In this study, we first detected PCSK9 protein expression in colon cancer tissues and found that PCSK9 protein was mainly expressed in the cytoplasm of tumor cells at a high level compared with that of the corresponding adjacent normal tissues and distal tissues, while the level of PCSK9 expression was similar between the adjacent and distal tissues (Fig. 1a and b and Table 1). Here, PCSK9 is linked to malignant colon neoplasm.