Abstract 2169: Metastases of a temozolimide-sensitive patient-derived melanoma xenograft model show distinct biologic features and developed resistance against temozolomide
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. 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 patho-histological examination. Furthermore, whole exome sequencing and RNAseq data of primary PDX and its metastases are available. Two out of the three sublines have corresponding cell lines for 2D and 3D testing. 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 cell lines established in 2D 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 day (spleen metastasis, MEXF 2090S) and 19.01 days doubling time for the liver metastasis model (MEXF 2090L). MEXF 2090S thereby depicted the slowest growth rate in our melanoma PDX panel (24 models, 10.09 days mean doubling time). The patho-histological examination revealed a well differentiated melanoma with low stroma content (3-5%) in all three lines. The molecular analysis (whole exome sequencing) identified distinct differences. Nevertheless, the potential driver mutations, Tp53 (R213Q) and Nras (Q61K), were recognized in all investigated samples. Temozolomide was applied to all three lines in vivo. 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. 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. Metastases of a temozolimide-sensitive patient-derived melanoma xenograft model show distinct biologic features and developed resistance against temozolomide [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2169.