Resistance In Cancer Patients Research Articles

Cancer TARGETases: DSB repair as a pharmacological target.

Cancer is a disease attributed to the accumulation of DNA damages due to incapacitation of DNA repair pathways resulting in genomic instability and a mutator phenotype. Among the DNA lesions, double stranded breaks (DSBs) are the most toxic forms of DNA damage which may arise as a result of extrinsic DNA damaging agents or intrinsic replication stress in fast proliferating cancer cells. Accurate repair of DSBs is therefore paramount to the cell survival, and several classes of proteins such as kinases, nucleases, helicases or core recombinational proteins have pre-defined jobs in precise execution of DSB repair pathways. On one hand, the proper functioning of these proteins ensures maintenance of genomic stability in normal cells, and on the other hand results in resistance to various drugs employed in cancer therapy and therefore presents a suitable opportunity for therapeutic targeting. Higher relapse and resistance in cancer patients due to non-specific, cytotoxic therapies is an alarming situation and it is becoming more evident to employ personalized treatment based on the genetic landscape of the cancer cells. For the success of personalized treatment, it is of immense importance to identify more suitable targetable proteins in DSB repair pathways and also to explore new synthetic lethal interactions with these pathways. Here we review the various alternative approaches to target the various protein classes termed as cancer TARGETases in DSB repair pathway to obtain more beneficial and selective therapy.

Abstract 3198: The impact of aerobic exercise on oxygenation and vascularity in breast cancer models

Abstract Background: Intratumoral hypoxia (pO2 <10mmHg) is associated with aggressive tumor progression and poor patient outcome. It is often found in solid tumors, and can constitute a major obstacle to anticancer therapy. The primary cause of abnormal oxygen tensions in tumors is the aberrant tumor vasculature, characterized by tortuous, leaky and immature vessels. A number of intervention strategies designed to overcome tumor hypoxia have been investigated including high oxygen content breathing and the use of bioreductive prodrugs, but these have had only moderate success in the clinic. Purpose: The goal of the present investigations was to determine whether aerobic exercise could be applied as a means to improve tumor physiology and decrease tumor hypoxia in breast cancer models. Methods: The effects of single and repeated bouts of moderate intensity exercise (treadmill running) were studied in mice bearing syngeneic murine mammary carcinoma models (EMT6 and 4T1). The exercise intensities were determined by measuring the anaerobic threshold, which is reflected by the steady rise in blood lactate during an exercise bout. Mice were orthotopically injected with tumor cells and once the tumors reached a size of 250 mm3, the mice were exposed to either a single bout of exercise or daily exercise bouts performed for 5 consecutive days. Controls for each treatment consisted of sedentary mice exposed to a stationary treadmill for the equivalent amount of time. Following cessation of each exercise regime tumors were harvested, sectioned and evaluated by immunofluorescence. Vessel density (MECA-32), blood perfusion (Hoechst-33342) and hypoxia (EF5) were quantified and significance was established at p<0.05. Results: Preliminary data indicate that even a single exercise bout may begin to demonstrate improvements in blood vessel perfusion and tumor oxygenation. Importantly, after 5 daily bouts of exercise, there was a significant increase in the number of patent vessels and improvement in oxygenation in the tumors of exercising mice compared to those of sedentary controls. Conclusion: The results indicate that moderate aerobic exercise can improve the oxygenation status of solid tumors. These findings suggest that such a non-toxic intervention may have potential utility in overcoming hypoxia-associated treatment resistance in cancer patients and improve patient outcome. Citation Format: Jennifer M. Wiggins, Jennifer A. Lee, Lori Rice, Dietmar Siemann. The impact of aerobic exercise on oxygenation and vascularity in breast cancer models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3198. doi:10.1158/1538-7445.AM2015-3198

STAT3-Mediated Metabolic Reprograming in Cellular Transformation and Implications for Drug Resistance.

Signal transducer and activator of transcription (STAT)3 mediates the signaling downstream of cytokine and growth factor receptors, regulating the expression of target genes. It is constitutively phosphorylated on tyrosine (Y-P) in many tumors, where its transcriptional activity can induce a metabolic switch toward aerobic glycolysis and down-regulate mitochondrial activity, a prominent metabolic feature of most cancer cells, correlating with reduced production of ROS, delayed senescence, and protection from apoptosis. STAT3 can, however, also localize to mitochondria, where its serine-phosphorylated (S-P) form preserves mitochondrial oxidative phosphorylation and controls the opening of the mitochondrial permeability transition pore, also promoting survival and resistance to apoptosis in response to specific signals/oncogenes such as RAS. Thus, downstream of different signals, both nuclear, Y-P STAT3, and mitochondrial, S-P STAT3, can act by promoting cell survival and reducing ROS production. Here, we discuss these properties in the light of potential connections between STAT3-driven alterations of mitochondrial metabolism and the development of drug resistance in cancer patients.

