Up-regulation of CacyBP/SIP during rat breast cancer development

CacyBP/SIP (calcyclin binding protein/Siah-1 interacting protein) was originally discovered in Ehrlich ascities tumor cells but was later found also in many different tumors. To better understand the function of CacyBP/SIP in carcinogenesis, we used immunohistochemistry, Western blotting, and RT-PCR assays to study the distribution and level of CacyBP/SIP in mammary tissues after tumor induction in rat with DMBA [(dimethylbenz[a]anthracene)]. Application of such a model allowed us to monitor changes in CacyBP/SIP level during development of breast cancer. We found that both the protein and mRNA levels of CacyBP/SIP gradually increased in pathologically changed tissues and were highest in tumors taken 8 weeks after DMBA treatment. Similar changes as for CacyBP/SIP were detected in the level of beta-catenin. Increase in CacyBP/SIP expression during development of breast cancer, observed early in the mammary tissues with only minimal pathological changes, might suggest an important role of this protein in the process of carcinogenesis.