Serum carcinoembryonic antigen levels as a predictive biomarker for cytokine-induced killer cell immunotherapy in patients with colorectal cancer

Cytokine-induced killer (CIK) cells, as an adoptive immunotherapy, are effective at treating colorectal cancer (CRC). However, whether an individual can benefit from CIK cell therapy remains unclear. In this study, we analyzed the long-term effects of CIK cell therapy and specifically the relationship between tumor-associated antigen expression and the survival benefit of CIK cell therapy in patients with CRC. We conducted a retrospective clinical study of 98 patients with CRC who were pathologically diagnosed between 2010 and 2014. Of the patients in the study, 48 received surgery and/or chemotherapy (control group), and 50 received CIK cell infusion with chemotherapy or surgery (CIK group). CIK cells exhibited significant antitumor activity, expressing high levels of CD107 and increasing the apoptosis of CRC cells in vitro. Survival analysis showed that adjuvant CIK cell immunotherapy improved overall survival (OS) and progression-free survival (PFS) of patients with CRC. Moreover, OS and PFS improved significantly, irrespective of the stage of the disease. Furthermore, CIK cell adjuvant therapy significantly increased OS and PFS in patients with carcinoembryonic antigen (CEA) levels lower than 5 ng/ml before surgery, but not in patients with CEA levels above 5 ng/ml. Univariate and multivariate analyses showed that CEA expression is an independent prognostic factor for OS and PFS in the CIK cell treatment group. Adjuvant CIK cell therapy is an effective strategy for prolonging OS and PFS in patients with CRC, especially in those with serum CEA levels below 5 ng/ml.