Even though the isozymes LOXL1 and LOXL4 have not been in the focus in connection with cancer for a long time, recent results also suggest an involvement of these lysyl oxidases in tumour progression, which was summarised in a recent review.[52k] Interestingly, a strong overexpression of LOXL4 at the mRNA level has been observed in triple-negative breast cancer.[116] Recently, it was shown that both mutation of LOXL4 to the catalytically inactive protein and genetic ablation of the entire protein in MDA-MB-231 breast cancer cells lead to significantly reduced tumour growth. Here, LOXL4 is linked to breast cancer.