Inhibition of human colon cancer cell growth by selective inhibition of cyclooxygenase-2.

A considerable amount of evidence collected from several different experimental systems indicates that cyclooxygenase-2 (COX-2) may play a role in colorectal tumorigenesis. Large epidemiologic studies have shown a 40-50% reduction in mortality from colorectal cancer in persons taking aspirin or other nonsteroidal antiinflammatory drugs on a regular basis. One property shared by all of these drugs is their ability to inhibit COX, a key enzyme in the conversion of arachidonic acid to prostaglandins. Two isoforms of COX have been characterized, COX-1 and COX-2. COX-2 is expressed at high levels in intestinal tumors in humans and rodents. In this study, we selected two transformed human colon cancer cell lines for studies on the role of COX-2 in intestinal tumorigenesis. We evaluated HCA-7 cells which express high levels of COX-2 protein constitutively and HCT-116 cells which lack COX-2 protein. Treatment of nude mice implanted with HCA-7 cells with a selective COX-2 inhibitor (SC-58125), reduced tumor formation by 85-90%. SC-58125 also inhibited colony formation of cultured HCA-7 cells. Conversely, SC-58125 had no effect on HCT-116 implants in nude mice or colony formation in culture. Here we provide evidence that there may be a direct link between inhibition of intestinal cancer growth and selective inhibition of the COX-2 pathway.     

The growth inhibition of human breast cancer cells by a novel synthetic progestin involves the induction of transforming growth factor beta.

Recent experimental work has identified a novel intracellular binding site for the synthetic progestin, Gestodene, that appears to be uniquely expressed in human breast cancer cells. Gestodene is shown here to inhibit the growth of human breast cancer cells in a dose-dependent fashion, but has no effect on endocrine-responsive human endometrial cancer cells. Gestodene induced a 90-fold increase in the secretion of transforming growth factor-beta (TGF-beta) by T47D human breast cancer cells. Other synthetic progestins had no effect, indicating that this induction is mediated by the novel Gestodene binding site and not by the conventional progesterone receptor. Furthermore, in four breast cancer cell lines, the extent of induction of TGF-beta correlated with intracellular levels of Gestodene binding site. No induction of TGF-beta was observed with the endometrial cancer line, HECl-B, which lacks the Gestodene binding site, but which expresses high levels of progesterone receptor. The inhibition of growth of T47D cells by Gestodene is partly reversible by a polyclonal antiserum to TGF-beta. These data indicate that the growth-inhibitory action of Gestodene may be mediated in part by an autocrine induction of TGF-beta.     

基因FoxM1介导DFOG抑制人乳腺癌细胞生长和诱导凋亡的研究

目的探讨7-二氟甲氧基-5,4′-二-正辛烷氧基金雀异黄素(DFOG)对人乳腺癌细胞生长、凋亡的影响及其作用机制。方法体外培养人乳腺癌MCF-7和MDA-MB-453细胞。平皿集落形成法测定DFOG对乳腺癌细胞集落形成率的影响;碘化丙啶(PI)染色流式细胞术(FCM)检测细胞凋亡及分析细胞周期分布;Western blotting分析转录因子FoxM1及其下游蛋白CDK1、cyclin B、survivin、p27kip1表达。结果 DFOG以浓度依赖的方式抑制人乳腺癌MCF-7和MDA-MB-453细胞生长和诱导凋亡,并且伴随G2/M期细胞周期阻滞。DFOG能下调FoxM1及其下游蛋白CDK1、cyclin B、survivin表达,上调p27kip1蛋白表达。通过siRNA干扰技术下调FoxM1表达能增强DFOG对乳腺癌细胞的诱导凋亡作用。结论 DFOG显著抑制人乳腺癌MCF-7和MDA-MB-453细胞生长和诱导凋亡,下调FoxM1表达可能是其作用机制之一。     

