Taxol-resistant epithelial ovarian tumors are associated with altered expression of specific beta-tubulin isotypes.

The treatment of advanced ovarian cancer with taxol is hindered by the development of drug resistance. The cellular target for taxol is the microtubule that is stabilized by the drug. Taxol preferentially binds to the beta subunit of tubulin of which there are six distinct isotypes in mammalian cells. We have used highly specific oligonucleotides and polymerase chain reaction to analyze expression of all six beta-tubulin genes. Human lung cancer cells (A549) were selected in 12 and 24 nM taxol resulting in cell lines that were 9- and 17-fold resistant, respectively. These cells displayed an altered ratio of classes I, II, III, and IVa beta-tubulin isotypes. Ovarian tumors, seven untreated primary and four taxol- resistant tumor-bearing ascites, displayed significant increases (P < 0.005) in classes I (3.6-fold), III (4.4-fold), and IVa (7.6-fold) isotypes in the taxol-resistant samples as compared with untreated primary ovarian tumors. The increased expression appears to be related to the resistance phenotype, as the basal levels of the class III and IVa isotypes in the untreated tumors were extremely low. This is the first report of altered expression of specific beta-tubulin genes in taxol-resistant ovarian tumors and we propose that the latter may play a role in clinical resistance to taxol.     

Musashi-1在妇科恶性肿瘤发生发展中的作用

妇科恶性肿瘤严重威胁女性健康,尽管目前治疗策略相对有效,但复发及耐药仍是影响整体生存率的重要因素。研究表明肿瘤的复发及耐药与具有自我更新、无限增殖、多向分化潜能及高致瘤性的肿瘤干细胞(cancer stem cells,CSCs)亚群密切相关。Musashi-1是一种最新研究报道的CSCs标志物,多数研究认为其通过Notch、Wnt等信号通路发挥作用,在多种肿瘤组织中异常表达,在妇科恶性肿瘤中高表达,且与肿瘤的分期、分化、血管浸润及化学药物治疗耐药等密切相关。深入研究其在妇科恶性肿瘤中的作用机制,可为妇科恶性肿瘤的临床治疗提供新思路。现就Musashi-1在妇科恶性肿瘤中的表达情况及作用机制进行综述。     

Establishment of a paclitaxel resistant human breast cancer cell strain (MCF-7/Taxol) and intracellular paclitaxel binding protein analysis

Multidrug resistance of tumours is one of the most important factors that leads to chemotherapy failure. A multidrug-resistant breast cancer cell line, MCF-7/Taxol, was established from the drug-sensitive parent cell line MCF-7. The biological properties of MCF-7/Taxol, including its drug resistance profile and profile of paclitaxel binding proteins, were analysed and compared with the parent cell line. A number of paclitaxel binding proteins were present in MCF-7 cells but absent from MCF-7/Taxol cells, namely heat shock protein 90, actinin and dermcidin precursor. The identification of differential paclitaxel binding proteins between the multidrug-resistant MCF-7/Taxol cell line and the parent drug-sensitive cell line MCF-7 provides insight into possible mechanisms involved in resistance to these chemotherapy drugs.     

中药干预外泌体影响胃癌治疗的研究进展

外泌体是近年来十分热门的话题,它是一种极微小的囊泡样物质,是由细胞分泌并帮助细胞与细胞之间传递生物信息的一种特殊物质。外泌体可携带肿瘤的遗传信息,向周围细胞组织,甚至远处细胞组织传递癌症信号,在肿瘤的发生机制中起到重要作用,可以参与肿瘤的生长、侵袭、转移、耐药等多种环节当中。近年来,中药在胃癌治疗中也被证实了可以影响外泌体的相关机制,外泌体在胃癌的诊治方面表现出较好的前景,特别是中药在治疗胃癌中与外泌体之间的联系。研究中药对肿瘤外泌体的影响,从微观的角度探求一条新的中药治疗胃癌的发展道路是亟待解决的问题。本文从外泌体对胃癌的作用机制及中药干预外泌体影响胃癌疗效等方面进行综述,希望能为胃癌的治疗提供更好、更新的助力。     

