Celecoxib leads to G2/M arrest by induction of p21 and down-regulation of cyclin B1 expression in a p53-independent manner

Discovery of ganoderic acid A (GAA) PROTACs as MDM2 protein degraders for the treatment of breast cancer

Breast cancer is one of the most common female malignant tumors, with triple-negative breast cancer (TNBC) being the most specific, highly invasive, metastatic and associated with a poor prognosis. Our previous study showed that the natural product ganoderic acid A (GAA) has a certain affinity for MDM2. In this study, two series of novel GAA PROTACs C1-C10 and V1-V10 were designed and synthesized for the treatment of breast cancer. The antitumor activity of these compounds was evaluated against four human tumor cell lines (MCF-7, MDA-MB-231, SJSA-1, and HepG2). Among them, V9 and V10 showed stronger anti-proliferative effects against breast cancer cells, and V10 showed the best selectivity in MDA-MB-231 cells (TNBC), which was 5-fold higher than that of the lead compound GAA. Preliminary structure-activity analysis revealed that V-series GAA PROTACs had better effects than C-series, and the introduction of 2O-4O PEG linkers could significantly improve the antitumor activity. Molecular docking, surface plasmon resonance (SPR), cellular thermal shift assay (CETSA), and Western blot researches showed that both V9 and V10 could bind with MDM2, and degrade the protein through the ubiquitin-proteasome system. Molecular dynamics simulation (MD) revealed that V10 is a bifunctional molecule that can bind to von Hippel-Lindau (VHL) at one end and target MDM2 at the other. In addition, V10 promoted the upregulation of p21 in p53-mutant MDA-MB-231 cells, and induced apoptosis via down-regulation of the bcl-2/bax ratio and the expression of cyclin B1. Finally, in vivo experiments showed that, V10 also exhibited good tumor inhibitory activity in xenografted TNBC zebrafish models, with an inhibition rate of 27.2% at 50 μg/mL. In conclusion, our results suggested that V10 has anti-tumor effects on p53-mutant breast cancer in vitro and in vivo, and may be used as a novel lead compound for the future development of TNBC.

Acacetin induces sustained ERK1/2 activation and RIP1-dependent necroptotic death in breast cancer cells

Acacetin (AC), a naturally occurring flavonoid has shown anticancer potential. Herein, we studied the mechanisms of cell death and growth inhibition by AC in breast carcinoma T-47D and MDA-MB-231 cells. AC (10-40 μM) significantly decreased the levels of G2/M phase cyclins and CDKs, simultaneously increasing the expression of CDK inhibitors including Cip1/p21. A concentration-dependent increase in cell death was noted in both breast cancer cell lines with no such considerable effects on MCF-10A non-tumorigenic breast cells. The cell death-inducing potential of AC was further confirmed using confocal microscopy and flow cytometry analysis. AC resulted in mitochondrial superoxide generation, DNA damage, and ROS generation. N-acetyl cysteine (NAC) pre-treatment inhibited ROS generation and partially reversed ERK1/2 activation as well as cell death by AC. Further, AC enhanced the expression of RIP1 and RIP3, which mediate necroptosis. RIP1-specific inhibitor Necrostatin-1 (NS-1) reversed the AC-induced DNA damage and cell death. Collectively, these findings, for the first time, suggested that AC exerts its antitumor potential through ROS induction and RIP1-dependent necroptosis in breast carcinoma cells.

Falnidamol and cisplatin combinational treatment inhibits non-small cell lung cancer (NSCLC) by targeting DUSP26-mediated signal pathways

Non-small-cell lung cancer (NSCLC) is one of the most commonly diagnosed cancers worldwide with limited effective therapies. Cisplatin (DDP), as the first-line treatment, is always served as a mainstay of chemotherapeutic agents in combination with other drugs for NSCLC treatment. Nevertheless, DDP-based therapy is limited due to the frequent development of chemoresistance and adverse effects. Herein, it is necessary to find a more effective therapeutic approach with less toxicity. Falnidamol (FLD) is a pyrimido-pyrimidine compound and exerts anti-cancer activity. In the present study, we found that FLD could strongly promote the cytotoxicity of DDP and markedly reduce the IC₅₀ values to restrain the proliferation of NSCLC cells. Furthermore, combination of FLD and DDP remarkably induced G2/M cell cycle arrest, DNA damage and mitochondrial apoptosis, which was largely through the induction of reactive oxygen species (ROS). Additionally, FLD/DDP in combination greatly triggered ferroptosis, along with free iron accumulation and enhanced lipid peroxidation. Epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) phosphorylation were also considerably restrained in NSCLC cells co-treated with FLD/DDP. Mechanistically, the combinative treatment significantly reduced DUSP26 expression in NSCLC cells. More studies showed that DUSP26 was strongly up-regulated in human NSCLC samples compared with the paired normal tissues, and high DUSP26 predicted poor overall survival rate among patients. Importantly, we found that DUSP26 suppression intensively reduced the proliferation, EMT process and pEGFR expression in NSCLC cells, whereas facilitated ROS production, DNA damage and cell death; however, opposite phenotype was observed in NSCLC cells over-expressing DUSP26. More importantly, DUSP26 over-expression completely abolished the anti-cancer function of FLD/DDP in NSCLC cells. Animal studies finally confirmed that FLD/DDP in combination efficiently reduced tumor growth and lung metastasis in mice with ameliorated side effects. In conclusion, all these data illustrated that FLD and DDP combinational treatment effectively restrained NSCLC progression, and thus can be served as a promising therapeutic strategy.

High ROS Production by Celecoxib and Enhanced Sensitivity for Death Ligand-Induced Apoptosis in Cutaneous SCC Cell Lines

Incidence of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis has increased worldwide, and non-steroidal anti-inflammatory drugs as celecoxib are considered for treatment. We show here strong anti-proliferative effects of celecoxib in four cSCC cell lines, while apoptosis and cell viability largely remained unaffected. Impeded apoptosis was overcome in combinations with agonistic CD95 antibody or TNF-related apoptosis-inducing ligand (TRAIL), resulting in up to 60% apoptosis and almost complete loss of cell viability. Proapoptotic caspase cascades were activated, and apoptosis was suppressed by caspase inhibition. TRAIL receptor (DR5) and proapoptotic Bcl-2 proteins (Puma and Bad) were upregulated, while anti-apoptotic factors (survivin, XIAP, cFLIP, Mcl-1, and Bcl-w) were downregulated. Strongly elevated levels of reactive oxygen species (ROS) turned out as particularly characteristic for celecoxib, appearing already after 2 h. ROS production alone was not sufficient for apoptosis induction but may play a critical role in sensitizing cancer cells for apoptosis and therapy. Thus, the full therapeutic potential of celecoxib may be better used in combinations with death ligands. Furthermore, the immune response against cSCC/AK may be improved by celecoxib, and combinations with checkpoint inhibitors, recently approved for the treatment of cSCC, may be considered.

