A supercritical CO2 extract of neem leaf (A. indica) and its bioactive liminoid, nimbolide, suppresses colon cancer in preclinical models by modulating pro-inflammatory pathways

Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second leading cause of cancer death in men and women in the United States. Anti-inflammatory blockade has been proven to be a promising avenue of colorectal cancer prevention. However, NSAIDs while effective in curbing CRC risk are too toxic for longterm use in cancer prevention. The Neem tree (Azadirachta indica) is rich in liminoid terpenoids, collectively known as azadiractoids and has been shown to have anti-inflammatory effects. To explore a role of neem in CRC, human colon cancer cell lines HCT116 and HT29 cells were treated with purified Super Critical Neem Extract (SCNE) or the neem liminoid, nimbolide. SCNE treatment resulted in a dose dependent inhibition of CRC cell proliferation and an increase in apoptosis. Treatment with SCNE and nimbolide decreased the expression of transcriptional factors, STAT3 and NF-KB which plays a major role in gene regulation of multiple cellular processes. Protein expression of COX1, IL-6, and TNF-alpha were decreased on treatment with SCNE in CRC cells. Western blots and Zymogram assays results revealed anti-invasive effect by decreased expression of MMP2 and MMP9 proteins in CRC cells. Overall, these data confirm a potential anti-cancer effect of SCNE, reducing cell proliferation, inflammation, migration, and invasion in human colon cancer cells. Confirming these indications, we found that treatment of mice bearing HT29 and HCT116 xenografted tumors exhibited striking inhibition of colon tumor growth. Clearly we must explore the effect of neem in preclinical animal models for anti-cancer therapy.