Depletion of Lysyl Oxidase-Like 4 (LOXL4) Attenuates Colony Formation in vitro and Collagen Deposition in vivo Breast Cancer Model

Background: Lysyl oxidase (LOX) family proteins have recently become a topic in cancer progression. Our recent study found a high expression of LOX-like 4 (LOXL4) in MDA-MB-231 cells. Objective: To reveal the impact of depleted LOXL4 in both in vitro and in vivo breast cancer models from a histological perspective. Material and Method: Endogenous LOXL4 was depleted using the CRISPR/Cas9 on MDA-MB-231 parental cells. Based on the LOXL4 protein expression, the clone was determined for the next experiment, thus generating MDA-MB-231 LOXL4 KO. Cell assay was conducted using colony formation assay (n=3) followed by crystal violet staining. The indicated cells were inoculated orthotopically to female BALB/c nude mice (n=5). At the end of the experiment, tumors were isolated, fixed, and prepared for Masson Trichrome staining. Result: CRISPR/Cas9 completely depleted LOXL4 expression on clone number #2-22. Depletion of LOXL4 reduced the colony size formed by MDA-MB-231 cells. MDA-MB-231 LOXL4 KO #2-22 derived tumors showed depressed tumor volume compared to the parental group. Reduced collagen was also observed from the Masson Trichrome staining (p<0.001). Conclusion: Depletion of LOXL4 downregulates the growth of MDA-MB-231 cells in vitro and collagen deposition in vivo.