MiR-148b reverses cisplatin-resistance in non-small cell cancer cells via negatively regulating DNA (cytosine-5)-methyltransferase 1(DNMT1) expression.

BackgroundThe emergence of drug resistance in cancer patients limits the success rate of clinical chemotherapy. MicroRNAs (miRNAs) may play a role in chemoresistance and may be involved in modulating of some drug resistance-related pathways in cancer cells. In this study, the involvement of microRNA-148b (miR-148b) and its roles in the development of chemoresistance in lung cancer are determined.MethodsThis study was performed in two lung cancer cell lines (A549 and SPC-A1). The levels of miR-148b and DNMT1 mRNA expression were determined by using Quantitative Real-Time PCR. Proteins of DNMTs are represented by western blot assay. Cell viability was assessed by MTT assay. Cell apoptosis was evaluated using flow cytometry.ResultsThe data showed a down-regulated of miR-148b expression and evaluated methyltransferases (DNMTs) expression in cisplatin-resisted human non-small cell lung cancer (NSCLC) cell line-A549/DDP and SPC-A1/DDP compared with their parental A549 and SPC-A1 cell line. In transfection experiments, miR-148b mimics reduced the DNMT1 expression, as well as enhanced the sensitivity of cells to cisplatin and cisplatin-induced apoptosis in A549/DDP or SPC-A1/DDP cells. While miR-148b inhibitor increased DNMT1 expression, as well as attenuated the sensitivity of cells to cisplatin in A549 and SPC-A1 cells. miR-148b was showed to exert negative effect on DNMT1 expression by targeting its 3′UTR in A549/DDP and A549 cells. Importantly, silenced DNMT1 increases cisplatin sensitivity of A549/DDP cells and over-expressed DNMT1 reverses pro-apoptosis effect of miR-148b mimic.ConclusionsmiR-148b reverses cisplatin-resistance in non-small cell cancer cells via negatively regulating DNMT1 expression.

Mitochondria as new therapeutic targets for eradicating cancer stem cells: Quantitative proteomics and functional validation via MCT1/2 inhibition.

Here, we used quantitative proteomics analysis to identify novel therapeutic targets in cancer stem cells and/or progenitor cells. For this purpose, mammospheres from two ER-positive breast cancer cell lines (MCF7 and T47D) were grown in suspension using low-attachment plates and directly compared to attached monolayer cells grown in parallel. This allowed us to identify a subset of proteins that were selectively over-expressed in mammospheres, relative to epithelial monolayers. We focused on mitochondrial proteins, as they appeared to be highly upregulated in both MCF7 and T47D mammospheres. Key mitochondrial-related enzymes involved in beta-oxidation and ketone metabolism were significantly upregulated in mammospheres, as well as proteins involved in mitochondrial biogenesis, and specific protein inhibitors of autophagy/mitophagy. Overall, we identified >40 "metabolic targets" that were commonly upregulated in both MCF7 and T47D mammospheres. Most of these "metabolic targets" were also transcriptionally upregulated in human breast cancer cells in vivo, validating their clinical relevance. Based on this analysis, we propose that increased mitochondrial biogenesis and decreased mitochondrial degradation could provide a novel mechanism for the accumulation of mitochondrial mass in cancer stem cells. To functionally validate our observations, we utilized a specific MCT1/2 inhibitor (AR-C155858), which blocks the cellular uptake of two types of mitochondrial fuels, namely ketone bodies and L-lactate. Our results indicate that inhibition of MCT1/2 function effectively reduces mammosphere formation, with an IC-50 of ~1 µM, in both ER-positive and ER-negative breast cancer cell lines. Very similar results were obtained with oligomycin A, an inhibitor of the mitochondrial ATP synthase. Thus, the proliferative clonal expansion of cancer stem cells appears to require oxidative mitochondrial metabolism, related to the re-use of monocarboxylic acids, such as ketones or L-lactate. Our findings have important clinical implications for exploiting mitochondrial metabolism to eradicate cancer stem cells and to prevent recurrence, metastasis and drug resistance in cancer patients. Importantly, a related MCT1/2 inhibitor (AZD3965) is currently in phase I clinical trials in patients with advanced cancers: http://clinicaltrials.gov/show/NCT01791595.

