8-bromo-5-hydroxy-7-methoxychrysin targeting for inhibition of the properties of liver cancer stem cells by modulation of Twist signaling

Isovitexin Suppresses Stemness of Lung Cancer Stem-Like Cells through Blockage of MnSOD/CaMKII/AMPK Signaling and Glycolysis Inhibition

BACKGROUND

Manganese superoxide dismutase (MnSOD) has been reported to promote stemness of lung cancer stem-like cells (LCSLCs) which had higher glycolytic rates compared with non-CSLCs. Isovitexin exhibited an inhibitory effect on the stemness of hepatocellular carcinoma cells. However, whether isovitexin could inhibit the promotion of stemness of LCSLCs mediated by MnSOD through glycolysis remains unclear.

OBJECTIVE

Our study was aimed at investigating whether isovitexin inhibits lung cancer stem-like cells (LCSLCs) through MnSOD signaling blockage and glycolysis suppression.

METHODS

Sphere formation and soft agar assays were conducted to determine self-renewal ability. The migration and invasion of LCSLCs were determined by wound healing and transwell assay. The glycolytic activity was assessed by determination of L-lactate metabolism rate. The influences of isovitexin on MnSOD, CaMKII, and AMPK activations as well as the metabolic shift to glycolysis were determined by manipulating MnSOD expression.

RESULTS

It was found that MnSOD and glycolysis enhanced simultaneously in LCSLCs compared with parental H460 cells. Overexpression of MnSOD activated CaMKII/AMPK signaling and glycolysis in LCSLCs with increased self-renewal, migration, invasion, and expression of stemness-associated markers in vitro and elevated carcinogenicity in vivo. Knockdown of MnSOD induced an inverse effect in LCSLCs. Isovitexin blocked MnSOD/CaMKII/AMPK signaling axis and suppressed glycolysis in LCSLCs, resulting in inhibition of stemness features in LCSLCs. The knockdown of MnSOD significantly augmented isovitexin-associated inhibition of CaMKII/AMPK signaling, glycolysis, and stemness in LCSLCs. However, the overexpression of MnSOD could attenuate the inhibition of isovitexin on LCSLCs. Importantly, isovitexin notably suppressed tumor growth in nude mice bearing LCSLCs by downregulation of MnSOD expression.

CONCLUSION

MnSOD promotion of stemness of LCSLCs derived from H460 cell line is involved in the activation of the CaMKII/AMPK pathway and induction of glycolysis. Isovitexin-associated inhibition of stemness in LCSLCs is partly dependent on blockage of the MnSOD/CaMKII/AMPK signaling axis and glycolysis suppression.

Synthesis of chrysin derivatives and screening of antitumor activity

A series of aromatic or long-chain chrysin derivatives (1-10) were synthesized by esterification of chrysin and acyl chloride. The chemical structures of these compounds were determined by mass spectrum (MS), ¹H NMR, and ¹³C NMR spectra. Though aromatic chrysin derivatives (1-9) with a rigid structure were hard to dissolve in common organic solvents, the long-chain chrysin derivative (10) with a flexible structure had better solubility, and its anticancer activity (IC₅₀ = 14.79 μmol/L) against liver cancer cell lines was 5.4 times better than chrysin (IC₅₀ = 74.97 μmol/L), which showed superposition of pharmacological activity.

8-bromo-7-methoxychrysin targets NF-κB and FoxM1 to inhibit lung cancer stem cells induced by pro-inflammatory factors

We have previously reported that 8-bromo-7-methoxychrysin (BrMC), a novel synthetic derivative of chrysin, was demonstrated anti-tumor activities against several human cancers, including lung cancer. Interaction between inflammation and cancer stem cell are recently increasingly recognized in tumorigenesis and progression. The purpose of this study was to investigate whether BrMC inhibits lung cancer stemness of H460 cells induced by inflammatory factors (TGF-β combined with TNF-α) and its potential mechanism. Our results showed that BrMC inhibited lung cancer stemness, as validated by enhanced self-renewal ability, higher in vitro tumorigenicity, and increased expression of CD133, CD44, Bmi1 and Oct4 in H460 cells administered TNF-α after prolonged induction by TGF-β, in a concentration-dependent manner. Both NF-κB inhibition by SN50 and FoxM1 suppression by thiostrepton (THI) prompted the inhibition of BrMC on lung CSCs. Conversely, overexpression of NF-κBp65 significantly antagonized the above effects of BrMC. Meanwhile, overexpression of FoxM1 also significantly compromised BrMC function on suppression of FoxM1 and NF-κBp65 as well as stemness of lung CSCs. Our results suggest that activation of NF-κB and FoxM1 by cytokines facilitate the acquisition CSCs phenotype, and compromise the chemical inhibition, which may represent an effective therapeutic target for treatment of human lung cancer. Moreover, BrMC may be a potential promising candidate for targeting NF-κB/ FoxM1 to prevent the tumorigenesis under inflammatory microenvironment.

