Imexon-based combination chemotherapy in A375 human melanoma and RPMI 8226 human myeloma cell lines

Purpose This study evaluated the cytotoxic effects of imexon (NSC-714597) in tumor cells when combined with a broad panel of chemotherapeutic drugs. Methods The sulforhodamine B (SRB) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assays were used to analyze the degree of growth inhibition for the combination studies in the A375 human malignant melanoma and RPMI 8226 human multiple myeloma cell lines, respectively. Cells were continuously exposed to both drugs at a constant molar ratio for 4–5 days. Combination effects were analyzed using the Median Effect method. Statistical significance was inferred if the 95% confidence interval for the combination interaction (C.I.) values for a particular two-drug combination did not include 1.0 (additivity). Synergy was inferred for C.I. values < 1.0 and antagonism for CI values > 1.0. Results Imexon was synergistic when combined with DNA-binding agents (cisplatin, dacarbazine, melphalan) and pyrimidine-based antimetabolites (cytarabine, fluorouracil, gemcitabine) in both cell lines. Antagonistic combinations with imexon included methotrexate and the topoisomerase I (TOPO I) and II (TOPO II) inhibitors irinotecan, doxorubicin, mitoxantrone and etoposide. Docetaxel was synergistic with imexon in both cell lines whereas paclitaxel and fludarabine showed a mixed result. Dexamethasone and the proteasome inhibitor bortezomib showed synergy in myeloma cells and additivity in the melanoma cells. The vinca alkaloid, vinorelbine, and the multi-targeted antifol, pemetrexed, were additive with imexon in both cell lines. Discussion The consistent synergy seen for imexon and alkylating agents may relate to the sulfhydryl-lowering effect of imexon, which would render cells more sensitive to electrophilic species from the alkylators. The marked synergy noted with pyrimidine-based antimetabolites was unexpected and may relate to the induction of cell cycle arrest in S-phase. The strong antagonism noted for imexon with topoisomerase I and II inhibitors may be due to the effect of imexon at increasing oxidant levels which are known to antagonize the cytotoxic effects of topoisomerase poisons. In contrast, the synergy seen with bortezomib in myeloma cells may be related to an increase in reactive oxygen species (ROS) from both drugs. These results suggest that combinations of imexon with alkylating agents and pyrimidine-based antimetabolites are rational to pursue in therapeutic studies in vivo.     

Phenotypical alterations induced by glucocorticoids resistance in RPMI 8226 human myeloma cells

Resistance to glucocorticoids (GCs) frequently appears during treatment of hematological malignancies. This study investigates the phenotypical alterations observed in human myeloma cell sublines resistant to glucocorticoids. Using the RPMI8226 cell line, the cytotoxic efficiencies of four glucocorticoids, and the phenotypes of isolated resistant sublines were analyzed. Methyl-prednisolone and dexamethasone exhibited the higher toxic effects on RPMI8226 cells. All corticoids were able to induce drug-resistance. Resistant sublines showed an increased expression of the alpha-isoform of the glucocorticoid receptors (GRs), and specific modulations in CD23, CD38, CD44 and CD58 expressions. Thus, glucocorticoid resistance in RPMI8226 cells is accompanied by significant phenotypical alterations that could be implicated in survival enhancement to therapy and/or tumor spreading.     

PJ34 对多发性骨髓瘤 RPMI8226 细胞体外生长及其对马法兰敏感性的影响

目的：观察PJ34对多发性骨髓瘤细胞株RPMI8226体外生长的影响以及与小剂量马法兰的协同作用,初步探讨其作用机制.方法：采用MTT法检测细胞增殖抑制率,Western blot方法检测FA/BRCA途径中的相关蛋白表达、流式细胞仪测定细胞周期及凋亡率.结果：PJ34能使细胞发生G2/M期阻滞、协同马法兰诱导 细胞凋亡作用.PJ34与马法兰联用与单用马法兰相比,细 胞凋亡率由（31.08±0.47）%增至（45.38±4.53）%.PJ34介导的FA/BRCA途径相关因子受抑制及γH2AX表达增强,从而抑制DNA的损伤修复.结论：PJ34对多发性骨髓瘤RPMI8226细胞有显著的抑制作用,并可增加RPMI8226细胞对烷化剂类化疗药物马法兰的敏感性,其作用机制可能是通过抑制FA/BRCA途径对DNA损伤的修复.PJ34与小剂量烷化剂化疗药物合用,是一种安全有效的逆转耐药的治疗方案.     

