, for which viable cell counts decreased to 6.3% of the control count at a TRAIL concentration of 100 ng/mL in the presence of 500 ng/mL ActD. Flow cytometry was used to demonstrate that apoptosis induced by TRAIL/ActD was in fact the cause of cell death. According to the WST-8 assay, MK pretreatment resulted in the suppression of TRAIL/ActD-mediated apoptosis in HepG2 cells, although cell viability did not increase when HepG2 cells were treated with MK alone. Caspase-3 activity was down-regulated when MK was added, but caspase-8 activity was high in both the absence and presence of MK.

CONCLUSIONS

The results of the current study indicate that MK acts as an antiapoptotic factor in HepG2 cells through the down-regulation of caspase-3 activity.

Preoperative serum midkine concentration is a prognostic marker for esophageal squamous cell carcinoma

High preoperative serum midkine concentration is associated with poor survival in patients with esophageal cancer, even after radical surgery, and thus may have prognostic value. Midkine (MK), a heparin-binding growth factor, is expressed in numerous cancer tissues, and serum MK (S-MK) concentrations are increased in patients with various neoplasms. The aim of this study is to evaluate the clinical significance of S-MK in patients with esophageal squamous cell cancer (SCC). S-MK was measured by enzyme-linked immunosorbent assay in 135 healthy controls, 16 patients with benign esophageal disease, and 93 patients with primary esophageal SCC before surgery. The serum concentrations of carcinoembryonic antigen (CEA), SCC antigen (SCC-Ag), and cytokeratin 19 fragment (CYFRA21-1) were also evaluated. All patients with esophageal SCC underwent radical esophagectomy. Tumor MK expression was assessed by immunohistochemistry in 14 fresh tumor specimens. To determine whether S-MK is of value as a prognostic factor, the authors conducted a survival analysis using Cox's proportional hazards model. S-MK values in patients with esophageal SCC were significantly higher than those in healthy controls (417 +/- 342 pg/ml vs. 154 +/- 76 pg/ml, P < 0.001). Using 300 pg/ml as the cut-off value (representing the mean + 2 standard deviations of the S-MK of healthy controls), 61% of patients with esophageal SCC were classified as positive. MK expression by the tumor was significantly associated with high level of S-MK. High S-MK (>/= 300 pg/ml) was associated with tumor size, immunoreactivity and poor survival. Multivariate analysis indicated that S-MK was an independent prognostic factor. S-MK may be a useful tumor marker for esophageal SCC. Increased preoperative S-MK in patients with esophageal SCC is associated with poor survival.

High levels of urinary midkine in various cancer patients

Midkine (MK) is a heparin-binding growth factor, which promotes growth, migration, and survival of various cells, and MK expression is increased in many human carcinomas. We determined the urinary MK level by enzyme-linked immunoassay. Taking 311pg/mg creatinine as a cut-off level, 70% of patients with various carcinomas (n=142) gave positive values, while only 5.5% of healthy volunteers (n=330) did. In case of gastric carcinoma, 17 out of 21 patients with stage 1 tumor were positive. Urinary MK levels are expected to become a convenient marker as an aid in detection of tumors.

Correlation of elevated level of blood midkine with poor prognostic factors of human neuroblastomas