8-bromo-7-methoxychrysin suppress stemness of SMMC-7721 cells induced by co-culture of liver cancer stem-like cells with hepatic stellate cells

BACKGROUND

Our previous works have demonstrated that 8-bromo-7-methoxychrysin suppressed stemness of human hepatocellular carcinoma (HCC) cell line SMMC-7721 induced by condition medium from hepatic stellate cell line LX-2 that was activated by liver cancer stem-like cells (LCSCs). However, whether and whereby BrMC inhibits the stemness induced by co-culture of LCSCs and LX-2 cells remains to be investigated.

METHODS

The second-generation spheres by sphere culture were identified and used as SMMC-7721-and MHCC97H-derived LCSLCs. SMMC-7721-and MHCC97-derived LCSCs/LX-2 cells transwell co-culture system was treated with BrMC and its lead compound chrysin. The concentrations of IL-6, IL-8, HGF and PDGF in condition medium from co-culture were measured by enzyme-linked immunosorbent assay (ELISA). The stemness of SMMC-7721 cells was evaluated by sphere formation assay and western blot analysis for expression levels of cancer stem cell markers (CD133 and CD44).The expression levels of cancer-associated fibroblast markers (FAP-α and α-SMA) were employed to evaluate pathologic activation of LX-2 cells. Addition of IL-6 and/or HGF or deletion of IL-6 and/or HGF was conducted to investigate the mechanisms for BrMC and chrysin treatment in SMMC-7721-derived LCSLCs co-cultured with LX-2cells.

RESULTS

The co-culture of LCSLCs with LX-2 cells increased sphere formation capability as well as expression of CD133 and CD44 in SMMC-7721 cells, meanwhile, upregulated expression of FAP-α in LX-2 cells. ELISA indicated that the concentrations of IL-6 and HGF were significantly elevated in Co-CM than that of condition media from co-cultured SMMC-7721 cells/LX-2 cells. Treatment of BrMC and chrysin with co-cultures of SMMC-7721- and MHCC97H-derived LCSLCs and LX-2 cells effectively inhibited the above responses. Moreover, addition of IL-6 and/or HGF induced stemness of SMMC-7721 cells and activation of LX-2 cells, conversely, deletion of IL-6 and/or HGF suppressed those. Furthermore, the inhibitory effects of BrMC and chrysin on stemness of SMMC-7721 cells and activation of LX-2 cells were attenuated by addition of IL-6 or HGF, and enhanced by deletion of IL-6 or HGF.

CONCLUSIONS

Our results suggest IL-6 and HGF may be the key communication molecules for the interaction between LCSLCs and HSCs, and BrMC and chrysin could block these effects and be the novel therapeutic candidates for HCC management.

Targeting liver cancer stem cells for the treatment of hepatocellular carcinoma

Liver cancer is one of the most common malignant tumors and prognosis remains poor. It has been increasingly recognized that liver cancer stem cells (LCSCs) are responsible for the carcinogenesis, recurrence, metastasis and chemoresistance of hepatocellular carcinoma (HCC). Targeting LCSCs is promising to be a new direction for the treatment of HCC. Herein, we summarize the potentially therapeutic targets in LCSCs at the level of genes, molecules and cells, such as knockout of oncogenes or oncoproteins, restoring the silent tumor suppressor genes, inhibition of the transcription factors and regulation of noncoding RNAs (including microRNAs and long noncoding RNAs) in LCSCs at the genetic level; inhibition of markers and blockade of the key signaling pathways of LCSCs at the molecular level; and inhibiting autophagy and application of oncolytic adenoviruses in LCSCs at the cellular level. Moreover, we analyze the potential targets in LCSCs to eliminate chemoresistance of HCC. Thereinto, the suppression of autophagy and Nanog by chloroquine and shRNA respectively may be the most promising targeting approaches. These targets may provide novel therapeutic strategies for the treatment of HCC by targeting LCSCs.

