Mechanisms Of Drug Resistance In Cancer Research Articles

Carbon nano-onion-mediated dual targeting of P-selectin and P-glycoprotein to overcome cancer drug resistance

The transmembrane P-glycoprotein (P-gp) pumps that efflux drugs are a major mechanism of cancer drug resistance. They are also important in protecting normal tissue cells from poisonous xenobiotics and endogenous metabolites. Here, we report a fucoidan-decorated silica-carbon nano-onion (FSCNO) hybrid nanoparticle that targets tumor vasculature to specifically release P-gp inhibitor and anticancer drug into tumor cells. The tumor vasculature targeting capability of the nanoparticle is demonstrated using multiple models. Moreover, we reveal the superior light absorption property of nano-onion in the near infrared region (NIR), which enables triggered drug release from the nanoparticle at a low NIR power. The released inhibitor selectively binds to P-gp pumps and disables their function, which improves the bioavailability of anticancer drug inside the cells. Furthermore, free P-gp inhibitor significantly increases the systemic toxicity of a chemotherapy drug, which can be resolved by delivering them with FSCNO nanoparticles in combination with a short low-power NIR laser irradiation.

In vitro 3D Systems to Model Tumor Angiogenesis and Interactions With Stromal Cells.

In vitro 3D culture systems provide promising tools for screening novel therapies and understanding drug resistance mechanisms in cancer because they are adapted for high throughput analysis. One of the main current challenges is to reproducibly culture patient samples containing cancer and stromal cells to faithfully recapitulate tumor microenvironment and move toward efficient personalized medicine. Tumors are composed of heterogeneous cell populations and characterized by chaotic vascularization in a remodeled microenvironment. Indeed, tumor angiogenesis occurs in a complex stroma containing immune cells and cancer-associated fibroblasts that secrete important amounts of cytokines, growth factors, extracellular vesicles, and extracellular matrix (ECM). This process leads to the formation of inflated, tortuous, and permeable capillaries that display deficient basement membrane (BM) and perivascular coverage. These abnormal capillaries affect responses to anti-cancer therapies such as anti-angiogenic, radio-, and immunotherapies. Current pre-clinical models are limited for investigating interactions between tumor cells and vascularization during tumor progression as well as mechanisms that lead to drug resistance. In vitro approaches developed for vascularization are either the result of engineered cell lining or based on physiological processes including vasculogenesis and sprouting angiogenesis. They allow investigation of paracrine and direct interactions between endothelial and tumor and/or stromal cells, as well as impact of biochemical and biophysical cues of the microenvironment, using either natural matrix components or functionalized synthetic hydrogels. In addition, microfluidic devices provide access to modeling the impact of shear stress and interstitial flow and growth factor gradients. In this review, we will describe the state of the art co-culture models of vascularized micro-tumors in order to study tumor progression and metastatic dissemination including intravasation and/or extravasation processes.

Nanoparticle-Based Drug Delivery in Cancer Therapy and Its Role in Overcoming Drug Resistance.

Nanotechnology has been extensively studied and exploited for cancer treatment as nanoparticles can play a significant role as a drug delivery system. Compared to conventional drugs, nanoparticle-based drug delivery has specific advantages, such as improved stability and biocompatibility, enhanced permeability and retention effect, and precise targeting. The application and development of hybrid nanoparticles, which incorporates the combined properties of different nanoparticles, has led this type of drug-carrier system to the next level. In addition, nanoparticle-based drug delivery systems have been shown to play a role in overcoming cancer-related drug resistance. The mechanisms of cancer drug resistance include overexpression of drug efflux transporters, defective apoptotic pathways, and hypoxic environment. Nanoparticles targeting these mechanisms can lead to an improvement in the reversal of multidrug resistance. Furthermore, as more tumor drug resistance mechanisms are revealed, nanoparticles are increasingly being developed to target these mechanisms. Moreover, scientists have recently started to investigate the role of nanoparticles in immunotherapy, which plays a more important role in cancer treatment. In this review, we discuss the roles of nanoparticles and hybrid nanoparticles for drug delivery in chemotherapy, targeted therapy, and immunotherapy and describe the targeting mechanism of nanoparticle-based drug delivery as well as its function on reversing drug resistance.

