Differential Expression of Glut 1 mRNA and Protein Levels Correlates with Increased Sensitivity to the Glyco-Conjugated Nitric Oxide Donor (2-glu-SNAP) in Different Tumor Cell Types

Abstract

Nitric Oxide (NO) releasing agents can serve as potent cytotoxic agents. However at present there are no effective ways to target delivery of NO donors like S-nitroso-N-acetyl-penicillamine (SNAP). SNAP conjugated to glucose (2-gluSNAP) can be readily transported across the membrane by GLUT 1 transporters. Therefore, sensitivity of cells to 2-gluSNAP may depend on glucose-transporter GLUT 1. We evaluated the cytotoxicity of SNAP and 2-gluSNAP on a GLUT 1 rich glioblastoma cell line T98G and GLUT 1 deficient osteoblastoma cell line 143B andits mitochondria-deficient variant ρ° (cell line 206). The cytotoxity of SNAP and 2-gluSNAP was assessed by clonogenic assay performed in the above cell lines in vitro. Immunoblotting and semi-quantitative real-time PCR assays were used to evaluate the expression of GLUT 1 transporter at protein and mRNA levels. The glioblastoma cell line T98G was more sensitive to 2-gluSNAP than unconjugated SNAP. SNAP and 2-gluSNAP affected the osteosarcoma cell lines 143B and ρ° poorly. Immunoblot analysis detected GLUT 1 protein in T98G cells and not in 143B or ρ°. There was about a 10-fold difference in GLUT 1 mRNA level in T98G cells compared to 143B and ρ° cell lines. This is consistent with our cytotoxicity studies and immunoblot analysis. Our results give credence to our hypothesis that the sensitivity to NO donors can be increased by glyco-conjugation and the cytotoxicity of the glyco-conjugated NO donors depends on the expression of GLUT 1 mRNA and protein.