Probing the tumorigenic potential of genetic interactions reconstituted in murine fallopian tube organoids

Abstract

Genetically engineered mice have been the gold standard in modeling tumor development. Recent studies have demonstrated that genetically engineered organoids can develop subcutaneous tumors in immunocompromised mice, at least for organs that prefer predominant driver mutations for tumorigenesis. To further substantiate this concept, the fallopian tube (FT), a major cell of origin of ovarian high‐grade serous carcinoma (HGSC), which almost invariably carries TP53 mutations, was investigated for p53 inactivation‐driven tumorigenesis. Murine FT organoids subjected to lentiviral Cre‐mediated Trp53 deletion did not develop tumors. However, subsequent suppression of Pten and simultaneous induction of mutant Pik3ca led to the development of carcinoma in situ and HGSC‐like tumors, respectively, whereas concurrent deletion of Apc resulted in the development of benign cysts, mirroring frequent activation of the PI3K/AKT axis and the marginal impact of Wnt pathway activation in HGSC. Consistent with the frequent activation of the RAS pathway in HGSC, mutant Kras cooperated with Trp53 deletion for the development of tumors, which unexpectedly contained sarcoma cells in addition to carcinoma cells, despite the epithelial origin of the inoculated organoids. This finding is in sharp contrast with the exclusive adenocarcinoma development from gastrointestinal organoids with the same genotype reported in previous studies, suggesting a tissue‐specific epithelial–mesenchymal transition program. In tumor‐derived organoids, the Cre‐mediated recombination rate reached 100% for Trp53 but not for the other genes, highlighting the advantage of p53 inactivation in FT tumorigenesis. The Trp53 wildtype FT organoids expressing the mutant Kras developed sarcoma and carcinoma upon Cdkn2a suppression and Tgfbr2 deletion, respectively, revealing novel pro‐tumorigenic genetic cooperation and critical roles of TGF‐β signaling for epithelial–mesenchymal transition in FT‐derived tumorigenesis. Collectively, the organoid‐based approach represents a shortcut to tumorigenesis and provides novel insights into the relationships among genotype, cell type, and tumor phenotype underlying tumorigenesis. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Two-Way Development of the Genetic Model for Endometrial Tumorigenesis in Mice: Current and Future Perspectives

“…Given the rapid application of organoids and CRISPR/Cas9 technology in many research fields ( Izumiya et al, 2021 ), it is probable that an increasing number of organoid-based models for EC will be developed. However, only a few such models have been documented for FRT organs to date ( Zhang et al, 2019 ; Lohmussaar et al, 2020 ; Maru et al, 2021a ; Maru et al, 2021b ), including ours being the first and only EC model ( Maru et al, 2021a ). Although this study described the development of a novel model for uterine CS, it belongs to a minor category of type II EC, and no organoid-based model for type I EC has been developed so far.…”

“…Intriguingly, the propagation of endometrial organoids was unexpectedly halted after the lentiviral introduction of the pLKO.1puro vector and shLuc (shRNA against luciferase), an empty backbone vector and the negative control shRNA, respectively (Maru et al, 2021a). These phenomena have never been observed in any other tissue-derived organoids under almost the same culture conditions (Onuma et al, 2013;Ochiai et al, 2019;Matsuura et al, 2020;Maru et al, 2021b). In addition, endometrial organoids with potentially advantageous alterations, such as Cre-mediated Kras G12D induction or shRNA-mediated Pten knockdown, continued to proliferate over many passages after lentiviral infection.…”

“…Therefore, these findings point toward the notion that these models could, at least partly, substitute and complement GEMs in evaluating the pathological relevance of reconstituted genetic interactions. Ex vivo/in vivo hybrid carcinogenesis models using murine FT organoids have been recently described ( Maru et al, 2021b ). Although Trp53 loss alone is not sufficient for tumor development in FT organoids, the concurrent introduction of common genetic aberrations in ovarian high-grade serous carcinoma leads to the development of tumors of various grades and histological features.…”

Organoids: A New Chapter in Sarcoma Diagnosis and Treatment

“…Maru et al investigated the transformation potential of the combination of Kirsten rat sarcoma virus ( Kras ) activation and Phosphatase and tensin homolog ( Pten ) inactivation in murine endometrial organoids in the subcutis of immunodeficient mice, and reported that Cyclin-Dependent Kinase Inhibitor 2A ( CDKN2A ) knockdown or transformation-related protein 53 ( Trp53 ) deletion led to the induction of sarcomatous differentiation and, consequently, to the development of uterine carcinosarcoma [ 30 ]. The Japanese study group also developed Trp53 wildtype fallopian tube organoids expressing the mutant Kras , that were found to develop ovarian carcinosarcoma upon CDKN2A suppression [ 31 ]. McCorkle et al successfully established in vitro monolayer and ovarian carcinosarcoma organoid cell lines to investigate the effects of diverse chemotherapeutic agents.…”

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“…This finding was in line with the notion that Kras WT competes with Kras G12D , thereby acting as a relative tumor suppressor. Deletion of the Kras WT allele was frequently observed in Kras-driven tumorigenesis in the oviduct [7] and endometrial organoids [8]. These findings suggest that cells with hyperactive Kras pathway are selected in the subcutaneous tissue, in which synergistic effects of Kras G12D with the loss of Trp53 and Kras WT provides a prominent growth advantage.…”