Therapeutic Targeting of MDR1 Expression by RORγ Antagonists Resensitizes Cross-Resistant CRPC to Taxane via Coordinated Induction of Cell Death Programs.

Overexpression of ATP-binding cassette subfamily B member 1 (ABCB1)-encoded multidrug resistance protein 1 (MDR1) constitutes a major mechanism of cancer drug resistance including docetaxel (DTX) and cabazitaxel (CTX) resistance in castration-resistant prostate cancer (CRPC). However, no therapeutics that targets MDR1 is available at clinic for taxane sensitization. We report here that retinoic acid receptor-related orphan receptor γ (RORγ), a nuclear receptor family member, unexpectedly mediates MDR1/ABCB1 overexpression. RORγ plays an important role in controlling the functions of subsets of immune cells and has been an attractive target for autoimmune diseases. We found that its small-molecule antagonists are efficacious in resensitizing DTX and CTX cross-resistant CRPC cells and tumors to taxanes in both androgen receptor-positive and -negative models. Our mechanistic analyses revealed that combined treatment with RORγ antagonists and taxane elicited a robust synergy in killing the resistant cells, which involves a coordinated alteration of p53, Myc, and E2F-controlled programs critical for both intrinsic and extrinsic apoptosis, survival, and cell growth. Our results suggest that targeting RORγ with small-molecule inhibitors is a novel strategy for chemotherapy resensitization in tumors with MDR1 overexpression.

The Emerging Role of the SLCO1B3 Protein in Cancer Resistance.

Currently, chemotherapy is one of the mainstays of oncologic therapies. But the efficacy of chemotherapy is often limited by drug resistance and severe side effects. Consequently, it is becoming increasingly important to investigate the underlying mechanism and overcome the problem of anticancer chemotherapy resistance. The solute carrier organic anion transporter family member 1B3 (SLCO1B3), a functional transporter normally expressed in the liver, transports a variety of endogenous and exogenous compounds, including hormones and their conjugates as well as some anticancer drugs. The extrahepatic expression of SLCO1B3 has been detected in different cancer cell lines and cancer tissues. Recently, accumulating data indicates that the abnormal expression and function of SLCO1B3 are involved in resistance to anticancer drugs, such as taxanes, camptothecin and its analogs, SN-38, and Androgen Deprivation Therapy (ADT) in breast, prostate, lung, hepatic, and colorectal cancer, respectively. Thus, more investigations have been implemented to identify the potential SLCO1B3-related mechanisms of cancer drug resistance. In this review, we focus on the emerging roles of SLCO1B3 protein in the development of cancer chemotherapy resistance and briefly discuss the mechanisms of resistance. Elucidating the function of SLCO1B3 in chemoresistance may bring out novel therapeutic strategies for cancer treatment.

A Combination Strategy Targeting Enhancer Plasticity Exerts Synergistic Lethality Against Beti-Resistant Leukemia Cells

