Growth inhibition of breast epithelial cells by celecoxib is associated with upregulation of insulin-like growth factor binding protein-3 expression

Celecoxib substituted biotinylated poly(amidoamine) G3 dendrimer as potential treatment for temozolomide resistant glioma therapy and anti-nematode agent

Glioblastoma multiforme (GBM) is a one of the most widely diagnosed and difficult to treat type of central nervous system tumors. Resection combined with radiotherapy and temozolomide (TMZ) chemotherapy prolongs patients' survival only for 12 - 15 months after diagnosis. Moreover, many patients develop TMZ resistance, thus important is search for a new therapy regimes including targeted drug delivery. Most types of GBM reveal increased expression of cyclooxygenase-2 (COX-2) and production of prostaglandin E2 (PGE₂), that are considered as valuable therapeutic target. In these studies, the anti-tumor properties of the selective COX-2 inhibitor celecoxib (CXB) and biotinylated third generation of the poly(amidoamine) dendrimer substituted with 31 CXB residues (G3BC31) on TMZ -resistant U-118 MG glioma cell line were examined and compared with the effect of TMZ alone including viability, proliferation, migration and apoptosis, as well as the cellular expression of COX-2, ATP level, and PGE₂ production. Confocal microscopy analysis with the fluorescently labeled G3BC31 analogue has shown that the compound was effectively accumulated in U-118 MG cells in time-dependent manner and its localization was confirmed in lysosomes but not nuclei. G3BC31 reveal much higher cytotoxicity for U-118 MG cells at relatively low concentrations in the range of 2-4 µM with compared to CBX alone, active at 50-100 µM. This was due to induction of apoptosis and inhibition of proliferation and migration. Observed effects were concomitant with reduction of PGE₂ production but independent of COX-2 expression. We suggest that investigated conjugate may be a promising candidate for therapy of TMZ-resistant glioblastoma multiforme, although applicable in local treatment, since our previous study of G3BC31 did not demonstrate selectivity against glioma cells compared to normal human fibroblasts. However, it has to be pointed that in our in vivo studies conducted with model organism, Caenorhabditis elegans indicated high anti-nematode activity of G3BC31 in comparison with CXB alone that confirms of usefulness of that organism for estimation of anti-cancer drug toxicity.

Biomarker Modulation Study of Celecoxib for Chemoprevention in Women at Increased Risk for Breast Cancer: A Phase II Pilot Study

In preclinical studies, celecoxib has been associated with reduced risk of breast cancer. In this study, the aim was to assess the biomodulatory effect of celecoxib on blood and benign breast tissue biomarkers in women at increased risk for breast cancer. Women at increased risk for breast cancer [5-year Gail risk score of >1.67%, history of atypical hyperplasia, lobular carcinoma in situ, or previous estrogen receptor (ER)-negative breast cancer] were treated with celecoxib at 400 mg orally twice daily for 6 months. Participants underwent random periareolar fine needle aspiration and blood draw at baseline and at 6 months for analysis of biomarkers: serum levels of insulin-like growth factor 1 (IGF-1), IGF-binding protein 1 (IGFBP-1), and IGFBP-3; tissue expression of Ki-67 and ER; as well as cytology. Forty-nine patients were eligible for analysis. Median IGFBP-1 levels increased significantly from 6.05 ng/mL at baseline to 6.93 ng/mL at 6 months (P = 0.04), and median IGFBP-3 levels decreased significantly from 3,593 ng/mL to 3,420 ng/mL (P = 0.01). We also detected favorable changes in cytology of 52% of tested sites after 6 months of celecoxib therapy. No changes in tissue Ki-67 and ER expression levels were observed. No grade 3 or 4 toxicity was recorded. Celecoxib was well tolerated and induced favorable changes in serum biomarkers as well as cytology in this pilot phase II trial. A phase IIb placebo-controlled study with celecoxib could be considered for women at increased risk for breast cancer.

