Exogenous DKK‑3/REIC inhibits Wnt/β‑catenin signaling and cell proliferation in human kidney cancer KPK1

Abstract

Abstract. The third member of the Dickkopf family (DKK-3), also known as reduced expression in immortalized cells (REIC), is a tumor suppressor present in a variety of tumor cells. Regarding the regulation of the Wnt/β-catenin signaling pathway, exogenous DKK-1 and DKK-2 are reported to inhibit Wnt signaling by binding the associated effectors. However, whether exogenous DKK-3 inhibits Wnt signaling remains unclear. A recombinant protein of human full-length DKK-3 was used to investigate the exogenous effects of the protein in vitro in KPK1 human renal cell carcinoma cells. It was demonstrated that the expression of phosphorylated (p-)β-catenin (inactive form as the transcriptional factor) was increased in KPK1 cells treated with the exogenous DKK-3 protein. The levels of non-p-β-catenin (activated form of β-catenin) were consistently decreased. It was revealed that the expression of transcription factor (TCF) 1 and c-Myc, the downstream transcription factors of the Wnt/β-catenin signaling pathway, was inhibited following treatment with DKK-3. A cancer cell viability assay confirmed the anti-proliferative effects of exogenous DKK-3 protein, which was consistent with a suppressed Wnt/β-catenin signaling cascade. In addition, as low-density lipoprotein receptor-related protein 6 (LRP6) is a receptor of DKK-1 and DKK-2 and their interaction on the cell surface inhibits Wnt/β-catenin signaling, it was examined whether the exogenous DKK-3 protein affects LRP6-mediated Wnt/β-catenin signaling. The LRP6 gene was silenced and the effects of DKK-3 on the time course of the upregulation of p-β-catenin expression were subsequently analyzed. Notably, LRP6 depletion elevated the base level of p-β-catenin; however, there was no significant effect on its upregulation course or expression pattern. These findings indicate that exogenous DKK-3 upregulates p-β-catenin and inhibits Wnt/β-catenin signaling in an LRP6-independent manner. Therefore, exogenous DKK-3 protein may inhibit the proliferation of KPK1 cells via inactivating Wnt/β-catenin signaling.

Bone secreted factors induce cellular quiescence in prostate cancer cells

“…We conducted a dose response analysis for each selected bone-secreted factors. We used factor concentrations reported in the literature 41–47 and tested several concentrations to ensure that the dosages used do not cause toxicity, i.e., cell death, in PCa cells using live-cell imaging. Based on the response, we selected the following concentrations for further study: DKK3 (10 µg/mL), BMP1 (0.4 µg/mL), vasorin (0.25 µg/mL), neogenin (0.5 µg/mL), MIA (0.1 µg/mL), or NGAL (0.25 µg/mL) (Fig.…”

“…Indeed, the high factor concentrations used in our studies are within the range reported in the literature. As an example, similar concentrations of human DKK3 at 10–50 µg/mL were used to block the proliferation of human kidney KPK1 cancer cells 41 ; human BMP1-3, an alternatively-spliced variant of BMP1, at 150–1000 ng/mL was observed to increase the expression of p21, a cell cycle inhibitor, in human embryonic kidney 293 (HEK293) cells 42 ; human MIA at 50 ng/mL was used to inhibit the invasive activity of melanoma cells 45 ; and PEDF at 250 ng/mL was used to induce osteoblastic differentiation of human mesenchymal stem cells 47 .…”

Functional Genomic Screening During Somatic Cell Reprogramming Identifies DKK3 as a Roadblock of Organ Regeneration

“…[ 20 , 65 ] The involvement of DKK3 in modulation of Wnt‐signaling has been extensively described. [ 27 , 28 , 66 ] As simple GSEA is frequently hampered in discriminating the repression or activation of a given pathway, we determined differentially regulated genes (DEG) at individual time points. [ 67 ] In line, the amount of DEGs increased over time with highest numbers at 96 h after induction of pancreatitis (Figure 6F ), an observation in concordance with our morphological observations.…”

Functional genomic screening during somatic cell reprogramming identifies Dkk3 as a roadblock of organ regeneration

“…[20,65] The involvement of DKK3 in modulation of Wnt-signaling has been extensively described. [27,28,66] As simple GSEA is frequently hampered in discriminating the repression or activation of a given pathway, we determined differentially regulated genes (DEG) at individual time points. [67] In line, the amount of DEGs increased over time with highest numbers at 96 h after induction of pancreatitis (Figure 6F), an observation in concordance with our morphological observations.…”