br Fig DSC suppresses the
Fig. 2. 3-DSC suppresses the growth of colon cancer cells. (A) Eﬀect of 3-DSC on the proliferation of colon cancer cells, HCT-15, HCT116, SW620, and DLD1 was assessed at 24, 48, and 72 h by the MTT assay. The asterisks indicate a significant decrease in proliferation compared with the vehicle control (*p < 0.01, **p < 0.001). (B) The eﬀect of 3-DSC on the anchorage-independent colony growth of colon cancer cells was evaluated. The asterisks (**p < 0.001) indicate a significant decrease (percentage) in colony numbers in cells treated with 5, 10 or 20 μM 3-DSC, as compared with untreated controls. (C) Representative photographs of anchorage-independent cell growth assay results of cells treated or not treated with 3-DSC.
Fig. 3. 3-DSC inhibits cell proliferation by the induction of cell cycle arrest at the G2/M phase. (A) Analysis of results from the cell cycle assay. (B) Plots indicating cell cycle distribution. (C) Expression of cell cycle markers in colon cancer cell lines. Cells were treated with 0, 5, 10, or 20 μM 3-DSC and then incubated for 48 h. The asterisks (**p < 0.001) indicate a significant diﬀerence between untreated controls and treated cells.
cascades, including the mitogen-activated protein kinases, ERKs, RSKs, several transcription factors, such as activation protein (AP)-1 and nuclear factor kappa-light-chain-enhancer of activated 13C6-3-Nitrophenylhydrazine (NF-κB), thereby promoting cell proliferation, migration, and invasion (Aksamitiene et al., 2010; Oh et al., 2007; Park et al., 2014). Colorectal cancer (CRC) is one of the most common causes of cancer-related deaths worldwide. According to the latest figures, CRC patients cur-rently number 95,520 and this cancer will lead to around 50,260 deaths in the United States (Siegel et al., 2017). Zhu et al. reported that TOPK is highly expressed in human colorectal cancer tissues and cell lines, and that it promotes tumorigenesis of colorectal cancers by its phos-phorylation of ERKs (Zhu et al., 2007). Thus TOPK might be a potential target for chemotherapeutic or chemopreventive agents in colon cancer. 3-DSC ((2E)-1-(4-Hydroxy-2-methoxyphenyl)-3-(4-hydro-xyphenyl)-2-propen-1-one, 3-deoxysappanchalcone) is a biologically active compound that is found in the roots and heartwood of the Cae-salpinia sappan L. plant (Yodsaoue et al., 2009). 3-DSC has been re-ported to have anti-allergic activity and to inhibit antigen-induced beta-hexaminidase release in rat basophilic leukemic RBL-2H3 cells (Yodsaoue et al., 2009). 3-DSC reportedly has anti-inflammatory
activity and protects against influenza virus-induced inflammation of endothelial cells by suppressing secretion of chemokine (CeC motif) ligand 5 and C-X-C motif chemokine 10 (Yang et al. 2012). Also, 3-DSC promotes hair growth in vitro and in vivo in mice by modulating the WNT/β-catenin and JAK-STAT intracellular signaling pathways, which increases the proliferation of hair follicle dermal papilla cells (Kim et al., 2016; Yang et al., 2012; Yodsaoue et al., 2009).
In this study, we examined the anticancer activity of 3-DSC and showed that 3-DSC could inhibit colorectal cancer cell growth by di-rectly inhibiting TOPK kinase activity and its down-stream signaling eﬀectors.
Materials and methods
3-DSC (purity ≥95% from HPLC and NMR analysis) was purchased from ChemFaces (Wuhan, Hubei, China) (Supplementary Fig. 1A–C). Active TOPK, MEK1, inactive ERK1 (MEK substrate), and MBP human recombinant proteins for kinase assays were purchased from Signal
Fig. 4. 3-DSC induces apoptosis. (A) Analysis of the results of the apoptosis assay. (B) Plots of apoptotic cell populations. (C) Expression of apoptosis markers in colon cancer cell lines. Cells were treated with 0, 5, 10 or 20 μM 3-DSC and then incubated for 72 h. The asterisks (**p < 0.001) indicate a significant diﬀerence between untreated controls and treated cells.
Fig. 5. 3-DSC suppresses TOPK-signaling in colon cancer cells. Cells were treated with vehicle or 5, 10, or 20 μM 3-DSC for 24 h. The proteins were ex-tracted and the expression levels of pTOPK, total TOPK, pERKs, total ERKs, pRSK, total RSK, pc-Jun, and total c-Jun were detected by Western blotting, using specific antibodies as indicated. β-Actin was used as a loading control.
Chem (Richmond, BC, Canada) or Sigma Aldrich (St. Louis, MO, USA). Antibodies to detect phosphorylated TOPK (pTOPK), total TOPK, phosphorylated MEK (pMEK), total MEK, phosphorylated ERKs (pERKs), total ERKs, phosphorylated RSK (pRSK), total RSK, phos-phorylated c-Jun (pc-Jun), total c-Jun, p21, PARP, caspase-3, caspase-7, cleaved PARP, cleaved caspase-3, and cleaved caspase-7 were pur-chased from Cell Signaling Technology (Beverly, MA, USA).