More than a physical structure providing support to tissues, the extracellular matrix (ECM) is a complex and dynamic network of macromolecules that modulates the behavior of both cancer cells and associated stromal cells of the tumor microenvironment (TME). Over the last few years, several efforts have been made to develop new models that accurately mimic the interconnections within the TME and specifically the biomechanical and biomolecular complexity of the tumor ECM. Particularly in colorectal cancer, the ECM is highly remodeled and disorganized and constitutes a key component that affects cancer hallmarks, such as cell differentiation, proliferation, angiogenesis, invasion and metastasis. Therefore, several scaffolds produced from natural and/or synthetic polymers and ceramics have been used in 3D biomimetic strategies for colorectal cancer research. Nevertheless, decellularized ECM from colorectal tumors is a unique model that offers the maintenance of native ECM architecture and molecular composition.
1. Introduction
Colorectal cancer (CRC) is an increasingly prevalent disease that accounts for substantial mortality and morbidity and is responsible for an impaired quality of life and high financial resource consumption
[1]. Despite advances in the development of less invasive screening and diagnostic approaches, approximately 25% of CRC patients are still diagnosed with a distant metastatic disease
[2]. Currently, available therapies have not only limited the curative impact but also developed resistance, leading to poor prognosis and increased mortality rates
[3]. In particular, immunotherapy has a limited application in CRC, being only recommended to patients with high microsatellite instable (MSI) tumors, which correspond to less than 15% of all CRC cases
[4]. This scenario highlights the urgent need to better understand the biological mechanisms underlying CRC onset, progression and spread to improve CRC diagnosis and establish tailored therapeutic strategies. For that, a detailed understanding of the tumor microenvironment is fundamental, since it is where the tumorigenic process begins and evolves under the heavy influence of the complex crosstalk between the cellular component (cancer cells and the non-malignant stromal cells), the non-cellular component (extracellular matrix—ECM) and the interstitial fluids
[5].
Over the last few years, the ECM has become a hot topic of research since this complex network of macromolecules is much more than a physical and stable structure providing support to tissues. The ECM is an extremely dynamic component of the TME
[6] that modulates the behavior of both tumor and cancer-associated stromal cells through its particular biochemical and biomechanical properties
[7]. During tumor development, the ECM is significantly altered, both structurally and in terms of composition, usually enabling cellular transformation, angiogenesis, inflammation, invasion and metastasis
[8,9][8][9]. These tumor ECM alterations translate into dysfunctional biomechanical tissue properties with increased stiffness activating several cellular pathways, such as YAP/TAZ
[10], TXNIP
[11], Rho/Rock-PTEN
[12], PI3K-AKT
[13], GSK3β
[14] and AMPK
[15,16][15][16].
Considering the relevant role of this cellular–acellular communication, several efforts have been made to develop new CRC models that accurately mimic the interconnections within the TME to understand the disease
[17,18,19,20,21,22,23][17][18][19][20][21][22][23]. Until now, most cancer research has been performed with in vitro two-dimensional (2D) cell culture. However, it is known that cells behave differently in 2D and three-dimensional (3D) cultures, and that animal models do not truly represent the human tumor architecture
[17]. Current 3D cancer models are now managing to bridge the gap between 2D monolayer cell lines, animal models and clinical research. There is an increasingly growing field for the development of 3D cell culture models that are able to closely recapitulate the TME landscape and screen anti-cancer drugs in CRC, such as bio-fabricated tissues
[18], organotypic 3D-bioactive models
[19] and cancer tissue-originated spheroids
[20]. Among these, several reports have described interesting strategies using decellularized ECM from native tissues where the cellular component is removed and the tissue physiology is maintained
[24,25,26][24][25][26].
