Decreased Cell Proliferation with 2, 3‐ Dichloro‐5, 8‐Dimethoxy‐1, 4‐Naphthoquinone and 4‐Hydroxy Tamoxifen in Triple Negative Breast Cancer Cell Lines

Abstract

Triple negative breast cancer (TNBC) is a subtype of breast cancer (BC) that makes up 10–15% of BC diagnosis. This form of the disease disproportionately affects African American (AA) women as compared to women of other ethnicities. TNBC is classified by lack of expression of three receptors: Estrogen alpha (ERα), progesterone (PR) and human epidermal growth factor 2 (HER2). These receptors are used as therapeutic targets for BC that express them. As specific targets are not present, surgery, radiation and chemotherapy have been the mainstay of therapy for TNBC. Recently, newer drugs have become available based on specific genetic and epigenetic mutations like BRCA1, however more treatment options need to be produced to reduce the mortality rate in this disease. A novel compound, 2, 3‐dichloro‐5, 8‐dimethoxy‐1, 4‐naphthoquinone (Z285) belongs to the class of naphthoquinones that demonstrate activities as anticancer, antimalarial, and antibacterial compounds. These compounds have also been shown to cause an increase in reactive oxygen species (ROS) production as well as affect signaling pathways associated with epidermal growth factor receptor (EGFR). Moreover, it has been reported that treatment with tamoxifen can cause cell death. This is based on the accumulation of the drug and its active metabolites within cells that may cause an increase in the ROS production ultimately leading to cellular death, even in ERα negative cell lines. In the current study, three triple negative cell lines, HCC1806, MDA MB 231 and HS578T were used. These cells were treated with Z285 and 4‐hydroxy tamoxifen (4OH‐Tam) for 24 or 72hr with 1, 2, 4, 8, 16μM and 3, 6, 12, 24, 48μM respectively. Synergestic activity was demonstrated using SynergyFinder as well as the Chou‐Talalay method (CompuSyn). In other experiments, cells were treated with the IC50 of Z285 which was established in prior experiments. mRNA and protein were isolated between 6 and 24hr. Results showed alterations of several mRNA in response to these treatments. In addition, there were modifications to Nrf2 protein concentration, a transcription factor associated with oxidative stress. Therefore, these results indicate that combination treatment of Z285 and 4OH‐Tam induce cell death at lower concentrations. Thus this novel compound which causes an increase in ROS in these TNBC cells, may render them more susceptible to tamoxifen therapy. Support or Funding Information Charles and Mary Latham Fund