Wnt/β-catenin signaling as a useful therapeutic target in hepatoblastoma

Abstract

Hepatoblastoma is a malignant tumor in the liver of children that generally occurs at the age of 2-3 years. There have been ample evidence from the preclinical as well as clinical studies suggesting the activation of Wnt/β-catenin signaling in hepatoblastoma, which is mainly attributed to the somatic mutations in the exon 3 of β-catenin gene. There is increased translocation of β-catenin protein from the cell surface to cytoplasm and nucleus and intracellular accumulation is directly linked to the severity of the cancer. Accordingly, the alterations in β-catenin and its target genes may be used as markers in the diagnosis and prognosis of pediatric live tumors. Furthermore, scientists have reported the therapeutic usefulness of inhibition of Wnt/β-catenin signaling in hepatoblastoma and this inhibition of signaling has been done using different methods including short interfering RNA (siRNA), miRNA and pharmacological agents. Wnt/β-catenin works in association with other signaling pathways to induce the development of hepatoblastoma including Yes-associated protein (YAP)1 (YAP-1), mammalian target of rapamycin (mTOR) 1 (mTOR-1), SLC38A1, glypican 3 (GPC3), nuclear factor κ-light-chain-enhancer of activated B cells (NF-kB), epidermal growth factor receptor, ERK1/2, tumor necrosis factor-α (TNF-α), regenerating islet-derived 1 and 3 α (REG1A and 3A), substance P (SP)/neurokinin-1 receptor and PARP-1. The present review describes the key role of Wnt/β-catenin signaling in the development of hepatoblastoma. Moreover, the role of other signaling pathways in hepatoblastoma in association with Wnt/β-catenin has also been described.

Keywords: NF-kB; TNF-α; Wnt; hepatoblastoma; β-catenin.

Figure 1. Different type of mutations including CTNNB1 gene may directly or indirectly activate the β-catenin signaling

There may be activation of glypican-3, NF-kB, GSK-3β, ERK1/2 and/or co-activator of β-catenin, i.e. FHL2. Activation of β-catenin signaling may induce different pathways to induce the development of hepatoblastoma including inhibition of TNF-α-dependent apoptosis, increase in the secretion of epithelial growth factor (EGF) and formation of complex of β-catenin with YAP-1 protein. This interaction may activate mTOR pathway to increase the expression of SLC38A1 (amino acid transporter) that may be critical in the development of hepatoblastoma. Abbreviations: mTOR, mammalian target of rapamycin; TNF-α, tumor necrosis factor-α.