Multidrug resistance in a small cell lung cancer line: rapid selection with etoposide and differential chemosensitization with cyclosporin A.

We developed a multidrug resistant small cell lung cancer line, VPR-2, by exposing H69 parent cells to etoposide (20 microM) for 1 h daily for 3 days every 21-28 days, a schedule similar to that used in the clinic. Resistance (20-fold) to the cytostatic and DNA cleavage activities of etoposide emerged after the third treatment, and this phenotype was stable in the absence of drug exposure for 2.5 years. VPR-2 cells exhibited cross resistance to intercalating agents and vinca alkaloids, but remained sensitive to X-radiation, cisplatin and 5-fluorouracil. The human mdr1 gene was overexpressed in the resistant line, but steady-state concentrations of etoposide were reduced only 1.5-fold. Topoisomerase II catalytic and etoposide stimulated DNA cleavage activity in nuclear extracts from both lines were identical despite retention of a 3-fold level of resistance to etoposide-induced strand breaks in isolated nuclei from VPR-2 cells. Cyclosporin A and verapamil, both of which bind to P-glycoprotein, enhanced accumulation of etoposide in VPR-2 cells, and H69 cells to a lesser extent. Yet only cyclosporin A was effective in differentially enhancing etoposide cytostasis in VPR-2 relative to H69. In VPR-2 whole cells, cyclosporin A enhanced etoposide-induced DNA single-strand break frequency 9-fold but had no effect in isolated nuclei. Rapid selection of this line with a clinically relevant drug exposure schema and stability of the resistant phenotype suggest these cells may have been a steady subpopulation of the parent line through years of serial passage in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biochemical changes associated with a multidrug-resistant phenotype of a human glioma cell line with temozolomide-acquired resistance

Temozolomide (TMZ) is a newly approved alkylating agent for the treatment of malignant gliomas. To investigate resistance mechanisms in a multidrug therapeutic approach, a TMZ-resistant human glioma cell line, SF188/TR, was established by stepwise exposure of human SF188 parental cells to TMZ for approximately 6 months. SF188/TR showed 6-fold resistance to TMZ and cross-resistance to a broad spectrum of other anticancer agents that included 3-5-fold resistance to melphalan (MEL), gemcitabine (GEM), paclitaxel (PAC), methotrexate (MTX), and doxorubicin (DOX), and 1.6-2-fold resistance to cisplatin (CDDP) and topotecan (TPT). Alkylguanine alkyltransferase (AGT) activity was increased significantly in the resistant cell line compared with the parental cell line (P<0.05), whereas no significant differences occurred in the cellular uptake of TMZ and PAC between resistant and parental cells. Depletion of AGT by O(6)-benzylguanine significantly increased the cytotoxicity of TMZ in both the sensitive and resistant cell lines, but did not influence the cytotoxicity of the other drugs tested. Treatment with TMZ caused SF188 cells to accumulate in S phase, whereas SF188/TR cells were unaffected. Expression of Bcl-2 family members in SF188/TR cells compared with SF188 cells indicated that the pro-apoptotic proteins (i.e. Bad, Bax, Bcl-X(S)) were reduced 2-4-fold in the resistant cell line, whereas the anti-apoptotic proteins Bcl-2 and Bcl-X(L) were expressed at similar levels in both cell lines. In conclusion, the mechanism of resistance of SF188/TR cells to TMZ involved increased activity of AGT, a primary resistance mechanism, whereas the broad cross-resistance pattern to other anticancer drugs was due to a common secondary resistance mechanism related to alterations in the relative expression of the pro-apoptotic and anti-apoptotic proteins.     

