In vitro study of biosynthesis of protoporphyrin IX induced by Ù-Aminolevulinic acid in normal and cancerous cells of the human cervix

RESUMO

Bxkground. Ù-Aminolevulinic acid (ALA) is recognized as the starter in the biosynthesis of the heme group, the structural basis of cytochromes, chlorophylls, biliary pigments, and other porphyrins. It is the first intermediary in the biosynthesis of protoporphyrin IX (PpIX), and of ther heme group. PpIX is present in low concentration in normal cells, and in high concentration in tumor cells. Methods. The accumulation of protoporhyrin IX (PpIX) induced by Ù-aminolevulinic acid (ALA) was tested in two cervico-uterine cancer cell lines (HeLa and CaLo), and in normal human cervical epithelial (NHCE) cells. Results. The optimal concentration of ALA that induced maximum levels of intra- and extracellular accumulation of PpIX in both HeLa and NHCE cells was 300 µg of ALA/mL, and for CaLo cells, 150 µg/mL. The viability of HeLa, CaLo, and NHCE cells exposed to ALA measured 81, 98 and 84 percent, respectively. The optimale time for accumulation of PpIX, both intra- and extracellular, was 4 h for HeLa and NHCE cells and 5 h for CaLo cells per 24 h of expusure to optimal concentrations of ALA. After the maximum level of PpIX accumulation was reached, there was a gradual decrease until there was only a small quantity. A statistically significant difference (p <0.0001) was foundf in the accumulation of PpIX, depending on the concentrations of ALA used as well as between cervical cancer cell lines and 17, and for NHCE and CaLo cells. 15. Conclusions. These results are important for determining the usefulness of the sensitizer (PpIX)