Constitutive suppression of PRL-3 inhibits invasion and proliferation of gastric cancer cell in vitro and in vivo.

OBJECTIVE: Overexpression of phosphatase of regenerating liver-3 (PRL-3) has been implicated in tumor progression and metastasis of gastric carcinoma. Here we examined what alterations occur in the phenotype of gastric cancer cells in vitro and in vivo when PRL-3 expression is knocked down. METHODS: We constructed a small interfering RNA (siRNA)-expressing vector which stably interfered with PRL-3 expression and was transfected into SH101-P4 cells, which express the highest PRL-3 mRNA levels among 13 gastric cancer cell lines. The new SH101-P4 subclones, in which PRL-3 was stably reduced, were established and their in vitro growth, motility and abilities of liver metastasis from the injected spleen were analyzed in vivo. RESULTS: PRL-3 knockdown effectively suppressed invasion and growth of SH101-P4 cells in vitro. Liver metastasis in vivo was significantly decreased when PRL-3 expression was suppressed. The primary tumor size in the injected spleen tended to be smaller in PRL-3 knockdown clones than in the controls. These findings suggest that PRL-3 expression may contribute not only to the establishment of metastasis but also to the growth of primary foci of human gastric cancer. Therefore, PRL-3 may be one of the target molecules in gastric cancer therapy.

Expression of the enhancer of zeste homolog 2 is correlated with poor prognosis in human gastric cancer.

Overexpression of the enhancer of zeste homolog 2 (EZH2) protein, a known repressor of gene transcription, has been reported to be associated with biological malignancy of prostate cancer and several other cancers. The purpose of this study was to examine the expression of EZH2 and analyze its relationship with the clinicopathological features of human gastric cancers. Expression levels of EZH2 mRNA and protein were examined in 13 gastric cancer cell lines and in 83 surgically removed human gastric cancer tissues. Immunohistochemical analysis of the 83 tissue samples and corresponding non-cancerous gastric mucosa showed that EZH2 was more highly expressed in the cancerous than in the non-cancerous tissues, and the expression levels of EZH2 were highly correlated with tumor size, depth of invasion, vessel invasion, lymph node metastasis and clinical stages. Univariate analysis of survival rate calculated by the Kaplan-Meier method revealed that gastric cancer patients with high-level EZH2 expression had poorer prognosis than those expressing no or low levels of EZH2 (P = 0.0271). These findings suggest that overexpression of EZH2 may contribute to the progression and oncogenesis of human gastric cancers, and thus immunohistochemical study of EZH2 expression may serve as a new biomarker for predicting the prognosis of gastric cancers.

Human serum albumin incorporating synthetic heme: red blood cell substitute without hypertension by nitric oxide scavenging.

The administration of extracellular, hemoglobin-based oxygen carriers often elicits an acute increase in blood pressure by vasoconstriction. This side effect is now recognized to be due to the depletion of nitric oxide (endothelial-derived relaxing factor) by the extravasuated hemoglobins. We have recently found that the administration of a recombinant human serum albumin (rHSA)-based oxygen carrier involving synthetic tetraphenyporphinatoiron(II) derivative (FeP) (rHSA-FeP) does not induce such hypertensive action, because of its low permeability through the vascular endothelium. The heart rate responses after the rHSA-FeP injection were also negligibly small. Visualization of the intestinal microcirculatory changes clearly revealed the widths of the venule and arteriole to be fairly constant. The entirely synthetic rHSA-FeP becomes a promising material as a new type of red blood cell substitute.

Oxygenation of hypoxic region in solid tumor by administration of human serum albumin incorporating synthetic hemes.

Recombinant human serum albumin incorporating synthetic heme (rHSA-FeP) was tested for its ability to increase O(2) tension in the hypoxia of the solid tumor rat model. By the direct administration of the rHSA-FeP solution (10 mL/kg) via the aorta descendens to the ascites hepatoma LY80 tumor on the right femur, the O(2) tension of the hypoxic region immediately increased to 3.45 +/- 1.43 Torr, which corresponds to a 2.4-fold increase compared to that of the baseline value. These high O(2) levels continued for 300 s after the infusion. The rHSA-FeP solution can be utilized not only as a red blood cell substitute but also as an O(2)-carrying medicine for the effective reoxygenation of the hypoxia solid tumor.

Effect of heme structure on O(2)-binding properties of human serum albumin-heme hybrids: intramolecular histidine coordination provides a stable O(2)-adduct complex.

5,10,15,20-Tetrakis[(alpha,alpha,alpha,alpha-o-pivaloylamino)phenyl]porphinatoiron(II) and 5,10,15,20-tetrakis([alpha,alpha,alpha,alpha-o-(1-methylcyclohexanoylamino)]phenyl)porphinatoiron(II) complexes bearing a covalently bound 8-(2-methyl-1-imidazolyl)octanoyloxymethyl or 4-(methyl-L-histidinamido)butanoyloxymethyl side-chain [FeRP(B) series: R = piv or cyc, B = Im or His] have been synthesized. The histidine-bound derivatives [FepivP(His), FecycP(His)] formed five N-coordinated high-spin iron(II) complexes in organic solvents under an N(2) atmosphere and showed large O(2)-binding affinities in comparison to those of the 2-methylimidazole-bound analogues [FepivP(Im), FecycP(Im)] due to the low O(2)-dissociation rate constants. On the contrary, the difference in the fence groups around the O(2)-coordination site (pivaloyl or 1-methylhexanoyl) did not significantly influence to the O(2)-binding parameters. These four porphinatoiron(II)s were efficiently incorporated into recombinant human serum albumin (rHSA), thus providing the synthetic hemoprotein, the albumin-heme hybrid [rHSA-FeRP(B)]. An rHSA host absorbs a maximum of eight FeRP(B) molecules in each case. The obtained rHSA-FeRP(B) can reversibly bind and release O(2) under physiological conditions (in aqueous media, pH 7.3, 37 degrees C) like hemoglobin and myoglobin. As in organic solutions, the difference in the fence groups did not affect their O(2)-binding parameters, but the axial histidine coordination significantly increased the O(2)-binding affinity, which is again ascribed to the low O(2)-dissociation rates. The most remarkable effect of the heme structure appeared in the half-life (tau(1/2)) of the O(2)-adduct complex. The dioxygenated rHSA-FecycP(His) showed an unusually long lifetime (tau(1/2): 25 h at 37 degrees C) which is ca. 13-fold longer than that of rHSA-FepivP(Im).