Pharmacogenetic Discovery in CALGB (Alliance) 90401 and Mechanistic Validation of a VAC14 Polymorphism that Increases Risk of Docetaxel-Induced Neuropathy

Contribution of plasma levels of VEGF-A and angiopoietin-2 in addition to a genetic variant in KCNAB1 to predict the risk of bevacizumab-induced hypertension

Bevacizumab-induced hypertension poses a therapeutic challenge and identifying biomarkers for hypertension can enhance therapy safety. Lower plasma levels of VEGF-A, angiopoietin-2, and rs6770663 in KCNAB1 were previously associated with increased risk of bevacizumab-induced hypertension. This study investigated whether these factors independently contribute to grade 2-3 bevacizumab-induced hypertension risk in 277 cancer patients (CALGB/Alliance 90401). Multivariable analyses assessed the independent association of each factor and hypertension. Likelihood ratio test (LRT) evaluated the explanatory significance of combining protein levels and rs6770663 in predicting hypertension. Boostrap was employed to assess the mediation effect of protein levels on the rs6770663 association with hypertension. Lower protein levels and rs6770663 were independently associated with increased hypertension risk. Adding rs6770663 to protein levels improved the prediction of hypertension (LRT p = 0.0002), with no mediation effect observed. Protein levels of VEGF-A, angiopoietin-2 and rs6770663 in KCNAB1 are independent risk factors and, when combined, may improve prediction of bevacizumab-induced hypertension. ClinicalTrials.gov Identifier: NCT00110214.

Common variation in a long non-coding RNA gene modulates variation of circulating TGF-β2 levels in metastatic colorectal cancer patients (Alliance)

BACKGROUND

Herein, we report results from a genome-wide study conducted to identify protein quantitative trait loci (pQTL) for circulating angiogenic and inflammatory protein markers in patients with metastatic colorectal cancer (mCRC). The study was conducted using genotype, protein marker, and baseline clinical and demographic data from CALGB/SWOG 80405 (Alliance), a randomized phase III study designed to assess outcomes of adding VEGF or EGFR inhibitors to systemic chemotherapy in mCRC patients. Germline DNA derived from blood was genotyped on whole-genome array platforms. The abundance of protein markers was quantified using a multiplex enzyme-linked immunosorbent assay from plasma derived from peripheral venous blood collected at baseline. A robust rank-based method was used to assess the statistical significance of each variant and protein pair against a strict genome-wide level. A given pQTL was tested for validation in two external datasets of prostate (CALGB 90401) and pancreatic cancer (CALGB 80303) patients. Bioinformatics analyses were conducted to further establish biological bases for these findings.

RESULTS

The final analysis was carried out based on data from 540,021 common typed genetic variants and 23 protein markers from 869 genetically estimated European patients with mCRC. Correcting for multiple testing, the analysis discovered a novel cis-pQTL in LINC02869, a long non-coding RNA gene, for circulating TGF-β2 levels (rs11118119; AAF = 0.11; P-value < 1.4e-14). This finding was validated in a cohort of 538 prostate cancer patients from CALGB 90401 (AAF = 0.10, P-value < 3.3e-25). The analysis also validated a cis-pQTL we had previously reported for VEGF-A in advanced pancreatic cancer, and additionally identified trans-pQTLs for VEGF-R3, and cis-pQTLs for CD73.

CONCLUSIONS

This study has provided evidence of a novel cis germline genetic variant that regulates circulating TGF-β2 levels in plasma of patients with advanced mCRC and prostate cancer. Moreover, the validation of previously identified pQTLs for VEGF-A, CD73, and VEGF-R3, potentiates the validity of these associations.

Pharmacogenetic and clinical risk factors for bevacizumab-related gastrointestinal hemorrhage in prostate cancer patients treated on CALGB 90401 (Alliance)

The objective of this study was to discover clinical and pharmacogenetic factors associated with bevacizumab-related gastrointestinal hemorrhage in Cancer and Leukemia Group B (Alliance) 90401. Patients with metastatic castration-resistant prostate cancer received docetaxel and prednisone ± bevacizumab. Patients were genotyped using Illumina HumanHap610-Quad and assessed using cause-specific risk for association between single nucleotide polymorphisms (SNPs) and gastrointestinal hemorrhage. In 1008 patients, grade 2 or higher gastrointestinal hemorrhage occurred in 9.5% and 3.8% of bevacizumab (n = 503) and placebo (n = 505) treated patients, respectively. Bevacizumab (P < 0.001) and age (P = 0.002) were associated with gastrointestinal hemorrhage. In 616 genetically estimated Europeans (n = 314 bevacizumab and n = 302 placebo treated patients), grade 2 or higher gastrointestinal hemorrhage occurred in 9.6% and 2.0% of patients, respectively. One SNP (rs1478947; HR 6.26; 95% CI 3.19-12.28; P = 9.40 × 10-8) surpassed Bonferroni-corrected significance. Grade 2 or higher gastrointestinal hemorrhage rate was 33.3% and 6.2% in bevacizumab-treated patients with the AA/AG and GG genotypes, versus 2.9% and 1.9% in the placebo arm, respectively. Prospective validation of these findings and functional analyses are needed to better understand the genetic contribution to treatment-related gastrointestinal hemorrhage.

Common variation in a long non-coding RNA gene modulates variation of circulating TGF-β2 levels in metastatic colorectal cancer patients (Alliance)

Background

Herein, we report results from a genome-wide study conducted to identify protein quantitative trait loci (pQTL) for circulating angiogenic and inflammatory protein markers in patients with metastatic colorectal cancer (mCRC).The study was conducted using genotype, protein marker, and baseline clinical and demographic data from CALGB/SWOG 80405 (Alliance), a randomized phase III study designed to assess outcomes of adding VEGF or EGFR inhibitors to systemic chemotherapy in mCRC patients. Germline DNA derived from blood was genotyped on whole-genome array platforms. The abundance of protein markers was quantified using a multiplex enzyme-linked immunosorbent assay from plasma derived from peripheral venous blood collected at baseline. A robust rank-based method was used to assess the statistical significance of each variant and protein pair against a strict genome-wide level. A given pQTL was tested for validation in two external datasets of prostate (CALGB 90401) and pancreatic cancer (CALGB 80303) patients. Bioinformatics analyses were conducted to further establish biological bases for these findings.

Results

The final analysis was carried out based on data from 540,021 common typed genetic variants and 23 protein markers from 869 genetically estimated European patients with mCRC. Correcting for multiple testing, the analysis discovered a novel cis-pQTL in LINC02869, a long non-coding RNA gene, for circulating TGF-β2 levels (rs11118119; AAF = 0.11; P-value < 1.4e-14). This finding was validated in a cohort of 538 prostate cancer patients from CALGB 90401 (AAF = 0.10, P-value < 3.3e-25). The analysis also validated a cis-pQTL we had previously reported for VEGF-A in advanced pancreatic cancer, and additionally identified trans-pQTLs for VEGF-R3, and cis-pQTLs for CD73.

Conclusions

This study has provided evidence of a novel cis germline genetic variant that regulates circulating TGF-β2 levels in plasma of patients with advanced mCRC and prostate cancer. Moreover, the validation of previously identified pQTLs for VEGF-A, CD73, and VEGF-R3, potentiates the validity of these associations.

