Abstract 227: Novel and easy-to-use approach to triple-negative breast cancer tumoroid culture

Abstract Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer diagnoses in the United States. Patients with metastatic TNBC have a low survival rate, driven in part by limited treatment options for the disease. Tumoroids, also known as cancer organoids, have been shown to better maintain tumor-specific mutational and gene expression profiles over long-term culture, and evidence is growing that the functional response of tumoroids to therapeutics better recapitulates in vivo response. These improved preclinical models of TNBC may facilitate the development of new therapies, but tumoroids are yet to be widely adopted due to challenging culture methods. In this study, we show that two TNBC tumoroid models publicly available through the National Cancer Institute Patient-Derived Models Repository can be expanded in suspension culture using Gibco™ OncoPro™ Tumoroid Culture Medium supplemented with FGF10 and beta-estradiol. We compared the bulk tumoroid morphologies, growth rates, maintenance of mutational and gene expression profiles, and molecular phenotypes of cells grown in the NCI-recommended medium in embedded culture, and the OncoPro medium in embedded culture and suspension culture. We saw comparable morphologies and growth rates in all culture conditions. A multivariate analysis of the allelic frequencies of single nucleotide variants and ploidy values of copy number variants for cells expanded in all experimental conditions revealed 95% and 88% correlation, respectively, with the initial material. Interestingly, despite the change in the medium formulation, gene expression was also highly correlated between the initial material and the OncoPro medium conditions for 20, 000 RefSeq genes (Pearson r0. 94) and for a cancer-gene specific panel of 1, 423 genes (r0. 87). Further analysis showed unchanged expression levels in 97% of total genes analyzed and the basal molecular subtype was maintained for both lines in all conditions. The OncoPro media system was also used to derive a new TNBC tumoroid line, which demonstrates consistent growth rate and maintains the patient-specific mutational profile of the original breast tumor. Differential gene expression analysis revealed that changes in the gene expression profile were largely due to the loss of non-malignant cell populations from the original tumor. Finally, we utilized this new tumoroid line to examine donor-specific killing efficiencies of primary natural killer cells in a co-culture experiment. The discrepancy in the dynamics of killing a tumoroid line versus the standard K562 cell line indicates that tumoroids may offer an improved approach for screening new cell therapies. In summary, the easy-to-adopt OncoPro medium and culture method does not change the characteristics of existing models and may be used to derive new tumoroid lines, both of which can be leveraged for preclinical studies to develop critical new therapies for TNBC. Citation Format: Brittany Balhouse, Chris Yankaskas, Colin Paul, Shyanne Salen, Sylvia Beam, Pradip Shahi Thakuri, Matt Dallas, David Kuninger. Novel and easy-to-use approach to triple-negative breast cancer tumoroid culture abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 227.