Cancer Drug Toxicity Research Articles

Transformer-based Named Entity Recognition for Clinical Cancer Drug Toxicity by Positive-unlabeled Learning and KL Regularizers

Background: With increasing rates of polypharmacy, the vigilant surveillance of clinical drug toxicity has emerged as an important With increasing rates of polypharmacy, the vigilant surveillance of clinical drug toxicity has emerged as an important concern. Named Entity Recognition (NER) stands as an indispensable undertaking, essential for the extraction of valuable insights regarding drug safety from the biomedical literature. In recent years, significant advancements have been achieved in the deep learning models on NER tasks. Nonetheless, the effectiveness of these NER techniques relies on the availability of substantial volumes of annotated data, which is labor-intensive and inefficient. Methods: This study introduces a novel approach that diverges from the conventional reliance on manually annotated data. It employs a transformer-based technique known as Positive-Unlabeled Learning (PULearning), which incorporates adaptive learning and is applied to the clinical cancer drug toxicity corpus. To improve the precision of prediction, we employ relative position embeddings within the transformer encoder. Additionally, we formulate a composite loss function that integrates two Kullback-Leibler (KL) regularizers to align with PULearning assumptions. The outcomes demonstrate that our approach attains the targeted performance for NER tasks, solely relying on unlabeled data and named entity dictionaries. Conclusion: Our model achieves an overall NER performance with an F1 of 0.819. Specifically, it attains F1 of 0.841, 0.801 and 0.815 for DRUG, CANCER, and TOXI entities, respectively. A comprehensive analysis of the results validates the effectiveness of our approach in comparison to existing PULearning methods on biomedical NER tasks. Additionally, a visualization of the associations among three identified entities is provided, offering a valuable reference for querying their interrelationships.

Report from theCardio-Oncology Symposium at theAssociazione Nazionale Medici Cardiologi Ospedalieri (ANMCO) Annual Congress.

Overview of the meeting The Cardio-OncologySymposium at the Associazione Nazionale Medici Cardiologi Ospedalieri (ANMCO) Annual Meeting mainly focused on the diagnosis, management and prevention of cardiovascular toxicity of cancer drugs, in particular, cardiac dysfunction induced by anthracyclines. Although a variety of cardiac biomarkers and imaging modalities are available, there remains no consensus regarding their appropriate useto identify early and late cardiotoxicity and to guide preventive strategies. At the same time, the multitude of pharmacological trials, aimed at preventing cardiac damage through a neurohormonal blockade, provided conflicting results. Nevertheless, the advent of novel heart failure medications can change the decision-makingof the cardio-oncologist. This symposium attempted to harmonize these issues.

Abstract 135: Age-related immunosenescence and cancer drug toxicity and efficacy in C57BL/6J syngeneic model

Abstract Cancer has a higher incidence in the elderly and immunotherapy is widely applied to this population. However, the majority of preclinical studies assessing drug toxicity and efficacy have been done in young healthy mice. Immunosenescence is a state of aging-related gradual deterioration of the immune system in the elderly. Here, we established tumor models in aged mice that show immunosenescence for a better representation of cancer patients, and to examine the effects of aging and immunosenescence on cancer drug efficacy and toxicity. Young (7 weeks), mid-aged (54-58 weeks), and aged (76-78 weeks) C57BL/6J female mice were used for this study. Syngeneic tumor models were established using three different mouse cancer cell lines, B16-F10 melanoma, MC38 colon adenocarcinoma, and E0771 breast cancer. Age-related tumor growth kinetics varied based on tumor models. Specifically, aging did not affect tumor growth kinetics of B16-F10 tumors, while aged mice showed slowed growth of MC38 tumors and faster growth of E0771 tumors. To evaluate the maximum tolerated dose, young and aged mice were dosed with the standard of care cancer drugs (docetaxel, cisplatin, and doxorubicin) and body weight was monitored three times a week. Aged mice showed higher toxicity against standard care cancer drugs compared to young counterparts. Next, we performed efficacy study using checkpoint inhibitor. Young, mid-aged, and aged mice bearing MC-38 tumor were treated with isotype control or Anti-PD1 (8 mg/kg), intravenously, twice weekly for 3 weeks. Whole blood and tumor samples were collected for immune cell profiling. Comparisons of PD-1 response in the various age groups showed that anti-PD1 treatment showed significant suppression of tumor growth in all age groups with the MC38 tumors, with the greatest effect in aged mice. We also found that anti-PD1 treatment increased T cell infiltration into the tumor, and that regulatory T cells in the tumor are decreased in aged mice. In conclusion, we established syngeneic tumor models using aged mice, and found aged mice exhibit higher toxicity against drugs. The effect of aging on tumor growth kinetics varies depending on the models. Differences in immune cell infiltration in the tumor might be an underlying event that causes age-related differences in response to anti-PD1 treatment. The integration of aging in cancer research could potentially bridge the gap between preclinical studies and clinical outcomes. Citation Format: Jiwon Yang, Andrew Schile, Mingshan Cheng, James G. Keck. Age-related immunosenescence and cancer drug toxicity and efficacy in C57BL/6J syngeneic model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 135.

