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 increased ODC expression made the typically tumor-resistant C57Bl/6 mice more sensitive to tumor-promoting effects. However, when doxycycline was used to repress ODC expression, the number of papillomas was significantly reduced, demonstrating the critical role of ODC in tumor promotion.