The heparin-binding growth factor midkine (MK) is the product of a retinoic acid-responsive gene, and is implicated in neuronal survival and differentiation, and carcinogenesis. We previously reported that MK mRNA expression is elevated in neuroblastoma specimens at all stages, whereas pleiotrophin, the other member of the MK family, is expressed at high levels in favourable neuroblastomas. As MK is a secretory protein, it can be detected in the blood. Here, we show a significant correlation of the plasma MK level with prognostic factors of neuroblastomas. The plasma MK level was determined in 220 patients with neuroblastomas, and compared with that in children without malignant tumors (n=17, <500 pg ml(-1)). The plasma MK level became significantly elevated with advancing stages (stage 1: 445 pg ml(-1) (median), n=73; stage 2: 589, n=39; stage 3: 864, n=40; stage 4: 1445, n=56; and stage 4S: 2439, n=12). More importantly, a higher MK level was strongly correlated with poor prognostic factors: over 1 year of age (P=0.0299), MYCN amplification (P<0.0001), low TrkA expression (P=0.0005), nonmass screening, sporadic neuroblastomas (P<0.0001), and diploidy/tetraploidy (P=0.0007). Thus, these results demonstrate that the plasma MK level is a good marker for evaluating the progression of neuroblastomas. Moreover, considering the ability of antisense MK oligodeoxyribonucleotide to suppress tumour growth of colorectal carcinoma cells in nude mice, as recently reported, the present study suggests that MK is a possible candidate molecular target for therapy for neuroblastomas.

Increased serum midkine concentration as a possible tumor marker in patients with superficial esophageal cancer

Midkine, a heparin-binding growth factor, is expressed in numerous cancer tissues and is reportedly elevated in patients with various neoplasms. The aim of this study was to evaluate the clinicopathological significance of serum midkine concentration (S-MK) in patients with superficial esophageal squamous cell carcinoma (SCC). Pretreatment S-MK was measured by enzyme-linked immunosorbent assay in 135 healthy controls, 16 patients with benign esophageal disease, and 60 patients with primary superficial esophageal squamous cell cancer (SESCC). All patients with SESCC underwent curative resection. The disease was staged according to TNM/UICC guidelines. Serum concentrations of carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC-Ag), and cytokeratin 19 fragment (CYFRA21-1) were also evaluated in the same populations. S-MK in patients with SESCC (388+/-411 pg/ml) was significantly higher than in benign esophageal disease or healthy controls (183+/-73 and 154+/-76 pg/ml, respectively). Using the mean + 2 standard deviations of healthy control S-MK (300 pg/ml) as the cut-off level, 50% of patients with esophageal SESCC were deemed positive. This S-MK positivity rate for detecting SESCC was significantly higher than for other tumor markers. Thus, S-MK may be useful as a tumor marker to detect SESCC.

Receptor-type protein tyrosine phosphatase zeta as a component of the signaling receptor complex for midkine-dependent survival of embryonic neurons

Midkine (MK), a heparin-binding growth factor, suppresses apoptosis of embryonic neurons in culture, induced by serum deprivation. Receptor-type protein tyrosine phosphatase zeta (PTP zeta) is a chondroitin sulfate proteoglycan with a transmembrane domain and intracellular tyrosine phosphatase domains. The activity of MK was abolished by digestion with chondroitinase ABC, or addition of the antibody to PTP zeta, while digestion with heparitinase showed no significant effect. These results suggested that the survival-promoting signal of MK was received by a receptor complex containing PTP zeta. Low density lipoprotein receptor-related protein (LRP) has been identified as another component of the signaling receptor. Ectodomains of two related proteins expressed on neurons, namely LRP6 and apoE receptor 2, were FLAG-tagged and examined for MK binding, using MK-agarose column. Both the ectodomains were found to exhibit calcium-dependent binding to MK. These proteins may participate in MK signaling in certain cases. The survival-promoting activity of MK was abolished by PP1, an inhibitor of src protein kinase, pertussis toxin, an inhibitor of G protein-linked signaling and sodium orthovanadate, an inhibitor of PTPs.