Virtual Screening for the Discovery of Microbiome β-Glucuronidase Inhibitors to Alleviate Cancer Drug Toxicity.

Despite the potency of most first-line anti-cancer drugs, nonadherence to these drug regimens remains high and is attributable to the prevalence of "off-target" drug effects that result in serious adverse events (SAEs) like hair loss, nausea, vomiting, and diarrhea. Some anti-cancer drugs are converted by liver uridine 5'-diphospho-glucuronosyltransferases through homeostatic host metabolism to form drug-glucuronide conjugates. These sugar-conjugated metabolites are generally inactive and can be safely excreted via the biliary system into the gastrointestinal tract. However, β-glucuronidase (βGUS) enzymes expressed by commensal gut bacteria can remove the glucuronic acid moiety, producing the reactivated drug and triggering dose-limiting side effects. Small-molecule βGUS inhibitors may reduce this drug-induced gut toxicity, allowing patients to complete their full course of treatment. Herein, we report the discovery of novel chemical series of βGUS inhibitors by structure-based virtual high-throughput screening (vHTS). We developed homology models for βGUS and applied them to large-scale vHTS against nearly 400,000 compounds within the chemical libraries of the National Center for Advancing Translational Sciences at the National Institutes of Health. From the vHTS results, we cherry-picked 291 compounds via a multifactor prioritization procedure, providing 69 diverse compounds that exhibited positive inhibitory activity in a follow-up βGUS biochemical assay in vitro. Our findings correspond to a hit rate of 24% and could inform the successful downstream development of a therapeutic adjunct that targets the human microbiome to prevent SAEs associated with first-line, standard-of-care anti-cancer drugs.

Epidermal growth factor receptor inhibitor-induced diarrhea: clinical incidence, toxicological mechanism, and management.

The epidermal growth factor receptor (EGFR) family is a class of receptor tyrosine kinase playing a central role in carcinogenesis and cancer progression. The members of this family, particularly EGFR and human epidermal growth factor receptor 2 (HER2), are the most extensively studied drug targets for malignancy. Today, numerous tyrosine kinase inhibitors targeting EGFR family have been developed to combat non-small-cell lung cancer and breast cancer. However, severe gastrointestinal (GI) toxicity leading to dose reduction and treatment discontinuation hampers the therapeutic outcome of EGFR inhibitors. Diarrhea is one of the most frequent GI side effects, especially when it comes to second-generation EGFR inhibitors. Enterocytes apoptosis and increased inflammation accompany with many oral EGFR inhibitors. Loperamide and budesonide are the first-line treatment to manage such adverse effects. However, current prophylaxis and management are all empirical interventions to relieve the symptom. They do not specifically target the toxicological mechanism of EGFR inhibitors. Hereby, those anti-diarrhea agents do not work well when used in cancer patients experiencing EGFR inhibitor-induced diarrhea. On the other hand, the toxicological mechanism of EGFR inhibitor-induced diarrhea is poorly understood. Thus, determining the mechanism behind such diarrhea is urgently in need for developing genuinely effective anti-diarrhea agents. This review aims to call attention to EGFR inhibitor-induced diarrhea, a highly occurring and devastating cancer drug toxicity.