Phenotypic and functional analysis of 1,25-dihydroxyvitamin D3 receptor mediated modulation of the human myeloma cell line RPMI 8226

Several recent studies have demonstrated the presence of specific receptors for the 1,25-dihydroxyvitamin D3 (calcitriol) in activated normal lymphocytes. By DNA cellulose chromatography, we show evidence of such specific receptors in the human myeloma cell line RPMI 8226. Nanomolar concentrations of 1,25-dihydroxyvitamin D3 reduce the proliferation of RPMI 8226 cells significantly and simultaneously induce the appearance of both new properties and phenotype expression, such as butyrate esterase, enhanced expression of CD20 (B1), CD15 (Leu-M1) antigens and lambda chains, and decreased expression of the PC1 antigen using microfluorometric analysis. But such an increased expression of membrane lambda chains was not associated with an enhanced secretion of lambda chains. Furthermore, the bone resorbing activity produced normally by RPMI 8226 cells was reduced significantly after 1,25-dihydroxyvitamin D3 treatment. The possible mechanisms and significance of these new functional and phenotypic properties are discussed with respect to the B-cell lineage.     

黄连解毒汤抑制多发性骨髓瘤RPMI8226细胞增生及促凋亡作用的研究

 目的 研究中药黄连解毒汤（HLJDT）对人多发性骨髓瘤（MM）细胞RPMI8226增生和凋亡的作用。方法 以含10 ％胎牛血清的RPMI1640培养基常规培养RPMI8226细胞,分别以不同浓度的HLJDT作用不同的时间后,应用锥虫蓝拒染法测定细胞活力变化,MTT法检测细胞的增生变化;采用流式细胞术测定细胞周期的变化;应用流式细胞仪检测药物细胞的凋亡现象,荧光显微镜下观察AO／EB染色后的细胞凋亡形态变化;比色法检测半胱氨酸蛋白水解酶3（caspase3）活性变化。结果 与对照组相比,200～800 ng／ml浓度的HLJDT可明显抑制细胞增生影响（P＜0.01）,并呈时间和剂量依赖性;使细胞周期阻滞在G0／G1期细胞增多,S期细胞减少,并呈剂量依赖性改变; MM细胞凋亡百分率显著增高（P＜0.01）,免疫荧光显微镜下可见典型的凋亡细胞形态学变化;使caspase3活性增强,且呈剂量和时间依赖性（P＜0.01）。结论 HLJDT能有效抑制MM细胞RPMI8226增生,促其凋亡,G0／G1期细胞比例增加和S期细胞比例减少可能是原因之一;caspase3活性增强可能参与其凋亡过程,具体机制研究还有待完善。     

人类骨髓成纤维样基质细胞对多发性骨髓瘤细胞迁移和归巢特性的影响

 目的　观察人类骨髓成纤维样细胞系HFCL对多发性骨髓瘤细胞RPMI8226增殖、迁移和归巢的影响。方法　采用体外细胞培养,建立RPMI8226细胞和HFCL细胞共培养体系,锥虫蓝拒染法测定生长曲线;流式细胞术（FCM）检测细胞周期和黏附分子CD49d的变化;RT-PCR检测CXCR4基因的表达情况。结果　HFCL细胞抑制 RPMI8226细胞生长,且与HFCL细胞直接接触组的抑制作用大于非直接接触组（Transwell）组。RPMI8226细胞与HFCL细胞共培养后,直接接触组G1期细胞增高,S期细胞减少;HFCL细胞下调RPMI8226细胞的CXCR4和CD49d的表达,单独培养组明显高于直接培养组;Transwell组无明显变化。结论　人类骨髓成纤维样细胞HFCL能抑制多发性骨髓瘤细胞RPMI8226的增殖,抑制CXCR4和CD49d的表达,影响骨髓瘤细胞的迁移和归巢。     

