Role of RLIP76 in lung cancer doxorubicin resistance: III. Anti-RLIP76 antibodies trigger apoptosis in lung cancer cells and synergistically increase doxorubicin cytotoxicity

RLIP76 (ral-binding protein, RalBP1) is a non-ABC multi-specific transporter of amphiphilic chemotherapeutic drugs such as doxorubicin (DOX) and glutathione-electrophile conjugates. In the present studies, we used polyclonal rabbit anti-human RLIP76 IgG to inhibit RLIP76 function for determining the role of RLIP76 in DOX resistance of NSCLC cells. Western blot analyses and immunohistochemistry studies showed no recognition of other protein in crude NSCLC cell homogenates by anti-RLIP76, confirming the specificity of anti-RLIP76 IgG. In immunohistochemistry and flow cytometry studies, these antibodies recognized RLIP76 domain(s) on the cell surface. Cells coated with anti-RLIP76 IgG accumulated significantly greater DOX than cells coated with pre-immune IgG. Synergy was calculated using the Chou-Talalay median effect analysis. Herceptin was the positive control, and pre-immune IgG and Rituxan (anti-CD20) were negative controls. The interaction of anti-RLIP76 IgG and DOX were markedly synergistic (CI 0.36+/-0.27). Lesser synergy was observed between Herceptin and DOX (CI 0.75+/-0.49). Interaction between Herceptin and anti-RLIP76 was only additive (CI 1.12+/-0.5). Human IgG, Rituxan, and rabbit pre-immune IgG controls had no effect on DOX toxicity. DNA-laddering confirmed that DOX triggered apoptosis. Anti-RLIP76 IgG alone as well as Herceptin alone also triggered apoptosis in all 6 NSCLC cell lines. Anti-RLIP76 IgG and Herceptin were shown to increase DOX accumulation in NSCLC. These results demonstrated that specific inhibition of the transport function of RLIP by anti-RLIP76 IgG can trigger apoptosis and synergistically increase DOX cytotoxicity in NSCLC.     

Amiodarone-induced enhancement of doxorubicin and 4'-deoxydoxorubicin cytotoxicity to rat colon cancer cells in vitro and in vivo

The mechanisms of the resistance of intestinal cancer to anthracyclines were studied on an experimental model of rat colon cancer cells. The accumulation of anthracyclines in the nucleus of living cancer cells was observed by fluorescence microscopy. This accumulation depended on both the capacity of anthracyclines to penetrate into the cell and the activity of an efflux mechanism extruding the drug from the cell. We found that 4'-deoxydoxorubicin was superior to 4 other anthracyclines in its capacity to penetrate into confluent colon cancer cells. Amiodarone, an antiarrhythmic agent used in cardiology, inhibited the efflux mechanism efficiently and increased the toxicity of anthracyclines to the colon cancer cells. Association of amiodarone and 4'-deoxydoxorubicin was able to cure 5 of 13 rats that had been inoculated i.p. previously with syngeneic colon cancer cells. This association could be of interest in the treatment of human colon cancer.     

DHA在人乳腺癌中对阿霉素细胞毒活性的影响与脂质过氧化作用的关系

目的　探讨廿二碳六烯酸 (DHA)影响阿霉素 (ADM)对人乳腺癌DMA MB 435s细胞毒活性的机理是否通过DHA的脂质过氧化作用。方法　在培养的人乳腺癌DMA MB 435s细胞株中加入不同配伍的细胞毒药物、多不饱和脂肪酸 (PUFAs)、前氧化剂VitC和VitK3混合物及抗氧化剂VitE等 ,在细胞的抽提物中以TBA法每 2 4小时测定脂质过氧化产物丙二醛 (MDA)及用亚硝酸盐分光光度法测定一氧化氮 (NO)的含量 ,并作出MDA、NO含量与细胞毒性间的剂量 -效应相关直线。结果　从细胞培养的第三天开始 ,出现明显的细胞活力变化 ,同时伴有脂质过氧化物 (MDA)水平的增加及NO含量的降低。细胞抽提物中MDA及NO含量与细胞毒性之间存在直线相关关系。结论　DHA能明显增加ADM对MDA MB 435s细胞株的细胞毒活性 ,机理之一是DHA增强了瘤细胞内的脂质过氧化作用。     