Glycosaminoglycan structures required for strong binding to midkine, a heparin-binding growth factor

Midkine (MK), a heparin-binding growth factor, binds strongly to oversulfated structures in chondroitin sulfates (CSs) and heparan sulfate. To elucidate the carbohydrate structure actually involved in the strong binding, dissected brains from 13-day mouse embryos were incubated with [14C]-glucosamine. The labeled glycosaminoglycans were fractionated by MK-agarose affinity chromatography to a weakly binding fraction, which was eluted by 0.5 M NaCl, and a strongly binding fraction, which was eluted by higher NaCl concentrations. Among the unsaturated disaccharides released from the strongly binding fraction by chondroitinase ABC, DeltaDi-diSE with 4,6-disulfated N-acetylgalactosamine accounted for 32.3%, whereas its content was lower in the weakly binding fraction. Artificial CS-E structure was formed using N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase purified from squid or recombinant human enzyme. Analysis of the products and their interaction with MK revealed that E units without 3-O-sulfation of glucuronic acid are sufficient for strong binding, provided that they are present as a dense cluster. Among the sulfated disaccharides released by heparitinase digestion, the trisulfated one, DeltaDiHS-triS, was the most abundant in the strongly binding fraction and was lower in the weakly binding fraction. Together with results of previous studies, we concluded that the multivalent trisulfated heparin-like unit is another structure involved in strong binding to MK.

Glypican-2 binds to midkine: the role of glypican-2 in neuronal cell adhesion and neurite outgrowth

Cell-surface heparan sulfate proteoglycans participate in molecular events that regulate cell adhesion, migration, and proliferation. The present study was performed to elucidate whether glypican-2 plays a role in interactions of neurons with midkine (MK), a heparin-binding neuroregulatory factor. MK bound to heparan sulfate chains of glypican-2 in a manner similar to syndecan-3. Microbeads coated with MK or poly-L-lysine induced clustering of glypican-2 as well as syndecan-3. Substratum-bound MK or poly-L-lysine induced cell adhesion of N2a neuroblastoma cells, while only MK promoted neurite outgrowth of these cells. Ligation of cell-surface glypican-2 with MK or an antibody against epitope-tagged glypican-2 induced cell adhesion and promoted neurite outgrowth. These results verified that cell-surface glypican-2 bound to MK and suggested that MK-glypican-2 interactions participate in neuronal cell migration and neurite outgrowth. In addition, we observed different localization of epitope-tagged glypican-2 and syndecan-3 on the surface of N2a cells; the result suggested that they may play different roles in MK-mediated neural function.

Haptotactic migration induced by midkine. Involvement of protein-tyrosine phosphatase zeta. Mitogen-activated protein kinase, and phosphatidylinositol 3-kinase

Midkine, a heparin-binding growth factor, plays a critical role in cell migration causing suppression of neointima formation in midkine-deficient mice. Here we have determined the molecules essential for midkine-induced migration. Midkine induced haptotaxis of osteoblast-like cells, which was abrogated by the soluble form of midkine or pleiotrophin, a midkine-homologous protein. Chondroitin sulfate B, E, chondroitinase ABC, B, and orthovanadate, an inhibitor of protein-tyrosine phosphatase, suppressed the migration. Supporting these data, the cells examined expressed PTPzeta, a receptor-type protein-tyrosine phosphatase that exhibits high affinity to both midkine and pleiotrophin and harbors chondroitin sulfate chains. Furthermore, strong synergism between midkine and platelet-derived growth factor in migration was detected. The use of specific inhibitors demonstrated that mitogen-activated protein (MAP) kinase and protein-tyrosine phosphatase were involved in midkine-induced haptotaxis but not PDGF-induced chemotaxis, whereas phosphatidylinositol 3 (PI3)-kinase and protein kinase C were involved in both functions. Midkine activated both PI3-kinase and MAP kinases, the latter activation was blocked by a PI3-kinase inhibitor. Midkine further recruited PTPzeta and PI3-kinase. These results indicate that PTPzeta and concerted signaling involving PI3-kinase and MAP kinase are required for midkine-induced migration and demonstrate for the first time the synergism between midkine and platelet-derived growth factor in cell migration.