Liquid Biopsy to Monitor the Evolution of Nsclc Egfr+During Treatment with Gefintinib

ABSTRACT Aim: Resistance to EGFR tyrosine kinase inhibitors (TKI) is a clinically relevant problem that needs to be addressed by the use of appropriate technological platforms to discover the early appearance of mutations during treatment and before clinical disease progression. However, there is a lack of standardised approaches to monitor the molecular evolution of the disease under the selective pressure exerted by targeted treatments. One potential, not yet fully validated approach, is the analysis of gene mutations conferring drug resistance on cell-free circulating tumor DNA (cctDNA) released into the peripheral blood from primary tumor and metastatic sites. Periodic monitoring of the genetic evolution of the tumor, unfeasible with repeated biopsies, will greatly contribute to a better understanding and clinical management of drug resistance in cancer patients. Methods: In order to validate this approach in real-life conditions, we examined a case of acquired resistance to EGFR TKI to ascertain whether the technical platform chosen to perform this analysis is appropriate in terms of sensitivity and specificity and if it fulfills our need for molecular monitoring of the disease to improve our ability to personalise treatment. Therefore, in order to understand the cause of resistance to EGFR TKIs, a peripheral blood sample (6 ml) was drawn in a patient at first documented complete response to chemotherapy and at the three following disease progression after gefitinib. cctDNA was extracted from plasma with QIAamp Circulating Nucleic Acid Kit (Qiagen®) and molecular analysis of KRAS G12D, G12V, G12A, G12C, G12R, G12S, BRAF V600E, EGFR T790M was performed with a Digital Droplet PCR (Bio-Rad). Results: At first sampling the patient was wild type for all the tested mutations. At second sampling the patient developed the KRAS G12R and the BRAF V600E mutations. At third sampling also the the EGFR T790M was detected and the analysis confirmed the previous KRAS and BRAF mutations. Finally, the fourth sampling confirmed all three mutations. Conclusions: The liquid biopsy approach is feasible and uncovers the complexity of secondary mutations occurring in NSCLC patients treated with targeted treatments and undescores the role of the KRAS pathway in the development of resistance. Disclosure: All authors have declared no conflicts of interest.

Systems biology of cisplatin resistance: past, present and future.

The platinum derivative cis-diamminedichloroplatinum(II), best known as cisplatin, is currently employed for the clinical management of patients affected by testicular, ovarian, head and neck, colorectal, bladder and lung cancers. For a long time, the antineoplastic effects of cisplatin have been fully ascribed to its ability to generate unrepairable DNA lesions, hence inducing either a permanent proliferative arrest known as cellular senescence or the mitochondrial pathway of apoptosis. Accumulating evidence now suggests that the cytostatic and cytotoxic activity of cisplatin involves both a nuclear and a cytoplasmic component. Despite the unresolved issues regarding its mechanism of action, the administration of cisplatin is generally associated with high rates of clinical responses. However, in the vast majority of cases, malignant cells exposed to cisplatin activate a multipronged adaptive response that renders them less susceptible to the antiproliferative and cytotoxic effects of the drug, and eventually resume proliferation. Thus, a large fraction of cisplatin-treated patients is destined to experience therapeutic failure and tumor recurrence. Throughout the last four decades great efforts have been devoted to the characterization of the molecular mechanisms whereby neoplastic cells progressively lose their sensitivity to cisplatin. The advent of high-content and high-throughput screening technologies has accelerated the discovery of cell-intrinsic and cell-extrinsic pathways that may be targeted to prevent or reverse cisplatin resistance in cancer patients. Still, the multifactorial and redundant nature of this phenomenon poses a significant barrier against the identification of effective chemosensitization strategies. Here, we discuss recent systems biology studies aimed at deconvoluting the complex circuitries that underpin cisplatin resistance, and how their findings might drive the development of rational approaches to tackle this clinically relevant problem.

EP-1823: Proteome-based identification of biomarkers to predict radiation resistance in cancer patients

EP-1823: Proteome-based identification of biomarkers to predict radiation resistance in cancer patients