Insulin-like growth factor-I receptor antagonism results in increased cytotoxicity of breast cancer cells to doxorubicin and taxol

Therapeutic strategies for patients with advanced-stage adenocarcinoma of the breast frequently include the use of cytotoxic chemotherapy. Insulin-like growth factor I (IGF-I) receptor, a key factor in cell-cycle regulation, is frequently overexpressed in high-grade breast cancers. IGF-I receptor overexpression in these tumors may provide a target for novel molecular therapy against this disease. Early passage samples of estrogen-responsive (ER+) MCF 7 and estrogen receptor-negative (ER-) MDA-231 cells were cultured in semi-confluent conditions. Dose-titrations were performed for doxorubicin and taxol with receptor modulation using IGF-I or a competitive receptor inhibitor, alphaIR3. The addition of 100 ng/ml IGF-I resulted in a >2-fold mitogenic response in both ER+ and ER- cells. Receptor activation prior to the treatment with cytotoxic chemotherapeutic agents altered the pattern of response with a 26.3% increase in IC50. Doxorubicin and taxol both produced dose-related toxicity with IC50 of 0.05 microg/ml and 0.00 microg/ml respectively. The addition of alphaIR3 resulted in increased cytotoxicity in IGF-I stimulated cells compared with the use of doxorubicin or taxol alone. These results suggest that IGF-I receptor modulation alters the response to cytotoxic chemotherapeutic agents in breast cancer cells.     

Hypothermic modulation of doxorubicin, cisplatin and radiation cytotoxicity in vitro

BACKGROUND: The influence of hypothermia on doxorubicin, cisplatin and radiation cytotoxicity was investigated in vitro. MATERIALS AND METHODS: A human glioma cell line (251MG) in early exponential growth was exposed to doxorubicin or cisplatin at various concentrations for 4 hours, or X-irradiation at 28 degrees C or 37 degrees C. The cells continued growing in multi-well plates at 37 degrees C and were counted every third day until the end of the logarithmic phase, on day 13. RESULTS: Exposure to doxorubicin 0.05-0.5 microg/ml or cisplatin 1-10 microg/ml caused a dose-dependent inhibition of cell growth with a significantly reduced toxicity when exposed at 28 degrees C as compared to 37 degrees C. Irradiation with 4 Gy also resulted in less toxicity during hypothermia. Chlorpromazine 0.01-10 microg/ml, used to induce hypothermia in vivo (1), neither influenced, cellular growth itself nor interacted with doxorubicin, cisplatin or irradiation. CONCLUSION: Moderate hypothermia (28 degrees C) appears to protect against the cellular insult of doxorubicin, cisplatin and ionising irradiation and their consequences.     

Solasodine glycosides. In vitro preferential cytotoxicity for human cancer cells

Solamargine [(22R,25R)-spiro-5-en-3 beta-yl-alpha-L-rhamnopyranosyl- (1----2glu)-O-alpha-L-rhamnopyranozyl (1----4glu)-beta-D-glucopyranoze], a glycoside of solasodine preferentially inhibits the uptake of tritiated thymidine by cancer cells. In contrast, solamargine at equivalent concentration, and the mono- and diglycosides of solasodine have a limited effect on the uptake of tritiated thymidine for other cell types, including unstimulated lymphocytes and lymphocytes stimulated with Con A. In contrast the solasodine glycosides do not inhibit the uptake of tritiated thymidine by lymphocytes stimulated with PHA or PWM. The inhibition of tritiated thymidine uptake by solamargine and the mono- and di-glycosides of solasodine are dependent upon their cellular uptake by endogenous endocytic lectins (EELs). The mode of action of the solasodine glycosides, in particular solamargine, appears to be the induction of cell lysis, as determined by morphological examination.     