Celecoxib affects estrogen sulfonation catalyzed by several human hepatic sulfotransferases, but does not stimulate 17-sulfonation in rat liver

Celecoxib is known to alter the preferred position of SULT2A1-catalyzed sulfonation of 17β-estradiol (17β-E2) and other estrogens from the 3- to the 17-position. Understanding the effects of celecoxib on estrogen sulfonation is of interest in the context of the investigational use of celecoxib to treat breast cancer. This study examined the effects on celecoxib on cytosolic sulfotransferases in human and rat liver and on SULT enzymes known to be expressed in liver. Celecoxib's effects on the sulfonation of several steroids catalyzed by human liver cytosol were similar but not identical to those observed previously for SULT2A1. Celecoxib was shown to inhibit recombinant SULT1A1-catalyzed sulfonation of 10nM estrone and 4μM p-nitrophenol with IC₅₀ values of 2.6 and 2.1μM, respectively, but did not inhibit SULT1E1-catalyzed estrone sulfonation. In human liver cytosol, the combined effect of celecoxib and known SULT1A1 and 1E1 inhibitors, quercetin and triclosan, resulted in inhibition of 17β-E2-3-sulfonation such that the 17-sulfate became the major metabolite: this is of interest because the 17-sulfate is not readily hydrolyzed by steroid sulfatase to 17β-E2. Investigation of hepatic cytosolic steroid sulfonation in rat revealed that celecoxib did not stimulate 17β-E2 17-sulfonation in male or female rat liver as it does with human SULT2A1 and human liver cytosol, demonstrating that rat is not a useful model of this effect. In silico studies suggested that the presence of the bulky tryptophan residue in the substrate-binding site of the rat SULT2A homolog instead of glycine as in human SULT2A1 may explain this species difference.

Celecoxib influences steroid sulfonation catalyzed by human recombinant sulfotransferase 2A1

Celecoxib has been reported to switch the human SULT2A1-catalyzed sulfonation of 17β-estradiol (17β-E2) from the 3- to the 17-position. The effects of celecoxib on the sulfonation of selected steroids catalyzed by human SULT2A1 were assessed through in vitro and in silico studies. Celecoxib inhibited SULT2A1-catalyzed sulfonation of dehydroepiandrosterone (DHEA), androst-5-ene-3β, 17β-diol (AD), testosterone (T) and epitestosterone (Epi-T) in a concentration-dependent manner. Low μM concentrations of celecoxib strikingly enhanced the formation of the 17-sulfates of 6-dehydroestradiol (6D-E2), 17β-dihydroequilenin (17β-Eqn), 17β-dihydroequilin (17β-Eq), and 9-dehydroestradiol (9D-E2) as well as the overall rate of sulfonation. For 6D-E2, 9D-E2 and 17β-Eqn, celecoxib inhibited 3-sulfonation, however 3-sulfonation of 17β-Eq was stimulated at celecoxib concentrations below 40 μM. Ligand docking studies in silico suggest that celecoxib binds in the substrate-binding site of SULT2A1 in a manner that prohibits the usual binding of substrates but facilitates, for appropriately shaped substrates, a binding mode that favors 17-sulfonation.

Cyclooxygenase-2 and the inflammogenesis of breast cancer

Cohesive scientific evidence from molecular, animal, and human investigations supports the hypothesis that constitutive overexpression of cyclooxygenase-2 (COX-2) is a ubiquitous driver of mammary carcinogenesis, and reciprocally, that COX-2 blockade has strong potential for breast cancer prevention and therapy. Key findings include the following: (1) COX-2 is constitutively expressed throughout breast cancer development and expression intensifies with stage at detection, cancer progression and metastasis; (2) essential features of mammary carcinogenesis (mutagenesis, mitogenesis, angiogenesis, reduced apoptosis, metastasis and immunosuppression) are linked to COX-2-driven prostaglandin E2 (PGE-2) biosynthesis; (3) upregulation of COX-2 and PGE-2 expression induces transcription of CYP-19 and aromatase-catalyzed estrogen biosynthesis which stimulates unbridled mitogenesis; (4) extrahepatic CYP-1B1 in mammary adipose tissue converts paracrine estrogen to carcinogenic quinones with mutagenic impact; and (5) agents that inhibit COX-2 reduce the risk of breast cancer in women without disease and reduce recurrence risk and mortality in women with breast cancer. Recent sharp increases in global breast cancer incidence and mortality are likely driven by chronic inflammation of mammary adipose and upregulation of COX-2 associated with the obesity pandemic. The totality of evidence clearly supports the supposition that mammary carcinogenesis often evolves as a progressive series of highly specific cellular and molecular changes in response to induction of constitutive over-expression of COX-2 and the prostaglandin cascade in the “inflammogenesis of breast cancer”.