Primary and acquired drug resistance is a major challenge to achieving optimized clinical outcomes during cancer treatment which can arise from transcription reactivation, bypass and alteration during anticancer treatment [1-3]. Epigenetic dysregulation is emerging as a crucial component involved in drug resistance. Transcriptional adaptation during drug treatment is often mediated by inducible histone modifications, especially histone H3 lysine 27 acetylation (H3K27ac) at the distal enhancer elements, thus activating the transcription of drug resistance-associated genes [4-6]. BRD4 (bromodomain-containing protein 4), a member of the bromodomain and extra-terminal domain (BET) family, acts as a chromatin reader to regulate transcription by linking histone acetylation and core components of the transcriptional apparatus [7]. BET inhibitors (BETi), as exemplified by JQ1 and I-BET151, have been shown to suppress the growth of multiple types of tumor both in vitro and in vivo [8]. However, drug resistance associated with BETi becomes one of the major hurdles hampering the clinical applications of these promising drug candidates [8, 9]. Using BET inhibitor (BETi) resistant leukemia cells as a model system, we demonstrated herein that genome-wide enhancer remodeling played a pivotal role in driving therapeutic resistance via compensational re-expression of pro-survival genes. Capitalizing on CRISPR interference, we identified the second intron of IncRNA, PVT1, as a unique bona fidegained enhancer that restored MYCtranscription independent of BRD4 recruitment. A combined BETi and CDK7 inhibitor treatment abolished MYC transcription by impeding RNAPII loading without affecting PVT1-mediated chromatin looping at the MYClocus in BETi-resistant leukemia cells. Furthermore, recipient mice transferred with BETi-resistant murine MLL-AF9 AML cells receiving the combination treatment showed the most effective therapeutic outcomes, as characterized by prolonged overall survival and reduced tumor burdens in the spleen and bone marrow. Together, our findings have established the feasibility of targeting enhancer plasticity to overcome drug resistance associated with epigenetic therapies.

Personalized Drug Efficacy Monitoring Chip.

Cancer drug resistance mechanisms such as tumor heterogeneity and adaptable feedback loops are prevalent issues facing cancer therapy development. Drug resistance can be unique to a cancer type and, most importantly, to each individual cancer patient. Consequently, testing different dosages and therapeutics directly on each individual patient sample (i.e., tumor and cancer cells) has compelling advantages compared to large scale in vitro drug testing and is a step toward personalized drug selection and effective treatment development. Recently, microfluidic-based chemo-sensitivity assays on patient biopsies have been proposed. Despite their novelty, these platforms usually rely on optical labels, optical equipment, or complex microfabricated channel geometries and structures. In this work, we proposed a novel lab on a chip platform capable of real-time and continuous screening of drug efficacy on (cancer) cell subpopulations without the need of labels or bulky readout optical equipment. In this platform, several label-free and rapid techniques have been implemented for the precise capturing of cells of interest in parallel with the real-time measurement and characterization of the effectiveness of candidate therapeutic agents. To demonstrate the utility of the platform, the effect of an apoptotic inducer, topoisomerase I inhibitor, 7-ethyl-10-hydrocamptothecin (SN38) on human colorectal carcinoma cancer cells (HCT 116) was used as a study model. Additionally, electrical results were optically verified to examine the continuous measurements of the biological mechanisms, specifically, apoptosis and necrosis, during therapeutic agent characterizations. The proposed device is a versatile platform which can also be easily redesigned for the automated and arrayed analysis of cell-drug interaction down to the single cell level. Our platform is another step toward enabling the personalized screening of drug efficacy on individual patients' samples that potentially leads to a better understanding of drug resistance and the optimization of patients' treatments.

Differential regulatory network-based quantification and prioritization of key genes underlying cancer drug resistance based on time-course RNA-seq data.

Drug resistance is a major cause for the failure of cancer chemotherapy or targeted therapy. However, the molecular regulatory mechanisms controlling the dynamic evolvement of drug resistance remain poorly understood. Thus, it is important to develop methods for identifying key gene regulatory mechanisms of the resistance to specific drugs. In this study, we developed a data-driven computational framework, DryNetMC, using a differential regulatory network-based modeling and characterization strategy to quantify and prioritize key genes underlying cancer drug resistance. The DryNetMC does not only infer gene regulatory networks (GRNs) via an integrated approach, but also characterizes and quantifies dynamical network properties for measuring node importance. We used time-course RNA-seq data from glioma cells treated with dbcAMP (a cAMP activator) as a realistic case to reconstruct the GRNs for sensitive and resistant cells. Based on a novel node importance index that comprehensively quantifies network topology, network entropy and expression dynamics, the top ranked genes were verified to be predictive of the drug sensitivities of different glioma cell lines, in comparison with other existing methods. The proposed method provides a quantitative approach to gain insights into the dynamic adaptation and regulatory mechanisms of cancer drug resistance and sheds light on the design of novel biomarkers or targets for predicting or overcoming drug resistance.

