Keli Tian

Combination of curcumin and green tea catechins prevents dimethylhydrazine-induced colon carcinogenesis

The chemopreventive effects of curcumin and green tea catechins individually and in combination on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis were studied in male Wister rats following 32 weeks of dietary treatment. The incidence, number and size of colorectal cancer were measured. Colorectal aberrant crypt foci (ACF) were analyzed by methylene blue staining. Proliferation indices and apoptotic indices were determined by PCNA immunostaining and TUNEL assay, respectively. The results showed that dietary curcumin, catechins and combination administration significantly inhibited the total number of ACF per rat. The combination treatment displayed the most potent inhibitory effect, while there was no difference of inhibition between curcumin and catechins-treated groups. The incidence of colorectal cancer in the treated groups was significantly lower than that of positive control group. Compared with the positive control group, the proliferation index was significantly decreased and the apoptotic index was significantly increased in all treatment groups, while the effect of the combination was the greatest among the treated groups. Our findings suggest that the combination of curcumin and catechins may produce a synergistic colon cancer-preventative effect that would be more potent than each of the compounds alone.

Preventive action of curcumin in experimental acute pancreatitis in mouse.

Background & objectives: Curcuma longa (turmeric) has a long history of use in Ayurvedic medicine as a treatment for inflammatory conditions. The purpose of the present study was to investigate the preventive effects of curcumin against acute pancreatitis (AP) induced by caerulein in mouse and to elucidate possible mechanism of curcumin action. Methods: Curcumin (50 mg/kg/day) was intraperitoneally injected to Kun Ming male mice for 6 days, followed by injection of caerulein to induce AP. GW9662 (0.3 mg/kg), a specific peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, was intravenously injected along with curcumin. Murine macrophage RAW264.7 cells were treated with 100 μmol/l curcumin for 2 h, and then stimulated with 0.1 μ g/ml lipopolysaccharide (LPS). Serum amylase and transaminase levels were measured at 10 h after AP. TNF-α level in mouse serum and cell culture medium were detected by ELISA. Expression of PPARγ and NF-κB were analyzed by RT-PCR and Western blot. Results: Curcumin significantly decreased the pancreas injury and reversed the elevation of serum amylase, ALT and AST activities and TNF-α level in mice with AP. Curcumin treatment inhibited the elevation of NF-κB-p65 in the nucleus of mouse pancreas AP group and RAW264.7 cells, but significantly increased the expression of PPARγ. GW9662 could abolish the effects of curcumin on serum levels of amylase, ALT, AST, TNF-α, and NF-κB level. Interpretation & conclusions: Our results suggest that curcumin could attenuate pancreas tissue and other organ injury by inhibiting the release of inflammatory cytokine TNF-α. These effects may involve upregulation of PPARγ and subsequent downregulation of NF-κB.

Knockdown of AGR2 induces cellular senescence in prostate cancer cells

Anterior-gradient 2 (AGR2), overexpressed in many tumors including prostate cancer (PCa), is implicated in stimulation of cell proliferation, adhesion, anti-apoptosis and cell cycle regulation. Here, a potential role of AGR2 in cellular senescence was investigated. We first observed that AGR2 was overexpressed in Chinese Han PCa tissues and had a positive correlation with cyclin D1 and p-Rb but not with p16(INK4a). AGR2 expression profiles varied among cell lines, with PC3 cells being the highest level, LNCaP and DU145 relatively less. The expression of cyclin D1 showed similar pattern to the AGR2 in cell lines. Knockdown of AGR2 caused a decrease in cell viability in PC3 cells, whereas forced expression of AGR2 led to an increased cell proliferation of LNCaP and DU145 cells. Importantly, AGR2 depletion resulted in accumulation of cells at the G(0)/G(1) phase and induction of cellular senescence in all three PCa cell lines as indicated by an increase of flat, enlarged and senescence-associated β-galactosidase (SA-β-Gal) positive cells. Senescent response to AGR2 silencing was also evidenced by elevated γH2AX and fluorescent punctuate formation of tri-methyl-histone H3 in AGR2-depleted cells. Further studies indicated that LNCaP underwent a p21(CIP1)-dependent cellular senescence in response to AGR2 depletion that requires inactivation of ERK signaling, whereas PC-3 was also p21(CIP1) dependent but involved in suppression of PI3K/Akt. Unlike LNCaP and PC-3, senescent response of DU145 was found to be mainly p27(KIP1) dependent that may require upregulation of PTEN and inhibition of PI3K/Akt signaling. Thus, these findings suggest a novel role of AGR2 in regulation of cellular senescence.