An AIE-based self-assembled fluorescent probe for COX-2 imaging

The first AIE-based fluorescent probe TPI-IMC was developed for imaging of cyclooxygenase-2 (COX-2) in normal cells and cancer cells.

Upregulation of FoxM1 by MnSOD Overexpression Contributes to Cancer Stem-Like Cell Characteristics in the Lung Cancer H460 Cell Line

Manganese superoxide dismutase promotes migration and invasion in lung cancer cells via upregulation of the transcription factor forkhead box M1. Here, we assessed whether upregulation of forkhead box M1 by manganese superoxide dismutase overexpression mediates the acquisition of cancer stem-like cell characteristics in non-small cell lung cancer H460 cells. The second-generation spheroids from H460 cells were used as lung cancer stem-like cells. The levels of manganese superoxide dismutase, forkhead box M1, stemness markers (CD133, CD44, and ALDH1), and transcription factors (Bmi1, Nanog, and Sox2) were analyzed by Western blot. Sphere formation in vitro and carcinogenicity of lung cancer stem-like cells were evaluated by spheroid formation assay and limited dilution xenograft assays. Knockdown or overexpression of manganese superoxide dismutase or/and forkhead box M1 by transduction with short hairpin RNA(shRNA) or complementary DNA were performed for mechanistic studies. We showed that manganese superoxide dismutase and forkhead box M1 amounts as well as the expression levels of stemness markers and transcription factors sphere formation in vitro, and carcinogenicity of lung cancer stem-like cells were higher than in monolayer cells. Lung cancer stem-like cells transduced with manganese superoxide dismutase shRNA or FoxM1 shRNA exhibited decreased sphere formation and lower amounts of stemness markers and transcription factors. Overexpression of manganese superoxide dismutase or FoxM1 in H460 cells resulted in elevated sphere formation rates and protein levels of stemness markers and transcription factors. Meanwhile, manganese superoxide dismutase knockdown or overexpression accordingly altered forkhead box M1 levels. However, forkhead box M1 knockdown or overexpression had no effect on manganese superoxide dismutase levels but inhibited or promoted lung cancer stem-like cell functions. Interestingly, forkhead box M1 overexpression alleviated the inhibitory effects of manganese superoxide dismutase knockdown in lung cancer stem-like cells. In a panel of non-small cell lung cancer cells, including H441, H1299, and H358 cells, compared to the respective monolayer counterparts, the expression levels of manganese superoxide dismutase and forkhead box M1 were elevated in the corresponding spheroids. These findings revealed the role of forkhead box M1 upregulation by manganese superoxide dismutase overexpression in maintaining lung cancer stem-like cell properties. Therefore, inhibition of forkhead box M1 upregulation by manganese superoxide dismutase overexpression may represent an effective therapeutic strategy for non-small cell lung cancer.

A Forkhead Box Protein C2 Inhibitor: Targeting Epithelial-Mesenchymal Transition and Cancer Metastasis

The epithelial-mesenchymal transition (EMT) has been suggested as a new target for therapeutic intervention of metastatic cancer. Forkhead box protein C2 (FOXC2) is known to be necessary for initiating and maintaining EMT, and therefore bestows on cancer cells metastatic and cancer stem cell (CSC)-like phenotypes, allowing cells to acquire higher motility, invasiveness, self-renewal, and therapy resistance. Here, we describe the first inhibitor of FOXC2, MC-1-F2. MC-1-F2 was able to induce cadherin switching and reverse EMT through the degradation of FOXC2 and blocking of its nuclear localization. In addition, MC-1-F2 was very effective in inhibiting cancer cell migration and invasion. As the first small-molecule inhibitor of FOXC2 and the first compound targeting EMT-associated transcription factor, MC-1-F2 will pave the way for a new anticancer therapeutic agent targeting metastatic cancer and help to elucidate the network of EMT signaling pathways.