Major obstacles to doxorubicin therapy: Cardiotoxicity and drug resistance.

Doxorubicin is one of the most commonly prescribed and time-tested anticancer drugs. Although being considered as a first line drug in different types of cancers, the two main obstacles to doxorubicin therapy are drug-induced cardiotoxicity and drug resistance. The study utilizes systemic reviews on publications of previous studies obtained from scholarly journal databases including PubMed, Medline, Ebsco Host, Google Scholar, and Cochrane. The study utilizes secondary information obtained from health organizations using filters and keywords to sustain information relevancy. The study utilizes information retrieved from studies captured in the peer-reviewed journals on "doxorubicin-induced cardiotoxicity" and "doxorubicin resistance." The exact mechanisms of cardiotoxicity are not known; various hypotheses are studied. Doxorubicin can lead to free radical generation in various ways. The commonly proposed underlying mechanisms promoting doxorubicin resistance are the expression of multidrug resistance proteins as well as other causes. In this review, we have described the major obstacles to doxorubicin therapy, doxorubicin-induced cardiotoxicity as well as the mechanisms of cancer drug resistance and in following the treatment failures.

Limitations of molecularly targeted therapy

Personalized medicine is an extension of traditional medicine is based on a highly individual approach to each patient. One of the most important tools that allow this approach is targeted therapy. It focuses mainly on blocking cancer cell’s proliferation and angiogenesis capabilities by interfacing with specific molecules that are involved in the growth and progression of the tumour. Small-molecule inhibitors and monoclonal antibodies are the main drugs that are currently in use in order to affect the specific biochemical pathways in cancer cells. However, likewise any other cancer therapies, targeted therapy has its own limitations. For instance, identifying a molecular target needed to begin treatment is one of those hardships. A specific molecule is crucial in this way of treatment. The other limitation is the toxicity that appears during the treatment, the same as in the case of traditional chemotherapy and radiotherapy. Furthermore, the cost of this therapy is significantly higher compared to classical treatments. However, the main obstacles are mechanisms of cancer drug resistance which are often developing in response to given drugs. In many cases, it makes further treatment impossible. This article is focusing on the limitations of molecularly targeted therapy.

CDRgator: An Integrative Navigator of Cancer Drug Resistance Gene Signatures.

Understanding the mechanisms of cancer drug resistance is a critical challenge in cancer therapy. For many cancer drugs, various resistance mechanisms have been identified such as target alteration, alternative signaling pathways, epithelial–mesenchymal transition, and epigenetic modulation. Resistance may arise via multiple mechanisms even for a single drug, making it necessary to investigate multiple independent models for comprehensive understanding and therapeutic application. In particular, we hypothesize that different resistance processes result in distinct gene expression changes. Here, we present a web-based database, CDRgator (Cancer Drug Resistance navigator) for comparative analysis of gene expression signatures of cancer drug resistance. Resistance signatures were extracted from two different types of datasets. First, resistance signatures were extracted from transcriptomic profiles of cancer cells or patient samples and their resistance-induced counterparts for >30 cancer drugs. Second, drug resistance group signatures were also extracted from two large-scale drug sensitivity datasets representing ~1,000 cancer cell lines. All the datasets are available for download, and are conveniently accessible based on drug class and cancer type, along with analytic features such as clustering analysis, multidimensional scaling, and pathway analysis. CDRgator allows meta-analysis of independent resistance models for more comprehensive understanding of drug-resistance mechanisms that is difficult to accomplish with individual datasets alone (database URL: http://cdrgator.ewha.ac.kr).

MicroRNAs and cancer drug resistance: over two thousand characters in search of a role.

