Midkine secretion protects Hep3B cells from cadmium induced cellular damage

Midkine inhibition enhances anti-PD-1 immunotherapy in sorafenib-treated hepatocellular carcinoma via preventing immunosuppressive MDSCs infiltration

Sorafenib, a multiple-target tyrosine kinase inhibitor, is the standard of care for patients with advanced hepatocellular carcinoma (HCC), but provides limited benefits. Emerging evidences suggest that prolonged sorafenib treatment induces an immunosuppressive HCC microenvironment, but the underling mechanism is undetermined. In the present study, the potential function of midkine, a heparin-binding growth factor/cytokine, was evaluated in sorafenib-treated HCC tumors. Infiltrating immune cells of orthotopic HCC tumors were measured by flow cytometry. Differentially expressed genes in sorafenib-treated HCC tumors were evaluated by transcriptome RNA sequencing. The potential function of midkine were evaluated by western blot, T cell suppression assay, immunohistochemistry (IHC) staining and tumor xenograft model. We found that sorafenib treatment increased intratumoral hypoxia and altered HCC microenvironment towards an immune-resistant state in orthotopic HCC tumors. Sorafenib treatment promoted midkine expression and secretion by HCC cells. Moreover, forced midkine expression stimulated immunosuppressive myeloid-derived suppressor cells (MDSCs) accumulation in HCC microenvironment, while knockdown of midkine exhibited opposite effects. Furthermore, midkine overexpression promoted CD11b⁺CD33⁺HLA-DR^- MDSCs expansion from human PBMCs, while midkine depletion suppressed this effect. PD-1 blockade showed no obvious inhibition on tumor growth of sorafenib-treated HCC tumors, but the inhibitory effect was greatly enhanced by midkine knockdown. Besides, midkine overexpression promoted multiple pathways activation and IL-10 production by MDSCs. Our data elucidated a novel role of midkine in the immunosuppressive microenvironment of sorafenib-treated HCC tumors. Mikdine might be a potential target for the combination of anti-PD-1 immunotherapy in HCC patients.

PBMCs gene expression signature of advanced cirrhosis with high risk for clinically significant portal hypertension in HIV/HCV coinfected patients: A cross-control study

BACKGROUND

Patients with advanced cirrhosis are at high risk of developing clinically significant portal hypertension (CSPH). We analyzed the gene expression profile of peripheral blood mononuclear cells (PBMCs) from HIV/HCV coinfected patients to identify a gene expression signature of advanced cirrhosis with high risk for CSPH.

METHODS

We conducted a cross-sectional study on 68 patients. Liver stiffness measurement (LSM) was used to stratify patients into < 12.5 kPa (no cirrhosis, n = 19), 12.5 - 24.9 kPa (cirrhosis, n = 20), and ≥ 25 kPa (advanced cirrhosis with high risk for CSPH, n = 29). Besides, we further evaluated LSM < 25 kPa (n = 39) vs. ≥ 25 kPa (n = 29). Total RNA was extracted from PBMCs, and poly(A) RNA sequencing was performed. Two significant differentially expressed (SDE) transcripts were validated by quantitative PCR in a different cohort (n = 46).

RESULTS

We found 60 SDE transcripts between patients with LSM < 12.5 kPa and ≥ 25 kPa. Partial least squares discriminant analysis showed that those 60 SDE transcripts collectively discriminated LSM ≥ 25 kPa, with an area under the receiver operating characteristic curve (AUROC) of 0.84. Eight genes had an AUROC ≥ 0.75 for LSM ≥ 25 kPa: five were positively associated with LSM values (SCAMP1, ABHD17B, GPR146, GTF2A1, and TMEM64), while three were inversely associated (ZFHX2-AS1, MDK, and STAG3L2). We validated the two SDE transcripts with the highest discrimination capacity in a different cohort, finding significant differences between < 25 kPa and ≥ 25 kPa (MDK (p = 0.006) and STAG3L2 (p = 0.021)).

CONCLUSIONS

A gene expression signature of 60 transcripts was associated with advanced cirrhosis with high risk for CSPH in HIV/HCV coinfected patients.

Midkine promotes metastasis and therapeutic resistance via mTOR/RPS6 in uveal melanoma

Uveal melanoma is a rare form of melanoma that originates in the eye, exerts widespread therapeutic resistance and displays an inherent propensity for hepatic metastases. Since metastatic disease is characterized by poor survival, there is an unmet clinical need to identify new therapeutic targets in uveal melanoma. Here, we show that the pleiotropic cytokine midkine is expressed in uveal melanoma. Midkine expression in primary uveal melanoma significantly correlates with poor survival and is elevated in patients that develop metastatic disease. Monosomy 3 and histopathological staging parameters are associated with midkine expression. In addition, we demonstrate that midkine promotes survival, migration across a barrier of hepatic sinusoid endothelial cells and resistance to AKT/mTOR inhibition. Furthermore, midkine is secreted and mediates mTOR activation by maintaining phosphorylation of the mTOR target RPS6 in uveal melanoma cells. Therefore, midkine is identified as a uveal melanoma cell survival factor that drives metastasis and therapeutic resistance, and could be exploited as a biomarker as well as a new therapeutic target. Implications: Midkine is identified as a survival factor that drives liver metastasis and therapeutic resistance in melanoma of the eye.