CAVIN2 is frequently silenced by CpG methylation and sensitizes lung cancer cells to paclitaxel and 5-FU

Aim: To explore the biological functions and clinical significance of CAVIN2 in lung cancer. Materials & methods: Methylation-specific PCR was used to measure promoter methylation of CAVIN2. The function of CAVIN2 was tested by Cell Counting Kit-8, colony formation, Transwell, flow cytometric analysis, acridine orange/ethidium bromide, chemosensitivity assay and xenograft assay. Results: CAVIN2 is significantly downregulated by promoter methylation in lung cancer. CAVIN2 overexpression inhibits lung cancer cell migration and invasion. Furthermore, ectopic expression of CAVIN2 inhibits cell proliferation in vivo and in vitro by inducing G2/M cell cycle arrest, which sensitizes the chemosensitivity of lung cancer cells to paclitaxel and 5-fluorouracil, but not cisplatin. Conclusion: CAVIN2 is a tumor suppressor in non-small-cell lung cancer and can sensitize lung cancer cells to paclitaxel and 5-fluorouracil.

Inosine 5'-diphosphate, a molecular decoy rescues Nucleoside diphosphate kinase from c-MYC G-Quadruplex unfolding

BACKGROUND

The transcription-inhibitory G-Quadruplex(Pu27-GQ) at c-MYC promoter is challenging to target due to structural heterogeneity. Nucleoside diphosphate kinase (NM23-H2) specifically binds and unfolds Pu27-GQ to increase c-MYC transcription. Here, we used Inosine 5'-diphosphate (IDP) to disrupt NM23-H2-Pu27-GQ interactions and arrest c-MYC transcription without compromising NM23-H2-mediated kinase properties.

METHODS

Site-directed mutagenesis,³¹P-NMR and STD-NMR studies delineate the epitope of NM23-H2-IDP complex and characterize specific amino acids in NM23-H2 involved in Pu27-GQ and IDP interactions. Immunoprecipitations and phosphohistidine-immunoblots reveal how IDP blocks NM23-H2-Pu27 association to downregulate c-MYC transcription in MDAMB-231 cells exempting NM23-H2-mediated kinase properties.

RESULTS

NMR studies show that IDP binds to the Guanosine diphosphate-binding pocket of NM23-H2 (K_D = 5.0 ± 0.276 μM). Arg88-driven hydrogen bonds to the terminal phosphate of IDP restricts P-O-P bond-rotation increasing its pKa (∆pKa = 0.85 ± 0.0025).9-inosinyl moiety of IDP is stacked over Phe60 phenyl ring driving trans-conformation of inosine and axial geometry of pyrophosphates. Chromatin immunoprecipitations revealed that these interactions rescue NM23-H2-driven Pu27-GQ unfolding, which triggers Nucleolin recruitment and lowers Sp1 occupancy at c-MYC promoter stabilizing Pu27-GQ. This silences c-MYC transcription that reduces c-MYC-Sp1 association amplifying Sp1 recruitment across P21 promoter stimulating P21 transcription and G₂/M arrest.

CONCLUSIONS

IDP synergizes the effects of Pu27-GQ-interacting compounds to abrogate c-MYC transcription and induce apoptosis in MDAMB-231 cells by disrupting NM23-H2-Pu27-GQ interactions without affecting NM23-H2-mediated kinase properties.

GENERAL SIGNIFICANCE

Our study provides a pragmatic approach for developing NM23-H2-targeting regulators to rescue NM23-H2 binding at structurally ambiguous Pu27-GQ that synergizes the anti-tumorigenic effects of GQ-based therapeutics with minimized off-target effects.

Recombinant Dual-target MDM2/MDMX Inhibitor Reverses Doxorubicin Resistance through Activation of the TAB1/TAK1/p38 MAPK Pathway in Wild-type p53 Multidrug-resistant Breast Cancer Cells

Chemotherapy resistance represents a major obstacle for the treatment of patients with breast cancer (BC) and greatly restricts the therapeutic effect of the first-line chemotherapeutic agent doxorubicin (DOX). The present study aimed to investigate the feasibility of the recombinant dual-target murine double minute 2 (MDM2) and murine double minute X (MDMX) inhibitor in reversing the DOX resistance of BC. Both DOX-resistant human breast carcinoma cell lines exhibited a multidrug resistance (MDR) phenotype. The ability of the dual-target MDM2/MDMX inhibitor in reversing doxorubicin resistance was subsequently verified, (9.15 and 13.92 - fold reversal indexes) respectively. We observed that the MDM2/MDMX inhibitor in combination with DOX could suppress proliferation, promote cell cycle arrest and induce apoptosis. In addition, it was capable of reducing rhodamine123 efflux in DOX-resistance BC cell lines and further played a key role in BC nude mice model. The groups that were treated with the combination of the drugs had decreased P-glycoprotein/multidrug resistance-associated protein/cdc 2/Bcl-2 expression and increased CyclinB1/Bax expression. These effects were caused due to activation of the transforming growth factor β-activated kinase 1 (TAK1)-binding protein 1 (TAB1)/TAK1/p38 mitogen-activated protein kinase (MAPK) signaling pathway, as shown by small interfering RNA (siRNA) silencing and immumohistochemical staining of BC tissue sections. Furthermore, high MDM2/MDMX expression was positively associated with weak TAB1 expression in BC patients. Therefore, the recombinant dual-target MDM2/MDMX inhibitor could reverse doxorubicin resistance via the activation of the TAB1/TAK1/p38 MAPK pathway in wild-type p53 multidrug-resistant BC.

MicroRNA-582-3p negatively regulates cell proliferation and cell cycle progression in acute myeloid leukemia by targeting cyclin B2

BACKGROUND

MicroRNAs (miRNAs) function as post-transcriptional gene expression regulators. Some miRNAs, including the recently discovered miR-582-3p, have been implicated in leukemogenesis. This study aimed to reveal the biological function of miR-582-3p in acute myeloid leukemia (AML), which is one of the most frequently diagnosed hematological malignancies.

METHODS

The expression of miR-582-3p was determined using quantitative real-time PCR in blood samples from leukemia patients and in cell lines. Cell proliferation and cell cycle distribution were analyzed using the CCK-8, colony formation and flow cytometry assays. The target gene of miR-582-3p was verified using a dual-luciferase reporter assay. The G2/M phase arrest-related molecule contents were measured using western blotting analysis.

RESULTS

We found miR-582-3p was significantly downregulated in the blood samples from leukemia patients and in the cell lines. MiR-582-3p overexpression significantly impaired cell proliferation and induced G2/M cell cycle arrest in THP-1 cells. Furthermore, cyclin B2 (CCNB2) was confirmed as a target gene of miR-582-3p and found to be negatively regulated by miR-582-3p overexpression. More importantly, CCNB2 knockdown showed suppressive effects on cell proliferation and cell cycle progression similar to those caused by miR-582-3p overexpression. The inhibitory effects of miR-582-3p overexpression on cell proliferation and cell cycle progression were abrogated by CCNB2 transfection.

