Abstract 2489: Study the efficacy of hypomethylating agent in treating regular and brain metastasized HER2-positive breast cancer
Authors: Liu Tuoen , Butler Christopher , Donoughe Kelsey , Forchette Lauren , Sebastian William , Szalai Gabor , Lockman Paul 
Published: April 2023

Abstract
Breast cancer is the second leading cause of cancer with the highest mortality rate in females in the United States. Late stage breast cancer can metastasize to different locations of the body, and patients with brain metastasis have a poor prognosis and short survival time. HER2-positive breast cancer, composed of ~15-20% of total cases, is aggressive with unfavorable clinical outcomes. Although HER2-targeted therapies are available, they are mostly ineffective against brain metastasis. To study tumor metastasis, we had established the breast cancer brain metastasis preclinical cell and mouse models. Our previous study has shown that the hypomethylating agent azacitidine (AZA) is effective in treating brain metastasis triple-negative breast cancer using in vitro cell and in vivo mouse models. Thus, we hypothesized that AZA will be effective to treat HER2-positive breast cancer. To test our hypothesis, we treated regular (JIMT-1) and brain metastasized (JIMT-1 Br) HER2-positive breast cancer cell lines with various concentrations of AZA, and the IC50 values, cell proliferation, and apoptosis were measured. Our results showed that train metastasized HER2-positive breast cancer JIMT-1 Br cells have similar growth rate compared to their parental regular breast cancer JIMT-1 cells. Regular breast cancer cells are more sensitive to AZA treatment, supported by (1) The IC50 value of AZA in JIMT-1 cells is significantly lower than that in JIMT-1 Br cells; (2) 72 hours of AZA treatment significantly inhibited cell grow in both cell lines, and the inhibition of JIMT-1 growth is greater than that of JIMT-1 Br cells; (3) AZA triggered apoptosis in both cell lines in a dose-dependent manner; (4) Higher concentrations of AZA induced a higher percentage of cell apoptosis in JIMT-1 compared to JIMT-1 Br cells. AZA treatment does not significantly change the expression of metastasis protein markers in either cell line. Epithelial-mesenchymal transition promotes cancer cell invasion and metastasis. Epithelial markers include cytokeratins and E-cadherin, and mesenchymal markers include N-cadherin and vimentin. We measured the expression of those markers in both cell lines after AZA treatment by Western blotting, and found that the expression of pan-cytokeratins and keratin 18 were equivalent between both cell lines upon AZA treatment. However, the expression of keratin 19, E-cadherin, N-cadherin, and vimentin were not detected in either cell line. In conclusion, in this study, we tested the in vitro effects of the hypomethylating agent AZA in both regular and brain metastasized HER2-positive breast cancer cells. We found that AZA inhibits cell growth and promotes apoptosis in both cell types, but the regular breast cancer cells are more sensitive to AZA treatment compared to brain metastasized cells, shown by the differences in IC50 values and extents of cell growth inhibition and apoptosis induction.
Citation Format: Tuoen Liu, Christopher Butler, Kelsey Donoughe, Lauren Forchette, William Sebastian, Gabor Szalai, Paul Lockman. Study the efficacy of hypomethylating agent in treating regular and brain metastasized HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2489.