Abstract 2749: Age-related cancer drug toxicity and efficacy, and immune modulation in C57BL6J syngeneic model

Abstract Cancer has a higher incidence in the elderly and immunotherapy is widely applied to this population. However, the majority of preclinical studies assessing drug toxicity and efficacy have been done in young healthy mice, which could lead to translational failure. The goals of this study were to establish tumor models in aged mice for a better representation of cancer patients, and to examine the effects of aging on tumor growth, toxicity and efficacy of cancer treatment, and immune cell populations in syngeneic models using C57BL/6J mice of different ages. Young (7 weeks), mid-aged (56-58 weeks) and aged (76-78 weeks) C57BL/6J female mice were used for this study. To evaluate the maximum tolerated dose, young and aged mice were dosed with the standard of care cancer drugs (docetaxel, cisplatin, and doxorubicin) and body weight was monitored three times a week until mice reached endpoint criteria. Syngeneic tumor models were established using three different mouse cancer cell lines, B16-F10 melanoma, MC38 colon adenocarcinoma, and E0771 breast cancer. Several different concentrations of cells were injected subcutaneously and tumor growth kinetics were evaluated three times weekly. For efficacy study, mice were randomly assigned to isotype control or Anti-PD1 (8 mg/kg) treatment groups, and were dosed intravenously twice weekly for 3 weeks. One week after the last dose, whole blood and tumor samples were collected for flow cytometry analysis for immune cell profiling on B cells, T cells, NK cells. Aged mice showed higher toxicity against docetaxel, cisplatin, and doxorubicin compared to their young counterparts. Age-related tumor growth kinetics varied based on tumor models. Aging did not affect tumor growth kinetics of B16-F10 tumors, while aged mice showed slowed growth of MC38 tumors and faster growth of E0771 tumors. Across all tumor models, aged mice lost body weight while young mice gained body weight over the course of tumor growth, suggesting potential cancer-related cachexia in aged mice. Comparisons of PD-1 response in the various age groups with different tumors showed that anti-PD1 treatment significantly slowed down tumor growth in mid-aged (58 weeks) mice with B16-F10 tumors, but not in young or aged mice. However, the same treatment showed significant suppression of tumor growth in all age groups with the MC38 tumors. This effect might be partly caused by changes in the immune cell infiltration profile with aging. In conclusion, we have established syngeneic tumor models using aged mice and found aged mice exhibit higher toxicity against drugs while the effect of aging on tumor growth kinetics varies depending on models. Differences in immune cell infiltration in the tumor might be an underlying event that causes age-related differences in response to anti-PD1 treatment. The integration of aging in cancer research could potentially bridge the gap between preclinical studies and clinical outcomes. Citation Format: Jiwon Yang, Andrew Schile, Mingshan Cheng, James Keck. Age-related cancer drug toxicity and efficacy, and immune modulation in C57BL6J syngeneic model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2749.

Expression of drug metabolizing enzymes and transporters in the cochlea: Implications for drug delivery and ototoxicity

Inner ear drug delivery is a major area of research and development, but relatively little is known about basic drug metabolism in the cochlea. Additionally, the use of potentially ototoxic drugs such as NSAIDs, chemotherapeutics and aminoglycosides is common, but little is known about the role of metabolism in ototoxicity of those drugs. To address those issues, we compared expression of major Cytochromes P450 (Cyps), UDP-glucuronosyl-transferases (Ugts), sulfotransferases (Sults), and drug transporters between cochleae and liver, an organ with high expression, in mice using qPCR and enzyme kinetics. Together, the tested drug-metabolizing enzymes (DMEs) and transporters account for metabolism of approximately 70–80% of all medically important drugs in the body. Expression of most Cyps was low in the cochlea compared to liver, but three displayed similar expression levels to the liver, and one (Cyp2c65) had significantly higher levels of expression in the cochlea (1.9 ± 0.06 fold vs. liver). Enzyme kinetics revealed undetectable levels of p450 activity in the cochlea, especially as compared to the liver. Similar results were obtained for expression of Ugts and Sults. Interestingly, expression of most transporters was also low, with one major exception: Mdr1/P-glycoprotein (P-gp), which is generally thought to be highly expressed in liver and poorly expressed in most of the nervous system, was 3-fold greater in cochlea. Importantly, P-gp is known to protect other tissues from toxicity of cancer drugs by acting as an efflux pump. Our data demonstrate overall low levels of expression of DMEs and transporters in the cochlea, and identify a few that may be important to consider when designing and testing drugs for local delivery to the inner ear.

