Zu-Hua Gao

Chemoprevention of intestinal adenomatous polyposis by acetyl‐11‐keto‐beta‐boswellic acid in APCMin/+ mice

Acetyl‐11‐keto‐beta‐boswellic acid (AKBA) is a derivative of boswellic acid, which is an active component of the gum resin of Boswellia serrata. AKBA has been used as an adjuvant medication for treatment of inflammatory diseases. In this study, we aimed to evaluate the efficacy of AKBA as a chemopreventive agent against intestinal adenomatous polyposis in the adenomatous polyposis coli multiple intestinal neoplasia (APCMin/+) mouse model. APCMin/+ mice were administered AKBA by p.o. gavage for 8 consecutive weeks. The mice were sacrificed and the number, size and histopathology of intestinal polyps were examined by light microscopy. AKBA decreased polyp numbers by 48.9% in the small intestine and 60.4% in the colon. An even greater AKBA effect was observed in preventing the malignant progression of these polyps. The number of large (>3 cm) colonic polyposis was reduced by 77.8%. Histopathologic analysis demonstrated a significant reduction in the number of dysplastic cells and in the degree of dysplasia in each polyp after AKBA treatment. There was no evidence of high grade dysplasia or intramucosal carcinoma in any of the polyps examined within the treated group. More interestingly, interdigitated normal appearing intestinal villi were observed in the polyps of the treated group. During the course of the study, AKBA was well tolerated by the mice with no obvious signs of toxicity. Results from immunohistochemical staining, Western blotting and enzyme‐linked immunosorbent assay indicated that the chemopreventive effect of AKBA was attributed to a collection of activities including antiproliferation, apoptosis induction, antiangiogenesis and anti‐inflammation. AKBA was found to exert its chemopreventive action through the inhibition of the Wnt/β‐catenin and NF‐κB/cyclooxygenase‐2 signaling pathways. Our findings suggest that AKBA could be a promising regimen in chemoprevention against intestinal tumorigenesis.

The Adverse Effects of Sorafenib in Patients with Advanced Cancers

Sorafenib is the first multi-kinase inhibitor (TKI) approved for the treatment of advanced hepatocellular cancer (HCC) and metastatic renal cell cancer (RCC) and is increasingly being used to treat patients with well-differentiated radioiodine-resistant thyroid cancer (DTC). Sorafenib demonstrates targeted activity on several families of receptor and non-receptor tyrosine kinases that are involved in angiogenesis, tumour growth and metastatic progression of cancer. Sorafenib treatment results in long-term efficacy and low incidence of life-threatening toxicities. Although sorafenib has demonstrated many benefits in patients, the adverse effects cannot be ignored. The most common treatment-related toxicities include diarrhoea, fatigue, hand-foot skin reaction and hypertension. Most of these toxicities are considered mild to moderate and manageable to varying degrees; however, cardiovascular events might lead to death. In this MiniReview, we summarize the adverse effects of sorafenib that commonly occur in patients with advanced cancers.

RETRACTED: Acetyl-11-keto-β-boswellic acid (AKBA) inhibits human gastric carcinoma growth through modulation of the Wnt/β-catenin signaling pathway

BACKGROUNDnAcetyl-11-keto-beta-boswellic acid (AKBA) is a derivative of boswellic acid, an active component of Boswellia serrata gum resin. We examined the effect of AKBA on human gastric carcinoma growth and explored the underlying molecular mechanisms.nnnMETHODSnInhibition of cancer cell growth was estimated by colorimetric and clonogenic assays. Cell cycle distribution was analyzed by flow cytometry and apoptosis determined using Annexin V-FITC/PI staining and DNA ladder quantification. After three weeks of oral AKBA administration in nude mice bearing cancer xenografts, animals were sacrificed and xenografts removed for TUNEL staining and western blot analysis.nnnRESULTSnAKBA exhibited anti-cancer activity in vitro and in vivo. With oral application in mice, AKBA significantly inhibited SGC-7901 and MKN-45 xenografts without toxicity. This effect might be associated with its roles in cell cycle arrest and apoptosis induction. The results also showed activation of p21(Waf1/Cip1) and p53 in mitochondria and increased cleaved caspase-9, caspase-3, and PARP and Bax/Bcl-2 ratio after AKBA treatment. Further analysis suggested that these effects might arise from AKBAs modulation of the aberrant Wnt/β-catenin signaling pathway. Upon AKBA treatment, β-catenin expression in nuclei was inhibited, and membrane β-catenin was activated. In the same sample, active GSK3β was increased and its non-active form decreased. Levels of cyclin D1, PCNA, survivin, c-Myc, MMP-2, and MMP-7, downstream targets of Wnt/β-catenin, were inhibited.nnnCONCLUSIONSnAKBA effects on human gastric carcinoma growth were associated with its activity in modulating the Wnt/β-catenin signaling pathway.nnnGENERAL SIGNIFICANCEnAKBA could be useful in the treatment of gastric cancers.