抗阿霉素的中国仓鼠卵巢上皮细胞系的抗药性

用细胞生物学和SDS-PAGE电泳方法,研究抗阿霉素(Dox)CHO细胞系(RCl)的特性。用间接免疫荧光法,未测到RCl超表达P-糖蛋白。RCl降低Dox的摄入,增加膜的流动性,Dox在CHO中主要分布在细胞核,在RCl中则分布在细胞质和细胞核。RCl中有一种分子质量为30—40 kDa的核蛋白的表达被抑制,而在敏感CHO中其表达正常。     

耐阿霉素人骨肉瘤细胞株的建立及其耐药机制探讨

目的诱导并建立耐阿霉素(ADM)的人骨肉瘤细胞株并探讨其耐药机制。方法采用逐步增加药物剂量冲击诱导方法诱导人成骨肉瘤原代Saos-2细胞株;MTT法检测原代与耐药细胞株对ADM、顺铂(DDP)、甲氨蝶呤(MTX)、异环磷酰胺(IFO)、表柔比星(EPI)、比柔比星(THP)、紫杉醇(Paclitaxel,PTX)药物敏感性;利用光学显微镜、透射电镜观察细胞形态及超微结构变化;RT-PCR和IHC法分别检测多药耐药基因1(MDR1)、多药耐药相关蛋白(MRP)基因及其相应蛋白(P-gp)、MRP的表达。结果经167d的诱导,建立Saos-2/ADM1、Saos-2/ADM4细胞株,其对ADM的耐药指数分别为原代细胞株的49.8和74.6倍;耐药细胞株对MTX、EPI、THP、PTX亦产生不同程度的交叉耐药(P<0.05),对DDP仍然敏感(P>0.05);光镜观察Saos-2/ADM1、Saos-2/ADM4细胞株细胞体积增大,多核现象较原代Saos-2细胞株明显增加;透射电镜显示Saos-2/ADM1、Saos-2/ADM4细胞株表面突起较原代Saos-2细胞株减少、且核仁增大增多;细胞生长曲线显示耐药细胞株增殖能力下降。MDR1mRNA、MRPmRNA和P-gp、MRP在各耐药细胞株表达阳性。结论MDR1 mRNA、MRP mRNA及其相应蛋白参与了耐药细胞株耐药的形成,这些骨肉瘤耐药细胞株为进一步研究骨肉瘤耐药特征及逆转方法打下了基础。     

阿霉素诱导的人白血病细胞系K562/A02多药抗药性(英文)

目的:研究白血病细胞多药耐药发生的机制. 方法:用逐步增加培养基中阿霉素(Dox)浓度的方法,诱导出一株耐Dox的人白血病细胞系K562/A02.用[~3H]TdR参入法测定IC_(50),HPLC法测定细胞内药物浓度,免疫组织化学法检测P-糖蛋白的表达,RT-PCR法测定mdr1基因表达,点杂交测定基因组中mdr1DNA和拓扑异构酶Ⅱ(TopⅡ)基因表达,CDNB法测定谷胱甘肽-S-转移酶(GST)活性. 结果:K562/A02对Dox、HHT、Dau、VCR、m-AMSA、VP-16具有较强的交叉耐药性,而对Ara-C耐药较弱,对5-FU、Cis和MTX不交叉耐药,表现出典型的多药耐药表型.K562/A02细胞内药物浓度明显低于K562细胞,P-170阳性表达.K562/A02细胞中MDR1基因拷贝数与K562的无差异,但mdr1mRNA高表达.TopⅡ的mRNA水平低于K562,GST的活性增高. 结论:白血病细胞多药耐药的机制与mdr1基因表达密切相关,也与TopⅡ和GST有关.     