硼替佐米对骨髓瘤细胞株RPMI8226增殖和凋亡影响的研究

目的 探讨硼替佐米对骨髓瘤细胞株RPMI8226增殖和凋亡的影响.方法 采用20、40、60、80和100 nmol/L的硼替佐米处理骨髓瘤细胞株RPMI8226(处理组),以不含硼替佐米的细胞作为对照(对照组).采用MTT法检测硼替佐米对RPMI8226细胞的增殖抑制作用,采用Annexin V-FITC/PI流式细胞术检测细胞凋亡率,采用RT-PCR和Western Blot技术检测细胞Wnt/β-catenin信号通路相关蛋白β-catenin、c-myc及PI3K/AKT信号通路相关蛋白Bcl-2、Bax的mRNA和蛋白表达水平.结果 不同浓度的硼替佐米均可抑制RPMI8226细胞的增殖,且呈剂量效应;20、40、60、80和100 nmol/L硼替佐米处理组的RPMI8226细胞凋亡率分别为(11.80±0.56)%、(19.45±1.25)%、(36.82±2.26)%、(43.56±3.50)%和(56.62±5.02)%,均高于对照组的(8.02±0.45)%,差异均有统计学意义(P﹤0.05).处理组c-myc、β-catenin及Bcl-2的mRNA和蛋白表达水平均低于对照组,且随硼替佐米浓度的增加而下降;而Bax的mRNA和蛋白表达水平均高于对照组,且随硼替佐米浓度的增加而升高.结论 硼替佐米可抑制多发性骨髓瘤细胞的增殖,促进其凋亡,作用机制可能与调控Wnt/β-catenin信号通路和PI3K/AKT信号通路有关.     

葛根总黄酮对骨髓瘤细胞株U266及RPMI8226增殖作用的研究

 【摘要】　目的　初步探讨葛根总黄酮（PRF）对骨髓瘤细胞株U266及RPMI 8226增殖影响及其机制。方法　采用0、10、30、50、100 μg／ml PRF分别处理U266、RPMI 8226细胞 48 h及72 h,MTT法检测细胞增殖抑制率,流式细胞术检测细胞周期变化,瑞特染色观察细胞形态学改变,FITC-Annexin V／PI双染法检测细胞早期凋亡率改变,DNA片段化分析观察PRF处理U266细胞DNA断裂片段。结果　PRF可以抑制2种骨髓瘤细胞增殖,对U266细胞抑制作用大于对RPMI 8226细胞的作用,呈浓度依赖性;随PRF浓度增加2种细胞凋亡比例增加。瑞特染色未观察到2种细胞凋亡形态学特征。0、10、30、50、100 μg／ml PRF 处理U266细胞48 h早期凋亡率分别为（3.20±0.36）%、（5.20±0.92）%、（7.30±1.22）%、（8.10±0.53）%、（10.80±0.90）%,呈剂量依赖性增高,组间差异有统计学意义（P＜0.05）。DNA片段化分析U266细胞未出现凋亡细胞特有的DNA梯带。结论　一定浓度PRF对骨髓瘤U266及RPMI 8226细胞具有较明显的增殖抑制作用;PRF对U266细胞增殖抑制作用机制虽可能与凋亡相关,但并非U266细胞增殖受抑的主要途径,其确切机制有待进一步探讨。     

Multiple mechanisms confer drug resistance to mitoxantrone in the human 8226 myeloma cell line

Selection for in vitro drug resistance can result in a complex phenotype with more than one mechanism of resistance emerging concurrently or sequentially. We examined emerging mechanisms of drug resistance during selection with mitoxantrone in the human myeloma cell line 8226. A novel transport mechanism appeared early in the selection process that was associated with a 10-fold resistance to mitoxantrone in the 8226/MR4 cell line. The reduction in intracellular drug concentration was ATP-dependent and ouabain-insensitive. The 8226/MR4 cell line was 34-fold cross-resistant to the fluorescent aza-anthrapyrazole BBR 3390. The resistance to BBR 3390 coincided with a 50% reduction in intracellular drug concentration. Confocal microscopy using BBR 3390 revealed a 64% decrease in the nuclear:cytoplasmic ratio in the drug-resistant cell line. The reduction in intracellular drug concentration of both mitoxantrone and BBR 3390 was reversed by a novel chemosensitizing agent, fumitremorgin C. In contrast, fumitremorgin C had no effect on resistance to mitoxantrone or BBR 3390 in the P-glycoprotein-positive 8226/DOX6 cell line. Increasing the degree of resistance to mitoxantrone in the 8226 cell line from 10 to 37 times (8226/MR20) did not further reduce the intracellular drug concentration. However, the 8226/MR20 cell line exhibited 88 and 70% reductions in topoisomerase II beta and alpha expression, respectively, compared with the parental drug sensitive cell line. This decrease in topoisomerase expression and activity was not observed in the low-level drug-resistant, 8226/MR4 cell line. These data demonstrate that low-level mitoxantrone resistance is due to the presence of a novel, energy-dependent drug efflux pump similar to P-glycoprotein and multidrug resistance-associated protein. Reversal of resistance by blocking drug efflux with fumitremorgin C should allow for functional analysis of this novel transporter in cancer cell lines or clinical tumor samples. Increased resistance to mitoxantrone may result from reduced intracellular drug accumulation, altered nuclear/cytoplasmic drug distribution, and alterations in topoisomerase II activity.     