Binding and inhibition of drug transport proteins by heparin

A major problem in cancer treatment is the development of resistance to chemotherapeutic agents, multidrug resistance (MDR), associated with increased activity of transmembrane drug transporter proteins which impair cytotoxic treatment by rapidly removing the drugs from the targeted cells. Previously, it has been shown that heparin treatment of cancer patients undergoing chemotherapy increases survival. In order to determine whether heparin is capable reducing MDR and increasing the potency of chemotherapeutic drugs, the cytoxicity of a number of agents toward four cancer cell lines (a human enriched breast cancer stem cell line, two human breast cancer cell lines, MCF-7 and MDA-MB-231, and a human lung cancer cell line A549) was tested in the presence or absence of heparin. Results demonstrated that heparin increased the cytotoxicity of a range of chemotherapeutic agents. This effect was associated with the ability of heparin to bind to several of the drug transport proteins of the ABC and non ABC transporter systems. Among the ABC system, heparin treatment caused significant inhibition of the ATPase activity of ABCG2 and ABCC1, and of the efflux function observed as enhanced intracellular accumulation of specific substrates. Doxorubicin cytoxicity, which was enhanced by heparin treatment of MCF-7 cells, was found to be under the control of one of the major non-ABC transporter proteins, lung resistance protein (LRP). LRP was also shown to be a heparin-binding protein. These findings indicate that heparin has a potential role in the clinic as a drug transporter modulator to reduce multidrug resistance in cancer patients.

Activation Of Autophagy By Bone Marrow Adipocytes Protects Myeloma Cells From Chemotherapy-Induced Apoptosis

Currently, chemotherapy is the most effective treatment for multiple myeloma (MM). Although some new drugs have been shown to prolong survival in MM patients, these patients are prone to rapid relapse after high-dose treatment. Recent studies show that several bone marrow (BM) stromal cells are potentially involved in drug resistance. However, the role of other stromal cells is unclear. Adipocytes (ADs) are a major component of BM stromal cells. ADs have been shown to be involved in tumor rapid growth, metastasis, and apoptosis. Clinical studies suggest that BM ADs are associated with an increased risk of MM. Moreover, ADs isolated from patient BM biopsies were shown to support MM proliferation and migration. However, no published study has examined the importance of ADs in MM drug resistance. In addition, autophagy activation has been shown to induce drug resistance in cancer patients. We hypothesized that BM ADs protect MM cells from chemotherapy drug-induced apoptosis by autophagy activation. To examine the role of ADs in MM drug resistance, MM cells were cocultured with ADs at a ratio of 1:5 for 24 hours in medium with melphalan, dexamethasone, or bortezomib, the commonly used drugs for the treatment of MM. MM cells included primary MM cells isolated from BM aspirates of 5 MM patients and 6 MM cell lines. Human ADs were generated from mesenchymal stem cells derived from the BM mononuclear cells of healthy human fetal bones or BM aspirates of MM patients or healthy adult donors, cultured in AD medium for 2 weeks. ADs generated in vitro contained cytoplasmic Oil red O+ lipid droplets and produced triglycerol. Our results showed less drug-induced MM apoptosis in cocultures of MM cells and ADs compared with cultures of MM cells alone. Western blot analysis showed that treatment with melphalan upregulated the levels of cleaved caspase-9 and -3, but not -8, and PARP in MM cells. Compared with cultures alone, cocultures with ADs showed significantly lower levels of cleaved caspase-9, -3, and PARP in melphalan-treated MM cells. Mechanistic studies further showed that cocultures of ADs, compared with cultures alone, significantly upregulated the expression of autophagy proteins LC3B, Atg3, Atg5, and LAMP-1, but not Beclin-1. The addition of autophagy inhibitors 3-methyl adenine and chloroquine diphosphate to the cocultures remarkably enhanced apoptosis and caspase activation. Furthermore, we observed that cocultures of MM cells and ADs with either cell-cell contact or those separated by transwell inserts conferred similar protection from drug-induced apoptosis. We identified that AD-produced adipokines such as adiponection, leptin, adipsin, IL-6, MCP-1, TNF-a, and IGF-1, but not VEGF and CRP, were abundant in all examined ADs. Among these adipokines, adiponection, leptin, and adipsin were mainly produced from ADs and not from BM stromal cells, whereas other adipokines were produced from both cells. The addition of antibodies against these adipokines to the cocultures enhanced apoptosis and reduced autophagy, whereas addition of these adipokines to the cultures alone inhibited apoptosis and enhanced autophagy. In vivo studies validated these findings that injection of BM-derived ADs into the implanted human bones of SCID-hu mice bearing primary MM cells reduced response to treatment with melphalan and induced autophagy activation. Taken together, our findings elucidate a novel mechanism of MM drug resistance, through BM ADs. Our studies also provide evidence that targeting BM ADs may be a new approach to improve the efficacy of chemotherapy for the treatment of MM. Disclosures:No relevant conflicts of interest to declare.