粉防己碱逆转肿瘤多药抗药性细胞的凋亡抗性作用

目的探讨粉防己碱逆转ＭＤＲ细胞凋亡抗性的作用及其机制。方法ＭＤＲ细胞株ＭＣＦ－７／Ａｄｒ与其相应的敏感株ＭＣＦ－７进行对比研究。比较粉防己碱对阿霉素（Ｄｏｘ）诱导ＭＤＲ细胞及其相应的敏感株的凋亡作用。并比较粉防己碱对ＭＤＲ细胞及其相应的敏感株的细胞ｂｃｌ－２蛋白的表达的影响。细胞凋亡及ｂｃｌ－２蛋白表达的测定以流式细胞仪法。结果加入Ｄｏｘ共同培养２４ｈ可诱导７４．６％ＭＣＦ－７细胞凋亡，而只引起１４．３％的ＭＣＦ－７／Ａｄｒ细胞凋亡。只加入粉防己碱共同培养２４ｈ，未见明显增加ＭＤＲ细胞及其相应敏感细胞的凋亡百分比。Ｄｏｘ＋粉防己碱能显著地使ＭＤＲ细胞的凋亡增至４７．０％，与单独用Ｄｏｘ组相比较，差异有显著性（Ｐ＜０．０１），而敏感细胞株为７７．８％，与单独用Ｄｏｘ组相比较，差异无显著性（Ｐ＞０．０５）。ＭＤＲ细胞株与其相应的敏感株ｂｃｌ－２蛋白表达水平均较低且差异无显著性。加入粉防己碱对ＭＤＲ细胞株与其相应的敏感株ｂｃｌ－２蛋白表达水平均未见明显影响。结论粉防己碱能逆转ＭＤＲ细胞对Ｄｏｘ的凋亡抗性。其逆转机制可能与ｂｃｌ－２蛋白表达无关。粉防己碱逆转ＭＤＲ细胞ＭＣＲ－７／ＡＤＲ对Ｄｏｘ的凋亡抗性的机制有待进?     

细胞粘附在结肠癌细胞系SW480多药耐药表型中的作用

目的探讨细胞粘附在结肠癌细胞系SW 480多药耐药表型中的作用。方法通过细胞粘附实验、四甲基偶氮唑盐实验（MTT法）、细胞内阿霉素的蓄积和潴留及Annexin V/PI染色法检测凋亡等检测粘附于层粘连蛋白（LN）的结肠癌细胞系SW 480的多药耐药性的改变。结果粘附于LN的SW 480细胞对化疗药物敏感性显著下降,化疗药物的IC50均显著升高,化疗药物诱导的凋亡指数明显减少 细胞内阿霉素的蓄积和潴留均明显减少,药物泵出率显著增加（P〈0.05）。结论结肠癌细胞SW 480与LN粘附后,可能提高了对药物转运的能力,导致化疗药物在肿瘤细胞内蓄积的减少 通过提高抗凋亡的能力,逃避化疗药物诱导的凋亡。     

Increased drug resistance is associated with reduced glucose levels and an enhanced glycolysis phenotype

BACKGROUND AND PURPOSE

The testing of anticancer compounds in vitro is usually performed in hyperglycaemic cell cultures, although many tumours and their in vivo microenvironments are hypoglycaemic. Here, we have assessed, in cultures of tumour cells, the effects of reduced glucose levels on resistance to anticancer drugs and investigated the underlying cellular mechanisms.

EXPERIMENTAL APPROACH

PIK3CA mutant (AGS, HGC27), and wild-type (MKN45, NUGC4) gastric cancer cells were cultured in high-glucose (HG, 25 mM) or low-glucose (LG, 5 mM) media and tested for sensitivity to two cytotoxic compounds, 5-fluorouracil (5-FU) and carboplatin, the PI3K/mTOR inhibitor, PI103 and the mTOR inhibitor, Ku-0063794.

KEY RESULTS

All cells had increased resistance to 5-FU and carboplatin when cultured in LG compared with HG conditions despite having similar growth and cell cycle characteristics. On treatment with PI103 or Ku-0063794, only the PIK3CA mutant cells displayed increased resistance in LG conditions. The PIK3CA mutant LG cells had selectively increased p-mTOR, p-S6, p-4EBP1, GLUT1 and lactate production, and reduced reactive oxygen species, consistent with increased glycolysis. Combination analysis indicated PI103 and Ku-0063794 were synergistic in PIK3CA mutant LG cells only. Synergism was accompanied by reduced mTOR signalling and increased autophagy.

