Overexpression of HER-2 oncogene is reported in more than 60% of ductal carcinoma in situ (DCIS) breast cancer, including 30% estrogen receptor negative chemotherapy resistant high-grade tumors with metastatic phenotype. Recent studies show high correlation between MRI characteristics and lower ER score, higher grade, much higher CD68 count (inflammatory marker) and extensive comedo necrosis of DCIS. The inflammatory cytokine IL-8 is found to be overexpressed in most ER- breast cancers and is recently suggested as a marker of tumor invasion and metastasis. Curcumin (CUR) the active component of the spice turmeric, known for its immunomodulatory, antimutagenic and antitumorigenic properties and was found to inhibit cell proliferation and mitogenic signal transduction pathways in ER negative, HER-2 positive DCIS breast cancer model.
Normal 184-B5 breast epithelial cells and transformed 184-B5/HER cells in log phase were exposed to 0, 5, 10 and 20 μM CUR for 24 and 48 hours and analyzed for dose response, cell viability, cell cycle distribution, gene expression and HER-2 signal transduction protein markers.
184-B5/HER cells exhibit hyper-proliferation, shorter population doubling time, higher saturation density, reduced rate of apoptosis, higher anchorage independent growth and tumorigenecity compared to the non-tumorigenic ER-, PR-, HER2-, EGFR+ and p53+ parental immortalized 184-B5 cells. Cell cycle analysis of 184-B5/HER cells exposed to 20μM CUR showed cytostatic arrest of growth, 85% inhibition of colony formation, decreased G0/G1: S+G2/M ratio and increased apoptosis. Microarray data showed 557 probes to be modulated in 20μM CUR (24 hrs) treated 185-B5/HER cells (117 upregulated, 380 downregulated). These include reduced expression of cell cycle regulatory genes such as cyclin A (-2.79), cyclin B2 (-3.89), cyclin D1 (-1.50), cdk2 (-1.69) and Cdc25c (-3.80). Decreased levels of Cyclin B2, cdk2 and Cdc25c cell cycle proteins in 184-B5/HER cells, reflect CUR induced cell cycle arrest in S and G2/M phases. Treatment with CUR decreased NFkB (-1.86) in 184-B5/HER cells suggesting modulation of downstream signaling pathways including the inflammatory cascade. We observed a 10 fold higher levels of interleukin-8 (IL-8) gene expression in 184-B5/HER cells compared to 184-B5 cells, while treatment with CUR dramatically reduced the IL-8 gene expression as revealed by both microarray and real-time PCR.
Treatment of breast epithelial 184-B5/HER cells with CUR show preventive efficacy in this ER negative DCIS model via cytostatic arrest in S and G2/M phases of the cell cycle, by downregulation of ERK pathway and induction of apoptosis, verified at both the gene and protein levels. Moreover, CUR down-regulates key regulatory proteins such as NFkB and IL-8 expression thus preventing the inflammatory cascade and possible progression of DCIS into invasive ductal carcinoma. Reduced expression of metastatic molecular marker IL-8 by CUR in 184-B5/HER cells suggests its preventive/therapeutic potential [Support: NIH-NCI CA122394].
Citation Information: Cancer Prev Res 2008;1(7 Suppl):A34.
Seventh AACR International Conference on Frontiers in Cancer Prevention Research-- Nov 16-19, 2008; Washington, DC