Rat hypoxanthine phosphoribosyltransferase cDNA cloning and sequence analysis

Low dose Zebularine treatment enhances immunogenicity of tumor cells

STRATEGY

We have investigated how alterations in gene expression induced by the demethylating drug Zebularine affect the immune response tumor cells elicit. The rational has been to treat syngeneic rat colon cancer cells with Zebularine at different concentrations and then use these cells to study gene expression of different genes involved in cancer immunogenicity. Gene expressions were monitored by semi-quantitative PCR and real-time PCR.

RESULTS

Intriguingly there was a large increase in the production of indoleamine 2,3-dioxygenase (IDO) after treatment with 100 microM Zebularine as compared with untreated tumor cells, whereas treatment with 20 microM Zebularine caused a significant decrease of the IDO production. After immunization with syngeneic tumor cells, spleen cells were isolated and restimulated in vitro with irradiated tumor cells. Immune reactivity was measured by proliferation, and production of interferon gamma and interleukin10. The immunogenicity of tumor cells treated in vitro with a low dose of Zebularine increased, whereas it decreased after high dose exposure. The inhibition of immunogenicity by 100 microM Zebularine was shown to be counteracted by the IDO inhibitor 1-methyl-tryptophan (1 MT), confirming that this effect of Zebularine is mainly caused by IDO induction. Differences using Zebularine-treated or non-treated cells for in vitro restimulation were marginal.

CONCLUSION

Low dose treatment with Zebularine (20 microM) decreases the production of the immunosuppressive IDO from rat colon cancer cells and enhances their immunogenicity, whereas high dose Zebularine treatment (100 microM) enhances the IDO production from the cancer cells and suppresses their immunogenicity. This immunosuppression should be considered when cancer is treated with Zebularine or drugs acting in a similar way.

Quantification of neurotrophin-3 mRNA in the rat hippocampal subregions using the RT-PCR-based coamplification method

Quantitative reverse transcription-polymerase chain reaction (RT-PCR) is a suitable method for determining the expression levels of rare mRNAs in small amounts of tissue. To compare the mRNA expression levels across specific brain regions, we adopted an RT-PCR method in which a target gene was coamplified with an endogenous internal standard gene in single reaction tubes. Use of the endogenous internal standard can control fluctuations in target quantification resulting from various factors, including tube-to-tube variation in amplification efficiency and variation in mRNA content among the total RNAs prepared from different tissues. In this study, we quantitatively determined the mRNA expression levels for NT-3, a member of the neurotrophin family of growth factors, in the hippocampal subregions: the entorhinal cortex, dentate gyrus and CA1. NT-3 gene was simultaneously coamplified with an endogenous internal standard gene, hypoxanthine-guanine phosphoribosyltransferase (HPRT), in the same reaction tube. Using this RT-PCR coamplification method, we detected a regional difference in the NT-3 mRNA expression levels across the hippocampal subregions. Our method can serve as a useful quantification method to investigate molecular signaling cascades in a specific cortical region.