CONCLUSIONS AND IMPLICATIONS

Hypoglycaemia increased resistance to cytotoxic agents, especially in tumour cells with a high dependence on glycolysis. Dual inhibition of the PI3K/mTOR pathway may be able to attenuate such hypoglycaemia-associated resistance.     

穿琥宁对大肠癌HCT-8/5-FU耐药细胞株逆转作用的研究

目的:探讨中药制剂穿琥宁对HCT-8/5-FU多药耐药细胞株的影响.方法:观察0.4,1.2和2.4mg·mL-1穿琥宁作用下的HCT-8/5-FU多药耐药细胞株生长曲线,MTT法检测上述浓度下的细胞抑制率.MTT法、流式细胞仪PI染色法检测穿琥宁与化疗药物5-氟尿嘧啶(5-FU)、顺铂(DDP)和阿霉素(ADM)联合作用下,对HCT-8/5-FU耐药细胞的毒性作用和凋亡率.流式细胞仪罗丹明染色法和PI染色法探讨穿琥宁的作用机制.结果:0.4mg·mL-1穿琥宁生长曲线与正常对照组无明显差别,1.2mg·mL-1穿琥宁对细胞生长有轻度抑制作用,2.4mg·mL-1浓度有一定抑制,但细胞仍可生长.MTT法检测0.4,1.2,2.4mg·mL-1穿琥宁作用下,HCT-8/5-FU耐药细胞株的抑制率分别为7.2%,13.2%,21%.1.2mg·mL-1穿琥宁与5-FU,DDP,AMD联合作用,与这3种化疗药物单独作用比较细胞凋亡率分别为54.2%/26.4%;42.6%/13.6%;30.8%/14.2%,差异显著(P<0.01).罗丹明染色法提示穿琥宁的作用机制可能与影响P-170的活性有关.但穿琥宁本身并不诱导凋亡,对细胞周期也无影响.结论:低浓度穿琥宁对HCT-8/5-FU细胞无明显抑制作用;与5-FU,ADM,DDP联合作用,可增加上述化疗药物的毒性作用,使肿瘤细胞的凋亡率增高,其机制可能与抑制P-170功能有关.     

Induction of deoxycytidine kinase by 5-azacytidine in an HL-60 cell line resistant to arabinosylcytosine.

Induction of 2'-deoxycytidine kinase (dCK) by 5-azacytidine (5-Aza-C) in a dCK-deficient HL-60 cell line resistant to 1-beta-D-arabinofuranosylcytosine (Ara-C) (HL-60/Ara-C) was examined by measurement of the incorporation of [3H]deoxycytidine ([3H] dCyd) into cellular DNA, the kinetic properties of purified dCK, the cytotoxic potency (IC50 values), and the DNA methylation patterns of 5-Aza-C-treated and untreated cells. Following a 72-hr exposure to 1 microM 5-Aza-C, the incorporation of [3H]dCyd into DNA was increased 6-fold and the total dCK activity was increased 12-fold, with a peak for both on day 6. The onset of dCK induction was dependent on the length of exposure time. The IC50 values for cell growth inhibition by Ara-C on day 3 were 0.08 microM for HL-60 cells, 12.5 microM for HL-60/Ara-C cells, and 0.55 microM for HL-60/Ara-C cells pretreated with 5-Aza-C for 40 hr. The Km and Vmax of dCyd for HL-60 dCK were similar to those for 5-Aza-C-induced HL-60/Ara-C dCK. The restriction enzymes Hpall, which cleaves CCGG sequences but cannot cleave at sites methylated at the internal cytosines (5'-CMeCGG), and Mspl, which cleaves sequences with internal methylated cytosine but cannot cleave at sites methylated at external cytosines (5'-MeCCGG), were used for DNA methylation pattern determination. The newly synthesized DNA of HL-60 wild-type cells was cleaved by Mspl to a greater extent than that of HL-60/Ara-C cells. After exposure to 1 microM 5-Aza-C for 40 hr, methylation patterns of newly synthesized DNA reverted in HL-60/Ara-C cells to a clevage pattern similar to that in HL-60 wild-type cells. When compared with untreated control, DNAs from 5-Aza-C-treated resistant cells were cleaved to a greater extent by Mspl than by Hpall, suggesting that internal cytosine-residue methylation was relatively uninhibited.(ABSTRACT TRUNCATED AT 250 WORDS)     