Expression of the hemochromatosis gene modulates the cytotoxicity of doxorubicin in breast cancer cells

The antineoplastic agent doxorubicin inhibits cell growth through mechanisms that include an interaction with iron, resulting in the generation of cytotoxic reactive oxygen species (ROS). Prior studies have shown that the wild-type hemochromatosis gene (wt HFE) may downregulate iron uptake and alter iron homeostasis in cells. We therefore tested the hypothesis that expression of wt HFE would affect the cytotoxicity of doxorubicin. Human breast cancer MCF-7 cells were transfected with an expression plasmid for a FLAG-tagged wt HFE gene [fwtHFE(+) cells], to examine the impact of wt HFE expression on doxorubicin-induced apoptosis. Our results show that, in MCF-7 cells, fwtHFE expression resulted in a reduction in cellular iron uptake and a decrease in the growth inhibitory effects of doxorubicin. Two micromolar doxorubicin inhibited the growth of fwtHFE(+) and fwtHFE(-) MCF-7 cells by 34% and 61%, respectively. In parallel, doxorubicin induced caspase-3-like activity in fwtHFE(-) cells, but not in fwtHFE(+) cells. On analysis with a DCF fluorescence assay, ROS could be detected in fwtHFE(-) cells but not in fwtHFE(+) cells exposed to doxorubicin. Western blot analysis of breast biopsy samples from patients revealed immunoreactive HFE and transferrin receptor proteins in both normal and malignant breast tissues. Our studies suggest that HFE expression and its consequent effect on cellular iron homeostasis may modulate doxorubicin-induced oxidative stress and apoptosis in breast cancer cells. Further investigation is warranted to determine whether HFE expression in tumor cells impacts on the clinical efficacy of doxorubicin.     

Role of RLIP76 in lung cancer doxorubicin resistance: I. The ATPase activity of RLIP76 correlates with doxorubicin and 4-hydroxynonenal resistance in lung cancer cells

RLIP76 functions as an ATP-dependent transporter of amphiphilic chemotherapeutic drugs such as doxorubicin (DOX, adriamycin), as well as of glutathione-conjugates of endogenous electrophilic toxins such as 4-hydroxynonenal (4HNE). RLIP76 couples transport and ATP-hydrolysis with a 1:1 stoichiometry, making the ATPase activity of RLIP76 an excellent surrogate for its transport activity. Present studies were performed to determine the relationship of the RLIP76 ATPase activity with DOX and 4HNE resistance in a panel of 13 native human lung cancer cell lines. RLIP76 was purified from each cell line and homogeneity demonstrated by SDS-PAGE and amino acid composition analysis. Anti-RLIP76 antibodies were shown by Ouchterlony double immunodiffusion tests to be non-cross-reactive with any other proteins including P-glycoprotein (Pgp) or multidrug resistance associated protein (MRP). These antibodies completely immunoprecipitated ATPase activity of purified RLIP76 fractions, further confirming homogeneity of purified RLIP76. RLIP76 ATPase purified from NSCLC cell lines was about 2-fold more active than that from SCLC in the absence of the stimulator dinitrophenyl S-glutathione (206+/-47, n=7 vs. 94+/-22, n=6, nmol/min/mg protein, respectively), or in its presence (340+/-60, n=7 vs. 186+/-32, n=6, nmol/min/mg; p<0.01). Partial tryptic digest revealed a 44 kDa internal fragment of RLIP76 beginning at Thr-294 in NSCLC cell lines. This fragment was absent from all SCLC, suggesting the possibility that the activity of RLIP76 in SCLC and NSCLC is differentially regulated through post-translational modifications. Taken together, these findings suggest that RLIP76 activity is a general determinant of 4HNE and DOX resistance, and that its activity contributes to the drug-resistant phenotype of NSCLC.     

