Abstract 1888: Ocimum gratissimum: a novel natural inhibitor of Matrix Metalloproteases

Abstract

Abstract Ocimum sp. (a.k.a. holy basil or tulsi), exhibits chemo-preventive, anti-carcinogenic, free radical scavenging, radio-protective and numerous other pharmacological properties, and has therefore, been one of the most popular herbs used in Asian and European countries for the treatment of various ailments since ancient times. Extract of Ocimum gratissimum (OG) inhibits proliferation, migration, anchorage-independent growth, three-dimensional growth and morphogenesis, and induction of COX-2 protein in breast cancer cells. In addition, OG extracts also reduced tumor size and neoangiogenesis in a MCF10A DCIS.com xenograft model of human DCIS, suggesting that OG leaf extract may be of value as a breast cancer preventive and therapeutic agent. In an effort to identify the biological target of OG activity, we observed that the aqueous extract of OG inhibited the cleavage of galectin-3 in in vitro conditions. Galectin-3 is a carbohydrate-binding tumor-associated protein containing a collagen-alpha like domain, which is cleavable by Matrix-metalloproteases-2 and −9. We questioned whether the inhibition of galectin-3 cleavage by OG is due to the inhibition of enzymatic activity of MMPs, or the interactions between the MMPs and galectin-3. MCF10AT1, MCF10A and MCF10AEIII8 cells were incubated with various concentrations of the extract and the conditioned media were analyzed for galectin-3 cleavage as well as the gelatinolytic activity by gelatin zymography. The results showed an inhibition of galectin-3 cleavage in the treated cells, but no differences in the MMP activities between the treated and the untreated cells were observed in the zymogram. Next, we performed the gelatin zymography on the recombinant MMP-2 and −9 and incubated the gel with the extract. An inhibition of the gelatinolytic activity was observed in the treated gel. A dose dependent decrease in the MMP-2 and −9 activity was also observed when a fluorogenic peptide, MOCAcPLGLA2pr(Dnp)AR-NH2 was used as a substrate. Furthermore, an inhibition of in vivo activities of MMP-2 and MMP-9 was observed using in situ zymography of fresh frozen MCF10ADCIS.com xenografts in nude mice fed on OG extract compared to the water fed mice. A reduced cleavage of galectin-3 in xenografts harvested from the OG fed mice also indicates a reduced MMP activity. Fractionation of the crude extract indicates that the inhibitory activity is specific to the methanol soluble fraction of OG. Further purification of this fraction by is in progress. The results suggest that OG inhibits the enzymatic activity of MMP-2 and −9 and can be developed as a novel non-toxic therapeutic agent preventing the invasion and progression of cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1888.