Common Mechanism Of Drug Resistance Research Articles

An Anaplastic Lymphoma Kinase-positive Inflammatory Myofibroblastic Tumor with Rapidly Acquired Resistance to First-line Anaplastic Lymphoma Kinase Inhibitor: A Case and Literature Review

Abstract Inflammatory myofibroblastic tumors (IMTs) are soft-tissue neoplasms with rare metastatic potential. Approximately half of IMTs are positive for an anaplastic lymphoma kinase (ALK) gene rearrangement which causes aberrant expression. Early phase clinical trials have demonstrated the efficacy of ALK inhibitors in the treatment of IMTs. However, there is no definite conclusion on which ALK inhibitor performs best, and data regarding subsequent therapy after first-line ALK inhibitor failure are scarce. Here, we report a case of ALK+ metastatic IMT that demonstrated a dramatic response to first-line alectinib but resulted in rapidly acquired resistance. Repeated biopsy and next-generation sequencing (NGS) showed ALK:c.3604G>A; p.(Gly1202Arg), which is a common mechanism of drug resistance in ALK fusion-positive non-small cell lung cancer. We also report subsequent treatment choices and responses in this patient and perform a literature review regarding similar cases as this rare tumor.

Drug resistance in glioblastoma: from chemo- to immunotherapy.

As the most common and aggressive type of primary brain tumor in adults, glioblastoma is estimated to end over 10,000 lives each year in the United States alone. Stand treatment for glioblastoma, including surgery followed by radiotherapy and chemotherapy (i.e., Temozolomide), has been largely unchanged since early 2000. Cancer immunotherapy has significantly shifted the paradigm of cancer management in the past decade with various degrees of success in treating many hematopoietic cancers and some solid tumors, such as melanoma and non-small cell lung cancer (NSCLC). However, little progress has been made in the field of neuro-oncology, especially in the application of immunotherapy to glioblastoma treatment. In this review, we attempted to summarize the common drug resistance mechanisms in glioblastoma from Temozolomide to immunotherapy. Our intent is not to repeat the well-known difficulty in the area of neuro-oncology, such as the blood-brain barrier, but to provide some fresh insights into the molecular mechanisms responsible for resistance by summarizing some of the most recent literature. Through this review, we also hope to share some new ideas for improving the immunotherapy outcome of glioblastoma treatment.

Therapeutic targeting of glutamate dehydrogenase 1 that links metabolic reprogramming and Snail-mediated epithelial–mesenchymal transition in drug-resistant lung cancer

Acquired drug resistance and epithelial–mesenchymal transition (EMT) mediated metastasis are two highly interacting determinants for non-small-cell lung cancer (NSCLC) prognosis. This study investigated the common mechanisms of drug resistance and EMT from the perspective of metabolic reprogramming, which may offer new ideas to improve anticancer therapy. Acquired resistant cells were found to grow faster and have a greater migratory and invasive capacity than their parent cells. Metabolomics analysis revealed that acquired resistant cells highly relied on glutamine utilization and mainly fluxed into oxidative phosphorylation energy production. Further mechanistic studies screened out glutamate dehydrogenase 1 (GLUD1) as the determinant of glutamine addiction in acquired resistant NSCLC cells, and provided evidence that GLUD1-mediated α-KG production and the accompanying reactive oxygen species (ROS) accumulation primarily triggered migration and invasion by inducing Snail. Pharmacological and genetic interference with GLUD1 in vitro significantly reversed drug resistance and decreased cell migration and invasion capability. Lastly, the successful application of R162, a selective GLUD1 inhibitor, to overcome both acquired resistance and EMT-induced metastasis in vivo, identified GLUD1 as a promising and druggable therapeutic target for malignant progression of NSCLC. Collectively, our study offers a potential strategy for NSCLC therapy, especially for drug-resistant patients with highly expressed GLUD1.

Epigenetic Regulation of Antifungal Drug Resistance.