Overexpression of ABCB4 contributes to acquired doxorubicin resistance in breast cancer cells in vitro

Purpose

Doxorubicin is one of the most active agents in the first-line therapy for metastatic breast cancer, but its utility is partially limited by the frequent emergence of doxorubicin resistance. In this study, we aimed to investigate the role of ATP-binding cassette sub-family B, member 4 (ABCB4) in acquired doxorubicin resistance in breast cancer cells, as well as its potential mechanism.

Methods

In doxorubicin-sensitive and -resistant breast cancer cell lines MCF-7 and MDA-MB-231, the expression levels of ABCB4 were detected using real-time quantitative PCR and Western blot analysis, the DNA methylation and histone acetylation status of ABCB4 gene were investigated by bisulfite-sequencing PCR (BSP) and chromatin immunoprecipitation (ChIP) assays, and the doxorubicin sensitivity and intracellular doxorubicin accumulation were observed using cell cytotoxicity assay and flow cytometry. In Madin–Darby Canine Kidney (MDCKII) cells, In vitro transport assay was used to assess the ABCB4-mediated transport of doxorubicin.

Results

ABCB4 was overexpressed in doxorubicin-resistant breast cancer cells compared to their doxorubicin-sensitive counterparts, which was associated with reduced DNA methylation as well as increased histone acetylation at the ABCB4 promoter. ABCB4 could actively pump doxorubicin out of the cells, and knockdown of ABCB4 increased doxorubicin sensitivity and intracellular accumulation in doxorubicin-resistant breast cancer cells.

Conclusions

Our results indicate that ABCB4 is overexpressed in breast cancer cells with acquired doxorubicin resistance, which could be attributed, at least partially, to the epigenetic modifications of ABCB4 gene. ABCB4 mediates the efflux transport of doxorubicin, and contributes to the acquired resistance of doxorubicin in breast cancer cells.

     

Uptake and distribution of doxorubicin in hormone-manipulated human breast cancer cells in vitro

Background: Kinetic resistance to cytotoxic drugs may account for the moderate responsiveness of breast cancer to chemotherapy. In the present study the in vitro effects of estradiol-mediated DNA stimulation on the cellular uptake of the DNA intercalating drug doxorubicin (DOX) were examined in MCF-7 human breast cancer cells. Methods: Using the fluorescent properties of the drug, the cellular uptake was investigated by high performance liquid chromatography (HPLC), and by flow cytometry. Results: The uptake of DOX (0.01–2 g/ml) by MCF-7 cells in suspension, incubated for 1 and 6 h, showed a strong correlation between the incubation concentration of DOX and the cellular uptake of the drug as measured by HPLC and flow cytometry. Simultaneous exposure of MCF-7 cells, in monolayer culture, to DOX (0.04–0.2 g/ml) and estradiol (1 nM) for 1–24 h showed no significant difference in uptake of the drug compared to control cultures exposed to DOX in the absence of estradiol. Neither was there a significant difference in uptake of DOX when MCF-7 cells were pretreated with estradiol (1 nM) for 16–24 h followed by a 0.5, 1, 6, and 21/23 h incubation with DOX (0.01–2 g/ml). Pretreatment with estradiol did not affect the retention of DOX as measured 24 h after a 0.5 h incubation with DOX (2 g/ml). Furthermore, fluorescence microscopy revealed no difference in the cellular DOX distribution pattern of estradiol-stimulated MCF-7 cultures compared to unstimulated cultures. Conclusion: From this study we can conclude that, for the human MCF-7 breast cancer cells in vitro, the uptake, retention, and cellular distribution of DOX are not influenced by estrogenic manipulation.     

Synergistic cytotoxicity of bcl-2 antisense oligodeoxynucleotides and etoposide, doxorubicin and cisplatin on small-cell lung cancer cell lines.