Lovastatin Inhibits Cancer Stem Cells and Sensitizes to Chemo- and Photodynamic Therapy in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus-associated malignancy occurring at high incidence in Southeast Asia and southern China. In spite of the good response to radio- and chemo-therapy at the early stage, resistance and recurrence develop in NPC patients in the advanced setting. Cancer stem cells (CSCs) play an important role in drug resistance and cancer recurrence. Here we report that lovastatin, a natural compound and a lipophilic statin that has already been used in the clinic to treat hypercholesterolemia, inhibited the CSC properties and induced apoptosis and cell cycle arrest in sphere-forming cells derived from the 5-8F and 6-10B NPC cell lines. Furthermore, lovastatin conferred enhanced sensitivity to the chemotherapeutic and photodynamic agents in NPC CSCs. Together our findings suggest that targeting CSCs by lovastatin in combination with routine chemotherapeutic drugs or photodynamic therapy might be a promising approach to the treatment of NPC.

8-Bromo-7-methoxychrysin-blocked STAT3/Twist axis inhibits the stemness of cancer stem cell-like cell originated from SMMC-7721 cells

Signal transducer and activator of transcription 3 (STAT3) is a member of the family of latent cytoplasmic transcriptional factors that could regulate cell proliferation, survival, and development. It has been reported that Twist is a target gene of STAT3, and STAT3/Twist signaling plays an important role in regulating cancer progress. Here, to explore whether 8-bromo-7-methoxychrysin (BrMC) inhibits liver cancer stem-like cell (LCSLC) properties via disrupting STAT3/Twist signaling, we cultured SMMC-7721 cells in vitro, and evaluated the effects of BrMC on the stemness of spheroids by determining the sphere-forming capability and migration. The sphere formation assay results showed a concentration-dependent decrease of sphere-forming capacity in LCSLCs (P < 0.05) treated with different concentrations of BrMC. Wound-healing assays results demonstrated a concentration-dependent decline in cell migration of LCSLCs treated with different concentrations of BrMC. In addition, CD133, CD44, and ALDH1 levels were decreased in LCSLCs treated with BrMC. Treatment with different concentrations of BrMC also reduced the expressions of p-STAT3 and Twist1 proteins. The effect of BrMC was substantially enhanced by co-treatment with JSI-124, a specific inhibitor of STAT3. Ectopic expression of Twist1 attenuated the inhibitory effects of BrMC on sphere formation, migration, and expression of the markers in LCSLCs. However, it had no affect on p-STAT3 expression in LCSLCs. These results demonstrated that BrMC inhibits the stemness of LCSLCs originated from SMMC-7721 cell line by inhibiting STAT3/Twist signal axis.

Synergistic inhibition of characteristics of liver cancer stem-like cells with a combination of sorafenib and 8-bromo-7-methoxychrysin in SMMC-7721 cell line

Sorafenib, a multi-kinase inhibitor, has shown its promising antitumor effect in a series of clinical trials, and has been approved as the current standard treatment for advanced hepatocellular carcinoma (HCC). 8-Bromo‑7-methoxychrysin (BrMC) is a novel chrysin synthetic analogue that has been reported to inhibit the growth of various tumor cells and possess properties for targeting liver cancer stem cells (LCSCs) . The present study investigated the synergistic targeting effects on the properties of liver cancer stem-like cells (LCSLCs) by a combination of sorafenib and BrMC in SMMC-7721 cell line. We also investigated whether this effect involves regulation of HIF-1α, Twist and NF-κB protein. We found that the sphere-forming cells (SFCs) from the SMMC‑7721 cells possessed the properties of LCSLCs. Sorafenib diminished the self-renewal capacity and downregulated the expression of stem cell biomarkers (CD133, CD44 and ALDH1) in a dose-dependent manner, while BrMC cooperated with sorafenib to strengthen this inhibition. Moreover, the combination of sorafenib and BrMC led to a remarkable decrease in the cellular migration and invasion, the downregulation of N-cadherin protein and upregulation of E-cadherin protein, and increase of cell apoptosis in LCSLCs. BrMC has a remarkable antagonistic effect on the upregulation of protein expression and DNA binding activity of NF-κB (p65) induced by sorafenib. In addition, our results indicated that the synergistic inhibition of sorafenib and BrMC on the characteristics of LCSLCs involves the downregulated expression of HIF-1α and EMT regulator Twist1. Collectively, the combination therapy of sorafenib and BrMC could be a new and promising therapeutic approach in the treatment of HCC.

