The HSP90 inhibitor 17-PAG effectively inhibits the proliferation and migration of androgen-independent prostate cancer cells

Castration-resistant prostate cancer (CRPC) ultimately occurs after a period of treatment with androgen deprivation therapy. Furthermore, CRPC patients can only derive limited survival benefits from traditional cytotoxic drugs. HSP90, which is a molecular chaperone, plays a vital role in client protein processing and maintaining the function of cells. HSP90 is usually overexpressed in prostate cancer tissues, which makes it a potential target for managing prostate cancer. Geldanamycin (GA), which was recognized as the first natural HSP90 inhibitor, has demonstrated potent anti-tumor efficacy in large-scale pre-clinical studies, but its application in the clinic is not permitted due to its liver toxicity and unstable physical properties. In this study, we report a new GA derivative, 17-PAG (17-(propynylamino)-17-demethoxygeldanamycin), which demonstrates highly effective anti-tumor activity against androgen-independent prostate cancer cells. Treating cells with 17-PAG dose-dependently suppressed proliferation, reduced colony formation and induced apoptosis of DU-145/C4-2B cells. Moreover, 17-PAG suppressed the migration and invasion of DU-145/C4-2B cells by regulating epithelial mesenchymal transition (EMT). 17-PAG also downregulated the HSP90 client proteins, including Her2, EGFR, C-Raf, AKT, p-AKT, and CDK4. Animal assays confirmed that 17-PAG shows strong anti-tumor effects with no obvious organ toxicity in DU-145 cell xenografted nude mice. These results provide us with a potential target for treating androgen-independent prostate cancer in a safe and effective manner.     

吸水链霉菌17997产生氢醌型格尔德霉素及其生物合成中间产物

目的 了解格尔德霉素生物合成PKS后修饰过程中的一些细节.方法 对格尔德霉素产生菌吸水链霉菌17997及其格尔德霉素生物合成聚酮合酶(polyketide synthase,PKS)后修饰基因阻断变株(gdmP-和gdmN-)在ISPII平板不同时间的培养物进行乙酸乙酯提取,硅胶板TLC和NaOH显色分析,检测GDM及其生物合成中间产物,并利用LC-MS对中间产物进行鉴定.结果 吸水链霉菌17997原株、gdmN-和gdmP-变株在培养时间72～96h,发现氢醌型格尔德霉素(GQH2)、氢醌型4,5-双氢-7-去氨甲酰基-7-羟基格尔德霉素(H2GQH2-dC)和氢醌型4,5-双氢格尔德霉素(H2GQH2)分别为主要组分,相应的醌型化合物为次要组分;之后,这些氢醌型化合物随培养时间延长逐渐消失,相应的醌型化合物成为主要组分.双向硅胶板TLC分析证实GQH2、H2GQH2-dC和H2GQH2均可在空气中自发氧化为相应的醌型化合物.结论 在吸水链霉菌17997的GDM生物合成PKS后修饰过程中,首次提出GQH2自发氧化为GDM可能是氢醌型向醌型转变的位点,同时它也是GDM生物合成最后一步.     

格尔德霉素对胆囊癌的体外治疗作用

目的 观察格尔德霉素(GA)对胆囊癌细胞生长、运动和侵袭的影响及其化疗增敏作用.方法 噻唑蓝(MTT)比色法检测(0、0.0064、0.032、0.16、0.8、4、20、100)×10-6 mol/L浓度梯度的GA对胆囊癌细胞GBC-SD生长影响;观察1 μmoL/L的GA对0.1倍最大血药浓度(Maximal plasma concentration,Cmax)的5-氟尿嘧啶(5-Fu,Cmax 10 mg/L)、丝裂霉素(MMC,Cmax 3 mg/L)、阿霉素(ADM,Cmax 0.4 mg/L)的化疗增敏作用.应用迁移运动及侵袭实验观察1μmol/L的GA体外对胆囊癌细胞运动、侵袭能力的影响.结果 GA体外对胆囊癌细胞有较强的抑制作用,半数抑制浓度(Inhibitory concentration 50%,IC50)在20μmol/L水平.1μmol/L低生长抑制浓度的GA能够增加传统化疗药物对GBC-SD生长的抑制作用,有明显的增效作用;同时低浓度的GA可以抑制肝细胞生长因子(HGF)对GBC-SD运动迁移和侵袭能力的诱导作用.结论 GA有可能成为胆囊癌化疗和抗转移的有效药物.     