In medical mycology, epigenetic mechanisms are emerging as key regulators of multiple aspects of fungal biology ranging from development, phenotypic and morphological plasticity to antifungal drug resistance. Emerging resistance to the limited therapeutic options for the treatment of invasive fungal infections is a growing concern. Human fungal pathogens develop drug resistance via multiple mechanisms, with recent studies highlighting the role of epigenetic changes involving the acetylation and methylation of histones, remodeling of chromatin and heterochromatin-based gene silencing, in the acquisition of antifungal resistance. A comprehensive understanding of how pathogens acquire drug resistance will aid the development of new antifungal therapies as well as increase the efficacy of current antifungals by blocking common drug-resistance mechanisms. In this article, we describe the epigenetic mechanisms that affect resistance towards widely used systemic antifungal drugs: azoles, echinocandins and polyenes. Additionally, we review the literature on the possible links between DNA mismatch repair, gene silencing and drug-resistance mechanisms.

Mechanisms and pathogenicity of the PI3K pathway: from basic research to clinical application

PI3K signaling pathway is one of the most important signaling pathways in tumorigenesis. Dysfunction of PI3K signalling pathway has been widely found in lymphatic hematologic tumors and solid tumors. Different PI3K inhibitors have shown anti-tumor activity against a variety of tumors. Furthermore, the FDA has approved various PI3K inhibitors for marketing or clinical studies, and have achieved considerable efficacy, especially in lymphoma and breast cancer. However, drug resistance and treatment-related adverse reactions remain unsolved. The PI3K signaling pathway also involves several other physiological functions related signaling pathway networks, and the combination therapy of selective inhibition of these signaling pathways needs to be further explored. New strategies include the combination of allosteric inhibitors and orthosteric inhibitors of PI3Kα and the development of inhibitors of salvage mutation sites. This review summarizes the clinical research progress and common drug resistance mechanisms of various common malignancies involved in PI3K inhibitors. In addition to targeting cancer cells, PI3K inhibitors also have great potential in cancer immunotherapy in the future.

Specificity of Binding and Antitumor Efficacy of a Covalent Microtubule Stabilizer

Microtubule stabilizers, including the taxanes paclitaxel and docetaxel, are a mainstay in the treatment of solid tumors, including breast and ovarian cancers. Although these agents are often effective as first‐line therapy, they are susceptible to common drug resistance mechanisms, including the upregulation of drug efflux pumps. Therefore, there is a critical need to develop novel classes of microtubule targeted agents that retain activity in taxane‐resistant settings. The C22,23‐epoxy taccalonolides are a class of plant‐derived microtubule stabilizers that covalently and irreversibly bind microtubules, allowing them to retain efficacy in a variety of taxane‐resistant cancer models. We employed cellular‐based binding studies to fully map the taccalonolide pharmacophore and confirm the target specificity of this covalent compound. The identification of β‐tubulin residues that are critical for taccalonolide binding in a cellular context has provided the opportunity to generate functional taccalonolide mimetics through a synthetically tractable approach.Herein, we demonstrate that taccalonolide AF is less susceptible to p‐glycoprotein‐mediated drug efflux than paclitaxel in two separate ovarian cancer models and that it has superior cellular persistence after drug washout, likely due to irreversible target engagement. While taccalonolide AF demonstrated potent and persistent in vivo antitumor efficacy against the taxane‐resistant NCI/ADR‐RES ovarian cancer model as a flank xenograft when administered systemically, it was associated with a narrow therapeutic window. Additional studies showing that intratumoral injection of the taccalonolides into flank tumors provided long‐term antitumor efficacy months after the final dose prompted a study of their utility in the targeted delivery to a disseminated orthotopic ovarian cancer model representing localized metastasis. Indeed, we found that taccalonolide‐treated animals showed a significant decrease in micrometastasis of taxane‐resistant ovarian cancer cells to the spleen, as detected by quantitative RT‐PCR, without any evidence of systemic toxicity. We propose that the irreversible mechanism of microtubule stabilization elicited by the taccalonolides has the unique potential for intraperitoneal treatment of locally disseminated taxane‐resistant disease, which represents a significant unmet clinical need in the treatment of ovarian cancer patients.