Cancer Drug Toxicity: Moving from Patient to Survivor.

Millions of individuals worldwide are living with cancer and have remained disease-free for more than 5 years. These individuals are considered to be cancer survivors. The advent of new targeted therapies and personalized treatment modalities have contributed to this increased survivorship. Additionally, earlier diagnosis and detection of cancer, greater access to preventive screenings, and greater focus on cancer pharmaceutical safety have all been contributed to increasing longevity. Of note, all cancer types have benefited in the survivorship arena. The advent of expansive survivorship care planning mandated by national governmental agencies and the emergence of newer classes of drug therapies for cancer are expected to buttress and support cancer survivorship in the coming decades.

Revival of a potent therapeutic maytansinoid agent using a strategy that combines covalent drug conjugation with sequential nanoparticle assembly

Maytansine and its related analogues are a class of highly potent anti-proliferation agents that have failed to be exploited as clinical drugs for human therapy due to unacceptable systemic toxicity. Here, we delineate a novel strategy that combines rational drug conjugation with subsequent nanoparticle assembly to systemically deliver this highly potent and toxic drug. To demonstrate this concept, we covalently coupled the thiolated maytansine derivative, the DM1 agent, to amphiphilic block co-polymers, polyethylene glycol (PEG)-block-polylactide (PLA), in varying molecular weights to generate two prodrug constructs (i.e., PEG2K-PLA2K-DM1 and PEG2K-PLA4K-DM1) via the maleimide-thiol reaction. The resulting two constructs are amenable to self-assembly in aqueous solutions and are systemically injectable for preclinical studies. In vivo evaluations indicate that PEG-PLA-DM1 conjugate-assembled nanoparticles (NPs) display substantially reduced drug toxicity compared to the free drug forms and NPs that physically encapsulate DM1. Furthermore, following systemic administration, these nanodrugs produced superior therapeutic efficacy over free DM1 in a colon tumor xenograft-bearing mouse model. Therefore, this study provides evidence that the conjugation of toxic drugs to assembling copolymers enables the alleviation of cancer drug toxicity and effective delivery of anticancer drugs. Thus, this DM1-formulated platform represents a new generation of nanotherapeutics that are available for further clinical evaluation.

New Generation Nanomedicines Constructed from Self-Assembling Small-Molecule Prodrugs Alleviate Cancer Drug Toxicity.

The therapeutic index for chemotherapeutic drugs is determined in part by systemic toxicity, so strategies for dose intensification to improve efficacy must also address tolerability. In addressing this issue, we have investigated a novel combinatorial strategy of reconstructing a drug molecule and using sequential drug-induced nanoassembly to fabricate supramolecular nanomedicines (SNM). Using cabazitaxel as a target agent, we established that individual synthetic prodrugs tethered with polyunsaturated fatty acids were capable of recapitulating self-assembly behavior independent of exogenous excipients. The resulting SNM could be further refined by PEGylation with amphiphilic copolymers suitable for preclinical studies. Among these cabazitaxel derivatives, docosahexaenoic acid-derived compound 1 retained high antiproliferative activity. SNM assembled with compound 1 displayed an unexpected enhancement of tolerability in animals along with effective therapeutic efficacy in a mouse xenograft model of human cancer, compared with free drug administered in its clinical formulation. Overall, our studies showed how attaching flexible lipid chains to a hydrophobic and highly toxic anticancer drug can convert it to a systemic self-deliverable nanotherapy, preserving its pharmacologic efficacy while improving its safety profile. Cancer Res; 77(24); 6963-74. ©2017 AACR.

Immune Cell-Mediated Biodegradable Theranostic Nanoparticles for Melanoma Targeting and Drug Delivery.

