Localized Treatment of Malignant Melanoma Using a Modified Cellulose-Based Hydrogel Loaded with Temozolomide with Increased Safety of Human Dermal Fibroblasts and the Mechanisms Behind the Effect

Abstract

Melanoma pathophysiology is highly varied, and the initial cause of tumorigenesis is still unknown, but it is likely a combination of both epigenetic and genetic means. Further, melanoma tumors have one of the highest mutational burdens of all cancers and are largely composed of varied subpopulations within the same tumor. These two factors provide insight into why melanoma is so difficult to treat medicinally. Dacarbazine is the gold-standard of metastatic melanoma treatment, yet only has an overall response rate of 22% and no impact on survival. Temozolomide (TMZ), an analog of dacarbazine, is often viewed as a more ideal choice because of its more favorable side effect profile and its ability to pass across the blood-brain barrier. While Dacarbazine is converted to its active form in the liver, TMZ is converted in the presence of physiological (neutral) pH levels. Local delivery using hydrogels loaded with a specific chemotherapy drug are viewed as a more efficient and safer method of chemotherapy administration. Hydrogels can allow for lower dosages, sustained release, and minimized side-effects to healthy tissue. The ultimate goal is first to improve the effectiveness of TMZ cytotoxicity in melanoma while being safer to normal skin cells by using a modified cellulose-based hydrogel as a vehicle for drug delivery and second, use the expression of proteins associated with chemoresistance to determine the mechanisms that are overcome by localized sustained delivery. This is to be accomplished with the use of a hydrogel made of cellulose nano-fibers (CNF) modified with polyacrylic acid (PAA) to retain an acidic environment to prolong TMZ stability and release. Protein analysis of biomolecules that promote chemoresistance will also be analyzed between melanoma and normal cells to better understand by what mechanism hydrogel loaded drug release is more efficient on melanoma cytotoxicity, while simultaneously being safer on normal cells. The strategy to reach the goal of an improved delivery of TMZ will be accomplished throughout the following aims: (1) Determine cell viability of highly resistant Duke melanoma 6 cells (DM6) and human dermal fibroblasts (HDF-α) after treatment with free TMZ and hydrogel delivered TMZ, as well as characterizing the release profile and stability of TMZ when loaded into modified CNF; (2) Bridge the gap between in vitro and in vivo using a 3D collagen matrix seeded with DM6 or HDF-α. TMZ delivered via CNF (CNF/TMZ) will be injected in an intratumoral fashion into the gel. (3) Protein levels associated with methylated DNA repair and glutathione synthesis, amino acid import, and endogenous cysteine production will be measured to further specify the means CNF/TMZ is able to bypass chemoresistance of DM6 without significant harm to HDF-α. Further analysis will include quantification of oxidative stress molecules and glutathione synthesis specific molecules.