Abstract A5: Establishment of a novel spontaneous prostate cancer liver metastasis model
Authors: Roobol Stefan J. , van Zoggel Johanneke A.A. , de Ridder Corrina M.A. , Hoeben Sander A.H. , Versluis Yin C.I.L. , Ridwan Yanto R. , Haeck Joost C. , van Weerden Wytske M. 
Published: May 2016

Introduction: It is well-documented that prostate cancer (PCa) preferentially spreads to bone, but the patterns of non-osseous metastases are less well-defined. With the increased options for treatment of late stage patients, metastatic spread to lung, lymph nodes and liver has become more prominent. Especially, men with visceral (especially hepatic) metastases have a particularly poor prognosis. To understand the determining factors of this metastatic pattern in PCa and to elucidate the mechanisms underlying metastatic outgrowth in the liver and other relevant organs, we set out to develop a patient-derived xenograft (PDX) model of metastasis. We used a multimodality imaging approach to identify and monitor metastatic outgrowth.

Material & Methods: We established 3D cultures of the PC339 PDX model, originating from a TURP of a late stage patient. PCL339 3D cultures were transfected with M21 (firefly luciferase - GFP fused protein) and inoculated subcutaneously in NOD-SCID-gamma (NSG) mice. Mice with established PCL339-M21 tumors underwent tumorectomy (700-1000 mm3) to extent their life span and allow metastatic outgrowth. After tumorectomy, animals were imaged weekly using MRI, microCT and In Vivo Imaging System (IVIS) to monitor metastatic development. At sacrifice, liver and other luciferase-positive organs were stored for RNA isolation and qPCR and for immunohistochemistry. Additionally, the positive liver was cultured to retrieve the PCL339-M21-L subline. To investigate whether metastatic potential was improved, this subline was re-injected subcutaneously and the above described procedure was repeated. Positive organs, including lung, lymph node and bone, were cultured to retrieve the PCL339-M21-L-LN and PCL339-M21-ZL-LU sublines.

Results: Subcutaneous PCL339-M21-L tumors spread more consistent (almost 100%) and faster to liver compared to PCL339-M21 tumors (30 days after tumorectomy). Luciferase-positive signals in liver were detected by

IVIS as early as 7 days after tumorectomy. MRI showed the first visible lesions at 21 days while microCT imaging detected positive lesions only after 28 days. 3D reconstructed microCT images and MRI-detected lesions confirmed location of the signals as seen by IVIS. Similar to MRI images, macroscopic liver lesions could be clearly observed at 21 days. In all cases, additional (micro)metastatic spread to lymph nodes, lung and bone was seen by IVIS imaging. Positive signals from these micrometastases could be confirmed by qPCR and immunohistochemistry for androgen receptor, prostate specific antigen and luciferase or GFP.

Conclusion: We have established a new reproducible and transplantable PCa liver metastasis model PCL339-M21-L that shows spontaneous spread to liver and other organs like lung and lymph nodes. We demonstrated the value of non-invasive multimodality imaging to localize and follow metastatic spread and outgrowth over time. This unique PCL339-M21-L model is a valuable asset to study the biological aspects of PCa liver metastasis and provide a new PDX model to test potential therapies aiming to block metastatic spread of PCa.

Citation Format: Stefan J. Roobol, Johanneke A.A. van Zoggel, Corrina M.A. de Ridder, Sander A.H. Hoeben, Yin C.I.L. Versluis, Yanto R. Ridwan, Joost C. Haeck, Wytske M. van Weerden. Establishment of a novel spontaneous prostate cancer liver metastasis model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A5.