CD146, a novel target of CD44-signaling, suppresses breast tumor cell invasion.

BACKGROUND: We have previously validated three novel CD44-downstream positively regulated transcriptional targets, including Cortactin, Survivin and TGF-ß2, and further characterized the players underlying their separate signaling pathways. In the present study, we identified CD146 as a potential novel target, negatively regulated by CD44. While the exact function of CD146 in breast cancer (BC) is not completely understood, substantial evidence from our work and others support the hypothesis that CD146 is a suppressor of breast tumor progression. METHODS: Therefore, using molecular and pharmacological approaches both in vitro and in breast tissues of human samples, the present study validated CD146 as a novel target of CD44-signaling suppressed during BC progression. RESULTS: Our results revealed that CD44 activation could cause a substantial decrease of CD146 expression with an equally notable converse effect upon CD44-siRNA inhibition. More interestingly, activation of CD44 decreased cellular CD146 and increased soluble CD146 through CD44-dependent activation of MMP. CONCLUSION: Here, we provide a possible mechanism by which CD146 suppresses BC progression as a target of CD44-downstream signaling, regulating neovascularization and cancer cell motility.

TLE1 promotes EMT in A549 lung cancer cells through suppression of E-cadherin.

The Groucho transcriptional corepressor TLE1 protein has recently been shown to be a putative lung specific oncogene, but its underlying oncogenic activity in lung cancer has not been fully elucidated. In this report, we investigated whether TLE1 regulates lung cancer aggressiveness using the human lung adenocarcinoma cell line A549 as a model system. Through a combination of genetic approaches, we found that TLE1 potentiates epithelial-to-mesenchymal transition (EMT) in A549 cells in part through suppression of the tumor suppressor gene E-cadherin. Exogenous expression of TLE1 in A549 cells resulted in heightened EMT phenotypes (enhanced fibroblastoid morphology and increased cell migratory potential) and in molecular alterations characteristic of EMT (downregulation of the epithelial marker E-cadherin and upregulation of the mesenchymal marker Vimentin). Conversely, downregulation of endogenous TLE1 expression in these cells resulted in reversal of basal EMT characterized by a cuboidal-like epithelial cell phenotype, reduced cell motility, and upregulated E-cadherin expression. Mechanistic studies showed that TLE1 suppresses E-cadherin expression at the transcriptional level in part by recruiting histone deacetylase (HDAC) activity to the E-cadherin promoter. Consistently, the HDAC inhibitor TSA partially reversed the TLE1-induced E-cadherin downregulation and cell migration, suggesting a role for HDACs in TLE1-mediated transcriptional repression of E-cadherin and EMT function. These findings uncover a novel role of TLE1 in regulating EMT in A549 cells through its repressive effect on E-cadherin and provide a mechanism for TLE1 oncogenic activity in lung cancer.

Chemoprevention of rat mammary carcinogenesis by spirulina.

Spirulina (SP) (Arthrospira platensis; previously Spirulina platensis) is a filamentous blue-green microalga (cyanobacterium) with potent dietary phytoantioxidant and anticancerous properties. We investigated the chemopreventive effect of SP against 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat breast carcinogenesis, and further studied its underlying mechanisms of action in vitro. Remarkably, SP cleared DMBA-induced rat mammary tumors, which was clearly confirmed by morphological and histological methods. SP supplementation reduced the incidence of breast tumors from 87% to 13%. At the molecular level, immunohistochemical analysis revealed that SP supplementation reduced expression of both Ki-67 and estrogen α. More interestingly, molecular analysis in the in vitro experiments indicated that SP treatment inhibited cell proliferation by 24 hours, which was accompanied by increased p53 expression, followed by increased expression of its downstream target gene, Cdkn1a (alias p21 or p21(Waf1/Cip1)). In addition, SP increased Bax and decreased Bcl-2 expression, indicating induction of apoptosis by 48 hours after SP treatment. To our knowledge, this is the first report of in vivo chemopreventive effect of SP against DMBA-induced breast carcinogenesis in rat, supporting its potential use in chemoprevention of cancer.

Survivin is a novel target of CD44-promoted breast tumor invasion.