Identifying and overcoming a mechanism of resistance to WEE1 kinase inhibitor AZD1775 in high grade serous ovarian cancer cells

Objective: As a result of TP53 gene mutation high grade serous ovarian cancer (HGSOC) is dependent on the G2 checkpoint for the repair of DNA damage and survival. The key role of WEE1 kinase at this checkpoint makes inhibition of WEE1 kinase in combination with DNA damaging agents an attractive therapeutic strategy for HGSOC. Our aim was to characterise resistance mechanisms to WEE1 inhibitor AZD1775 and identify ways to overcome resistance ready for use in the clinic. Methods: AZD1775-resistant HGSOC cell clones were isolated and western blotting, cell cycle analysis, growth assays, RNA-Seq and gene expression analysis were used to characterise resistance mechanisms and investigate a way to overcome resistance. Results: A resistance mechanism previously reported in small cell lung cancer did not operate in HGSOC. Instead, resistance resulted from different cell cycle control pathway changes that slow AZD1775-induced cell cycle progression and reduce accumulation of replication associated DNA damage. One major change was reduced levels of CDK1, the substrate for WEE1 kinase inhibition; another was increased levels of PKMYT1, which can also inhibit CDK1. Increased expression of TGFβ signalling to slow cell cycle progression occurred in resistant clones. A TGFβR1 inhibitor overcame resistance in a clone with the highest TGFβR1 receptor expression. Conclusions: Although overexpression of the membrane glycoprotein MDR1 is a common mechanism of drug resistance, it was not involved in our HGSOC cells. Instead AZD1775 resistance resulted from cell cycle control pathway changes that combine to slow AZD1775-induced cell cycle progression and so reduce accumulation of replication-associated DNA damage.

Structural Optimization and Enhanced Prodrug-Mediated Delivery Overcomes Camptothecin Resistance in High-Risk Solid Tumors.

Camptothecins are potent topoisomerase I inhibitors used to treat high-risk pediatric solid tumors, but they often show poor efficacy due to intrinsic or acquired chemoresistance. Here, we developed a multivalent, polymer-based prodrug of a structurally optimized camptothecin (SN22) designed to overcome key chemoresistance mechanisms. The ability of SN22 vs. SN38 (the active form of irinotecan/CPT-11) to overcome efflux pump-driven drug resistance was tested. Tumor uptake and biodistribution of SN22 as a polymer-based prodrug (PEG-[SN22]4) compared with SN38 was determined. The therapeutic efficacy of PEG-[SN22]4 to CPT-11 was compared in: (i) spontaneous neuroblastomas (NB) in transgenic TH-MYCN mice; (ii) orthotopic xenografts of a drug-resistant NB line SK-N-BE(2)C (mutated TP53); (iii) flank xenografts of a drug-resistant NB-PDX; and (iv) xenografts of Ewing sarcoma and rhabdomyosarcoma. Unlike SN38, SN22 inhibited NB cell growth regardless of ABCG2 expression levels. SN22 prodrug delivery resulted in sustained intratumoral drug concentrations, dramatically higher than those of SN38 at all time points. CPT-11/SN38 treatment had only marginal effects on tumors in transgenic mice, but PEG-[SN22]4 treatment caused complete tumor regression lasting over 6 months (tumor free at necropsy). PEG-[SN22]4 also markedly extended survival of mice with drug-resistant, orthotopic NB and it caused long-term (6+ months) remissions in 80% to 100% of NB and sarcoma xenografts. SN22 administered as a multivalent polymeric prodrug resulted in increased and protracted tumor drug exposure compared with CPT-11, leading to long-term "cures" in NB models of intrinsic or acquired drug resistance, and models of high-risk sarcomas, warranting its further development for clinical trials. SIGNIFICANCE: SN22 is an effective and curative multivalent macromolecular agent in multiple solid tumor mouse models, overcoming common mechanisms of drug resistance with the potential to elicit fewer toxicities than most cancer therapeutics.

