Polo-like kinase 2 promotes chemoresistance and predicts limited survival benefit from adjuvant chemotherapy in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignances worldwide. Chemoresistance remains a major issue in the field of CRC treatment. The present study aimed to investigate the potential role of polo-like kinase 2 (Plk2) in chemoresistance in CRC. The associations between Plk2 and clinicopathological factors, as well as chemotherapeutic benefit were analyzed with a publicly available CRC dataset. The correlation between Plk2 expression and chemosensitivity was further confirmed in CRC cells. Moreover, knockdown and exogenous overexpression experiments of Plk2 were carried out to uncover the potential role of Plk2 in regulating the chemoresistance of CRC cells. We found that the expression of Plk2 was significantly associated with proximally located tumors. In addition, it was found that high expression ofPlk2 was associated with deficient mismatch repair status, B-raf serine/threonine kinase proto-oncogeneand Kirsten rat sarcoma viral oncogene homolog mutations. By contrast, tumor protein 53 mutation was correlated with a low expression level of Plk2. A higher expression level of Plk2 significantly predicted a poorer outcome in patients with CRC. However, the prognostic significance was only observed in patients who received adjuvant chemotherapy. In CRC cells, higher levels of Plk2 were associated with increased resistance to chemotherapeutic agents. Knocking down the expression of Plk2 resulted in elevated cellular apoptosis induced by oxaliplatin. By contrast, exogenous overexpression of Plk2 exerted an anti-apoptotic effect and enhanced the resistance of CRC cells to chemotherapeutic agents. In conclusion, a high expression of Plk2 was associated with chemoresistant traits of CRC through inhibiting apoptosis. These results suggested that Plk2 may serve as a predictive marker for chemoresistance and a novel target in CRC treatment.