Identification of a potent peptide antagonist to an active laminin-1 sequence that blocks angiogenesis and tumor growth.

The extracellular matrix plays an important role in many physiological processes. We have identified >20 angiogenic sites in the extracellular matrix protein laminin-1. The most potent sites are A13 (RQVFQVAYIIIKA) and C16 (KAFDITYVRLKF), which are present in homologous NH(2)-terminal domains of the alpha 1 and gamma 1 chains, respectively. We reported recently that a scrambled C16 sequence, C16S (DFKLFAVTIKYR), acts as an antagonist to both peptides. Here, we have identified a stronger antiangiogenic peptide, C16Y (C16S with a T to Y substitution), with potent activity in several biological assays including tumor growth. C16Y is more potent in promoting endothelial cell attachment and inhibiting attachment to laminin-1 than either C16 or C16Y. Disruption of tube formation by C16Y is also observed at concentrations at least five times lower than C16S. The minimal active sequence was found to be DFKLFAVY. C16Y is more potent in blocking C16-induced chick chorioallantoic membrane angiogenesis than C16S. Tumor growth studies on the chick chorioallantoic membrane showed that C16Y reduces breast cancer cell growth without affecting cell proliferation. This result suggests that angiogenesis is being inhibited by the peptide. In vivo animal studies demonstrated that C16Y treatment significantly reduced tumor growth and decreased tumor vessel number, as compared with controls, additionally suggesting that angiogenesis was affected. These results indicate that we have identified a more potent antiangiogenesis inhibitor peptide that may be used as a therapeutic to treat cancer.