Mechanism of Histologic Transformation of Drive Gene Positive Lung Adenocarcinoma in Targeted Therapy and Treatment Strategy

驱动基因阳性的肺腺癌（adenocarcinoma, ADC）患者在接受靶向治疗一段时间后将不可避免地产生耐药。常见的耐药机制包括驱动基因的二次突变、非驱动基因的变异、病理类型转化和上皮间质转化等。其中病理类型转化包括肺ADC向小细胞肺癌（small cell lung cancer, SCLC）、鳞状细胞癌（squamous cell carcinoma, SCC）和大细胞神经内分泌癌（large cell neuroendocrine carcinoma, LCNEC）等病理类型发生转化。病理类型转化在降低患者生存质量的同时也对患者的后续治疗构成巨大的挑战，但目前对其机制的认知还不全面。本文将综述病理类型转化机制的研究成果以及治疗策略的选择。

Research progress in mechanisms for drug-resistance and recurrence in bladder cancer

Bladder cancer is a common malignant tumor in the urinary system, and its drug-resistant recurrence has become a major problem in clinical treatment. At present, there is still a lack of molecular markers for effectively predicting bladder cancer resistance. The mechanisms for drug resistance in bladder cancer is very complicated. The common mechanisms of drug resistance include epigenetic modification, abnormal expression level, abnormal regulation of non-coding RNA, production of bladder cancer stem cells, increase of drug efflux and autophagy. The various drug resistance mechanisms of bladder cancer are not independent, but there is a certain relationship between them, which leads to the occurrence of drug resistance. Further study on the mechanisms for bladder cancer resistance is of great importance to overcome these problems.

Abstract 4920: A status of re-biopsy for non-small-cell lung cancer patients after first EGFR-TKI failure and incidence of T790M mutation

Abstract Background: Among patients with advanced non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutation, T790M mutation is the most common mechanism of drug resistance to first- or second-generation EGFR tyrosine kinase inhibitors (TKIs). However, the proportion of patients with T790M mutation at re-biopsy is varied by studies or biopsy methods. Methods: A total of 126 patients who were treated with first- or second-generation EGFR TKIs and had disease progression in our institution from January 2017 to September 2018 were eligible for this study. We retrospectively evaluated re-biopsy methods and the proportion of patients who harbor T790M mutation. Result: A total of 126 patients (male, 36.5% ; median age, 69 year ) were included. Among 126 patients, 118 patients (93.7%) underwent re-biopsy by any methods: tissue biopsy or cytology sampling in 68 patients and plasma sampling in 50 patients during a first re-biopsy, and 44 patients (37.3%) had T790M mutation. During the first biopsy, in the 68 patients who underwent tissue biopsy or cytology sampling, 32 patients (47%) were positive for T790M mutation, nevertheless there were no tumor samples in 4 patients and only atypical cells in 3 patients and 1 patient was identified transformation to SCLC. In the 50 patients who performed plasma sampling during a first re-biopsy, T790M mutation was detected in only 12 patients (24%). Second re-biopsy was conducted in 19 patients among 74 patients resulted in T790M-negative or unknown after the first re-biopsy, and 10 patients were positive for T790M mutation. Eventually, a total of 80 patients were performed tissue biopsy or cytology sampling, 74 patients (96.1%) were found to have any EGFR mutations and T790M mutation was detected in 39 patients (48.1%). On the other hand, 59 patients underwent plasma sampling and 31 patients (52.5%) were found to have any EGFR mutations and T790M mutation was detected in only 17 patients (28.8%). Totally 54 patients (42.9%) were detected T790M mutation, and 52 patients (41.3%) received Osimertinib subsequently. Conclusion: After progression of first- or second-generation EGFR-TKIs, about 95% of patients underwent re-biopsy, and T790M mutation was present in approximately half of patients who underwent re-biopsy and almost all patients who were positive for T790M mutation could receive Osimertinib. In patients who underwent tissue biopsy or cytology sampling, high frequency of detecting any EGFR mutations contributed to higher detection rate of T790M mutation compared to plasma sampling. To improve the sensitivity for T790M mutation detection, tissue biopsy or cytology sampling should be performed if possible. Citation Format: Tetsuya Sakai, Hibiki Udagawa, Yoshitaka Zenke, Keisuke Kirita, Shigeki Umemura, Shingo Matsumoto, Kiyotaka Yoh, Seiji Niho, Genichiro Ishii, Koichi Goto. A status of re-biopsy for non-small-cell lung cancer patients after first EGFR-TKI failure and incidence of T790M mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4920.

Drugging drug resistance with bystander-assisted immunotherapy.