Anti-β2 Microglobulin Monoclonal Antibodies Overcome Bortezomib-Induced Drug Resistance In Multiple Myeloma By Inhibition Of Autophagy

Chemotherapy is the most effective treatment for multiple myeloma (MM). Several new drugs have been developed to prolong MM patient survival. However, application of these drugs, such as bortezomib (BTZ), usually induces drug resistance, and patients are prone to quick relapse. It is known that cell death or proliferation is regulated by the crosstalk between apoptosis and autophagy, and autophagy activation inhibits apoptosis by reducing caspase cleavage. Recent studies have shown that autophagy activation plays a role in chemotherapy drug resistance in cancer patients, in particular, BTZ treatment activates autophagy in MM, indicating that inhibition of autophagy could overcome BTZ-induced drug resistance. We have recently reported the generation of monoclonal antibodies (mAbs) against human beta2 microglobuline (b2M), and have found that high dose mAbs have strong apoptotic effects on MM. In this study, using a BTZ treatment-setting, we hypothesized that anti-β2M mAbs could overcome drug resistance and enhance chemotherapy efficacy in MM by inhibiting autophagy. To investigate the combined effects of mAbs and BTZ, MM cells were cultured with addition of BTZ (5 nM) or mAbs (clone D1; 10 mg/ml) or both for 24 hours. Results from Annexin-V binding assay indicated that combined treatment significantly enhanced apoptosis in MM cell lines, such as ARK, ARP-1, MM.1S, and U266, and in primary MM cells as compared with individual treatment, respectively. Next, BTZ-sensitive or -resistant MM cells KAS-6 WT/V10R or OPM-2 WT/V10R were used to determine the importance of BTZ in the synergistic effects, and such synergistic effects was only shown in apoptosis of BTZ-sensitive cells, but not in BTZ-resistant cells. Furthermore, combined treatment significantly increased apoptosis in β2M-overexpressing, but decreased in β2M-knocking down MM cells, which indicated that the synergistic effects is dependent on the surface β2M expression on MM cells. Mechanistic studies further showed that BTZ treatment resulted in an accumulation of cleaved-caspase 9/3 and PARP cleavage, suggesting that combined treatment enhanced caspase activation. In addition, Western blot analysis showed that BTZ treatment upregulated the expression of autophagy proteins, such as LAMP-1, Beclin 1, and LC3B, in a dose dependent manner, whereas combined treatment decreased their expression. Beclin 1, which is a key protein required for autophagy, has been reported to have a potential NF-kB p65 binding site on its promoter. Therefore, we checked if mAbs inhibited BTZ-induced autophagy via NF-kB signaling pathway. Our data showed that BTZ treatment increased p65 nuclear translocation and the levels of phosphorylated p65 in MM cells, while combined treatment significantly reduced both. ChIP assay has further verified that mAb treatment inhibited p65 binding to Beclin 1 promoter. To examine our hypothesis in vivo, MM cells ARP-1 or MM.1S were subcutaneously injected into SCID mice. The mice were then subcutaneously injected with mAbs (0.6 mg/kg) or intraperitoneally injected with BTZ (0.1 mg/kg) individually or in combination. Tumor burdens were assessed by measuring tumor volumes and serum M-protein levels by ELISA. The combination of anti-β2M mAb and BTZ treatment repressed tumor growth and prolonged the survival of tumor-bearing mice as compared with individual treatment. In conclusion, our study for the first time demonstrated that anti-β2M mAbs prevent BTZ resistance and enhance its anti-MM efficacy by reducing the expression of autophagy proteins via NF-kB signaling. Thus, our studies provide a new insight into clinical development of anti-β2M mAbs to overcome chemotherapy drug resistance and improve MM patient survival. Disclosures:No relevant conflicts of interest to declare.

Platinum-Based Agents for Individualized Cancer Treatment

Platinum-based agents are important drugs or drug candidates for cancer chemotherapy. Traditional platinum drugs including the globally approved cisplatin, carboplatin and oxaliplatin are neutral platinum (II) complexes with two amine ligands and two additional ligands that can be aquated for further binding with DNA. The platinum-DNA adducts can impede cellular process and lead to cellular apoptosis. Tumor resistance to platinum drugs has become a very challenging problem to overcome. Individualized cancer treatment using different strategies to circumvent the platinum-drug resistance in cancer patients is of great importance. Structural modification of traditional platinum drugs, combination therapy using platinum drugs with other agents and improved delivery of platinum drug to tumor sites are major strategies developed to overcome existed problems in chemotherapy using traditional platinum drugs. Platinum-based agents with respect to their structure, mechanism of action and strategies developed for improved efficacy in cancer treatment have been summarized in this paper with the perspective of developing new platinum drugs or platinum-based therapy for individualized cancer treatment.