格尔霉素降低Raf-1和AKt水平诱导神经母细胞瘤凋亡的研究

目的：探讨格尔霉素(GA)是否会改变对神经细胞的存活起关键作用的信号传导蛋白Raf-1和AKT的表达，诱导神经母细胞瘤细胞凋亡。方法：在不同时间内用GA处理人神经母细胞瘤细胞(SH-gy5y，SK-N-SH，LAN-1)，MTT分析细胞存活率，DNA碎片ELISH流动细胞计数Western Blot分析凋亡情况。结果：GA能降低Raf-1和AKT的活性，激活Caspase-9和Caspase-3，线粒体释放细胞色素C继之切割PARP，诱导细胞凋亡。结论：GA可能是一种有效治疗神经母细胞瘤的药物。     

TRIM5alpha association with cytoplasmic bodies is not required for antiretroviral activity

The tripartite motif (TRIM) protein, TRIM5alpha, restricts infection by particular retroviruses. Many TRIM proteins form cytoplasmic bodies of unknown function. We investigated the relationship between cytoplasmic body formation and the structure and antiretroviral activity of TRIM5alpha. In addition to diffuse cytoplasmic staining, the TRIM5alpha proteins from several primate species were located in cytoplasmic bodies of different sizes; by contrast, TRIM5alpha from spider monkeys did not form cytoplasmic bodies. Despite these differences, all of the TRIM5alpha proteins exhibited the ability to restrict infection by particular retroviruses. Treatment of cells with geldanamycin, an Hsp90 inhibitor, resulted in disappearance or reduction of the TRIM5alpha-associated cytoplasmic bodies, yet exerted little effect on the restriction of retroviral infection. Studies of green fluorescent protein-TRIM5alpha fusion proteins indicated that no TRIM5alpha domain is specifically required for association with cytoplasmic bodies. Apparently, the formation of cytoplasmic bodies is not required for the antiretroviral activity of TRIM5alpha.     

Thermo-targeted drug delivery of geldanamycin to hyperthermic tumor margins with diblock elastin-based biopolymers

The tumor margins are the barrier to hepatocellular carcinoma (HCC) eradication for tumors > 3 cm. Indeed, inadequately treated tumor margins commonly result in local and regional HCC recurrence with increased size and mass. Tumor recurrence is a common problem with chemotherapy, radiotherapy, thermal ablation, and/or surgical resection, by the inability to properly treat the tumor core and the tumor margins. Here we present novel thermosensitive biopolymer-drug conjugates for thermo-targeted chemotherapy at hyperthermic isotherms produced by focal, locoregional thermal ablation. The chemotherapeutic target is heat shock protein 90 (HSP90), a key molecular chaperone of several, and potent pro-oncogenic pathways including Akt, Raf-1, and mutated p53 that is upregulated in HCC. To inhibit HSP90, we have chosen geldanamycin (GA), a potent HSP90 inhibitor. GA has gained significant attention for its low IC50 ~ 1nM and inhibition of Akt and Raf-1, amongst other critical pro-oncogenic pathways. Despite such evidence, clinical trials of GA have not shown promise due to off-target toxicity and poor formulation design. Here, we propose using diblock elastin-based biopolymers as a Ringsdorf macromolecular GA solubilizer — a new generation containing functional poly(Asp)/(Glu) blocks for facile drug conjugation and an ELP block for thermo-targeting of hyperthermic ablative margins. GA release is controlled by pH-sensitive, covalent hydrazone bonds with the biopolymer backbone to avoid systemic toxicity and off-target effects. The resultant biopolymer-conjugates form stable nanoconstructs and display tunable, acute phase transitions at high temperatures. Drug release kinetics are favorable with or without the presence of serum. Thermo-targeted chemotherapy and synchronous thermal ablation provide a unique opportunity for simultaneous destruction of the HCC ablative margins and tumor core for focal, locoregional control of HCC.     

Efficacy of Hsp90 inhibition for induction of apoptosis and inhibition of growth in cervical carcinoma cells in vitro and in vivo

Purpose Heat shock protein 90 (Hsp90) is a conserved chaperone involved in crucial signaling events in normal and malignant cells. Previous research suggests that tumor cells are particularly dependent on Hsp90 for survival as well as malignant progression. Hsp90 inhibitors which are derivates of the natural compound geldanamycin, such as the orally bioavailable 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), are currently being tested in clinical trials and small molecule inhibitors are in development. In this study we investigated the response of a panel of cervical carcinoma cell lines in vitro and in vivo to determine potential factors that might influence the sensitivity towards Hsp90 inhibition. Methods Cell viability, proliferation and drug-induced changes on Hsp90 chaperoned “client” factors were examined with focus on G2/M cell cycle regulators, and a comparison with immortalized and normal keratinocytes was performed. ME180 and CaSki cells were grown as subcutaneous xenografts in mice treated with 6–10 mg/kg 17-DMAG by oral gavage 2×/day on a chronic schedule. Tissue concentrations of 17-DMAG were measured by high performance liquid chromatography. Results Cell death during abnormal mitosis was observed within 48 h after treatment start. ME180 and CaSki showed more cell death at this time point than SiHa and HeLa, and higher levels of pre-treatment Akt activity. IC₅₀ values ranged between 17 and 37 nanoM geldanamycin (MTS). Keratinocytes were at least as sensitive as carcinoma cells. All cell lines responded with an increase of the G2/M fraction. Despite in vitro effectiveness and tissue concentrations of 1 μM, only a limited tumor growth reduction was observed with 17-DMAG given close to the maximum tolerated dose level. Lower levels of Hsp90 protein, a lower Akt activity and signs of tissue hypoxia were observed in xenografts compared to cell cultures. Conclusions We show here that Hsp90 inhibition effectively induces apoptosis and growth arrest in cervical carcinoma cells in vitro. Mitotic catastrophe was identified as one mechanism of cell death. In contrast, a limited efficacy of 17-DMAG was observed in subcutaneous xenograft models. Induction of a heat shock response has previously been implicated in resistance towards Hsp90 inhibition. Additional factors might be (1) an altered abundance and/or activity of primary (Hsp90) and secondary (e.g., Akt) target(s), (2) a narrow therapeutic range of 17-DMAG by oral application and (3) response-modifying factors within the tumor environment. The further development of synthetic Hsp90 inhibitors with increased therapeutic window is warranted.     

