The generation of MDA-MB-231 cells with different LOX expression levels and harvest of tumor tissue. (a) Morphology and GFP expression of MDA-MB-231 after lentiviral transfection. Left: cell morphology under phase contrast microscope; Right: GFP expression. Scale bar: 100 μm. (b) qPCR analysis of the mRNAs expression level of LOX which was normalized to GAPDH (n = 3, *P < 0.05, **P < 0.01, compared with the control group, ANOVA followed by Tukey's post hoc test). (c) Western blotting analysis of LOX protein expression of the cells. (d, e) Tumor tissue after subcutaneous injection into the armpit of male nude mice. (f) Diameter of tumor tissue sample. (g) Thickness of tumor tissue sample. (h) Decellularized tumor tissue sample. (i) Schematic illustration of the decellularization procedure. (j) Tumor volumes at different time postimplantation (n = 3). Low: low stiffness group; Medium: medium stiffness group; High: high stiffness group. (k) Elastic modulus of DECM scaffold (n = 3). *P < 0.05 represents statistically significant difference compared with the Medium group. **P < 0.01 represents extremely statistically significant difference compared with the he Medium group. Statistical significance was determined by ANOVA followed by Tukey's post hoc test. Low: low stiffness group; Medium: medium stiffness group; High: high stiffness group.