Introduction:: Despite advances in chemotherapy over the past century, there is still a high rate of morbidity and mortality associated with pediatric cancers. According to a report from the St. Jude Lifetime Cohort Study, 99.9% of patients treated for childhood cancer develop chronic health conditions from the chemotherapy used to treat their initial malignancy. Major factors limiting treatment success include appropriate dosages of conventional chemotherapies for treatment in pediatric neuro-oncology, risk of future malignancies from drug toxicity, and systemic and local drug barriers preventing complete drug penetration of traditional drug delivery routes of administration1. To address this need, our group synthesized a novel hydrogel drug delivery system and performed a dose escalation study to determine the response of drug to the tumor site. Our strategy is to develop a novel, biodegradable starch hydrogel, Amygel, as a vehicle for sustained drug release. Specifically, in mouse xenograft models bearing pediatric brain tumors, we will test the use of Amygel to locally deliver chemotherapy directly to the tumor microenvironment.
Materials and Methods:: Hydrogels were synthesized utilizing a microwave-assisted synthesis (MAOS) method with the Anton Paar Microwave Monowave. The materials to formulate the hydrogels include dimethyl sulfoxide (DMSO, Sigma Aldrich), amylopectin (Sigma Aldrich), and free based doxorubicin (MedKoo). DAOY medulloblastoma cells (American Type Culture Collection, Rockewell, MD) were used to performed the tumor inoculation for in vivo dose escalation analysis. The cells were cultured in EMEM (Eagle’s Minimum Essential Medium; Sigma Aldrish, St. Louis, MO) supplemented with 10% FBS (Fetal Bovine Serum; Sigma Aldrich, St. Louis, MO) and 1% penicillin/streptomycin (Sigma Aldrish, St. Louis, MO) in T-75 culture flasks (Corning Inc., Corning, NY). The cells were cultured at 37ºC in a 5% CO2 humified atmosphere. 6.0 x 106 cells per site were injection subcutaneously into the nude mouse model. DAOY Cells were suspended into PBS mixed with Matrigel Matrix (Corning, Corning, NY). Each mouse then received one tumor in each thigh that will be treated with the doxorubicin-loaded hydrogel. Seven tumors will be in each dose group consisting of 50, 100, 200, 300, 400, 500, or 750 mg of doxorubicin in a single injection. Ultrasound was used for image guided treatment injections and tumor assessment. IVIS imaging is used to determine the diffusion of doxorubicin intratumorally.
Results, Conclusions, and Discussions:: Our Amygel/Doxorubicin strategy is designed to achieve improved tissue penetration of the chemotherapy agent by utilizing dimethyl sulfoxide in the formulation. Our data shows that utilizing the free base structure of doxorubicin, not the salt form, and formulating it in the Amygel system using dimethyl sulfoxide achieved complete elimination of the tumor without any histologic evidence of drug distribution beyond the tumor site. In the dose escalation study, our data shows that doxorubicin dose escalation controls the dosage diffusion over time in the tumor site.
Amygel delivery of chemotherapeutic agents directly to tumor sites has great advantages over traditional and emerging drug delivery technologies. Local delivery of compounds using Amygel increases drug concentration at the target site, decreases drug effects on non-target tissues, and improves drug penetration in the tumor tissue. Our data shows that based upon the tumor size, the doxorubicin concentration in the Amygel can control the diffusion of the drug to the tumor site. For these reasons, local chemotherapy delivery using Amygel may prove to be a more effective way to treat pediatric solid tumor malignancies and improve long-term patient outcomes.
Acknowledgements (Optional): : I would like to recognize and thank Dr. Elizabeth D. Barker and Dr. Jenny Patel for their mentorship throughout the experiments and beyond.
References (Optional): : Patel, J., A Local Drug Delivery Approach for Enhancing Tissue Penetration of Chemotherapy to Improve Treatment Outcomes of Pediatric Brain Tumors. 2022: The University of Tennessee, Knoxville