Evolution of predictive risk factor analysis for chemotherapy-related toxicity

The causes of variation in toxicity to the same treatment regimen among seemingly similar patients remain largely unknown. There was tremendous optimism that the patient's germline genome would be strongly predictive of treatment-related toxicity and could be used to personalize treatment and improve therapeutic outcomes. However, there has been limited success in discovering robust pharmacogenetic predictors of treatment-related toxicity and even less progress in translating the few validated predictors into clinical practice. It is apparent that identification of toxicity predictors that can be used to predict and prevent treatment-related toxicity will require thinking beyond germline genomics. To that end, we propose an integrated biomarker discovery approach that recognizes that a patient's toxicity risk is determined by the cumulative effects of a broad range of "omic" and non-omic factors. This commentary describes the limited success in discovering and translating clinical and pharmacogenetic toxicity predictors into clinical practice. We illustrate the evolution of cancer toxicity biomarker discovery and translation through studies of taxane-induced peripheral neuropathy, which is one of the most common and debilitating side effects of cancer treatment. We then discuss the opportunities for discovering non-genomic (e.g., metabolomic, lipidomic, transcriptomic, proteomic, microbiomic, medical, behavioral, environmental) and integrated biomarkers that may be more strongly predictive of toxicity risk and the potential challenges with translating integrated biomarkers into clinical practice. This integrated biomarker discovery approach may circumvent some of the major limitations in toxicity biomarker science and move precision oncology treatment forward so that patients receive maximum treatment benefit with minimal toxicity.

A systematic review of genome-wide association studies for pain, nociception, neuropathy, and pain treatment responses

ABSTRACT

Pain is the leading cause of disability worldwide, imposing an enormous burden on personal health and society. Pain is a multifactorial and multidimensional problem. Currently, there is (some) evidence that genetic factors could partially explain individual susceptibility to pain and interpersonal differences in pain treatment response. To better understand the underlying genetic mechanisms of pain, we systematically reviewed and summarized genome-wide association studies (GWASes) investigating the associations between genetic variants and pain/pain-related phenotypes in humans. We reviewed 57 full-text articles and identified 30 loci reported in more than 1 study. To check whether genes described in this review are associated with (other) pain phenotypes, we searched 2 pain genetic databases, Human Pain Genetics Database and Mouse Pain Genetics Database. Six GWAS-identified genes/loci were also reported in those databases, mainly involved in neurological functions and inflammation. These findings demonstrate an important contribution of genetic factors to the risk of pain and pain-related phenotypes. However, replication studies with consistent phenotype definitions and sufficient statistical power are required to validate these pain-associated genes further. Our review also highlights the need for bioinformatic tools to elucidate the function of identified genes/loci. We believe that a better understanding of the genetic background of pain will shed light on the underlying biological mechanisms of pain and benefit patients by improving the clinical management of pain.

Pharmacogenetics of Breast Cancer Treatments: A Sub-Saharan Africa Perspective

Breast cancer is the most frequent cause of cancer death in low- and middle-income countries, in particular among sub-Saharan African women, where response to available anticancer treatment therapy is often limited by the recurrent breast tumours and metastasis, ultimately resulting in decreased overall survival rate. This can also be attributed to African genomes that contain more variation than those from other parts of the world. The purpose of this review is to summarize published evidence on pharmacogenetic and pharmacokinetic aspects related to specific available treatments and the known genetic variabilities associated with metabolism and/or transport of breast cancer drugs, and treatment outcomes when possible. The emphasis is on the African genetic variation and focuses on the genes with the highest strength of evidence, with a close look on CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4/5, CYP19A1, UGT1A4, UGT2B7, UGT2B15, SLC22A16, SLC38A7, FcγR, DPYD, ABCB1, and SULT1A1, which are the genes known to play major roles in the metabolism and/or elimination of the respective anti-breast cancer drugs given to the patients. The genetic variability of their metabolism could be associated with different metabolic phenotypes that may cause reduced patients' adherence because of toxicity or sub-therapeutic doses. Finally, this knowledge enhances possible personalized treatment approaches, with the possibility of improving survival outcomes in patients with breast cancer.

Polygenic Risk Scores for Blood Pressure to Assess the Risk of Severe Bevacizumab-Induced Hypertension in Cancer Patients (Alliance)

Hypertension is a common bevacizumab-induced toxicity. No markers are available to predict patients at risk of developing hypertension. We hypothesized that genetic risk of essential hypertension, as measured by a blood pressure polygenic risk score (PRS), would be associated with risk of severe bevacizumab-induced hypertension. PRSs were calculated for 1,027 bevacizumab-treated patients of European descent with cancer from four clinical trials (Alliance for Clinical Trials in Oncology (Alliance) / Cancer and Leukemia Group B (CALGB) 80303, 40503, 90401, 40502) using summary systolic blood pressure (SBP) and diastolic blood pressure (DBP) genome-wide association results obtained from 757,601 individuals of European descent. The association between PRS and grade 3 bevacizumab-induced hypertension (Common Toxicity Criteria for Adverse Events version 3) in each trial was performed by multivariable logistic regression. Fixed-effect meta-analyses odds ratios (ORs) per standard deviation (SD) of the association of PRS (quantitative) and hypertension across trials were estimated by inverse-variance weighting. PRSs were additionally stratified into quintiles, with the bottom quintile as the referent group. The OR of the association between hypertension and each quintile vs. the referent group was determined by logistic regression. The most significant PRS (quantitative)-hypertension association included up to 67 single-nucleotide variants (SNPs) associated with SBP (P = 0.0077, OR per SD = 1.31, 95% confidence interval (CI), 1.07-1.60), and up to 53 SNPs associated with DBP (P = 0.0209, OR per SD = 1.27, 95% CI, 1.04-1.56). Patients in the top quintile had a higher risk of developing bevacizumab-induced hypertension compared with patients in the bottom quintile using SNPs associated with SBP (P = 4.75 × 10^-4 , OR = 3.72, 95% CI, 1.84-8.16) and DBP (P = 0.076, OR = 1.83, 95% CI, 0.95-3.64). Genetic variants associated with essential hypertension, mainly SBP, increase the risk of severe bevacizumab-induced hypertension.

Bevacizumab-induced hypertension and proteinuria: a genome-wide study of more than 1000 patients

BACKGROUND

Hypertension and proteinuria are common bevacizumab-induced toxicities. No validated biomarkers are available for identifying patients at risk of these toxicities.

METHODS

A genome-wide association study (GWAS) meta-analysis was performed in 1039 bevacizumab-treated patients of European ancestry in four clinical trials (CALGB 40502, 40503, 80303, 90401). Grade ≥2 hypertension and proteinuria were recorded (CTCAE v.3.0). Single-nucleotide polymorphism (SNP)-toxicity associations were determined using a cause-specific Cox model adjusting for age and sex.

RESULTS

The most significant SNP associated with hypertension with concordant effect in three out of the four studies (p-value <0.05 for each study) was rs6770663 (A > G) in KCNAB1, with the G allele increasing the risk of hypertension (p-value = 4.16 × 10-6). The effect of the G allele was replicated in ECOG-ACRIN E5103 in 582 patients (p-value = 0.005). The meta-analysis of all five studies for rs6770663 led to p-value = 7.73 × 10-8, close to genome-wide significance. The most significant SNP associated with proteinuria was rs339947 (C > A, between DNAH5 and TRIO), with the A allele increasing the risk of proteinuria (p-value = 1.58 × 10-7).