Expression of Bcl-2 is life-sustaining for small-cell lung cancer cells and associated with drug resistance. In the present study, the interactions between the bcl-2 antisense oligodeoxynucleotide 2009 and the chemotherapeutic agents etoposide, doxorubicin and cisplatin were investigated on small-cell lung cancer cell lines to search for synergistic combinations. The cell lines NCI-H69, SW2 and NCI-H82 express high, intermediate-high and low basal levels of Bcl-2, respectively, which are inversely correlated with the sensitivities of the cell lines to treatment with oligodeoxynucleotide 2009 and the chemotherapeutic agents alone. Moreover, differences were found in the responsiveness of the cell lines to treatment with combinations of oligodeoxynucleotide 2009 and the chemotherapeutic agents. In the cell lines NCI-H69 and SW2, all combinations resulted in synergistic cytotoxicity. In NCI-H69 cells, maximum synergy with a combination index of 0.2 was achieved with the combination of oligodeoxynucleotide 2009 and etoposide. In SW2 cells, the combination of oligodeoxynucleotide 2009 and doxorubicin was the most effective (combination index = 0.5). In the cell line NCI-H82, which expresses a low basal level of Bcl-2, most of the combinations were slightly antagonistic. Our data suggest the use of oligodeoxynucleotide 2009 in combination with chemotherapy for the treatment of small-cell lung cancer that overexpresses Bcl-2.     

负载人结肠癌Lovo细胞总RNA抗原树突状细胞对细胞因子诱导的杀伤细胞在体外特异性杀伤的影响

目的 探讨人结肠癌Lovo细胞总RNA抗原致敏的树突状细胞(DC)对细胞因子诱导的杀伤细胞(CIK)在体外特异性杀伤的影响.方法 利用Ficoll密度梯度离心法提取脐血单核细胞,分别诱导CIK和DC细胞,并用流式细胞仪检测其免疫表型.采用Trizol提取结肠癌Lovo细胞总RNA作为肿瘤细胞抗原,转染脐血来源的DC.实验分为3组:转染Lovo DC共培养CIK组、未转染DC共培养CIK组和单纯CIK组.靶细胞为Lovo细胞,在效靶比为50∶1和20∶1的条件下以噻唑蓝法分别检测CIK的体外杀伤活性.结果 在效靶比为20∶1时,负载Lovo RNA抗原的DC能诱导出CIK对Lovo细胞最强的细胞毒杀伤力为(76.49±4.21)%,DC+CIK组次之为(53.84±2.15)%,CIK组细胞毒性最低为(32.20±3.07)%,且两组间差异有统计学意义(P＜0.05).结论 肿瘤细胞总RNA提取方法简单,易于临床实施,其作为抗原致敏DC能强化CIK的特异性杀伤,将有很好的临床应用前景.     

Adenovirus-mediated gene therapy specific for small cell lung cancer cells using a Myc-Max binding motif

Recent clinical trials of gene therapy for patients with thoracic cancers have shown that these treatments were well tolerated with minimal side effects and that we need to further enhance specificity as well as efficiency of gene transfer to target cancer cells. We previously reported that myc-overexpressing SCLC cell lines became selectively sensitive to ganciclovir (GCV) by transducing the herpes simplex virus thymidine kinase (HSV-TK) gene under the control of the Myc-Max response elements (a core nucleotide sequence, CACGTG) and that this construct (MycTK) could be utilized to develop a novel treatment against chemo-radio-resistant SCLC. We report here in vivo antitumor effects and safety of a replication-deficient adenoviral vector containing the Myc-Max binding motif (AdMycTK) on SCLC cells. In vitro infection with AdMycTK selectively rendered myc-overexpressing SCLC cell lines 63- to 307-fold more sensitive to GCV. In vivo injections with AdMycTK followed by GCV administration markedly suppressed the growth of myc-overexpressing tumors established in the subcutis or in the peritoneal cavity of athymic mice. On the other hand, infection with AdMycTK did not significantly affect either in vitro GCV sensitivity of the cells expressing very low levels of the myc genes or the growth of their subcutaneous tumors. Moreover, we observed no apparent side effects of this treatment including body weight loss or biochemical abnormalities in contrast to the treatment with AdCATK that conferred strong but nonspecific expression of the HSV-TK gene. These results suggested that AdMycTK/GCV therapy is effective on SCLC patients whose tumors overexpress myc family oncogenes.     