Anti-inflammatory effect of Marchantin M contributes to sensitization of prostate cancer cells to docetaxel

As pro-inflammatory cytokines and chemokines contribute to the malignancy of many types of human cancer, we examined the anti-inflammatory effect of bisbibenzyls, a diverse bioactive group of naturally occurring compounds. Marchantin M (Mar M) was identified through a screening process of these compounds as a potent anti-inflammatory agent based on its capacity to inhibit LPS-induced IL6, IL1β and CCL2 expression in HUVECs and PBMCs without affecting cell proliferation. Since Mar M has been found to exhibit anticancer activity, we observed that Mar M treatment also resulted in decreases in the expressions of IL6, IL1β and TNFα in metastatic prostate cancer (PCa) cells. This effect was further confirmed in other cancer cell lines that express high level of pro-inflammatory cytokines. Furthermore, inactivation of NF-κB, a critical transcription factor controlling many pro-inflammatory cytokine expressions, was observed in Mar M-treated PCa cells as evidenced by decreased phosphor-p65 and subsequently phosphor-STAT3. Mar M also suppressed phosphorylation of IKBα, an inhibitor of NF-κB in the cytosol. However, reduced phosphor-p65 by Mar M was slightly increased when knockdown of IKBα, suggesting that Mar M may target upstream molecules of IKBα/NF-κB signaling. Finally, treatment with Mar M resulted in more enhanced-sensitivity of PCa cells to docetaxel-induced apoptosis than that of the IL6 blocking. Our study demonstrates the potential of the anti-inflammatory agent Mar M as an adjuvant to improve the efficacy of traditional anticancer agents such as docetaxel.

Metformin prevents DMH-induced colorectal cancer in diabetic rats by reversing the warburg effect.

Epidemiologic studies have shown that the treatment of diabetics with metformin reduced the risk of cancer‐related mortality. Here, we investigated the chemopreventive effects of metformin on dimethylhydrazine (DMH)‐induced colorectal carcinogenesis in diabetic SD rats following metformin treatment and the effect on Warburg effect involved in this process. Diabetic rat models were induced with high‐fat feeding in combination with a low dose of Streptozotocin (STZ) and then induce colorectal cancer with a low dose of DMH. The formation of colorectal Aberrant crypt foci (ACF) and the incidence, number and size of the tumor were measured. The proliferation indices of colonic tissues were determined through Proliferating cell nuclear antigen (PCNA) immunostaining. Then detect the expression of PK and IDH in colonic tissues using immunohistochemistry and Western blot. The enzyme activities of HK and PDH in colonic tissues were measured. The growth and expression of PK and IDH and activity of HK and PDH in cell lines LoVo and HT‐29 were measured after metformin treatment. The results showed that metformin treatment significantly inhibited the formation of ACF and tumors. The proliferation index of colonic tissues was significantly decreased following metformin treatment. In addition, metformin inhibited cell growth and decreased the imbalance in the expression of the enzymes involved in glycolysis and the TCA cycle. These findings suggested that metformin might produce a synergistic colon cancer‐preventative effect in diabetic patients through the regulation of the enzymes expression involved in glucose metabolism.

Regulation of SOD2 and β-arrestin1 by interleukin-6 contributes to the increase of IGF-1R expression in docetaxel resistant prostate cancer cells

Although several mechanisms behind resistance to docetaxel in castration-refractory prostate cancer (CRPC) have been investigated, molecular determinants of evolved resistance are still not entirely understood. Proteomics-based analysis in this study revealed that SOD2, associated with downregulation of reactive oxygen species (ROS), was significantly up-regulated in docetaxel-resistant (PC3/Doc) cells if compared to sensitive cells, and the expression of redox-regulated genes such as IGF-1R, CXCR4, and BCL2 was increased as well. Forced expression of SOD2 in sensitive cells led to the increase of IGF-1R and association with drug resistance, whereas silencing of SOD2 resulted in the decrease of IGF-1R at the protein level in resistant cells. Further study revealed that SOD2 acted as a negative regulator of β-arrestin1 that is an important adaptor responsible for degradation of IGF-1R via the changes in ROS, as evidenced by observations that an antioxidant agent substantially attenuated β-arrestin1 expression in vitro and in vivo. Finally, we found that blocking of IL6 that was up-regulated in resistant cells resulted in attenuation of SOD2 and STAT3, and simultaneously in increased expression of β-arrestin1. The modulation consequently led to the decreased IGF-1R at both protein and transcription levels. Together, our data provide a novel explanation that high level of IL6 stimulated SOD2 expression that, at least partially, contributed to the low level of ROS that would likely result in a sustained increase in the expression of IGF-1R through abolishment of β-arrestin1 in docetaxel resistant cells.

Retigeric acid B-induced mitophagy by oxidative stress attenuates cell death against prostate cancer cells in vitro

