Cytotoxicity of Sodium Benazldehyde Derivatives against OSCC Cell Lines

Objective: Sodium 5,6-benzylidene-L-ascorbate (SBA) has produced prominent anti-tumor effects on inoperative cancer patients, by still unidentified mechanism. We investigated the tumor specificity and type of cell death induced by SBA in various tumor cell lines including oral squamous cell carcinoma (OSCC) cell lines. Method: The dose-response curve was used to determine the 50% cytotoxic concentration (CC₅₀). Tumor-specificity index was calculated by the ratio of mean CC₅₀ for normal cells to that for tumor cell lines. Apoptosis markers used were internucleosomal DNA fragmentation (measured by agarose gel electrophoresis) and caspase-3,-8, -9 activation (measured by cleavage of substrates). Autophagy markers used were acridine orange staining (for detection of acidic organelles) and transmission electron microscopy (for detection of fine cell structure). Results: SBA showed slightly higher cytotoxicity against human tumor cells lines, as compared with normal cells, with a tumor-specificity index of 2.0. Human myelogenous leukemica cell lines (HL-60, ML-1, KG-1) were the most sensitive to SBA,followed by human OSCC (HSC-2, HSC-3, HSC-4) and human glioblastoma (T98G, U87MG). Human normal cells (gingival fibroblast, pulp cell, periodontal ligament fibroblast)were the most resistant. SBA failed to induce internucleosomal DNA fragmentation and caspase-3, caspase-8, caspase-9 activation in HSC-2, HSC-4, HL-60 and T-98G cells, in contrast to actinomycin D treatment that induced both of these apoptosis markers. Electron microscopy and acridine orange staining demonstrated that SBA induced the destruction of mitochondrial structure and digestion of broken organelles by the secondary lysosome in all of these cells. Cyclodexrin benzaldehyde inclusion compound induced similar changes in OSCC cell lines with SBA. Conclusion: The present study suggests that benzaldehyde derivatives generally induce autophagic cell death in OSCC cell lines.