Clonal variability in CD95 expression is the major determinant in Fas-medicated, but not chemotherapy-medicated apoptosis in the RPMI 8226 multiple myeloma cell line.

CD95 (Fas/APO-1) is a member of the TNFR superfamily that induces apoptosis following cross-linking with its cognate ligand, CD95L (FasL/APO-1L) or agonist antibody. The human myeloma cell line, RPMI 8226, has limited sensitivity to CD95-mediated apoptosis, with a maximum of 65% of the population responding. To determine the source of the limited sensitivity to CD95-mediated apoptosis, we isolated multiple clones from the RPMI-8226 cell line by limiting dilution. Analysis of these clones demonstrated that sensitivity to CD95-mediated cell death directly correlated with CD95 expression. Clones with high levels of CD95 expression had greater than 90% cell death, whereas cells with low levels of expression had less than 10% cell death. In contrast, no correlative differences were identified for other members of the DISC complex, or for members of the anti-apoptotic Bcl-2 family. We further examined the sensitivity of the 8226 clones to various cytotoxic agents. Although modest clonal variability was demonstrated in response to the chemotherapeutic drugs, doxorubicin, etoposide (VP-16), and vincristine, there was no correlation between CD95 function and sensitivity to chemotherapeutic drugs. These results indicate that in this cell line, receptor expression is rate limiting in CD95-mediated apoptosis, whereas CD95 expression was not a determinant in drug-induced programmed cell death.     

Nuclear DNA content and chromatin texture in multidrug-resistant human leukemic cell lines

Nuclear morphological alterations associated with multidrug resistance (MDR) were evaluated by image cytometry in various human leukemic cell sub-lines: 3 cell lines with P-gp-mediated resistance (CEM-VLB, HL60/Vinc, K562-Dox), the non-Pgp-mediated MDR HL60/AR leukemic cell line with over-expres-sion of MRP, and the at-MDR CEM-VMI leukemic cell line with alteration of topoisomerase II. All these MDR cell sub-lines were obtained by drug selection and were compared with their sensitive counterparts and with the hamster LR73-R cell line obtained by transfection of mouse mdrl cDNA. All MDR cell sub-lines obtained by drug selection displayed decreased DNA Feulgen stainability as compared with their respective sensitive parental cell line, a phenomenon not observed in the trans-fected LR73-R cells. Nuclear texture analysis on G₀/G₁-selected cell nuclei revealed 2 types of textural phenotype. The first phenotype was characterized by chromatin decondensation with small but compact chromatin clumps, and was observed in drug-selected P-gp-mediated MDR cells (CEM-VLB, HL60-Vinc, K562-Dox) and in the non-P-gp-mediated MDR HL60/AR cell line. The second phenotype was characterized by a condensed and homogeneous chromatin pattern, and was observed in the at-MDR CEM-VMI cell line. LR73-R cells transfected with mdrl cDNA did not display any significant changes in textural pheno-type as compared with sensitive LR73 cells, suggesting that P-gp over-expression alone cannot account for the cytological modi-fications observed in MDR cells. These data suggest that multidrug resistance could be associated with specific nuclear morphological changes which appeared to be a consequence of alterations occurring during selection by cytotoxic drugs rather than of P-gp over-expression. © 1995 Wiley-Liss, Inc.     

Decoupling of normal CD40/interleukin-4 immunoglobulin heavy chain switch signal leads to genomic instability in SGH-MM5 and RPMI 8226 multiple myeloma cell lines.

The processes mediating genomic instability and clonal evolution are obscure in multiple myeloma (MM). Acquisition of new chromosomal translocations into the switch region of the immunoglobulin heavy chain (IgH) gene (chromosome 14q32) in MM, often heralds transformation to more aggressive disease. Since the combined effects of CD40 plus interleukin-4 (IL-4) mediate IgH isotype class switch recombination (CSR), and this process involves DNA double strand break repair (DSBR), we hypothesized that CD40 and/or IL-4 activation of MM cells could induce abnormal DNA DSBR and lead to genomic instability and clonal evolution. In this study, we show that MM cell lines that are optimally triggered via CD40 and/or IL-4 demonstrate abnormal decoupling of IL-4 signal transduction from CD40. Specifically, CD40 alone was sufficient to trigger maximal growth of tumor cells. We further demonstrate that CD40 triggering induced both DNA DSBs as well as newly acquired karyotypic abnormalities in MM cell lines. Importantly, these observations were accompanied by induction of activation induced cytidine deaminase expression, but not gross apoptosis. These data support the role of abnormal CD40 signal transduction in mediating genomic instability, suggesting a role for the CD40 pathway and intermediates in myelomagenesis and clonal evolution in vivo.     

