Suppression of azoxymethane-induced colon cancer development in rats by a cyclooxygenase-1 selective inhibitor, mofezolac

We demonstrated recently that mofezolac, a cyclooxygenase-1 (COX-1) selective inhibitor, suppresses the development of azoxymethane (AOM)-induced colonic aberrant crypt foci in F344 rats and intestinal polyps in APC1309 mice. In the present study, we therefore investigated the effects of mofezolac on colon cancer development. Male F344 rats were injected subcutaneously with 15 mg/kg body weight of AOM in the back twice at 7-day intervals from 5 weeks of age, and fed a diet containing 600 or 1200 ppm mofezolac for 32 weeks, starting 1 day before the first dosing of AOM. Treatment with 1200 ppm mofezolac significantly reduced the incidence, multiplicity and volume of colon carcinomas to 79%, 2.15 +/- 1.65 and 7.5 +/- 11.8 mm3, respectively, compared with 94%, 3.19 +/- 1.87 and 23.7 +/- 31.2 mm3 in the AOM treatment alone. Administration of 600 ppm mofezolac showed only a slight reduction. No side effects were observed in any of the groups. These results confirm that COX-1, as well as COX-2, contributes to colon carcinogenesis and that mofezolac may be a good chemopreventive agent for human colon cancer.     

Sequential analysis of morphological and biological properties of beta-catenin-accumulated crypts, provable premalignant lesions independent of aberrant crypt foci in rat colon carcinogenesis

Our previous study (Cancer Res., 60: 3323-3327, 2000) showed that frequent beta-catenin gene mutations are present in beta-catenin-accumulated crypts, which occur early in rodent colonic carcinogenesis, with a lack of the appearance of aberrant crypt foci (ACF). To clarify the nature of such lesions, we performed a sequential analysis of the morphological and biological properties of beta-catenin-accumulated crypts. Azoxymethane was administered s.c. to male F344 rats (15 mg/kg body weight) once a week for 3 weeks, and the animals were sacrificed at 5, 10, and 20 weeks after the carcinogen treatment. Both the number of crypts/lesion and the diameter of beta-catenin-accumulated crypts were significantly increased with time courses of 5, 10, and 20 weeks from carcinogen exposure (P < 0.01). Likewise, the histological abnormality in those crypts, assessed by semiquantitative analyses, was also increased with time (P < 0.01). Conversely, ACF did not show any increase in histological abnormality during the time course and maintained a monotonous histology throughout the experiment. The histological abnormality score for beta-catenin-accumulated crypts was significantly higher than for ACF at every time point (P < 0.001). The number of AgNOR/nucleus in beta-catenin-accumulated crypts was significantly higher than in ACF (P < 0.001). Beta-catenin-accumulated crypts were accompanied frequently by Paneth cells and had decreased hexosaminidase activity. Such data, together with the results in our previous report, strongly suggest that beta-catenin-accumulated crypts, which are independent of ACF, are truly premalignant lesions for colon cancer.     

Chemoprevention of colon cancer by specific cyclooxygenase-2 inhibitor, celecoxib, administered during different stages of carcinogenesis

