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35 Repeated short-term in vitro carboplatin exposure of patient-derived ovarian cancer organoids promotes platinum resistance
  1. Juliane Reichenbach,
  2. Sophia Hierlmayer,
  3. Anca Chelariu Raicu,
  4. Tingyu Zhang,
  5. Fabian Kraus,
  6. Bastian Czogalla,
  7. Sven Mahner,
  8. Fabian Trillsch and
  9. Mirjana Kessler
  1. Department of Gynecology and Obstetrics, Ludwig-Maximilian-University Munich, Munich, Germany


Introduction/Background Translational approaches with appropriate experimental models are required to understand the mechanisms of platinum resistance in the highly variable disease of high-grade serous ovarian cancer (HGSOC). Our biobank with a cohort of more than 200 patient-derived HGSOC organoids (PDOs) enables the functional study of patient-specific platinum responses and PDO long-term expansion potential after in vitro carboplatin exposure by our developed Organoid Forming Efficiency (OFE) Test.

Methodology The regeneration potential of PDOs from different HGSOC patients, further characterized by their respective clinical platinum response and tumor mutational profile, was assessed by OFE-Test after repeated short-term in vitro exposure to carboplatin (48 hours) followed by a recovery phase and quantification of OFE. Transcriptional and signaling response to carboplatin challenge was investigated both in the acute treatment phase as well as in long-term expanding organoids post platinum exposure. The impact of Keratin 17 (KRT17) on this process of resistance phenotype acquisition was assessed by CRISPR-Cas9-mediated gene editing of organoids.

Results We observe inter-individual differences in platinum response across PDOs corresponding with the respective clinical response. Repeated short-term challenge of pretreated PDOs to carboplatin leads to an altered, more resistant, but stable phenotype in subsequent passages, as quantified by OFE-Test. CRISPR-Cas9-mediated gene editing of the possible response regulator KRT17 resulting in a truncated version of the protein, leads to a highly resistant phenotype that remains viable even at the highest carboplatin concentrations.

Conclusion In this study, increasing acquired resistance after repeated platinum exposure of HGSOC organoids, strongly suggests that this is a suitable in vitro model to study the origins of platinum resistance. KRT17 is identified as a potential regulator of carboplatin exposure with a dramatic shift in platinum sensitivity after genomic editing. Acquisition of stable resistant properties in organoids after short carboplatin treatment is indicative of the existence of underlying epigenetic mechanisms that mediate reprogramming.

Disclosures F.T. received research funding, advisory board, honoraria, and travel expenses from AstraZeneca, Clovis, Eisai, ImmunoGen, Medac, MSD, PharmaMar, Roche, and Tesaro/GSK. S.M. Received Research funding, advisory board, honorary or travel expenses: AbbVie, AstraZeneca, Clovis, Eisai, GlaxoSmithKline, Hubro, Medac, MSD, Novartis, Nykode, Olympus, PharmaMar, Pfizer, Roche, Sensor Kinesis, Teva, Tesaro.

Abstract 35 Figure 1

Repeated short-term in vitro carboplatin exposure of wildtype and gene-edited patient-derived ovarian cancer organoids promotes platinum resistance

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