Granzow C, Kopun M, Kröber T
Department Biochemie der Zelle, Deutsches Krebsforschungszentrum (0225), Heidelberg, Germany.
Cancer Res. 1995 Nov 1;55(21):4837-43.
Poor reproducibility of cytotoxicity tests with Vinca alkaloids has frequently been reported. A commonly presumed light sensitivity of the drugs could not be confirmed. However, we found that they are photosensitized by riboflavin (vitamin B2), an obligatory component of cell culture media. Light of wavelengths below 500 nm triggered rapid photoreactions of riboflavin with vinblastine, vincristine, and vindesine in aqueous solutions. The photoreactions altered the absorption spectra of these alkaloids and yielded degradation products that could be separated by TLC. In cell cultures, both immediate and persisting, riboflavin-mediated photoreactivity could be distinguished. They preclude reliable determinations of sensitivity and resistance to Vinca alkaloids, as exemplified on chemosensitive and multidrug-resistant mouse ascites cells. In experiments involving photosensitization, the 50% inhibitory concentration values of sensitive and resistant cells were overlapping and fluctuated in the ranges from 3 to 30 nM and 15 to 360 nM vinblastine, respectively. Corresponding values from series of experiments protected from photosensitization were 1.02 +/- 0.22 nM and 18.5 +/- 3.42 nM. Hence, riboflavin-mediated photoreactions must be fully prevented in assays of cellular drug sensitivity. Procedures for eliminating immediate as well as persisting photoreactivity were established.
长春花生物碱细胞毒性试验的重现性差经常有报道。通常认为的药物光敏感性并未得到证实。然而，我们发现它们可被核黄素（维生素B2）光敏化，核黄素是细胞培养基的一种必需成分。波长低于500 nm的光会引发核黄素与长春碱、长春新碱和长春地辛在水溶液中的快速光反应。这些光反应改变了这些生物碱的吸收光谱，并产生了可用薄层色谱法分离的降解产物。在细胞培养中，可以区分即时的和持续的核黄素介导的光反应性。它们妨碍了对长春花生物碱敏感性和抗性的可靠测定，以化学敏感和多药耐药小鼠腹水细胞为例。在涉及光敏化的实验中，敏感细胞和耐药细胞的50%抑制浓度值相互重叠，长春碱的波动范围分别为3至30 nM和15至360 nM。未进行光敏化的系列实验的相应值分别为1.02±0.22 nM和18.5±3.42 nM。因此，在细胞药物敏感性测定中必须完全防止核黄素介导的光反应。已建立消除即时和持续光反应性的程序。