Epidemiological observations and laboratory research have suggested that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colon cancer and that the inhibition of colon carcinogenesis by NSAIDs is mediated through the modulation of prostaglandin production by rate-limiting enzymes known as cyclooxygenases (COXs). Because traditional NSAIDs inhibit both COX-1 and COX-2, these drugs induce side effects, such as gastrointestinal ulceration and renal toxicity, through the inhibition of the constitutive COX-1. Overexpression of COX-2 has been observed in colon tumors; therefore, specific inhibitors of COX-2 could serve as chemopreventive agents. Our previous study has shown that celecoxib, an inhibitor of COX-2, while sparing COX-1, inhibited azoxymethane (AOM)-induced colon tumorigenesis when administered during both initiation and postinitiation stages, ie., celecoxib administered continuously before, during, and after carcinogen treatment. This study examined the dose-response effect of celecoxib when administered during the initiation and postinitiation stages. In addition, the chemopreventive effects of high-dose celecoxib administered during the promotion/progression stage of colon carcinogenesis, ie., continuous celecoxib administration beginning 14 weeks after the carcinogen treatment, was determined in male F344 rats. We also measured the steady-state levels of celecoxib in the plasma of animals given this inhibitor. Groups of 5-week-old male F344 rats were fed either a control diet or experimental diets containing 500, 1000, or 1500 ppm celecoxib. At 7 and 8 weeks of age, rats scheduled for carcinogen treatment were injected s.c. with AOM at a dose rate of 15 mg/kg body weight/week. Groups of animals destined for the promotion/ progression study and initially receiving the control diet were switched to a diet containing 1500 ppm celecoxib beginning 14 weeks after the second AOM treatment. All rats remained on their respective dietary regimens until the termination of the study, ie., 52 weeks, and were then sacrificed. Colon tumors were evaluated histopathologically. Administration of 500, 1000, or 1500 ppm celecoxib during the initiation and postinitiation stages significantly inhibited the incidence (P < 0.01 to P < 0.0001) as well as the multiplicity (P < 0.01 to P < 0.0001) of adenocarcinomas of the colon in a dose-dependent manner. Importantly, administration of 1500 ppm celecoxib during the promotion/progression stage also significantly suppressed the incidence and multiplicity of adenocarcinomas of the colon (P < 0.01). Also, administration of celecoxib to the rats during the initiation and postinitiation periods and throughout the promotion/progression stage strongly suppressed colon tumor volume (P < 0.0002 to P < 0.001). The steady-state plasma concentration of celecoxib increases somewhat with the dose. Thus, in this model system, the chemopreventive efficacy of celecoxib is dose-dependent when this COX-2 inhibitor is administered during the initiation and postinitiation periods. This study provides the first evidence that celecoxib is also very effective when it is given during the promotion/progression stage of colon carcinogenesis, indicating that the chemopreventive efficacy is achieved during the later stages of colon tumor development. This suggests that celecoxib may potentially be an effective chemopreventive agent for the secondary prevention of colon cancer in patients with familial adenomatous polyposis and sporadic polyps.     

选择性COX-2抑制剂塞来昔布预防胃癌前病变发生及其机制的研究

背景与目的:前期的动物实验表明,选择性环氧合酶(cyclooxygenase-2,COX-2)抑制剂塞来昔布可显著降低化学致癌剂N-甲基-NV-硝基-亚硝基胍(N-methyl-N5-nitro-N-nitrosoguanidine,MNNG)诱导的大鼠胃肿瘤发生率,但其对胃癌发生的重要中间阶段——胃癌前病变作用的研究甚少。本研究旨在探讨塞来昔布对胃癌前病变发生率的影响及其可能的机制。方法:94只清洁级雄性Wistar大鼠随机分为A、B、C、D、E5组。A组不作特殊处理;B组仅灌喂塞来昔布10mg/kg,每日1次;C组饮用含MNNG100!g/ml的蒸馏水;D组和E组除饮用含MNNG100!g/ml的蒸馏水外,D组灌喂塞来昔布10mg/kg每日1次,E组灌喂消炎痛3mg/kg,每日1次。实验前6周,每周一次用10%饱和氯化钠溶液1ml灌胃。16周时A、B、C、D、E组分别处死大鼠6只、8只、10只、10只、10只,其余大鼠在实验终点24周时处死。比较各组大鼠胃癌前病变发生率的差异,荧光定量PCR及免疫组化法检测胃粘膜COX-1、COX-2mRNA及蛋白水平,ELISA法测定胃粘膜PGE2水平。结果:93只大鼠完成实验,16周和24周时C、D、E组萎缩性胃炎的发生率均无显著性差异(P>0.05)。16周时各组均未见有异型增生改变;24周时C、D、E组异型增生发生率分别为75%(9/12)、25%(3/12)和46%(5/11)。与C组相比,D组异型增生发生率明显下降(P=0.039),而E组下降不显著(P=0.214)。16周、24周时各组胃粘膜COX-1表达水平均无显著性差异,C组COX-2表达水平(3.29±1.50、3.41±0.94)明显高于其他4组(P<0.001),而C组PGE2水平与D、E组相比差异无显著性(P>0.05)。结论:塞来昔布能有效降低化学致癌剂MNNG诱导的大鼠胃粘膜异型增生的发生率,而对胃粘膜组织PGE2表达水平无影响,提示这种效应可能通过非COX-2依赖途径实现。     

Chemopreventive properties of a selective inducible nitric oxide synthase inhibitor in colon carcinogenesis, administered alone or in combination with celecoxib, a selective cyclooxygenase-2 inhibitor.