Acid Ceramidase Upregulation in Prostate Cancer Cells Confers Resistance to Radiation: AC Inhibition, a Potential Radiosensitizer

Radiation resistance in a subset of prostate tumors remains a challenge to prostate cancer radiotherapy. The current study on the effects of radiation on prostate cancer cells reveals that radiation programs an unpredicted resistance mechanism by upregulating acid ceramidase (AC). Irradiated cells demonstrated limited changes of ceramide levels while elevating levels of sphingosine and sphingosine-1-phosphate. By genetically downregulating AC with small interfering RNA (siRNA), we observed radiosensitization of cells using clonogenic and cytotoxicity assays. Conversely, AC overexpression further decreased sensitivity to radiation. We also observed that radiation-induced AC upregulation was sufficient to create cross-resistance to chemotherapy as demonstrated by decreased sensitivity to Taxol and C₆ ceramide compared to controls. Lower levels of caspase 3/7 activity were detected in cells pretreated with radiation, also indicating increased resistance. Finally, utilization of the small molecule AC inhibitor, LCL385, sensitized PPC-1 cells to radiation and significantly decreased tumor xenograft growth. These data suggest a new mechanism of cancer cell resistance to radiation, through upregulation of AC that is, in part, mediated by application of the therapy itself. An improved understanding of radiotherapy and the application of combination therapy achieved in this study offer new opportunities for the modulation of radiation effects in the treatment of cancer.     

In-vivo efficacy of novel paclitaxel nanoparticles in paclitaxel-resistant human colorectal tumors.

Colloidal carriers have been shown to improve tumor therapy by increased drug delivery into tumor sites resulting directly from the enhanced permeability and retention effect (EPR). However, the clinical outcome of tumor therapy is often limited due to multidrug resistance. Several different types of resistance exist with expression of p-glycoprotein being the most commonly described. Paclitaxel entrapped in emulsifying wax nanoparticles (PX NPs) was shown to overcome drug resistance in a human colon adenocarcinoma cell line (HCT-15). In the present studies, the in-vivo efficacy of PX NPs in a HCT-15 mouse xenograft model was demonstrated. Significant inhibition in tumor growth was observed in mice receiving PX NPs treatment. Additionally, mice dosed with Taxol also demonstrated slower tumor growth; however, the efficacy of the Taxol treatment was shown in the in-vitro HUVEC model to be due to the antiangiogenic effect of paclitaxel. It was concluded that the enhanced efficacy of PX NPs over Taxol in the xenograft model was due to both overcoming paclitaxel resistance and an antiangiogenic effect.     

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.     

Trastuzumab causes antibody-dependent cellular cytotoxicity-mediated growth inhibition of submacroscopic JIMT-1 breast cancer xenografts despite intrinsic drug resistance

Trastuzumab is a recombinant antibody drug that is widely used for the treatment of breast cancer. Despite encouraging clinical results, some cancers are primarily resistant to trastuzumab, and a majority of those initially responding become resistant during prolonged treatment. The mechanisms of trastuzumab resistance have not been fully understood. We examined the role of antibody-dependent cellular cytotoxicity (ADCC) using JIMT-1 cells that are ErbB2 positive but intrinsically resistant to trastuzumab in vitro. Unexpectedly, in experiments mimicking adjuvant therapy of submacroscopic disease in vivo (JIMT-1 cells inoculated s.c. in severe combined immunodeficiency mice), trastuzumab was able to inhibit the outgrowth of macroscopically detectable xenograft tumors for up to 5-7 weeks. The effect is likely to be mediated via ADCC because trastuzumab-F(ab')(2) was ineffective in this model. Moreover, in vitro ADCC reaction of human leukocytes was equally strong against breast cancer cells intrinsically sensitive (SKBR-3) or resistant (JIMT-1) to trastuzumab or even against a subline of JIMT-1 that was established from xenograft tumors growing despite trastuzumab treatment. These results suggest that ADCC may be the predominant mechanism of trastuzumab action on submacroscopic tumor spread. Thus, measuring the ADCC activity of patient's leukocytes against the tumor cells may be a relevant predictor of clinical trastuzumab responsiveness in vivo.     