氧化苏木素抑制人乳癌MCF-7细胞生长及其相关机制

目的:探讨氧化苏木素对人乳癌MCF-7细胞生长的抑制作用及其相关作用机制.方法:MTT实验检测氧化苏木素对乳腺癌MCF-7细胞的生长抑制;PI染色流式细胞仪检测细胞周期的变化;Western blot 实验检测细胞CD1和β-Catenin蛋白的变化.结果:氧化苏木素显著性的抑制了人乳癌MCF-7细胞的生长,将细胞周期阻滞在G1期;0、7.5、15、30 μmol/L的氧化苏木素处理MCF-7细胞48 h后,G1期在整个细胞周期中的比率从(48.10±3.48)％依次增加到(59.56±4.31)％、(70.37±3.71)％、(77.75±6.12)％;Western blot结果显示氧化苏木素下调了MCF-7细胞CD1和3-Catenin蛋白的表达.结论:氧化苏木素具有高效的抑制人乳癌MCF-7细胞增殖的活性,抑制Wnt/β-Catenin信号通路,下调CD1蛋白是其抑制细胞生长的主要机制.     

促性腺激素释放激素拮抗剂在诱导HEC-1A子宫内膜癌细胞株生长抑制中MAPK的活性

目的调查促性腺激素释放激素（GnRH）拮抗剂Cetrorelix对HEC-1A子宫内膜癌细胞株生长是否具有直接抑制作用,并探讨它的作用机制。方法应用RT-PCR法测定在子宫内膜癌细胞株促性腺激素释放激素及它的受体mRNA的表达。应用5-溴-2’-脱氧尿嘧啶核苷（5-bromo-2’-deoxyuridine,BrdU）免疫组化标记技术测定细胞增殖变化。应用Western免疫印迹技术测定与信号传导相关的丝裂原活化蛋白激酶/MAPK的蛋白水平。结果 HEC-1A细胞株表达GnRH及其受体。GnRH拮抗剂Cetrorelix在浓度10^-5mol/L下,体外作用24h后抑制了HEC-1A细胞的生长。Cetrorelix在浓度10^-6mol/L与10^-5mol/L之间作用于HEC-1A细胞6h,磷酸化丝裂原活化蛋白激酶/ERK1/2蛋白水平增长,并持续24h,这个增长被提前加入丝裂原或化蛋白激酶/MEK抑制剂U0126而阻止。而磷酸化p38、JNK蛋白水平没有变化。结论结果表明持续的ERK1/2活性在Cetrorelix抑制HEC-1A细胞生长中发挥重要作用。     

Cooperative action of tamoxifen and c-Src inhibition in preventing the growth of estrogen receptor-positive human breast cancer cells

It has long been appreciated that estrogenic signaling contributes to breast cancer progression. c-Src is also required for a number of processes involved in tumor progression and metastasis. We have previously identified the K303R mutant estrogen receptor alpha (ERalpha) that confers hypersensitivity to low levels of estrogen. Because ERalpha and c-Src have been shown to interact in a number of different systems, we wanted to evaluate the role of c-Src kinase in estrogen-stimulated growth and survival of ERalpha-positive breast cancer cells. MCF-7 cells stably expressing the mutant receptor showed increased c-Src kinase activity and c-Src tyrosine phosphorylation when compared with wild-type ERalpha-expressing cells. A c-Src inhibitor, AZD0530, was used to analyze the biological effects of pharmacologically inhibiting c-Src kinase activity. MCF-7 cells showed an anchorage-dependent growth IC50 of 0.47 micromol/L, which was increased 4-fold in the presence of estrogen. In contrast, cells stably expressing the mutant ERalpha had an elevated IC50 that was only increased 1.4-fold by estrogen stimulation. The c-Src inhibitor effectively inhibited the anchorage-independent growth of both of these cells, and estrogen was able to reverse these effects. When cells were treated with suboptimal concentrations of c-Src inhibitor and tamoxifen, synergistic inhibition was observed, suggesting a cooperative interaction between c-Src and ERalpha. These data clearly show an important role for ERalpha and estrogen signaling in c-Src-mediated breast cancer cell growth and survival. Here, we show that c-Src inhibition is blocked by estrogen signaling; thus, the therapeutic use of c-Src inhibitors may require inhibition of ERalpha in estrogen-dependent breast cancer.     

