As a consequence, US9 may travel even in the absence of other viral functions that are required for virus transport. In this study, GFP was used as a tool to chase US9 localization. However, from a different standpoint, GFP may be also seen as a molecule targeted to specific destinations by the addition of the US9 sequence. Importantly, this US9 sequence is sufficient to confer the resulting GFP fusion protein the specific localization pattern described, even though GFP is about three times larger than full length US9. Thus US9 is not only a valid molecular tool for the study of axonal transport but may also be used to deliver large proteins or other targets to specific neuronal sites. To achieve this goal, a full understanding of how US9 transport vesicles are formed and loaded is necessary. Once revealed, these mechanisms may be exploited to accomplish transport delivery and design/test different loading strategies. Their composition and environment are governed by biochemical and molecular signals exchanged between cells and their extracellular matrix. Even though 2D tumor cell cultures have been used routinely for conducting biochemical and drug sensitivity tests in oncology, they seldom mimic the in vivo environment, and scarcely reflect integral biomimetic characteristics such as cell-cell and cell-matrix interactions and their corresponding spatiotemporal signaling, metabolic gradients, and mechanical restriction. Thus, bioengineering tumors by using biological relevant 3D tumor cell culture models can bridge between in vitro cell based assay and the native microenvironment of living organisms. In addition, 3D culture systems generated from human tissue could be a better tool for drug screening by implementing more accurate in vivo equivalent structures and organization and might produce more predictive response than non-human systems. Many 3D tumor cell culture models ranging from scaffolddependent to scaffold-free, and consisting of single or multiple cell types have been developed. These models provide the opportunity to simulate important aspects of tumor masses including cancer cell aggregation and clustering, cell migration and proliferation, angiogenic factors release and hypoxia. One of the most widely used models is the Multicellular Tumor Spheroids system, a scaffold-free tumor cell system that can facilitate cell-cell interactions through chemical linkers or gravitational enhancement. Many extracellular matrices such as Matrigel, type I collagen, fibrin, and hyaluronic acid have been used as tumor cell 3D scaffolds. These biologically derived matrices provide both chemical and mechanical cues essential for modulation in gene expression while allowing for cellular adhesion and integrin engagement. However, there are still some incomplete requirements for cancer research and drug development, such as unknown dose of growth factors and additives in the preparations, uncontrollable mechanical rigidity, batch to batch variations, low reproducibility, complex protocol setup, and physiological irrelevant matrices for cells. The ECM plays an important role in supporting or even inducing tumorigenesis. The most common extracellular matrix component R428 1037624-75-1 presenting in the tumor microenvironment is collagen.