Intraventricular administration of the neurotrophic factor midkine ameliorates hippocampal delayed neuronal death following transient forebrain ischemia in gerbils

Midkine (MK) is a growth factor with neurotrophic activities, and is expressed during the early stages of experimental cerebral infarction in rats in the zone surrounding the infarct. To evaluate in vivo activity of MK in preventing neuronal death, MK produced in yeast (Pichia pastoris) was administered into the brain ventricle immediately before occlusion of the bilateral common carotid artery of Mongolian gerbils. MK administration at the dose of 0.5-2 microg immediately before occlusion was found to ameliorate delayed neuronal death in the hippocampal CA1 region caused by transient ischemia 7 days after the insult. The hippocampal neurons of the MK-administered gerbils tended to degenerate 14 and 21 days after the insult, but their numbers remained higher than those in saline-administered controls; however, the hippocampal neurons were degenerated 28 days after the insult. MK administration at 2 h after occlusion did not ameliorate the neuronal death. These findings suggested that the therapeutic time window was narrow. The two to four times repeated administration of 2 microg MK immediately before and at 1, 2, or 3 weeks after the occlusion were not significantly different for the hippocampal neuronal death at 28 days after the insult compared with a single injection, but were significantly effective compared with vehicle administration alone. These findings suggested that the therapeutic time window was relatively narrow. The potent neuroprotective activity of MK observed in vivo suggested that MK might be useful as a therapeutic reagent for prevention of neuronal death in neurodegenerative diseases.

An approach to the removal of yeast specific O-linked oligo-mannoses from human midkine expressed in Pichia pastoris using site-specific mutagenesis

Human midkine is expressed and secreted in the medium under the control of an AOX1 gene promoter in Pichia pastoris using its own secretion signal. The midkine precursor is properly processed to yield the correct amino-terminus of mature midkine. However, more than half of the product receives yeast specific mannosylations. The sites for the mannosylations were determined to be the three threonine residues in the carboxy-terminal region of human midkine. In order to obtain non-mannosylated midkine, alanine residues were substituted for the three threonine residues by site specific mutagenesis. HPLC and mass spectrometry confirmed that the mutant midkine contained almost no mannose residues. Despite the amino acid substitutions in the carboxy-terminal region, mutant human midkine, promoted CHO cell proliferation as well as normal midkine.

Overexpression of midkine in pancreatic duct adenocarcinomas induced by N-Nitrosobis(2-oxopropyl)amine in hamsters and their cell lines

The expression of midkine (MK) was investigated in pancreatic ductal hyperplasias, atypical hyperplasias and adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters, and in hamster ductal adenocarcinoma cell lines (HPD-1NR, -2NR and -3NR). MK mRNA was clearly overexpressed in invasive pancreatic duct adenocarcinomas (PCs) and the three cell lines as assessed by northern blot analysis, and MK protein expression increased from ductal hyperplasia through atypical hyperplasias, intraductal carcinomas and invasive PCs by immunohistochemistry. The extent of overexpression of MK mRNA in PCs was almost the same as in hamster whole embryonic tissue. MK is reported to be a retinoid-responsive gene, but MK mRNA expression was not affected by treatment with all-trans retinoic acid (tRA) or N-(4-hydroxyphenyl)retinamide (4-HPR) in HPD-1NR cells. The results thus suggest that MK expression is involved in the development and progression of pancreatic ductal adenocarcinomas induced by BOP in hamsters, with loss of upregulation by retinoic acid.

Serum midkine levels are increased in patients with various types of carcinomas

The level of expression of midkine (MK), a heparin-binding growth factor, is increased in many types of human carcinomas. An enzyme-linked immunoassay, which utilizes a combination of rabbit and chicken antibodies revealed that serum MK level in the controls (n = 135) was 0.154 +/- 0.076 (mean +/- SD) ng ml(-1)with an apparent cut-off value as 0.5 ng ml(-1). Serum MK level was significantly elevated in the cancer patients (n = 150) (P< 0.001); 87% of the patients showed levels of more than 0.5 ng ml(-1). All ten types of cancer examined showed a similar profile of serum MK level. There was no or weak correlation between C-reactive protein level, a marker of inflammation, and serum MK level. Furthermore, in case of gastric carcinoma and lung carcinoma, patients with stage I carcinoma already showed elevated serum MK levels. The present results indicated that serum MK could serve as a general tumour marker with a good potential for clinical application.