乳腺癌HER-2靶向治疗的现状与发展前景

目的人表皮生长因子受体2(HER2)是表皮生长因子受体(EGFR或Er Bb)家族中扮演中心角色的一个成员。本文对HER2靶向治疗的现状与发展方向作一综述。方法查阅Pubmed、中国知网、万方、维普等数据库与乳腺癌HER2靶向治疗方面相关的文章,共纳入52篇文献。结果 HER2信号能够调节细胞增殖、存活和分化,与乳腺癌、胃癌、肺癌与卵巢癌等多种肿瘤的发生发展密切相关。目前使用的HER2靶向治疗有助于改善临床化疗药物疗效、提高患者无疾病生存期和5年存活率,但肿瘤的耐药性也越来越严重,已经引起人们的关注。结论 HER2靶向治疗对提高HER2阳性乳腺癌患者治疗效果起到重要作用,其耐药性需要进一步研究解决。     

In vivo evaluation of polymeric micellar paclitaxel formulation: toxicity and efficacy.

Although the current clinical formulation of paclitaxel (Taxol) has a promising clinical activity against a wide variety of tumors, it has significant toxic side effects, some of which are associated with its formulation in a 1:1 (v/v) mixture of Cremophor EL and dehydrated alcohol. One of the problems associated with the intravenous administration of paclitaxel is its low solubility in water. Our study was designed to evaluate the pharmacokinetics, tissue distribution, toxicity and efficacy of a paclitaxel (Genexol)-containing biodegradable polymeric micellar system (Genexol-PM) in comparison to Taxol. Genexol-PM was newly developed by using a low molecular weight, nontoxic and biodegradable amphiphilic diblock copolymer, monomethoxy poly(ethylene glycol)-block-poly(D,L-lactide) (mPEG-PDLLA) and paclitaxel (Genexol, Samyang Genex Co., Seoul, Korea). In a human cancer cell line model, Genexol-PM and Taxol showed comparable in vitro cytotoxicity against human ovarian cancer cell line OVCAR-3 and human breast cancer cell line MCF7. The maximum tolerated dose (MTD) of Genexol-PM and Taxol in nude mice was determined to be 60 and 20 mg/kg, respectively. The median lethal dose (LD(50)) in Sprague--Dawley rats was 205.4 mg/kg (male) and 221.6 mg/kg (female) for Genexol-PM, while 8.3 mg/kg (male) and 8.8 mg/kg (female) for Taxol. After intravenous administration of Genexol-PM in murine B16 melanoma-induced female SPF C57BL/6 mice at a dose of 50 mg/kg, the area under the plasma concentration-time curve (AUC) was similar to Taxol((R)) at a dose of 20 mg/kg, but biodistribution of paclitaxel after administration of Genexol-PM showed 2 to 3-fold higher levels in tissues including liver, spleen, kidneys, lungs, heart and tumor as compared to Taxol. The in vivo antitumor efficacy of Genexol-PM as measured by reduction in tumor volume of SKOV-3 human ovarian cancer implanted in nude (nu/nu) athymic mice and MX-1 human breast cancer implanted in Tac:Cr:(NCr)-nu athymic mice was significantly greater than that of Taxol. The results of cytotoxicity, MTD, LD(50) and antitumor efficacy suggest that Genexol-PM may have a great advantage over present-day chemotherapy with Taxol.     

Hedgehog信号通路介导白血病干细胞耐药

耐药与复发是当前急性白血病治疗的瓶颈,逆转白血病干细胞（LSC）耐药,清除体内残留LSC是治愈白血病的关键。近来研究发现,异常激活的Hedgehog（HH）信号通路在多种肿瘤发生发展中发挥重要作用,同时也是LSC产生多重耐药的关键机制之一。本文简要叙述HH信号通路介导LSC耐药的机制,为清除体内残留LSC提供新思路。     

A new mechanism of drug resistance in breast cancer cells: fatty acid synthase overexpression-mediated palmitate overproduction

