J. S. Taylor1, B. Yavuz3, J. Zeki1, K. Harrington3, J. M. Coburn3, N. Ikegaki5, D. L. Kaplan3, B. Chiu1,5 1Stanford University,Pediatric Surgery / Surgery / Stanford School Of Medicine,Stanford, CA, USA 3Tufts University,Biomedical Engineering,Medford, MA, USA 4University Of Illinois At Chicago,Surgery,Chicago, IL, USA 5University Of Illinois At Chicago,Anatomy And Cell Biology,Chicago, IL, USA
Introduction: Advanced stage neuroblastoma requires multi-agent chemotherapy but still portends a poor prognosis. Cisplatin is an effective systemic chemotherapy; however, treatment courses are often shortened because of side effects. We hypothesized that implanting a sustained release reservoir loaded with cisplatin can suppress tumor growth while limiting systemic toxicity.
Methods: Specially designed silk protein reservoirs were prepared using previously described techniques and loaded with 0.2 mg or 0.5 mg cisplatin. In vitro testing was performed to evaluate the cisplatin release profile from the reservoirs, and dose-dependent toxicity was determined using human neuroblastoma KELLY cells. Subsequently, KELLY cells were injected into mouse adrenal glands to create orthotopic tumors. After the tumors reached 100 mm3 by ultrasound, a sustained release reservoir was implanted into the tumors; reservoirs were either empty controls or loaded with 0.2 mg or 0.5 mg cisplatin. Tumor growth was followed with serial ultrasounds and animals were euthanized when tumor volume exceeded 1,000 mm3. Paraffin-embedded tumor sections were stained with hematoxylin/eosin.
Results: Cisplatin killed 50% of the KELLY cells in vitro at approximately one μg/mL. In vitro, Cisplatin 0.2 mg-loaded reservoirs released 53.28 μg of the loaded drug in 24 hours and 53.31 μg in four days. Cisplatin 0.5 mg-loaded reservoirs released 114.96 μg of the loaded drug in 24 hours and 313.84 μg in 13 days (Fig 1A). In vivo, cisplatin-loaded reservoirs suppressed tumor growth in a dose-dependent manner compared to control treated tumors (p < 0.05). Tumors treated with 0.5 mg cisplatin reached 500 mm3 after 17.6 ±3 6.4 days; tumors treated with 0.2 mg cisplatin took 4.2 ± 1.8 days; tumors treated with control reservoirs took 1.2 ± 0.3 days (Fig 1B). Similar growth suppression was observed at 600, 700, and 800 mm3. No significant toxicity was observed in the cisplatin-treated animals. Hematoxylin/eosin staining demonstrated tumor necrosis adjacent to the cisplatin-loaded reservoir.
Figure 1: A) In vitro cisplatin release profile from silk protein reservoir. Error bars represent standard deviations. B)Tumor growth kinetics when treated with control, 0.2 mg, or 0.5 mg cisplatin-loaded reservoirs. Asterisk (*) indicated p-value < 0.05.
Conclusion: Sustained release cisplatin reservoirs implanted into orthotopic neuroblastoma xenografts were able to significantly suppress tumor growth. Silk reservoirs can be utilized to load a larger amount of cisplatin for tumor implantation.