Real-time liquid biopsy: circulating tumor cells versus circulating tumor DNA.

Liquid biopsy is a new diagnostic concept, i.e., analysis of therapeutic targets and drug resistance-conferring gene mutations on circulating tumor cells and cell-free circulating tumor DNA released into the peripheral blood from metastatic deposits. Here, we discuss current challenges and future perspectives of the liquid biopsy concept in clinical oncology. We postulate that this concept will contribute to a better understanding and clinical management of drug resistance in cancer patients.

Abstract 4640: Highly sensitive proximity mediated immunoassay can determine functional VEGFR2 status in clinical samples for routine clinical uses.

Abstract VEGFR2 is the primary signaling receptor for VEGF-A, and is considered to be the major initiator of angiogenesis. Binding of the growth factor activates VEGFR2 via tyrosine phosphorylation and results in induction of angiogenic and lymphangiogenic signals. An understanding of the VEGFR2 status of human tumors may help to identify patients who would benefit most from treatment with VEGFR2 inhibitors. Currently there are several drugs targeting VEGFR2 either approved for clinical use or in various stages of clinical trials. Bevacizumab, a monoclonal antibody to VEGF-A is used to treat patients with lung, colon and breast cancer. Sunitinib targeting VEGFR2, PDGFRβ and c-Kit was approved for treating carcinoid tumors in the gastro-intestinal stroma. VEGFR2 profiling could be used to monitor the efficacy of anti-angiogenic treatment in cancer patients. Here we report the development of immunoarray assays for functional characterization of VEGFR2 and their application in profiling VEGFR2 status in preclinical and clinical specimens. The CEERTM (Collaborative Enzyme Enhanced Reactive-immunoassay) assays use an antibody-microarray based platform which utilizes the formation of a unique “triple-antibody-enzyme-channeling” immuno-complex capable of measuring expression (total) and activation (phospho) of VEGFR2 in tumor tissues or surrogate tissues with limited availability. CEERTM platform can detect levels of expression and activation of VEGFR2 in as little as 10 cells due to its unique proximity channeling assay configuration. Specimens are analyzed along with standards so quantitative read out can be compared longitudinally. Assay specificity was established by comparing levels of phosphorylated VEGFR2, between the non-treated and treated with VEGF. Phosphorylation levels were increased in VEGFR2 positive cell lines HUVEC and H441 when treated, while VEGFR2 negative cell lines MDA-MB-134 IV, BT474, SNU16, Ramos lymphoma, and K562 did not. In clinical setting, robust quantifiable signals were detected in FNAs or core biopsy tissues obtained from various cancer patients. Ongoing analysis of clinical samples from colorectal, lung and renal cancer patients indicates an increase of VEGFR2 phosphorylation in tumor samples compared to healthy tissues and a reduction of VEGFR2 phosphorylation post VEGFR2-targeted therapy in some patients. 47% (18/38) of NSCLC patients have shown evidence of activated VEGFR2, and it would be interesting to determine if patients with activated VEGFR2 respond to Bevacizumab. The CEER-based VEGFR2 assay can provide quantitative analysis of clinical samples with limited availability providing critical information for developing effective strategies for treatment selection, monitoring drug response and overcoming potential resistance in cancer patients. Citation Format: Kelly D. Hester, Nicholas Hoe, Jinyao Zhou, Crystal Kuy, Liching Zhang, Phillip Kim, Xinjun Liu, Sharat Singh. Highly sensitive proximity mediated immunoassay can determine functional VEGFR2 status in clinical samples for routine clinical uses. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4640. doi:10.1158/1538-7445.AM2013-4640

A novel serum protein signature associated with resistance to epidermal growth factor receptor tyrosine kinase inhibitors in head and neck squamous cell carcinoma

