Conversion of C57Bl/6 Mice from a Tumor Promotion-Resistant to a Sensitive Phenotype by Enhanced Ornithine Decarboxylase Expression

The study developed a transgenic mouse model to investigate the role of ornithine decarboxylase (ODC) in tumor promotion. By using a tetracycline-regulated system, researchers were able to overexpress ODC specifically in hair follicle keratinocytes of C57Bl/6 mice. In the absence of doxycycline, these mice showed high levels of epidermal ODC activity and hyperplasia when exposed to the tumor promoter TPA, particularly affecting hair follicles. This effect was reversed by adding doxycycline, which repressed transgene expression. The study concluded that increased ODC expression made the typically tumor-resistant C57Bl/6 mice more susceptible to tumor promotion by TPA, highlighting the significance of ODC in tumor development.