Celecoxib induces apoptosis and cell-cycle arrest in nasopharyngeal carcinoma cell lines via inhibition of STAT3 phosphorylation

AIM

To investigate the mechanisms underlying the anticancer effect of celecoxib on nasopharyngeal carcinoma (NPC).

METHODS

NPC cell lines, HNE1 and CNE1-LMP1, were treated with various concentrations of celecoxib for 48 h. The antiproliferative effect of celecoxib was assessed using MTT assay. Both cell cycle profiles and apoptosis were analyzed using flow cytometry. Western blot was used to measure the levels of signal transducer and activator of transcription 3 (STAT3), phosphorylated STAT3(Y705) (pSTAT3(Y705)), COX-2, Survivin, Mcl-1, Bcl-2 and Cyclin D1.

RESULTS

Celecoxib (10-75 μmol/L) inhibited the proliferation of the NPC cell lines in a dose-dependent manner. Celecoxib (25 and 50 μmol/L) induced apoptosis and cell-cycle arrest at the G(0)/G(1) checkpoint in the NPC cell lines, which was associated with significantly reduced STAT3 phosphorylation. The genes downstream of STAT3 (ie, Survivin, Mcl-1, Bcl-2 and Cyclin D1) were significantly down-regulated after exposure to celecoxib (25 and 50 μmol/L).

CONCLUSION

The anticancer effects of celecoxib on NPC cell lines results from inducing apoptosis and cell cycle arrest, which may be partly mediated through the STAT3 pathway.

Celecoxib synergizes human pancreatic ductal adenocarcinoma cells to sorafenib-induced growth inhibition

BACKGROUND

Pancreatic ductal adenocarcinoma is frequently associated with aberrant activation of the Ras/Raf/MAPK pathway and cyclooxygenase-2 (COX-2) overexpression. This study evaluated the potential for combining the multikinase inhibitor sorafenib and the specific COX-2 inhibitor celecoxib as therapy in pancreatic ductal adenocarcinoma cells.

METHODS

BxPC-3, MIAPaCa-2, PANC-1 and AsPC-1 pancreatic adenocarcinoma cells were exposed to sorafenib and celecoxib combined treatment in vitro. Cell viability and various growth promoting and survival signaling pathways were monitored by MTT, flow cytometry and Western blotting.

RESULTS

Combined treatment with sorafenib and celecoxib synergistically inhibited pancreatic adenocarcinoma cell proliferation. This regimen produced combination index (CI) values between 0.67 and 0.92 for the various cell lines, indicating significant synergistic interactions between sorafenib and celecoxib, which also markedly inhibited the migratory capacity. The growth inhibition was associated with an accumulation of cells in the G(0)/G(1) phase of the cell cycle and induction of apoptosis. These changes were accompanied by a significant reduction of p21(WAF1/Cip1) levels, where celecoxib sensitized the cells to sorafenib-mediated p21(WAF1/Cip1) suppression.

CONCLUSION

These results suggest that combined treatment with sorafenib and celecoxib synergistically induce growth inhibition and apoptosis in pancreatic adenocarcinoma cells through a process involving p21(WAF1/Cip1) suppression.

Interaction between cyclooxygenase-2 and insulin-like growth factor in breast cancer: A new field for prevention and treatment

The objective of this study was to evaluate the correlation between cyclooxygenase-2 (COX-2) and markers of cell proliferation and apoptosis, including, Bcl-2, Bax, Ki-67 and the type I insulin-like growth factor (IGF) receptor (IGF1-R) in ductal carcinoma in situ (DCIS) and infiltrating ductal carcinoma (IDC), present in the same surgical specimen. A total of 110 cases were evaluated using tissue microarrays. Cases were classified in scores from 0 to 3 according to pre-defined methods. The results showed that the positivity rates were COX-2 in 87% of cases in DCIS and IDC; Bcl-2 in 55% of cases in DCIS and IDC; Bax in 23% of cases in IDC and 19% in DCIS, IGF-1 in 24% of cases in DCIS and IDC; and Ki-67 in 81% of cases in DCIS and IDC. We also observed a positive correlation between the expression of COX-2 and IGF1-R (p=0.045). Our results demonstrate a positive correlation between the expression of COX-2 and IGF1-R in DCIS and IDC, demonstrating that they are involved in breast cancer carcinogenesis. Further studies are required to prove the effectiveness of COX-2 and IGF1-R inhibitors for the prevention and treatment of breast cancer, as well as to explain their mechanism of action.