2. Decellularized Colorectal Cancer Matrices as Bioactive Scaffolds for Modeling the Tumor Microenvironment
Decellularized ECM from malignant tissues is gaining attention in the field of organotypic modeling of tumor-stroma interactions by successfully incorporating key biochemical and biophysical characteristics of the native TME
[133,134,135][27][28][29]. Particularly, patient-derived scaffolds allow comparisons between the tumor and the normal adjacent tissues, as well as deliver the potential of a preclinical platform to test patient-specific responses to treatment therapies
[136,137][30][31]. However, decellularized ECM as a biomimetic model for CRC research is just beginning to be explored (
Table 1)
[24,25][24][25].
Table 1. Methods used for the decellularization and evaluation of biochemical/biomechanical properties of decellularized ECM from colorectal tissues.
ECM Sources |
Decellularization Method |
Biochemical Evaluation |
Biomechanical Evaluation |
REF |
Cell-derived matrix HT-29 SW480 CCD-841-Com |
-CHEMICAL 0.5% Triton X-100 20 mM NH4OH Ionic and nonionic surfactants |
n/a |
n/a |
[138,139,140][32][33][34] |
Human-derived tissue |
CHEMICAL 5 mM EDTA 10% DMSO 1% Triton X-100 10 mM sodium cholate hydrate 50 mM Tris-HCl Centrifugal rotation Ionic and nonionic surfactants Mechanical mixing |
-Cellular proteins (cytokeratin, vimentin) and stromal components (collagen IV, fibrinogen, hyaluronic acid): Immunohistochemistry -Actin: Western Blot -DNA content: SYBR agarose gel |
-Architecture: HE -3D structure: FITC staining of ECMs |
[50][35] |
CHEMICAL/ENZYMATIC 4% sodium deoxycholate 2000 kU DNase-I |
-DNA content: DNeasy Blood & Tissue kit -Stromal components (GAGs, Col IV): PAS and Immunohistochemistry -Cellular proteins (Ki67, vimentin, E-cadherin, DAPI): Immunofluorescence |
-Architecture: HE and Laminin -3D structure: SEM -Permeability: In-house developed permeability device |
[49][36] |
-DNA content: DNeasy Blood & Tissue kit and 1% SYBRsafe agarose gel -Stromal components (GAGs, Col IV): PAS, Masson’s Trichrome, Immunohistochemistry and Alcian blue |
-Architecture: HE, Gieson and Silver stains -3D structure: SEM |
[19] |
PHYSICAL/CHEMICAL Freezing 2% SDC 1% Triton X-100 Physical disruption Ionic and nonionic surfactants |
-Nucleic acids: HE -Collagens: SHG |
-Stiffness: AMR -Topography: SHG |
[52][37] |
CHEMICAL/ENZYMATIC 0.1% SDS 50 U/mL DNase-I Ionic surfactant |
-Nucleic acids: DAPI -DNA content: PureLink Genomic DNA Mini Kit -Histomorphological analysis: HE and Masson’s Trichrome -Major ECM proteins (Collagens I and IV, Laminin, Fibronectin and Hyaluronic acid): Immunofluorescence |
-Stiffness: Rheology -3D structure: SEM |
[26] |
CHEMICAL 1% SDS 1% Triton X-100 |
-DNA content: Nanodrop -Major ECM proteins (GAGs, Collagen I, Laminin and fibronectin): Immunostaining -Cellular proteins: F-actin (cytoskeleton), DAPI and HE (nuclei acid) |
-Structure and architecture: SEM and TEM |
[141][38] |
SISmuc (small intestine submucosa + mucosa from decellularized porcine jejunum) |
CHEMICAL 4% SDS 200 U/mL DNase I- |
n/e |
n/e |
[142][39] |
Mice-derived tissue |
CHEMICAL/ENZYMATIC 4% sodium deoxycholate 2000 kU DNase-I |
-DNA content: Roche’s DNA isolation Kit and Quant-It PicoGreen dsDNA Assay -Nucleic acids: DAPI and HE -Major ECM proteins (Collagens I and IV, Fibronectin and Laminin): Immunofluorescence and Masson’s Trichrome |
-Tensile testing: RSA-G2 solids analyzer |
[143][40] |