Irinotecan-induced cytotoxicity to colon cancer cells in vitro is stimulated by pre-incubation with trifluorothymidine

SN38 is the active metabolite of the anti-cancer agent irinotecan (CPT-11) and is a potent inhibitor of topoisomerase-I (topo-I), leading to DNA strand breaks and eventually cell death. The pyrimidine analog trifluorothymidine (TFT) is part of the anti-cancer drug formulation TAS-102, which was developed to enhance the bioavailability of TFT in vivo, and is currently being evaluated as an oral chemotherapeutic agent in phase I clinical studies. In this study, the combined cytotoxic effects of dual-targeted TFT with SN38 were investigated in a panel of human colon cancer cell lines (WiDr, H630, Colo320, SNU-C4, SW1116). We used different drug combination treatment schedules of SN38 with TFT, and possible synergism was evaluated using median drug effect analysis resulting in combination indexes (CI), in which CI<0.9 indicates synergism, CI=0.9-1.1 indicates additivity and CI>1.1 indicates antagonism. Drug target analysis was performed to investigate the effect of TFT on SN38-induced DNA damage, cell cycle delay and apoptosis. Simultaneous exposure to SN38 in combination with TFT was not more than additive, whereas pre-incubation with TFT resulted in synergism with SN38 (CI=0.3-0.6). Only for Colo320 synergism could be induced for both simultaneous and sequential drug combinations. SN38 and TFT induced most DNA damage in H630 and Colo320 cells, which was increased in combination. TFT pre-incubation further enhanced SN38-induced DNA strand breaks in H630 and Colo320 (>20%), which was most pronounced in H630 cells (p<0.01). Exposure to SN38 alone induced a clear cell cycle G2M-phase arrest and pre-incubation with TFT enhanced this effect in WiDr and H630 (p<0.05). Both drugs induced significant apoptosis; SN38-induced apoptosis increased significantly in the presence of TFT (p<0.01), either when added simultaneously (about 3-fold) or at pre-incubation (about 2-fold). Topo-I protein levels varied among the cell lines and TFT hardly affected these. In conclusion, TFT pre-incubation can enhance SN38-induced cytotoxicity to colon cancer cells resulting in synergism between the drugs, thereby increasing DNA damage and apoptosis induction.     

N-hexanoyl-sphingomyelin potentiates in vitro doxorubicin cytotoxicity by enhancing its cellular influx

Anticancer drugs generally have intracellular targets, implicating transport over the plasma membrane. For amphiphilic agents, such as the anthracycline doxorubicin, this occurs by passive diffusion. We investigated whether exogenous membrane-permeable lipid analogues improve this drug influx. Combinations of drugs and lipid analogues were coadministered to cultured endothelial cells and various tumour cell lines, and subsequent drug accumulation in cells was quantified. We identified N-hexanoyl-sphingomyelin (SM) as a potent enhancer of drug uptake. Low micromolar amounts of this short-chain sphingolipid, being not toxic itself, enhanced the uptake of doxorubicin up to 300% and decreased its EC(50) toxicity values seven- to 14-fold. N-hexanoyl SM acts at the level of the plasma membrane, but was found not incorporated in (isolated) lipid rafts, and artificial disruption or elimination of raft constituents did not affect its drug uptake-enhancing effect. Further, any mechanistic role of the endocytic machinery, membrane leakage or ABC-transporter-mediated efflux could be excluded. Finally, a correlation was established between the degree of drug lipophilicity, as defined by partitioning in a two-phase octanol-water system, and the susceptibility of the drug towards the uptake-enhancing effect of the sphingolipid. A clear optimum was found for amphiphilic drugs, such as doxorubicin, epirubicin and topotecan, indicating that N-hexanoyl-SM might act by modulating the average degree of plasma membrane lipophilicity, in turn facilitating transbilayer drug diffusion. The concept of short-chain sphingolipids as amphiphilic drug potentiators provides novel opportunities for improving drug delivery technologies.     

