Tadayoshi Kaneko

Preventive effect of rebamipide gargle on chemoradiotherpy-induced oral mucositis in patients with oral cancer: a pilot study.

ABSTRACT Objectives To assess the efficacy and safety of rebamipide in preventing chemoradiotherapy-induced oral mucositis in patients with oral cancer. Material and Methods Patients with oral cancer treated with chemoradiotherapy (daily radiotherapy plus docetaxel hydrate once a week) were enrolled for this study. They were assigned in a double-blind fashion to receive either rebamipide gargle or placebo on the days of chemoradiotherapy. Oral mucositis was assessed using the WHO grading system. The primary endpoint of this study was the incidence of grade 3 - 4 mucositis after exposure to 40 Gy radiation (4 weeks). The secondary endpoint was the effect of rebamipide gargle on tumour response to chemoradiotherapy. Results Twenty-four patients were randomly assigned to receive rebamipide gargle (n = 12) or placebo-gargle (n = 12) during chemoradiotherapy. The number of patients with severe mucositis (WHO ≥ 3) was higher in the placebo group than in the rebamipide group (83.3% vs. 33.3%, P = 0.036). In addition, no effect of rebamipide gargle on tumour response to chemoradiotherapy was recognized compared with the placebo group. Conclusions For patients with oral cancer undergoing chemoradiotherapy, rebamipide gargle may contribute to decrease the severity of oral mucositis.

Partial Protection of Paclitaxel-induced Neurotoxicity by Antioxidants.

Background/Aim: In order to search for substances that reduce the neurotoxicity of paclitaxel, the sensitivity of differentiated rat neuronal PC12 cells to paclitaxel was compared to that of malignant and non-malignant cells, and the extent to which four antioxidants can alleviate paclitaxel-induced neurotoxicity was investigated. Materials and Methods: Viability of cells was determined by the MTT method. Cytotoxicity was evaluated as the concentration that reduced cell viability by 50% (CC50). Tumor specificity of paclitaxel was determined as the ratio of CC50 against non-malignant cells to that against malignant cells. Results: Paclitaxel was three-fold more cytotoxic towards human oral squamous cell carcinoma cell lines (Ca9-22, HSC-2, HSC-3. HSC-4) than human normal epithelial and mesenchymal (human gingival fibroblast, human periodontal ligament fibroblast, human pulp cell) normal cells, confirming its antitumor potential. However, paclitaxel at as low a concentration as 5 ng/ml significantly reduced neurite formation in nerve growth factor-induced differentiated PC12 cells, although complete killing of cells was not achieved even at 2,000-fold higher concentration (10 μM). Paclitaxel-induced neurotoxicity was enhanced with the prolongation of incubation time and reduction of inoculation cell density. Four antioxidants, namely docosahexaenoic acid, acetyl-L-carnitine hydrochloride, N-acetyl-L-cysteine and sodium ascorbate, only partially protected PC12 cells from paclitaxel-induced toxicity. Conclusion: The present study suggests the involvement of both oxidative and other mechanisms in paclitaxel-induced neurotoxicity.

Change in Anticancer Drug Sensitivity During Neuronal Differentiation of PC12 Cells.

Background/Aim: Although there are many reports of anticancer drug-induced neurotoxicity, most previous data have been derived from neuronal cell models grown in a variety of culture conditions. This has prevented accurate assessment of the potency of their neurotoxicity and of changes in drug sensitivity of neuronal cells during differentiation. In this study, a simple neuronal differentiation induction system was established and the relative potency of neurotoxicity of eight anticancer drugs was compared during neuronal cell differentiation. Materials and Methods: Rat PC12 cells were induced to differentiate into neuronal cells by 50 ng/ml nerve growth factor in serum-free Dulbeccos modified Eagles medium, followed by overlay of fresh nutrients at day 3, without medium change. Cell viability was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Results: During differentiation, PC12 cells became 1.1-to more than 10,000-fold resistant to anticancer drugs. Topoisomerase inhibitors (doxorubicin, SN-38, etoposide) were the most toxic to differentiated PC12 cells, followed by docetaxel, gefitinib, melphalan, 5-fluorouracil and methotrexate. Docetaxel showed the highest cytotoxicity against undifferentiated PC12 cells, but its cytotoxicity was dramatically reduced during differentiation. Conclusion: The present study demonstrated considerable variation in the neurotoxicity of anticancer drugs during the cell differentiation process. The present simple assay system may be useful to search for neuroprotective substances.