热休克蛋白90在门脉高压大鼠内脏高动力循环中的作用

目的研究热休克蛋白90(HSP90)在门脉高压大鼠内脏高动力循环中的作用。方法20只SD大鼠制成门脉高压动物模型,10只大鼠行假手术作为对照。4周后处死动物获取肠系膜动脉。测定其对甲氧胺(MTX)和乙酰胆碱的量效曲线。然后再灌注格尔德霉素(GA),再次测量其量效曲线。去内膜后,再测量肠系膜动脉对硝普钠(SNP)的量效曲线。结果肠系膜动脉对MTX的反应性降低。而GA能增强门脉高压大鼠肠系膜血管对MTX的反应性。GA还能减少肠系膜血管乙酰胆碱依赖的血管扩张,但不能减少SNP依赖的血管扩张。结论本研究说明了HSP90在门脉高压大鼠内脏高动力循环中起重要作用。     

Pharmacokinetics and pharmacodynamics of 17-demethoxy 17-[[(2-dimethylamino)ethyl]amino]geldanamycin (17DMAG, NSC 707545) in C.B-17 SCID mice bearing MDA-MB-231 human breast cancer xenografts

Purpose 17-demethoxy 17-[[(2-dimethylamino)ethyl]amino]geldanamycin (17DMAG, NSC 707545) is a water-soluble analogue of 17-(allylamino)-17-demethoxygeldanamycin (17AAG), a compound currently in clinical trials. These preclinical studies: (1) characterized 17DMAG concentrations in plasma, normal tissues, and tumor after i.v. delivery to mice; and (2) correlated tumor and normal tissue 17DMAG concentrations with alterations in heat shock protein 90 (HSP90) and selected HSP90-chaperoned proteins.Methods At specified times after i.v. administration of 75 mg/kg 17DMAG, SCID mice bearing s.c. MDA-MB-231 human breast xenografts were killed and plasma and tissues were retained. 17DMAG concentrations were determined by HPLC. Raf-1, heat shock protein 70 (HSP70), and HSP90 in tissues were determined by Western blotting.Results Peak plasma 17DMAG concentration was 15.4±1.4 g/ml. The area under the plasma 17DMAG concentration versus time curve was 1072 g/ml min, corresponding to a total body clearance of 70 ml/kg/min. Peak 17DMAG concentrations in liver (118.8±5.7 g/g), kidney (122.9±10.6 g/g), heart (81.3±8.1 g/g), and lung (110.6±25.4 g/g) occurred at 5–10 min, while peak concentrations in spleen (70.6±9.6 g/g) and tumor (9.0±1.0 g/g) occurred at 30–45 min. At 48 h, 17DMAG was detectable in tumor but not in any normal tissue. Raf-1 in tumors of 17DMAG-treated mice killed at 4, 7, 24 and 48 h was about 20% lower than in tumors from vehicle-treated mice. HSP90 and HSP70 in tumors of 17DMAG-treated animals were significantly lower than in tumors of control animals at 4, 7, and 24 h. Hepatic Raf-1 was decreased by more than 60% at all times after 17DMAG treatment; however, hepatic HSP90 was not affected. HSP70 was undetectable in livers of vehicle-treated mice or mice killed at 2 or 4 h after 17DMAG treatment, but was detected in livers at 7, 24 and 48 h. 17DMAG did not affect renal Raf-1. In contrast, renal HSP70 and HSP90 were decreased by more than 50% at 2 and 4 h after 17DMAG treatment. Renal HSP70 increased approximately twofold above that in kidneys from vehicle-treated control mice at 7 and 24 h, while HSP90 relative protein concentration was no different from that in controls.Conclusions Plasma pharmacokinetics of 17DMAG in tumor-bearing mice were similar to those previously reported in nontumor-bearing mice. 17DMAG was distributed widely to tissues but was retained for longer in tumors than normal tissues. Raf-1, HSP90, and HSP70 were altered to different degrees in tumors, livers, and kidneys of 17DMAG-treated animals. These data illustrate the complex nature of the biological responses to 17DMAG.This work was supported by contract NO1-CM07106 and Grant 2P30 CA47904, awarded by the National Cancer Institute.