Novel 3D µtissues Mimicking the Fibrotic Stroma in Pancreatic Cancer to Study Cellular Interactions and Stroma-Modulating Therapeutics

Architectural organization and molecular profiling of 3D cancer heterospheroids and their application in drug testing

3D cancer cell cultures have enabled new opportunities for replacing compound testing in experimental animals. However, most solid tumors are composed of multiple cell types, including fibroblasts. In this study we developed multicellular tumor heterospheroids composed of cancer and fibroblasts cell lines. We developed heterospheroids by combining HT-29, MCF-7, PANC-1 or SW480 with 1BR.3.G fibroblasts, which we have previously reported support spheroid formation. We also tested fibroblast cell lines, MRC-5, GM00498 and HIF, but 1BR.3.G was found to best form heterospheroids with morphological similarity to in vivo tumor tissue. The architectural organization of heterospheroids was based on histological examination using immunohistochemistry. We found that HT-29 and MCF-7 cells developed spheroids with the cancer cells surrounding the fibroblasts, whereas PANC-1 cells interspersed with the fibroblasts and SW480 cells were surrounded by fibroblasts. The fibroblasts also expressed collagen-1 and FAP-α, and whole transcriptomic analysis (WTA) showed abundant ECM- and EMT-related expression in heterospheroids, thus reflecting a representative tumor-like microenvironment. The WTA showed that PANC-1 heterospheroids possess a strong EMT profile with abundant Vimentin and CDH2 expression. Drug testing was evaluated by measuring cytotoxicity of 5FU and cisplatin using cell viability and apoptosis assays. We found no major impact on the cytotoxicity when fibroblasts were added to the spheroids. We conclude that the cancer cell lines together with fibroblasts shape the architectural organization of heterospheroids to form tumor-like morphology, and we propose that the various 3D tumor structures can be used for drug testing directed against the cancer cells as well as the fibroblasts.

Modeling Physical Forces Experienced by Cancer and Stromal Cells Within Different Organ-Specific Tumor Tissue

Mechanical force exerted on cancer cells by their microenvironment have been reported to drive cells toward invasive phenotypes by altering cells' motility, proliferation, and apoptosis. These mechanical forces include compressive, tensile, hydrostatic, and shear forces. The importance of forces is then hypothesized to be an alteration of cancer cells' and their microenvironment's biophysical properties as the indicator of a tumor's malignancy state. Our objective is to investigate and quantify the correlation between a tumor's malignancy state and forces experienced by the cancer cells and components of the microenvironment. In this study, we have developed a multicomponent, three-dimensional model of tumor tissue consisting of a cancer cell surrounded by fibroblasts and extracellular matrix (ECM). Our results on three different organs including breast, kidney, and pancreas show that: A) the stresses within tumor tissue are impacted by the organ specific ECM's biophysical properties, B) more invasive cancer cells experience higher stresses, C) in pancreas which has a softer ECM (Young modulus of 1.0 kPa) and stiffer cancer cells (Young modulus of 2.4 kPa and 1.7 kPa) than breast and kidney, cancer cells experienced significantly higher stresses, D) cancer cells in contact with ECM experienced higher stresses compared to cells surrounded by fibroblasts but the area of tumor stroma experiencing high stresses has a maximum length of 40 μm when the cancer cell is surrounded by fibroblasts and 12 μm for when the cancer cell is in vicinity of ECM. This study serves as an important first step in understanding of how the stresses experienced by cancer cells, fibroblasts, and ECM are associated with malignancy states of cancer cells in different organs. The quantification of forces exerted on cancer cells by different organ-specific ECM and at different stages of malignancy will help, first to develop theranostic strategies, second to predict accurately which tumors will become highly malignant, and third to establish accurate criteria controlling the progression of cancer cells malignancy. Furthermore, our in silico model of tumor tissue can yield critical, useful information for guiding ex vivo or in vitro experiments, narrowing down variables to be investigated, understanding what factors could be impacting cancer treatments or even biomarkers to be looking for.

Embedded bioprinted multicellular spheroids modeling pancreatic cancer bioarchitecture towards advanced drug therapy

The desmoplastic bioarchitecture and microenvironment caused by fibroblasts have been confirmed to be closely related to the drug response behavior of pancreatic ductal adenocarcinoma (PDAC). Despite the extensive progress in developing PDAC models as in vitro drug screening platforms, developing efficient and controllable approaches for the construction of physiologically relevant models remains challenging. In the current study, multicellular spheroid models that emulate pancreatic cancer bioarchitecture and the desmoplastic microenvironment are bioengineered. An extrusion-based embedded dot bioprinting strategy was established to fabricate PDAC spheroids in a one-step process. Cell-laden hydrogel beads were directly deposited into a methacrylated gelatin (GelMA) suspension bath to generate spherical multicellular aggregates (SMAs), which further progressed into dense spheroids through in situ self assembly. By modulating the printing parameters, SMAs, even from multiple cell components, could be manipulated with tunable size and flexible location, achieving tunable spheroid patterns within the hydrogel bath with reproducible morphological features. To demonstrate the feasibility of this printing strategy, we fabricated desmoplastic PDAC spheroids by printing SMAs consisting of tumor cells and fibroblasts within the GelMA matrix bath. The produced hybrid spheroids were further exposed to different concentrations of the drug gemcitabine to verify their potential for use in cell therapy. Beyond providing a robust and facile bioprinting system that enables desmoplastic PDAC bioarchitecture bioengineering, this work introduces an approach for the scalable, flexible and rapid fabrication of cell spheroids or multi-cell-type spheroid patterns as platforms for advanced drug therapy or disease mechanism exploration.

Decellularization of xenografted tumors provides cell-specific in vitro 3D environment

In vitro cell culture studies are common in the cancer research field, and reliable biomimetic 3D models are needed to ensure physiological relevance. In this manuscript, we hypothesized that decellularized xenograft tumors can serve as an optimal 3D substrate to generate a top-down approach for in vitro tumor modeling. Multiple tumor cell lines were xenografted and the formed solid tumors were recovered for their decellularization by several techniques and further characterization by histology and proteomics techniques. Selected decellularized tumor xenograft samples were seeded with the HCC1806 human triple-negative breast cancer (TNBC) basal-like subtype cell line, and cell behavior was compared among them and with other control 2D and 3D cell culture methods. A soft treatment using Freeze-EDTA-DNAse allows proper decellularization of xenografted tumor samples. Interestingly, proteomic data show that samples decellularized from TNBC basal-like subtype xenograft models had different extracellular matrix (ECM) compositions compared to the rest of the xenograft tumors tested. The in vitro recellularization of decellularized ECM (dECM) yields tumor-type–specific cell behavior in the TNBC context. Data show that dECM derived from xenograft tumors is a feasible substrate for reseeding purposes, thereby promoting tumor-type–specific cell behavior. These data serve as a proof-of-concept for further potential generation of patient-specific in vitro research models.