Multidrug resistance is a major problem in successful cancer chemotherapy. Various mechanisms of resistance, such as ABC transporter-mediated drug efflux, have been discovered using established model cancer cell lines. While characterizing a drug-resistant breast cancer cell line, MCF7/AdVp3000, we found that fatty acid synthase (FASN) is overexpressed. In this study, we showed that ectopic overexpression of FASN indeed causes drug resistance and that reducing the FASN expression increased the drug sensitivity in breast cancer cell lines MCF7 and MDA-MB-468 but not in the normal mammary epithelial cell line MCF10A1. Use of FASN inhibitor, Orlistat, at low concentrations also sensitized cells with FASN overexpression to anticancer drugs. The FASN-mediated drug resistance appears to be due to a decrease in drug-induced apoptosis from an overproduction of palmitic acid by FASN. Together with previous findings of FASN as a poor prognosis marker for breast cancer patients, our results suggest that FASN overexpression is a new mechanism of drug resistance and may be an ideal target for chemosensitization in breast cancer chemotherapy.     

外泌体与卵巢癌耐药关系的研究进展

卵巢癌是女性生殖系统中恶性程度最高的肿瘤,目前化疗是其主要治疗方法之一,然而化疗药物的长期使用通常会引起卵巢癌的耐药性,从而导致治疗的失败。卵巢癌耐药机制及逆转耐药策略抑制是卵巢癌治疗研究的热点。外泌体是由细胞分泌的直径为40～100 nm的球形囊泡,其携带多种生物活性分子(如DNA、非编码RNA、蛋白质等)调控多种生理和病理活动。本文就外泌体与卵巢癌耐药的关系及其机制进行综述,以期为卵巢癌耐药的预防和治疗提供新思路。     

Dual targeting of EGFR can overcome a major drug resistance mutation in mouse models of EGFR mutant lung cancer

EGFR is a major anticancer drug target in human epithelial tumors. One effective class of agents is the tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib. These drugs induce dramatic responses in individuals with lung adenocarcinomas characterized by mutations in exons encoding the EGFR tyrosine kinase domain, but disease progression invariably occurs. A major reason for such acquired resistance is the outgrowth of tumor cells with additional TKI-resistant EGFR mutations. Here we used relevant transgenic mouse lung tumor models to evaluate strategies to overcome the most common EGFR TKI resistance mutation, T790M. We treated mice bearing tumors harboring EGFR mutations with a variety of anticancer agents, including a new irreversible EGFR TKI that is under development (BIBW-2992) and the EGFR-specific antibody cetuximab. Surprisingly, we found that only the combination of both agents together induced dramatic shrinkage of erlotinib-resistant tumors harboring the T790M mutation, because together they efficiently depleted both phosphorylated and total EGFR. We suggest that these studies have immediate therapeutic implications for lung cancer patients, as dual targeting with cetuximab and a second-generation EGFR TKI may be an effective strategy to overcome T790M-mediated drug resistance. Moreover, this approach could serve as an important model for targeting other receptor tyrosine kinases activated in human cancers.     

Therapeutic interactions between stathmin inhibition and chemotherapeutic agents in prostate cancer

