In vitro and in vivo effects and mechanisms of celecoxib-induced growth inhibition of human hepatocellular carcinoma cells

Differential expression of E-prostanoid receptors in human hepatocellular carcinoma

Recent studies have shown that inhibition of cyclooxygenases (e.g. COX-2) exerts antitumorigenic effects on hepatocellular carcinomas (HCCs), which are to a significant extent due to the abrogation of PGE(2) synthesis. PGE(2) acts via differentially regulated prostaglandin receptors (EP(1-4)). Our study was designed to investigate the expression pattern of EP-receptors in HCCs and to evaluate the therapeutic potential of selective EP-receptor antagonists. Using tissue microarrays including a total of 14 control livers, 17 liver cirrhoses, 22 premalignant dysplastic nodules (DNs) and 162 HCCs with different histological grades, the expression of COX-2, mPGES-1 and -2 and EP(1-4)-receptors was analyzed. Western immunoblot analyses were performed to confirm the expression in HCC cell lines. The effects of EP(1-4)-receptor antagonism on cell viability and apoptosis were investigated using MTT-assays and FACS-analyses, respectively. COX-2, mPGES-1 and -2 and EP(1-4)-receptors were expressed in all HCC tissues. COX-2 expression was highest in DNs and declined with loss of HCC-differentiation. With respect to COX-2 expression, a converse expression of EP(1-3) -receptors and mPGES-1 and -2 was found in DNs compared to HCCs. Selectively antagonizing EP(1)- and EP(3)-receptors reduced the viability of HCC cells in a dose-dependent manner, which was associated with apoptosis induction. Our results suggest a differential regulation of EP-receptor subtype expression with dedifferentiation of HCCs in which a converse expression pattern for COX-2 in comparison to EP(1-3)-receptors occurs. Of clinical interest, selectively antagonizing EP(1)- and EP(3)-receptors may provide a novel systemic therapeutic approach to the treatment of HCCs.

Inflammatory response and meningioma tumorigenesis and the effect of cyclooxygenase-2 inhibitors

In this article the authors discuss the rationale and research supporting the hypothesis that meningioma tumorigenesis may, in part, be driven by overexpression of cyclooxygenase-2 (Cox-2) and that treatment with celecoxib, a selective Cox-2 inhibitor, may hold therapeutic promise. Because therapies for recurrent or aggressive meningiomas (atypical or malignant subtypes) such as chemotherapy and radiotherapy generally offer little therapeutic benefit, interest in targeting Cox-2 has grown. This rate-limiting enzyme of prostaglandin synthesis can be inhibited with nonsteroidal antiinflammatory drugs (NSAIDs) such as ibuprofen and celecoxib. Treatment with NSAIDs has been shown to curb the tumorigenic properties of prostaglandins in several cancer models via both Cox-2-dependent and -independent mechanisms. In addition, celecoxib is well tolerated in humans, making its use as a chronic therapy for meningiomas attractive.

Clinical significance of prostaglandin E synthase expression in gastric cancer tissue

Studies have linked microsomal prostaglandin E synthase (mPGES)-1 with gastric cancer. The purpose of this study was to determine mPGES-1, mPGES-2, and cytosolic PGES (cPGES) expression in gastric cancer and to evaluate the correlation between mPGES-1 and mPGES-2 expression and clinicopathological factors and cyclooxygenase-2 expression. PGES protein expression was examined by Western blot in gastric cancer cell lines and in biopsy samples from patients with gastric cancer. mPGES-1, mPGES-2, and cPGES protein localizations were examined immunohistochemically in 129 archival gastric cancer surgical resections. mPGES-1 protein expression was found in gastric cancer biopsies and cancer cell lines with differentiated or undifferentiated adenocarcinoma. There was no mPGES-1 expression in nonneoplastic biopsies. All cell lines and tissue samples expressed mPGES-2 and cPGES. Immunohistochemical analysis showed cancer cells expressed mPGES-1 in 47% of cases. mPGES-2 immunoreactivity was seen both in nonneoplastic glandular epithelium and cancer cells; however, cancer cell immunoreactivity was significantly more pronounced in 29% of cases. cPGES expression was constitutive both in nonneoplastic and neoplastic tissues, with no significant variation among cases. mPGES-1 and mPGES-2 expression correlated with cyclooxygenase-2 expression. mPGES-1 and mPGES-2 expression, and tumor-node-metastasis stage had independent prognostic significance under multivariate analysis in patients with gastric cancer overall and in patients with differentiated cancers. However, only tumor-node-metastasis stage and mPGES-2 expression retained independent prognostic significance in patients with poorly differentiated cancers. mPGES-1 and mPGES-2 correlate with clinicopathological factors and may be valuable prognostic factors in gastric cancer.