CONCLUSION

These findings indicate new functions and mechanisms for miR-582-3p in AML development. Further study could clarify if miR-582-3p and CCNB2 are potential therapeutic targets for the treatment of AML.

The ascidian natural product eusynstyelamide B is a novel topoisomerase II poison that induces DNA damage and growth arrest in prostate and breast cancer cells

As part of an anti-cancer natural product drug discovery program, we recently identified eusynstyelamide B (EB), which displayed cytotoxicity against MDA-MB-231 breast cancer cells (IC₅₀ = 5 μM) and induced apoptosis. Here, we investigated the mechanism of action of EB in cancer cell lines of the prostate (LNCaP) and breast (MDA-MB-231). EB inhibited cell growth (IC₅₀ = 5 μM) and induced a G2 cell cycle arrest, as shown by a significant increase in the G2/M cell population in the absence of elevated levels of the mitotic marker phospho-histone H3. In contrast to MDA-MB-231 cells, EB did not induce cell death in LNCaP cells when treated for up to 10 days. Transcript profiling and Ingenuity Pathway Analysis suggested that EB activated DNA damage pathways in LNCaP cells. Consistent with this, CHK2 phosphorylation was increased, p21^CIP1/WAF1 was up-regulated and CDC2 expression strongly reduced by EB. Importantly, EB caused DNA double-strand breaks, yet did not directly interact with DNA. Analysis of topoisomerase II-mediated decatenation discovered that EB is a novel topoisomerase II poison.

Antitumour potential of BPT: a dual inhibitor of cdk4 and tubulin polymerization

The marine natural product fascaplysin (1) is a potent Cdk4 (cyclin-dependent kinase 4)-specific inhibitor, but is toxic to all cell types possibly because of its DNA-intercalating properties. Through the design and synthesis of numerous fascaplysin analogues, we intended to identify inhibitors of cancer cell growth with good therapeutic window with respect to normal cells. Among various non-planar tryptoline analogues prepared, N-(biphenyl-2-yl) tryptoline (BPT, 6) was identified as a potent inhibitor of cancer cell growth and free from DNA-binding properties owing to its non-planar structure. This compound was tested in over 60 protein kinase assays. It displayed inhibition of Cdk4-cyclin D1 enzyme in vitro far more potently than many other kinases including Cdk family members. Although it blocks growth of cancer cells deficient in the mitotic-spindle checkpoint at the G0/G1 phase of the cell cycle, the block occurs primarily at the G2/M phase. BPT inhibits tubulin polymerization in vitro and acts as an enhancer of tubulin depolymerization of paclitaxel-stabilized tubulin in live cells. Western blot analyses indicated that, in p53-positive cells, BPT upregulates the expression of p53, p21 and p27 proteins, whereas it downregulates the expression of cyclin B1 and Cdk1. BPT selectively kills SV40-transformed mouse embryonic hepatic cells and human fibroblasts rather than untransformed cells. BPT inhibited the growth of several human cancer cells with an IC50<1 μM. The pharmacokinetic study in BALB/c mice indicated good plasma exposure after intravenous administration. It was found to be efficacious at 1/10th the maximum-tolerated dose (1000 mg/kg) against human tumours derived from HCT-116 (colon) and NCI-H460 (lung) cells in SCID (severe-combined immunodeficient) mice models. BPT is a relatively better anticancer agent than fascaplysin with an unusual ability to block two overlapping yet crucial phases of the cell cycle, mitosis and G0/G1. Its ability to effectively halt tumour growth in human tumour-bearing mice would suggest that BPT has the potential to be a candidate for further clinical development.

Curcumin cytotoxicity is enhanced by PTEN disruption in colorectal cancer cells

AIM

To investigate the effects of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) deficiency on the cytotoxicity of chemotherapeutic agents toward colorectal cancer cells.

METHODS

PTEN-deficient colorectal cancer (CRC) cells were generated by human somatic cell gene targeting using the adeno-associated virus system. The cytotoxic effects of compounds including curcumin, 5-fluorouracil (5-FU), dihydroartemisinin (DHA), irinotecan (CPT-11) and oxaliplatin (OXA) on cancer cells were determined using the MTT assay. Enhanced cytotoxicity of curcumin in PTEN-deficient CRC cells was observed, and this was confirmed using clonogenic assays. Apoptosis and cell cycle progression were analyzed by flow cytometry. Levels of apoptosis and cell cycle-related proteins were examined by Western blotting.

RESULTS

We developed an isogenic set of CRC cell lines that differed only in their PTEN status. Using this set of cell lines, we found that disruption of the PTEN gene had no effect on the sensitivity of CRC cells to 5-FU, CPT-11, DHA, or OXA, whereas PTEN disruption increased the sensitivity of CRC cells to curcumin. Loss of PTEN did not alter the curcumin-induced apoptosis in CRC cells. However, PTEN deficiency led to an altered pattern of curcumin-mediated cell cycle arrest. In HCT116 PTEN (+/+) cells, curcumin caused a G2/M phase arrest, whereas it caused a G0/G1 phase arrest in HCT116 PTEN (-/-) cells. Levels of cell cycle-related proteins were consistent with these respective patterns of cell cycle arrest.

CONCLUSION

Curcumin shows enhanced cytotoxicity toward PTEN-deficient cancer cells, suggesting that it might be a potential chemotherapeutic agent for cancers harboring PTEN mutations.

Phenylhydroquinone induces loss of thymocytes through cell cycle arrest and apoptosis elevation in p53-dependent pathway

ortho-Phenylphenol has been employed in post-harvest treatment of citrus fruits. Although o-phenylphenol has been reported to cause carcinomas in the urinary tract in rats, toxicity to the immune organs is still unknown. Herein, we report that administration of o-phenylphenol induces thymic atrophy and loss of thymocytes in female BALB/c mice. The influence seems to result from inhibition of the thymocyte development, because increased and decreased populations of the CD4⁻ CD8⁻ double-negative and CD4⁺ CD8⁺ double-positive thymocytes were observed in the o-phenylphenol-administered mice, respectively. ortho-Phenylphenol is metabolized to phenylhydroquinone by cytochrome P450 monooxygenases. Phenylhydroquinone made cell cycle of thymocytes to be arrested through reduced expression of the genes associated with G₂/M phase and through phosphorylation of p53 at Ser15. Phosphorylation of p53 at Ser15 was upregulated by activation of not only ATR but also Erk1/2 and p38, leading to increase of apoptosis. Gene expression of cytochrome P450 1A1 (CYP1A1) was promoted in thymocytes from the o-phenylphenol-administered mice. Overall, our results suggest that o-phenylphenol induces CYP1A1 expression and is metabolized into phenylhydroquinone by the expressed CYP1A1 in thymocytes. The produced phenylhydroquinone in turn induces inhibition of thymocyte development through cell cycle arrest and apoptosis in the p53-dependent pathway.

