J. C. Harris3, B. Yavuz1, J. Zeki2, J. Coburn4, N. Ikegaki2, D. Levitin1, D. Kaplan1, B. Chiu2,3 1Tufts University,Biomedical Engineering,Boston, MA, USA 2University Of Illinois Chicago,Pediatric Surgery,Chicago, IL, USA 3Rush University Medical Center,Surgery,Chicago, IL, USA 4Worcester Polytechnic Institute,Biomedical Engineering,Worcester, MA, USA
Introduction: Etoposide is used to treat high-risk neuroblastoma patients. In this study we created sustained release, etoposide-loaded silk wafers to treat murine orthotopic neuroblastoma tumors. We hypothesized that intra-tumoral implantation of etoposide wafers could decrease tumor growth.
Methods: Silk wafers were made using previously described techniques and loaded with 100 μg etoposide. In vitro testing was performed to evaluate the etoposide release profile from the wafer, and the dose-dependent toxicity was determined using human neuroblastoma KELLY cells. KELLY cells were used to create orthotopic tumor in mice. When tumor volume reached >100mm3 on ultrasound (1) Etoposide 3% uncoated (EtoU-3%), (2) Etoposide 6% uncoated (EtoU-6%), (3) Etoposide 6% glycerin coated (Eto20x-6%) or (4) control wafer was implanted into the tumor. Tumor size was longitudinally measured using ultrasound following implantation. Paraffin-embedded tumor sections were stained with H&E.
Results: Etoposide killed 50% of the KELLY cells in vitro at 1 μg/mL. EtoU-3% released 72% of the loaded drug in 24 hours and 92.6% in 2 days. Drug release from EtoU-6% and Eto20x-6% continued for 30 days and 45 days, respectively. Tumors treated with EtoU-6% took 8.6 ± 1.7 days to reach 500mm3, EtoU-3% took 8.1 ± 1.7 days, 6% control wafers took 5.7 ± 1.0 days, and 3% control wafers 4.4 ± 1.0 days. Significantly slower tumor growth was seen with EtoU-6% and EtoU-3% compared to their respective controls (p=0.01, p=0.02), but no difference between EtoU-6% and EtoU-3% (p=0.63). Tumors treated with EtoU-6% took 8.2 ± 3.0 days to reach 500mm3, Eto20x-6% took 5.9 ± 1.9 days, and control wafers 1.6 ± 0.6 days. EtoU-6% and Eto20x-6% significantly slowed tumor growth compared to control wafer (p=0.01, p=0.02) but no difference in tumor growth between EtoU-6% and Eto20x-6% (p=0.23). H&E staining demonstrated tumor necrosis adjacent to the wafer in tumors implanted with EtoU-3%.
Conclusions: Silk wafers can be loaded with etoposide and used for intra-tumoral treatment of neuroblastoma. All formulations of etoposide-loaded silk wafer slowed tumor growth compared to controls, and the additional silk coating provided extended release. Silk wafer is a versatile implantable drug delivery system for neuroblastoma treatment.