Abstract 2125: Roles of KAT6A and KAT6B in the biology of estrogen positive breast cancer

Abstract KAT6A and KAT6B are histone acetyl transferase (HAT) that are controlling gene expression by transferring acetyl groups to histones. Yu et al (Oncogene, 2017 36, 2910-2918) have shown that KAT6A has a role in breast cancer development by activating the ERα promoter and was found frequently amplified in 11% and is overexpressed in 15% of breast cancers. Altogether, these data support KAT6A as an attractive target in estrogen receptor driven breast cancer. KAT6B is a close homolog that shares 91% identity in the acetyl coA binding site. While the prevalence of gene amplification for KAT6B in breast cancer is only 1-2%, it is often overexpressed. In this study, we are exploring how KAT6A and KAT6B are contributing to ERα expression and the growth of KAT6A amplified breast cancer cell lines. To decipher each protein's role, we have designed specific siRNA against KAT6A and KAT6B and we tested their action either individually or in combination in the KAT6A gene amplified breast cancer cell lines T-47D, CAM-1 and ZR-75. Following treatment of T-47D, CAMA-1 and ZR75 cell lines with KAT6A or B siRNA we observed a decrease of ERα gene and protein expression for all siRNAs. The effect was more pronounced when using KAT6A over KAT6B and the effect of both siRNA A/B were additive. Phenotypically, the impact on cell line proliferation by applying clonogenic and incucyte assays, mirrors what is observed on ERα gene and protein expression. The effect on cellular proliferation of KAT6A is more prominent than KAT6B silencing, while the combined KAT6A + KAT6B silencing being more impactful than KAT6A silencing alone. In conclusion, our data show that KAT6A and KAT6B share similar function in the control of ER gene and protein expression. This study suggests that KAT6A and KAT6B may be paralogs, one compensating for the loss of the other. This translates into a more pronounced antiproliferative effect when both genes are silenced concomitantly. Citation Format: Isabelle Meaux, Dimitri Gorge-Bernat, Angele Paz, Catherine Geslin, Laurent Debussche, Jürgen Moll, Christophe Henry. Roles of KAT6A and KAT6B in the biology of estrogen positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2125.