A randomised controlled phase II trial of pre-operative celecoxib treatment reveals anti-tumour transcriptional response in primary breast cancer

Introduction

Cyclooxygenase-2 (COX-2) is frequently over-expressed in primary breast cancer. In transgenic breast cancer models, over-expression of COX-2 leads to tumour formation while COX-2 inhibition exerts anti-tumour effects in breast cancer cell lines. To further determine the effect of COX-2 inhibition in primary breast cancer, we aimed to identify transcriptional changes in breast cancer tissues of patients treated with the selective COX-2 inhibitor celecoxib.

Methods

In a single-centre double-blind phase II study, thirty-seven breast cancer patients were randomised to receive either pre-operative celecoxib (400 mg) twice daily for two to three weeks (n = 22) or a placebo according to the same schedule (n = 15). Gene expression in fresh-frozen pre-surgical biopsies (before treatment) and surgical excision specimens (after treatment) was profiled by using Affymetrix arrays. Differentially expressed genes and altered pathways were bioinformatically identified. Expression of selected genes was validated by quantitative PCR (qPCR). Immunohistochemical protein expression analyses of the proliferation marker Ki-67, the apoptosis marker cleaved caspase-3 and the neo-angiogenesis marker CD34 served to evaluate biological response.

Results

We identified 972 and 586 significantly up- and down-regulated genes, respectively, in celecoxib-treated specimens. Significant expression changes in six out of eight genes could be validated by qPCR. Pathway analyses revealed over-representation of deregulated genes in the networks of proliferation, cell cycle, extracellular matrix biology, and inflammatory immune response. The Ki-67 mean change relative to baseline was -29.1% (P = 0.019) and -8.2% (P = 0.384) in the treatment and control arm, respectively. Between treatment groups, the change in Ki-67 was statistically significant (P = 0.029). Cleaved caspase-3 and CD34 expression were not significantly different between the celecoxib-treated and placebo-treated groups.

Conclusions

Short-term COX-2 inhibition by celecoxib induces transcriptional programs supporting anti-tumour activity in primary breast cancer tissue. The impact on proliferation-associated genes is reflected by a reduction of Ki-67 positive cells. Therefore, COX-2 inhibition should be considered as a treatment strategy for further clinical testing in primary breast cancer.

Trial registration

ClinicalTrials.gov NCT01695226.

Effects of flavocoxid, a dual inhibitor of COX and 5-lipoxygenase enzymes, on benign prostatic hyperplasia

BACKGROUND AND PURPOSE

Inflammation plays a key role in the development of benign prostatic hyperplasia (BPH). Eicosanoids derived from the COX and 5-lipoxygenase (5-LOX) pathways are elevated in the enlarging prostate. Flavocoxid is a novel flavonoid-based 'dual inhibitor' of the COX and 5-LOX enzymes. This study evaluated the effects of flavocoxid in experimental BPH.

EXPERIMENTAL APPROACH

Rats were treated daily with testosterone propionate (3 mg·kg(-1)  s.c.) or its vehicle for 14 days to induce BPH. Animals receiving testosterone were randomized to receive vehicle (1 mL·kg(-1) , i.p.) or flavocoxid (20 mg·kg(-1) , i.p.) for 14 days. Histological changes, eicosanoid content and mRNA and protein levels for apoptosis-related proteins and growth factors were assayed in prostate tissue. The effects of flavocoxid were also tested on human prostate carcinoma PC3 cells.

KEY RESULTS

Flavocoxid reduced prostate weight and hyperplasia, blunted inducible expression of COX-2 and 5-LOX as well as the increased production of PGE(2) and leukotriene B(4) (LTB(4) ), enhanced pro-apoptotic Bax and caspase-9 and decreased the anti-apoptotic Bcl-2 mRNA. Flavocoxid also reduced EGF and VEGF expression. In PC3 cells, flavocoxid stimulated apoptosis and inhibited growth factor expression. Flavocoxid-mediated induction of apoptosis was inhibited by the pan-caspase inhibitor, Z-VAD-FMK, in PC3 cells, suggesting an essential role of caspases in flavocoxid-mediated apoptosis during prostatic growth.

CONCLUSION AND IMPLICATIONS

Our results show that a 'dual inhibitor' of the COX and 5-LOX enzymes, such as flavocoxid, might represent a rational approach to reduce BPH through modulation of eicosanoid production and a caspase-induced apoptotic mechanism.

Antitumor activity of the selective cyclooxygenase-2 inhibitor, celecoxib, on breast cancer in Vitro and in Vivo

BACKGROUND

Cyclooxygenase-2(COX-2) promotes carcinogenesis, tumor proliferation, angiogenesis, prevention of apoptosis, and immunosuppression. Meanwhile, COX-2 over-expression has been associated with tumor behavior and prognosis in several cancers. This study investigated the antitumor effects of the selective COX-2 inhibitor, Celecoxib, on breast cancer in vitro and in vivo.

METHODS

Human breast cancer MCF-7 and MDA-MB-231 cells were cultured with different concentration (10, 20, 40 μmol/L) of celecoxib after 0-96 hours in vitro. MTT assay was used to determine the growth inhibition of breast cancer cells in vitro. The expression of COX-2 on mRNA was measured by real-time quantitive PCR analysis. Flow cytometry was performed to analyze the cell cycle of MCF-7 cells. Levels of PGE2 were measured by ELISA method. The in vivo therapeutic effects of celecoxib were determined using rat breast cancer chemically induced by 7,12-dimethylben anthracene (DMBA).

RESULTS

The inhibition of proliferation of both MCF-7 and MDA-MB-231 cells in vitro by celecoxib was observerd in time and dose dependent manner. Celecoxib effectively down-regulated the expression of COX-2. The cell cycle was arrested at G0/G1, and rate of cells in S phase was obviously decreased. Levels of PGE2 were inhibited by Celecoxib. The tumor incidence rate of the celecoxib group was lower than that of the control group. In addition, the tumor latency period of the celecoxib group was longer than that of the control group.

CONCLUSIONS

Celecoxib inhibited the proliferation of breast cancer cell lines in vitro, and prevented the occurrence of rat breast cancer chemically induced by DMBA. Therefore, celecoxib exhibits an antitumor activity and seems to be effective in anti-tumor therapy.

Pirarubicin inhibits multidrug-resistant osteosarcoma cell proliferation through induction of G2/M phase cell cycle arrest

AIM

Pirarubicin (THP) is recently found to be effective in treating patients with advanced, relapsed or recurrent high-grade osteosarcoma. In this study, the effects of THP on the multidrug-resistant (MDR) osteosarcoma cells were assessed, and the underlying mechanisms for the disruption of cell cycle kinetics by THP were explored.

