01.06 Novel Fluorescent Dye VGT-309 Can Identify Early Malignant Mesothelial Cells

F. S. Azari1, G. T. Kennedy1, L. Frenzel Sulyok1, M. Bryski1, E. Bernstein1, S. Singhal1 1Hospital Of The University Of Pennsylvania,Thoracic Surgery,Philadelphia, PA, USA

Optimal chance for mesothelioma cure is predicated upon R0 resection and sound surgical principles, which often is not possible due to extensive nature of the disease and inability to discern malignant cells using visual and tactile feedback.  Fluorescence guided surgery can ameliorate these challenges and aid in detection of residual disease. The purpose of this study was to evaluate the in-vivo sensitivity of a novel fluorescent dye (VGT-309) in detection of malignant mesothelioma.

All experiments were approved by the IRB and were conducted in accordance to policies set forth by the office of University Laboratory Animal Resources.  Athymic 15-week old BALB/c female mice were injected with 1 million AB12 cells (mouse derived mesothelioma cells) which were grown in supplemented R10 media.  Subsequently, after tumor burden reached 250mm3, the mice were injected with 100 uL of vehicle solution of VGT-309 at differing doses. Animals were then imaged at 15-minutes, 1 hour, 3 hours, 24 hours, and 48 hours using near-infrared (NIR) imaging. The organs and tumor cells were retrieved after 48 hours for histopathological evaluation of dye accumulation. Signal to Background Ratios (SBR) were measured to quantify fluorescence using the ImageJ software (National Institutes of Health).

All the animal subjects tolerated the procedure well without adverse effects attributable to VGT-309 administration.  After 48 hours, tail vein injection at 2mg/kg and 4 mg/kg demonstrated consistent fluorescence in AB12 cells in all the mice under NIR imaging. Strongest fluorescence (15,000 A.U) was detected after 24 hours of drug delivery compared to earlier time points and 48 hours. Furthermore, malignant mesothelial cells showed strongest fluorescence (12,500 absorbance units (A.U)) versus various visceral organs including pancreas, liver, stomach, bowel, and lung with mean A.U of 5300 (Figure 1). Immunohistochemical and histopathological analysis confirmed the selective accumulation of the dye in the tumor compared to background healthy tissue. Mean SBRs for tumor tissues were noted to be 3.48 and 4.12 at 24 and 48 hours respectively.  

We have demonstrated that the novel VGT-309 dye can safely and reliably accumulate in malignant mesothelial cells as well as be detected using conventional fluorescence equipment. Implementation of this dye in surgical treatment of mesothelioma patients can aid in higher chance of R0 resection and subsequently increase the 5-year survival rates. Further studies in animals are needed to assess the efficacy of tumor dye accumulation.