Aim:Retigeric acid B (RAB), a pentacyclic triterpenic acid from Lobaria kurokawae Yoshim, has been found to induce apoptosis in prostate cancer cells. The aim of this study was to investigate the roles of mitochondrial damage-caused mitophagy in RAB-induced prostate cancer cell death in vitro.Methods:Human prostate cancer PC3 and LNCaP cells were tested. Cell viability was analyzed with MTT assay. Cell apoptosis, ROS level and mitochondrial transmembrane potential (mtΔψ) were measured with flow cytometry. Autophagy- and apoptosis-related proteins were studied using Western blotting. GFP-LC3B puncta, mitochondrial swelling and mitophagy were examined morphologically. Quantitative RT-PCR was used to measure LC3B mRNA level, and siRNA was used to knock down LC3BII.Results:In both PC3 and LNCaP cells, RAB (15 μmol/L) increased ROS accumulation and decreased mtΔψ in a time-dependent manner. Furthermore, RAB induced mitochondrial swelling and mitophagy, significantly increased LC3B expression and conversion of LC3BI to LC3BII, and the elimination of mitochondria by LC3BII-containing autophagolysosomes. In addition, RAB suppressed the PI3K/Akt/mTOR pathway activation. Pretreatment of PC3 cells with autophagy inhibitor 3-MA (5 mmol/L) or the lysosomal protease inhibitor CQ (10 μmol/L) significantly increased RAB-induced apoptosis. Similar results were obtained in RAB-treated PC3 cells with LC3B knocked down.Conclusion:RAB induces mitochondrial damage and mitophagy that attenuates RAB-induced prostate cancer cell death. Thus, suppression of mitophagy might be a potential strategy for improving the chemotherapeutic effects of RAB.

Associations of saposin C, Src, and androgen receptor upregulate the expression and function of androgen receptor in human prostate cancer cells

We previously demonstrated that ectopic expression of neurotrophic peptide (NP) derived from saposin C promotes androgen receptor (AR) expression and transactivation in human prostate cancer cells. This prompted us to investigate how NP or saposin C can function in cells. We constructed plasmids expressing saposin C or a chimeric peptide of a viral TAT transduction domain and saposin C (TAT‐saposin C) with His‐tag. Intracellular localization of saposin C and NP was predominantly shown in transfected cells, while TAT‐saposin C was detected around membrane and in cytosol by immunofluorescence staining. Furthermore, induction of the AR expression and activation of the AR transcriptional function were observed in cells transfected with saposin C or TAT‐saposin C, compared to control cells transfected with an empty plasmid. The effects of saposin C and TAT‐saposin C on AR activity were examined in the presence of inhibitors of GPCR, MAPK1/2, and PI3K/Akt. Interestingly, we found that these inhibitors only affect AR activities in cells with TAT‐saposin C expression but not with saposin C expression. Immunostaining images showed that co‐localization of saposin C, Src, and the AR occurred in transfected cells. Physical interactions of saposin C/NP, Src, and the AR were then demonstrated by co‐immunoprecipitation assays. Blockage of Src activity by specific inhibitor led to a decrease in the saposin C‐mediated enhancement of AR transactivity, suggesting that intracellular expression of saposin C caused stimulation of AR expression and activity by associations with Src in LNCaP cells. This effect may not be mediated by GPCR. J. Cell. Biochem. 112: 818–828, 2011.

Oxidative stress induced autophagy in cancer associated fibroblast enhances proliferation and metabolism of colorectal cancer cells

ABSTRACT Tumors are comprised of malignant cancer cells and stromal cells which constitute the tumor microenvironment (TME). Previous studies have shown that cancer associated fibroblast (CAF) in TME is an important promoter of tumor initiation and progression. However, the underlying molecular mechanisms by which CAFs influence the growth of colorectal cancer cells (CRCs) have not been clearly elucidated. In this study, by using a non-contact co-culture system between human colorectal fibroblasts (CCD-18-co) and CRCs (LoVo, SW480, and SW620), we found that fibroblasts existing in tumor microenvironment positively influenced the metabolism of colorectal cancer cells, through its autophagy and oxidative stress pathway which were initially induced by neighboring tumor cells. Therefore, our data provided a novel possibility to develop fibroblasts as a potential target to treat CRC.

Induction of DNA damage and p21-dependent senescence by Riccardin D is a novel mechanism contributing to its growth suppression in prostate cancer cells in vitro and in vivo

PurposeOur previous studies had shown that Riccardin D (RD) exhibited cytotoxic effects by induction of apoptosis and inhibition of angiogenesis and topoisomerase II. Here, we reported that apoptosis is not the sole mechanism by which RD inhibits tumor cell growth because low concentrations of RD caused cellular senescence in prostate cancer (PCa) cells.MethodsLow concentrations of RD were used to treat PCa cells in vitro and in vivo, and senescence-associated β-galactosidase activity, DNA damage response markers, and/or colony-forming ability, cell cycle were analyzed, respectively. We then used siRNA knockdown to identify key factor in RD-triggered cellular senescence.ResultsRD treatment caused growth arrest at G0/G1 phase with features of cellular senescence phenotype such as enlarged and flattened morphology, increased senescence-associated-beta-galactosidase staining cells, and decreased cell proliferation in PCa cells. Induction of cellular senescence by RD occurred through activation of DNA damage response including increases in the phosphor-H2AX, inactivation of Chk1/2, and suppression of repair-related Ku70/86 and phosphor-BRCA1 in PCa cells in vitro and in vivo. Analysis of expression levels of p53, p21CIP1, p16INK4a, p27KIP1, pRb and E2F1 and genetic knockdown of p21CIP1 demonstrated an important role of p21CIP1 in RD-triggered cellular senescence.ConclusionsInvolvement of the DNA damage response and p21CIP1 defines a novel mechanism of RD action and indicates that RD could be further developed as a promising anticancer agent for cancer therapy.