METHODS

Human osteosarcoma cell line MG63 and human MDR osteosarcoma cell line MG63/DOX were tested. The cytotoxicity of drugs was examined using a cell proliferation assay with the Cell Counting Kit-8 (CCK-8). The distribution of cells across the cell cycle was determined with flow cytometry. The expression of cell cycle-regulated genes cyclin B1 and Cdc2 (CDK1), and the phosphorylated Cdc2 and Cdc25C was examined using Western blot analyses.

RESULTS

MG63/DOX cells were highly resistant to doxorubicin (ADM) and gemcitabine (GEM), but were sensitive or lowly resistant to THP, methotrexate (MTX) and cisplatin (DDP). Treatment of MG63/DOX cells with THP (200-1000 ng/mL) inhibited the cell proliferation in time- and concentration-dependent manners. THP (50-500 ng/mL) induced MG63/DOX cell cycle arrest at the G(2)/M phase in time- and concentration-dependent manners. Furthermore, the treatment of MG63/DOX cells with THP (200-1000 ng/mL) downregulated cyclin B1 expression, and decreased the phosphorylated Cdc2 at Thr(161). Conversely, the treatment increased the phosphorylated Cdc2 at Thr(14)/Tyr(15) and Cdc25C at Ser(216), which led to a decrease in Cdc2-cyclin B1 activity.

CONCLUSION

The cytotoxicity of THP to MG63/DOX cells may be in part due to its ability to arrest cell cycle progression at the G(2)/M phase, which supports the use of THP for managing patients with MDR osteosarcoma.

Paris chinensis dioscin induces G2/M cell cycle arrest and apoptosis in human gastric cancer SGC-7901 cells

AIM: To investigate the anti-tumor effects of Paris chinensis dioscin (PCD) and mechanisms regarding cell cycle regulation and apoptosis in human gastric cancer SGC-7901 cells.

METHODS: Cell viability was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Cell apoptosis was evaluated by flow cytometry and laser scanning confocal microscope (LSCM) using Annexin-V/propidium iodide (PI) staining, and the cell cycle was evaluated using PI staining with flow cytometry. Intracellular calcium ions were detected under fluorescence microscope. The expression of cell cycle and apoptosis-related proteins cyclin B1, CDK1, cytochrome C and caspase-3 was measured by immunohistochemical staining.

RESULTS: PCD had an anti-proliferation effect on human gastric cancer SGC-7901 cells in a dose- and time-dependent manner. After treatment of SGC-7901 cells with PCD, apoptosis appeared in SGC-7901 cells. Morphological changes typical of apoptosis were also observed with LSCM by Annexin V/PI staining, and the cell number of the G0/G1 phase was decreased, while the number of cells in the G2/M phase was increased. Cell cycle-related proteins, such as cyclin B1 and CDK1, were all down-regulated, but caspase-3 and cytochrome C were up-regulated. Moreover, intracellular calcium accumulation occurred in PCD-treated cells.

CONCLUSION: G2/M phase arrest and apoptosis induced by PCD are associated with the inhibition of CDK-activating kinase activity and the activation of Ca²⁺-related mitochondrion pathway in SGC-7901 cells.

Inhibition of AP-1 suppresses cervical cancer cell proliferation and is associated with p21 expression

AP-1, a transcription factor comprised primarily of Jun and Fos family proteins, regulates genes involved in proliferation, differentiation and oncogenesis. Previous studies demonstrated that elevated expression of Jun and Fos family member proteins is associated with numerous human cancers and in cancer-relevant biological processes. In this study we used a dominant-negative mutant of c-Jun, Tam67, which interferes with the functional activity of all AP-1 complexes, to investigate the requirement of AP-1 in the proliferation and cell cycle progression of cervical cancer cells. Transient and stable expression of Tam67 in CaSki cervical cancer cells resulted in decreased AP-1 activity that correlated with a significant inhibition of cell proliferation and anchorage-independent colony formation. Inhibiting AP-1 activity resulted in a two-fold increase in cells located in the G2/M phase of the cell cycle and an accompanying increase in the expression of the cell cycle regulatory protein, p21. The increase in p21 was associated with a decrease in HPV E6 expression and an increase in p53. Importantly, blocking the induction of p21 in CaSki-Tam67-expressing cells accelerated their proliferation rate to that of CaSki, implicating p21 as a key player in the growth arrest induced by Tam67. Our results suggest a role for AP-1 in the proliferation, G2/M progression and inhibition of p21 expression in cervical cancer.

A human ribonuclease induces apoptosis associated with p21WAF1/CIP1 induction and JNK inactivation

Background

Ribonucleases are promising agents for use in anticancer therapy. Among the different ribonucleases described to be cytotoxic, a paradigmatic example is onconase which manifests cytotoxic and cytostatic effects, presents synergism with several kinds of anticancer drugs and is currently in phase II/III of its clinical trial as an anticancer drug against different types of cancer. The mechanism of cytotoxicity of PE5, a variant of human pancreatic ribonuclease carrying a nuclear localization signal, has been investigated and compared to that of onconase.

Methods

Cytotoxicity was measured by the MTT method and by the tripan blue exclusion assay. Apoptosis was assessed by flow cytometry, caspase enzymatic detection and confocal microscopy. Cell cycle phase analysis was performed by flow cytometry. The expression of different proteins was analyzed by western blot.

Results

We show that the cytotoxicity of PE5 is produced through apoptosis, that it does not require the proapoptotic activity of p53 and is not prevented by the multiple drug resistance phenotype. We also show that PE5 and onconase induce cell death at the same extent although the latter is also able to arrest the cell growth. We have compared the cytotoxic effects of both ribonucleases in the NCI/ADR-RES cell line by measuring their effects on the cell cycle, on the activation of different caspases and on the expression of different apoptosis- and cell cycle-related proteins. PE5 increases the number of cells in S and G₂/M cell cycle phases, which is accompanied by the increased expression of cyclin E and p21^WAF1/CIP1 together with the underphosphorylation of p46 forms of JNK. Citotoxicity of onconase in this cell line does not alter the cell cycle phase distribution and it is accompanied by a decreased expression of XIAP

Conclusions

We conclude that PE5 kills the cells through apoptosis associated with the p21^WAF1/CIP1 induction and the inactivation of JNK. This mechanism is significantly different from that found for onconase.

25-Hydroxycholesterol exerts both a cox-2-dependent transient proliferative effect and cox-2-independent cytotoxic effect on bovine endothelial cells in a time- and cell-type-dependent manner

Background

25-hydroxycholesterol (25-OHC) is a product of oxidation of dietary cholesterol present in human plasma. 25-OHC and other oxidized forms of cholesterol are implicated in modulating inflammatory responses involved in development of atherosclerosis and colon carcinogenesis.