Action of Celecoxib on Hepatic Metabolic Changes Induced by the Walker-256 Tumour in Rats

The purpose of the present work was to investigate the influence of celecoxib on some hepatic metabolic parameters affected by the Walker-256 tumour in rats. Celecoxib was administered daily (5-50 mg/kg body weight) beginning at the day in which the tumour cells were inocculated. At day 14, the liver was isolated and perfused in order to measure alanine transformation, glycolysis and arginine transformation. Maximal reduction of tumour growth (75%), accompanied by an almost normal weight gain, was attained with a celecoxib dose of 12.5 mg/kg. Diminution of glucose utilization (glycolysis) and inhibition of gluconeogenesis and ureogenesis from alanine caused by the tumor were totally reversed by celecoxib. Oxygen uptake by the liver was also normalized by the drug. Hepatic arginine transformation, which is normally enhanced in rats bearing the Walker-256 tumour, remained elevated in celecoxib-treated animals. It was concluded that preservation of gluconeogenesis and normalization of hepatic glucose utilization can explain, partly at least, the clinical improvement of cancer patients treated with the drug. The lack of action of celecoxib on arginine hydrolysis might indicate that reduction in polyamine synthesis is not a factor contributing to the diminished tumour growth.

Relative non-steroidal anti-inflammatory drug (NSAID) antiproliferative activity is mediated through p21-induced G1 arrest and E2F inhibition

This study was performed to compare the relative antineoplastic activity of 10 different non-steroidal anti-inflammatory drugs (NSAIDs) in clinical use, and to investigate the underlying mechanisms of this activity in a squamous cell carcinoma of the head and neck model (SCCHN). A standard 5-day MTT assay was used to calculate IC(50) values in UM-SCC-1 cells for 10 NSAIDs, including celecoxib, rofecoxib, sulindac sulfide, sulindac sulfone, indomethacin, ketoprofen, flurbiprofen, naproxen, piroxicam, and aspirin. Celecoxib, a COX-2 specific inhibitor, was by far the most potent NSAID, with an IC(50) of 39.9 +/- 1.1 microM, followed by sulindac sulfide (116.5 +/- 2.34 microM). Celecoxib and sulindac sulfide also induced more activation of caspase-3 than any other NSAID. Cell cycle analysis showed that celecoxib and sulindac sulfide both induced a 3-fold increase in G(1) phase distribution, and this correlated with strong induction of p21(waf1/cip1), inhibition of cyclin D1, and hypophosphorylation of Rb. Celecoxib and sulindac sulfide treatment induced strong downstream inhibition of E2F transactivating activity as determined by a luciferase reporter assay. These data demonstrate the wide range of activity of various NSAID agents, and reveal a mechanism of action through cell cycle inhibition and induction of apoptosis.

Effects and mechanisms of silibinin on human hepatoma cell lines

AIM

To investigate in vitro effects and mechanisms of silibinin on hepatocellular carcinoma (HCC) cell growth.

METHODS

Human HCC cell lines were treated with different doses of silibinin. The effects of silibinin on HCC cell growth and proliferation, apoptosis, cell cycle progression, histone acetylation, and other related signal transductions were systematically examined.