Although tremendous efforts have been made on targeted drug delivery systems, current therapy outcomes still suffer from low circulating time and limited targeting efficiency. The integration of cell-mediated drug delivery and theranostic nanomedicine can potentially improve cancer management in both therapeutic and diagnostic applications. By taking advantage of innate immune cell's ability to target tumor cells, the authors develop a novel drug delivery system by using macrophages as both nanoparticle (NP) carriers and navigators to achieve cancer-specific drug delivery. Theranostic NPs are fabricated from a unique polymer, biodegradable photoluminescent poly (lactic acid) (BPLP-PLA), which possesses strong fluorescence, biodegradability, and cytocompatibility. In order to minimize the toxicity of cancer drugs to immune cells and other healthy cells, an anti-BRAF V600E mutant melanoma specific drug (PLX4032) is loaded into BPLP-PLA nanoparticles. Muramyl tripeptide is also conjugated onto the nanoparticles to improve the nanoparticle loading efficiency. The resulting nanoparticles are internalized within macrophages, which are tracked via the intrinsic fluorescence of BPLP-PLA. Macrophages carrying nanoparticles deliver drugs to melanoma cells via cell-cell binding. Pharmacological studies also indicate that the PLX4032 loaded nanoparticles effectively kill melanoma cells. The "self-powered" immune cell-mediated drug delivery system demonstrates a potentially significant advancement in targeted theranostic cancer nanotechnologies.

Structure and Inhibition of Microbiome β-Glucuronidases Essential to the Alleviation of Cancer Drug Toxicity

The selective inhibition of bacterial β-glucuronidases was recently shown to alleviate drug-induced gastrointestinal toxicity in mice, including the damage caused by the widely used anticancer drug irinotecan. Here, we report crystal structures of representative β-glucuronidases from the Firmicutes Streptococcus agalactiae and Clostridium perfringens and the Proteobacterium Escherichia coli, and the characterization of a β-glucuronidase from the Bacteroidetes Bacteroides fragilis. While largely similar in structure, these enzymes exhibit marked differences in catalytic properties and propensities for inhibition, indicating that the microbiome maintains functional diversity in orthologous enzymes. Small changes in the structure of designed inhibitors can induce significant conformational changes in the β-glucuronidase active site. Finally, we establish that β-glucuronidase inhibition does not alter the serum pharmacokinetics of irinotecan or its metabolites in mice. Together, the data presented advance our in vitro and in vivo understanding of the microbial β-glucuronidases, a promising new set of targets for controlling drug-induced gastrointestinal toxicity.

Clinical effect of oxaliplatin, calcium tolinate and tegafur in the chemotherapy of rectal cancer patients

Objective To observe the effect and toxicity of oxaliplatin combined with calcium folinate and tegafur in the treatment of rectal cancer patients, in order to provide a safe and effective clinical program for rectal cancer treatment. Methods 117 rectal cancer patients conforming to the selection criteria were randomly divided into treatment group 59 cases and control group 58 cases by using random number method, treatment group were received chemotherapy of Oxaliplatin, calcium folinate and tegafur; control group were received FOLFOX4 program. After implementation of two treatment plans, solid tumor curative effect evaluation standard from WHO was referenced to evaluate the curative effect. And toxicity classification was reached according to the WHO cancer drug toxicity assessment standard. Results Total effective rate of treatment group was 27.1%, total effective rate of control group was 29.3%,the comparative difference of two rates was not statistically significant(χ2=0.069,P>0.05). The main symptoms of adverse reactions of two treatment plans were decreased of leukopenia, hemoglobin and thrombocytopenia of the blood system; nausea, vomiting, weak and abnormal liver function of the digestive system;,and limb numbness or pain of the nervous system.Adverse reactions difference in two groups was not significant(χ2=0.106,0.158, 0.000,0.563,0.001,0.284,0.068,0.000,all P>0.05).After treatment,the median surial time was 15.5 months in treatment group and 16.5 months in control group,the difference of the median surial time in two groups was not statistically significant(P=0.781,P>0.05). Conclusion Combination of Oxaliplatin, calcium fluoride and tegafur is another safe and effective plan after the FOLFOX4 program in the treatment of rectal cancer drug application. Key words: Rectal neoplamsms; Oxaliplatin; Tegafur; Calcium Fluoride; FOLFOX4 program

Structure and Inhibition of Microbiome β-Glucuronidases Essential to the Alleviation of Cancer Drug Toxicity

Structure and Inhibition of Microbiome β-Glucuronidases Essential to the Alleviation of Cancer Drug Toxicity

Old drug new use--amoxapine and its metabolites as potent bacterial β-glucuronidase inhibitors for alleviating cancer drug toxicity.