氟哌啶醇对人红白血病耐多柔比星细胞株多药耐药性的逆转及其机制

目的　从临床常用药物中探寻逆转肿瘤耐药性的活性物质。方法　应用MTT法测定不同浓度Hal处理的瘤细胞对 0～ 2 0 μmol·L- 1多柔比星 (Dox)的敏感性的影响。RT PCR法分析 12 .5 μmol·L- 1氟哌啶醇 (Hal)处理后多药耐药基因 (MDR1) ,多药耐药相关蛋白 (MRP)和谷胱甘肽S转移酶Pi(GSTπ)mRNA表达的变化。通过流式细胞术观察 0 ,6 .2 5 ,12 .5 ,2 5 μmol·L- 1Hal对细胞内药物蓄积和细胞周期进程的影响。结果　Hal对K5 6 2 /Dox的耐药性具有明显的逆转作用。在 12 .5 ,6 .2 5及 3.12 5 μmol·L- 1时的逆转倍数分别为 8.35 ,4 .2 1及 2 .16。用 12 .5μmol·L- 1Hal处理后 ,MDR1及MRP的mRNA表达水平均呈现时间依赖性明显降低 ,分别较原水平下降76 .3%及 6 4.6 %。药后d 2GSTπmRNA表达下降6 6 .1% ,于d 3回升。Hal处理细胞lh后 ,Dox在细胞内蓄积量明显增加 ,并呈浓度依赖性 ;此外 ,Hal可明显增强Dox对K5 6 2 /Dox细胞的G2 /M阻滞作用 ,12 .5 μmol·L- 1浓度可以使 5 μmol·L- 1Dox的G2 /M阻断由单独应用时的 9.9%± 4 .3%增加到2 3.4 %± 3.0 %。结论　Hal具有较强的逆转K5 6 2 /Dox细胞MDR的作用 ,其逆转机制为多种途径 ,包括相关基因mRNA的表达下调 ,增加细胞内药物蓄积 ,增强Dox对K5 6 2 /Dox在G2     

Effect of curcumin on multidrug resistance in resistant human gastric carcinoma cell line SGC7901/VCR

AIM: To investigate the reversal effects of curcumin on multidrug resistance (MDR) in a resistant human gastric carcinoma cell line. METHODS: The cytotoxic effect of vincristine (VCR) was evaluated by MTT assay. The cell apoptosis induced by VCR was determined by propidium iodide (PI)-stained flow cytometry (FCM) and a morphological assay using acridine orange (AO)/ethidium bromide (EB) dual staining. P-glycoprotein (P-gp) function was demonstrated by the accumulation and efflux of rhodamine123 (Rh123) using FCM. The expression of P-gp and the activation of caspase-3 were measured by FCM using fluorescein isothiocyanate (FITC)-conjugated anti-P-gp and anti-cleaved caspase-3 antibodies, respectively. RESULTS: Curcumin, at concentrations of 5 micromol/L, 10 micromol/L, or 20 micromol/L, had no cytotoxic effect on a parent human gastric carcinoma cell line (SGC7901) or its VCR-resistant variant cell line (SGC7901/VCR). The VCR-IC50 value of the SGC7901/VCR cells was 45 times more than that of the SGC7901cells and the SGC7901/VCR cells showed apoptotic resistance to VCR. SGC7901/VCR cells treated with 5 micromol/L, 10 micromol/L, or 20 micromol/L curcumin decreased the IC50 value of VCR and promoted VCR-mediated apoptosis in a dose-dependent manner. Curcumin (10 micromol/L) increased Rh123 accumulation and inhibited the efflux of Rh123 in SGC7901/VCR cells, but did not change the accumulation and efflux of Rh123 in SGC7901 cells. P-gp was overexpressed in SGC7901/VCR cells, whereas it was downregulated after a 24-h treatment with curcumin (10 micromol/L). Resistant cells treated with 1 mumol/L VCR alone showed 77% lower levels of caspase-3 activation relative to SGC7901 cells, but the activation of caspase-3 in the resistant cell line increased by 44% when cells were treated with VCR in combination with curcumin. CONCLUSION: Curcumin can reverse the MDR of the human gastric carcinoma SGC7901/VCR cell line. This might be associated with decreased P-gp function and expression, and the promotion of caspase-3 activation in MDR cells.     

