Abstract B69: VAL401 decreases tumor volume in a xenograft model of pancreatic cancer utilizing a novel improved luciferase labelling technique

Bioluminescent-labelling allows sensitive non-invasive sequential imaging of tumor development and early metastasis. Current methods for the genetic modification of cells typically use integrating genotoxic viruses that can potentially disrupt the molecular behavior of cancer cell lines due to their random nature of integration. VAL401 is the reformulation of a clinical drug to enable use in the treatment of cancer. Preclinical data indicate potential use of the reformulated drug in lung cancer, where many subsets of patients have currently a high unmet medical need. We have utilized a non-viral DNA vector that comprises an S/MAR (Scaffold/Matrix Attachment Region) element to stably modify cells to be further used in xenograft studies to allow long term expression without affecting cell behavior or silencing over cell divisions. Human BxPC3 pancreatic cancer cells were stably transfected with a pSMARt-UBC-Luc and cultured for 4 weeks under selection. Colonies that formed after this period were isolated and expanded in normal medium and evaluated for luciferase expression and molecular integrity of the DNA vector. For in vivo studies, BxPC3 cells were inoculated orthotopically into the pancreas of athymic nude mice. Four experimental groups were included in the study: 1) Control group receiving vehicle; 2) Reference compound gemcitabine (60 mg/kg, q3dx4 i.p, one week pause, q3dx4 i.p.); 3) Test compound VAL401 (1 mg/kg, p.o. daily); 4) Test compound VAL401 (2 mg/kg, p.o. daily). The luciferase transfected cells maintained their original properties with stable expression. Luciferase-labelled BxPC3 cells inoculated orthotopically into the pancreas were successfully followed for 5 weeks with non-invasive bioluminescence imaging by IVIS, and the results demonstrated high-quality follow-up of tumor growth compared with tumor models using non-labelled cells. BxPC3-luc cells induced growth of pancreatic tumors with high take rate in all groups. Gemcitabine and both studied doses of VAL401 decreased tumor volume, and the same trend was seen in tumor weight and the BLI parameters (total flux, area and average radiance) during the study. In conclusion, both gemcitabine and VAL401 decreased tumor volume and same trend was seen in BLI. Our results demonstrated that S/MAR DNA vectors are able to produce genetically modified cells without the limitations of random genomic integration, whilst providing extra-chromosomal mitotic stability and sustained transgene expression at high level. When utilized in orthotopic xenograft studies, these luciferase expressing cells formed a reliable and essential non-invasive imaging platform that improves substantially efficacy testing of anticancer drug candidates. Citation Format: Mari I. Suominen, Jenni Bernoulli, Suzanne Dilly, Johanna Tuomela, Matthias Bozza, Katja M. Fagerlund, George Morris, Jussi M. Halleen, Richard Harbottle. VAL401 decreases tumor volume in a xenograft model of pancreatic cancer utilizing a novel improved luciferase labelling technique. [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 B69.