Abstract 2783: Establishment and characterization of patient-derived xenografts of head and neck tumors.
Authors: Klinghammer Konrad , Raguse Jan D , Siedmann Moritz , Becker Michael , Keilholz Ulrich , Hoffmann Jens , Fichtner Iduna 
Published: August 2014

Abstract
Background-Aims: The introduction of first targeted therapy with Cetuximab has improved survival of head and neck cancer. However there is still a large population with intrinsic resistance. To evaluate the mechanisms and find alternative treatments we started establishing a large panel of patient derived xenografts from head and neck squamous cell carcinomas displaying the heterogeneity of this disease, as cell lines and thereof established xenografts have only a limited value for preclinical drug evaluation and biomarker analysis due to clonal selection and cellular dedifferentiation. Using these models we evaluate new treatment options, identify predictive biomarkers and test the sensitivity of experimental drugs and treatment approaches.
Methods: Specimen from head and neck tumor samples were transplanted subcutaneously to immunodeficient mice within 24 hours. In case of engraftment groups of 5-6 mice were treated after 3rd passage with 5-FU, MTX, Cetuximab, Carboplatin, Docetaxel and Everolimus. Treatment was applied for 3 weeks. Response to treatment was evaluated by comparing growth inhibition of treated tumors in relation to a control group. Patient tumors and xenografts were evaluated for HPV status by immunohistochemical staining of p16INK4A and detection of HPV-16 E6 and E7 viral DNA by PCR. Primary tumor and the derived xenografts are screened for common oncogenic mutations using the Illumina TruSeq Amplicon - Cancer Panel and for genetic expression profiles by Affymetrix analysis
Results: In total, 70 tumor samples were transplanted resulting in 26 stably growing patient derived xenografts and 21 remain presently ongoing. So far only 23 xenotransplanted tumors did not grow. This results in an engraftment rate of &gt;60%. Tumors remained histologically similar through several passages. Engraftment was not related to growth fraction of the primary tumor, ranging from 10 to 90% evaluated by Ki67 staining. In a few cases we were able to establish xenografts from primary tumors and synchronous metastases. These showed high similarity concerning growth rate and drug sensitivity. Response to treatment varied considerably. Significant growth inhibition in relation to the control group was observed in 8 of 11 (72%) treated tumors for Everolimus, in 4/11 (36%) for 5-FU, 3/11 (27%) for MTX, in 3/11 (27%) for Carboplatin, in 3/11 (27%) for Cetuximab and in 6/11 (54%) for Docetaxel. Out of the established xenografts four primary tumors were classified as HPV positive but only one of them remained positive after several passages in mice.
Conclusion: Our newly established head and neck cancer panel provides an excellent tool for preclinical drug and biomarker research. Together with the molecular genetic characterization, these patient derived xenografts can be used for modeling the systemic biology of the tumor and can help to develop new rational hypotheses for further clinical trials.
Citation Format: Konrad Klinghammer, Jan D Raguse, Moritz Siedmann, Michael Becker, Ulrich Keilholz, Jens Hoffmann, Iduna Fichtner. Establishment and characterization of patient-derived xenografts of head and neck tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2783. doi:10.1158/1538-7445.AM2013-2783