Impact of Tumor Microenvironment on Intratumor Distribution of Liposomes in Prostate Cancer
Type of DegreePhD Dissertation
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Extensive developments in nanocarrier formulations and their applications in cancer therapy have occurred in the last few decades. This improvement brought many FDA-approved liposome nanoparticles (LNPs) and other nanoparticle formulations. However, it has been established in many clinical studies that the efficacy of these LNPs has not met the expectations. This unsatisfactory outcome results from the poor correlation between existing in vitro 2D monolayer culture and that of preclinical and clinical “human” in vivo models. Solid tumors are made up of cancer cells with various stromal cells and factors that represent the tumor microenvironment (TME). The presence of fibroblasts, macrophages, and other stromal cells contributes to the poor distribution and efficacy of LNPs. Therefore, existing 2D models fail to recapitulate the architecture and complexity of tumor pathology and do not capture the challenges associated with the distribution and deposition of nanoparticles and their payloads. Our study uses metastatic castration-resistant prostate cancer (mCRPC) cells (PC3) that show neuroendocrine differentiation, which is associated with poor prognosis and survival. Accordingly, our goal was to develop a 3D multicellular platform that permits the examination of the impact of the TME on the performance of nanomedicines. Furthermore, we hypothesize that stromal cells can alter the barrier properties within the TME and the distribution or uptake of LNPs, specifically cancer-associated fibroblasts (CAFs). To achieve that, we established a 3D model of prostate cancer with CAFs that allows visualization of drug distribution and uses flow cytometry to measure drug uptake. To examine the impact of TME, we developed model conventional and stealth liposomes similar to clinically approved formulations and stably entrap propidium iodide over 72 hours under physiological conditions (37 oC with serum). Moreover, we have demonstrated that free propidium iodide can be taken up by live cells with prolonged exposure (>6 hours). In addition, we have determined the effect of CAFs on distribution and uptake between conventional and PEGylated liposomes in our 3D co- culture model using flow cytometry. We also acquired scanning fluorescence confocal microscopy images to confirm our findings in flow results and gain insights into the spatial distribution throughout different 3D co-cultures. We are using RNA-seq and immunoblotting to determine the effect of stromal cells, such as fibroblasts, on gene expression and protein changes in 3D spheroids. Preliminary data suggest that the inclusion of CAF results in genes associated with the malignant phenotype. In conclusion, insights into the interplay between LNPs and solid tumors and their microenvironment can be exploited to optimize and individualize the treatment of aggressive primary cancers and metastatic disease.