多发性骨髓瘤细胞株PRIM8226侧群细胞分选及其生物学特性的研究

目的 检测和分选多发性骨髓瘤（MM）细胞株PRIM8226中的侧群细胞（SP细胞）并鉴定其生物学特性.方法 以Hoechst33342/碘化丙啶（PI）荧光染料双染,维拉帕米拮抗对照,应用流式细胞术荧光激活分选法检测并分选MM细胞株PRIM8226 SP细胞,并通过细胞生长曲线、细胞周期、免疫表型、集落形成实验、RT-PCR检测干细胞特异标志物mRNA表达量、裸鼠体内成瘤实验等对SP细胞的生物学特性进行初步探讨.结果 MM细胞株PRIM8226 SP细胞含量为（1.78±0.89）％,采用流式细胞术成功分选SP细胞.生长曲线显示：SP细胞分选初期生长较主群细胞（MP细胞）缓慢,进入稳定增长期后增殖能力与MP细胞差异无统计学意义（P＞0.05）.细胞周期分析显示：SP细胞与MP细胞相比,周期多处于Go/G1期[（44.34±3.09）％、（28.49±1.97）％,P＜0.05],较少的细胞处于S期[（38.83±3.69）％、（51.49±4.62）％,P＜ 0.05].在免疫表型研究中,观察到SP和MP细胞的CD138、CD38表达分别为（78.5±8.5）％、（82.0±4.0）％和（72.3±15.7）％、（84.3±11.9）％,差异均无统计学意义（均P＞0.05）.MM细胞株PRIM8226 SP细胞的单细胞克隆直径、克隆形成数、克隆形成率均高于MP细胞[0.280±0.016和0.118±0.019、1 722±127和358±14、（86.1±3.46）％和（17.9±1.88）％,P＜0.05].RT-PCR显示SP细胞干细胞标志性基因的表达高于MP细胞：c-myc[（29.90±3.73）％、（16.84±2.35）％]、KIF4[（29.97±2.89）％、（19.06±1.23）％]、SOX2[（40.00±4.58）％、（16.62±2.09）％]、OCT4[（32.96±1.56）％、（23.27±0.92）％]（均P＜0.05）.裸鼠体内成瘤实验显示SP细胞成瘤能力显著高于MP细胞（最低成瘤数量分别为5×103、5×105个）.结论 MM细胞株PRIM8226的SP细胞在静止期细胞比例、集落形成能力、干细胞标记c-myc、KIF4、SOX2、OCT4基因表达量、体内成瘤能力上与MP细胞差异均有统计学意义,而SP细胞和MP?     

Effect of vinorelbine on the growth of human myeloma cell lines in vitro

Vinorelbine (NVB) is a newly synthesized vinca alkaloid that has been used to treat advanced malignant diseases including lung adenocarcinoma and lymphoma. The effect of NVB on myeloma, however, is unknown. We therefore examined the effect of NVB on the growth of human myeloma cell lines (RPMI8226, U266 and KPMM2) using the trypan blue dye exclusion test and Alamar blue assay. NVB inhibited the growth of myeloma cells of all three cell lines dose-dependently and this effect was intensified when NVB was combined with dexamethasone at 1.0 x 10(-6)mol/l. Flow cytometric analysis using annexin V (AN) and 7-amino-actinomycin D (7AAD) showed that NVB-induced apoptosis of these myeloma cells in all the cell lines. NVB appears to be a potent inducer of apoptosis in myeloma cells, and might have some benefit in the treatment of myeloma patients.     

Gene expression patterns associated with the metastatic phenotype in rodent and human tumors

Using subtractive technology, we have generated metastasis-associated gene expression profiles for rat mammary and pancreatic adenocarcinomas. Several genes whose expression is thought to be related to tumor progression such as c-Met, urokinase-type plasminogen activator receptor, ezrin, HMG-1, oncomodulin, cathepsin, and caveolin were thereby isolated. Half of the metastasis-associated clones showed no significant homology to genes with known function. Notably, several of the metastasis-associated clones were also expressed in metastatic lines but not in nonmetastatic lines of other tumor models. Furthermore, in situ hybridization using selected clones documents the relevance of these results for human cancer because strong expression in tumor cells including metastases was detected in human colorectal cancer samples and, to a lesser extent, in mammary cancer samples. These data support the concept that tumors express a "metastatic program" of genes.