EPCR promotes MGC803 human gastric cancer cell tumor angiogenesis in vitro through activating ERK1/2 and AKT in a PAR1-dependent manner

The endothelial cell protein C receptor (EPCR) serves a key role in activated protein C (APC)-mediated cytoprotective effects in endothelial cells, and is involved in the development of certain types of human cancer. To the best of our knowledge, the present study is the first to demonstrate that EPCR may exert effects on gastric cancer angiogenesis in vitro. To detect microvessel density (MVD), the microvascular endothelial cells were stained for cluster of differentiation (CD)31 and CD34 in 61 cases of surgical resection of gastric carcinoma tissues, and the association between the expression of EPCR protein and MVD was analyzed. In addition, to analyze the effect of EPCR expressed by gastric cancer cells on the proliferation, migration and angiogenic abilities of endothelial cells, human umbilical vein endothelial cells (HUVECs) were cultured with tumor-conditioned medium derived from EPCR knockdown or protease-activated receptor 1 (PAR1)-blocked MGC803 gastric cancer cells. A CCK-8 assay was used to assess the proliferation ability of the HUVECs. A Transwell assay was performed to assess the migration ability of the HUVECs and a Matrigel-based tube formation assay was used to assess the angiogenic activity of the HUVECs. The results demonstrated that the expression of EPCR was correlated with the MVD of gastric cancer tissues. When cultured with tumor-conditioned medium derived from EPCR knockdown or PAR1-blocked MGC803 cells, the proliferation, migration and tubules formation abilities of HUVECs were markedly inhibited markedly. The expression of phosphorylated (p)-extracellular signal regulated kinase 1/2, p-protein kinase B (AKT; s473) and p-AKT (T308) in the HUVECs was decreased. In addition, EPCR knockdown inhibited PAR1 activation in the MGC803 cells. These results indicated that the expression of EPCR in gastric cancer cell line MGC803 contributes to tumor angiogenesis in vitro by activating ERK1/2 and AKT, and that this effect of EPCR is dependent on PAR1 activation.

[The role of extracellular signal regulated kinase 1/2 in mediating osteodifferentiation of human periodontal ligament cells induced by cyclic stretch]

OBJECTIVE

This study aimed to investigate the mechanism of cyclic stretch that promotesthe osteogenic differentiation of human periodontal ligament cells (hPDLCs) through the mediation of extracellular-signal-regulated kinase 1/2 (ERK1/2).

METHODS

hPDLCs were isolated through the explant method and cultured in vitro. hPDLCs were mechanically stimulated by a multi-channel cell-stress-loading system for 1, 3, 6, 12, and 24 h. The magnitude of stretch was 10% deformation, and the frequency was 0.5 Hz. Nonloaded cells were used as control group. ERK1/2 activation was blocked by U0126, a specific ERK1/2 pathway inhibitor. Additionally, hPDLCs were transfected with adenoviral vector encoding dominant negative ERK1/2 (DN-ERK1/2) to continuouslyinhibit ERK1/2 activation. The mRNA and protein levels of target geneswere detected through real-time polymerase chain reaction and Western blot.

RESULTS

Cyclic stretching promoted the expression of ERK1/2, osteocalcin (OCN) mRNA, and bone sialoprotein (BSP) mRNA. The expression of runt-related transcription factor (Runx) 2 protein and mRNA also increased at 3 and 6 h of cyclic stretching. The inhibition of ERK1/2 by U0126 and DN-ERK1/2 suppressed the expressionof Runx2 mRNA, OCN mRNA, BSP mRNA, Runx 2 protein, and p-ERK1/2 protein relative to that in stretched cells without the ERK1/2 inhibitor.

CONCLUSIONS

ERK1/2 is a critical molecule in the mediation ofthe osteogenic differentiation of hPDLCs under mechanical stimulation. ERK1/2 activation induced the elevation of Runx2 protein levels, which may be involved in the stretch-induced expressions of OCN and BSP.

Activation of the extracellular signal regulated kinase (ERK) pathway in human melanoma

BACKGROUND

Several studies suggest that melanoma may be resistant to treatment because of resistance to apoptosis and that this may be the result of activation of the extracellular signal regulated kinase (ERK1/2) pathway.

AIMS

To test this hypothesis by examining the expression of ERK1/2 and its activated form in histological sections of melanoma and its relation to known prognostic features of the disease.

MATERIALS/METHODS

Immunohistochemistry with antibodies to ERK1/2 and phosphorylated ERK (p-ERK) was performed on formalin fixed sections from 42 primary melanomas, 38 metastases, and 20 naevi. Fourteen of the primary melanomas were in the radial and 28 in the vertical growth phase.

RESULTS

ERK1/2 was widely expressed (100%) in all the (pigmented) lesions studied. p-ERK1/2 expression was much lower in compound (32.4%) and dysplastic (54.5%) naevi than in primary melanoma (nodular 78.8%, superficial spreading 67%) and subcutaneous metastases (76.3%). p-ERK expression was much lower in lymph node metastases (48.5%), suggesting that the microenvironment may influence the activation of ERK. There was a (non-significant) trend for p-ERK expression to be higher in thick (>1.0 mm) versus thin (< or =1.0 mm) melanoma (p = 0.23). There was a trend for overall survival to be related to p-ERK expression in patients with melanoma over 1 mm in thickness.

CONCLUSIONS

Expression of activated ERK1/2 in melanocytic lesions appears to be related to malignant potential so that activation of ERK1/2 may be important in melanoma progression. These results provide important histological support for the proposal that inhibition of this signalling pathway may be useful in treatment of melanoma.