CONCLUSIONS

The results from the largest study of bevacizumab toxicity provide new markers of drug safety for further evaluations. SNP in KCNAB1 validated in an independent dataset provides evidence toward its clinical applicability to predict bevacizumab-induced hypertension. ClinicalTrials.gov Identifier: NCT00785291 (CALGB 40502); NCT00601900 (CALGB 40503); NCT00088894 (CALGB 80303) and NCT00110214 (CALGB 90401).

Plasma levels of angiopoietin-2, VEGF-A, and VCAM-1 as markers of bevacizumab-induced hypertension: CALGB 80303 and 90401 (Alliance)

Hypertension is a common toxicity induced by bevacizumab and other antiangiogenic drugs. There are no biomarkers to predict the risk of bevacizumab-induced hypertension. This study aimed to identify plasma proteins related to the function of the vasculature to predict the risk of severe bevacizumab-induced hypertension. Using pretreated plasma samples from 398 bevacizumab-treated patients in two clinical trials (CALGB 80303 and 90401), the levels of 17 proteins were measured via ELISA. The association between proteins and grade 3 bevacizumab-induced hypertension was performed by calculating the odds ratio (OR) from logistic regression adjusting for age, sex, and clinical trial. Using the optimal cut-point of each protein, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for hypertension were estimated. Five proteins showed no difference in levels between clinical trials and were used for analyses. Lower levels of angiopoietin-2 (p = 0.0013, OR 3.41, 95% CI 1.67-7.55), VEGF-A (p = 0.0008, OR 4.25, 95% CI 1.93-10.72), and VCAM-1 (p = 0.0067, OR 2.68, 95% CI 1.34-5.63) were associated with an increased risk of grade 3 hypertension. The multivariable model suggests independent effects of angiopoietin-2 (p = 0.0111, OR 2.71, 95% CI 1.29-6.10), VEGF-A (p = 0.0051, OR 3.66, 95% CI 1.54-9.73), and VCAM-1 (p = 0.0308, OR 2.27, 95% CI 1.10-4.92). The presence of low levels of 2-3 proteins had an OR of 10.06 (95% CI 3.92-34.18, p = 1.80 × 10^-5) for the risk of hypertension, with sensitivity of 89.7%, specificity of 53.5%, PPV of 17.3%, and NPV of 97.9%. This is the first study providing evidence of plasma proteins with potential value to predict patients at risk of developing bevacizumab-induced hypertension.Clinical trial registration: ClinicalTrials.gov Identifier: NCT00088894 (CALGB 80303); and NCT00110214 (CALGB 90401).

Management of Side Effects in the Personalized Medicine Era: Chemotherapy-Induced Peripheral Neurotoxicity

Pharmacogenomics is a powerful tool to predict individual response to treatment, in order to personalize therapy, and it has been explored extensively in oncology practice. Not only efficacy on the malignant disease has been investigated but also the possibility to predict adverse effects due to drug administration. Chemotherapy-induced peripheral neurotoxicity (CIPN) is one of those. This potentially severe and long-lasting/permanent side effect of commonly administered anticancer drugs can severely impair quality of life (QoL) in a large cohort of long survival patients. So far, a pharmacogenomics-based approach in CIPN regard has been quite delusive, making a methodological improvement warranted in this field of interest: even the most refined genetic analysis cannot be effective if not applied correctly. Here we try to devise why it is so, suggesting how THE "bench-side" (pharmacogenomics) might benefit from and should cooperate with THE "bed-side" (clinimetrics), in order to make genetic profiling effective if applied to CIPN.

Mechanistic insights into the pathogenesis of microtubule-targeting agent-induced peripheral neuropathy from pharmacogenetic and functional studies

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity that affects 30%-40% of patients undergoing cancer treatment. Although multiple mechanisms of chemotherapy-induced neurotoxicity have been described in preclinical models, these have not been translated into widely effective strategies for the prevention or treatment of CIPN. Predictive biomarkers to inform therapeutic approaches are also lacking. Recent studies have examined genetic risk factors associated with CIPN susceptibility. This review provides an overview of the clinical and pathologic features of CIPN and summarizes efforts to identify target pathways through genetic and functional studies. Structurally and mechanistically diverse chemotherapeutics are associated with CIPN; however, the current review is focused on microtubule-targeting agents since these are the focus of most pharmacogenetic association and functional studies of CIPN. Genome-wide pharmacogenetic association studies are useful tools to identify not only causative genes and genetic variants but also genetic networks implicated in drug response or toxicity and have been increasingly applied to investigations of CIPN. Induced pluripotent stem cell-derived models of human sensory neurons are especially useful to understand the mechanistic significance of genomic findings. Combined genetic and functional genomic efforts to understand CIPN hold great promise for developing therapeutic approaches for its prevention and treatment.

A Multimodal Approach to Discover Biomarkers for Taxane-Induced Peripheral Neuropathy (TIPN): A Study Protocol

Introduction: Taxanes are a class of chemotherapeutics commonly used to treat various solid tumors, including breast and ovarian cancers. Taxane-induced peripheral neuropathy (TIPN) occurs in up to 70% of patients, impacting quality of life both during and after treatment. TIPN typically manifests as tingling and numbness in the hands and feet and can cause irreversible loss of function of peripheral nerves. TIPN can be dose-limiting, potentially impacting clinical outcomes. The mechanisms underlying TIPN are poorly understood. As such, there are limited treatment options and no tools to provide early detection of those who will develop TIPN. Although some patients may have a genetic predisposition, genetic biomarkers have been inconsistent in predicting chemotherapy-induced peripheral neuropathy (CIPN). Moreover, other molecular markers (eg, metabolites, mRNA, miRNA, proteins) may be informative for predicting CIPN, but remain largely unexplored. We anticipate that combinations of multiple biomarkers will be required to consistently predict those who will develop TIPN. Methods: To address this clinical gap of identifying patients at risk of TIPN, we initiated the Genetics and Inflammatory Markers for CIPN (GENIE) study. This longitudinal multicenter observational study uses a novel, multimodal approach to evaluate genomic variation, metabolites, DNA methylation, gene expression, and circulating cytokines/chemokines prior to, during, and after taxane treatment in 400 patients with breast cancer. Molecular and patient reported data will be collected prior to, during, and after taxane therapy. Multi-modal data will be used to develop a set of comprehensive predictive biomarker signatures of TIPN. Conclusion: The goal of this study is to enable early detection of patients at risk of developing TIPN, provide a tool to modify taxane treatment to minimize morbidity from TIPN, and improved patient quality of life. Here we provide a brief review of the current state of research into CIPN and TIPN and introduce the GENIE study design.

Genome-Wide Association Study of 2,093 Cases With Idiopathic Polyneuropathy and 445,256 Controls Identifies First Susceptibility Loci

Background: About one third of patients with chronic polyneuropathy have no obvious underlying etiology and are classified as having idiopathic polyneuropathy. The lack of knowledge about pathomechanisms and predisposing factors limits the development of effective prevention and treatment for these patients. We report the first genome-wide association study (GWAS) of idiopathic polyneuropathy.

Methods: Cases with idiopathic polyneuropathy and healthy controls were identified by linkage to hospital records. We performed genome-wide association studies using genetic data from two large population-based health studies, the Trøndelag Health Study (HUNT, 1,147 cases and 62,204 controls) and UK Biobank (UKB, 946 cases and 383,052 controls). In a two-stage analysis design, we first treated HUNT as a discovery cohort and UK Biobank as a replication cohort. Secondly, we combined the two studies in a meta-analysis. Downstream analyses included genetic correlation to other traits and diseases. We specifically examined previously reported risk loci, and genes known to cause hereditary polyneuropathy.