BackgroundAcquired resistance to tyrosine kinase inhibitors (TKIs) is becoming a major challenge in the treatment of many cancers. Epidermal growth factor receptor (EGFR) is overexpressed in squamous carcinomas, notably those of the head and neck (HNSCC), and can be targeted with several TKIs. We aimed to identify soluble proteins suitable for development as markers of EGFR TKI resistance in cancer patients to aid in early and minimally invasive assessment of therapeutic responses. MethodsResistant HNSCC cell lines were generated by exposure to an EGFR TKI, gefitinib, in vitro. Cell lines were characterised for their biological behaviour in vitro (using growth inhibition assays, flow cytometry, western blots, antibody arrays and/or immunoassays) and in vivo (using subcutaneous tumour xenografts). Sera from EGFR-treated and -untreated HNSCC patients were analysed by immunoassay. ResultsTwo independent sublines of CAL 27 and a PJ34 subline with acquired resistance to EGFR TKIs (gefitinib, erlotinib and afatinib) were developed. Resistant cells grew as highly aggressive xenografts leading to reduced host survival rates compared with EGFR-TKI sensitive cells. This suggested a link between resistance in vitro and poor prognosis in vivo. A significant upregulation of proteins linked to tumour angiogenesis and invasion was identified in resistant cells. This ‘resistance-associated protein signature’ (RAPS) was detected in the sera of a small cohort of HNSCC patients and was associated with reduced survival. ConclusionWe have identified a protein signature associated with EGFR-TKI resistance that may also be linked to poor prognosis and warrants further investigation as a potential clinical biomarker.

Rationally Designed Multitarget Anticancer Agents

Balanced modulation of multiple targets is an attractive therapeutic strategy in treating complex diseases including cancer. Comparing with drugs combination, single molecule modulating desirable multiple targets has advantages in pharmacokinetic and pharmacodynamics. Different from previous reviews, we provided an overview of reported multitarget antitumor agents from the viewpoint of pharmacophores. These multitarget antitumor agents were designed by combination of pharmacophores or by high-throughput screening plus structural modification, which were exemplified by the privileged pharmacophore quinazoline and several other popular pharmacophores, including phenylaminopyrimidine, anthracycline and naphthalimide. Previous research demonstrated the importance of in-depth validation against multiple targets not only in cell-free system, but also in cancer cells. Furthermore, the multitarget compounds were also effective for resistance cell lines which highlighted their antitumor potency in the era of increasing drug resistance in cancer patients.

Chimerically designed HDAC- and tyrosine kinase inhibitors. A series of erlotinib hybrids as dual-selective inhibitors of EGFR, HER2 and histone deacetylases

The regulation of chromatin structure and, therefore, transcriptional activity of histone proteins by reversible lysine acetylation is an important posttranslational modification. Inhibitors of histone deacetylase (HDAC) are considered as promising new anti-neoplastic drugs. The hydroxamic acid SAHA e.g. is currently used in the treatment of advanced primary cutaneous T-cell lymphoma. The EGFR protein tyrosine kinase inhibitor erlotinib is a prominent drug in cancer chemotherapy and currently approved for treatment of non-small cell lung cancer. In this report, we present a novel strategy for cancer drug development by a combination of EGFR/HER2 kinase and HDAC inhibitory activity in one molecule. By combining two distinct pharmacological properties in one molecule, we expect a broader activity spectrum and less likelihood of drug resistance in cancer patients. The combination led to substances with both HDAC inhibitory properties and EGFR as well as HER2 kinase inhibitory activities.

Abstract C29: Elevated CDKN1A (p21) expression in human cancer cell variants selected for resistance to the novel microtubule depolymerizing agent BAL27862 (active moiety of BAL101553).

Abstract BAL27862 is a synthetic small molecule that induces tumor cell apoptosis due to inhibition of tubulin polymerization via a potentially new mechanism of action. Administered as the prodrug BAL101553, BAL27862 is currently undergoing Phase I evaluation in advanced cancer patients. We have previously demonstrated that BAL27862 retains activity in a broad panel of MDR1(+) and MDR1(−) human breast and ovarian cancer cell variants selected for resistance to taxanes (Abstract 4412, AACR 2010). In this current study, we established five variants selected for stable drug resistance in cell lines from human lung cancer (H460 and A549), acute T-cell leukemia (Jurkat), ovarian cancer (SK-OV-3) and cervical cancer (HeLa). These variants are approximately 3- to 24-fold resistant to BAL27862. The resistance is not transporter mediated, with no activation of ABCB1 (MDR1/P-glycoprotein) following drug selection, no change in activity in cells co-incubated with known P-glycoprotein inhibitors (PSC-833, 2 μM) and no difference in either accumulation or retention of [14C]-BAL27862 relative to parental controls. Tubulin polymerization assays indicated a higher proportion of tubulin in the polymerized fraction from resistant lines, indicating microtubule stabilization. Consistently, most lines exhibited increased sensitivity to microtubule stabilizers (e.g. resistance factors [RF = antiproliferative IC50 resistant line/parental line] for paclitaxel: H460=0.4; Jurkat=0.7). Strikingly, differential responses to standard microtubule-destabilizing agents were evident. For example, RFs for Jurkat cells were lower for both vincristine (2.5) and colchicine (10) as compared to BAL27862 (24); whereas, similar RFs were measured in SK-OV-3 (3, 5 and 4, respectively). Finally, relative to parental controls, altered tubulin isoform content was observed in some BAL27862-selected lines, but elevated CDKN1A (p21) protein expression was observed in 4 out of 5 of the resistant variants (SK-OV-3, H460, A549 and HeLa). Q-PCR analysis indicated an associated elevation in p21 mRNA levels only in lines with enhanced protein expression. As aberrant p21 expression has been previously related to poor prognosis and chemotherapy resistance in cancer patients, the potential of using this biomarker to support patient stratification efforts in future trials is worthy of further study. The functional significance of p21 to the resistance phenotype, and other key alterations identified through more detailed genomic profiling (Stanford's HEEBO microarrays), will be studied by gene transfer and gene silencing experiments. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C29.

