A conjugate of camptothecin and a somatostatin analog against prostate cancer cell invasion via a possible signaling pathway involving PI3K/Akt, aV?3/aV?5 and MMP-2/-9 - siRNA Conjugates

A conjugate of camptothecin and a somatostatin analog against prostate cancer cell invasion via a possible signaling pathway involving PI3K/Akt, aV?3/aV?5 and MMP-2/-9
Available online 27 April 2006.
Li-Chun Sun, , Jing Luo, L. Vienna Mackey, Joseph A. Fuselier and David H. Coy
Cancer Letters
Abstract
Camptothecin (CPT) was conjugated to the N-terminal of a somatostatin analog (SSA) directly via a carbamate group and a basic N-terminal linking motif, d-Lys-d-Tyr-Lys-d-Tyr-d-Lys. This new CPT-SSA conjugate termed JF-10-81 was evaluated as a receptor-specific delivery system for its anti-invasive and anti-angiogenic activities. It was found that, in addition to blocking migration and invasion of highly invasive prostate cancer PC-3 cells, this conjugate also inhibited in vitro capillary-like tube formation of endothelial cells and in vivo angiogenesis in C57B1/6N female mice. JF-10-81 was found to block PC-3 cell attachment to various extracellular matrix components, mainly to vitronectin, the ligand of cell surface receptors integrin aV?3 and aV?5. Additionally, JF-10-81 reduced expression of integrins aV?3 and aV?5 on PC-3 cell surfaces, without effects on ?1 or any a?1 heterodimers. This conjugate also inactivated phosphorylation of protein kinase B (PKB/Akt), down-regulated the expression of latent matrix metalloproteinase (MMP) -2 and MMP-9, but had little effect on MMP-3/-10. Meanwhile, membrane type-1 matrix metalloproteinase (MT1-MMP) and the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) were not detectable in PC-3 cells. aV?3/aV?5 and MMP-2/-9 are known to be highly expressed in many tumor cells and play an important role in tumor progression. Our results support that this conjugate could possibly inhibit prostate cancer PC-3 cell invasion through a signaling pathway involving PI3K/Akt, aV?3/aV?5 and MMP-2/-9, and this SSA could be used as an efficient vector to deliver CPT or other cytotoxic agents to target sites for cancer therapy.
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