Melanoma Cell Lines Derived From Patient Derived Xenografts (Pdx) Can Contain Murine Chromosomes Resultant From Cell Fusions.

Abstract Introduction: Patient Derived Xenografts (PDX) provide a distinct platform to generate in vivo and ex vivo cell lines to investigate novel therapies. However, human-murine cell fusions may skew the models and is a poorly characterized phenomenon. Methods: Malignant melanoma IRB-consented biopsies [IRBs: 17-000548; 17-001685; 17-001351; 11-003254] were excised from various sites and implanted into gender-matched 4-6 weeks old NOD-scid IL2Rgammanull mice. Tumor-bearing mice were humanely euthanized and adherent cell lines were generated after Miltenyi gentleMACS™ dissociation of the PDXs. Briefly, adherent cells are allowed to proliferate and passaged when 70% confluent for approximately 4-8 weeks. PDX-derived cell products were processed for long term-cryostorage and an aliquot was sent for GenePrint 10 System-Promega®-LaragenTM cell line authentication paired with patient-matched peripheral blood mononuclear cells (PBMC) for specimen congruency. Mouse-genome contaminant resulting cultures were prepared and sent for cell line characterization by G-banded metaphase karyotyping-Cell Line GeneticsTM. Cultures containing murine karyotypes were processed according to manufacturer recommendations by Miltenyi Mouse Cell Depletion KitTM where the flow through (negative fraction) represents the human-cell fraction. Results: We implanted 86 patient-derived biopsies into mice over 3years, from which 39 [45%] resulted in progressively growing PDXs. From these PDXs we have generated 26 [37%]-patient-specific PDX-derived cell lines. G-banded metaphase karyotyping demonstrated that 6 [24%]- cell lines presented murine chromosome contamination. The immunoprofile of these 6 cellular materials appear to be murine as the totality of the cultures were sequestered in the column by mouse depletion cell cocktail. Separation assay was validated by bonafide human cell lines, utilized as human positive controls, M257 and MX210 both with human karyotypes and matched Cell ID profiling. The murine colon carcinoma cell line MC38, was utilized as a positive murine control, and performed identically as the 6 PDX-derived cellular materials with abnormal mouse genomes. Conclusion: Detection of murine-human fusion cells in cell lines derived from PDXs may limit the utility of these models. Citation Format: Agustin Vega-Crespo, Ignacio Baselga-Carretero, Ivan Perez-Garcilaso, Sameeha Jilani, Kevin Chen, Vaneet Khullar, Egmidio Medina, Yaroslav Teper, Antoni Ribas, Begoña Comin-Anduix. Melanoma cell lines derived from patient derived xenografts (PDX) can contain murine chromosomes resultant from cell fusions [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 3006.