The hyaluronan (HA) receptor CD44 plays an essential role in cell-cell or cell-extracellular matrix communications and is a bioactive signal transmitter. Although a number of studies have described the function of CD44 in breast cancer (BC) metastasis, the underlying mechanisms have yet to be determined. By using a validated tetracycline-off-regulated CD44 expression system in the MCF-7 cell line combined with microarray analysis, we identified survivin (SVV) as a potential downstream transcriptional target of CD44. To test the hypothesis that SVV underpins CD44-promoted BC cell invasion, we combined molecular and pharmacologic approaches and showed that CD44 induction increased SVV expression levels, which in turn promotes BC cell invasion. Further, clinical analysis of breast tissue samples showed that SVV expression patterns paralleled those of the standard form of CD44 during breast tumor progression. More interestingly, we identified the PI3K/E2F1 pathway as a potential molecular link between HA/CD44 activation and SVV transcription. In addition to identifying SVV as a target for HA/CD44 signaling, this investigation provides a better understanding of the molecular mechanisms that underpin the novel function of SVV in breast cancer metastasis.

Effects of fried potato chip supplementation on mouse pregnancy and fetal development.

OBJECTIVE: Acrylamide (ACR), a proven rodent carcinogen, is present at significantly high quantities in commonly consumed foods such as potato chips, raising a health concern worldwide. METHODS: The effects of ACR and fried potato chips (FPC) on pregnant mice and their offspring before and after birth were investigated and compared. RESULTS: In the pregnant mice, similar histologic abnormalities were found in various tissues for ACR intoxication and FPC supplementation. Drastic alterations were mainly seen in the liver, kidney, heart muscle, and epiphyseal cartilage of experimental dams. ACR and FPC increased the rate of abortion and neonatal mortality and decreased the total number, body weight, size, and crown-rump length of the offspring before and after birth. Interestingly, however, higher rates of congenital malformations were observed in the FPC-treated group. Although ossification of axial and appendicular bones was markedly retarded during fetal development, some ossified bones were missing in newly born offspring of treated groups. Furthermore, the incidence of missing ossification centers was higher in the FPC-treated than in the ACR-treated neonates. CONCLUSION: These results suggest that FPC can cause hazardous health effects and warrant a systematic study on the health effects of consumption of FPC and French fries in the general population.

Histopathological effects of cisplatin, doxorubicin and 5-flurouracil (5-FU) on the liver of male albino rats.

Cisplatin, doxorubicin and fluorouracil (5-FU), drugs belonging to different chemical classes, have been extensively used for chemotherapy of various cancers. Despite extensive investigations into their hepatotoxicity, there is very limited information on their effects on the structure and ultra-structure of liver cells in vivo. Here, we demonstrate for the first time, the effects of these three anticancer drugs on rat liver toxicity using both light and electron microscopy. Light microscopic observations revealed that higher doses of cisplatin and doxorubicin caused massive hepatotoxicity compared to 5-FU treatment, including dissolution of hepatic cords, focal inflammation and necrotic tissues. Interestingly, low doses also exhibited abnormal changes, including periportal fibrosis, degeneration of hepatic cords and increased apoptosis. These changes were confirmed at ultrastructural level, including vesiculated rough endoplasmic reticulum and atrophied mitochondria with ill-differentiated cisternae, dense collection of macrophages and lymphocytes as well as fibrocytes with collagenous fibrils manifesting early sign of fibrosis, especially in response to cisplatin and doxorubicin -treatment. Our results provide in vivo evidence, at ultrastructural level, of direct hepatotoxicity caused by cisplatin, doxorubicin and 5-FU at both light and electron microscopi. These results can guide the design of appropriate treatment regimen to reduce the hepatotoxic effects of these anticancer drugs.

Chemoprevention of rat liver toxicity and carcinogenesis by Spirulina.