RESULTS

We demonstrated that silibinin significantly reduced the growth of HuH7, HepG2, Hep3B, and PLC/PRF/5 human hepatoma cells. Silibinin-reduced HuH7 cell growth was associated with significantly up-regulated p21/CDK4 and p27/CDK4 complexes, down-regulated Rb-phosphorylation and E2F1/DP1 complex. Silibinin promoted apoptosis of HuH7 cells that was associated with down-regulated survivin and up-regulated activated caspase-3 and -9. Silibinin's anti-angiogenic effects were indicated by down-regulated metalloproteinase-2 (MMP2) and CD34. We found that silibinin-reduced growth of HuH7 cells was associated with increased activity of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and decreased p-Akt production, indicating the role of PTEN/PI(3)K/Akt pathway in silibinin-mediated anti-HCC effects. We also demonstrated that silibinin increased acetylation of histone H3 and H4 (AC-H3 and AC-H4), indicating a possible role of altered histone acetylation in silibinin-reduced HCC cell proliferation.

CONCLUSION

Our results defined silibinin's in vitro anti-HCC effects and possible mechanisms, and provided a rationale to further test silibinin for HCC chemoprevention.

P-glycoprotein mediates celecoxib-induced apoptosis in multiple drug-resistant cell lines

In several neoplastic diseases, including hepatocellular carcinoma, the expression of P-glycoprotein and cyclooxygenase-2 (COX-2) are often increased and involved in drug resistance and poor prognosis. P-glycoprotein, in addition to drug resistance, blocks cytochrome c release, preventing apoptosis in tumor cells. Because COX-2 induces P-glycoprotein expression, we evaluated the effect of celecoxib, a specific inhibitor of COX-2 activity, on P-glycoprotein-mediated resistance to apoptosis in cell lines expressing multidrug resistant (MDR) phenotype. Experiments were done using MDR-positive and parental cell lines at basal conditions and after exposure to 10 or 50 micromol/L celecoxib. We found that 10 micromol/L celecoxib reduced P-glycoprotein, Bcl-x(L), and Bcl-2 expression, and induced translocation of Bax from cytosol to mitochondria and cytochrome c release into cytosol in MDR-positive hepatocellular carcinoma cells. This causes the activation of caspase-3 and increases the number of cells going into apoptosis. No effect was shown on parental drug-sensitive or on MDR-positive hepatocellular carcinoma cells after transfection with MDR1 small interfering RNA. Interestingly, although inhibiting COX-2 activity, 50 micromol/L celecoxib weakly increased the expression of COX-2 and P-glycoprotein and did not alter Bcl-x(L) and Bcl-2 expression. In conclusion, these results show that relatively low concentrations of celecoxib induce cell apoptosis in MDR cell lines. This effect is mediated by P-glycoprotein and suggests that the efficacy of celecoxib in the treatment of different types of cancer may depend on celecoxib concentration and P-glycoprotein expression.

Celecoxib induces apoptosis by inhibiting the expression of survivin in HeLa cells

The effect of celecoxib, a cyclooxygenase-2 selective inhibitor, on a human cervical cancer cell line, HeLa cells, was examined. We found that celecoxib increased DNA ladder formation and the activity of caspase-3, indicating that celecoxib induced apoptosis in HeLa cells. Celecoxib suppressed the expression of an anti-apoptotic protein, survivin, in both protein and mRNA levels. The overexpression of survivin overrode caspase-3 activation induced by celecoxib. Subsequently, we performed luciferase reporter assay with the reporter vector containing human survivin promoter region and electrophoretic mobility shift assay and found that the -75 to -66 bp region relative to the initiating codon played an important role in celecoxib action to suppress survivin promoter activity. Our findings might provide a new insight into the anti-cancer effects of celecoxib.

Celecoxib inhibits meningioma tumor growth in a mouse xenograft model

BACKGROUND

Treatments for recurrent meningiomas are limited. We previously demonstrated universal expression of COX-2 in meningiomas and dose-dependent growth inhibition in vitro with celecoxib, a COX-2 inhibitor. We therefore tested the effects of celecoxib on meningioma growth in a mouse xenograft model.