Irinotecan (CPT-11) induced diarrhea occurs frequently in patients with cancer and limits its usage. Bacteria β-glucuronidase (GUS) enzymes in intestines convert the nontoxic metabolite of CPT-11, SN-38G, to toxic SN-38, and finally lead to damage of intestinal epithelial cells and diarrhea. We previously reported amoxapine as a potent GUS inhibitor in vitro. To further understand the molecular mechanism of amoxapine and its potential for treatment of CPT-11-induced diarrhea, we studied the binding modes of amoxapine and its metabolites by docking and molecular dynamics simulation, and tested the in vivo efficacy on mice in combination with CPT-11. The binding of amoxapine, its metabolites, 7-hydroxyamoxapine and 8-hydroxyamoxapine, and a control drug loxapine with GUS was explored by computational protocols. The in vitro potencies of metabolites were measured by Escherichia coli GUS enzyme and cell-based assay. Low-dosage daily oral administration was designed to use along with CPT-11 to treat tumor-bearing mice. Computational modeling results indicated that amoxapine and its metabolites bound in the active site of GUS and satisfied critical pharmacophore features: aromatic features near bacterial loop residue F365' and hydrogen bond toward E413. Amoxapine and its metabolites were demonstrated as potent in vitro. Administration of low dosages of amoxapine with CPT-11 in mice achieved significant suppression of diarrhea and reduced tumor growth. Amoxapine has great clinical potential to be rapidly translated to human subjects for irinotecan-induced diarrhea.

Manipulation of the Microbiota for Treatment of IBS and IBD—Challenges and Controversies

There is compelling rationale for manipulating the microbiota to treat inflammatory bowel diseases (IBDs). Although studies of animal models of intestinal inflammation produced promising results, trials in humans have been disappointing. In contrast to IBD, the role of the microbiota in the development of irritable bowel syndrome (IBS) only recently has been considered, but early stage results have been encouraging. As pharmaceutical companies develop fewer truly novel agents for treatment of these disorders, consumers seek safer, long-term strategies to deal with chronic symptoms. We assess the rationale for modulating the microbiota for treatment of IBD and IBS, and discuss whether current concepts are simplistic and overstated or simply under-researched. Are claims exaggerated and expectations unrealistic? Difficulties with microbiota terminology and technologies, as well as differences among patients and the heterogeneity of these diseases, pose additional challenges in developing microbiota-based therapies for IBD and IBS.

Toward creation of a cancer drug toxicity knowledge base: automatically extracting cancer drug-side effect relationships from the literature.

A comprehensive and machine-understandable cancer drug-side effect (drug-SE) relationship knowledge base is important for in silico cancer drug target discovery, drug repurposing, and toxicity predication, and for personalized risk-benefit decisions by cancer patients. While US Food and Drug Administration (FDA) drug labels capture well-known cancer drug SE information, much cancer drug SE knowledge remains buried the published biomedical literature. We present a relationship extraction approach to extract cancer drug-SE pairs from the literature. We used 21,354,075 MEDLINE records as the text corpus. We extracted drug-SE co-occurrence pairs using a cancer drug lexicon and a clean SE lexicon that we created. We then developed two filtering approaches to remove drug-disease treatment pairs and subsequently a ranking scheme to further prioritize filtered pairs. Finally, we analyzed relationships among SEs, gene targets, and indications. We extracted 56,602 cancer drug-SE pairs. The filtering algorithms improved the precision of extracted pairs from 0.252 at baseline to 0.426, representing a 69% improvement in precision with no decrease in recall. The ranking algorithm further prioritized filtered pairs and achieved a precision of 0.778 for top-ranked pairs. We showed that cancer drugs that share SEs tend to have overlapping gene targets and overlapping indications. The relationship extraction approach is effective in extracting many cancer drug-SE pairs from the literature. This unique knowledge base, when combined with existing cancer drug SE knowledge, can facilitate drug target discovery, drug repurposing, and toxicity prediction.

