Developing the Three Dimensional Tumor Model for Melanoma Drug Screening
Two-dimensional (2D) Tissue Culture Treated Plastic (TCTP) is widely used for cancer drug screening and has dominated the field for a long time. Compared with traditional two dimensional cell culture, a three dimensional tumor model may able to provide more reliable experimental results related to drug screening and discovery. With the development of nanoparticle chemotherapies, there is a need for ways to better investigate and characterize the effect of the 3D tumor environment. Cerium oxide nanoparticles, Nanoceria, is one of the potential solutions being explored for treating melanoma in the future in combination with conventional chemotherapies. This is attributed to its special dual functions: accumulating the radical oxygen species to help kill the melanoma cells in the acidic tumor microenvironment and acting as anti-angiogenic factor by modifying the tumor stromal components, while also providing oxidative protection to the surrounding tissue in the physiologically neutral pH microenvironment of normal tissues. In this study, the effect of extracellular matrix (ECM) stiffness on melanoma cells is investigated using a new three dimensional collagen-based tumor model. Initially, cell morphology and proliferation are characterized with respect to the different matrices. Then, a proof-of-concept drug screening of nanoceria in combination with commonly used small molecule chemotherapy drugs are assessed in terms of cytotoxicity and cell death mechanism using the characterized substrates. Finally, the ability of nanoceria to induce differential expression of several key metastatic drivers in tumor cells is caused by pH driven redox surface chemistry known to cause mitochondrial stress. Lysyl oxidase, MMP9 and hypoxia induce factor 1 alpha (HIF1α) expression, which are related to redox stress pathways and ECM remodeling, are investigated under tumor hypoxia-like conditions to demonstrate the importance of 3D tumor ECM models for developing a new nanoceria treatment for melanoma. The results show the biocompatibility and biomimetic properties of crosslinked, plastically compressed collagen gels (XPC) as models for melanoma tumors for in-vitro studies. Furthermore, the potential of nanoceria as an adjuvant chemotherapy for melanoma is demonstrated to show different efficacy on the collagen models compared to typical 2D TCTP culture. Finally, the expression of HIF-1α, MMP9 and lysyl oxidase are shown to be increasing with the increasing of oxidative stress, and provides a motivation for further studies of nanoceria using 3D models to develop a new effective treatment for melanoma. This research will help lead to a more broadly attention of application of this novel tumor model for further melanoma research, and can provide many clues to explain the mechanism of nanoceria with respect to the complex interplay of tumor hypoxia and the tumor ECM.