Insulin-like growth factor binding protein-3 has dual effects on gastrointestinal stromal tumor cell viability and sensitivity to the anti-tumor effects of imatinib mesylate in vitro

Background

Imatinib mesylate has significantly improved survival and quality of life of patients with gastrointestinal stromal tumors (GISTs). However, the molecular mechanism through which imatinib exerts its anti-tumor effects is not clear. Previously, we found up-regulation of insulin-like growth factor binding protein-3 (IGFBP3) expression in imatinib-responsive GIST cells and tumor samples. Because IGFBP3 regulates cell proliferation and survival and mediates the anti-tumor effects of a number of anti-cancer agents through both IGF-dependent and IGF-independent mechanisms, we hypothesized that IGFBP3 mediates GIST cell response to imatinib. To test this hypothesis, we manipulated IGFBP3 levels in two imatinib-responsive GIST cell lines and observed cell viability after drug treatment.

Results

In the GIST882 cell line, imatinib treatment induced endogenous IGFBP3 expression, and IGFBP3 down-modulation by neutralization or RNA interference resulted in partial resistance to imatinib. In contrast, IGFBP3 overexpression in GIST-T1, which had no detectable endogenous IGFBP3 expression after imatinib, had no effect on imatinib-induced loss of viability. Furthermore, both the loss of IGFBP3 in GIST882 cells and the overexpression of IGFBP3 in GIST-T1 cells was cytotoxic, demonstrating that IGFBP3 has opposing effects on GIST cell viability.

Conclusion

This data demonstrates that IGFBP3 has dual, opposing roles in modulating GIST cell viability and response to imatinib in vitro. These preliminary findings suggest that there may be some clinical benefits to IGFBP3 therapy in GIST patients, but further studies are needed to better characterize the functions of IGFBP3 in GIST.

Regulation of the apoptosis-inducing kinase DRAK2 by cyclooxygenase-2 in colorectal cancer

Background:

Cyclooxygenase-2 (COX-2) is over-expressed in colorectal cancer (CRC), rendering tumour cells resistant to apoptosis. Selective COX-2 inhibition is effective in CRC prevention, although having adverse cardiovascular effects, thus focus has shifted to downstream pathways.

Methods:

Microarray experiments identified genes regulated by COX-2 in HCA7 CRC cells. In vitro and in vivo regulation of DRAK2 (DAP kinase-related apoptosis-inducing kinase 2 or STK17β, an apoptosis-inducing kinase) by COX-2 was validated by qRT-PCR.

Results:

Inhibition of COX-2 induced apoptosis and enhanced DRAK2 expression in HCA7 cells (4.4-fold increase at 4 h by qRT-PCR, P=0.001), an effect prevented by co-administration of PGE₂. DRAK2 levels were suppressed in a panel of human colorectal tumours (n=10) compared to normal mucosa, and showed inverse correlation with COX-2 expression (R=−0.68, R²=0.46, P=0.03). Administration of the selective COX-2 inhibitor rofecoxib to patients with CRC (n=5) induced DRAK2 expression in tumours (2.5-fold increase, P=0.01). In vitro silencing of DRAK2 by RNAi enhanced CRC cell survival following COX-2 inhibitor treatment.

Conclusion:

DRAK2 is a serine–threonine kinase implicated in the regulation of apoptosis and is negatively regulated by COX-2 in vitro and in vivo, suggesting a novel mechanism for the effect of COX-2 on cancer cell survival.