MicroRNAs (miRNAs), a group of small regulatory noncoding RNAs, transformed our thinking on gene regulation. More than two thousand human miRNAs have been identified thus far. These bind imperfectly to the 3’-untranslated region of target mRNA and have been involved in several pathological conditions including cancer. In fact, major hallmarks of cancer, such as the cell cycle, cell proliferation, survival and invasion are modulated by miRNAs. Cancer drug resistance (CDR) has also been described as being modulated by miRNAs. CDR remains a burden for cancer therapy and patients’ outcome, often resulting in more aggressive tumours that tend to metastasize to distant organs. In this review we discuss the role of miRNAs influencing drug metabolism and drug influx/efflux, two important mechanisms of CDR.

P2.13-34 Long Intergenic Non-Coding RNA 00665 Induces Acquired Resistance to Gefitinib in Non-Small-Cell Lung Cancer

Gefitinib, a tyrosine kinase inhibitor of epidermal growth factor receptor (EGFR-TKI), has been used as the first choice of treatment for advanced non-small cell lung cancer (NSCLC). However, during the course of treatment cancer cells often develop resistance to gefitinib without fully understood mechanisms. In recent years, numerous studies have shown that long non-coding RNAs (lncRNAs) play vital roles in modulating various biological processes, such as cell apoptosis, proliferation, migration, and invasion. Nevertheless cancer drug resistance mechanisms related to LncRNAs and their important roles in cancer development are still poorly understood. In this study, we aimed to elucidate an important role of long intergenic non-coding RNA 00665 (LINC00665) in developing resistance to gefitinib in NSCLC. Quantitative reverse transcription PCR (qRT-PCR) was performed to examine the expression levels of LINC00665 in 10 pairs of LUAD tissues from patients who had never been treated with gefitinib (NG) and those who were treated with gefitinib but developed resistance (GR). The effect of LINC00665 on proliferation and apoptosis in gefitinib-resistant cells was evaluated by CCK8, colony formation, flow-cytometric analysis and in vivo tumor formation assays. Western-blot and immunohistochemistry were used to evaluate the expression of EGFR and its downstream event. LINC00665 expression levels were significantly increased in NSCLC patients who developed acquired resistance to gefitinib compared to the NG group.Furthermore, LINC00665 inhibition reversed gefitinib sensitivity both in vitro and in vivo by suppressing cell growth and induced cell apoptosis. Importantly, knockdown of LINC00665 marked decreased activation of EGFR and its downstream event Akt and ERK1/2. Taken together,our study demonstrates that LINC00665 may be a potential biomarker of response to gefitinib as well as a novel therapeutic target for future treatment of NSCLC.

Time to tame necroptosis - viable combat against chemo resistant oral cancer cells.