Reversible inhibition of mononuclear cell Fc receptors by sera from breast cancer patients

The number of circulating mononuclear cells (MNC) expressing Fc receptor for IgG (Fc gamma R) was evaluated in 65 breast cancer patients and 37 normal controls by EAG rosette technique. The percentage (mean +/- SD) of Fc gamma + cells in patients (15.5 +/- 7.8) was significantly decreased (p less than 0.001) when compared to controls (20.4 +/- 5.6). The MNC of patients with low basal rosette values recovered their rosetting capacity when incubated in vitro at 37 degrees C. This effect was not related to detectable immune complexes (ICs). Some of the sera of breast cancer patients were also able to reversibly inhibit the capacity to form rosettes by MNC from healthy subjects. Our data suggest that serum factor(s), different from detectable ICs, might be responsible for this inhibiting effect.     

Epidermal growth factor receptor inhibition and non-small cell lung cancer

The majority of non-small cell (NSC) lung cancers express epidermal growth factor receptor (EGFR). Many studies have evaluated the clinical effect from targeted therapy achieved by blocking EGFR in patients with NSC lung cancer. Treatment of biologically unselected patients with NSC lung cancer with two reversible quinazole EGFR inhibitors, gefitinib and erlotinib, gave negative results in all controlled trials but one. Ten percent to 20% of patients with NSC lung cancers have somatic mutations in EGFR, and these patients have a significantly higher response rate (73%) to treatment with EGFR inhibitors than patients with wild-type EGFR (10%). Patients with Asian background, women, non-smokers, and patients with adenocarcinoma had higher response rates than other patients, and the differences may be due to an association between the clinical characteristics and EGFR mutations. Further studies are needed to fully evaluate the effect of EGFR inhibitor-treatment for subgroups of patients with NSC lung cancer with favorable biological and clinical characteristics.     

Pneumocystis carinii: inhibition of lung cell growth mediated by parasite attachment.

Pneumocystis carinii pneumonia is a significant cause of mortality in immunocompromised patients. Current concepts suggest that attachment of P. carinii to alveolar epithelium is required for development of pneumonia. We examined the mechanism of P. carinii adherence to cultured A549 cells, a permanent cell line derived from human alveolar epithelium. P. carinii adherence was quantified by measuring attachment of 51Cr-labeled P. carinii to cultured A549 cells. After 8 h of incubation, 37.4 +/- 4.2% of P. carinii were adherent to A549 cells. In the presence of agents known to impair cytoskeletal function, including 10(-5) M cytochalasin B, 10(-5) M colchicine, and 10(-5) M trimethylcolchicinic acid (TMCA), adherence was decreased from 57.4 +/- 4.2% to 9.3 +/- 3.4%, 12.5 +/- 3.6%, and 21.5 +/- 3.6%, respectively (P less than 0.01, all comparisons). Secondly, we examined the effect of P. carinii on the function of A549 cells. P. carinii resulted in significant impairment of A549 cell growth, indicating P. carinii adversely affected the function of target lung cells. A P. carinii:A549 cell ratio of 50:1 resulted in 43.5 +/- 2.9% inhibition of A549 cell growth (P less than 0.001). Additionally, TMCA, which significantly prevented attachment of P. carinii, reversed the impairment of A549 cell growth. These data demonstrate that P. carinii attachment to cultured lung cells can be quantified, is dependent on intact cytoskeletal function and is necessary for impairment of lung cell replication.     

Effects of inhibition of microtubule assembly on bone mineral release and enzyme release by human breast cancer cells.

