Engineering cancer microenvironments for in vitro 3-D tumor models

Abstract

The natural microenvironment of tumors is composed of extracellular matrix (ECM), blood vasculature, and supporting stromal cells. The physical characteristics of ECM as well as the cellular components play a vital role in controlling cancer cell proliferation, apoptosis, metabolism, and differentiation. To mimic the tumor microenvironment outside the human body for drug testing, two-dimensional (2-D) and murine tumor models are routinely used. Although these conventional approaches are employed in preclinical studies, they still present challenges. For example, murine tumor models are expensive and difficult to adopt for routine drug screening. On the other hand, 2-D in vitro models are simple to perform, but they do not recapitulate natural tumor microenvironment, because they do not capture important three-dimensional (3-D) cell–cell, cell–matrix signaling pathways, and multi-cellular heterogeneous components of the tumor microenvironment such as stromal and immune cells. The three-dimensional (3-D) in vitro tumor models aim to closely mimic cancer microenvironments and have emerged as an alternative to routinely used methods for drug screening. Herein, we review recent advances in 3-D tumor model generation and highlight directions for future applications in drug testing.

Advances in multicellular spheroids formation

“…Moreover, a Matrigel with lung cancer cell mixture injected into an animal model resulted in rapid formation of tumour MCSs in animals compared with cell injections without Matrigel. The similar results were also obtained from cancer cells of A253 and B16F10 [76]. However, three-dimensional tumour models grown on the Matrigel exhibited less similarity to the in vivo tumours compared with three-dimensional poly (lactide-co-glycolide) (PLG) engineered tumours because of a decreased level of IL-8 expression in the Matrigel [49].…”

“…Human colon Matrigel -rich in growth factors, signal factors for cell proliferation -expensive and animal derived PC-3M, PrCa, NCI-H600 [74], HepG2 [75], A235, B16F10 [76] agar -damage on cells by forces from gel formation inside the agar -excellent mechanical properties human foreskin dermal fibroblasts [77], cortical cell [78] alginate -rapid formation of hydrogel scaffolds -strong chemicals required to break hydrogel networks to harvest MCSs human fat-derived stromal vascular fraction cells [79], human colon cancer cells (HCT116) [80] fibrin -promoting cell attachment -high cell viability human mesenchymal stem cell [81], B16-F1…”

Microfluidic models for adoptive cell-mediated cancer immunotherapies

“…For example, murine models are complex, expensive and time-consuming and 2D in vitro tumour models, although simpler and faster, fail to mimic the native 3D tissue structure or the surrounding tumour microenvironment. To overcome some of these limitations, 3D in vitro models are being developed that offer the capability to investigate the role of the TME in a more physiologically realistic 3D condition compared with standard 2D in vitro assays [30]. TME architecture presents structural, mechanical and chemical cues that affect the expression of essential molecules such as integrins and matrix metalloproteinases that activate signalling pathways to regulate cell adhesion, EMT, migration and differentiation; and, although a degree of simplification is probably needed, it can be argued that standard 2D systems missing the features of 3D tissue organisation that play an essential part in cell growth, function, differentiation and interaction lack sufficient physiological relevance.…”

Responsive graphene oxide hydrogel microcarriers for controllable cell capture and release

“…Recently, strategies for the on-demand capture, proliferation, and release of cells in biomimetic three-dimensional (3D) environments have received increasing attention in fields such as cell biology, drug discovery and tissue engineering [1][2][3][4][5][6][7][8]. In particular, microcarriers have emerged as an optimized strategy based on novel 3D biomaterial scaffold platforms, which have advantages in terms of space saving, cost effectiveness, and lower time and labor requirements for cell culture [8][9][10].…”

“…In particular, microcarriers have emerged as an optimized strategy based on novel 3D biomaterial scaffold platforms, which have advantages in terms of space saving, cost effectiveness, and lower time and labor requirements for cell culture [8][9][10]. Several approaches have been employed for engineering cell microcarriers, including micromolding, electrojetting, photolithography and microfluidics [10][11][12][13][14].…”