Till 1998, a little was known about alternative forms of regulated cell death beside apoptosis. In present scenario, accumulating evidences suggest a form of programmed necrosis called Necroptosis which can be induced by various external stimuli including anticancer drugs, ionizing radiation, photodynamic therapy in the form of death domain receptor (DR) engagement by their respective ligands, TNF-alpha, Fas ligand (FasL) and TRAIL, under apoptosis deficient condition (caspase inhibitor), etc. receptor interacting protein-1 (RIP-1), a death domain containing kinase is the key molecule in necroptotic cell death pathway. On interaction with an additional protein RIP-3 to form an intracellular complex (complex-IIb), it triggers the various downstream mechanisms of necroptosis which includes: i) excessive production reactive oxygen species (ROS) as RIP-3 interacts with metabolic enzymes (glycogen phosphorylase, glutamate dehydrogenase) which increases the concentration of substrates for oxidative phophorylation - a major source of ROS; ii) mitochondrial dysfunction (mitrochondrial permeability transition ). Necrostatin (Nec-1) and CYLD act as negative and positive regulators for this mode of cell death.TNF the master pro-inflammatory cytokine has been known to either promote gene activation or to induce RIPK1 kinase-dependent cell death, in the form of apoptosis or necroptosis. Autophagy has also been proposed as an execution mechanism for necroptosis. There is growing evidence of impairment of necroptosis in tumerogenesis of various human cancers such as chronic lymphocytic leukemia, epidermal cancer and non Hodgkins lymphoma.As conventional anticancer drugs are usually apoptosis inducers, the development of apoptosis resistant cell clones is inevitable owing to cancer heterogeneity and mutation leading to failure of standard chemotherapy. It is a known fact that triggering necroptosis could be an alternative way to eradicate apoptosis-resistant cancer cells. Development of a new class of anticancer drug targeting this alternative pathway of the cell death is the need of the hour. Few in vitro and in vivo studies have been conducted showing excellent anti-tumor effect in both drug sensitive and resistant cases by targeting different modulators of necroptotic pathway: i) shikonin-a naturally occurring naphthoquinone showed prompt but profound anti-tumor effect on both primary and metastatic tumor i.e. cancer cell lines and osteosarcoma by inducing RIPK1 and RIPK3 dependent necroptosis; ii) staurosporine-generally accepted inducer of intrinsic apoptotic pathway and it is a wide spectrum inhibitor of protein kinases. It can induce necroptosis in caspase compromised conditions; iii) deoxypodophyllotoxin - a naturally occurring microtubule destabilizer successfully induced necroptosis in both drug sensitive and drug resistant cancer cell lines; iv) targeting Nec-1, a specific inhibitor of necroptosis can help in inducing necroptosis to enhance the radiosensitivity of cancer cells. Tanshinone IIA (Tan IIA) is known to induces both Nec-1 inhibition and FLIPS regulation-mediated apoptosis/necroptosis; v) obatoclax induces the interaction of p62 with RIP1K, RIP3K and FADD, key components of the necrosome and can mediate cell death in oral squamous cell carcinoma (OSCC) cells via autophagy-dependent necroptosis.Despite the rigorous implement of conventional therapies, increased number of refractory cases is unavoidable due to acquired resistance of cancer cells, badly affecting survival rate of OSCC. Additional knowledge about the mechanisms of cancer drug resistance and development of novel targeted therapy using alternative pathway of cell death and less susceptible to known resistance mechanisms i.e. necroptosis-based cancer therapy may help in designing effective anticancer strategies for OSCC .

The Different Mechanisms of Cancer Drug Resistance: A Brief Review.

Anticancer drugs resistance is a complex process that arises from altering in the drug targets. Advances in the DNA microarray, proteomics technology and the development of targeted therapies provide the new strategies to overcome the drug resistance. Although a design of the new chemotherapy agents is growing quickly, effective chemotherapy agent has not been discovered against the advanced stage of cancer (such as invasion and metastasis). The cancer cell resistance against the anticancer agents can be due to many factors such as the individual’s genetic differences, especially in tumoral somatic cells. Also, the cancer drug resistance is acquired, the drug resistance can be occurred by different mechanisms, including multi-drug resistance, cell death inhibiting (apoptosis suppression), altering in the drug metabolism, epigenetic and drug targets, enhancing DNA repair and gene amplification. In this review, we outlined the mechanisms of cancer drug resistance and in following, the treatment failures by common chemotherapy agents in the different type of cancers.

Cellular Prion Protein Enhances Drug Resistance of Colorectal Cancer Cells via Regulation of a Survival Signal Pathway.

Anti-cancer drug resistance is a major problem in colorectal cancer (CRC) research. Although several studies have revealed the mechanism of cancer drug resistance, molecular targets for chemotherapeutic combinations remain elusive. To address this issue, we focused on the expression of cellular prion protein (PrPC) in 5-FU-resistant CRC cells. In 5-FU-resistant CRC cells, PrPC expression is significantly increased, compared with that in normal CRC cells. In the presence of 5-FU, PrPC increased CRC cell survival and proliferation by maintaining the activation of the PI3K-Akt signaling pathway and the expression of cell cycle-associated proteins, including cyclin E, CDK2, cyclin D1, and CDK4. In addition, PrPC inhibited the activation of the stress-associated proteins p38, JNK, and p53. Moreover, after treatment of 5-FU-resistant CRC cells with 5-FU, silencing of PrPC triggered apoptosis via the activation of caspase-3. These results indicate that PrPC plays a key role in CRC drug resistance. The novel strategy of combining chemotherapy with PrPC targeting may yield efficacious treatments of colorectal cancer.

