Resistance to conventional chemotherapeutic agents, including irinotecan (CPT‑11), 5-fluorouracil and capecitabine is a major cause for therapeutic failure in patients with colorectal cancer (CRC). Increasing evidence has demonstrated that cancer cells exhibiting stem cell-like characteristics are associated with the development of resistance to chemotherapeutic agents. As a plant polyphenol, curcumin has been demonstrated to have the ability to ameliorate resistance of CRC to chemotherapeutic agents, but the associations among curcumin, cancer stem cells (CSCs) and chemoresistance of CRC remain unclear. The present study established a CPT‑11-resistant colon cancer cell line, LoVo/CPT‑11 cells, and detected the expression levels of CSC identification markers [cluster of differentiation (CD)44, CD133, epithelial cell adhesion molecule (EpCAM) and CD24] in parental cells and CPT‑11-resistant cells. It was revealed that the expression levels of the colon CSC markers in LoVo/CPT‑11 cells were significantly higher compared those in parental cells at the mRNA and protein level. The effect of curcumin on the chemoresistance to CPT‑11 and the expression levels of CSC identification markers in LoVo/CPT‑11 cells separately treated with curcumin and CPT‑11 were further investigated. The results revealed that curcumin significantly attenuated chemoresistance to CPT‑11, and treatment with curcumin resulted in a significant reduction of the expression levels of CSC identification markers. Furthermore, a tumor sphere formation assay was used to enrich colon CSCs from LoVo/CPT‑11 cells, and demonstrated that curcumin efficiently diminished the traits of colon CSCs, as evidenced by the inability to form tumor spheres, the reduction in the expression of CSC identification markers, and apoptosis-induced effects on sphere-forming cells treated with curcumin alone or in combination with CPT‑11. Altogether, the present data demonstrated that curcumin attenuated resistance to chemotherapeutic drugs through induction of apoptosis of CSCs among colon cancer cells. These findings may provide novel evidence for the therapeutic application of curcumin in CRC intervention.
Copper is an essential trace element in an organism, and changes in copper levels in vivo often indicate a diseased state. Copper and immunity have been discussed since the last century, with copper deficiency significantly affecting the development and function of the immune system, such as increased host susceptibility to various pathogens, decreased number and impaired function of neutrophils, reduced antibacterial activity of macrophages, decreased proliferation of splenocytes, impaired B cell ability to produce antibodies and impaired function of cytotoxic T lymphocyte and helper T cells. In the past 20 years, some studies have shown that copper ions are related to the development of many tumors, including lung cancer, acute lymphoid leukaemia, multiple myeloma and other tumors, wherein copper ion levels were significantly elevated, and current studies reveal that copper ions are involved in the development, growth and metastasis of tumors through various pathways. Moreover, recent studies have shown that copper ions can regulate the expression of PD-L1, thus, attention should be paid to the important role of copper in tumor immunity. By exploring and studying copper ions and tumor immunity, new insights into tumor immunity could be generated and novel therapeutic approaches to improve the clinical prognosis of patients can be provided.
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