Limitations of prostate cancer therapy may be overcome by combinations of chemotherapeutic agents with gene therapy directed against specific proteins critical for disease progression. Stathmin is overexpressed in many types of human cancer, including prostate cancer. Stathmin is one of the key regulators of the microtubule network and the mitotic spindle and provides an attractive therapeutic target in cancer therapy. We recently showed that adenovirus-mediated gene transfer of anti-stathmin ribozyme could suppress the malignant phenotype of prostate cancer cells in vitro. In the current studies, we asked whether the therapeutic effects of stathmin inhibition could be further enhanced by exposure to different chemotherapeutic agents. Exposure of uninfected LNCaP human prostate cancer cells or cells infected with a control adenovirus to Taxol, etoposide, 5-fluorouracil (5-FU), or Adriamycin resulted in modest decrease in proliferation and clonogenicity. Interestingly, exposure of cells infected with an anti-stathmin adenovirus to Taxol or etoposide resulted in a complete loss of proliferation and clonogenicity, whereas exposure of the same cells to 5-FU or Adriamycin potentiated the growth-inhibitory effects of the anti-stathmin ribozyme, but the cells continued to proliferate. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling analysis of uninfected cells or cells infected with a control adenovirus showed modest induction of apoptosis in the presence of different drugs. In contrast, cells infected with the anti-stathmin adenovirus showed a marked increase in apoptosis on exposure to Taxol or etoposide and a modest increase on exposure to 5-FU or Adriamycin. Overall, the effects of combinations of anti-stathmin ribozyme with Taxol or etoposide were synergistic, whereas the effects of combinations of anti-stathmin ribozyme with 5-FU or Adriamycin were additive. Moreover, triple combination of anti-stathmin ribozyme with low noninhibitory concentrations of Taxol and etoposide resulted in a profound synergistic inhibition of proliferation, clonogenicity, and marked induction of apoptosis. This synergy might be very relevant for the treatment of prostate cancer because Taxol and etoposide are two of the most effective agents in this disease. Thus, this combination may provide a novel form of prostate cancer therapy that would avoid toxicities associated with the use of multiple chemotherapeutic agents at full therapeutic doses.     

Doxorubicin loaded iron oxide nanoparticles overcome multidrug resistance in cancer in vitro

Multidrug resistance (MDR) is characterized by the overexpression of ATP-binding cassette (ABC) transporters that actively pump a broad class of hydrophobic chemotherapeutic drugs out of cancer cells. MDR is a major mechanism of treatment resistance in a variety of human tumors, and clinically applicable strategies to circumvent MDR remain to be characterized. Here we describe the fabrication and characterization of a drug-loaded iron oxide nanoparticle designed to circumvent MDR. Doxorubicin (DOX), an anthracycline antibiotic commonly used in cancer chemotherapy and substrate for ABC-mediated drug efflux, was covalently bound to polyethylenimine via a pH sensitive hydrazone linkage and conjugated to an iron oxide nanoparticle coated with amine terminated polyethylene glycol. Drug loading, physiochemical properties and pH lability of the DOX-hydrazone linkage were evaluated in vitro. Nanoparticle uptake, retention, and dose-dependent effects on viability were compared in wild-type and DOX-resistant ABC transporter over-expressing rat glioma C6 cells. We found that DOX release from nanoparticles was greatest at acidic pH, indicative of cleavage of the hydrazone linkage. DOX-conjugated nanoparticles were readily taken up by wild-type and drug-resistant cells. In contrast to free drug, DOX-conjugated nanoparticles persisted in drug-resistant cells, indicating that they were not subject to drug efflux. Greater retention of DOX-conjugated nanoparticles was accompanied by reduction of viability relative to cells treated with free drug. Our results suggest that DOX-conjugated nanoparticles could improve the efficacy of chemotherapy by circumventing MDR.     

Functional drug-gene interactions in lung cancer

Despite the dawn of the genomic information era, the challenges of cancer treatment remain formidable. Particularly for the most prevalent cancer types, including lung cancer, successful treatment of metastatic disease is rare and escalating costs for modern targeted drugs place an increasing strain on healthcare systems. Although powerful diagnostic tools to characterize individual tumor samples in great molecular detail are becoming rapidly available, the transformation of this information into therapy provides a major challenge. A fundamental difficulty is the molecular complexity of cancer cells that often causes drug resistance, but can also render tumors exquisitely sensitive to targeted agents. By using lung cancer as an example, we outline the principles that govern drug sensitivity and resistance from a genetic perspective and discuss how in vitro chemical-genetic screens can impact on patient stratification in the clinic.     

妇科肿瘤铂类药物临床应用指南

铂类药物是作用机制独特的广谱抗肿瘤药物,以铂类药物为基础的联合化疗是妇科肿瘤最常用的化疗方案。紫杉醇联合卡铂方案是上皮性卵巢癌的首选标准方案,顺铂是子宫颈癌的首选铂类药物。耐药是铂类药物临床应用中面临的最大挑战,此外,应积极预防和处理铂类药物不良反应及过敏反应。《妇科肿瘤铂类药物临床应用指南》旨在规范铂类药物的临床用药方案及用药后管理。