Antitumor effects of human ribonuclease inhibitor gene transfected on B16 melanoma cells.

Human ribonuclease inhibitor (RI) is a cytoplasmic acidic protein. The experiment demonstrated that it might effectively inhibit tumor-induced angiogenesis and inhibit tumor growth. Ribonuclease inhibitor is constructed almost entirely of leucine-rich repeats, which might be involved in unknown biological effects besides inhibiting RNase A and angiogenin activities. The exact molecular mechanism of antitumor on ribonuclease inhibitor remains unclear so far. In order to further understand the function of ribonuclease inhibitor and investigate the relationship with tumor growth, our study established a transfection of human ribonuclease inhibitor cDNA into the murine B16 cells by the retroviral packaging cell line PA317. The cell line transfected with a stably high expression of ribonuclease inhibitor was identified. We found that the transfected ribonuclease inhibitor could obviously inhibit cell proliferation, regulate cell cycle and induce cell apoptosis in vitro. Mice that were injected with the B16 cells transfected RI cDNA showed a significant inhibition of the tumor growth with lighter tumor weight, lower density of microvessels, longer latent periods, and survival time than those in the other two control groups. In conclusion, the results reveal the novel mechanism that antitumor effect of ribonuclease inhibitor is also associated with inducing apoptosis, regulating cell cycle and inhibiting proliferation besides antiangiogenesis. These results suggest that ribonuclease inhibitor might be a candidate of tumor suppressor gene in some tissues. RI could become a target gene for gene therapy. Our study may be of biological and clinical importance.

[Anti-oxidative effect of ribonuclease inhibitor by site-directed mutagenesis and expression in Pichia pastoris].

Human placental ribonuclease inhibitor is an acidic protein of Mr approximately 50 kDa with unusually high contents of leucine and cysteine. It is a cytosolic protein that protects cells from the adventitious invasion of pancreatic-type ribonuclease. HRI has 32 cysteine residues, and the oxidative formation of disulfide bonds from those cysteine residues is a rapid cooperative process that inactivates HRI. The most proximal cysteine residues in native HRI are two pairs that are adjacent in sequence. In the present paper, two molecules of alanine to substitute for cys328/cys329 were performed by site-directed mutagenesis. The site-mutated RI cDNA was constructed into plasmid pPIC9K, and then transformed Pichia pastoris GS115 by electroporation. After colony screening , the bacterium was cultured and the product was purified with affinity chromatography. The affinity of the recombinant human RI with double site mutation was examined for RNase A and its anti-oxidative effect. The results indicated that there was no much change in the affinity for RNase A detected when compared with the wild type of RI. But the capacity of anti-oxidative effect was increased by 7-9 times. The enhance in anti-oxidative effect might be the reason for preventing the formation of disulfide bond between cys328 and cys329 and the three dimensional structure of RI was thereby maintained.

The antioxidant effects of ribonuclease inhibitor.

Ribonuclease inhibitor (RI) is an acidic cytosolic glycoprotein with molecular weight of about 50 kDa, which contains 32 cysteine residues. It is possibly that RI may have antioxidant effect by thiol-disulfide exchange reaction. We studied the effects of RI over-expression on the rat glial cell line C6 injured with H2O2. The transfected C6 cells with RI cDNA (C6') had higher viability, less LDH leakage and MDA contents, but more GSH contents compare that in the control C6 cells. In transfected C6 cells, the activities of CAT and GST were higher than that in the control C6 cells. Without H202 stress, the activities of CAT and GST in the C6' cells were 1.73 and 3.62 times that in the control C6 cells, respectively; With 1.00 mmol/L H2O2 stress, the activities of CATand GSTin the C6' cells were 3.38 and 2.11 times that in the C6 cells, respectively. These results suggest that the over-expression RI has antioxidant activity and it is able to protect cells from per-oxidative injuries. Moreover, we investigated whether RI has a protective role against mouse hepatic damage in vivo. The mice pretreated with different doses of human RI were injected by CC14. The results show that the SOD activities of therapy groups were significantly higher than that of the control group (p < 0.01), while the contents of MOD and activities of ALT and AST in blood were remarkably lower than that of the control group (p < 0.01). Pathological examination shows that the degree of damage was alleviated with RI therapy. These results suggest that RI has the protective role against mouse hepatic damage induced by CC14. The anti-oxidative effects of RI may play an important role in cell protection from per-oxidative injuries.

