Colorectal cancer (CRC) is the third most frequently diagnosed type of cancer worldwide. Stage II CRC accounts for ~25% all CRC cases and their management after surgical resection remains a clinical dilemma due to the lack of reliable criteria for identifying patients who may benefit from adjuvant chemotherapy. Homeodomain‑interacting protein kinase 2 (HIPK2), a multifunctional kinase involved in numerous signaling pathways, serves several key roles in cell response to different types of stresses, including chemotherapy‑induced genotoxic damage. In the present study, immunohistochemistry was performed for HIPK2 on a tissue microarray of primary human tumor samples from 84 patients with stage II CRC, treated (30 patients) or not treated (54 patients) with adjuvant chemotherapy, and sequenced for the TP53 gene, a key HIPK2 target in genotoxic damage response. It was observed that, regardless of the TP53 gene status, a high percentage of HIPK2+ cells was associated with therapeutic vulnerability in stage II CRC, suggesting a contribution of HIPK2 to drug‑response in vivo. For the in vitro characterization, HIPK2 was depleted in human CRC cells by CRISPR/Cas9 or RNA interference. HIPK2‑proficient and HIPK2‑defective cells were evaluated for their response to 5‑fluorouracil (5‑FU) and oxaliplatin (OXA). The results revealed that HIPK2 depletion induced resistance to 5‑FU and OXA, and that this resistance was not overcome by brusatol, an inhibitor of the antioxidant response regulator nuclear factor erythroid 2‑related factor 2 (NRF2), which is frequently overexpressed in CRC. By contrast, cell sensitivity to 5‑FU and OXA was further induced by brusatol supplementation in HIPK2‑proficient cells, further supporting the contribution of HIPK2 in chemotherapy response. Overall, the present results suggested that HIPK2 may be a potential predictive marker for adjuvant‑treated stage II CRC and for prospective therapy with NRF2 modulators.
Keywords: HIPK2; NRF2; brusatol; CRC; adjuvant therapy.