COPS6 and cancer: COP9 signalosome subunit 6 (CSN6) is one of the eight subunits of the COP9 signalosome that is involved in proteasome-mediated ubiquitination,16,17 cell cycle,18,19 transcriptional activation,20 signal transduction17,19 and tumorigenesis.17,21 Previous studies have shown that CSN6 is highly expressed in many tumours, including cervical cancer,22 CRC,23 breast cancer24 and T cell leukaemia.25 In addition, CSN6 regulates tumour growth19,22 and tumour metastasis22,23 in cancer.