[Inhibitory effect of ginsenoside-Rg3 on lung metastasis of mouse melanoma transfected with ribonuclease inhibitor].

OBJECTIVE: To investigate the effect of ginsenoside-Rg3 on lung metastasis of ribonuclease inhibitor (RI) gene-transfected mouse B16 melanoma. METHODS: C57BL/6 mice were iv injected with parental or RI-transfected B16 melanoma cells. Lung metastasis was assessed by the number of surface tumor nodules. Mice were divided into 6 groups. Group I, II and III of mice were given parental, mock-transfected and RI-transfected B16 melanoma cells, respectively while in group IV, V and VI, Rg3 (1.5 mg/kg, iv q.o.d. x 10) was given to mice bearing parental, mock-transfected and RI-transfected B16 melanoma, respectively. Micovessel density (MVD) of the lung metastatic tumor was assessed by immunohistochemical staining of factor VIII-R expression. RESULTS: The number of tumor nodules was significantly decreased in mice injected with RI-transfected B16 melanoma (Gp III, compared to Gp I and II). Rg3 treatment per se could also decrease the number of lung tumor nodules but to a lesser extent (Gp IV and V compared to Gp III). However, Rg3 synergized with RI transfection resulting in most significant inhibition of lung metastasis (Gp VI). Mice in Gp I and II died within 26 days of the experiment, whereas all the mice in Gp VI were alive during the observation period of one and one half month. MVD was significantly decreased in the lung tumor nodules in mice injected with RI-transfected B16 melanoma. It was further decreased when additional Rg3 was given (Gp VI). CONCLUSION: Transfection of ribonuclease inhibitor gene significantly reduces the metastatic potential of B16 melanoma. Ginsenoside-Rg3 has a synergistic effect.

[Secretory expression vector V-pLNCX-s-hri inhibits the growth of mouse B16 melanoma].

BACKGROUND AND OBJECTIVE: Human ribonuclease inhibitor (hRI) extracted and purified from human placenta has been shown to remarkably inhibit some solid tumors in mice. This study was to construct V-pLNCX-s-hri, a secretory expression vector, and explore its inhibition effects on the growth of mouse B16 melanoma cells. METHODS: The hRI gene sequence conjugated with the synthesized signal peptide of mouse IgG was cloned into the retroviral vector V-pLNCX to construct V-pLNCX-s-hri. The PA317 cells were used for viral package and NIH3T3 cells were employed to determine the viral titer. The expression of hRI gene was detected by RT-PCR and Western blot. The content of RI was determined by enzyme-linked immunoabsorption assay (ELISA). The model of B16 melanoma-carrying mouse was established and received different treatments. The tumor weight and microvessle density (MVD) were assessed. Normal saline (NS), V-pLNCX, and V-pLNCX-hri were used as controls. RESULTS: The infection efficiency of V-pLNCX-s-hri on cultured B16 cells reached 38.5%. mRNA and protein levels of hRI were detected in B16 cells infected by V-pLNCX-s-hri. The hRI content in the supernatant of infected B16 cells reached 0.228 microg/mL. The hRI content in the peripheral blood of experimental mice was significantly higher in the V-pLNCX-s-hri group (0.249 microg/mL) than in the NS group (0.035 microg/mL), V-pLNCX group (0.028 microg/mL) and V-pLNCX-hri group (0.169 microg/mL) (P<0.01). The tumor weight and MVD were significantly lower in the V-pLNCX-s-hri group compared with those in the NS, V-pLNCX and V-pLNCX-hri groups (P>0.01). CONCLUSIONS: V-pLNCX-s-hri can effectively infect B16 cells and induce high expression of hRI. V-pLNCX-s-hri is superior to V-pLNCX-hri in inhibiting the growth of B16 cells.

[Transfection and expression of hRI gene on human umbilical blood stem cells and gene therapy for mouse melanoma].

In order to explore the transfection and expression of hRI gene on human umbilical blood stem cells, and observe it's effect on the tumor growth. After enriching human umbilical cord blood CD34+ cells with a high-gradient magnetic cell sorting system (MACS), transfected them with supernatant of retrovirus containing human Ribonuclease inhibitor (hRI) cDNA. Hematopoietic progenitor clonogenic assay and PCR were used to evaluate transfection efficiency, and Western-blot and immune fluorescence were used to evaluate the expression quantity of hRI gene after transfection. Observe the effect of RI on the growth of melonoma in B16C57BL mice. The results showed that human umbilical blood CD34+ cells were highly purified by MACS, which made the purity of human umbilical blood CD34+ cells average 96.15%. hRI can be transfected on umbilical blood CD34+ cells, and the transfection efficiency was 35%. The positive expression of hRI gene on transfected CD34+ cells is identified by Western-blot and immune fluorescence assay. Mice injected with transfected CD34+ cells show a significant restraint of the tumor growth, a lower efficiency of tumor formation, a lower weight of the tumor and a longer incubation period of tumor formation with respect to the control groups. The results demonstrated the capacity of RI to inhibited the tumor growth by blocking the vasculature in tumor.