A Genetic Screen Using the PiggyBac Transposon in Haploid Cells Identifies Parp1 as a Mediator of Olaparib Toxicity

Genetic perturbation screens have the potential to dissect a wide range of cellular phenotypes. Such screens have historically been difficult in diploid mammalian cells. The recent derivation of haploid embryonic stem cells provides an opportunity to cause loss of function mutants with a random mutagen in a mammalian cell with a normal genetic background. We describe an approach to genetic screens that exploits the highly active piggyBac transposon in haploid mammalian cells. As an example of haploid transposon (HTP) screening, we apply this approach to identifying determinants of cancer drug toxicity and resistance. In a screen for 6-thioguanine resistance we recovered components of the DNA mismatch repair pathway, a known requirement for toxicity. In a further screen for resistance to the clinical poly(ADP-ribose) polymerase (PARP) inhibitor olaparib we recovered multiple Parp1 mutants. Our results show that olaparib toxicity to normal cells is mediated predominantly via Parp1, and suggest that the clinical side effects of olaparib may be on target. The transposon mutant libraries are stable and can be readily reused to screen other drugs. The screening protocol described has several advantages over other methods such as RNA interference: it is rapid and low cost, and mutations can be easily reverted to establish causality.

427 The mitochondrial basis of resistance to BCL-2 antagonists and conventional chemotherapy

Unresponsiveness to therapy remains a significant problem in the treatment of cancer, also with the new classes of cancer drugs. In my laboratory, we use functional genetic approaches to identify biomarkers that can predict responsiveness to targeted cancer therapeutics. Nevertheless, it remains poorly explained why a significant number of tumors do not respond to these therapies. We aim to elucidate the molecular pathways that contribute to unresponsiveness to targeted cancer therapeutics using a functional genetic approach. This will yield biomarkers that may be useful to predict how individual patients will respond to these drugs. Furthermore, this work may allow the development of drugs that act in synergy with the established drug to prevent or overcome drug resistance. To identify biomarkers that control tumor cell responsiveness to cancer therapeutics, we use multiple complementary approaches. First, we use genome wide loss-of-function genetic screens (with shRNA interference libraries) in cancer cells that are sensitive to the drug-of-interest to search for genes whose down-regulation confers resistance to the drugof-interest (resistance screens). In addition, we use shRNA screens to screen for genes whose inhibition enhances the toxicity of cancer drugs (sensitizer screens). As a third approach, we use gain of function genetic screens in which we search for genes whose over-expression modulates drug responsiveness. Once we have identified candidate drug response biomarkers in relevant cell line models, we ask if the expression of these genes is correlated with clinical response to the drug-of-interest. For this, we use tumor samples of cancer patients treated with the drug in question and whose response to therapy is documented. In a fourth and distinct approach we perform high throughput sequencing of the “kinome” (some 600 genes) of tumor samples to identify connections between cancer genotype and drug responses. Examples of some of these approaches to identify biomarkers of response to different cancer drugs will be presented.

Reporting of cancer clinical trial adverse drug events: A RADAR report.

6090 Background: The timely identification of unknown toxicities of cancer drugs is an important, unsolved problem. Because of their cytotoxic effects, distinguishing cancer drug toxicity from disease progression or comorbidity can be difficult. Also, because of the need for novel cancer therapies, regulatory approval is typically based on fewer than 3000 patients. The adverse event detection failure rate during cancer clinical trials has not previously been determined and there has been relatively little evaluation of the utility of applying validated methods for ADE abstraction in this setting. Here, we compare routine adverse event reporting to structured case abstraction (SCA) of the research record and medical record. Outcomes of interest included detection, description, severity grading, and causality attribution. Methods: We obtained all adverse event data (2001-2008) reported to the Northwestern University Institutional Review Board (IRB) for all six clinical trials involving bevacizumab or oxaliplatin. We compared routine IRB reports to SCA for ability to detect an adverse event and for utility of assessing causality attribution with the 10-item Naranjo Scale. Results: Of the 205 adverse events found in the research record and medical record, 182 events (75%) were not reported; six of the 30 (20%) events with a severity grade of “severe,” “life-threatening,” or “fatal” and a causality assessment of “possible”, “probable”, or “definite” were unreported. The mean number of Naranjo items for which there was useful information was higher with SCA than with the standard IRB report (6.0 vs. 2.4 items, p<0.0001). Conclusions: One-fifth of “reportable” adverse events were unreported to the IRB via routine adverse event reporting. SCA also provided more useful information as to whether the adverse event was caused by the cancer drug exposure. Our results suggest that SCA has potential to improve adverse event detection and to improve the accuracy of causality attribution during cancer drug clinical trials. Use of SCA may reduce delays in recognition of novel cancer drug safety signals. There is an urgent need to prospectively evaluate use of structured case abstraction during cancer drug clinical trials.