Abstract C47: A platform of metastatic bioluminescent tumorgafts for preclinical studies.
Authors: Beurdeley Arnaud , Stephant Gael , Renauleaud Celine , Babin Anthony , Bourre Ludovic , Lassalle Myriam , Corcuff Erwan , Judde Jean-Gabriel 
Published: June 2012

Background: The ability of tumor cells to spread and form metastasis is one of the key parameters used to classify tumor aggressiveness. Metastasis detection at diagnosis or during follow-up post-surgery is associated with poor prognosis. The lack of pertinent models to investigate the biology of metastasis renders problematic the set-up of anti-metastasis therapies. We took advantage of our tumorgraft collection to develop models suitable to assess anti-metastatic therapy. Furthermore, to enable measurement of metastasis response to treatment, we labeled tumors with lentivirus-mediated luciferase insertion into tumor cells, allowing the follow up of metastasis formation by non invasive imaging.

Methods: In order to obtain a bioluminescent model, upon tumor resection, HBCx-12B tumor cells were dissociated and transduced with a defective lentivirus bearing the firefly luciferase gene. One million cells were injected subcutaneously in different strains of immunocompromised mice (RAG γC−/−; RAG γC−/− FLK; Nude; SCID; NOD SCID), tumor growth and metastasis formation were monitored throughout passages by whole body visualization using the Xenogen IVIS® Lumina. Mice were imaged over 10 to 24 weeks, and in order to prolong the follow-up window for metastasis detection, tumor resection was performed when primary tumor size reached 500 mm3. During this period, bioluminescence was measured every two weeks to assess metastasis appearance and progression. Bio-imaging allowed metastasis detection with a threshold of 100 to 400 cells per metastatic focus. The presence of metastases was confirmed by both histological analysis, and ex vivo organ fluorescence imaging. The pro-drug 5-aminolevulinic acid was injected intravenously, transformed into protoporphyrin IX, a fluorescent compound accumulated into tumor cells.

Results: Metastases developped in all tested strains with different efficiency. RAG γC −/− and SCID strains had the highest susceptibility, with fast and high metastasis incidence. RAG γC (9/9), RAG γC−/− FLK (2/2) and SCID (4/5) mice presented lung metastases after an average of 50-day independently of the passage, while metastases developed in 1/7 in nude mice after 90 days. Histological examination confirmed the adenocarcinomatous origin of metastases, extravading into the lung arteriolar vessels.

Conclusions and perspectives: Bioluminescent metastasis models could be successfully established by growing luciferase-enginered tumorgrafts into appropriate strains of immunocompromised mice. At present, other bioluminescent models of melanoma, pancreatic, and breast cancer tumorgrafts are being validated as metastatic. The establishment of bioluminescent metastasis models of different types of cancer will provide an useful tool to explore the biology of metastasis development and anti-metastatic therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C47.