Inhibition of NF-kB mediated inflammatory response by parthenolide in breast cancer cells
Triple-negative breast cancer (TNBC), indicated by the absence of estrogen, progesterone and human epidermal growth factor receptor 2 (HER2), is the most aggressive form of breast cancer characterized by high rates of metastasis and low survival. Among those diagnosed with TNBC, 34% contain Inhibitor of Growth 4 (ING4) deletion that is associated with poor patient outcomes. We previously showed that ING4 negatively regulates NF-kB in breast cancer. Previous studies show parthenolide, a compound found in feverfew (Tanacetum parthenium) to inhibit NF-kB in prostate, colorectal, and pancreatic cancer. As low ING4 expression is correlated to activation of NF-kB, we hypothesized that parthenolide inhibits cytokine-induced activation of NF-kB in ING4 deficient TNBC cells. To test the hypothesis, the ING4 gene was deleted in MDA-MB 231, a TNBC cell line using a CRISPR/Cas9 system. Inflammatory cytokines were tested against ING4 wildtype and ING4 deleted cells for elicited phosphorylation of NF-kB, proliferation and migration using Boyden chamber assays in the presence or absence of parthenolide. The results showed that TNFa or IL-1b induces phosphorylation of NF-kB regardless of ING4 deletion. Furthermore, we found the optimal working dose of parthenolide, 100nM, to be of no effect on proliferation in the presence or absence of proinflammatory cytokine IL-1b in MDA-MB 231 cells. Parthenolide did not inhibit IL-1b induced phosphorylation of NF-kB regardless of the presence or absence of ING4. However, parthenolide did inhibit nuclear translocation of NF-kB in ING4 deleted cell lines. Parthenolide also inhibited both TNFa induced phosphorylation of NF-kB and migration of ING4 deleted cells to basal level. We conclude that parthenolide is inhibiting TNFa-induced migration in part by inhibiting phosphorylative NF-kB in ING4 deficient cells. The results of this study may show parthenolide to improve patient outcomes in ING4 deleted TNBC.