Abstract 4265: Bithionol as an inhibitor of tumor angiogenesis

Abstract Tumor progression depends on angiogenesis. The clinical successes in recent years have demonstrated that antiangiogenic agents can be developed as effective treatment for cancer patients. However, the resistance to the current FDA approved antiangiogenic therapies is emerging, which presents challenges in cancer research and urgent needs for novel angiogenesis inhibitors with different mechanisms of drug actions to overcome the resistance. In our previous studies, we have identified a small molecule bithionol as a potential antiangiogenic agent through a chemical diversity library screening with a cell-based angiogenesis assay. Bithionol is a FDA approved and current clinically used anthelmintics, which has been found to directly inhibit activity of autotaxin, a secreted enzyme that catalyzes lysophosphatidic acid (LPA) production. LPA, as a lipid signaling molecule, is a potent angiogenic and cancer cell motility stimulating factor. Therefore, autotaxin plays important role in tumor angiogenesis and metastasis and has been recently identified as an attractive angiogenesis and cancer target. Our recent studies have shown that autotaxin is expressed at high levels in human endothelial and number of human cancer cell lines. Bithionol has demonstrated inhibitory activities against human endothelial cell proliferation, migration, and tube-formation as the three key cellular steps in angiogenesis process. The effect of bithionol on inhibition of tumor angiogenesis was also evaluated with an ex vivo xenograft chicken embryo chorioallantoic membrane (xenograft-CAM) model system. Bithionol is able to inhibit tumor-induced new blood vessel formation in a dose dependent manner and has demonstrated an additive inhibitory activity when it is applied in combination with Sutent, a current clinically used antiangiogenic drug. The results of this research suggest that bithionol provide a unique promising opportunity in developing new combinational treatment to increase the anticancer efficacy and minimize the resistance in cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4265. doi:10.1158/1538-7445.AM2011-4265

Molecular Evolutionary Analysis of ABCB5: The Ancestral Gene Is a Full Transporter with Potentially Deleterious Single Nucleotide Polymorphisms

BackgroundABCB5 is a member of the ABC protein superfamily, which includes the transporters ABCB1, ABCC1 and ABCG2 responsible for causing drug resistance in cancer patients and also several other transporters that have been linked to human disease. The ABCB5 full transporter (ABCB5.ts) is expressed in human testis and its functional significance is presently unknown. Another variant of this transporter, ABCB5 beta posses a “half-transporter-like” structure and is expressed in melanoma stem cells, normal melanocytes, and other types of pigment cells. ABCB5 beta has important clinical implications, as it may be involved with multidrug resistance in melanoma stem cells, allowing these stem cells to survive chemotherapeutic regimes.Methodology/Principal FindingsWe constructed and examined in detail topological structures of the human ABCB5 protein and determined in-silico the cSNPs (coding single nucleotide polymorphisms) that may affect its function. Evolutionary analysis of ABCB5 indicated that ABCB5, ABCB1, ABCB4, and ABCB11 share a common ancestor, which began duplicating early in the evolutionary history of chordates. This suggests that ABCB5 has evolved as a full transporter throughout its evolutionary history.Conclusions/SignificanceFrom our in-silco analysis of cSNPs we found that a large number of non-synonymous cSNPs map to important functional regions of the protein suggesting that these SNPs if present in human populations may play a role in diseases associated with ABCB5. From phylogenetic analyses, we have shown that ABCB5 evolved as a full transporter throughout its evolutionary history with an absence of any major shifts in selection between the various lineages suggesting that the function of ABCB5 has been maintained during mammalian evolution. This finding would suggest that ABCB5 beta may have evolved to play a specific role in human pigment cells and/or melanoma cells where it is predominantly expressed.