In Vitro Assessment of ABJ-1-195, a Novel BRCA1-Mimetic Drug, in Breast Cancer Cells
Poster #: 168
Session/Time: A
Author:
Devra Catarena Athanasiadis, BS
Mentor:
Kan Wang, MD
Research Type: Basic Science
Abstract
INTRODUCTION:
To expand treatment opportunities and drug discovery for drug-resistant breast cancers, this study conducts in vitro assessments of a novel BRCA1-mimetic drug, termed ABJ-1-195, using breast cancer model cell lines. Breast cancers are classified by the presence or absence of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2). In cancers that are ER positive, there has been a development of resistance to treatments such as Tamoxifen, which utilizes the estrogen receptor pathway as its mechanism of action. BRCA1 (breast cancer susceptibility gene 1), a tumor suppressor involved in DNA repair and estrogen receptor alpha (Erα) regulation, can lose function due to mutation. ABJ-1-195, as a BRCA1 mimetic, is designed to overcome resistance to therapies like tamoxifen, an estrogen antagonist. Tamoxifen treats ER-positive cancers but develops resistance over time, as demonstrated in the cell line LCC9, which proliferates independently of estrogen. ABJ-1-195 in vitro efficacy is assessed using cancer cell lines to model ER-positive cancers. This study aims to evaluate the efficacy of ABJ-1-195 as a BRCA1 mimetic in Tamoxifen-sensitive and in ER-resistant breast cancer models.
METHODS:
Three ER-positive breast cancer cell lines, MCF-7, LCC9, and T47D, were used to evaluate ABJ-1-195. MCF-7 and T47D are estrogen-sensitive, while LCC9 models cancer with active ERα and tamoxifen resistance. T47D cells stably expressed a luciferase gene under estrogen response elements (EREs), enabling real-time monitoring of ERα transcriptional activity. Cells were treated with ABJ-1-195 at concentrations ranging from 0.01 to 10 μM for 3 to 10 days under various conditions: drug alone, drug with 10 nM estradiol (E2), E2 alone, and no treatment. All treatments were replicated for statistical accuracy. Luminescence, measured via dual-luciferase assay to analyze ABJ-1-195's anticipated disruption of ERα signaling. Cell viability and proliferation were assessed using the MTT assay, with absorbance measured spectrophotometrically to evaluate growth inhibition. Total RNA was extracted post-treatment, reverse-transcribed, and analyzed using TaqMan qPCR targeting Cathepsin D, a protease linked to tumor growth and poor prognosis. GAPDH (glyceraldehyde-phosphate-dehydrogenase) was used as an internal control, enabling quantitative analysis. The integration of functional and molecular assays enabled a comprehensive evaluation of ABJ-1-195, focusing on its effects on viability, hormone response, and the expression of genes associated with metastasis.
RESULTS:
Results across LCC9, MCF-7, and T47D cell lines indicate that ABJ-1-195 reduces viability in a concentration-dependent manner in the presence of E2, consistent with BRCA1-like tumor suppression. Ongoing qPCR in the MCF-7 model is expected to show downregulation of the target gene in the presence of the drug with E2 treatment. Expression of the GFP protein in MCF-7 cells, achieved through plasmid transfection, enabled us to track motility and study proliferation in different types of mixed cell organoids. These findings are early and ongoing data collection aims to further characterize ABJ-1-195's therapeutic potential.
CONCLUSION:
The data obtained support ABJ-1-195 as a BRCA1-mimetic that reduces proliferation in endocrine-resistant breast cancer via tumor-suppressive pathways, validating a new ERα antagonist class with a mechanism to overcome treatment resistance, and laying the groundwork for future development.
To expand treatment opportunities and drug discovery for drug-resistant breast cancers, this study conducts in vitro assessments of a novel BRCA1-mimetic drug, termed ABJ-1-195, using breast cancer model cell lines. Breast cancers are classified by the presence or absence of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2). In cancers that are ER positive, there has been a development of resistance to treatments such as Tamoxifen, which utilizes the estrogen receptor pathway as its mechanism of action. BRCA1 (breast cancer susceptibility gene 1), a tumor suppressor involved in DNA repair and estrogen receptor alpha (Erα) regulation, can lose function due to mutation. ABJ-1-195, as a BRCA1 mimetic, is designed to overcome resistance to therapies like tamoxifen, an estrogen antagonist. Tamoxifen treats ER-positive cancers but develops resistance over time, as demonstrated in the cell line LCC9, which proliferates independently of estrogen. ABJ-1-195 in vitro efficacy is assessed using cancer cell lines to model ER-positive cancers. This study aims to evaluate the efficacy of ABJ-1-195 as a BRCA1 mimetic in Tamoxifen-sensitive and in ER-resistant breast cancer models.
METHODS:
Three ER-positive breast cancer cell lines, MCF-7, LCC9, and T47D, were used to evaluate ABJ-1-195. MCF-7 and T47D are estrogen-sensitive, while LCC9 models cancer with active ERα and tamoxifen resistance. T47D cells stably expressed a luciferase gene under estrogen response elements (EREs), enabling real-time monitoring of ERα transcriptional activity. Cells were treated with ABJ-1-195 at concentrations ranging from 0.01 to 10 μM for 3 to 10 days under various conditions: drug alone, drug with 10 nM estradiol (E2), E2 alone, and no treatment. All treatments were replicated for statistical accuracy. Luminescence, measured via dual-luciferase assay to analyze ABJ-1-195's anticipated disruption of ERα signaling. Cell viability and proliferation were assessed using the MTT assay, with absorbance measured spectrophotometrically to evaluate growth inhibition. Total RNA was extracted post-treatment, reverse-transcribed, and analyzed using TaqMan qPCR targeting Cathepsin D, a protease linked to tumor growth and poor prognosis. GAPDH (glyceraldehyde-phosphate-dehydrogenase) was used as an internal control, enabling quantitative analysis. The integration of functional and molecular assays enabled a comprehensive evaluation of ABJ-1-195, focusing on its effects on viability, hormone response, and the expression of genes associated with metastasis.
RESULTS:
Results across LCC9, MCF-7, and T47D cell lines indicate that ABJ-1-195 reduces viability in a concentration-dependent manner in the presence of E2, consistent with BRCA1-like tumor suppression. Ongoing qPCR in the MCF-7 model is expected to show downregulation of the target gene in the presence of the drug with E2 treatment. Expression of the GFP protein in MCF-7 cells, achieved through plasmid transfection, enabled us to track motility and study proliferation in different types of mixed cell organoids. These findings are early and ongoing data collection aims to further characterize ABJ-1-195's therapeutic potential.
CONCLUSION:
The data obtained support ABJ-1-195 as a BRCA1-mimetic that reduces proliferation in endocrine-resistant breast cancer via tumor-suppressive pathways, validating a new ERα antagonist class with a mechanism to overcome treatment resistance, and laying the groundwork for future development.