Effect of β-carotene on cancer cell stemness and differentiation in SK-N-BE(2)C neuroblastoma cells

Neuroblastoma is a solid tumor often diagnosed in childhood. While there have been intense efforts to develop a treatment for neuroblastoma, current therapies remain unsuccessful due to high rate of resistance and metastasis. Most cancers originate from a subset of self-renewing cells, primarily cancer stem cells (CSCs), which establish a tumor through continuous self-renewal and differentiation. The successful elimination of CSCs is an important goal in the development of effective strategies to achieve complete remission for cancers. Although β-carotene has been associated with several anticancer mechanisms, the efficacy of β-carotene against CSCs remains unclear. In the present study, β-carotene was shown to reduce cell growth and induce neuronal cell differentiation, concomitant with a marked increase in the phosphorylation of extracellular signal-regulated kinases (ERK) (p42/p44). More importantly, β-carotene inhibited self-renewal characteristics of CSCs and decreased expression of several stem cell markers. Levels of mRNA and protein of Drosophila delta-like 1 homolog (Drosophila) (DLK1) were downregulated following treatment with β-carotene. In addition, knockdown of DLK1 by siRNA enhanced the inhibitory effect of β-carotene on colony formation of neuroblastoma cells. β-carotene also potentiated the effect of cisplatin on the self-renewal characteristics of CSCs in neuroblastoma, revealing that β-carotene has the capacity to resensitize cells to cisplatin cytotoxicity by directly targeting CSCs. In conclusion, β-carotene was shown to strongly increase the anticancer efficacy against neuroblastoma cancer stem-like cells. Moreover, these results suggest that the targeting of CSCs is a novel mechanism of β-carotene. Thus, β-carotene is a potential chemotherapeutic reagent for this cancer.