ERBB2 and monocytic leukemia: The human monocytic leukaemia cell line THP-1 shares many properties with human monocyte-derived macrophages after stimulation with phorbol-12-myristate 13-acetate (PMA) for 24 h.28 Here, we examined the expression of MMPs in PMA-treated THP-1 macrophages expressing CAR-h147 (Fig. 5a) after coculture with HER2+ human breast cancer MDA-MB-453 tumour cells (Fig. 5b).