The inducible isoforms of nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) are overexpressed in colonic tumors of humans, as well as in colon tumors that develop in rats after the administration of the colon-specific carcinogen, azoxymethane (AOM). iNOS may regulate COX-2 production of proinflammatory prostaglandins, which are known to play a key role in colon tumor development. Experiments were designed to assess the potential chemopreventive properties of highly selective iNOS inhibitors, administered individually and in combination with a selective COX-2 inhibitor, on the development of AOM-induced colonic aberrant crypt foci (ACF). F344 rats were fed experimental diets containing one of the following: 0, 10, 30, or 100 parts/million (ppm) of the selective iNOS inhibitor L-N(6)-(1-iminoethyl)lysine tetrazole-amide (SC-51); 1800 ppm of the less potent, selective iNOS inhibitor aminoguanidine (AG); 500 ppm of the COX-2 inhibitor celecoxib; 320 ppm of the nonsteroidal anti-inflammatory sulindac (positive control); or 30 ppm of SC-51 with 500 ppm of celecoxib, and 100 ppm of SC-51 with 500 ppm of celecoxib. One and 2 weeks later, rats received s.c. injections of AOM at a dose of 15 mg/kg of body weight. At 17 weeks of age, all rats were sacrificed. Colons were evaluated for ACF, and colonic mucosae were assayed for COX and NOS isoform enzyme activities. Samples of venous blood, collected at various time points, were analyzed for these agents. SC-51, administered alone, demonstrated dose-dependent inhibition of the incidence of colonic ACF. The highest doses of SC-51 (100 ppm) and AG (1800 ppm) significantly suppressed the incidence of colonic ACF (P < 0.01 and < 0.001, respectively) and crypt multiplicity in terms of numbers of aberrant crypts/focus (P < 0.0001). Importantly, the combination of either low or high effective doses of SC-51 (30 or 100 ppm) and celecoxib (500 ppm) suppressed AOM-induced colonic ACF formation (P < 0.05 and < 0.001, respectively) and reduced multiplicity of four or more aberrant crypts/focus (P < 0.0001) to a greater extent than did these agents administered individually. As expected, sulindac inhibited colonic ACF formation (P < 0.001) and reduced the multiplicity of four or more aberrant crypts (P < 0.0001) to approximately 45%. The enzymatic activities of COX-2 and iNOS were significantly induced in the AOM-treated animals, and administration of the iNOS inhibitors, SC-51 and AG, significantly inhibited the activities of both iNOS and COX-2 in the colonic mucosa. The combined administration of SC-51 and celecoxib inhibited the COX-2 activity to a greater extent than did either of these agents administered alone. These findings support the hypothesis that selective iNOS inhibitors may have chemopreventive properties and that coadministration with a selective COX-2 inhibitor may have additional chemopreventive potential.     

Inhibitory effect of a selective cyclooxygenase-2 inhibitor on liver metastasis of colon cancer

COX-2 overexpression is recognized in various cancers, but the role of COX-2 in the progression of cancer, including the liver metastasis of colon cancer, is not clearly understood. We examined the role of COX-2 in the mechanism of liver metastasis of colon cancer, using a highly metastasizable colon carcinoma cell line, LM-H3. A COX-2 inhibitor, JTE-522, inhibited cell proliferation and invasion of LM-H3 in vitro and clearly reduced the number of metastatic nodules on the surface of nude mouse livers in vivo. We also examined the effects of JTE-522 on the production of growth factors and MMPs through the use of ELISA and gelatin zymography, respectively. JTE-522 downregulated PDGF production by LM-H3 but had no influence on VEGF production. JTE-522 also inhibited MMP-2 secretion by LM-H3. JTE-522 downregulated PGE(2) production, but the associated changes in PGE(2) did not affect PDGF and VEGF production by LM-H3. We conclude that JTE-522 downregulated the cell proliferation and invasive potential of LM-H3 by reducing the production of PDGF and MMP-2 and hypothesize that these inhibitory effects on the production of PDGF and MMP-2 can lead to inhibition of liver metastasis of colon cancer. These data indicate that the COX-2 inhibitor JTE-522 has a high potential for use as a clinical agent for the treatment of liver metastasis of colon cancer.     