A heparin-binding growth factor, midkine, binds to a chondroitin sulfate proteoglycan, PG-M/versican

Midkine is a heparin-binding growth factor with survival-promoting and migration-enhancing activities. In order to understand the regulation of midkine signaling, we isolated midkine-binding proteoglycans from day 13 mouse embryos, when midkine is intensely expressed. Deglycosylation followed by SDS/PAGE revealed various protein bands; one of these was identified as PG-M/versican by in gel trypsin digestion and sequencing the resulting peptides. PG-M/versican isolated from day 13 mouse embryos bound midkine with a Kd of 1.0 nM. Pleiotrophin/heparin-binding growth-associated molecule, which has a structure related to midkine, was also bound similarly. Digestion with chondroitinase ABC, AC-I or B abolished the binding to midkine. Heparin as well as chondroitin sulfate D and E inhibited the binding. After chondroitinase ABC digestion, the midkine-binding PG-M/versican released 4-sulfated, 6-sulfated, 2, 6-disulfated and 4,6-disulfated unsaturated disaccharides. These results suggest that midkine binds to a polysulfated domain in the chondroitin sulfate chain with a region of dermatan sulfate structure. This proteoglycan may modulate the midkine activity, as binding to midkine can enhance midkine action by concentrating it to the cell periphery or inhibit the action by competing with the binding to a signaling receptor.

LDL receptor-related protein as a component of the midkine receptor

Midkine (MK) is a heparin-binding growth factor with migration-promoting and survival-promoting activities. To identify signaling receptor(s) of MK, membrane glycoproteins with MK-binding activity were isolated from day 13 mouse embryos by lectin- and MK-affinity chromatography. SDS-PAGE followed by protein sequence analysis revealed the presence of LDL receptor-related protein (LRP) and NCAM in the fraction. The dissociation constant of binding between LRP and MK was 3.5 nM. Receptor-associated protein (RAP), which interfered with the binding, inhibited MK-dependent survival of embryonic neurons. Brushin/megalin, which is also a high molecular weight protein belonging to the LDL receptor family, bound to MK less strongly than LRP. These findings suggest that LRP is a component of the receptor complex for MK.

Neointima formation in a restenosis model is suppressed in midkine-deficient mice

Neointima formation is a common feature of atherosclerosis and restenosis after balloon angioplasty. To find a new target to suppress neointima formation, we investigated the possible role of midkine (MK), a heparin-binding growth factor with neurotrophic and chemotactic activities, in neointima formation. MK expression increased during neointima formation caused by intraluminal balloon injury of the rat carotid artery. Neointima formation in a restenosis model was strongly suppressed in MK-deficient mice. Continuous administration of MK protein to MK-deficient mice restored neointima formation. Leukocyte recruitment to the vascular walls after injury was markedly decreased in MK-deficient mice. Soluble MK as well as that bound to the substratum induced migration of macrophages in vitro. These results indicate that MK plays a critical role in neointima formation at least in part owing to its ability to mediate leukocyte recruitment.