Des-gamma-carboxy prothrombin antagonizes the effects of Sorafenib on human hepatocellular carcinoma through activation of the Raf/MEK/ERK and PI3K/Akt/mTOR signaling pathways

Despite significant progress, advanced hepatocellular carcinoma (HCC) remains an incurable disease, and the overall efficacy of targeted therapy by Sorafenib remains moderate. We hypothesized that DCP (des-gamma-carboxy prothrombin), a prothrombin precursor produced in HCC, might be one of the reasons linked to the low efficacy of Sorafenib. We evaluated the efficacy of Sorafenib in HLE and SK-Hep cells, both of which are known DCP-negative HCC cell lines. In the absence of DCP, Sorafenib effectively inhibited the growth of HCC and induced cancer cell apoptosis. In the presence of DCP, HCC was resistant to Sorafenib-induced inhibition and apoptosis, as determined by in vitro assays and in mice xenografted with HLE cells. Molecular analysis of HLE xenografted-nude mice showed that DCP activates the transduction of the Ras/Raf/MEK/ERK and Ras/PI3K/Akt/mTOR cascades. DCP might stimulate the formation of compensatory feedback loops in the intricately connected signaling pathways when kinases are targeted by Sorafenib. Our results indicate that DCP antagonizes the inhibitory effects of Sorafenib on HCC through activation of the Ras/Raf/MEK/ERK and Ras/PI3K/Akt/mTOR signaling pathways. Taken together, our findings define a DCP-mediated mechanism of inhibition of Sorafenib in HCC, which is critical for targeting therapy in advanced HCC.

RETRACTED: Acetyl-11-keto-beta-boswellic acid (AKBA) prevents human colonic adenocarcinoma growth through modulation of multiple signaling pathways

BACKGROUNDnAcetyl-11-keto-beta-boswellic acid (AKBA) is a derivative of boswellic acid. We have previously reported that AKBA can reduce the number and size of colonic adenomatous polyps in the APC(Min/+) mouse model. In this study, we evaluated the effect of AKBA on human colonic adenocarcinoma growth. Its efficacy and toxicity were compared with those of the non-steroidal anti-inflammatory drug aspirin.nnnMETHODSnThe inhibition of cancer cell growth was estimated by colorimetric and clonogenic assay. Cell cycle distribution was analyzed by the flow cytometry assay. Annexin V-FITC/PI staining and JC-1 fluorescence probe assays were performed to determine the apoptotic cells. Further experiment was carried out in mice with HT-29 xenografts. AKBA was orally administered for 24days. The HT-29 xenografts were removed for TUNEL staining and western blotting analysis. Blood was obtained for clinical chemical analysis, and samples of organs were sectioned for microscopic assessment.nnnRESULTSnAKBA significantly inhibited human colon adenocarcinoma growth, showing arrest of the cell cycle in G1-phase and induction of apoptosis. AKBA administration in mice effectively delayed the growth of HT-29 xenografts without signs of toxicity. The activity of AKBA was more potent than that of aspirin. Western blotting suggested that this activity may arise from its multiple effects on the activation of apoptotic proteins, suppression of inflammatory cytokines and modulation of EGFR and ATM/P53 signaling pathways in the HT-29 xenografts.nnnCONCLUSIONSnAKBA prevents the growth of colonic adenocarcinoma through modulation of multiple signaling pathways.nnnGENERAL SIGNIFICANCEnAKBA could be a promising agent in the prevention of colonic adenocarcinomas.

Overexpression of SphK2 contributes to ATRA resistance in colon cancer through rapid degradation of cytoplasmic RXRα by K48/K63-linked polyubiquitination

The resistance mechanisms that limit the efficacy of retinoid therapy in cancer are poorly understood. Sphingosine kinase 2 (SphK2) is a highly conserved enzyme that is mainly located in the nucleus and endoplasmic reticulum. Unlike well-studied sphingosine kinase 1 (SphK1) located in the cytosol, little has yet understood the functions of SphK2. Here we show that SphK2 overexpression contributes to the resistance of all-trans retinoic acid (ATRA) therapy in colon cancer through rapid degradation of cytoplasmic retinoid X receptor α (RXRα) by lysine 48 (K48)- and lysine 63 (K63)-based polyubiquitination. Human colonic adenocarcinoma HCT-116 cells transfected with SphK2 (HCT-116Sphk2 cells) demonstrate resistance to ATRA therapy as determined by in vitro and in vivo assays. Sphk2 overexpression increases the ATRA-induced nuclear RXRα export to cytoplasm and then rapidly degrades RXRα through the polyubiquitination pathway. We further show that Sphk2 activates the ubiquitin-proteasome system through the signal mechanisms of (1) K48-linked proteosomal degradation and (2) K63-linked ubiquitin-dependent autophagic degradation. These results provide new insights into the biological functions of Sphk2 and the molecular mechanisms that underlie the Sphk2-mediated resistance to retinoid therapy.