When supernates from the established human breast cancer cell line MCF-7 were applied to fetal rat long bones that had been labeled with 45Ca and devitalized to remove endogenous bone cells, mineral was released from the bones. The release of bone mineral by MCF-7 supernates was associated with increased basal release of hydrolytic enzyme activity by the tumor cells. The basal release of lysosomal enzymes and collagenolytic activity by MCF-7 cells with approximately twice that of mouse 3T3 cells, which did not cause mineral release by the fetal rat bones. Release of hydrolytic enzymes and bone mineral-releasing activity was increased by colchicine and vinblastine, drugs that inhibit microtubule assembly, but not affected by lumicolchicine. Time-course experiments performed on MCF-7 cells with or without colchicine showed that release of cathepsin D and collagenolytic activity was associated more closely with release of bone mineral and degradation of bone matrix than was the release of N-acetylglucosaminidase. The release of previously incorporated [3H]proline from the bones exposed to MCF-7 cell cultures was more closely associated with release of collagenolytic activity by MCF-7 cells than with release of cathepsin D or N-acetylglucosaminidase. These data suggest that breast cancer-mediated bone resorption in vitro is positively correlated with release of hydrolytic enzymes by the tumor cells, and release of these enzymes is enhanced by disassembly of microtubules.     

Antiintegrin alpha v beta 3 blocks human breast cancer growth and angiogenesis in human skin.

Angiogenesis plays a fundamental role in human breast tumor progression. In fact, recent findings indicate that vascular density is a prognostic indicator of breast cancer disease status. Evidence is presented that the integrin alpha v beta 3 is not only a marker of human breast tumor-associated blood vessels, but that it plays a significant role in human angiogenesis and breast tumor growth. To assess the role of alpha v beta 3-dependent angiogenesis in the progression of human breast cancer, we examined a SCID mouse/human chimeric model with transplanted full thickness human skin containing alpha v beta 3-negative human breast tumor cells. This tumor induced a human angiogenic response as measured by vascular cell immunoreactivity with monoclonal antibodies LM609 and P2B1 directed to human alpha v beta 3 and CD31, respectively. Intravenous administration of LM609 either prevented tumor growth or markedly reduced tumor cell proliferation within the microenvironment of the human skin. These LM609-treated tumors not only contained significantly fewer human blood vessels but also appeared considerably less invasive than tumors in control animals. These findings demonstrate that alpha v beta 3 antagonists may provide an effective antiangiogenic approach for the treatment of human breast cancer.     

Cyclohexylpiperazine derivative PB28, a sigma2 agonist and sigma1 antagonist receptor, inhibits cell growth, modulates P-glycoprotein, and synergizes with anthracyclines in breast cancer

sigma Ligands have recently been shown to have cytotoxic activity, to induce ceramide-dependent/caspase-independent apoptosis, and to down-regulate P-glycoprotein (P-gp) mRNA levels in some mouse and human models. In this study, we verified whether a mixed sigma(2) agonist/sigma(1) antagonist, PB28, was able to have antitumor activity and to enhance anthracycline efficacy in two human breast cancer cell lines, MCF7 and MCF7 ADR, both characterized by significant sigma(2) receptor expression, by high and low sigma(1) receptor expression, and low and high P-gp expression, respectively. In both cell lines, PB28 showed high sigma(2) receptor affinity and low sigma(1) receptor affinity; furthermore, it inhibited cell growth with a clear effect at 48 hours (IC(50) in nanomolar range), a consistent time exposure-independent increase of G(0)-G(1)-phase fraction (of approximately 20% of both cell lines) and caspase-independent apoptosis (15% increased after 1-day drug exposure). PB28 also reduced P-gp expression in a concentration- and time-dependent manner ( approximately 60% in MCF7 and 90% in MCF7 ADR). We showed also a strong synergism between PB28 and doxorubicin by adopting either simultaneous or sequential schedules of the two drugs. We suggest that this synergism could depend on PB28-induced increase of intracellular accumulation of doxorubicin ( approximately 50% in MCF7 and 75% in MCF7 ADR by flow cytometry analysis). In conclusion, we suggest that the sigma(2) agonist PB28 could be an interesting antitumor agent either in monotherapy or in combination with conventional drugs.     