Spirulina platensis (SP) is a filamentous cyanobacterium microalgae with potent dietary phyto-antioxidant, anti-inflammatory and anti-cancerous properties. The present study aimed to investigate the chemopreventive effect of SP against rat liver toxicity and carcinogenesis induced by dibutyl nitrosamine (DBN) precursors, and further characterized its underlying mechanisms of action in HepG2 cell line. Investigation by light and electron microscopy showed that DBN treatment induced severe liver injury and histopathological abnormalities, which were prevented by SP supplementation. The incidence of liver tumors was significantly reduced from 80 to 20% by SP. Immunohistochemical results indicated that both PCNA and p53 were highly expressed in the liver of DBN-treated rats, but were significantly reduced by SP supplementation. Molecular analysis indicated that SP treatment inhibited cell proliferation, which was accompanied by increased p21 and decreased Rb expression levels at 48hrs post-treatment. In addition, SP increased Bax and decreased Bcl-2 expression, indicating induction of apoptosis by 48hrs. This is the first report of the in vivo chemopreventive effect of SP against DBN-induced rat liver cytotoxicity and carcinogenesis, suggesting its potential use in chemoprevention of cancer.

Characterization of coordinated immediate responses by p16INK4A and p53 pathways in UVB-irradiated human skin cells.

While the precise mechanisms of melanoma development are unknown, recent in vivo studies have revealed that the p16(Ink4a)/Rb pathway is disrupted in melanomagenesis. Here, we characterize the role of p16/Rb in coordinating the early events in UVB-irradiated skin. Foreskins and melanoma cell cultures were irradiated with low and high acute UVB doses and examined for cell-cycle- and apoptosis-associated genes. In melanoma cells, low UVB dose upregulated p16, p53, and p21 expression levels in Malme-3M, and high UVB dose accentuated the expression of p53 and p21(Cip1/Waf1), in particular; however, in SkMel-28 cells only p16 expression was upregulated in response to UV irradiation. In HaCaT cells, high UVB dose caused dramatic increase in p53 expression followed by upregulation of p21(Cip1/Waf1) and Bax, and downregulation of Bcl-2 leading to apoptosis. In HaCaT cells, reinstatement of p16 pathway restored cell-cycle arrest in response to low dose. Foreskin organ culture experiments confirmed our in vitro cell results. These data indicate that the p53 and p16 pathways respond independently to UVB insult. The p16 pathway is favored at low doses and results in cell-cycle arrest; the p53 pathway is more responsive to higher doses and induces apoptosis depending on p53 mutation status.

Synergistic action of dietary phyto-antioxidants on survival and proliferation of ovarian cancer cells.

OBJECTIVES: A number of herbal dietary antioxidant supplements containing Indole-3 Carbinol (I3C) and Resveratrol (RE) have been established as anti-proliferative agents in cancer. These compounds have both similar as well as unique molecular targeting profiles. The purpose of this study is to analyze their mechanism of action when used individually and in combination in ovarian cancer. METHODS: SK-OV-3 ovarian cancer cells were treated with various doses of I3C, RE or I3C+RE. AlamarBlue dye assay was used to examine cell growth and proliferation. Cell cycle and apoptosis were analyzed by flow cytometry. Western blot was performed to determine the expression of the genes associated with cell cycle and apoptosis. CA-125, a functional marker of ovarian cancer, and nitric oxide, were analyzed by ELISA. RESULTS: I3C or RE inhibited cell proliferation, and caused cell contraction and apoptosis. Analysis of apoptosis-associated genes revealed an inhibition of Retinoblastoma protein (Rb) and Survivin (SVV) gene expression. This was accompanied by elevation of p21, a tumor suppressor. Cell cycle was inhibited at both G1 and G2/M by individual treatments, and accentuated by a combination. AlamarBlue assay revealed a clear synergistic action of I3C+RE. CA125 was inhibited by either I3C or RE treatments. In contrast, basal nitric oxide production was inhibited by I3C and I3C+RE but not RE alone. CONCLUSIONS: This is the first evidence demonstrating the effects of I3C on ovarian cancer cells and its synergism with RE. Based on this model, our data indicate that combinations of compounds with different targeting properties will be more effective in chemoprevention and/or chemotherapy of ovarian and possibly other cancers.

Differential effects of leptin on the invasive potential of androgen-dependent and -independent prostate carcinoma cells.