Anti-laminin receptor antibody targeting of liposomes with encapsulated doxorubicin to human breast cancer cells in vitro

The tumor cell laminin receptor is a cell-surface protein that binds laminin with high affinity (Kd = 1.0 nM). The putative ligand-binding domain of the laminin receptor has been molecularly cloned and sequenced. In the present study, we used the predicted amino acid sequence of the laminin receptor to generate synthetic peptide antigens and produced immunoglobulin M (IgM) anti-laminin receptor monoclonal antibodies. The disulfide bond group of the IgM molecule was used to couple the antibodies to the surface of liposomes encapsulating doxorubicin. The anti-laminin receptor monoclonal antibodies coupled to the liposomes bound avidly to the surface of MDA-MB-435S (MDA-435) human breast carcinoma cells, which have high numbers of laminin receptors. These antibody-coupled liposomes exhibited a low degree of binding to Hs 578Bst (Hs 578) normal human breast epithelial cells, which express a low number of laminin receptors. Excess liposomes competed for the binding of unbound laminin to the tumor cell surface, and excess laminin competed for binding with the liposomes. Antibody-coupled liposomes encapsulating doxorubicin were specifically more efficient in inhibiting colony formation by MDA-435 cells in vitro than unbound doxorubicin or liposomes without anti-laminin receptor monoclonal antibodies. Unbound doxorubicin inhibited thymidine uptake by 10%-20% in both Hs 578 and MDA-435 cells, whereas the antibody-coupled liposomes encapsulating doxorubicin inhibited thymidine uptake by 90% in MDA-435 cells but only 15% in Hs 578 cells. Thus, use of anti-laminin receptor monoclonal antibodies coupled with liposomes encapsulating doxorubicin represents a new strategy for selective targeting of doxorubicin to carcinoma cells with exposed laminin receptors.     

Effect of exposure to calcium entry blockers on doxorubicin accumulation and cytotoxicity in multidrug-resistant cells

Flow cytometry has been used to measure doxorubicin (DOX) retention in several pairs of drug-sensitive and multidrug-resistant (MDR) cell lines and in unselected human tumor cell lines. Co-exposure to several agents that have been reported to reverse multidrug resistance, particularly calcium entry blockers (CEBs), produced a dose-dependent increase in DOX accumulation in MDR cell lines. In MDR Chinese hamster ovary cells (CHRC5), DOX levels declined rapidly following removal of CEBs, reaching a plateau value above that found in cells treated with DOX alone; this small increase probably represents DOX that is not accessible to the p170 efflux pump overexpressed in these cells. Increased DOX retention could be observed even after brief exposure to CEBs and washout and correlates with a decrease in cell proliferation over a 3-day growth assay. These results suggest that only a brief inhibition of drug efflux is sufficient to produce a meaningful reversal of drug resistance.     

Antibody-mediated transduction of p53 selectively kills cancer cells

Some human cancers are caused by functional defects in p53 that are restored by gene therapy with wild-type p53. To circumvent the use of viral vectors, we reconstituted cancer cell lines with p53 by protein transduction. A fusion protein was produced from cDNA constructed from the Fv fragment of an antibody that penetrates living cells and wild-type p53 (Fv-p53). Fv-p53 penetrated and killed cancer cells that do not express p53. Additionally, Fv-p53 killed cancer cells that were malignant as a result of mutations within p53, nuclear exclusion of p53 and over-expression of MDM2. Non-specific toxicity was excluded by showing that Fv-p53 penetrated but did not kill primary cells and cancer cells unresponsive to p53. Fv fragments alone were not cytotoxic, indicating that killing was due to transduction of p53. Fv-p53 was shown to penetrate cancer cells engrafted in vivo. These results support continued efforts to evaluate the potential efficacy of Fv-p53 for the treatment of certain cancers in vivo.     