Results: No replicable risk loci were identified in the discovery-replication stage, in line with the limited predicted power of this approach. When combined in a meta-analysis, two independent loci reached statistical significance (rs7294354 in B4GALNT3, P-value 4.51 × 10⁻⁸) and (rs147738081 near NR5A2, P-value 4.75 × 10⁻⁸). Idiopathic polyneuropathy genetically correlated with several anthropometric measures, most pronounced for height, and with several pain-related traits.

Conclusions: In this first GWAS of idiopathic polyneuropathy we identify two risk-loci that indicate possible pathogenetic mechanisms. Future collaborative efforts are needed to replicate and expand on these findings.

Chemotherapy and peripheral neuropathy

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a major dose-limiting side effect of many anti-cancer agents, including taxanes, platinums, vinca alkaloids, proteasome inhibitors, immunomodulatory drugs, and antibody-drug conjugates. The resultant symptoms often persist post treatment completion and continue to impact on long-term function and quality of life for cancer survivors. At present, dose reduction remains the only strategy to prevent severe neuropathy, often leading clinicians to the difficult decision of balancing maximal treatment exposure and minimal long-lasting side effects. This review examines the clinical presentations of CIPN with each class of neurotoxic treatment, describing signs, symptoms, and long-term outcomes. We provide an update on the proposed mechanisms of nerve damage and review current data on clinical and genetic risk factors contributing to CIPN development. We also examine recent areas of research in the treatment and prevention of CIPN, with specific focus on current clinical trials and consensus recommendations for CIPN management.

Large-Scale Prospective Genome-Wide Association Study of Oxaliplatin in Stage II/III Colon Cancer and Neuropathy

IMPORTANCE

The severity of oxaliplatin (L-OHP)-induced peripheral sensory neuropathy (PSN) exhibits substantial interpatient variability, and some patients suffer from long-term, persisting PSN.

OBJECTIVE

To identify single-nucleotide polymorphisms (SNPs) predicting L-OHP-induced PSN using a genome-wide association study (GWAS) approach.

DESIGN, SETTING, PARTICIPANTS

A large prospective GWAS including 1,379 patients with stage II/III colon cancer who received L-OHP-based adjuvant chemotherapy (mFOLFOX6/CAPOX) under the phase II (JOIN/JFMC41) or the phase III (ACHIVE/JFMC47) trial.

MAIN OUTCOMES AND MEASURES

First, GWAS comparison of worst grade PSN (grade 0/1 vs. 2/3) was performed. Next, to minimize the impact of ambiguity in PSN grading, extreme PSN phenotypes were selected and analyzed by GWAS. SNPs that could predict time to recovery from PSN were also evaluated. In addition, SNPs associated with L-OHP-induced allergic reactions (AR) and time to disease recurrence were explored.

RESULTS

No SNPs exceeded the genome-wide significance (p < 5.0 × 10^-8) in either GWAS comparison of worst grade PSN, extreme PSN phenotypes, or time to recovery from PSN. Association study focusing on AR or time to disease recurrence also failed to reveal any significant SNPs.

CONCLUSION AND RELEVANCE

Our results highlight the challenges of utilizing SNPs for predicting susceptibility to L-OHP-induced PSN in daily clinical practice.

Integrating disease and drug-related phenotypes for improved identification of pharmacogenomic variants

Aim: To improve the identification and interpretation of pharmacogenetic variants through the integration of disease and drug-related traits. Materials & methods: We hypothesized that integrating genome-wide disease and pharmacogenomic data may drive new insights into drug toxicity and response by identifying shared genetic architecture. Pleiotropic variants were identified using a methodological framework incorporating colocalization analysis. Results: Using genome-wide association studies summary statistics from the UK Biobank, European Bioinformatics Institute genome-wide association studies catalog and the Pharmacogenomics Research Network, we validated pleiotropy at the ABCG2 locus between allopurinol response and gout and identified novel pleiotropy between antihypertensive-induced new-onset diabetes, Crohn's disease and inflammatory bowel disease at the IL18RAP/SLC9A4 locus. Conclusion: New mechanistic insights and genetic loci can be uncovered by identifying pleiotropy between disease and drug-related traits.

Exploring pharmacogenetics of paclitaxel- and docetaxel-induced peripheral neuropathy by evaluating the direct pharmacogenetic-pharmacokinetic and pharmacokinetic-neuropathy relationships

Introduction: Peripheral neuropathy (PN) is an adverse effect of several classes of chemotherapy including the taxanes. Predictive PN biomarkers could inform individualized taxane treatment to reduce PN and enhance therapeutic outcomes. Pharmacogenetics studies of taxane-induced PN have focused on genes involved in pharmacokinetics, including enzymes and transporters. Contradictory findings from these studies prevent translation of genetic biomarkers into clinical practice. Areas covered: This review discusses the progress toward identifying pharmacogenetic predictors of PN by assessing the evidence for two independent associations; the effect of pharmacogenetics on taxane pharmacokinetics and the evidence that taxane pharmacokinetics affects PN. Assessing these direct relationships allows the reader to understand the progress toward individualized taxane treatment and future research opportunities. Expert opinion: Paclitaxel pharmacokinetics is a major determinant of PN. Additional clinical trials are needed to confirm the clinical benefit of individualized dosing to achieve target paclitaxel exposure. Genetics does not meaningfully contribute to paclitaxel pharmacokinetics and may not be useful to inform dosing. However, genetics may contribute to PN sensitivity and could be useful for estimating patients' optimal paclitaxel exposure. For docetaxel, genetics has not been demonstrated to have a meaningful effect on pharmacokinetics and there is no evidence that pharmacokinetics determines PN.

Human Induced Pluripotent Stem Cell Derived Sensory Neurons are Sensitive to the Neurotoxic Effects of Paclitaxel

Chemotherapy‐induced peripheral neuropathy (CIPN) is a dose‐limiting adverse event associated with treatment with paclitaxel and other chemotherapeutic agents. The prevention and treatment of CIPN are limited by a lack of understanding of the molecular mechanisms underlying this toxicity. In the current study, a human induced pluripotent stem cell–derived sensory neuron (iPSC‐SN) model was developed for the study of chemotherapy‐induced neurotoxicity. The iPSC‐SNs express proteins characteristic of nociceptor, mechanoreceptor, and proprioceptor sensory neurons and show Ca²⁺ influx in response to capsaicin, α,β‐meATP, and glutamate. The iPSC‐SNs are relatively resistant to the cytotoxic effects of paclitaxel, with half‐maximal inhibitory concentration (IC₅₀) values of 38.1 µM (95% confidence interval (CI) 22.9–70.9 µM) for 48‐hour exposure and 9.3 µM (95% CI 5.7–16.5 µM) for 72‐hour treatment. Paclitaxel causes dose‐dependent and time‐dependent changes in neurite network complexity detected by βIII‐tubulin staining and high content imaging. The IC₅₀ for paclitaxel reduction of neurite area was 1.4 µM (95% CI 0.3–16.9 µM) for 48‐hour exposure and 0.6 µM (95% CI 0.09–9.9 µM) for 72‐hour exposure. Decreased mitochondrial membrane potential, slower movement of mitochondria down the neurites, and changes in glutamate‐induced neuronal excitability were also observed with paclitaxel exposure. The iPSC‐SNs were also sensitive to docetaxel, vincristine, and bortezomib. Collectively, these data support the use of iPSC‐SNs for detailed mechanistic investigations of genes and pathways implicated in chemotherapy‐induced neurotoxicity and the identification of novel therapeutic approaches for its prevention and treatment.