Obesity has been linked with an increased risk of prostate cancer. The formation of toxic free oxygen radicals has been implicated in obesity mediated disease processes. Leptin is one of the major cytokines produced by adipocytes and controls body weight homeostasis through food intake and energy expenditure. The rationale of the study was to determine the impact of leptin on the metastatic potential of androgen-sensitive (LNCaP) cells as well as androgen-insensitive (PC-3 and DU-145) cells. At a concentration of 200 nm, LNCaP cells showed a significant increase (20% above control; P < .0001) in cellular proliferation without any effect on androgen-insensitive cells. Furthermore, exposure to leptin caused a significant (P < .01 to P < .0001) dose-dependent decrease in migration and invasion of PC3 and Du-145 prostate carcinoma cell lines. At the molecular level, exposure of androgen-independent prostate cancer cells to leptin stimulates the phosphorylation of MAPK at early time point as well as the transcription factor STAT3, suggesting the activation of the intracellular signaling cascade upon leptin binding to its cognate receptor. Taken together, these results suggest that leptin mediates the invasive potential of prostate carcinoma cells, and that this effect is dependent on their androgen sensitivity.

In vivo evidence for the role of CD44s in promoting breast cancer metastasis to the liver.

The hyaluronan receptor CD44 plays an important role in facilitating invasion and metastasis of a variety of tumors, including breast carcinomas. CD44 functions as a bioactive signaling transmitter. Although a number of studies have implicated CD44 in breast tumor invasion, the evidence is still circumstantial. We have developed a tetracycline-regulated CD44s (standard form) system in the weakly metastatic breast cancer cell MCF7, which exhibits low endogenous expression of CD44 and generated a new cell line, MCF7F-B5. Induction of CD44s alone affected the growth characteristics of MCF7F-B5 cells by increasing their abilities to proliferate, migrate, and invade in vitro. In addition, we have identified and validated cortactin as a novel transcriptional target of hyaluronan/CD44s signaling in underpinning breast tumor invasion. To test these observations in vivo, we developed a doxycycline (DOX)-regulated CD44s breast cancer xenograft model. Induction of CD44s did not affect the growth rate or local invasion of the primary tumor. However, although no mice from the +DOX group developed metastasis, 8 of 11 mice from the -DOX group developed secondary tumors to the liver only. Interestingly, metastatic breast tumors expressed high levels of CD44. This study provides in vivo evidence for the role of the standard form of CD44 in promoting breast tumor invasion and metastasis to the liver.

Elevation of serum riboflavin carrier protein in hepatocellular carcinoma.

Early detection of hepatocellular cancer (HCC), makes it surgically resectable with a potential for cure. The test most commonly used to detect HCC is the measurement of serum alpha-fetoprotein (AFP) levels. However, the AFP test is negative in HCC detection in more than 30% of the cases. Riboflavin carrier protein (RCP) is a growth and developmental protein, synthesized and secreted by the liver and hence was of interest to measure its levels in HCC. A prospective double blind evaluation of RCP levels in serum from 93 subjects was undertaken. These included 22 proven cases of HCC, 25 normal controls, 20 cases of alcoholic hepatitis, 20 cirrhotics, and 6 cases of primary biliary cirrhosis (PBC). RCP was measured by a sensitive and specific radioimmunoassay (RIA). RCP was immunohistochemically localized in paraffin sections of liver specimens using standard methods. Mean serum RCP levels in HCC were 21.75+/-14.66ng/ml and were significantly higher (p<0.0001) than those in normal controls (0.73+/-0.25ng/ml), alcoholic hepatitis (1.92+/-0.82ng/ml), PBC (2.16+/-0.74ng/ml), or cirrhosis (5.02+/-1.52ng/ml). Serum RCP levels were elevated in all 22 HCC cases. In contrast serum AFP levels were elevated in 11 of 22 HCC cases. Immunohistochemical analyses revealed positive staining for RCP in liver tumors. We have previously demonstrated elevation of serum RCP levels in breast adenocarcinoma. Our results suggest that serum RCP levels are significantly elevated in HCC also and could potentially serve as a marker for HCC detection under conditions where breast cancer is ruled out. In combination with AFP, serum RCP levels have the potential of serving as a panel of markers for better detection of HCC.