Inhibitory action of emulsified sulfoquinovosyl acylglycerol on mammalian DNA polymerases.

We reported previously that sulfoquinovosyl diacylglycerol and sulfoquinovosyl monoacylglycerol (SQDG/SQMG) are potent inhibitors of mammalian DNA polymerases and DNA topoisomerase II, and can be potent immunosuppressive agents and anticancer chemotherapy agents [Matsumoto, Y., Sahara, H., Fujita T., Shimozawa, K., Takenouchi, M., Torigoe, T., Hanashima, S., Yamazaki, T., Takahashi, S., Sugawara, F., et al., An Immunosuppressive Effect by Synthetic Sulfonolipids Deduced from Sulfonoquinovosyl Diacylglycerols of Sea Urchin, Transplantation 74, 261-267 (2002); Sahara, H., Hanashima, S., Yamazaki, T., Takahashi, S., Sugawara, F., Ohtani, S., Ishikawa, M., Mizushina, Y., Ohta, K., Shimozawa, K., et al., Anti-tumor Effect of Chemically Synthesized Sulfolipids Based on Sea Urchin's Natural Sulfonoquinovosylmonoacylglycerols, Jpn. J. Cancer Res. 93, 85-92 (2002)]. In those experiments, the in vivo effectiveness greatly depended on the degree of water solubility of SQDG/SQMG. In the present work, we studied the emulsification of SQDG/SQMG in terms of their use in in vivo experiments. Lipid emulsions containing SQDG/SQMG (oil-in-water emulsions) in which the particle size was smaller than 100 nm were designed and synthesized, and then the biochemical modes of emulsified SQDG/SQMG were studied in comparison with those of SQDG/SQMG solubilized by DMSO. Emulsified SQDG/SQMG are also selective mammalian DNA polymerase inhibitors and potent antineoplastic agents but do not inhibit the DNA topoisomerase II activity. The growth inhibition effect of emulsified SQMG to NUGC-3 cancer cells was twofold stronger than DMSO-soluble SQMG (69 and 151 microM, respectively). From these results, the properties of lipid emulsions containing SQDG/SQMG and their possible use in in vivo experiments including clinical use are discussed.