LAUSR

268Background: 3D organoid culture, especially that generated from patient samples, is becoming prevalent as 2D cell culture models fail to provide clinical relevance. However, a relatively large amount of starting tissue is still required for this process, and the turnover rate and overall success rate vary greatly if relying solely on spontaneous aggregation. Methods: Here, we report the successful use of magnetic 3D bioprinting to drive organoid formation derived from fresh tumor samples of patients with prostate cancer, renal cell cancer, and urothelial cancer. Results: Only milligrams to tens of milligrams of starting tissues (from fine-needle biopsies, core biopsies, or surgical excision) were used. Most organoids formed overnight, with a very high overall success rate ( > 95%, n = 25). We have demonstrated that these cultures can be maintained, passed, and cryopreserved like conventional 2D cultures. More importantly, we characterized the organoids derived from prostatic adenocarcinomas and neuroen...