5-aminolevulinic-acid-hexyl-ester and Nasopharyngeal-Neoplasms

Nasopharyngeal carcinoma (NPC) is of high prevalence in Hong Kong and southern China. The pathogenesis of NPC is closely associated with Epstein-Barr virus (EBV) infection via regulation of viral oncoprotein latent membrane protein 1 (LMP1). The conventional treatment for NPC is chemo-radiotherapy, but the prognosis remains poor for advanced stage, recurrent and metastatic NPC. Photodynamic therapy (PDT) is a therapeutic approach to combat tumors. PDT effectiveness depends on the interaction of photosensitizers, light and molecular oxygen. 5- aminolevulinic acid hexyl derivative (H-ALA) is one of the photosensitizers derived from 5-ALA. H-ALA with improved lipophilic properties by adding a long lipophilic chain (hexyl group) to 5-ALA, resulted in better penetration into cell cytoplasm. In this study, the effect of H-ALA-PDT on NPC cells (EBV positive C666-1 and EBV negative CNE2) was investigated. The H-ALA mediated cellular uptake and cytotoxicity was revealed via flow cytometry analysis and MTT assay respectively. H-ALA PDT mediated protein modulation was analysed by western blot analysis. Our finding reported that the cellular uptake of H-ALA in C666-1 and CNE2 cells was in a time dependent manner. H-ALA PDT was effective to C666-1 and CNE2 cells. EBV LMP1 proteins was expressed in C666-1 cells only and its expression was responsive to H-ALA PDT in a dose dependent manner. This work revealed the potential of H-ALA PDT as a treatment regiment for EBV positive NPC cells. Understanding the mechanism of H-ALA mediated PDT could develop improved strategies for the treatment of NPC.

Topics: Aminolevulinic Acid; Cell Line, Tumor; Cell Survival; Herpesvirus 4, Human; Humans; Lasers, Semiconductor; Low-Level Light Therapy; Nasopharyngeal Neoplasms; Photochemotherapy; Photosensitizing Agents; Protoporphyrins; Viral Matrix Proteins

5-aminolevulinic acid (ALA) and its hexylester (ALA-H) are the drugs currently used in photodynamic therapy (PDT). The side effect, especially the long-term side effect of these drugs is a problem of concern in this field, which has not been clearly understood yet.. The normal lymphocytes and nasopharyngeal carcinoma (NPC) cells were used as the cell models to evaluate the side effects of ALA or ALA-H in the absence of light or under sub-lethal doses of light.. The cytotoxic and DNA-damaging effects of ALA or ALA-H on lymphocytes and NPC cells were studied by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the alkaline comet assay. ALA at 0.75 mM concentration and ALA-H at 10-microM concentrations were selected in the studies. This is because under these concentrations, ALA- or ALA-H-mediated PDT can destroy most NPC cells in vitro. The intracellular distributions of the protoporphyrin IX (PpIX), induced by the ALA or ALA-H, were measured by the confocal laser scanning microscope to provide more information for understanding the DNA damage.. The incubation of 0.75 mM ALA or 10 microM ALA-H alone (without light) did not cause DNA damage as well as the considerable cytotoxic effect on NPC cells. However, after ALA (0.75 mM) incubation and without light irradiation, the serious cytotoxicity and remarkable DNA damage were found in lymphocytes. When the lymphocytes were incubated with ALA-H (10 microM) alone (in the absence of light), no DNA damage could be detected and a slight cytotoxic effect was found. Both ALA and ALA-H induced PpIX in the lymphocytes. The fluorescence images of PpIX intracellular localization demonstrated that the PpIX diffused into the nuclear region in ALA-(0.75 mM)-incubated lymphocytes but not existed in the nucleus of ALA-H(10 microM)- incubated lymphocytes, providing an explanation for the facts that ALA (0.75 mM) induced the DNA damage while ALA-H (10 microM) did not.. These results suggested that the genotoxic potential of lymphocytes seems high for ALA (0.75 mM) and could be excluded for ALA-H (10 microM).

Topics: Aged; Aminolevulinic Acid; Cell Line, Tumor; Cell Survival; Comet Assay; DNA Damage; Humans; Lymphocytes; Male; Microscopy, Confocal; Mutagens; Nasopharyngeal Neoplasms; Photosensitizing Agents; Protoporphyrins; Ultraviolet Rays

Nasopharyngeal carcinoma (NPC) is a prevalent cancer in Hong Kong and southern China. To explore a new modality of NPC treatment, 5-aminolevulinic acid (ALA) or its hexyl ester (ALA-H) mediated photodynamic therapy (PDT) was studied in vitro. The results show that NPC cells are sensitive to both ALA and ALA-H mediated PDT. However, ALA-H PDT is much more effective at cell inactivation than ALA-PDT, due to a higher efficiency of ALA-H on producing endogenous protoporphyrin (PpIX) in cells. Both apoptosis and necrosis are involved in cell death, but apoptosis plays a major role under the short time incubation of drugs. ALA and ALA-H mediated PDT not only destroy the cells directly, but also inhibit the expression of matrix metalloproteinase-2 (MMP2) in cells, a maker for tumor metastasis. The ALA-H shows promising PDT results on NPC in vitro; therefore it is worth investigating further in vivo for NPC treatment.

Topics: Aminolevulinic Acid; Apoptosis; Carcinoma; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Flow Cytometry; Humans; Matrix Metalloproteinase 2; Microscopy, Fluorescence; Nasopharyngeal Neoplasms; Neoplasm Metastasis; Photochemotherapy; Photosensitizing Agents