Combined treatment with selective cyclooxygenase-2 inhibitor and fluorinated pyrimidines for liver metastasis of colon cancer

Liver metastasis is a major contributor to mortality in patients with colorectal cancer. Hence, it is essential to establish preventive therapy to control liver metastasis. Recently, it has become widely accepted that cyclooxygenase (COX)-2 inhibitors possess anti-cancer activity for various types of tumor, especially colorectal. The clinical application of COX-2 inhibitors may therefore be beneficial. In this study, we have developed a combined treatment with a selective COX-2 inhibitor and fluorinated pyrimidines for liver metastasis of colorectal cancer, and examined the effect of these agents on proliferation and invasion of a highly metastatic human colon cancer cell line, LM-H3. The COX-2 inhibitor etodolac was found to inhibit cell invasion of LM-H3. 5-Fluorouracil (5-FU) inhibited proliferation of this line in vitro. Etodolac did not increase the inhibitory effect of 5-FU on cell proliferation. We also examined the inhibitory effect of etodolac and UFT, belonging to the fluorinated pyrimidines, on liver metastasis by using a liver metastatic model in the nude mouse. Combined treatment with etodolac and UFT markedly reduced liver metastasis. Serious side effects were not observed. In conclusion, combined treatment with etodolac and UFT might be a promising preventive therapy for liver metastasis of colon cancer.     

Intracranial inhibition of glioma cell growth by cyclooxygenase-2 inhibitor celecoxib

Higher cyclooxygenase-2 (COX-2) expression is clinically associated with more aggressive gliomas and is a strong predictor of poor survival. To determine whether oral administration of a COX-2-specific inhibitor can inhibit glial tumors, we analyzed the effect of celecoxib on the growth of 9L rat gliosarcoma cells that were orthotopically transplanted into rat brains. Oral administration of celecoxib beginning 1 day after implantation of 5 x 10(4) 9L rat gliosarcoma cells into rat brain reduced the incidence and size of tumors significantly. Immunohistochemical analysis of implanted gliosarcoma cells from rats treated with celecoxib showed lower levels of phospho-Akt, phospho-EGFR, Bcl-2, and Bcl-XL expression compared with untreated tumor cells. Gliosarcoma cells from treated rats had significantly more TUNEL- and caspase-3-positive cells and fewer PCNA-positive cells. These results demonstrate that selective COX-2 inhibitors may be useful as adjuvants and/or therapeutic agents to treat gliomas overexpressing COX-2.     

Chronotherapy and chronotoxicity of the cyclooxygenase-2 inhibitor, celecoxib, in athymic mice bearing human breast cancer xenografts.

PURPOSE: Inhibition of the enzyme cyclooxygenase with celecoxib is cytotoxic in a variety of solid tumor cell lines. Previous work has shown that by charting circadian rhythms, it has been possible to find optimal times to deliver a dose of drug, such that it is most efficacious in killing cancer cells and least harmful to normal tissues. Therefore, we examined the time dependence of toxicity (chronotoxicity) and of antitumor effects (chronotherapy) of celecoxib to determine optimal time of day for dosing with respect to light-dark cycles. EXPERIMENTAL DESIGN: Celecoxib was administered i.p. for 10 days (5 days on, 2 days off, 5 days on) to nude mice bearing s.c. breast xenografts. Body weight, peripheral blood cells, clinical chemistry, and tumor growth were monitored. RESULTS: The highest tolerance (100% survival) was found at 7 HALO and the least occurred at 17 h after light onset (HALO; 10% survival). Chronotherapy at a 20-mg/kg dose varied between the seven HALO evaluated and between the three breast tumors (MCF-7, ZR-75-30, and MDA-MB-468) studied. When the maximum tolerated dose (MTD) of celecoxib was optimized for each HALO, we found that at 7-10 HALO, the MTD was 25 mg/kg, whereas at 17-20 HALO; the MTD was only 10 mg/kg. Tumor regression was observed when dosing was done at 23 HALO to 7 HALO (5 a.m. to 1 p.m.), whereas no therapeutic response was observed when dosing was done at 10-13 HALO (4 p.m. to 7 p.m.), and rapid tumor growth was noted when dosing was done at 17 HALO (11 p.m.). CONCLUSIONS: Tumor growth response to the MTD at each HALO revealed that there was no clear relationship between dose administered and therapeutic response. COX-2 expression was not able to explain either the chronotherapy or the chronotoxicity results obtained.     