Cep70 drives taxol drug resistance through regulating the acetylation α-tubulin to reduce microtubule stability

Objective To explore the Cep70 by adjusting the stability of acetylated alpha tubulin, participate in breast cancer drug resistance mechanisms. Methods ⑴ In order to induce taxol drug resistance cell line Michigan cancer foundation-7 (MCF-7)/pac, high-dose shock treatments taxol MCF-7 was used for 6 months, until the cells can grow in 3.5 μmol/L of paclitaxel. ⑵ The 3-(4, 5-dimenthylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) method was used to detect inhibition rate by taxol to MCF-7 and MCF-7/pac cell. ⑶ Immunofluorescence and Western blot were used to test acetylated alpha-tubulin and Cep70 expression levels in MCF-7 and MCF-7/pac cells. ⑷ Chemical intervention was used to acetylate apha-tubulin expression, Western blot and polymerase chain reaction (PCR) were used to detect the change of acetylated alpha-tubulin and Cep70 in MCF-7 and MCF-7/pac groups. Flow cytometry and Western blot were used to detect the change of cell cycle. Results ⑴ IC50 of MCF-7 and MCF-7/pac was 22.47 μmol/L and 31.38 μmol/L, respectively. ⑵ Immunofluorescence and Western blot results showed that the expression of acetylation of alpha-tubulin in resistant MCF-7 cell/pac was obviously decreased. ⑶ Real time polymerase chain reaction (RT-PCR) and Western blot showed Cep70 expression was consistent of acetylation of alpha-tubulin. ⑷ After incubation with paclitaxel for 24 hours, the expressions of acetylation of alpha-tubulin and Cep70 in MCF-7 and MCF-7/pac were increased, but the extent of MCF-7 cell was much higher. Instead, incubation with nocodazole after 24 hours, the acetylation of alpha-tubulin and Cep70 in MCF-7 and MCF-7/pac cells were obviously lowered. ⑸ After paclitaxel intervention, compared to the same group MCF-7 cells, the G2 phase ratio in MCF-7/pac cells was lower. In addition, given nocodazole after the intervention, compared to the same group MCF-7 cells, the ratio of G2 phase in MCF-7 cell/pac was significantly decreased. Conclusions Cep70 decreased the expression of the acetylated alpha-tubulin, reduced the stability of microtubules, which could be an important mechanism of taxol drug resistance. Key words: Centrosome; Tubulin; Breast neoplasms/DT/ME; Taxoids; Drug resistance, neoplasm

MiR 221/222 as New Players in Tamoxifen Resistance.

Breast cancer is the most frequent cancer in women. Despite advances in early detection and treatment, it has the second highest mortality rate after lung cancer. Around 85% of breast carcinomas are ER+; thus, antiestrogens like tamoxifen are beneficial. Although, tamoxifen is useful for many patients, a number of patients respond poorly to initial therapy or recurrence occurs in about 30% of cases, because tamoxifen resistance happens. Drug resistance remains a major clinical obstacle to successful treatment of breast cancer and more than 90% of unsuccessful treatments are because of acquired resistance and MultiDrug Resistance (MDR) is a major contributor. MicroRNAs are members of a novel class of short noncoding RNAs. Besides their various roles in gene expression, miRNAs are considered as important cancer therapeutic targets and biomarkers. Since 2005, when miRNA deregulation was first reported in breast cancer, more than 1000 reports have been published about miRNAs. Increasing number of studies showed the importance of miRNAs in antiestrogen therapy, especially on tamoxifen; thus, it is not surprising that these tiny molecules are involved in drug resistance. Due to the pivotal role of these known RNA molecules, in this review, we tried to illustrate the importance of the miRNAs as a new player in breast cancer pathogenesis. We have also focused on cancer drug resistance mechanisms highlighting the role of important oncomirs, miR 221/222, involved in cell cycle deregulation in breast cancer. The relationship between these oncomiRs with resistance to tamoxifen is also emphasized.