Methods

Primary lymphatic, venous and arterial endothelial cells isolated from bovine mesentery (bmLEC, bmVEC, bmAEC) were treated with 25-OHC and tested for several different cellular parameters.

Results

We found 25-OHC to be a potent inducer of cyclooxygenase-2 (Cox-2, prostaglandin G-H synthase-2) expression in bovine mesenteric lymphatic, venous, and arterial endothelial cells. The induction of Cox-2 expression in endothelial cells by 25-OHC led to an initial increase in cellular proliferation that was inhibited by the Cox-2 selective inhibitor celecoxib (Celebrex). Prolonged exposure to 25-OHC was cytotoxic. Furthermore, endothelial cells induced to express Cox-2 by 25-OHC were more sensitive to the effects of the Cox-2 selective inhibitor celecoxib (Celebrex). These results suggest that some effects of 25-OHC on cells may be dependent on Cox-2 enzymatic activity.

Conclusions

Cox-2 dependent elevating effects of 25-OHC on endothelial cell proliferation was transient. Prolonged exposure to 25-OHC caused cell death and enhanced celecoxib-induced cell death in a cell-type dependent manner. The lack of uniform response by the three endothelial cell types examined suggests that our model system of primary cultures of bmLECs, bmVECs, and bmAECs may aid the evaluation of celecoxib in inhibiting proliferation of different types of tumour-associated endothelial cells.

Neurogenic transdifferentiation of human adipose-derived stem cells? A critical protocol reevaluation with special emphasis on cell proliferation and cell cycle alterations

Adipose-derived stem cells (ASCs) are reported to display multilineage differentiation potential, including neuroectodermal pathways. The aim of the present study was to critically re-evaluate the potential neurogenic (trans-)differentiation capacity of ASCs using a neurogenic induction protocol based on the combination of isobutylmethylxanthine (IBMX), indomethacin and insulin. ASCs isolated from lipo-aspirate samples of five healthy female donors were characterized and potential neurogenic (trans-)differentiation was assessed by means of immunohistochemistry and gene expression analyses. Cell proliferation and cell cycle alterations were studied, and the expression of CREB/ATF transcription factors was analyzed. ASCs expressed CD59, CD90 and CD105, and were tested negative for CD34 and CD45. Under neurogenic induction, ASCs adopted a characteristic morphology comparable to neur(on)al progenitors and expressed musashi1, β-III-tubulin and nestin. Gene expression analyses revealed an increased expression of β-III-tubulin, GFAP, vimentin and BDNF, as well as SOX4 in induced ASCs. Cell proliferation was significantly reduced under neurogenic induction; cell cycle analyses showed a G2-cell cycle arrest accompanied by differential expression of key regulators of cell cycle progression. Differential expression of CREB/ATF transcription factors could be observed on neurogenic induction, pointing to a decisive role of the cAMP-CREB/ATF system. Our findings may point to a potential neurogenic (trans-)differentiation of ASCs into early neur(on)al progenitors, but do not present definite evidence for it. Especially, the adoption of a neural progenitor cell-like morphology must not automatically be misinterpreted as a specific characteristic of a respective (trans-)differentiation process, as this may as well be caused by alterations of cell cycle progression.

Role of eicosanoids on intestinal epithelial homeostasis

The intestinal epithelium is a highly dynamic system that is continuously renewed by a process involving cell proliferation and differentiation. Moreover, it is the main interface with the external environment, and maintenance and regulation of the epithelial structure and epithelial barrier function are key determinants of digestive health and host well being. The tight junction, a multiprotein complex composed of transmembrane proteins associated with the cytoskeletal peri-junctional ring of actin and myosin, is an essential component of this barrier that is strictly regulated in a spatio-temporal manner by a complex signaling network. Defects in the intestinal epithelial barrier function have been observed in inflammatory bowel disease, and a classic example of the connection between inflammation and cancer is the increased risk of colorectal cancer in patients with inflammatory bowel disease. In recent years, several molecules have emerged as critical players contributing to inflammation-associated colorectal cancer. For example, eicosanoids derived from arachidonic acid are proposed as mediators involved in the regulation of epithelial structure/function. Interestingly, the tissue concentration of eicosanoids increases during mucosal inflammation and colorectal cancer development. This overview focuses on the physiological and physiopathological roles of eicosanoids in cell growth/cell differentiation/apoptosis and in the paracellular permeability of the intestinal epithelium. A better understanding of these processes will foster new ideas for the development of therapies for these chronic disorders.

Anti-cancer effects of celecoxib in head and neck carcinoma

Although many studies highlighted cyclooxygenase2 (COX2) inhibition as a promising therapeutic strategy for cancer, more evidence is needed for clinical application. The purpose of this study was to investigate the feasibility of COX2 inhibition as a strategic treatment modality for head and neck carcinoma (HNC). We tested COX2 inhibitor, celecoxib in six types of HNC cells and analyzed the expression changes in proteins related to angiogenesis and apoptosis in vitro. We also evaluated proliferation, gelatinolysis and in vitro invasion. We used a hamster carcinogenesis model and a mouse tumorigenesis model for the in vivo evaluation of COX2 inhibition. We performed immunohistochemistry to assess changes in the expression of COX2, survivin and angiogenesis. Celecoxib administration caused decreases in the expressions of COX2, VEGF and survivin in vitro. Proliferation, in vitro invasion and gelatinolytic activity were reduced in HNC cell lines, but the effect was inconsistent across lines. COX2 inhibition retarded oral carcinogenesis from an early carcinogenic stage with increased apoptosis and decreased survivin expression. COX2 inhibition did not inhibit tumor growth, even with the COX2 downregulation and decrease in neovascularization. We conclude that COX2 inhibition has a chemopreventive effect, but its application as a treatment of HNC in a clinical setting still requires further research to overcome its limited anti-cancer effects.

Enhanced sensitivity of celecoxib in human glioblastoma cells: Induction of DNA damage leading to p53-dependent G1 cell cycle arrest and autophagy

BACKGROUND

Selective cyclooxygenase (COX)-2 inhibitors elicit anti-proliferative responses in various tumours, however the underlying anti-tumour mechanisms are unclear. Mutational inactivation of the tumour suppressor p53 gene is frequent in malignant gliomas. The role of p53 mutation in the anti-tumour responses of the selective COX-2 inhibitor celecoxib in human glioblastoma cells is unknown. In this study, we used human glioblastoma cells with various p53 status; U87MG (with high and low p53 functional levels), LN229 (functional p53) and U373MG (mutant p53) cells. Inhibition of p53 was achieved in U87MG cells transfected with E6 oncoprotein (U87MG-E6) and treated with pifithrin-alpha, a reversible inhibitor of p53 (U87MG-PFT). We investigated whether the anti-glioblastoma responses of celecoxib were p53-dependent, and whether celecoxib induced DNA damage leading to p53-dependent G1 cell cycle arrest, followed by autophagy or apoptosis.