塞来昔布术前干预对人胃癌组织E钙粘蛋白表达的影响

背景与目的:近年来非细胞毒性药物在肿瘤治疗研究中受到关注,研究表明环氧合酶2(Cyclooxygermse-2,COX-2)抑制剂对消化道恶性肿瘤具有显著的抑制作用.本研究观察COX-2抑制剂塞来昔布对人胃癌E钙粘蛋白(E-cadherin)表达的影响,探讨其作用机制.方法:59例胃癌患者随机分为用药组37例,术前每天口服塞来昔布2次,每次200 mg,共6 d;手术组22例,单纯手术治疗.组织COX-2和E-cadherin表达采用免疫组化检测,术前、术后血清可溶性E-cadherin 浓度测定采用酶联免疫吸附试验(ELISA)法.以20名健康人作为正常对照.结果:手术组胃癌组织COX-2阳性率显著高于用药组(P<0.05).而E-cadherin阳性率显著低于用药组(P相似文献   

celecoxib抑制肝癌细胞株SMMC-7721增殖及诱导凋亡的研究

背景与目的:肝癌发病率高,治疗效果差,通过研究选择性环氧合酶-2(COX-2)抑制剂celecoxib对人肝癌细胞株SMMC-7721增殖、凋亡的影响,为治疗肝癌提供依据。方法:采用四氮唑盐比色法(MTT法)观察细胞增殖活力改变,流式细胞仪检测细胞凋亡率,透射电镜观察细胞形态改变,DNA提取行琼脂糖凝胶电泳观察DNA的"梯状"条带,免疫组化观察bcl-2基因和bax基因表达情况。结果:MTT法显示celecoxib在25、50、75、100μmol/L浓度下,24h抑制率分别为(15±3)%、(34.6±2.4)%、(56.8±1.0)%、(86.2±0.4)%,48h抑制率分别为(33.4±0.7)%、(66.7±1.8)%、(76.1±2.4)%、(97.3±0.8)%,(P<0.05);透射电镜观察到细胞凋亡的特征形态改变,如细胞体积缩小,胞膜皱缩,表面微绒毛消失,核固缩、异染色质沿核膜分布,有凋亡小体;流式细胞仪测定celecoxib组出现凋亡峰:24h50μmol/L组凋亡率分别为(14.6±1.1)%,100μmol/L组24、48h凋亡率分别为(40.5±2.0)%、(56.2±1.4)%,(P<0.01);DNA提取行琼脂糖凝胶电泳可见DNA的"梯状"条带,免疫组化显示经celecoxib干预后,bax基因表达增加,由阳性到强阳性,而bcl-2基因表达减少,由强阳性到弱阳性,并随时间和药物浓度变化而变化。结论:celecoxib抑制SMMC-7721细胞增殖,并呈剂量、时间依赖性,诱导SMMC-7721细胞凋亡,其机制之一可能是通过减少bcl-2基因的表达,而增加bax基因的表达,从而启动细胞凋亡。     

Suppressive effects of nimesulide, a selective inhibitor of cyclooxygenase-2, on azoxymethane-induced colon carcinogenesis in mice

The effects of nimesulide, a selective inhibitor of cyclooxygenase-2 (COX-2) on azoxymethane (AOM)-induced colon carcinogenesis were investigated in mice. AOM at a dose of 10 mg/kg body wt was administered to male ICR mice once a week for 6 weeks. The animals were fed on AIN-76A powder diet containing nimesulide at doses of 200 or 400 p.p.m., starting the day before the first carcinogen treatment until the end of the experiment, at week 30. Administration of nimesulide reduced the incidence of colon carcinomas to 32 and 25% for the AOM + 200 and 400 p.p.m. nimesulide groups, respectively, compared with the AOM + basal diet group (50%). Multiplicities of colon carcinomas in the 200 and 400 p.p.m. nimesulide-treated groups were 0.70 +/- 0.28 and 0.35 +/- 0.11, respectively, being significantly smaller than the AOM alone value (1.79 +/- 0.47). The sizes of the colon carcinomas in the nimesulide-treated groups were also decreased. No significant influence on liver and lung tumor development was apparent. Thus, nimesulide exerted a suppressive effect on AOM-induced colon carcinogenesis in mice.      

