[Overexpression of the receptor tyrosine kinase EphA2 in choroidal melanoma: correlation with vesculogenic mimicry and prognosis].

OBJECTIVE: To study the correlation of EphA2 protein expression with vesculogenic mimicry (VM), clinicopathological characteristics and prognosis in choroidal melanoma (CM). METHODS: It was a retrospective case series study. Between January 1992 and December 2005, 56 cases of human CM with clinicopathologic data from the Second Hospital of Tianjin Medical University were studied. HE stainings were performed to observe the microcirculation patterns in tumor tissue specimens. VM was found in 26 of the 56 cases using CD31/periodic acid-Schiff (PAS) double staining and transelectron microscopy. All cases were divided into two groups: VM-positive and VM-negative. Immunohistochemical staining was performed on paraffin sections of the 56 cases of CM specimens to investigate the expression of EphA2. According to tumor cells positive rate and staining intensity of the results of evaluation, the specimens were divided into low expression and high expression groups.χ(2)-test and t-test were used to analyzed the enumeration data and measurement data, respectively. Survival analysis was used to further elucidate its correlation with clinicopathological characteristics, VM and prognosis. Cox proportional hazard model was used to analyzed the influence factors of prognosis. RESULTS: VM channels were found in 26 of the 56 CM cases and VM-negative 30 cases. VM-positivity was related to cell type, tumor size and recurrence and metastasis, and the differences were statistically significant (χ(2) = 4.612, 5.346, 5.213; P = 0.036, 0.021, 0.027). The results showed that EphA2 was up-regulated in the VM-positive group compared with the group of VM-negative group. The positive rates of EphA2 expression in the VM-positive group and VM-negative group were 92.3% (25/26) and 70.0% (21/30), respectively, with a significant difference between the two groups (t = 2.247, P = 0.009). The EphA2 protein was expressed in epithelioid (10/12), mixed (11/15) and spindle (41.40%) cell types, with a significant difference among these histological types (χ(2) = 6.513, P = 0.010). The expression rate of EphA2 protein were significantly higher in large (54.55%, 18/33) than small (45.45%, 15/33) tumors, and the expression of EphA2 in metastatic and recurrence patients (10/11) were significantly higher compared with controls (31.11%, 14/45) (χ(2) = 4.556, 8.211;P = 0.016, 0.005). Kaplan-Meier survival analysis showed the presence of VM resulted in a poor prognosis (t = 9.263, P = 0.000). The Cox proportional hazards model indicated that the EphA2 overexpression and the presence of VM were independent predictors of a poor prognosis (χ(2) = 12.041, P = 0.001). Moreover, there was a significant positive correlation between them (r = 0.412, P < 0.05). CONCLUSION: The results of this study demonstrate that EphA2 may play a critical role in the formation process of VM in CM, implicating EphA2 as a valuable marker for the prediction of recurrence, metastasis and prognosis in CM patients.

MicroRNA-34a targets notch1 and inhibits cell proliferation in glioblastoma multiforme.

Aberrant expression of microRNAs (miRNAs) has been implicated in cancer initiation and progression. In this study, we found that microRNA-34a (miR-34a) is significantly downregulated in glioblastoma multiforme (GBM) specimens compared with normal brain tissues. Growth curve and colony formation assays revealed that miR-34a suppresses proliferation of U373MG and SHG44 glioblastoma cells. Overexpression of miR-34a could induce apoptosis of glioblastoma cells. Also, we identified notch1 as a direct target gene of miR-34a. Knockdown of notch1 showed similar cellular functions as overexpression of miR-34a both in vitro and in vivo. Collectively, our findings show that miR-34a is downregulated in GBM cells and inhibits GBM growth by targeting notch1.

Inhibition of tumor growth and vasculogenic mimicry by curcumin through down-regulation of the EphA2/PI3K/MMP pathway in a murine choroidal melanoma model.

This study aims to investigate the underlying mechanism by which curcumin inhibits tumor growth and reduces vasculogenic mimicry (VM) in a murine choroidal melanoma model. Sixty mice were given subretinal injection with B16F10 cells and divided into a treatment and a control group. Curcumin was administered to the treatment group once a day at a dose of 100 mg/kg for 18 days starting at d3 (the day of inoculation is designated as d0); an equivalent volume of poloxamer-F68 was administered to the control group. Immunohistochemical and histochemical double staining were ued to detect the different blood supply patterns. The amounts of epithelial cell kinase (EphA2), phosphatidylinositol-3-kinase (PI3K), and matrixmetalloproteinase-2 and -9 (MMP-2, MMP-9) proteins expressed in the tumor tissue were analyzed using immunohistochemical staining; mRNA levels were measured using real-time PCR analysis. Results indicate that the tumor volume is reduced (P=0.000) and that the numbers of VM (P=0.000), mosaic vessels (P=0.031), and endothelium-dependent vessels (P=0.000) are significantly decreased by curcumin (P=0.001). The expression levels of EphA2, PI3K, MMP-2, and -9 are also lower in the treatment group than in the control group (P=0.001); similarly, mRNA levels in the treatment group are lower than those in the control group (P=0.000). In conclusion, curcumin has the ability to inhibit the growth of engrafted melanoma VM channels through the regulation of vasculogenic factors that could be related to the down-regulation of the EphA2/PI3K/MMPs signaling pathway. Thus, curcumin has the potential of being a clinical inhibitor of VM of choroidal melanoma.

[The mechanisms of microenvironments influence on vasculogenic mimicry between intraocular and subcutaneous melanoma].

OBJECTIVE: To investigate the influence of different microenvironments on melanoma vasculogenic mimicry, invasiveness and metastasis behavior. METHODS: It was an experimental study. Sixty C57BL/6J mice were randomly divided into two groups with 30 mice per group. Melanoma B16 cells were injected into the subretinal space and groin area of mice synchronously. The number of each type of microcirculation pattern was counted. The invasion and metastasis were observed. EphA2, MMP-2 and MMP-9 expression and their mRNA levels were detected by immunohistochemical staining and real time RT-PCR and compared between two groups. RESULTS: Five invasions and six lung metastases were found in the subretinal group while no invasion and metastasis were found in the groin group. The number of VM channels was significantly higher in subretinal group (t = 4. 188, P = 0.000). However, no significant difference of mosaic vessel and endothelium-dependent vessel was observed between two groups (t = 1.473, 1.805; P = 0.146, 0.076, respectively). EphA2, MMP-2 and MMP-9 expression was significantly higher in the subretinal group (data not shown). The mRNA levels of EphA2, MMP-2 and MMP-9 were rather higher in the subretinal tumor (t = 3.642, 8.109, 9.357; P = 0.002, 0.001 and 0.001, respectively). There was a positive association in melanoma cells of the VM between expression of EphA2 (r = 0.412, P = 0.021) but no statistically significant correlation between VM and MMP-2 (P > 0.05), nor between VM and MMP-9. CONCLUSIONS: Different microenvironments affect invasiveness and blood supply patterns of melanoma. Melanoma cells in intraocular microenvironment increased EphA2 expression which induced the formation of VM channels. Moreover, the expression of MMP-2 and MMP-9 in tumor tissue increased to enhance the invasiveness and metastasis behavior.