Celecoxib pre-treatment in human colorectal adenocarcinoma patients is associated with gene expression alterations suggestive of diminished cellular proliferation

Cancer cells treated with the cyclooxygenase-2 inhibitor celecoxib show growth inhibition and induced apoptosis. This study was conducted to determine if the same processes are relevant to celecoxib's effects on human colorectal adenocarcinomas treated in vivo. A cohort of 23 patients with primary colorectal adenocarcinomas was randomised to receive a 7-d course of celecoxib (400mg b.i.d.) or no drug prior to surgical resection. Gene expression profiling was performed on resected adenocarcinomas from the cohort of patients. Using fold change (>1.5) and p-value (<0.05) cut-offs, 190 genes were differentially expressed between adenocarcinomas from patients receiving celecoxib and those that did not. The celecoxib pre-treated samples showed decreased expression levels in multiple genes involved in cellular lipid and glutathione metabolism; changes associated with diminished cellular proliferation. Celecoxib pre-treatment for 7 d in vivo is associated with alterations in colorectal adenocarcinoma gene expression which are suggestive of diminished cellular proliferation.

Celecoxib treatment alters the gene expression profile of normal colonic mucosa

A clinical trial was recently conducted to evaluate the safety and efficacy of a selective inhibitor of cyclooxygenase-2 (celecoxib) in hereditary nonpolyposis colon cancer patients. In a randomized, placebo-controlled phase I/II multicenter trial, hereditary nonpolyposis colon cancer patients and gene carriers received either celecoxib at one of two doses or placebo. The goal was to evaluate the effects of these treatment arms on a number of endoscopic and tissue-based biomarker end points after 12 months of treatment. As part of this trial, we analyzed gene expression by cDNA array technology in normal descending (rectal) colonic mucosa of patients before and after treatment with celecoxib or placebo. We found that treatment of patients with celecoxib at recommended clinical doses (200 and 400 mg p.o. bid), in contrast to treatment with placebo, leads to changes in expression of >1,400 genes in the healthy colon, although in general, the magnitude of changes is <2-fold. Twenty-three of 25 pairs of colon biopsies taken before and after celecoxib treatment can be classified correctly by the pattern of gene expression in a leave-one-out cross-validation. Immune response, particularly T- and B-lymphocyte activation and early steps of inflammatory reaction, cell signaling and cell adhesion, response to stress, transforming growth factor-beta signaling, and regulation of apoptosis, are the main biological processes targeted by celecoxib as shown by overrepresentation analysis of the distribution of celecoxib-affected genes across Gene Ontology categories. Analysis of possible cumulative effects of celecoxib-induced changes in gene expression indicates that in healthy colon, celecoxib may suppress the immune response and early steps of inflammation, inhibit formation of focal contacts, and stimulate transforming growth factor-beta signaling.

Gene expression profiling in R-flurbiprofen-treated prostate cancer: R-Flurbiprofen regulates prostate stem cell antigen through activation of AKT kinase

We have used gene expression profiling to characterize genes regulated by the anti-tumor non-steroidal anti-inflammatory drug (NSAID)-like agent R-flurbiprofen (RFB) in murine TRAMP prostate cancer. Mice with spontaneous, palpable tumors were treated with RFB 25 mg/(kgd) x 7d orally, or vehicle only. RNA was then extracted from tumor tissue and used for microarray analysis with Affymetrix chips. Fifty-eight genes were reproducibly regulated by RFB treatment. One of the most highly up-regulated genes was prostate stem cell antigen (psca). We used TRAMP C1 murine prostate cancer cells to examine potential mechanisms through which RFB could regulate psca. RFB induced dose-dependent expression of PSCA protein, and activity of the psca promoter, in TRAMP C1 cells in culture. Increased psca promoter activity was also seen following treatment of cells with sulindac sulfone, another NSAID-like agent, but not with celecoxib treatment. RFB activation of the psca promoter could be attenuated by co-transfection of dominant-negative akt and h-ras constructs, but not by dominant-negative mek1 plasmids. Immunoblotting revealed that RFB increased expression of phosphorylated AKT at concentrations that stimulated psca promoter activity, and that increased PSCA protein expression. In addition, RFB-dependent up-regulation of PSCA protein expression could be blocked by AKT inhibitors. These data demonstrate that RFB, and possibly other NSAID-like analogs, can increase expression of the psca gene both in vivo and in culture. They further suggest the utility of combining RFB with AKT inhibitors or with monoclonal antibodies targeting PSCA protein, for treatment or prevention of prostate cancer.