Midkine rescues Wilms' tumor cells from cisplatin-induced apoptosis: regulation of Bcl-2 expression by Midkine

Midkine (MK) is a heparin-binding growth factor involved in diverse biological phenomena, e.g. neuronal survival, carcinogenesis, and tissue repair. MK expression is detected mainly in the kidney in adult mice. In this study, we show that, at a dose that can induce recoverable renal damage and induce apoptosis, cisplatin (CDDP) transiently suppressed MK expression in mouse kidney. In vitro, CDDP suppressed MK expression and induced apoptosis in cultured G401 cells, a Wilms' tumor cell line. Exogenous MK protein partially rescued G401 cells from CDDP-induced apoptosis. MK enhanced the expression of Bcl-2, but not that of Bcl-x(L), in G401 cells in a dose-dependent manner, and it prevented the Bcl-2 reduction due to CDDP. Moreover, Bcl-2 expression in mouse kidney was also transiently suppressed by CDDP treatment, the expression profile being similar to that of MK. These results imply that MK exerts cytoprotective activity toward a damaging insult, presumably at least in part through enhancement of the expression of Bcl-2.

Midkine binds specifically to sulfatide the role of sulfatide in cell attachment to midkine-coated surfaces

Midkine is a heparin-binding polypeptide which is implicated in the control of development and repair of various tissues. Recognition of sulfate groups in glycosaminoglycans is important for its function. To elucidate further its mechanism of action, the interactions of midkine with sulfated glycolipids were studied. Of various glycolipids and lipids examined, midkine bound strongly to sulfatide and cholesterol-3-sulfate (CHO-3-SO4) in a dose-dependent manner but failed to bind to other standard glycolipids and lipids. The properties of midkine binding to sulfatide and to CHO-3-SO4 differed in their sensitivity to inhibition by anionic polysaccharides, salt concentration and unlabeled midkine. Heparin inhibited midkine binding to sulfatide but weakly inhibited its binding to CHO-3-SO4. Liposomes bearing sulfatide carried out significant interactions with immobilized midkine, whereas those bearing CHO-3-SO4 did not. Incorporation of sulfatide into 32D cells and trypsinized COS cells enhanced 125I-labelled midkine binding, whereas incorporation of ganglioside or galactosylceramide had no effect. Furthermore, sulfatide-incorporated cells enhanced cell attachment to midkine-coated coverslips. These results indicate that midkine binds to sulfatide under physiological conditions and the midkine-sulfatide interaction may be important in controlling cell attachment.

Frequent expression of midkine gene in esophageal cancer suggests a potential usage of its promoter for suicide gene therapy

We have examined the expression of midkine (MK), a neurotrophic factor with heparin-binding activity, in human esophageal cancer cells. Seven esophageal cell lines tested expressed the transcript and 8 out of 14 human esophageal tumor specimens were positively stained with anti-MK antibody, while surrounding normal esophageal tissues in these specimens were not stained. The 5'-flanking, 2.3 kb genomic region of the MK gene was shown to drive the transcription of a reporter gene in the esophageal cell lines in a cis acting manner. Forced expression in esophageal cancer cells of herpes simplex virus-thymidine kinase gene mediated by the flanking region of the MK gene conferred sensitivity to a prodrug, ganciclovir. The 5'-upstream region of the MK gene thus possesses putative promoter activity which can be used for suicide gene-based gene therapy for esophageal cancer.

Overexpression of midkine in lung tumors induced by N-nitrosobis(2-hydroxypropyl)amine in rats and its increase with progression

The expression of midkine (MK) in lung tumors induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats was examined. The animals were administered 2000 p.p.m. of BHP in their drinking water for 12 weeks, then maintained without further treatment until being killed 20-28 weeks after the beginning of the experiment. MK mRNA expression of adenocarcinomas and squamous cell carcinomas assessed by means of the reverse transcriptase-polymerase chain reaction and northern blot analysis was significantly higher than in rat embryonic tissues (positive controls) and contrasted strongly with the lack in normal lungs. MK protein was detected immunohistochemically in 58.3% of alveolar hyperplasias, 92.3% of adenomas and 100% of adenocarcinomas and squamous cell carcinomas. The extent of staining significantly increased along with malignant progression in adenomatous (pre-)neoplastic lesions and tended to become more pronounced with malignant progression in squamous lesions. The results suggest that MK may play some essential roles in the development and progression of lung tumors induced by BHP in rats.

