Sensitization by glycerol for CDDP-therapy against human cultured cancer cells and tumors bearing mutated p53 gene.

To clarify effective chemotherapeutic regimens against cancer, we examined the effects of glycerol on apoptosis induced by CDDP treatment using cultured human cancer cells (in vitro) and transplanted tumor in mice (in vivo). Human tongue cell carcinoma (SAS) cells transfected with mutated p53 gene (SAS/m p53) showed CDDP-resistance compared with the cells with neo control gene (SAS/ neo). When those cultured cells were pre-treated with glycerol, CDDP-induced apoptosis was enhanced by glycerol in SAS/m p53 cells but not in SAS/ neo cells. In tumor-transplanted mice, the glycerol treatment to tumors enhanced growth delay induced by CDDP in mp53 tumors transplanted with SAS/m p53 cells, but not in wtp53 tumors transplanted with SAS/ neo cells. When transplanted tumors were treated with CDDP alone, the cells positive for active caspase-3, 85 kDa PARP and apoptosis were observed by immunohistochemical staining in wtp53 tumors but not in mp53 tumors. When the tumors were treated with CDDP combined with glycerol, positive cells were observed not only in wtp53 tumors but also in mp53 tumors. These results showed that the CDDP-induced growth inhibition of the tumors is p53 -dependent and that the enhanced growth delay by glycerol may be due to the increased apoptosis. Glycerol might be available for cancer chemotherapy in patients with mp53 tumors.

CDDP induces p53-dependent apoptosis in tongue cancer cells.

We have investigated the CDDP sensitivities of two tongue cancer cell lines with differing p53 genetic status, one with wild-type p53 (SAS) and the other with mutant-type p53 (HSC-4). SAS was about 2 times more sensitive at the D10 dose and demonstrated increased p53 and Bax protein levels at 10 h after CDDP treatment on Western blot analysis. On the other hand, overexpression of p53 in HSC-4 was observed without CDDP treatment and no elevation of Bax could be detected. Apoptosis was observed after CDDP treatment in SAS but not in HSC-4 by Hoechst 33342-staining and electrophoresis methods. These findings indicate that p53 plays an important role in apoptosis as a positive regulator of Bax expression. It is suggested that p53 status may have predictive potential with regard to response to CDDP therapy.

Transfection with mutant p53 gene inhibits heat-induced apoptosis in a head and neck cell line of human squamous cell carcinoma.

PURPOSE: To confirm that human cancer cells show p53-dependent heat sensitivity through an apoptosis-related mechanism, we examined the heat sensitivity and Bax-mediated apoptosis after heating in a human squamous cell carcinoma cell line, SAS, with identical genetic backgrounds except for the p53 status. MATERIALS AND METHODS: We performed colony formation assay, Western blotting and analyses of apoptosis, using the SAS cells transfected with pC53-248 vector with mutant p53 gene (SAS/Trp248 cells) or the cells transfected with pCMV-Neo-Bam vector (SAS/neo cells) as a control. RESULTS: SAS/Trp248 cells showed heat resistance due to the dominant negative nature of mp53, compared with SAS/neo cells. The incidence of DNA ladders and apoptotic bodies increased markedly after heating in SAS/neo cells, but increased very little in SAS/Trp248 cells. CONCLUSION: These results suggest that heat resistance brought by mp53-transfection is p53-dependent and closely correlates with the induction of apoptosis in human squamous cell carcinomas.

[Flow cytometric analysis of DNA ploidy in nasosinal papilloma].

Using paraffin embedded specimens taken from 32 patients with histologically benign nasosinal papillomas, we conducted nuclear DNA analysis by flow cytometry and studied the biological degree of malignancy in this disease. Aneuploidy, which is frequently observed in malignant tumors was not seen in any of these nasosinal papilloma cases. Age did not affect either S+G2M % or polyploid %, two parameters that reflect cell proliferation capacity. Both parameters, S+G2M % and polyploid %, were higher in inverted papillomas which are more likely to become malignant than epithelial papillomas. In recurrent cases of nasosinal papilloma both S+G2M % and polyploid % were higher than in nonrecurrent cases. Moreover, the polyploid % was significantly different, supporting speculation that this can be used as a parameter for predicting recurrence of nasosinal papilloma.