Taxane and epothilone-induced peripheral neurotoxicity: From pathogenesis to treatment

Taxane-induced peripheral neurotoxicity (TIPN) is the most common non-hematological side effect of taxane-based chemotherapy, and may result in dose reductions and discontinuations, having as such a detrimental effect on patients' overall survival. Epothilones share similar mechanism of action with taxanes. The typical TIPN clinical presentation is mainly comprised of numbness and paresthesia, in a stocking-and-glove distribution and may progress more proximally over time, with paclitaxel being more neurotoxic than docetaxel. Motor and autonomic involvement is less common, whereas an acute taxane-induced acute pain syndrome is frequent. Patient reported outcomes questionnaires, clinical evaluation, and instrumental tools offer complementary information in TIPN. Its electrodiagnostic features include reduced/abolished sensory action potentials, and less prominent motor involvement, in keeping with a length-dependent, axonal dying back predominately sensory neuropathy. TIPN is dose-dependent and may be reversible within months after the end of chemotherapy. The single and cumulative delivered dose of taxanes is considered the main risk factor of TIPN development. Apart from the cumulative dose, other risk factors for TIPN include demographic, clinical, and pharmacogenetic features with several single-nucleotide polymorphisms potentially linked with increased susceptibility of TIPN. There are currently no neuroprotective strategies to reduce the risk of TIPN, and symptomatic treatments are very limited. This review critically examines the pathogenesis, incidence, risk factors (both clinical and pharmacogenetic), clinical phenotype and management of TIPN.

The National Cancer Institute Clinical Trials Planning Meeting for Prevention and Treatment of Chemotherapy-Induced Peripheral Neuropathy

Although recent scientific advances have improved our understanding of basic biological mechanisms underlying chemotherapy-induced peripheral neuropathy (CIPN), few interventions are available to prevent or treat CIPN. Although some biological targets from preclinical studies show promise in nonhuman animal models, few targets have been translated to successful clinical trials. To address this problem, the National Cancer Institute's Symptom Management and Health-Related Quality of Life Steering Committee convened a meeting of experts in the CIPN and oncology symptom management fields to participate in a Clinical Trials Planning Meeting (CTPM). Investigators presented data from preclinical and translational studies for possible CIPN interventions; these were evaluated for readiness of randomized clinical trial testing by experts, and recommendations were provided. Breakout sessions were convened to discuss and develop future studies. The CTPM experts concluded that there is compelling evidence to move forward with selected pharmacological and nonpharmacological clinical trials for the prevention and treatment of CIPN. Several key feasibility issues need to be addressed, however. These include identification of optimal outcome measures to define the CIPN phenotype, establishment of parameters that guide the evaluation of clinically meaningful effects, and adoption of approaches for inclusion of translational and biomarker and/or genetic measures. The results of the CTPM provide support for conducting clinical trials that include both pharmacological and nonpharmacological approaches, alone or in combination, with biomarkers, genetics, or other measures designed to inform underlying CIPN mechanisms. Several working groups were formed to design rigorous CIPN clinical trials, the results of which are ongoing.

Pathogenesis of paclitaxel-induced peripheral neuropathy: A current review of in vitro and in vivo findings using rodent and human model systems

Paclitaxel (Brand name Taxol) is widely used in the treatment of common cancers like breast, ovarian and lung cancer. Although highly effective in blocking tumor progression, paclitaxel also causes peripheral neuropathy as a side effect in 60-70% of chemotherapy patients. Recent efforts by numerous labs have aimed at defining the underlying mechanisms of paclitaxel-induced peripheral neuropathy (PIPN). In vitro models using rodent dorsal root ganglion neurons, human induced pluripotent stem cells, and rodent in vivo models have revealed a number of molecular pathways affected by paclitaxel within axons of sensory neurons and within other cell types, such as the immune system and peripheral glia, as well skin. These studies revealed that paclitaxel induces altered calcium signaling, neuropeptide and growth factor release, mitochondrial damage and reactive oxygen species formation, and can activate ion channels that mediate responses to extracellular cues. Recent studies also suggest a role for the matrix-metalloproteinase 13 (MMP-13) in mediating neuropathy. These diverse changes may be secondary to paclitaxel-induced microtubule transport impairment. Human genetic studies, although still limited, also highlight the involvement of cytoskeletal changes in PIPN. Newly identified molecular targets resulting from these studies could provide the basis for the development of therapies with which to either prevent or reverse paclitaxel-induced peripheral neuropathy in chemotherapy patients.

Concerns regarding use of patient-reported outcomes in biomarker studies of chemotherapy-induced peripheral neuropathy

Clinician-rated toxicity data has been systematically collected within oncology clinical research using the National Cancer Institute’s CTCAE scale, providing estimates of the occurrence and severity of toxicity from cancer treatment. CTCAE is being supplemented by collection of patient-reported outcome (PRO) toxicity within clinical research and clinical practice, where PRO has demonstrable benefits. There is general agreement that PRO data is more sensitive and reliable than CTCAE data, particularly for subjective adverse effects. Based on this premise, researchers have begun to use PRO toxicity data collected within prospective clinical trials as the primary endpoint to discover pharmacogenetic and other predictive biomarkers of treatment-related toxicity. This perspective raises caution about the superiority of PRO data to CTCAE data for biomarker research, particularly in regards to chemotherapy-induced peripheral neuropathy (PN). The reader is provided an introduction to PRO and their integration into clinical research and practice, comparisons of PN data collected by PRO and CTCAE, examples of attempts to use PRO PN data for biomarker discovery, and evidence suggesting that PRO may not be superior to CTCAE for PN biomarker studies. The perspective concludes with a proposed approach for empirically testing whether PRO or CTCAE data is the better option for use in PN biomarker research, which can serve as a model for similar comparisons within other treatment-related toxicities.

Pharmacogenomic Biomarkers in Docetaxel Treatment of Prostate Cancer: From Discovery to Implementation

Prostate cancer is the fifth leading cause of male cancer death worldwide. Although docetaxel chemotherapy has been used for more than fifteen years to treat metastatic castration resistant prostate cancer, the high inter-individual variability of treatment efficacy and toxicity is still not well understood. Since prostate cancer has a high heritability, inherited biomarkers of the genomic signature may be appropriate tools to guide treatment. In this review, we provide an extensive overview and discuss the current state of the art of pharmacogenomic biomarkers modulating docetaxel treatment of prostate cancer. This includes (1) research studies with a focus on germline genomic biomarkers, (2) clinical trials including a range of genetic signatures, and (3) their implementation in treatment guidelines. Based on this work, we suggest that one of the most promising approaches to improve clinical predictive capacity of pharmacogenomic biomarkers in docetaxel treatment of prostate cancer is the use of compound, multigene pharmacogenomic panels defined by specific clinical outcome measures. In conclusion, we discuss the challenges of integrating prostate cancer pharmacogenomic biomarkers into the clinic and the strategies that can be employed to allow a more comprehensive, evidence-based approach to facilitate their clinical integration. Expanding the integration of pharmacogenetic markers in prostate cancer treatment procedures will enhance precision medicine and ultimately improve patient outcomes.

