Reduction of invasiveness of human glioma cells by ALA mediated photodynamic therapy

摘要

Introduction: High grade gliomas are characterised by rapid and invasive growth, that cause massive tissue destruction at both the tumour- brain boarder as well as in regions remote from the tumor core. Eradication or inhibition of infiltrating glioma cells poses a significant clinical challenge that is unlikely to be solved using conventional treatment regimens consisting of ionizing radiation and chemotherapeutic agents. In this study we evaluated the effects of ALA mediated photodynamic therapy (PDT) on the invesivness of human glioma cells migrating from implanted multicell tumor spheroids. Materials and method 3-400nm diameter tumor spheroids, derived from the human glioma cell line ACBT, were implanted into a gel matrix of collagen type Ⅰ. 24 hours following implantation there was a significant invasion of the surrounding gel by individual tumor cells to an average distance of 400nm. The cultures were incubated in increasing concentrations of ALA (10-1000 ug/ml) for four hours and then exposed to 635nm laser light in a titration of both fluence level and fluence rate. Results Fluences of 25 J/cm~2 were clearly cytotoxic for both the infiltrating cells as well as the spheroids at all ALA concentrations. Fluence levels of 6J did not stop the spheroid growth or prove cytotoxic to the glioma cells that had previously migrated into the gel, in a majority of cultures but inhibited further migration of the cells by 80-90% compared to control. Conclusion: Measurement of cell survival and cell proliferation indices seemed to indicate a direct migratory inhibition effect on the invading cells and not cytotoxicity as the most likely mechanism for this observation.