Shedding more light on the role of Midkine in hepatocellular carcinoma: New perspectives on diagnosis and therapy

One of the most common malignant tumors is hepatocellular carcinoma (HCC). Progression of HCC mainly results from highly complex molecular and pathological pathways. Midkine (MDK) is a growth factor that impacts viability, migration, and other cell activities. Since MDK has been involved in the inflammatory responses, it has been claimed that MDK has a crucial role in HCC. MDK acts as an anti-apoptotic factor, which mediates tumor cell viability. In addition, MDK blocks anoikis to promote metastasis. There is also evidence that MDK is involved in angiogenesis. It has been shown that the application of anti-MDK approaches might be promising in the treatment of HCC. Besides, due to the elevated expression in HCC, MDK has been proposed as a biomarker in the prognosis and diagnosis of HCC. In this review, we will discuss the role of MDK in HCC. It is hoped that the development of new strategies concerning MDK-based therapies will be promising in HCC management.

Notch signaling activated by replication stress-induced expression of midkine drives epithelial-mesenchymal transition and chemoresistance in pancreatic cancer

The incidence of pancreatic ductal adenocarcinoma (PDAC) nearly equals its mortality rate, partly because most PDACs are intrinsically chemoresistant and thus largely untreatable. It was found recently that chemoresistant PDAC cells overexpress the Notch-2 receptor and have undergone epithelial-mesenchymal transition (EMT). In this study, we show that these two phenotypes are interrelated by expression of Midkine (MK), a heparin-binding growth factor that is widely overexpressed in chemoresistant PDAC. Gemcitabine, the front-line chemotherapy used in PDAC treatment, induced MK expression in a dose-dependent manner, and its RNAi-mediated depletion was associated with sensitization to gemcitabine treatment. We identified an interaction between the Notch-2 receptor and MK in PDAC cells. MK-Notch-2 interaction activated Notch signaling, induced EMT, upregulated NF-κB, and increased chemoresistance. Taken together, our findings define an important pathway of chemoresistance in PDAC and suggest novel strategies for its clinical attack.

Role of midkine in cadmium-induced liver, heart and kidney damage

Accumulation of the widespread environmental toxin cadmium (Cd) in tissues results in toxicity. Cd, which can induce a broad spectrum of biological effects, is a toxic substance and is associated with inflammation and apoptosis. Midkine (MK) has fibrinolytic, antiapoptotic, transforming, angiogenetic and chemotactic activities. After Cd toxicity, we found increased MK expression in liver cells in an in vitro cell culture model. The aim of this study was to determine the possibility of relationship between tissue MK expression levels, tumor necrosis factor α(TNF-α) levels and apoptosis in a chronic Cd toxicity model in rats. Male Wistar rats were exposed to Cd at the dose of 15 parts per million (ppm) for 8 weeks. MK levels were measured in kidney, heart and liver tissue by enzyme-linked-immunosorbent assay (ELISA). MK messenger RNA (mRNA) expression was evaluated by RT-PCR. Tissue apoptosis level was evaluated with tissue caspase-3 activity levels. Accumulation of Cd in liver is higher than the kidney and heart. Cd-treated rats had significantly higher tissue TNF-α and caspase-3 levels when compared with the control rats (p < 0.001). MK mRNA and protein levels were also significantly upregulated in the Cd-treated group (p < 0.05, p < 0.001, respectively). When compared with apoptosis in tissues, it was more prominent in the liver than kidney and heart. MK level is found increased 3, 1.7 and 1.3× folds in liver, kidney and heart, respectively. Our results showed that chronic Cd administration induces inflammation and apoptosis in rat liver, kidney and heart. MK involved in damage mechanisms of Cd-induced tissues. Further studies will show the underlying mechanism of increased MK expression in Cd toxicity.

Enhancement of vinorelbine-induced cytotoxicity and apoptosis by clomipramine and lithium chloride in human neuroblastoma cancer cell line SH-SY5Y

The aim of this work is to investigate whether clomipramine (CIM) and lithium chloride (LiCl) potentiate the cytotoxicity of vinorelbine (VNR) on SH-SY5Y human neuroblastoma cells in vitro and whether midkine (MK) can be a resistance factor for these treatments. Four groups of experiments were performed for 96 h using both monolayer and spheroid cultures of SH-SY5Y cells: (1) control group, (2) singly applied VNR, CIM, and LiCl, (3) VNR with CIM, and (4) VNR with LiCl. Their effects on monolayer and spheroid cultures were determined by evaluating cell proliferation, bromodeoxyuridine labeling index (BrdU-LI), apoptosis, cyclic adenosine monophosphate (cAMP) and midkine levels, colony-forming efficiency, spheroid size, and ultrastructure. In comparison with the control group, single and combination drug treatments significantly reduced the proliferation index (PI) for 96 h. The most potent reduction of PI was observed with VNR in combination with CIM and LiCl for all time intervals. VNR with CIM and LiCl seemed to be ineffective in reducing BrdU-LI of both monolayer cell and spheroid cultures, spheroid size, and cAMP level. VNR with LiCl increased apoptosis at 24 h, however VNR with CIM increased apoptosis at 96 h. VNR was the most potent drug in inhibiting colony-forming efficiency. The combination of VNR with CIM was the most potent in reducing midkine levels among all groups. Interestingly, the combination of VNR with LiCl led to both nuclear membrane breakdown and disappearance of the cellular membranes inside the spheroids. Both CIM and LiCl seemed to potentiate VNR-induced cytotoxicity, and MK was not a resistance factor for VNR, LiCl, and CIM.