Biological predictors of chemotherapy-induced peripheral neuropathy (CIPN): MASCC neurological complications working group overview

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating condition associated with a number of chemotherapeutic agents. Drugs commonly implicated in the development of CIPN include platinum agents, taxanes, vinca alkaloids, bortezomib, and thalidomide analogues. As a drug response can vary between individuals, it is hypothesized that an individual's specific genetic variants could impact the regulation of genes involved in drug pharmacokinetics, ion channel functioning, neurotoxicity, and DNA repair, which in turn affect CIPN development and severity. Variations of other molecular markers may also affect the incidence and severity of CIPN. Hence, the objective of this review was to summarize the known biological (molecular and genomic) predictors of CIPN and discuss the means to facilitate progress in this field.

Fabrication of a Co-Culture System with Human Sweat Gland-Derived Cells and Peripheral Nerve Cells

The interaction of peripheral nerves with different cells of the skin is a relevant aspect of many physiological processes including nociception, temperature control, and wound healing. Here we describe a protocol for the setup of an indirect co-culture system of peripheral nerve cells and sweat gland-derived stem cells, which can be used to quantify neurite outgrowth.

Role of Germline Genetics in Identifying Survivors at Risk for Adverse Effects of Cancer Treatment

The growing population of cancer survivors often faces adverse effects of treatment, which have a substantial impact on morbidity and mortality. Although certain adverse effects are thought to have a significant heritable component, much work remains to be done to understand the role of germline genetic factors in the development of treatment-related toxicities. In this article, we review current understanding of genetic susceptibility to a range of adverse outcomes among cancer survivors (e.g., fibrosis, urinary and rectal toxicities, ototoxicity, chemotherapy-induced peripheral neuropathy, subsequent malignancies). Most previous research has been narrowly focused, investigating variation in candidate genes and pathways such as drug metabolism, DNA damage and repair, and inflammation. Few of the findings from these earlier candidate gene studies have been replicated in independent populations. Advances in understanding of the genome, improvements in technology, and reduction in laboratory costs have led to recent genome-wide studies, which agnostically interrogate common and/or rare variants across the entire genome. Larger cohorts of patients with homogeneous treatment exposures and systematic ascertainment of well-defined outcomes as well as replication in independent study populations are essential aspects of the study design and are increasingly leading to the discovery of variants associated with each of the adverse outcomes considered in this review. In the long-term, validated germline genetic associations hold tremendous promise for more precisely identifying patients at highest risk for developing adverse treatment effects, with implications for frontline therapy decision-making, personalization of long-term follow-up guidelines, and potential identification of targets for prevention or treatment of the toxicity.

Role for Nucleotide Excision Repair Gene Variants in Oxaliplatin-Induced Peripheral Neuropathy

PURPOSE

Oxaliplatin forms part of routine treatment of advanced colorectal cancer; however, it often causes severe peripheral neuropathy, resulting in treatment discontinuation. We sought to determine the molecular and cellular mechanism underlying this toxicity.

PATIENTS AND METHODS

We exome resequenced blood DNA samples from nine patients with advanced colorectal cancer who had severe peripheral neuropathy associated with oxaliplatin (PNAO) within 12 weeks of treatment. We Sanger sequenced the ERCC4 and ERCC6 open reading frames in 63 patients with PNAO and carried out targeted genotyping in 1,763 patients without PNAO. We tested the functionality of ERCC4 variants using viability and DNA repair assays in Schizosaccharomyces pombe and human cell lines after exposure to oxaliplatin and ultraviolet light.

RESULTS

Exome resequencing identified one patient carrying a novel germline truncating mutation in the nucleotide excision repair (NER) gene ERCC4. This mutation was functionally associated with sensitivity to oxaliplatin (P = 3.5 × 10-2). We subsequently found that multiple rare ERCC4 nonsynonymous variants were over-represented in affected individuals (P = 7.7 × 10-3) and three of these were defective in the repair of ultraviolet light-induced DNA damage (P < 1 × 10-3). We validated a role for NER genes in PNAO by finding that multiple rare ERCC6 nonsynonymous variants were similarly over-represented in affected individuals (P = 2.4 × 10-8). Excluding private variants, 22.2% of patients (14 of 63 patients) with PNAO carried Pro379Ser or Glu875Gly in ERCC4 or Asp425Ala, Gly446Asp, or Ser797Cys in ERCC6, compared with 8.7% of unaffected patients (152 of 1,750 patients; odds ratio, 3.0; 95% CI, 1.6 to 5.6; P = 2.5 × 10-4).

CONCLUSION

Our study provides evidence for a role of NER genes in PNAO, together with mechanistic insights.

Pharmacogenomics of Vincristine-Induced Peripheral Neuropathy Implicates Pharmacokinetic and Inherited Neuropathy Genes

Vincristine is an effective chemotherapeutic drug for various cancers, including acute lymphoblastic leukemia (ALL). Unfortunately, clinical utility is restricted by dose‐limiting vincristine‐induced peripheral neuropathies (VIPN). We sought to determine the association of VIPN with a recently identified risk variant, CEP72 rs924607, and drug absorption, distribution, metabolism, and excretion (ADME) gene variants in pediatric ALL. This was followed by a meta‐analysis of pharmacogenomic data from over 500 patients. CEP72 rs924607 was significantly associated with VIPN (P = 0.02; odds ratio (OR) = 3.4). ADME analyses identified associations between VIPN and ABCC1 rs3784867 (P = 5.34 × 10⁻⁵; OR = 4.9), and SLC5A7 rs1013940 (P = 9.00 × 10⁻⁴; OR= 8.6); genes involved in vincristine transport and inherited neuropathies, respectively. Meta‐analysis identified an association with a variant related to TTPA (rs10504361: P = 6.85 × 10⁻⁴; OR = 2.0), a heritable neuropathy‐related gene. This study provides essential corroboratory evidence for CEP72 rs924607 and highlights the importance of drug transporter and inherited neuropathy genes in VIPN.

Chemotherapy-induced peripheral neuropathy: evidence from genome-wide association studies and replication within multiple myeloma patients

Background

Based on the possible shared mechanisms of chemotherapy-induced peripheral neuropathy (CIPN) for different drugs, we aimed to aggregate results of all previously published genome-wide association studies (GWAS) on CIPN, and to replicate them within a cohort of multiple myeloma (MM) patients.

Methods

Following a systematic literature search, data for CIPN associated single nucleotide polymorphisms (SNPs) with P-values< 10^− 5 were extracted; these associations were investigated within a cohort of 983 German MM patients treated with bortezomib, thalidomide or vincristine. Cases were subjects that developed CIPN grade 2–4 while controls developed no or sub-clinical CIPN. Logistic regression with additive model was used.

Results

In total, 9 GWASs were identified from the literature on CIPN caused by different drugs (4 paclitaxel, 2 bortezomib, 1 vincristine, 1 docetaxel, and 1 oxaliplatin). Data were extracted for 526 SNPs in 109 loci. One hundred fourty-eight patients in our study population were CIPN cases (102/646 bortezomib, 17/63 thalidomide and 29/274 vincristine). In total, 13 SNPs in 9 loci were replicated in our population (p-value< 0.05). The four smallest P-values relevant to the nerve function were 0.0006 for rs8014839 (close to the FBXO33 gene), 0.004 for rs4618330 (close to the INTU gene), 0.006 for rs1903216 (close to the BCL6 gene) and 0.03 for rs4687753 (close to the IL17RB gene).