Insulin-like growth factor-1 is an endogenous mediator of focal ischemia-induced neural progenitor proliferation

The adult mammalian brain contains resident neural progenitors in the subgranular zone of the dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricles. The proliferation of neural progenitors increases after focal cerebral ischemia in both of these regions, but the mechanisms that promote ischemia-induced neural progenitor proliferation are not yet understood. We hypothesize that diffusible factors from the ischemic area play a role in this process as the DG is remote from the area of infarction. In this study, we observed that the peak of neural progenitor proliferation in the ipsilateral DG was between day 2 and day 4 of reperfusion after transient middle cerebral artery occlusion in adult spontaneously hypertensive rats. GeneChip and real-time PCR analysis showed a three- to 102-fold increase in the expression of 15 diffusible, mitogenic factors in the ischemic cortex at 3 days of reperfusion. Of these, insulin-like growth factor-1 (IGF-1) showed increased protein expression in the activated astrocytes in the ischemic penumbra. In addition, the progenitors in both the SVZ and DG showed IGF-1 receptor expression. Inhibiting IGF-1 activity by introcerebroventricular infusion of IGF-1 antibody significantly prevented the ischemia-induced neural progenitor proliferation. These results indicate that IGF-1 formed in the ischemic penumbra might be one of the diffusible factors that mediate post-ischemic neural progenitor proliferation.

Celecoxib can induce cell death independently of cyclooxygenase-2, p53, Mdm2, c-Abl and reactive oxygen species

Cell lines that do not overexpress functional cyclooxygenase-2 are resistant to the normal plasma levels of celecoxib achieved following oral ingestion. Cell growth inhibition was demonstrated after 24 h exposure to 80 micromol/l celecoxib while significant death was not detected at concentrations below 120 micromol/l following 24 h exposure. This growth inhibition and death induction was identified to be independent of p53 and Hdm2 in these cells, despite wild-type p53 stabilization and Hdm2 diminution in some lines. Cell death induced by celecoxib was preceded by the generation of reactive oxygen species within 4 h of drug exposure. The precise mechanism of elicitation of reactive oxygen species in these cells remains to be elucidated, although it was found to be independent of p53 and c-Abl, while in vitro, celecoxib enhanced superoxide radical production by xanthine oxidase. Importantly, the failure of anti-oxidants to protect from death indicates that celecoxib induces death independently of reactive oxygen species and that reactive oxygen species generation may be an insufficient trigger of death in p53-deficient cells.

Expression profiling of adrenocortical neoplasms suggests a molecular signature of malignancy

BACKGROUND

Distinguishing between adrenocortical adenomas and carcinomas is often difficult. Our aim was to investigate the differences in transcriptional profiles between benign and malignant adrenocortical neoplasms using complementary DNA microarray techniques.

METHODS

We studied 7 patients with adrenocortical carcinomas and 13 with adenomas. Histopathology was reviewed in all patients; clinical follow-up was at least 1 year. Hybridizations were performed in duplicate against RNA reference. Expression levels were analyzed in the R environment for statistical computing with the use of aroma, limma, statistics, and class packages.

RESULTS

Transcriptional profiles were homogeneous among adenomas, while carcinomas were much more heterogeneous. Hierarchical clustering and self-organizing maps could separate clearly carcinomas from adenomas. Among genes that were most significantly upregulated in carcinomas were 2 ubiquitin-related genes (USP4 and UFD1L) and several insulinlike growth factor-related genes (IGF2, IGF2R, IGFBP3 and IGFBP6). Among genes that were most significantly downregulated in carcinomas were a cytokine gene (CXCL10), several genes related to cell metabolism (RARRES2, ALDH1A1, CYBRD1 and GSTA4), and the cadherin 2 gene (CDH2).

CONCLUSIONS

Through the use of cDNA arrays, adrenocortical adenomas and carcinomas appear to be clearly distinguishable on the basis of their specific molecular signature. The biologic importance of the up- and downregulated genes is yet to be determined.

Celecoxib Inhibits Urokinase-Type Plasminogen Activator (uPA) Production in MDA-MB-231 Breast Cancer Cells

Elevated urokinase-type plasminogen activator (uPA) expression in breast tumors predicts poor survival. We found celecoxib (25 microM) significantly reduced uPA protein and mRNA in MDA-MB-231 breast cancer cells following 72 h of treatment. Celecoxib also inhibited cell viability (12.5 and 25 microM) and induced G2M arrest (25 microM). Therefore, celecoxib therapy for uPA positive breast cancer should be explored.

