Experimental Study of Yeast RNA Preparation as a Possible Radioprotective Agent for Radiotherapy of Malignant Tumors.

We studied radioprotective effects of a preparation based on yeast RNA and its influence on therapeutic efficiency of ionizing radiation against transplanted tumors. Parenteral administration of yeast RNA preparation to mice in a dose of 10 mg 1 h prior to exposure to ionizing γ-radiation (137Cs) in a lethal dose (LD80/30) increased 30-day survival by 66%; by day 80, 80% of animals survived (vs. 2.5% in the control). Whole-body exposure to ionizing γ-radiation in a dose of 7 Gy significantly increased the mean lifespan of mice with experimental lung metastases or intraperitoneally transplanted leukemia L-1210 by 42 and 20.8%, respectively. RNA preparation injected to the mice with tumors 1 h before irradiation did not affect the therapeutic efficiency of ionizing radiation or significantly potentiated it (in mice with transplanted leukemia L-1210). These results suggest that yeast RNA preparation protects healthy tissues during radiotherapy of malignant tumors.

Isolation and Characterization of a Phaseolus vulgaris Trypsin Inhibitor with Antiproliferative Activity on Leukemia and Lymphoma Cells.

A 17.5-kDa trypsin inhibitor was purified from Phaseolus vulgaris cv. "gold bean" with an isolation protocol including ion exchange chromatography on DEAE-cellulose (Diethylaminoethyl-cellulose), affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-sepharose (Sulfopropyl-sepharose), and gel filtration by FPLC (Fast protein liquid chromatography) on Superdex 75. It dose-dependently inhibited trypsin with an IC50 value of 0.4 µM, and this activity was reduced in the presence of dithiothreitol in a dose- and time-dependent manner, signifying the importance of the disulfide linkage to the activity. It inhibited [methyl-³H] thymidine incorporation by leukemia L1210 cells and lymphoma MBL2 cells with an IC50 value of 2.3 µM and 2.5 µM, respectively. The inhibitor had no effect on fungal growth and the activities of various viral enzymes when tested up to 100 µM.

PpIX induces mitochondria-related apoptosis in murine leukemia L1210 cells.

CONTEXT: Protoporphyrin IX (PpIX), a well-known sensitizer that can enhance laser light or ultrasound induced cytotoxicity in photodynamic and sonodynamic therapy. However, PpIX alone could effectively cause anti-tumor effect and the underlying mechanisms are rarely been reported. Therefore, this study was to investigate the possible mechanism by which PpIX revealed anti-proliferative effect on murine leukemia L1210 cells. MATERIALS AND METHODS: The accumulation of PpIX in L1210 cells and normal peripheral blood mononuclear cells (PBMCs) was evaluated with flow cytometry. The subcellular localization of PpIX and apoptosis-inducing factor (AIF) translocation were determined by confocal microscope. The cell viability was examined by MTT assay. Annexin V-PE/7-AAD and DAPI staining were used to detect apoptotic cells. The mitochondrial membrane potential (MMP) changes were tested by rhodamine123 staining. DNA damage was measured by comet assay. RESULTS: PpIX preferentially accumulated in L1210 cells compared to PBMCs and PpIX mainly located in the mitochondria of L1210 cells. PpIX at a concentration of 1 µg/ml or above exerted significant anti-tumor effect and the cell viability loss presented PpIX dose-dependent manner. Typical apoptotic features such as chromatin condensation were observed by DAPI staining. Annexin V-PE/7-AAD analysis showed 5 µg/ml PpIX could induce about 24% cell apoptosis, which was inhibited by cyclosporin A (CsA), an inhibitor of mitochondrial permeability transition pore. In addition, the PpIX caused MMP loss, AIF translocation to nucleus and serious DNA damage were also suppressed by CsA. CONCLUSION: The results indicate mitochondria-dependent apoptosis were involved in PpIX caused cell damage on L1210 cells.