Conclusions

Replicated SNPs provide clues of the molecular mechanism of CIPN and can be strong candidates for further research aiming to predict the risk of CIPN in clinical practice, particularly rs8014839, rs4618330, rs1903216, and rs4687753, which showed relevance to the function of nervous system.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4728-4) contains supplementary material, which is available to authorized users.

Genome-wide association study identifies genes associated with neuropathy in patients with head and neck cancer

Neuropathic pain (NP), defined as pain initiated or caused by a primary lesion or dysfunction in the nervous system, is a debilitating chronic pain condition often resulting from cancer treatment. Among cancer patients, neuropathy during cancer treatment is a predisposing event for NP. To identify genetic variants influencing the development of NP, we conducted a genome-wide association study in 1,043 patients with squamous cell carcinoma of the head and neck, based on 714,494 tagging single-nucleotide polymorphisms (SNPs) (130 cases, 913 controls). About 12.5% of the patients, who previously had cancer treatment, had neuropathy-associated diagnoses, as defined using the ICD-9/ICD-10 codes. We identified four common SNPs representing four genomic regions: 7q22.3 (rs10950641; SNX8; P = 3.39 × 10⁻¹⁴), 19p13.2 (rs4804217; PCP2; P = 2.95 × 10⁻⁹), 3q27.3 (rs6796803; KNG1; P = 6.42 × 10⁻⁹) and 15q22.2 (rs4775319; RORA; P = 1.02 × 10⁻⁸), suggesting SNX8, PCP2, KNG1 and RORA might be novel target genes for NP in patients with head and neck cancer. Future experimental validation to explore physiological effects of the identified SNPs will provide a better understanding of the biological mechanisms underlying NP and may provide insights into novel therapeutic targets for treatment and management of NP.

Clinical and Genome-Wide Analysis of Cisplatin-Induced Peripheral Neuropathy in Survivors of Adult-Onset Cancer

Purpose: Our purpose was to characterize the clinical influences, genetic risk factors, and gene mechanisms contributing to persistent cisplatin-induced peripheral neuropathy (CisIPN) in testicular cancer survivors (TCSs).Experimental Design: TCS given cisplatin-based therapy completed the validated EORTC QLQ-CIPN20 questionnaire. An ordinal CisIPN phenotype was derived, and associations with age, smoking, excess drinking, hypertension, body mass index, diabetes, hypercholesterolemia, cumulative cisplatin dose, and self-reported health were examined for 680 TCS. Genotyping was performed on the Illumina HumanOmniExpressExome chip. Following quality control and imputation, 5.1 million SNPs in 680 genetically European TCS formed the input set. GWAS and PrediXcan were used to identify genetic variation and genetically determined gene expression traits, respectively, contributing to CisIPN. We evaluated two independent datasets for replication: Vanderbilt's electronic health database (BioVU) and the CALGB 90401 trial.Results: Eight sensory items formed a subscale with good internal consistency (Cronbach α = 0.88). Variables significantly associated with CisIPN included age at diagnosis (OR per year, 1.06; P = 2 × 10-9), smoking (OR, 1.54; P = 0.004), excess drinking (OR, 1.83; P = 0.007), and hypertension (OR, 1.61; P = 0.03). CisIPN was correlated with lower self-reported health (OR, 0.56; P = 2.6 × 10-9) and weight gain adjusted for years since treatment (OR per Δkg/m2, 1.05; P = 0.004). PrediXcan identified lower expressions of MIDN and RPRD1B, and higher THEM5 expression as associated with CisIPN (P value for each < 5 × 10-6) with replication of RPRD1B meeting significance criteria (Fisher combined P = 0.0089).Conclusions: CisIPN is associated with age, modifiable risk factors, and genetically determined expression level of RPRD1B Further study of implicated genes could elucidate the pathophysiologic underpinnings of CisIPN. Clin Cancer Res; 23(19); 5757-68. ©2017 AACR.

Germline genetic variants with implications for disease risk and therapeutic outcomes

Genetic testing has multiple clinical applications including disease risk assessment, diagnosis, and pharmacogenomics. Pharmacogenomics can be utilized to predict whether a pharmacologic therapy will be effective or to identify patients at risk for treatment-related toxicity. Although genetic tests are typically ordered for a distinct clinical purpose, the genetic variants that are found may have additional implications for either disease or pharmacology. This review will address multiple examples of germline genetic variants that are informative for both disease and pharmacogenomics. The discussed relationships are diverse. Some of the agents are targeted for the disease-causing genetic variant, while others, although not targeted therapies, have implications for the disease they are used to treat. It is also possible that the disease implications of a genetic variant are unrelated to the pharmacogenomic implications. Some of these examples are considered clinically actionable pharmacogenes, with evidence-based, pharmacologic treatment recommendations, while others are still investigative as areas for additional research. It is important that clinicians are aware of both the disease and pharmacogenomic associations of these germline genetic variants to ensure patients are receiving comprehensive personalized care.

A Mechanistic Understanding of Axon Degeneration in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapeutic agents cause many short and long term toxic side effects to peripheral nervous system (PNS) that drastically alter quality of life. Chemotherapy-induced peripheral neuropathy (CIPN) is a common and enduring disorder caused by several anti-neoplastic agents. CIPN typically presents with neuropathic pain, numbness of distal extremities, and/or oversensitivity to thermal or mechanical stimuli. This adverse side effect often requires a reduction in chemotherapy dosage or even discontinuation of treatment. Currently there are no effective treatment options for CIPN. While the underlying mechanisms for CIPN are not understood, current data identify a “dying back” axon degeneration of distal nerve endings as the major pathology in this disorder. Therefore, mechanistic understanding of axon degeneration will provide insights into the pathway and molecular players responsible for CIPN. Here, we review recent findings that expand our understanding of the pathogenesis of CIPN and discuss pathways that may be shared with the axonal degeneration that occurs during developmental axon pruning and during injury-induced Wallerian degeneration. These mechanistic insights provide new avenues for development of therapies to prevent or treat CIPN.

Institutional profile of pharmacogenetics within University of Michigan College of Pharmacy

The University of Michigan College of Pharmacy has made substantial investment in the area of pharmacogenomics to further bolster its activity in pharmacogenomics research, implementation and education. Four tenure-track faculty members have active research programs that focus primarily on the discovery of functional polymorphisms (HJ Zhu), and genetic associations with treatment outcomes in patients with cancer (DL Hertz), cardiovascular disease (JA Luzum) and psychiatric conditions (VL Ellingrod). Recent investments from the University and the College have accelerated the implementation of pharmacogenetics broadly across the institution and in targeted therapeutic areas. Students within the PharmD and other health science professions receive substantial instruction in pharmacogenomics, in preparation for careers in biomedical health in which they can contribute to the generation, dissemination and utilization of pharmacogenomics knowledge to improve patient care.

Chemotherapy-induced peripheral neurotoxicity: management informed by pharmacogenetics

The increasing availability of sophisticated methods to characterize human genetic variation has enabled pharmacogenetic data to be used not only to predict responses to treatment (in the context of so-called personalized medicine), but also to identify patients at high or low risk of specific treatment-related adverse effects. Over the past two decades, extensive attempts have been made to understand the genetic basis of chemotherapy-induced peripheral neurotoxicity (CIPN), one of the most severe non-haematological adverse effects of cancer treatment. Despite substantial efforts, however, the identification of a genetic profile that can detect patients at high risk of CIPN still represents an unmet need, as the information obtained from pharmacogenetic studies published so far is inconsistent at best. Among the reasons for these inconsistencies, methodological flaws and the poor reliability of existing tools for assessing CIPN features and severity are particularly relevant. This Review provides a critical update of the pharmacogenetics of CIPN, focusing on the studies published since 2011. Strategies for improving the reliability of future pharmacogenetic studies of CIPN are also discussed.