Deciphering the molecular mechanisms underlying the binding of the TWIST1/E12 complex to regulatory E-box sequences

The TWIST1 bHLH transcription factor controls embryonic development and cancer processes. Although molecular and genetic analyses have provided a wealth of data on the role of bHLH transcription factors, very little is known on the molecular mechanisms underlying their binding affinity to the E-box sequence of the promoter. Here, we used an in silico model of the TWIST1/E12 (TE) heterocomplex and performed molecular dynamics (MD) simulations of its binding to specific (TE-box) and modified E-box sequences. We focused on (i) active E-box and inactive E-box sequences, on (ii) modified active E-box sequences, as well as on (iii) two box sequences with modified adjacent bases the AT- and TA-boxes. Our in silico models were supported by functional in vitro binding assays. This exploration highlighted the predominant role of protein side-chain residues, close to the heart of the complex, at anchoring the dimer to DNA sequences, and unveiled a shift towards adjacent ((-1) and (-1*)) bases and conserved bases of modified E-box sequences. In conclusion, our study provides proof of the predictive value of these MD simulations, which may contribute to the characterization of specific inhibitors by docking approaches, and their use in pharmacological therapies by blocking the tumoral TWIST1/E12 function in cancers.

Reversal of liver cancer-associated stellate cell-induced stem-like characteristics in SMMC-7721 cells by 8-bromo-7-methoxychrysin via inhibiting STAT3 activation

Hepatic stellate cells (HSCs) that are activated by human hepatocellular carcinoma (HCC) cells secrete a variety of cytokines, which are the main component of the HCC microenvironment. We aimed to determine whether 8-bromo-7-methoxychrysin (BrMC) could interfere in cross-talk of the human hepatic stellate cell line LX-2 and liver cancer stem-like cells (LCSLCs) to inhibit the characteristics of LCSLCs endowed with the capacity of sustaining human hepatocellular carcinoma (HCC) self-renewal and progression, and to identify its potential mechanism of action. We found that the levels of fibroblast activation protein (FAP) were augmented in LX-2 cells treated with the conditioned medium of LCSLCs (LCSLC-CM) compared to those cultured with routine medium, indicating that the LCSLC-CM can activate LX-2 cells to become liver cancer-associated stellate cells (LCAHSCs). Furthermore, sphere forming capability of SMMC-7721 cells was enhanced and stem cell-related protein expression was significantly increased following treatment with the conditioned medium of LCAHSCs (LCAHSC-CM). Moreover, the level of p-STAT3 was increased in LX-2 cells treated with LCSLC-CM and BrMC reduced expression of p-STAT3. Combination of BrMC and the selective inhibitor of STAT3 cucurbitacin I (JSI-124) synergistically suppressed the LCSLC characteristics in SMMC-7721 cells. Collectively, our data showed that BrMC inhibited the interaction between LX-2 cells and HCC-derived CSCs, and did so potentially through modulation of the STAT3 pathway. Future therapeutic strategies employing anti-CSC therapy should confirm the potential of cucurbitacin I (JSI-124) and BrMC as potent therapeutic agents.

Curcumin Suppresses Phthalate-Induced Metastasis and the Proportion of Cancer Stem Cell (CSC)-like Cells via the Inhibition of AhR/ERK/SK1 Signaling in Hepatocellular Carcinoma

Recent evidence indicating that phthalates promote cancer development, including cell proliferation, migration, and invasion, has raised public health concerns. Here, we show that bis(2-ethylhexyl) phthalate promotes the migration, invasion, and epithelial-mesenchymal transition of hepatocellular carcinoma cells. In addition, bis(2-ethylhexyl) phthalate increased the proportion of cancer stem cell (CSC)-like cells and stemness maintenance in vitro as well as tumor growth and metastasis in vivo. The various activities of curcumin, including anticancer, anti-inflammation, antioxidation, and immunomodulation, have been investigated extensively. Curcumin suppressed phthalate-induced cell migration, invasion, and epithelial-mesenchymal transition, decreased the proportion of CSC-like cells in hepatocellular carcinoma cell lines in vitro, and inhibited tumor growth and metastasis in vivo. We also reveal that curcumin suppressed phthalate-induced migration, invasion, and CSC-like cell maintenance through inhibition of the aryl hydrocarbon receptor/ERK/SK1/S1P3 signaling pathway. Our results suggest that curcumin may be a potential antidote for phthalate-induced cancer progression.