酪氨酸激酶抑制剂伊马替尼耐药K562细胞系的建立及其耐药特征

目的建立酪氨酸激酶抑制剂伊马替尼(STI-571)耐药K562细胞系并研究其耐药特征。方法采用含递增浓度伊马替尼的培养基培养K562细胞,诱导耐伊马替尼K562细胞系(K562R)。通过细胞生长曲线、细胞形态和细胞凋亡分析确定耐药细胞是否形成;采用MTT法观察耐药细胞的耐药谱;通过半定量PCR和Western印迹法检测相关基因及蛋白的表达,并通过基因测序分析K562R细胞B细胞受体-c-Abelson(BCR-ABL)激酶区基因序列。结果成功地将伊马替尼高敏感的K562细胞诱导成K562R,伊马替尼抑制K562和K562R细胞存活的IC50值分别为0.01±0.00和(2.35±0.01)μmol·L-1,耐药倍数为235.0倍。K562R具有一定的交叉耐药性,对高三尖杉酯碱、长春新碱和对柔红霉素的耐药倍数分别为13.2,63.2和11.8倍。K562R可对抗伊马替尼诱导的细胞凋亡,伊马替尼1.0μmol·L-1培养24 h K562和K562R细胞凋亡率分别为72.1%和18.2%。耐药形成机制研究表明,与K562细胞相比,K562R细胞BCR-ABL基因、多药耐药基因(MDR)和p-糖蛋白基因(p-GP)的表达均明显增加。此外,K562R细胞BCR-ABL基因的第696位发生A→C点突变,该位点突变导致激酶区第231位氨基酸由赖氨酸取代原有的天冬酰胺。结论成功建立了耐伊马替尼细胞系K562R。K562R细胞具有交叉耐药性和对抗伊马替尼诱导的细胞凋亡等特征。K562R细胞BCR-ABL基因序列发生点突变,MDR和p-GP等基因表达亦明显升高。     

Multidrug resistance associated proteins as determining factors of pharmacokinetics and pharmacodynamics of drugs

The multidrug resistance associated proteins (MRP1, MRP2, MRP3, MRP4, MRP5, MRP6, MRP7, MRP8 and MRP9) belong to the ATP-binding cassette superfamily (ABCC family) of transporters. They are expressed differentially in the liver, kidney, intestine, brain and other tissues. These transporters are localized to the apical and/or basolateral membrane of the hepatocytes, enterocytes, renal proximal tubule cells and endothelial cells of the blood-brain barrier. Several MRPs (mainly MRP1-3) are associated with tumor resistance which is often caused by an increased efflux and decreased intracellular accumulation of natural product anticancer drugs and other anticancer agents. MRPs transport a structurally diverse array of important endogenous substances and xenobiotics and their metabolites (in particular conjugates) with different substrate specificity and transport kinetics. Most MRPs are subject to induction and inhibition by a variety of compounds. Several nuclear receptors, including pregnane X receptor (PXR), liver X receptor (LXR), and farnesoid receptor (FXR) participate in the regulation of MRPs. MRPs play an important role in the absorption, distribution and elimination of various drugs in the body and thus may affect their efficacy and toxicity and cause drug-drug interactions. MRPs located in the blood-brain barrier can restrict the penetration of compounds into the central nervous system. Mutation of MRP2 causes Dubin-Johnson syndrome, while mutations in MRP6 are responsible for pseudoxanthoma elasticum. More recently, mutations in mouse Mrp6/Abcc6 gene is associated with dystrophic cardiac calcification (DCC), a disease characterized by hydroxyapatite deposition in necrotic myocytes. A single nucleotide polymorphism, 538G>A in the MRP8/ABCC11 gene, is responsible for determination of earwax type. A better understanding of the function and regulating mechanism of MRPs can help minimize and avoid drug toxicity, unfavourable drug-drug interactions, and to overcome drug resistance.     

