Figure 6.

Tumor-on-chip (TOC) systems that consider spheroids embedded in non-cancerous cell-laden-hydrogels. (a) Chemotaxis-driven assembly of endothelial barrier in a TOC platform [50]. Brightfield images of MCF7 spheroids co-cultured with human umbilical vein endothelial cells (HUVECs) (i) immediately after encapsulation, (ii) after three, and (iii) five days of culture. Scale bars: 200 μm. (iv) Evolution of HUVEC densities within different GelMA hydrogel zones 1 through 5 (zones are indicated on the oval inset). Zones are indicated within the inset. (v) Spheroid size as a function of culture time. Size was quantified as the projected area of the spheroid and normalized to its size at day 0; (*) and (**) indicate statistically significant differences of p < 0.05 and 0.01, respectively in a pairwise t-test. (vi) HUVECs and MCF7 spheroids (as observed in bright field) five (D5) and eight days (D8) after doxorubicin (DOX) treatment. Red arrows indicate the presence (or absence) of endothelial barrier. Scale Bar: 200 μm. (vii) MCF7 spheroid size after treatment with increasing doses of DOX. The spheroid area was normalized with respect to that of untreated spheroids. Significant differences are indicated by (*, **): p < 0.05 and 0.01, respectively (pair wise t-test). Taken from reference [50]; (b) TOC developed by Jeong et al. [51] to study the crosstalk and mutual activation between fibroblasts and cancer cells: (i) schematic of the device, (ii) and (iii) successive close-ups on the channel section, (iv) detail of the cell culture channel, and (iv) comparison of migration distances of fibroblasts in the direction of the cancerous region (blue) and the non-cancerous region (gray). (vi) Micrographs of cancer spheroids treated with different doses of DOX in monoculture and co-culture conditions. Scale bars: 50 μm. (vii) Evaluation of DOX efficacy in co-culture and monoculture conditions in this TOC. Significant differences are indicated by (*): p < 0.05. Taken from reference [51]; (c) TOC developed by Aref et al. [48], to model immune checkpoint blockade. (i) A real tumor is subjected to dissociation (mechanical and enzymatic) to yield dissociated tumor tissue (spheroids, cell agglomerates and single cells); (ii) schematic of Aref’s TOC; (iii) spheroid stained to reveal the presence of calcein AM (green); CD8 T cells (red); tumor cells (EpCAM; purple); and all nucleated cells (Hoechst; blue). Scale bars: 20 μm. (iv) Cell viability, and (v) cytokine expression profile over time in spheroids derived from patients and treated with different immunotherapies: α-PD-1: pembrolizumab, 250 μg mL⁻¹); α -CTLA-4: (ipilimumab, 50 μg mL⁻¹); or a combination. Taken from reference [48]. (d) TOC proposed by Bruce et al. [49] to recreate a bone marrow microenvironment and study acute lymphoblastic leukemia (ALL): (i) schematic representation, (ii) actual image, (iii) and detail of the post array within the device. (iv–vii) Confocal images of co-cultures of SUP-B15 (yellow arrows) and BMSC cells (white arrows) in (iv) 2D static, (v) 3D static, and (scale bars: 500 μm and 100 μm) (vi) 3D dynamic models. Proliferating cell nuclei were stained with Ki67 (green). Actin filaments were stained with phalloidin (red). Cell nuclei were stained with DAPI (blue). Scale bars: 20 μm. (vii) Chemoresistance of tumor cells to Ara-C among tri-culture or monoculture systems, in 2D versus 3D culture, and exposed (or not) to interstitial flow. (+) and (*) indicate significant difference between groups of p < 0.1, and p < 0.05, respectively. Taken from reference [49].