Abstract A019: Establishment and characterization of a melanoma patient-derived xenograft model comprising three different sublines with distinct biologic features
Authors: Klingner Kerstin , Lenhard Dorothee , Simon Elke , Peille Anne-Lise , Schüler Julia 
Published: August 2018

Abstract
Patient-derived tumor xenografts (PDX) play a major role in the development of new cancer therapies and their strengths and weaknesses have gradually been elucidated. Large panels of solid cancer PDX are available to screen innovative compounds, identify new targets, and study tumor biology. In the current study we established a melanoma PDX from donor patient tissue. In addition, we were able to create two sublines from spontaneous metastases occurring in the murine host during the establishment phase of the original model. All three lines were characterized by tumor growth kinetics, antitumoral activity against standard-of-care temozolomide, and pathohistologic examination. Furthermore, molecular examination of primary PDX and its metastases is under way as well as cell line establishment. The PDX model was developed from a biopsy of a 68-year-old woman undergoing surgery due to a non-pretreated melanoma. After seven subcutaneous passages in immune-compromised mice, individual animals showed tumor growth in the liver as well as the spleen. We were able to passage and characterize those metastases in parallel to the original model. The human origin of the lines as well as one cell line established in 2D from the primary PDX was confirmed by str-analysis. All three in vivo lines depicted distinct growth kinetics: The doubling times varied significantly (Kruskal-Wallis, p&lt; 0.0018) between 12.34 days (primary tumor, MEXF 2090P) and 30.78 days (spleen metastasis, MEXF 2090S) and 19.01 days doubling time for the liver metastasis model (MEXF 2090L). The pathohistologic examination revealed a well-differentiated melanoma with low stroma content (3-5%) in all three lines. The molecular analysis (whole exome sequencing) is ongoing. So far the primary tumor has been characterized and two potential driver mutations, Tp53 (R213Q) and Nras (Q61K), were recognized. To characterize the models in more detail, temozolomide was applied to all three lines. 6 mice per group and line were treated either with temozolomide (40 mg/kg/d, iv, twice a week for three weeks) or the control vehicle (10% DMSO, 90% NaCl). The primary tumor depicted statistically significant antitumoral activity with a T/C (test vs control) value of 36% (p&lt; 0.05, t test, two-tailed) two weeks after the last treatment (experiment day 32). The two lines derived of metastases were resistant against the alkylating agent, depicting T/C values of 76% (2090L) and 79% (2090S), respectively. Further characterization of the PDX model and its different sublines will help to elucidate the resistance mechanism behind these data. Spontaneous metastases are a rare event in PDX models growing subcutaneously in NMRI nude mice. Thus, shedding some light into the biology of the metastatic event in the current model will help to understand and influence the metastatic process in general. In any case, those lines can serve as indispensable tools in the oncology drug development pipeline.
Citation Format: Kerstin Klingner, Dorothee Lenhard, Elke Simon, Anne-Lise Peille, Julia Schüler. Establishment and characterization of a melanoma patient-derived xenograft model comprising three different sublines with distinct biologic features [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A019.