Abstract Acquired drug resistance is a longstanding challenge that reduces the efficacy of chemotherapeutic drugs. In contrast, the efficacies of modern immunotherapies do not directly correlate to the prevalence of chemo-resistant phenotypes. Here we improve upon this paradigm by targeting the action of immunotherapeutics to two general mechanisms of acquired drug resistance: irregular metabolism and drug efflux mediated by the ABC superfamily of transport proteins. In chemo-resistant prostate cancer cells, we demonstrate that these two mechanisms act in concert to selectively metabolize our newly developed class of enzyme-directed prodrug to the Toll-Like Receptor 7 immunotherapeutic Imiquimod. Following metabolism, liberated Imiquimod undergoes drug efflux to the extracellular space where it activates bystander immune cells in local proximity. In-vitro, we characterize this process of Bystander-Assisted ImmunoTherapy (BAIT) using an AT3B-1 chemo-resistant prostate cancer model with RAW-Blue and JAWSII reporter immune cell lines. Co-culture of AT3B-1 cancer cells with reporter immune cells results in immunogenicity mediated selectively by cancer cells. This results in enhanced NF-κB transcription, expression of cell surface markers, and secreted cytokines indicative of a cell-mediated immune response. Our prodrug is non-immunogenic with healthy cells alone and the enzyme-directing groups are stable for over 3 days in serum. Taken together, our results demonstrate that BAIT co-opts common mechanisms of drug resistance to elicit immunogenicity mediated by cancer cells themselves. We anticipate that BAIT will find use as a new mechanism of action that exploits drug resistant phenotypes to generate an immune response.

Advances in the Transformation to Small Cell Lung Cancer from Non-small Cell Lung Cancer Following Acquired Drug-resistance to EGFR Tyrosine Kinase Inhibitors

表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor tyrosine kinase inhibitors, EGFR TKIs）在治疗携带EGFR基因敏感突变的非小细胞肺癌（non-small cell lung cancer, NSCLC）中已取得显著疗效，但是，耐药的产生几乎是不可避免的，常见的耐药机制包括T790M突变、cMET基因扩增等。目前已有文献报道EGFR-TKI耐药的机制之一为NSCLC转化为小细胞肺癌（small cell lung cancer, SCLC），大约占3%-15%，是一种重要的少见耐药机制，并不为人们所深入了解。本文从“共同起源”和“转化时间节点”两个角度对其进行了归纳总结，重点探讨了其转化的可能机制，目前提出的两种可能转化机制分别为肿瘤异质性假说、NSCLC转化为SCLC假说，还涉及了许多分子水平的改变，如RB1基因缺失、P53基因失活、PTEN M264I基因突变等，同时对该种转化的发病特点、治疗策略等方面进行了归纳与总结。目前仍有许多问题需要进一步研究和解决。

P3.02b-101 EGFR T790M Resistance Mutation in NSCLC: Real-Life Data of Austrian Patients Treated with Osimertinib: Topic: EGFR RES

Somatic mutations in the epidermal growth factor receptor (EGFR) are detected in approximately 13% of the Austrian non-small cell lung cancer (NSCLC) patients. The EGFR T790M resistance mutation located on Exon 20 is the most common mechanism of drug resistance to EGFR tyrosine kinase inhibitors (TKI) in these patients. The mutation can be detected by re-biopsy as well liquid biopsy. Osimertinib (AZD9291), a 3rd generation EGFR-TKI, showed a highly clinical activity in these patients. We report about our experience with Osimertinib in EGFR-mutated NSCLC patients, who became resistant to first or second generation TKI's due to EGFR T790M mutation. From April 2015 to June 2016 we administered osimertinib 80 mg daily to 82 patients who had disease progression after previous treatment with an EFGR TKI. The T790M mutation status was assessed by re-biopsy and/or liquid biopsy. For liquid biopsies, blood samples were collected in EDTA-containing vacutainer tubes and processed within 2 hours after collection. Cell-free plasma DNA was extracted by using the QIAamp circulating nucleic acid kit (Qiagen) according to the manufacturer’s instructions. Mutation status was assessed with QX-100™ Droplet Digital™ PCR System (Bio-Rad). The T790M mutation status was assessed in 48 patients by liquid biopsy only and in 13 patients by re-biopsy of the tumor. In 21 patients the T790M mutation was detected by both methods. 70 (85%) patients showed a clear clinical and radiographic response. Out of these, 70 patients, 14 (17%) patients reached a complete remission, 56 (68%) patients showed partial response and in 5 (6%) patients, a stable disease after treatment with osimertinib was observed. Five patients had symptomatic brain metastasis initially without any further option of local treatment, and showed a clear a clear clinical benefit and a partial remission radiographically. Osimertinib was well tolerated. No clinically relevant significant side effects were reported. Osimertinib was highly active in our patients, while showing good safety profile. Therefore, re-biopsy or liquid biopsy should be performed in clinical routine to detect the T790M mutation. With the above described method, liquid biopsy could replace re-biopsy in clinical practice in the future.