RESULTS

Our findings demonstrated that celecoxib concentration-dependently reduced glioblastoma cell viability, following 24 and 72 hours of treatment. Inhibition of functional p53 in glioblastoma cells significantly reduced the anti-proliferative effect of celecoxib. In U87MG cells, celecoxib (8 and 30 muM) significantly induced DNA damage and inhibited DNA synthesis, corresponding with p53 activation. Celecoxib induced G1-phase cell cycle arrest, accompanied with p21 activation in U87MG cells. Cell cycle progression of U87MG-E6 and U87MG-PFT cells was not affected by celecoxib. In parallel, celecoxib induced G1 cell cycle arrest in LN229 cells, but not in U373MG cells. Autophagy was induced by celecoxib in U87MG and LN229 cells, as shown by the significantly greater population of acridine orange-stained cells and increased levels of LC3-II protein (in comparison with non-treated controls). Celecoxib did not induce significant autophagy in U87MG-PFT, U87MG-E6 and U373MG cells, which lack functional p53. Regardless of p53 status, celecoxib caused no significant difference in apoptosis level of U87MG, U87MG-PFT, U87MG-E6 and U373MG cells.

CONCLUSION

Our findings reveal that p53 increases human glioblastoma sensitivity to celecoxib. Celecoxib inhibits glioblastoma cell viability by induction of DNA damage, leading to p53-dependent G1 cell cycle arrest and p53-dependent autophagy, but not apoptosis.

Evaluation of the novel mitotic modulator ON 01910.Na in pancreatic cancer and preclinical development of an ex vivo predictive assay

The pupose of this study was to evaluate the activity of ON 01910.Na, a mitotic inhibitor, in in vitro and in vivo models of pancreatic cancer and to discover biomarkers predictive of efficacy. Successive in vitro and in vivo models were used; these included cell line-derived and patient-derived tumors from our PancXenoBank, a live collection of freshly generated pancreatic cancer xenografts. ON 01910.Na showed equivalent activity to gemcitabine against pancreatic cancer cell lines in vitro. The activity of the agent correlated with suppression of phospho-CDC25C and cyclin B1. These markers were optimized for a fine-needle aspirate ex vivo rapid assay. Cyclin B1 mRNA evaluation yielded the most optimal combination of accuracy and reproducibility. Next, nine patient-derived tumors from the PancXenoBank were profiled using the assay developed in cell lines and treated with ON01910.Na for 28 days. Two cases were cataloged as potential responders and seven as resistants. There was a correlation between the ex vivo assay and sensitivity to the tested agent, as the two cases prospectively identified as sensitive met prespecified criteria for response. Of the seven tumors of predictive resistant, only one was found to be sensitive to ON 01910.Na. In addition, there was a good correlation between cyclin B1 downregulation ex vivo and changes in cyclin B1 protein post-treatment. The novel mitotic inhibitor, ON 01910.Na, showed activity in preclinical model of pancreatic cancer. A rapid assay was rationally developed that not only identified cases sensitive to ON 01910.Na, but also anticipated the pharmacodynamic events occurring after in vivo exposure.

Combined action of celecoxib and ionizing radiation in prostate cancer cells is independent of pro-apoptotic Bax

BACKGROUND AND PURPOSE

The cyclooxygenase-2-inhibitor celecoxib has been shown to inhibit cell growth and to reduce prostatic intraepithelial neoplasia in mice. The drug was suggested to increase efficacy of ionizing radiation. However, extent and mechanisms of the suggested benefit of celecoxib on the radiation response are still unclear. The aim of the present study was to analyze cytotoxic efficacy of celecoxib in combination with irradiation on human prostate cancer cell lines and to define the importance of pro-apoptotic Bax in this process.

MATERIALS AND METHODS

Induction of apoptosis and global and clonogenic cell survival upon irradation- (2-10Gy), celecoxib- (10-75microM) or combined treatment were evaluated in prostate cancer cells by fluorescence microscopy, WST-1 assay and standard colony formation assays.

RESULTS

Celecoxib <25microM caused morphological changes and growth inhibition without substantial apoptosis or radiosensitization in terms of decreased clonogenic cell survival. In contrast, celecoxib 25microM increased radiation-induced cell death and clonogenic kill. While radiation-induced clonogenic death was increased in the presence of Bax, effects of celecoxib or combined treatment were Bax independent.

CONCLUSIONS

Our findings reveal Bax-independent beneficial effects of celecoxib on radiation-induced apoptosis and eradication of clonogenic prostate cancer cells in vitro providing a rationale for clinical evaluation of high-dose celecoxib in combination with irradiation in prostate cancer patients.

Celecoxib inhibits proliferation of retinal pigment epithelial and choroid-retinal endothelial cells by a cyclooxygenase-2-independent mechanism

Age-related macular degeneration (ARMD) is a leading cause of blindness. The major reason for severe vision loss in ARMD is choroidal neovascularization due to an elevation in the expression of angiogenic factors such as vascular endothelial growth factor (VEGF). Drugs with anti-VEGF and antiproliferative activities can be beneficial for the treatment of this disorder. We have previously demonstrated that celecoxib [a selective cyclooxygenase (Cox)-2 inhibitor] inhibits VEGF expression in retinal pigment epithelial cells. In this study, we investigated the antiproliferative effects of celecoxib in adult retinal pigment epithelial (ARPE-19) and choroidal endothelial (RF/6A) cells. The results indicate that celecoxib 1) causes a dose-dependent antiproliferative effect in ARPE-19 and RF/6A cells (IC(50) of 23 and 13 microM, respectively); 2) leads to a G(2)-M phase cell cycle arrest in these cell types; and 3) inhibits VEGF-induced proliferation of RF/6A cells (IC(50) of 20 microM). In addition, 4) the concentrations of celecoxib required for antiproliferative effects are lower than those required for the cytotoxicity. These effects of celecoxib are by mechanisms independent of its Cox-2 inhibitory activity because rofecoxib (another Cox-2 inhibitor) had no effects on the proliferation or cell cycle distribution of the two cell types, and flurbiprofen (an inhibitor of Cox-1 and Cox-2) had weak antiproliferative effects on ARPE-19 cells, with IC(50) of 90 microM. In summary, celecoxib has potent antiproliferative effects in RF/6A and ARPE-19 cells; thus, it can be a potential new treatment in proliferative disorders of the choroid-retina such as choroidal neovascularization in age-related macular degeneration.

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.