Heterozygote for plasmin inhibitor deficiency developing hemorrhagic tendency with advancing age

A heterozygote for congenital deficiency of plasma plasmin in inhibitor had hemorrhagic episodes repeatedly after the age of 79. Before the age of 79, he had not exhibited any hemorrhagic tendency and did not have abnormal bleeding even after surgical operations. Although heterozygotes for congenital deficiency of this inhibitor usually have no or only a mild hemorrhagic tendency, this case suggests that they may exhibit severe hemorrhagic tendency when they reach advanced ages because of age-related vascular changes producing hemostatic imbalance.

A transgenic mouse line with alpha-1,3/4-fucosyl-transferase cDNA: production and characteristics

cDNA of human alpha-1,3/4-fucosyltransferase (Fuc-TIII) was placed under the control of the chicken beta-actin promoter and cytomegalovirus enhancer, then introduced into male pronuclei of fertilized mouse eggs. A transgenic mouse line thus obtained exhibited enhanced expression of Lex (4C9) antigen in endothelial cells located in the glomerulus, sinusoidal capillaries of the liver and capillaries of the heart. Furthermore, in the transgenic mice, sialyl dimeric Lex (FH6) and sialyl Lea (2D3) antigens were strongly expressed in the glomerular endothelial cells.

Transgenic mouse lines with ectopic expression of alpha-1,3-galactosyltransferase: production and characteristics

The cDNA of murine alpha-1,3-galactosyltransferase was placed under the control of the beta-actin promoter and cytomegalovirus enhancer, then introduced into male pronuclei of fertilized mouse eggs. The three transgenic mouse lines obtained were analysed for the expression of the transferase by staining with Griffonia simplicifolia agglutinin I-B4 (GSI-B4), which is alpha-galactosyl specific. Compared with wild-type mice, all lines of transgenic mice expressed GSI-B4 binding sites more intensely in the renal tubular brush border and lung alveolar epithelium, and newly expressed them in the photoreceptor outer segments, goblet cells of the small intestine and around spermatogonia. GSI-B4 binding sites were also detected in the liver of some transgenic mice. Even though the introduced enzyme gene was expressed in embryos, it did not severely hinder embryogenesis. The transgenic mice tended to secrete more proteins in the urine than the wild type. Furthermore, low body weights, partial damage to hair growth and early death occurred more frequently in the transgenic mice.

Efficacy of recombinant human granulocyte colony-stimulating factor on neutropenia in patients with AIDS

The efficacy of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on neutropenia was evaluated in 14 patients with AIDS and AIDS-related complex (ARC). In all patients, including 11 neutropenic patients, 100 or 200 micrograms/m2 of rhG-CSF significantly increased the neutrophil counts. The response was greater in patients with higher neutrophil counts before the treatment, and was also dose-dependent. Although the effect seemed to be less potent, the agent also increased the neutrophil counts even when zidovudine (azidothymidine, AZT) and other myelosuppressive antiviral agents were administered simultaneously. These observations indicate that rhG-CSF may be beneficial in preventing and treating some secondary infections, and will make it easier to continue therapy with antiviral agents in patients with AIDS or ARC.

Preliminary evidence for inhibitory effect of glycyrrhizin on HIV replication in patients with AIDS

Glycyrrhizin (GL) at a dose of 400-1600 mg/day (7.2-30.8 mg/kg/day) was administered intravenously for a period of more than a month, on 6 separate occasions, to 3 hemophiliacs with acquired immune deficiency syndrome (AIDS). Human immunodeficiency virus type 1 (HIV-1) p24 antigen was detected at the beginning of 5 of the 6 treatment courses. Viral antigen was not detected at the end of or during 3 of the 5 treatment courses and decreased to a low level following the 2 other courses. These findings suggest that GL might inhibit HIV-1 replication in vivo.