Chemoprevention of intestinal tumorigenesis by the natural dietary flavonoid myricetin in APC Min/+ mice

Myricetin is a natural dietary flavonoid compound. We evaluated the efficacy of myricetin against intestinal tumorigenesis in adenomatous polyposis coli multiple intestinal neoplasia (APCMin/+) mice. Myricetin was given orally once a day for 12 consecutive weeks. APCMin/+ mice fed with myricetin developed fewer and smaller polyps without any adverse effects. Histopathological analysis showed a decreased number of dysplastic cells and degree of dysplasia in each polyp. Immunohistochemical and western blot analysis revealed that myricetin selectively inhibits cell proliferation and induces apoptosis in adenomatous polyps. The effects of myricetin were associated with a modulation the GSK-3β and Wnt/β-catenin pathways. ELISA analysis showed a reduced concentration of pro-inflammatory cytokines IL-6 and PGE2 in blood, which were elevated in APCMin/+ mice. The effect of myricetin treatment was more prominent in the adenomatous polyps originating in the colon. Further studies showed that myricetin downregulates the phosphorylated p38 MAPK/Akt/mTOR signaling pathways, which may be the mechanisms for the inhibition of adenomatous polyps by myricetin. Taken together, our data show that myricetin inhibits intestinal tumorigenesis through a collection of biological activities. Given these results, we suggest that myricetin could be used preventatively to reduce the risk of developing colon cancers.

Riccardin D, a Macrocyclic Bisbibenzy, Inhibits Human Breast Cancer Growth through the Suppression of Telomerase Activity

Riccardin D, a liverwort‐derived naturally occurring macrocyclic bisbibenzyl, has been found to exert anticancer effects in multiple cancer cell types. In this study, we investigated the effect and mechanism of Riccardin D on human breast cancer. Experiments were performed on human breast cancer MCF‐7 and MDA‐MB‐231 cells. The antitumour effects of Riccardin D were assessed by the 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide (MTT) assay and human breast cancer xenografts mice model. TRAPeze® XL Telomerase Detection assay was used for the detection of telomerase activity. γ‐H2AX foci formation was tested for the induction of DNA damage response. Cell cycle distribution was analysed by flow cytometry, and cell apoptosis was determined by annexin V‐FITC/PI staining, terminal deoxynucleotidyl transferase‐mediated dUTP nick end labelling (TUNEL) assay and Western blotting. Riccardin D effectively inhibited the growth of MCF‐7 and MDA‐MB‐231 cells in vitro. And Riccardin D also effectively delayed the growth of MCF‐7 and MDA‐MB‐231‐luc‐D3H2LN xenografts without significant loss of body‐weight. Further analysis suggested that Riccardin Ds effects may arise from its suppression of telomerase activity, which led to telomere dysfunction. Telomerase inhibition and telomere dysfunction could activate the canonical ataxia telangiectasia‐mutated (ATM) kinase‐mediated DNA damage response, as shown by elevated expression of γ‐H2AX, p‐ATM and p‐Chk2. This is finally followed by the induction of cell cycle arrest and apoptosis, as shown by the increase of TUNEL‐stained cells, caspase activation, PARP cleavage and the increase of bax/bcl‐2 ratio. Moreover, Riccardin D induced p53‐proficient MCF‐7 cells to arrest in G1 phase and p53‐deficient MDA‐MB‐231 cells to arrest in G2/M phase. Overall, these results demonstrate that Riccardin D may inhibit human breast cancer growth through suppression of telomerase activity.

CXCR7/CXCR4 heterodimer-induced histone demethylation: a new mechanism of colorectal tumorigenesis

Both chemokine receptors (CXCRs) 7 and 4 can facilitate immune cell migration and mediate a vast array of physiological and pathological events. Herein we report, in both human and animal studies, that these two CXCRs can form heterodimers in vivo and promote colorectal tumorigenesis through histone demethylation. Compared with adjacent non-neoplastic tissue, human colorectal cancer (CRC) tissue showed a significant higher expression of CXCR4 and CXCR7, which was colocalized in the cancer cell epithelium. The CXCR/CXCR4 heterodimerization was associated with increased histone demethylase JMJD2A. Villin-CXCR7-CXCR4 transgenic mice demonstrated a greater degree of exacerbated colitis and tumorigenesis than villin-CXCR7 and villin-CXCR4 mice. The CXCR7/CXCR4 heterodimerization also promoted APC mutation-driven colorectal tumorigenesis in APCMin/+/villin-CXCR7-CXCR4 mice. Further analysis showed that the CXCR7/CXCR4 heterodimer induced nuclear βarr1 recruitment and histone demethylase JMJD2A, leading to histone demethylation and resulting in transcription of inflammatory factors and oncogenes. This study uncovered a novel mechanism of colorectal tumorigenesis through the CXCR7/CXCR4 heterodimer-induced histone demethylation. Inhibition of CXCR7/CXCR4 heterodimer-induced histone demethylation could be an effective strategy for the prevention and treatment of colorectal cancer.