Application of stem cell derived neuronal cells to evaluate neurotoxic chemotherapy

The generation of induced pluripotent stem cells (iPSCs) and differentiation to cells composing major organs has opened up the possibility for a new model system to study adverse toxicities associated with chemotherapy. Therefore, we used human iPSC-derived neurons to study peripheral neuropathy, one of the most common adverse effects of chemotherapy and cause for dose reduction. To determine the utility of these neurons in investigating the effects of neurotoxic chemotherapy, we measured morphological differences in neurite outgrowth, cell viability as determined by ATP levels and apoptosis through measures of caspase 3/7 activation following treatment with clinically relevant concentrations of platinating agents (cisplatin, oxaliplatin and carboplatin), taxanes (paclitaxel, docetaxel and nab-paclitaxel), a targeted proteasome inhibitor (bortezomib), an antiangiogenic compound (thalidomide), and 5-fluorouracil, a chemotherapeutic that does not cause neuropathy. We demonstrate differential sensitivity of neurons to mechanistically distinct classes of chemotherapeutics. We also show a dose-dependent reduction of electrical activity as measured by mean firing rate of the neurons following treatment with paclitaxel. We compared neurite outgrowth and cell viability of iPSC-derived cortical (iCell® Neurons) and peripheral (Peri.4U) neurons to cisplatin, paclitaxel and vincristine. Goshajinkigan, a Japanese herbal neuroprotectant medicine, was protective against paclitaxel-induced neurotoxicity but not oxaliplatin as measured by morphological phenotypes. Thus, we have demonstrated the utility of human iPSC-derived neurons as a useful model to distinguish drug class differences and for studies of a potential neuroprotectant for the prevention of chemotherapy-induced peripheral neuropathy.

Genetic background influences susceptibility to chemotherapy-induced hematotoxicity

Hematotoxicity is a life-threatening side effect of many chemotherapy regimens. While clinical factors influence patient responses, genetic factors may also play an important role. We sought to identify genomic loci that influence chemotherapy-induced hematotoxicity by dosing Diversity Outbred mice with one of three chemotherapy drugs; doxorubicin, cyclophosphamide or docetaxel. We observed that each drug had a distinct effect on both the changes in blood cell sub-populations and the underlying genetic architecture of hematotoxicity. For doxorubicin, we mapped the change in cell counts before and after dosing and found that alleles of ATP-binding cassette B1B (Abcb1b) on chromosome 5 influence all cell populations. For cyclophosphamide and docetaxel, we found that each cell population was influenced by distinct loci, none of which overlapped between drugs. These results suggest that susceptibility to chemotherapy-induced hematotoxicity is influenced by different genes for different chemotherapy drugs.

Pathophysiology of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced neuropathy is a common, dose-dependent adverse effect of several antineoplastics. It can lead to detrimental dose reductions and discontinuation of treatment, and severely affects the quality of life of cancer survivors. Clinically, chemotherapy-induced peripheral neuropathy presents as deficits in sensory, motor, and autonomic function which develop in a glove and stocking distribution due to preferential effects on longer axons. The pathophysiological processes are multi-factorial and involve oxidative stress, apoptotic mechanisms, altered calcium homeostasis, axon degeneration and membrane remodeling as well as immune processes and neuroinflammation. This review focusses on the commonly used antineoplastic substances oxaliplatin, cisplatin, vincristine, docetaxel, and paclitaxel which interfere with the cancer cell cycle-leading to cell death and tumor degradation-and cause severe acute and chronic peripheral neuropathies. We discuss drug mechanism of action and pharmacokinetic disposition relevant to the development of peripheral neuropathy, the epidemiology and clinical presentation of chemotherapy-induced neuropathy, emerging insight into genetic susceptibilities as well as current understanding of the pathophysiology and treatment approaches.

Genome-Wide Association Studies of Chemotherapeutic Toxicities: Genomics of Inequality

With an estimated global population of cancer survivors exceeding 32 million and growing, there is a heightened awareness of the long-term toxicities resulting from cancer treatments and their impact on quality of life. Unexplained heterogeneity in the persistence and development of toxicities, as well as an incomplete understanding of their mechanisms, have generated a growing need for the identification of predictive pharmacogenomic markers. Early studies addressing this need used a candidate gene approach; however, over the last decade, unbiased and comprehensive genome-wide association studies (GWAS) have provided markers of phenotypic risk and potential targets to explore the mechanistic and regulatory pathways of biological functions associated with chemotherapeutic toxicity. In this review, we provide the current status of GWAS of chemotherapeutic toxicities with an emphasis on examining the ancestral diversity of the representative cohorts within these studies. Persistent calls to incorporate both ancestrally diverse and/or admixed populations into genomic efforts resulted in a recent rise in the number of studies utilizing cohorts of East Asian descent; however, few pharmacogenomic studies to date include cohorts of African, Indigenous American, Southwest Asian, and admixed populations. Through comprehensively evaluating sample size, composition by ancestry, genome-wide significant variants, and population-specific minor allele frequencies as reported by HapMap/dbSNP using NCBI PubMed and the NHGRI-EBI GWAS Catalog, we illustrate how allele frequencies and effect sizes tend to vary among individuals of differing ancestries. In an era of personalized medicine, the lack of diversity in genome-wide studies of anticancer agent toxicity may contribute to the health disparity gap. Clin Cancer Res; 23(15); 4010-9. ©2017 AACR.

Variants in WFS1 and Other Mendelian Deafness Genes Are Associated with Cisplatin-Associated Ototoxicity

Purpose: Cisplatin is one of the most commonly used chemotherapy drugs worldwide and one of the most ototoxic. We sought to identify genetic variants that modulate cisplatin-associated ototoxicity (CAO).Experimental Design: We performed a genome-wide association study (GWAS) of CAO using quantitative audiometry (4-12 kHz) in 511 testicular cancer survivors of European genetic ancestry. We performed polygenic modeling and functional analyses using a variety of publicly available databases. We used an electronic health record cohort to replicate our top mechanistic finding.Results: One SNP, rs62283056, in the first intron of Mendelian deafness gene WFS1 (wolframin ER transmembrane glycoprotein) and an expression quantitative trait locus (eQTL) for WFS1 met genome-wide significance for association with CAO (P = 1.4 × 10^-8). A significant interaction between cumulative cisplatin dose and rs62283056 genotype was evident, indicating that higher cisplatin doses exacerbate hearing loss in patients with the minor allele (P = 0.035). The association between decreased WFS1 expression and hearing loss was replicated in an independent BioVU cohort (n = 18,620 patients, Bonferroni adjusted P < 0.05). Beyond this top signal, we show CAO is a polygenic trait and that SNPs in and near 84 known Mendelian deafness genes are significantly enriched for low P values in the GWAS (P = 0.048).Conclusions: We show for the first time the role of WFS1 in CAO and document a statistically significant interaction between increasing cumulative cisplatin dose and rs62283056 genotype. Our clinical translational results demonstrate that pretherapy patient genotyping to minimize ototoxicity could be useful when deciding between cisplatin-based chemotherapy regimens of comparable efficacy with different cumulative doses. Clin Cancer Res; 23(13); 3325-33. ©2016 AACR.