Sulfotransferase 2A1 forms estradiol-17-sulfate and celecoxib switches the dominant product from estradiol-3-sulfate to estradiol-17-sulfate

Using recombinant sulfotransferases (SULTs) expressed in E. coli, beta-estradiol (E2) sulfonation was examined to determine which SULT enzyme is responsible for producing E2-17-sulfate (E2-17-S). SULTs 1A1*1, 1A1*2, 1A3, 1E1 and 2A1 all sulfated E2 to varying extents. No activity was observed with SULT1B1. Among the SULTs studied, SULT2A1 produced primarily E2-3-sulfate (E2-3-S), but also some E2-17-S and trace amounts of E2 disulfate. SULT2A1 had a K(m) value of 1.52 microM for formation of E2-3-S and 2.95 microM for formation of E2-17-S. SULT2A1 had the highest V(max) of 493 pmol/min/mg protein for formation of E2-3-S, which was 8.8- and 47-fold higher than the maximal rates of formation of E2-17-S and E2 disulfate, respectively. SULT2A1 formed E2-3-S more efficiently. However, when celecoxib (0-160 microM) was included in the incubation with either SULT2A1 or human liver cytosol, sulfonation switched from E2-3-S to E2-17-S in a concentration-dependent manner. The ratio of E2-17-S/E2-3-S went up to 15 with SULT2A1, and was saturated at 1 with human liver cytosol. In both cases, more E2-17-S was formed, with the unreacted E2 remained unchanged, suggesting celecoxib probably bound to a separate effector site to cause a conformational change in SULT2A1, which favored production of E2-17-S. The ability of celecoxib to alter the position of sulfonation of E2 may in part explain its success in the experimental prevention and treatment of breast cancer.

Mechanisms underlying the growth inhibitory effects of the cyclo-oxygenase-2 inhibitor celecoxib in human breast cancer cells

INTRODUCTION

Inhibitors of cyclo-oxygenase (COX)-2 are being extensively studied as anticancer agents. In the present study we evaluated the mechanisms by which a highly selective COX-2 inhibitor, celecoxib, affects tumor growth of two differentially invasive human breast cancer cell lines.

METHODS

MDA-MB-231 (highly invasive) and MDA-MB-468 (moderately invasive) cell lines were treated with varying concentrations of celecoxib in vitro, and the effects of this agent on cell growth and angiogenesis were monitored by evaluating cell proliferation, apoptosis, cell cycle arrest, and vasculogenic mimicry. The in vitro results of MDA-MB-231 cell line were further confirmed in vivo in a mouse xenograft model.

RESULTS

The highly invasive MDA-MB-231 cells express higher levels of COX-2 than do the less invasive MDA-MB-468 cells. Celecoxib treatment inhibited COX-2 activity, indicated by prostaglandin E2 secretion, and caused significant growth arrest in both breast cancer cell lines. In the highly invasive MDA-MB-231 cells, the mechanism of celecoxib-induced growth arrest was by induction of apoptosis, associated with reduced activation of protein kinase B/Akt, and subsequent activation of caspases 3 and 7. In the less invasive MDA-MB-468 cells, growth arrest was a consequence of cell cycle arrest at the G0/G1 checkpoint. Celecoxib-induced growth inhibition was reversed by addition of exogenous prostaglandin E2 in MDA-MB-468 cells but not in MDA-MB-231 cells. Furthermore, MDA-MB-468 cells formed significantly fewer extracellular matrix associated microvascular channels in vitro than did the high COX-2 expressing MDA-MB-231 cells. Celecoxib treatment not only inhibited cell growth and vascular channel formation but also reduced vascular endothelial growth factor levels. The in vitro findings corroborated in vivo data from a mouse xenograft model in which daily administration of celecoxib significantly reduced tumor growth of MDA-MB-231 cells, which was associated with reduced vascularization and increased necrosis in the tumor mass.

CONCLUSION

The disparate molecular mechanisms of celecoxib-induced growth inhibition in human breast cancer cells depends upon the level of COX-2 expression and the invasive potential of the cell lines examined. Data suggest a role for COX-2 not only in the growth of cancer cells but also in activating the angiogenic pathway through regulating levels of vascular endothelial growth factor.