Prolactin receptor antagonism reduces the clonogenic capacity of breast cancer cells and potentiates doxorubicin and paclitaxel cytotoxicity

Introduction

Exogenous prolactin is mitogenic and antiapoptotic in breast cancer cells, and overexpression of autocrine prolactin cDNA in breast cancer cell lines has been shown to stimulate their growth and to protect against chemotherapy-induced apoptosis. We examined the effects of the 'pure' prolactin receptor antagonist Δ1–9-G129R-hPrl (Δ1–9) on the breast cancer cell number and clonogenicity, alone and in combination with chemotherapy.

Methods

The effects of doxorubicin, paclitaxel and Δ1–9 on the growth of breast cancer cell lines (MCF-7, T47D, MDA-MB-453, MDA-MB-468 and SK-BR-3) in monolayer culture were assessed by the sulphorhodamine B assay. Effects on clonogenicity were assessed by soft agar assay for the cell lines and by the mammosphere assay for disaggregated primary ductal carcinoma in situ samples. Dual-fluorescence immunocytochemistry was used to identify subpopulations of cells expressing the prolactin receptor and autocrine prolactin.

Results

Δ1–9 as a single agent had no effect on the cell number in monolayer culture, but potentiated the cytotoxic effects of doxorubicin and paclitaxel. Doxorubicin accordingly induced expression of prolactin mRNA and protein in all five breast cancer cell lines tested. Δ1–9 alone inhibited the clonogenicity in soft agar of cell lines by ~90% and the mammosphere forming efficiency of six disaggregated primary ductal carcinoma in situ samples by a median of 56% (range 32% to 88%). Subpopulations of cells could be identified in the cell lines based on the prolactin receptor and prolactin expression.

Conclusion

Autocrine prolactin appears to act as an inducible survival factor in a clonogenic subpopulation of breast cancer cells. The rational combination of cytotoxics and Δ1–9 may therefore improve outcomes in breast cancer therapy by targeting this cell population.     

CD137单抗联合IL-15体外扩增NK细胞及其对肺癌细胞的杀伤活性

目的:建立CD137单抗联合IL-15体外扩增NK细胞的方案,研究扩增后NK细胞对肺癌细胞的杀伤活性。方法:分离健康人外周血单个核细胞,经免疫磁珠阴性分选获取CD3-CD56+NK细胞,将NK细胞分成对照组、IL-2组、IL-2+CD137单抗组、IL-2+IL-15组、IL-2+CD137单抗+IL-15组进行培养,经锥虫蓝染色法计算NK细胞的扩增倍数,流式细胞术检测NK细胞的表型,LDH酶释放法检测NK细胞对肺癌细胞株A549的杀伤活性,ELISA法检测扩增后NK细胞培养液上清中IFN-γ的分泌量。结果:经磁珠分选后NK细胞纯度为(93.28±3.21)%。IL-2+CD137单抗+IL-15组NK细胞扩增倍数明显高于IL-2+CD137单抗组、IL-2+IL-15组、IL-2组及对照组[(86.20±5.00)vs(60.01±5.00)、(49.06±4.39)、(17.04±1.49)、(3.95+0.23)倍,P<0.01]。IL-2+CD137单抗+IL-15组NK细胞对A549细胞的杀伤效率明显高于其他各组[(93.14±3.27)%vs(83.15±4.03)%、(71.25±3.24)%、(62.27±3.01)%、(49.38±2.35)%,P<0.01]。IL-2+CD137单抗+IL-15组培养液上清中的IFN-γ的分泌水平明显高于IL-2+CD137单抗组、IL-2+IL-15组、IL-2组及对照组[(296.25±9.79)vs(260.47±11.55)、(201.13±6.36)、(138.36±6.09)、(38.42±3.56)pg/ml,P<0.01]。结论:CD137单抗联合IL-15能高效扩增NK细胞,扩增的NK细胞高效杀伤A549肺癌细胞。