EGFR T790M resistance mutation in NSCLC: Real-life data of patients treated with osimertinib.

e20572Background: The EGFR T790M resistance mutation located on Exon 20 is the most common mechanism of drug resistance to EGFR tyrosine kinase inhibitors (TKI). The mutation can be detected by re-...

Efflux Pump Mediated Second-Line Tuberculosis Drug Resistance

The burden and spread of drug-resistant tuberculosis disease is a major public health problem worldwide. The causative agent, Mycobacterium tuberculosis uses several mechanisms to counteract therapy through drugresistance. A major and most common mechanism of drug-resistance is mediated through target mutations. Efflux pumps are emerging as potential agents of drug-resistance and treatment failure. In this review we explore the origin and principles of efflux pump-mediated resistance and determine their impact on second-line drugs used against extensively drug resistant tuberculosis. Inhibition of efflux pumps as a therapeutic intervention is also discussed.

AZD9291 in EGFR Inhibitor–Resistant Non–Small-Cell Lung Cancer

BackgroundThe EGFR T790M mutation is the most common mechanism of drug resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in patients who have lung cancer with an EGFR mutation (EGFR-mutated lung cancer). In preclinical models, the EGFR inhibitor AZD9291 has been shown to be effective against both EGFR tyrosine kinase inhibitor–sensitizing and T790M resistance mutations.MethodsWe administered AZD9291 at doses of 20 to 240 mg once daily in patients with advanced lung cancer who had radiologically documented disease progression after previous treatment with EGFR tyrosine kinase inhibitors. The study included dose-escalation cohorts and dose-expansion cohorts. In the expansion cohorts, prestudy tumor biopsies were required for central determination of EGFR T790M status. Patients were assessed for safety, pharmacokinetics, and efficacy.ResultsA total of 253 patients were treated. Among 31 patients enrolled in the dose-escalation cohorts, no dose-limiting toxic effects occurred at the doses evaluated. An additional 222 patients were treated in five expansion cohorts. The most common all-cause adverse events were diarrhea, rash, nausea, and decreased appetite. The overall objective tumor response rate was 51% (95% confidence interval [CI], 45 to 58). Among 127 patients with centrally confirmed EGFR T790M who could be evaluated for response, the response rate was 61% (95% CI, 52 to 70). In contrast, among 61 patients without centrally detectable EGFR T790M who could be evaluated for response, the response rate was 21% (95% CI, 12 to 34). The median progression-free survival was 9.6 months (95% CI, 8.3 to not reached) in EGFR T790M–positive patients and 2.8 months (95% CI, 2.1 to 4.3) in EGFR T790M–negative patients.ConclusionsAZD9291 was highly active in patients with lung cancer with the EGFR T790M mutation who had had disease progression during prior therapy with EGFR tyrosine kinase inhibitors. (Funded by AstraZeneca; ClinicalTrials.gov number, NCT01802632.)