Antitumor antibodies in human breast cancer sera as detected by fixed cell immunofluorescence and living cell membrane immunofluorescence assays.

The reactions of patients' sera with cultured human breast cancer cells were studied by fixed cell immunofluorescence (FCF) and living cell membrane immunofluorescence (MF) tests. The results suggested that the FCF reaction detected antibodies that were cell or organ specific, whereas the MF test was more indicative of an antineoplastic immune response.     

Identification and characterization of MEL-3, a novel AR antagonist that suppresses prostate cancer cell growth

Antiandrogens are an important component of prostate cancer therapy as the androgen receptor (AR) is the key regulator of prostate cancer growth and survival. Current AR antagonists, such as bicalutamide and hydroxyflutamide, have a low affinity for the AR and as a result block AR signaling insufficiently. Moreover, many patients develop a resistance for bicalutamide or hydroxyflutamide during therapy or show a clinical improvement after withdrawal of the antiandrogen. New and more effective AR antagonists are needed to ensure follow-up of these patients. We therefore developed a screening system to identify novel AR antagonists from a collection of compounds. MEL-3 [8-(propan-2-yl)-5,6-dihydro-4H-pyrazino[3,2,1-jk]carbazole] was selected as potent inhibitor of the AR and was further characterized in vitro. On different prostate cancer cell lines MEL-3 displayed an improved therapeutic profile compared with bicalutamide. Not only cell growth was inhibited but also the expression of androgen-regulated genes: PSA and FKBP5. Prostate cancer is often associated with mutated ARs that respond to a broadened spectrum of ligands including the current antiandrogens used in the clinic, hydroxyflutamide and bicalutamide. The activity of two mutant receptors (AR T877A and AR W741C) was shown to be reduced in presence of MEL-3, providing evidence that MEL-3 can potentially be a follow-up treatment for bicalutamide- and hydroxyflutamide-resistant patients. The mechanism of action of MEL-3 on the molecular level was further explored by comparing the structure-activity relationship of different chemical derivatives of MEL-3 with the in silico docking of MEL-3 derivatives in the binding pocket of the AR.     

In vitro mechanism of inhibition of bacterial cell growth by allicin.

Diallyl thiosulfinate (allicin) is the agent found in garlic which is responsible for the antibacterial and antifungal activity of extracts of this plant. The effect of bacteriostatic concentrations of allicin (0.2 to 0.5 mM) on the growth of Salmonella typhimurium revealed a pattern of inhibition characterized by: (i) a lag of approximately 15 min between addition of allicin and onset of inhibition, (ii) a transitory inhibition phase whose duration was proportional to allicin concentration and inversely proportional to culture density, (iii) a resumed growth phase which showed a lower rate of growth than in uninhibited controls, and (iv) an entry into stationary phase at a lower culture density. Whereas DNA and protein syntheses showed a delayed and partial inhibition by allicin, inhibition of RNA synthesis was immediate and total, suggesting that this is the primary target of allicin action.     

Steroid receptors in human breast tumorigenesis and breast cancer progression.

Steroid hormones, in particular estrogen and progesterone, play important roles in normal and neoplastic breast development. Alterations in both estrogen signaling and progesterone signaling likely occur during breast tumorigenesis and breast cancer progression. This is demonstrated by alteration of estrogen (ER) and progesterone (PR) receptor isoform expression as well as other factors such as coregulators, that can affect the activity, directly or indirectly, of in particular ER signal transduction pathways during breast tumorigenesis and breast cancer progression. A commonly emerging theme is the marked alteration of estrogen action that occurs during these processes. Since targeting ER signaling previously was successful, a better knowledge of all the molecular players involved in regulating estrogen signaling pathways and identifying changes that occur in vivo, seems critical to further exploit this previously successful approach and identify new targets for prevention and treatment of human breast cancer.