Increased expression of p27 is associated with the cisplatin resistance in gastric cancer cell line YCC-3

The major obstacle of treating cancer patients is acquisition of chemoresistance, in which treated tumor cells become insensitive after chronic drug exposure. To study the mechanism of acquired cisplatin resistance, we established a cisplatin-resistant human gastric cancer cell line. The cisplatin-resistant cell line (YCC-3/R) was isolated after exposing the gastric cancer cell line, YCC-3, to a constant concentration (0.5 μg/mL) of cisplatin for 12 months. The expression of cell cycle regulatory proteins (p53, Bax, p21, p27) in the YCC-3/R were investigated by western blot analysis. The cisplatin treatment significantly down-regulated the p53 and p21 expression level, while up-regulated the p27 expression in the YCC-3/R cells compared to the parental cells. The Bax expression level was similar in both cells. These results suggest that the p27 dependent-cell cycle arrest may prevent cisplatin-induced apoptosis and give enough time to repair the DNA damage in the YCC-3/R cells.     

Survival response of a human glioma cell line to hyperthermia associated with rhein.

The effect of association of hyperthermia with the anti-inflammatory drug rhein (RH), 4,5-dihydroxyanthraquinone-2-carboxylic acid, on the clonogenic activity of human glioma cells has been examined. RH inhibits neoplastic growth mainly through an ATP depletion, but thermal cell killing is not mediated by the drug-induced changes in the energy status of the cell. The analysis of the interaction between RH and hyperthermia, performed with the isobolar method, demonstrates an additivity of the response so that the effectiveness of the combined treatment is the result of two independent effects. Although the effect of this combination is purely additive, RH allows us to achieve a pre-established cell killing with exposure times at 42 degrees C, which is generally accepted to be clinically achievable. RH might, therefore, be employed to reduce the side effects of hyperthermia without impairing its therapeutic effectiveness.     

本芴醇衍生物LY980503逆转人乳腺癌多药耐药细胞株MCF/DOX对多柔比星的耐药性

目的　探讨本芴醇衍生物LY980 5 0 3对肿瘤多药耐药的逆转作用及其作用机理。方法　采用噻唑蓝 (MTT)法检测细胞毒作用 ;采用流式细胞术测定细胞内多柔比星 (Dox)浓度 ;应用人乳腺癌裸鼠移植瘤模型研究LY980 5 0 3对肿瘤多药耐药的体内逆转作用。结果　LY980 5 0 3在 4 .0 μmol·L- 1(非细胞毒剂量 )能大部逆转人乳腺癌耐Dox细胞株MCF/Dox对Dox的耐药性 ;药物蓄积实验表明 ,LY980 5 0 3能显著增加MCF/Dox细胞内Dox蓄积 ;10 μmol·L- 1LY980 5 0 3作用 96h能明显抑制MCF/Dox细胞mdr 1基因表达水平。将MCF/Dox细胞接种于裸鼠皮下 ,接种后d 4 2 ,合用LY980 5 0 3(2 0 0mg·kg- 1·d- 1×3,ig)的移植瘤体积 (0 .34± 0 .19)cm3较单用Dox的移植瘤体积 (0 .90± 0 .32 )cm3显著缩小。结论LY980 5 0 3在体外及体内均能有效逆转MCF/Dox细胞对Dox的耐药性。