Poly(2-oxazoline) based micelles with high capacity for 3rd generation taxoids: Preparation, in vitro and in vivo evaluation

The clinically and commercially successful taxanes, paclitaxel and docetaxel suffer from two major drawbacks, namely their very low aqueous solubility and the risk of developing resistance. Here, we present a method that overcomes both drawbacks in a very simple manner. We formulated 3rd generation taxoids, able to avoid common drug resistance mechanisms with doubly amphiphilic poly(2-oxazoline)s (POx), a safe and highly efficient polymer for the formulation of extremely hydrophobic drugs. We found excellent solubilization of different 3rd generation taxoids irrespective of the drug's chemical structures with essentially quantitative drug loading and final drug to polymer ratios around unity. The small, highly loaded micelles with a hydrodynamic diameter of less than 100nm are excellently suited for parenteral administration. Moreover, a selected formulation with the taxoid SB-T-1214 is about one to two orders of magnitude more active in vitro than paclitaxel in the multidrug resistant breast cancer cell line LCC6-MDR. In contrast, in wild-type LCC6, no difference was observed. Using a q4d×4 dosing regimen, we also found that POx/SB-T-1214 significantly inhibits the growth of LCC6-MDR orthotropic tumors, outperforming commercial paclitaxel drug Taxol and Cremophor EL formulated SB-T-1214.

Overexpression of human ABCB1 in cancer cells leads to reduced activity of GSK461364, a specific inhibitor of polo-like kinase 1.

Polo-like kinase 1 (Plk1) is a serine/threonine kinase involved in the regulation of mitosis and is overexpressed in many tumor types. Inhibition of Plk1 leads to cell cycle arrest, onset of apoptosis, and cell death, thus Plk1 has emerged as an important target for cancer treatment. GSK461364 is a potent inhibitor of Plk1 that inhibits the proliferation of multiple human cancer cell lines by promoting G2/M cell cycle arrest at low concentrations. However, as is the case for many therapeutic drugs, the risk of developing drug resistance to GSK461364 can present a therapeutic challenge to clinicians. Since the overexpression of ATP-binding cassette (ABC) drug transporter ABCB1 is one of the most common mechanisms of drug resistance, we aimed to investigate the effect of ABCB1 on the cellular efficacy of GSK461364. In this study, we observed a significantly reduced activity of GSK461364 in cells overexpressing human ABCB1. We showed that GSK461364 stimulates the ABCB1 ATPase activity and competitively inhibits ABCB1-mediated efflux of calcein-AM in a concentration-dependent manner. Moreover, as a way to assess the impact of ABCB1 on the efficacy of GSK461364, we evaluated the G2/M cell cycle arrest and apoptosis induced by GSK461364. We discovered that, by inhibiting the function of ABCB1, the reduced G2/M cell cycle arrest, apoptosis, and sensitivity to GSK461364 treatment in ABCB1-overexpressing cells can be significantly restored. In conclusion, in order to achieve a better therapeutic outcome, combination therapy of GSK461364 with a modulator of ABCB1 should be further investigated as a potential treatment approach.

Prevalence of extended-spectrum β-lactamase-producing Enterobacteriaceae in Menoufia University Hospitals

Objective The aim of the study was to evaluate the prevalence of extended-spectrum β-lactamase (ESBLs) in Enterobacteriaceae among patients conducted at Menoufia University Hospitals. Background Resistance to β-lactam antibiotics is an increasing problem, and β-lactamase production is the most common mechanism of drug resistance, especially in Enterobacteriaceae. The Clinical and Laboratory Standard Institute (CLSI) interpretive guidelines stated that Enterobacteriaceae that produce ESBLs are resistant to therapy with penicillin, cephalosporins, and aztreonam, despite apparent in-vitro susceptibility to some of these agents. Therefore, detection of ESBLs in Enterobacteriaceae is crucial for optimal treatment of patients and to control the spread of resistance. Patients and methods The isolated strains of Enterobacteriaceae are subjected to phenotype detection by screening for ESBLs by disk diffusion test then to confirmatory tests for ESBLs by double disk test. Results A total of 97 of 160 (60.6%) isolates were found to be ESBL producers by the CLSI confirmatory method. Of 97 ESBL producers, 45 (46.4%) were Escherichia coli , 28 (28.9%) were Enterobacter spp., and 22 (22.7%) were Klebsiella spp. Of the various clinical samples, the most frequent ESBLs isolates were from urine samples (27.8%), followed by sputum samples (18.6%). Conclusion High prevalence of ESBL producers in our hospital (60.6%) calls for strict policies regarding antibiotic usage and their screening methods, and hospital-based clinical laboratories should screen isolates following hospitalization in patients in need for antibiotics to formulate effective antibiotic strategy and plan a proper hospital infection control strategy to prevent the spread of these ESBL strains.