METHODS

Meningioma cell lines (IOMM-Lee, CH157-MN, WHO grade I primary cultured tumor) were transplanted into flanks of nude mice fed mouse chow with celecoxib at varying concentrations (0, 500, 1000, 1500 ppm) ad libitum. Tumors were measured biweekly and processed for MIB-1, Factor VIII, COX-2, and VEGF, and assayed with transferase-mediated dUTP-biotin nick-end labeling (TUNEL).

RESULTS

Celecoxib reduced growth of mean tumor volume by 66% (P < .05), 25% (P > .05), and 65% (P < .05) compared with untreated controls in IOMM-Lee, CH157-MN, and benign tumors, respectively. IOMM-Lee tumors removed from celecoxib treatment regained a growth rate similar to the control. Blood vessel density decreased and apoptotic cells increased in treated flank tumors. Diminished COX-2 expression and VEGF were observed in treated IOMM-Lee tumors. Mean plasma celecoxib levels were 845, 1540, and 2869 ng/mL, for low-, medium-, and high-dose celecoxib, respectively.

CONCLUSIONS

Celecoxib inhibits meningioma growth in vivo at plasma levels achievable in humans. Celecoxib-treated tumors were less vascular with increased apoptosis. IOMM-Lee tumors treated with celecoxib showed decreased COX-2 and VEGF expression. COX-2 inhibitors may have a role in the treatment of recurrent meningiomas.

Novel concepts in hepatocellular carcinoma: from molecular research to clinical practice

Hepatocellular carcinoma (HCC) is one of the most common malignancies in the world, burdened by a constantly increasing frequency. Therapy is currently restricted to invasive techniques but prognosis and survival are still unsatisfactory, mainly because of HCC recurrence and metastasis diffusion. This review will focus on the problem of tumor recurrence and/or metastasis, pointing out the role of the tissue microenvironment in affecting HCC behavior; new experimental findings will also be discussed in the light of their implications in medical care. Finally, new therapeutic approaches will be considered, paying particular attention to the tissue microenvironment as a potential target. In conclusion, this review will attempt to stimulate debate on translational research into HCC biology, in the field of clinical applications.

OSU-03012 promotes caspase-independent but PERK-, cathepsin B-, BID-, and AIF-dependent killing of transformed cells

We determined one mechanism by which the putative phosphoinositide-dependent kinase (PDK)-1 inhibitor 2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl}acetamide (OSU-03012) killed primary human glioma and other transformed cells. OSU-03012 caused a dose-dependent induction of cell death that was not altered by p53 mutation, expression of ERBB1 vIII, or loss of phosphatase and tensin homolog deleted on chromosome 10 function. OSU-03012 promoted cell killing to a greater extent in glioma cells than in nontransformed astrocytes. OSU-03012 and ionizing radiation caused an additive, caspase-independent elevation in cell killing in 96-h viability assays and true radiosensitization in colony formation assays. In a cell type-specific manner, combined exposure to OSU-03012 with a mitogen-activated protein kinase kinase 1/2 inhibitor, phosphoinositide 3-kinase/AKT inhibitors, or parallel molecular interventions resulted in a greater than additive induction of cell killing that was independent of AKT activity and caspase function. OSU-03012 lethality as a single agent or when combined with signaling modulators was not modified in cells lacking expression of BIM or of BAX/BAK. OSU-03012 promoted the release of cathepsin B from the lysosomal compartment and release of AIF from mitochondria. Loss of BH3-interacting domain (BID) function, overexpression of BCL(XL), and inhibition of cathepsin B function suppressed cell killing and apoptosis-inducing factor (AIF) release from mitochondria. In protein kinase R-like endoplasmic reticulum kinase-/- cells, the lethality of OSU-03012 was attenuated which correlated with reduced cleavage of BID and with suppression of cathepsin B and AIF release into the cytosol. Our data demonstrate that OSU-03012 promotes glioma cell killing that is dependent on endoplasmic reticulum stress, lysosomal dysfunction, and BID-dependent release of AIF from mitochondria, and whose lethality is enhanced by irradiation or by inhibition of protective signaling pathways.