Effects of a selective cyclooxygenase-2 inhibitor on cancer cells in vitro

The cyclooxygenase (COX) family of enzymes has been implicated in cell proliferation and angiogenesis in many tumors, including colon cancer. Indeed, cyclooxygenase-2 (COX-2) inhibitors recently have been approved for use for prophylaxis in individuals with familial adenomatous polyposis. We now report on the effects of a selective COX-2 inhibitor, celecoxib, on cell proliferation, matrix metalloproteinase (MMP) concentration, angiogenesis using an in vitro assay, and apoptosis in several human cancer cell lines. We demonstrate that celecoxib modestly reduces proliferation in some cell lines and does not affect MMP concentrations. However, celecoxib significantly decreases microtubule formation in stimulated human umbilical vein endothelial cells (HUVECs) exposed to cancer cell supernatants, an in vitro angiogenesis model, when compared to controls incubated with supernatants from untreated cells. Celecoxib does not consistently induce apoptosis in these cell lines, as determined by DNA laddering in agarose gels and by a caspase assay. Thus, it appears that COX-2 inhibitors have beneficial effects in reducing malignant cell behavior in vitro and warrant further study to elucidate their mechanisms of action and to examine their mechanisms of action in this role and their utility in vivo in a variety of animal and human tumors.     

Inhibition of DNA repair as a mechanism of enhanced radioresponse of head and neck carcinoma cells by a selective cyclooxygenase-2 inhibitor, celecoxib

PURPOSE: Previously, we reported that inhibitors of cyclooxygenase-2 (COX-2) enzyme enhanced murine and human tumor cell response to radiation in vitro and in vivo. However, the molecular mechanisms mediating the effects of COX-2 inhibitors are not clear. The present study was designed to investigate the ability of celecoxib, a selective COX-2 inhibitor, to sensitize human head-and-neck cancer cell line, HN5, to radiation, and examine its effects on DNA repair, which may be a potential mechanism of radiosensitization. METHODS AND MATERIALS: Cells were assessed for the effect of celecoxib (5-50 microM), by 3-[4,5-dimethylthiozol-2-yl]-2,5-diphenyltetrazolium bromide assay for growth inhibition and by clonogenic cell survival assay for the radiosensitizing effect. Kinase assay and Western analysis were conducted to assess the effect of celecoxib on DNA-dependent protein kinase catalytic subunit (PKcs) and Ku proteins. Electrophoretic mobility shift assays (EMSA) were performed to determine the DNA-binding activity of Ku/DNA-PKcs protein complex and nuclear factor kappa B (NFkappaB). RESULTS: Celecoxib (10 and 50 microM, for 2 days) inhibited the HN5 cell growth and significantly enhanced the cell radiosensitivity in a dose-dependent manner. It also reduced the shoulder region on the radiation-survival curve, suggesting that inhibition of DNA repair processes may have occurred. Western blot analysis demonstrated that celecoxib downregulated the expression of Ku70 protein and inhibited the kinase activity of DNA-PKcs, which are involved in the double-stranded DNA-break repair machinery. By EMSA, it was further shown that celecoxib reduced DNA-binding activity of Ku/DNA-PKcs protein complex. In addition, celecoxib inhibited the constitutively active NFkappaB and the radiation-induced NFkappaB in HN5 cells, suggesting that NFkappaB may play a role in mediating the effects of celecoxib. CONCLUSIONS: Celecoxib strongly enhanced the sensitivity of HN5 carcinoma cells to radiation, which, mechanistically, can be attributed to the inhibition of DNA repair processes in radiation-damaged cells.     

