Triple negative breast cancer (TNBC) is a classification given to breast cancers that do not express estrogen receptor or progesterone receptor and don’t overexpress HER2. The lack of hormone receptors mean TNBC can’t be treated with anti-estrogens like Tamoxifen, and the lack of HER2 overexpression means Herceptin treatment is also ineffective. TNBC is therefore one of the hardest cancers to treat and has a lower survival rate than other breast cancer types. It also disproportionately affects African American women even though breast cancer is more prevalent in white women overall. This difference in occurrence between women with different skin tone led us to investigate the effect of Vitamin D on treatment in TNBC. The hypothesis was that Vitamin D3 would cause greater efficacy of the drug paclitaxel, which is commonly used to treat breast, ovarian, and uterine cancer. We used the TNBC cell lines DU4475 and MDA-MB-231. DU4475 has active p53 protein, while MDA-MB-231 does not. The cells were treated with Vitamin D3 (either 25-OH vitamin D3 or 1,25(OH)2 Vitamin D3) for 3 days, then varying concentrations of paclitaxel for 5 days, after which the viability of the cells was measured using CellTiter-Glo®. The studies were done in media with stripped serum to ensure an accurate concentration of Vitamin D3. Our results indicate that the difference in the IC50 of paclitaxel with and without Vitamin D3 was negligible in both cell lines, indicating the Vitamin D3 had no effect on the efficacy of paclitaxel. This is in contrast to previously published reports using MDA-MB-231 in cells pre-treated with Vitamin D3.

Effect of vitamin D3 on paclitaxel potency in triple negative breast cancer cell lines

255th National Meeting (2018)

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