Abstract 42: A new type of drug resistance in cancer: extracellular ATP-induced resistance through ATP internalization and ATP-drug competition

Abstract Drug resistance is a major problem in cancer therapies and responsible for most relapse, one of the major causes of death in cancer. Several cancer drug resistance mechanisms are known, including genetic mutations in protooncogenes or tumor suppressor genes, cancer stem cells, and multi-drug resistance (MDR). Among these mechanisms, MDR is ATP-dependent. Intratumoral (extracellular) ATP levels of various cancer types are 10⁁3 to 10⁁4 times higher than those in their corresponding normal tissues but the biological significance of the high intratumoral ATP concentrations is unknown. We recently reported that extracellular ATP is internalized by cancer cells via macropinocytosis and enhances their growth and survival (1). Based on these results, we hypothesized that the internalized ATP also promotes drug resistance. Here we report that extracellular ATP, at concentrations in or below the range of reported intratumoral ATP levels, substantially increased intracellular ATP levels and promoted cancer cell drug resistance to tyrosine kinase inhibitor (TKI) sunitinib in human NSCLC A549 cells. The ATP increase and the drug resistance were mediated, at least in part, by macropinocytosis, clathrin- and caveolae-mediated endocytoses. The elevated intracellular ATP induced upregulated phosphorylation of PDGFR and proteins/enzymes in the PDGFR-mediated signaling pathways, such as Akt, mTOR, Raf and MEK, resulting in augmented cell growth and reduced apoptosis induced by sunitinib. The upregulated phosphorylation was not mediated by purinergic receptor signaling. Furthermore, in vitro, ex vivo, and in vivo, extracellular ATP partially restored phosphorylation levels of PDGRF and its downstream proteins/enzymes inhibited by sunitinib, a PDGFR inhibitor (TKI). These results strongly suggest that the extracellular ATP-increased intracellular ATP reversed the inhibition of TKIs by competing with the inhibitors for the ATP-binding site of PDGFR, enhancing the Akt-mTOR and Raf-MEK signaling pathways and promoting cancer cell survival. All these findings significantly expand our understanding of the roles of extracellular ATP in the Warburg effect (2) and drug resistance in cancer and indentify a new anti-drug resistance target. 1. Qian Y, Wang X, et al., Cancer Lett. 351(2014): 242-5. 2. Chen X, Qian Y, Wu S. Free. Radic. Biol. Med. 79(2015): 253-263. Citation Format: Xuan Wang, Yunsheng Li, Yanrong Qian, Yanyang Cao, Xiaozhuo Chen. A new type of drug resistance in cancer: extracellular ATP-induced resistance through ATP internalization and ATP-drug competition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 42.

Computational cell fate modelling for discovery of rewiring in apoptotic network for enhanced cancer drug sensitivity.

The ongoing cancer research has shown that malignant tumour cells have highly disrupted signalling transduction pathways. In cancer cells, signalling pathways are altered to satisfy the demands of continuous proliferation and survival. The changes in signalling pathways supporting uncontrolled cell growth, termed as rewiring, can lead to dysregulation of cell fates e.g. apoptosis. Hence comparative analysis of normal and oncogenic signal transduction pathways may provide insights into mechanisms of cancer drug-resistance and facilitate the discovery of novel and effective anti-cancer therapies. Here we propose a hybrid modelling approach based on ordinary differential equation (ODE) and machine learning to map network rewiring in the apoptotic pathways that may be responsible for the increase of drug sensitivity of tumour cells in triple-negative breast cancer. Our method employs Genetic Algorithm to search for the most likely network topologies by iteratively generating simulated protein phosphorylation data using ODEs and the rewired network and then fitting the simulated data with real data of cancer signalling and cell fate. Most of our predictions are consistent with experimental evidence from literature. Combining the strengths of knowledge-driven and data-driven approaches, our hybrid model can help uncover molecular mechanisms of cancer cell fate at systems level.