Departmental Affiliation and City, State, Zip for All Authors

College of Natural Sciences, Austin, Texas 78712; Department of Pharmacology and Neuroscience, Institute for Healthy Aging, Fort Worth, Texas 76107; Department of Pharmacology and Neuroscience, Institute for Healthy Aging, Fort Worth, Texas 76107

Scientific Abstract

After skin cancer, breast cancer is the most common cancer diagnosed in women, with an estimated 237,000 diagnoses of breast cancer annually. Whereas the treatment of breast cancer depends on the kind of breast cancer and its stage (e.g., how far it has spread), hormonal therapy, such as with the use of the estrogen receptor partial agonist/antagonist, tamoxifen, is often used (after surgery and chemotherapy/radiation therapy) to prevent residual cancer cells, that express hormone (e.g., estrogen) receptors, from proliferating and thus causing a recurrence of the cancer. However, not all breast cancer cells express the estrogen receptor (ER), and in one variant of breast cancer termed, “Triple Negative Breast Cancer (TNBC)”, these cells lack three targetable/druggable factors (ERs, progesterone receptors (PRs), and Human Epidermal Growth Factor Receptor 2(HER-2)), thus making the cancer difficult to treat. However, some cells that are termed TNBC, may express ER-beta. Furthermore, tamoxifen has been shown to have some efficacy in certain TNBC cells. Here we determined if indeed tamoxifen can influence the viability of TNBC cells, and based on the work in our lab implicating the role of let-7i and Pgrmc1 on regulating hormone-induced cell viability, assessed if over-expressing let-7i enhanced the cytotoxicity of tamoxifen. Our data show that let-7i does indeed enhance the cytotoxicity of tamoxifen in breast cancer cells, including TNBC cells, and suggests the utility of let-7i as a novel adjuvant for hormone receptor-expressing and TNBC cancers.

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LET7I AS AN ENHANCER OF THE EFFICACY OF TAMOXIFEN IN TRIPLE NEGATIVE BREAST CANCER CELL LINES

After skin cancer, breast cancer is the most common cancer diagnosed in women, with an estimated 237,000 diagnoses of breast cancer annually. Whereas the treatment of breast cancer depends on the kind of breast cancer and its stage (e.g., how far it has spread), hormonal therapy, such as with the use of the estrogen receptor partial agonist/antagonist, tamoxifen, is often used (after surgery and chemotherapy/radiation therapy) to prevent residual cancer cells, that express hormone (e.g., estrogen) receptors, from proliferating and thus causing a recurrence of the cancer. However, not all breast cancer cells express the estrogen receptor (ER), and in one variant of breast cancer termed, “Triple Negative Breast Cancer (TNBC)”, these cells lack three targetable/druggable factors (ERs, progesterone receptors (PRs), and Human Epidermal Growth Factor Receptor 2(HER-2)), thus making the cancer difficult to treat. However, some cells that are termed TNBC, may express ER-beta. Furthermore, tamoxifen has been shown to have some efficacy in certain TNBC cells. Here we determined if indeed tamoxifen can influence the viability of TNBC cells, and based on the work in our lab implicating the role of let-7i and Pgrmc1 on regulating hormone-induced cell viability, assessed if over-expressing let-7i enhanced the cytotoxicity of tamoxifen. Our data show that let-7i does indeed enhance the cytotoxicity of tamoxifen in breast cancer cells, including TNBC cells, and suggests the utility of let-7i as a novel adjuvant for hormone receptor-expressing and TNBC cancers.

Manuscript Number

1032