Antiproliferative effects of selective cyclooxygenase-2 inhibitor modulated by nimotuzumab in estrogen-dependent breast cancer cells

Breast cancer is the most common malignancy in women, and many breast cancer patients fail conventional treatment strategies of chemotherapy, radiation, and antiestrogen therapy. Research into the molecular pathways and biomarkers involved in the development of breast cancer should yield information that will guide therapeutic decisions. Epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) are involved in the carcinogenesis of breast cancer and exist tight crosstalk with estrogen receptor (ER) pathway. Combination of EGFR and COX-2 inhibitors, therefore, could be an effective strategy for reducing cell growth in estrogen-dependent breast cancer. In order to verify the effects of EGFR and COX-2 inhibitors, breast cancer cells MCF-7 and SKBR-3 were characterized for receptors status and then treated with respective inhibitors (nimotuzumab and celecoxib) alone and in combination. Both cell lines were sensitive to celecoxib, but not to nimotuzumab. However, combination of two drugs demonstrated synergistic effects on cell killing. Moreover, association of two drugs resulted in SKBR-3 cells, a further G0/G1 phase arrest than one drug alone. Downregulation of p-EGFR, p-Akt, p-mTOR, and amplified in breast cancer 1 (AIB1) were observed in both cell lines, and upregulation of E-cadherin was only found in MCF-7, after treatment with single agent or in combination. These studies suggest that nimotuzumab and celecoxib exert synergistic antiproliferation effects in breast cancer, which partly correlates with ER status. Due to Akt/mTOR, EMT and AIB1 pathways participate in this process, therefore, E-cadherin and AIB1 may be considered as possible biomarkers to predict response in ER-positive breast cancer cells treated with EGFR and COX-2 inhibitors.     

Apoptosis induction and enhancement of cytotoxicity of anticancer drugs by celecoxib,a selective cyclooxygenase-2 inhibitor,in human head and neck carcinoma cell lines

Colorectal carcinomas are well known to highly express COX-2 and their growth is markedly inhibited by COX-2 inhibitors, but little is known about head and neck carcinomas. In this study, we investigated the effect of a selective COX-2 inhibitor, celecoxib, on growth and apoptosis induction of four human head and neck carcinoma cell lines, SCC25, KB, HSG and HSY, in comparison with frequently used COX inhibitor sulindac. Also, we examined whether celecoxib augments the sensitivity of these cell lines to anticancer drugs such as doxorubicin (DOX), vincristine (VCR), cisplatin (CDDP), bleomycin (BLM) and 5-fluorouracil (5-FU). The growth of all cultured cell lines particularly SCC25 and HSG was inhibited by celecoxib and sulindac in a dose-dependent manner. The IC50 of celecoxib was ten times lower than that of sulindac. SCC25 produced ample PGE2 whereas KB, HSG and HSY produced a small amount of PGE2. The PGE2 production and COX-2 expression were inhibited more efficiently by celecoxib than by sulindac. Exogenous addition of PGE2 resulted in an increased cell growth of SCC25 even under the celecoxib-treated condition, but not of HSG. These results suggested that PGE2 is involved in the growth of SCC25 but not of HSG. The ability of celecoxib to induce apoptosis is greater than that of sulindac. Treatment of SCC25 and HSG with non-cytotoxic 1 micro M or less cytotoxic 5 micro M of celecoxib enhanced the sensitivity of both cell lines to anticancer drugs, particularly in DOX, VCR and BLM two to ten times as demonstrated by lowering of IC50s. The enhanced rate was almost parallel to the degree of apoptosis induction. These findings indicated that a selective COX-2 inhibitor celecoxib inhibits cell proliferation, induces apoptosis and augments sensitivity to anticancer drugs in human head and neck carcinoma cells. Therefore, celecoxib would be useful as biological modulator in treatment of head and neck cancer.     

