Evaluation of Sensitivity of Two Triple Negative Breast Cancer Cell Lines to 2, 3‐ dichloro‐5, 8‐dimethoxy‐1, 4‐naphthoquinone and 4 Hydroxy‐Tamoxifen

Abstract

Breast cancer (BC) is a heterogeneous disease and it is one of the leading causes of mortality worldwide in women each year. However, in the United States, there is a disparity in survival between African American (AA) and Caucasian women with AA women having a higher rate of mortality. BC is typically classified based on the expression of the following receptors: Estrogen receptor α (ERα), Progesterone receptor (PR) and Human Epidermal Growth Factor Receptor 2 (HER2). Conventional treatment for BC relies on the expression of ERα for anti‐estrogenic therapy and HER2 for HER2 inhibition. Triple negative breast cancer (TNBC) is a form of breast cancer which lacks expression of ERα, PR and HER2 and affects minority population disproportionately. Potential mechanisms for the loss of ERα expression include hyperactivation of MAPK pathways due to EGFR or HER2 overexpression, estrogen withdrawal, hypoxia and methylation of the CpG island, cytosine‐guanine abundant area, on the ER gene promoter region. Due to lack of targetted treatment for TNBC, alternative treatment options are essential to increase patient survivability. 2, 3‐ dichloro‐5, 8‐dimethoxy‐1, 4‐naphthoquinone (Z285), a 1,4 napthoquinone analog, has demonstrated cytotoxic effects in estrogen positive and estrogen negative cell lines. Previous in silico data showed that this compound may function as an MAPK allosteric inhibitor. MCF7 cells were used as an ERα positive control and two TNBC cell lines, HCC1806, from a AA woman, and MDA MB 231, from a Caucasian woman, were used. Cell viability studies were carried out on cells treated with Z285 alone (0.5–10μM), 4 Hydroxy‐Tamoxifen (4OH‐Tam) alone (3–30μM) for 24,72 and 120hrs. In combination studies, the cells were pretreated with Z285 (2 or 5μM) for 6 hrs followed by 4OH‐Tam (1–15μM) for 24, 72 and 120hrs. These results showed a dose and time‐dependent response with individual treatment. Combinatory studies showed significant decreases in cell viability when compared to individual studies. Cells were treated with 5 μM Z285 and mRNA was collected for RNA microarray analysis to determine changes in mRNA expression profile. These results showed modulation of several genes involved in the MAPK pathway and suggest a mechanism of increased sensitivity of the TNBC cells to 4OH‐Tamoxifen. Therefore, this novel compound which targets the MAPK pathway may offer a model for treating TNBC breast cancers by reactivating ERα expression in these cancers and thus rendering them susceptible to anti‐estrogen therapy.Support or Funding InformationCharles and Mary Latham FundThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.