[Analysis of gene expression of ribonuclease inhibitor in human breast cancer tissue].

BACKGROUND & OBJECTIVE: Ribonuclease inhibitor (RI), which is rich in human placenta, is a multi-functional acidic glycoprotein. Our previous studies showed that the growth of some solid tumors (S180 sarcoma, Ca761 breast cancer, and H22 hepatoma) could be significantly inhibited by RI extracted and purified from human placenta. This study was designed to observe the change of RI gene expression in human breast cancer tissue. METHODS: The expression level of RI mRNA was determined by reverse transcription-polymerase chain reaction (RT-PCR) and capillary electrophoresis (CE). The RI content was determined by Western blot analysis. RESULTS: The electrophoretic stripes of the RT-PCR products of the breast cancer tissues were narrower and the plaques of Western blot of the breast cancer tissues were smaller compared with the control breast tissues. The peak altitude and width of capillary electrophoretic absorptive curve of the RT-PCR product of the breast cancer tissue were clearly smaller than that of the control breast tissue. The capillary electrophoresis integral values of the absorptive peak areas of RT-PCR product of the breast cancer tissue and the control breast tissue were (3.320+/-0.365)x10(6) and (4.385+/-0.880)x10(6), respectively. The comparison between two groups reveals a remarkably difference (P< 0.01). CONCLUSION: The gene expression of RI is clearly down-regulated in human breast cancer tissue that the RI mRNA level is remarkably lower and RI content also reduces significantly in human breast cancer tissue.

Effects of DNA methylation inhibitor on down-regulation of ribonuclease inhibitor expression in cancer cell lines.

BACKGROUND & OBJECTIVE: Human ribonuclease inhibitor (RI) could effectively block angiogenin-induced angiogenesis, and inhibit growth of transplant solid tumors in animals. However, its exact molecular mechanism of antitumor has not been totally ascertained. Many tumor suppressor genes occur loss of expression by aberrant methylation in promoter region. Demethylation, treated with methylation inhibitor 5-aza-2'-deoxycytidine (5-Aza-CdR),can restore the gene expression. To further explore functions of RI, and investigate relationship between RI and tumorigenesis, the study was designed to explore effects of 5-Aza-CdR on expression of RI in cancer cell lines. METHODS: Human breast cancer cell line MCF-7, human gastric cancer cell line BGC-823, human prostate cancer cell line DU-145, and human colon cancer cell line HT-29 were treated with 5-Aza-CdR. Expression of RI was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and immunocytochemistry. RESULTS: Expression of RI significantly elevated by 5-Aza-CdR at both mRNA and protein level in MCF-7, BGC-823, and DU-145 cells (P< 0.01). Compared with control cells, mRNA levels of RI in MCF-7, BGC-823, and DU-145 cells treated with 5-Aza-CdR were increased by percentages of 37.2%, 46.0%, and 32.4%, respectively; protein levels of RI were increased by percentages of 26.4%, 20.9%, and 24.4%, respectively; but no obvious change observed in HT-29 cells. CONCLUSION: RI gene may be involved in tumorigenesis of gastric, prostate, and breast cancer.

[Preparation and purification of the antibody against ribonuclease inhibitor].

AIM: To prepare and purify the antibody against ribonuclease inhibitor(RI). METHODS: RI was extracted from human placenta and purified by affinity chromatography. Rabbits anti-RI antibody was obtained after immunization and then purified through rProtein A Sepharose Fast Flow chromatography column. The characters of the antibody was identified by SDS-PAGE, ELISA and Western blot. RESULTS: An anti-RI antibody was obtained and purified. SDS-PAGE analysis showed that the purified anti-RI antibody has high purity. The results of Western blot and ELISA indicated that anti-RI antibody had high specificity and good stability. CONCLUSION: The anti-RI antibody with high titer, high specificity and good stability has been acquired, which lays the foundation for further research on RI.