环氧化酶-2抑制剂对肺癌细胞的增殖抑制和放射增敏的实验研究

目的研究环氧化酶-2(COX-2)抑制剂塞来昔布对肺癌A549细胞增殖、凋亡的影响及其对A549细胞的放射增敏作用.方法噻唑蓝(MTT)比色法检测塞来昔布对肺癌A549细胞存活的影响;流式细胞分析法(FCM)检测对A549细胞周期时相影响及凋亡的作用;体外培养克隆形成率的方法检测塞来昔布对A549细胞的放射增敏作用.结果塞来昔布对肺癌A549细胞有明显的增殖抑制作用,这种抑制作用有时间和剂量依赖性,50μmol/L处理24和72 h的抑制率分别为(4.27±1.33)%、(10.63±2.23)%,100μmol/L处理分别为(33.47±8.02)%、(61.97±7.32)%,主要是抑制增殖,使细胞聚集在G0/G1期,100μmol/L处理72 h还有细胞死亡.塞来昔布无凋亡诱导作用,也不增加放射诱导的凋亡.体外培养克隆存活曲线分析显示,100μmol/L塞来昔布处理24和72 h降低了各个照射剂量点的存活分数(72 h比24 h作用强),但在照射高剂量区更明显.对照、100μmol/L处理24、72 h在2 Gy剂量点的存活分数(SF2)分别为(0.53±0.06)、(0.52±0.11)和(0.46±0.05),处理24和72 h的放射增敏比为1.27和1.7(D0值比).结论塞来昔布对肺癌A549细胞有明显的增殖抑制作用,呈时间和剂量依赖性,使细胞聚集在G0/G1期,但无诱导凋亡作用.塞来昔布对肺癌A549细胞有放射增敏作用,在高照射剂量区增敏作用更为明显.     

DNA-PKcs-dependent modulation of cellular radiosensitivity by a selective cyclooxygenase-2 inhibitor

PURPOSE: Inhibition of cyclooxygenase-2 has been shown to increase radiosensitivity. Recently, the suppression of radiation-induced DNA-dependant protein kinase (DNA-PK) activity by the selective cyclooxygenase-2 inhibitor celecoxib was reported. Given the importance of DNA-PK for repair of radiation-induced DNA double-strand breaks by nonhomologous end-joining and the clinical use of the substance, we investigated the relevance of the DNA-PK catalytic subunit (DNA-PKcs) for the modulation of cellular radiosensitivity by celecoxib. METHODS AND MATERIALS: We used a syngeneic model of Chinese hamster ovarian cell lines: AA8, possessing a wild-type DNK-PKcs; V3, lacking a functional DNA-PKcs; and V3/WT11, V3 stably transfected with the DNA-PKcs. The cells were treated with celecoxib (50 muM) for 24 h before irradiation. The modulation of radiosensitivity was determined using the colony formation assay. RESULTS: Treatment with celecoxib increased the cellular radiosensitivity in the DNA-PKcs-deficient cell line V3 with a dose-enhancement ratio of 1.3 for a surviving fraction of 0.5. In contrast, clonogenic survival was increased in DNA-PKcs wild-type-expressing AA8 cells and in V3 cells transfected with DNA-PKcs (V3/WT11). The decrease in radiosensitivity was comparable to the radiosensitization in V3 cells, with a dose-enhancement ratio of 0.76 (AA8) and 0.80 (V3/WT11) for a survival of 0.5. CONCLUSIONS: We have demonstrated a DNA-PKcs-dependent differential modulation of cellular radiosensitivity by celecoxib. These effects might be attributed to alterations in signaling cascades downstream of DNA-PK toward cell survival. These findings offer an explanation for the poor outcomes in some recently published clinical trials.     

Chemopreventive activity of celecoxib, a specific cyclooxygenase-2 inhibitor, and indomethacin against ultraviolet light-induced skin carcinogenesis.

Epidemiological and dietary studies suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colon cancer, possibly through a mechanism involving inhibition of cyclooxygenase (COX)-2, which is overexpressed in premalignant adenomatous polyps and colon cancer. Because ultraviolet light (UV) can induce COX-2 and nonspecific NSAIDs can decrease UV-induced skin cancer, we evaluated the ability of two compounds, celecoxib (a specific COX-2 inhibitor) and indomethacin (a nonspecific NSAID), to block UV-induced skin tumor development in SKH:HR-1-hrBr hairless mice. Mice fed 150 or 500 ppm celecoxib showed a dose-dependent reduction (60% and 89%, respectively) in tumor yield. Indomethacin (4ppm) reduced tumor yield by 78%. Although both acute and chronic UV exposure increased cell proliferation and edema, neither compound reduced these parameters. In contrast, UV-induced prostaglandin synthesis in the epidermis was effectively blocked by both compounds. UV-induced increases in COX-2 expression in skin were also not altered in any of the treatment groups. Similarly, tumors that constitutively express high levels of COX-2 displayed no reduction by treatment with celecoxib or indomethacin. The dramatic protective effects of celecoxib suggests that specific COX-2 inhibitors may offer a way to safely reduce the risk of skin cancer in humans.