Impact of baseline culture condition on the growth and treatment response of mouse derived cancer organoidsAuthors: Autumn Olson, Rebecca A. DeStefanis, Alyssa DeZeeuw, Samantha Anderson, Gioia Sha, Jeremy Kratz, Cheri Pasch, Linda Clipson, Dustin A. DemingIntroduction: Colorectal cancer (CRC) is a leading cause of cancer related deaths and there has been an increased focus on developing therapies targeted to the mutational profile of individual patients. Mouse derived cancer organoids (MDCOs) are used as a model for therapeutic drug testing. How the culture conditions can impact the determination of treatment response from MDCOs has been understudied and is the focus of these investigations. Here, we examine how baseline size, passage number, plating density, location within the Matrigel droplet, and lineage impact MDCO growth and treatment response.Methods: CRC MDCOs were derived from multiple tumors across several Apc and Pik3ca mutant mice (Fc1 Apcfl/+ Pik3caH1047R/+) totaling 3,152 individual MDCOs. Untreated MDCO growth was analyzed across 902 MDCOs. Additionally, the PI3K pathway inhibitors, AZD2014, Everolimus, BEZ235, MLN0128, Palbociclib, and Copanlisib were analyzed across 2,250 MDCOs. In each study, baseline brightfield images of the MDCOs were taken and following 48 hours. Individual MDCOs were evaluated for the impact of baseline size, passage number (passage 1-15), plating density, location within the Matrigel droplet, and the generation of MDCOs across different mice on MDCO growth and treatment response. A change point analysis was used to assess the impact of baseline size. The percent relative change in diameter over 48 hours was compared to each other culture condition by calculating an R2 value.Results: A change in the organoid baseline growth rate was observed if the MDCOs were greater than 0.373 mm in baseline was identified. There were no significant differences in growth due to changes in the other culture conditions for the untreated MDCOs. The R2 values comparing the percent relative change in diameter over 48 hours to the culture conditions of passage number, plating density, location within the Matrigel droplet, and from which mouse the MDCOs were derived from were 0.0103, 0.0243, 0.0001, and 0.0295, respectively. There were no significant differences in the response to PI3K pathway inhibition of the MDCOs related to passage number, plating density, location within the Matrigel droplet, and from which mouse the MDCOs were derived from (R2 values: 0.1174, 0.0979, 0.0221, and 0.1267, respectively).Conclusions: Mouse derived cancer organoids are a useful tool in modeling drug response of cancers with specific mutational profiles. While the baseline size of MDCOs can change the growth rate, the growth rate and treatment response of MDCOs is not impacted by the passage number, plating density, location within the Matrigel, and from which mouse the MDCOs were derived.

Citation Format: Autumn Olson, Rebecca A. DeStefanis, Alyssa DeZeeuw, Samantha Anderson, Gioia Sha, Jeremy Kratz, Cheri Pasch, Linda Clipson, Dustin A. Deming. Impact of baseline culture condition on the growth and treatment response of mouse derived cancer organoids [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 2969.