CIP-13F, a novel aminopeptidase N (APN/CD13) inhibitor, inhibits Lewis lung carcinoma growth and metastasis in mice.

PURPOSE

Aminopeptidase N (APN/CD13) is highly expressed on the surface of cancer cells and is thought to be involved in cancer growth and metastasis. The research of APN/CD13 inhibitors is considered as a strategy of cancer treatment. We aimed to evaluate the efficacy of CIP-13F, a novel APN/CD13 inhibitor, using a Lewis lung carcinoma (LLC) implantation mouse model.

METHODS

C57BL/6 mice were subcutaneously inoculated with LLC cells in anterior flank. Then, 0, 50 and 100 mg/kg of CIP-13F were injected via vena caudalis. Bestatin was used as the positive control. Administration of CIP-13F or bestatin was performed daily for 3 consecutive weeks. Mice were killed, and the tumors in anterior flank and metastasis nodules in lungs were examined. The assays of immunohistochemical staining, immunofluorescent flow cytometry and western blotting were performed to estimate the expression of APN/CD13 in LLC cells. We carried out the experiments of Annexin-V/PI staining, DNA fragmentation analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining to determine apoptotic cells in LLC tissues. Using immunohistochemical staining with CD34, the antiangiogenesis of CIP-13F was evaluated in LLC tissue sections.

RESULTS

CIP-13F treatment resulted in a significant delay of LLC growth in anterior flank. Examination of lungs showed that the number of metastatic nodules of LLC was also markedly decreased. The inhibitory effect of CIP-13F on LLC growth was further evidenced by the induction of LLC apoptosis, showing the increases in Annexin-V/PI staining cells, DNA fragmentation and TUNEL staining cells. Molecular analyses of LLC tissues in CIP-13F-treated mice suggested that the decrease in APN/CD13 expression by CIP-13F might account for its actions of mechanism. Further, the inhibition of angiogenesis in LLC tissues was determined, showing the decreases in microvessel density (MVD) and angiogenic factors including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and transforming growth factor-alpha (TGF-α).

CONCLUSION

Our results showed that CIP-13F effectively inhibited LLC growth and pulmonary metastasis in mice and suggested that CIP-13F is a potential drug for the treatment for cancers with positive APN/CD13 expression.