The cyclin-dependent kinase inhibitors p15INK4B and p21CIP1 are critical regulators of fibrillar collagen-induced tumor cell cycle arrest

The extracellular matrix is a crucial component in determining cell fate. Fibrillar collagen in its native form inhibits cell proliferation, whereas in its monomeric form it stimulates proliferation. The observation of elevated levels of p27(KIP1) in cells plated in the presence of fibrillar collagen has led to the assumption that this kinase inhibitor was responsible for cell cycle arrest on fibrillar collagen. Here we provide evidence that p15(INK4b), rather than p27(KIP1), is the cyclin-dependent kinase inhibitor responsible for G0/G1 arrest of human melanoma cells grown on fibrillar collagen. Additionally, we demonstrate that fibrillar collagen can also arrest cells at the G2 phase, which is mediated in part by p21(CIP1). Our data, in addition to identifying cyclin-dependent kinase inhibitors important in cell cycle arrest mediated by fibrillar collagen, demonstrate the complexity of cell cycle regulation and indicate that modulating a single cyclin-dependent kinase inhibitor does not disrupt cell proliferation in the presence of fibrillar collagen.

Phase-II study of dose attenuated schedule of irinotecan, capecitabine, and celecoxib in advanced colorectal cancer

BACKGROUND

The cyclooxygenase-2 (COX-2) enzyme plays a major role in tumor progression and resistance to chemotherapy. A Phase-II study was undertaken to determine the activity of a dose attenuated schedule of irinotecan, capecitabine, and the COX-2 inhibitor celecoxib in patients with advanced colorectal cancer.

METHODS

The eligibility criteria included a pathologically or cytologically confirmed diagnosis of adenocarcinoma of the colon or rectum that was metastatic. Patients received a combination of irinotecan 70 mg/m2 over 30 min I.V. on days 1 and 8, capecitabine 1,000 mg/m2 twice per day orally on days 1-14, and celecoxib at a daily dose of 800 mg continuously. Cycles were repeated every 21 days.

RESULTS

Fifty-one patients were enrolled (median age 58 years; M : F 31 : 20). The objective response rate was 21/51 = 41% [95% confidence intervals (CI), 0.28-0.55]. The median time to progression was 7.7 months (95% CI, 6.2-8.6 months). Median survival time and probability of survival at 1 year were 21.2 months (95% CI, 13.8-n/a), and 75% (95% CI, 0.63-0.88), respectively. The major toxicity was Grade 3 or 4 diarrhea, seen in 24 and 10% of patients, respectively. There were no treatment related deaths.

CONCLUSIONS

The lower dose intensity of irinotecan appeared to maintain activity and improve tolerability when combined with capecitabine. The addition of celecoxib to irinotecan and capecitabine did not appear to significantly increase the activity of this doublet based on the RECIST criteria for objective response.

Celecoxib attenuates 5-fluorouracil-induced apoptosis in HCT-15 and HT-29 human colon cancer cells

AIM: To investigate the combined chemotherapeutic effects of celecoxib when used with 5-FU in vitro.

METHODS: Two human colon cancer cell lines (HCT-15 and HT-29) were treated with 5-FU and celecoxib, alone and in combination. The effects of each drug were evaluated using the MTT [3- (4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay, flow cytometry, and western blotting.

RESULTS: 5-FU and celecoxib showed a dose-dependent cytotoxic effect. When treated with 10^-3 mol/L 5-FU (IC₅₀) and celecoxib with its concentration ranging from 10^-8 mol/L to 10^-4 mol/L of celecoxib, cells showed reduced cytotoxic effect than 5-FU (10^-3 mol/L) alone. Flow cytometry showed that celecoxib attenuated 5-FU induced accumulation of cells at subG1 phase. Western blot analyses for caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage showed that celecoxib attenuated 5-FU induced apoptosis. Western blot analyses for cell cycle molecules showed that G2/M arrest might be possible cause of 5-FU induced apoptosis and celecoxib attenuated 5-FU induced apoptosis via blocking of cell cycle progression to the G2/M phase, causing an accumulation of cells at the G1/S phase.

CONCLUSION: We found that celecoxib attenuated cytotoxic effect of 5-FU. Celecoxib might act via inhibition of cell cycle progression, thus preventing apoptosis induced by 5-FU.

Down-regulation of PGE2 by physiologic levels of celecoxib is not sufficient to induce apoptosis or inhibit cell proliferation in human colon carcinoma cell lines

This study was performed to evaluate whether down-regulation of prostaglandin E(2) (PGE(2)) synthesis by celecoxib treatment is associated with inhibition of cell growth in human colon carcinoma cell lines. Physiologic concentrations of celecoxib (5-10 microM) inhibited 80% to 90% of PGE(2) production in HT-29 cells that express high levels of COX-2 protein. In these concentrations, celecoxib had a minor inhibitory effect (20-30%) on cell growth. There was a significant change in induction of apoptosis only at higher concentrations of celecoxib (>20 microM). Treatment by low concentrations of celecoxib did not alter the levels of COX-1, beta-catenin, P(27), Bcl-2, and Bcl-x proteins. The effect of celecoxib on cell growth inhibition was higher on the COX-2-positive HT-29 cell line (IC(50)=20 microM) than on the COX-2 deficient SW-480 cell line (IC(50)=35 microM). In conclusion, inhibition of PGE(2) synthesis is an early, but not sufficient, step in the mechanism of celecoxib-mediated cell growth inhibition. These results support the need for additional evaluation of independent COX-2 pathways of celecoxib in chemoprevention of CRC.

IL-22-mediated tumor growth reduction correlates with inhibition of ERK1/2 and AKT phosphorylation and induction of cell cycle arrest in the G2-M phase

IL-22 is a recently discovered cytokine of the IL-10 family that binds to a class II cytokine receptor composed of IL-22R1 and IL-10R2(c) and influences a variety of immune reactions. As IL-22 has also been shown to modulate cell cycle and proliferation mediators such as ERK1/2 and JNK, we studied the role of IL-22 in proliferation, apoptosis, and cell cycle regulation in EMT6 murine breast cancer cells in vitro and in vivo. In this study, we report that murine breast cancer cells express functional IL-22R as indicated by RT-PCR studies, immunoblotting, and STAT3 activation assays. Importantly, IL-22 exposure of EMT6 cells resulted in decreased levels of phosphorylated ERK1/2 and AKT protein kinases, indicating an inhibitory effect of IL-22 on signaling pathways promoting cell proliferation. Furthermore, IL-22 induced a cell cycle arrest of EMT6 cells in the G(2)-M phase. IL-22 reduced EMT6 cell numbers and the proliferation rate by approximately 50% as measured by [(3)H]thymidine incorporation. IL-22 treatment of EMT6 tumor-bearing mice lead to a decreased tumor size and a reduced tumor cell proliferation in vivo, as determined by 3'-deoxy-3'-fluorothymidine-positron emission tomography scans. Interestingly, IL-22 did not induce apoptosis, as determined in annexin V binding assay and caspase-3 activation assay and had no effect on angiogenesis in vivo. In conclusion, our results indicate that IL-22 reduced tumor growth by inhibiting signaling pathways such as ERK1/2 and AKT phosphorylation that promote tumor cell proliferation in EMT6 cells. Therefore, IL-22 may play a role in the control of tumor growth and tumor progression.