Genetic advances uncover mechanisms of chemotherapy-induced peripheral neuropathy

Lower urinary dysfunction as a long-term effect of childhood vincristine treatment, with potential influences by sex and dose

Vincristine (VCR) is one of the most widely used chemotherapy agents in treating pediatric cancer. Nonetheless, it is known to cause dose-dependent neurotoxicity which can impact virtually every organ system. Despite its widespread use, the precise impact of VCR on the lower urinary tract (LUT) remains inadequately elucidated. Our initial clinical and translational investigations suggest a sex-specific influence of childhood VCR exposure on LUT function. Thus, the current study aimed to investigate the late effects of systemic VCR exposure on LUT physiology and the underlying mechanisms, focusing on dosage and male-sex, employing juvenile CD-1 mice as a model. Male mice subjected to VCR exhibited augmented functional bladder capacity accompanied by frequent non-void contractions during awake cystometry, alongside mast cell accumulation within the bladder, compared to the saline-treated control group. Noteworthy functional changes were observed in bladder strips from the VCR group, including decreased nerve-mediated contraction, heightened contractile responses to cholinergic and purinergic agonists, enhanced responsiveness to histamine-primarily via histamine receptor 1 (Hrh1)-and an augmented relaxation effect with compound 48/80 (a mast cell degranulator), relative to the control group. Significant changes in gene expression levels associated with neuroinflammation and nociception were observed in both the bladder and lumbosacral dorsal root ganglia (Ls-DRG) of the VCR group. These findings suggest that VCR exposure during childhood, particularly in males, triggers neuroimmune responses in the bladder and Ls-DRG, amplifying responsiveness to neurotransmitters in the bladder, thereby contributing to LUT dysfunction characterized by a mixed bladder phenotype as a late effect during survivorship.

The Challenges in Clinical Diagnosis of Trigeminal Neuralgia: A Review

The lack of established laboratory tests or biomarkers for trigeminal neuralgia (TN) makes diagnosing this relatively rare condition extremely challenging. Trigeminal nerve compression observable on magnetic resonance imaging may indicate TN, but many patients do not have visible lesions or compression. In particular, TN may be confused with migraine, cluster headache, temporomandibular disorder, and other types of headache. An accurate diagnosis is imperative for proper treatment since these conditions do not respond to the same treatment. Many symptoms of these headaches can be vague or overlap, and clinicians depend in large measure on the subjective reports of their patients. Nevertheless, it is imperative to diagnose TN better, which can cause excruciating pain, reduce the quality of life, and even result in disability. It is possible that TN is underestimated.

Using maximum plasma concentration (Cmax) to personalize taxane treatment and reduce toxicity

Taxanes are a widely used class of anticancer agents that play a vital role in the treatment of a variety of cancers. However, toxicity remains a major concern of using taxane drugs as some toxicities are highly prevalent, they can not only adversely affect patient prognosis but also compromise the overall treatment plan. Among all kinds of factors that associated with taxane toxicity, taxane exposure has been extensively studied, with different pharmacokinetic (PK) parameters being used as toxicity predictors. Compared to other widely used predictors such as the area under the drug plasma concentration curve versus time (AUC) and time above threshold plasma drug concentration, maximum plasma concentration (Cmax) is easier to collect and shows promise for use in clinical practice. In this article, we review the previous research on using Cmax to predict taxane treatment outcomes. While Cmax and toxicity have been extensively studied, research on the relationship between Cmax and efficacy is lacking. Most of the articles find a positive relationship between Cmax and toxicity but several articles have contradictory findings. Future clinical trials are needed to validate the relationship between Cmax and treatment outcome and determine whether Cmax can serve as a useful surrogate endpoint of taxane treatment efficacy.

Schwann Cell-Derived Exosomes Ameliorate Paclitaxel-Induced Peripheral Neuropathy Through the miR-21-Mediated PTEN Signaling Pathway

Paclitaxel-induced peripheral neuropathy (PIPN) is a neurological disorder resulting from paclitaxel (PTX) treatment for cancer patients. There are currently no drugs available that can definitively prevent or treat PIPN. Exosomes are cell-secreted nanoscale vesicles that mediate communication between neurons and glial cells. We found that Schwann cell-derived exosomes (SC-EXOs) robustly improved PIPN both in vitro and in vivo. In vivo studies showed that SC-EXOs were able to alleviate PTX-induced mechanical nociceptive sensitization in rats. Pathomorphological analysis showed that SC-EXOs ameliorated PTX-induced plantar intraepidermal nerve fiber loss and dorsal root ganglion (DRG) injury. Additionally, the results of in vitro studies showed that SC-EXOs had significant protective effects on the DRG cells damaged by PTX, and did not affect the antitumor effect of PTX against Hela cells. Further, mechanism research revealed that SC-EXOs promoted axonal regeneration and protected damaged neurons by upregulating miR-21 to repress the phosphatase and tensin homolog (PTEN) pathway, which could improve PIPN. Taken together, these findings suggest that SC-EXOs ameliorate PTX-induced peripheral neuropathy via the miR-21-mediated PTEN signaling pathway, which provides a novel strategy for the treatment of PIPN.

GSTM1 and GSTT1 polymorphisms associated with pain in a chemotherapy-induced peripheral neuropathy cohort

PURPOSE

Chemotherapy induced peripheral neuropathy (CIPN) is a debilitating condition that is a direct consequence of receiving cancer treatment. The molecular aetiology of CIPN is not well understood, and it is theorised that there may be a genetic component. Genetic polymorphisms in Glutathione-S Transferase (GST) genes, including GSTT1, GSTM1 and GSTP1, encode for enzymes known to metabolise drugs used in chemotherapy, and have been theorised to be associated with CIPN. This study aimed to investigate four markers in these genes for an association in a mixed cancer cohort in relation to CIPN (n = 172).

METHODS

CIPN was measured using the neuropathy item from the Patient Reported Outcome Common Terminology Criteria for Adverse Event (PRO-CTCAE) assessment. Genotyping for all samples was performed using PCR for the GSTM1 and GSTT1 null variants and restriction fragment length polymorphisms for the GSTP1 and GSTM1 polymorphisms.

RESULTS

No associations were found for the GST gene markers in relation to CIPN within our study, or CIPN severity. Longitudinal stratification of the CIPN phenotypes to examine links for neuropathy, identified nominally significant protective associations with the GSTM* null allele (p-value = 0.038, OR = 0.55) and the presence of pain at month 2 of treatment, as well as a risk factor for pain related month 2 of treatment for individuals with the GSTT1*null allele (p-value = 0.030, OR = 1.64). Higher severity of pain in patients with CIPN persisted at each time-point compared to those without CIPN.

CONCLUSION

No significant results for an association between CIPN with polymorphisms in GSTM1, GSTT1 and GSTP1 were identified. However, associations for the GSTM1¬-null and GSTT1-null polymorphisms with pain at month 2 following chemotherapy were identified.

Neuroimaging reveals a potential brain-based pre-existing mechanism that confers vulnerability to development of chronic painful chemotherapy-induced peripheral neuropathy

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating condition impacting 30% of cancer survivors. This study is the first to explore whether a brain-based vulnerability to chronic sensory CIPN exists.

METHODS

This prospective, multicentre cohort study recruited from three sites across Scotland. Brain functional MRI (fMRI) scans (3 Tesla) were carried out on chemotherapy naïve patients at a single fMRI centre in Edinburgh, Scotland. Nociceptive stimuli (with a 256 mN monofilament) were administered during the fMRI. Development of chronic sensory/painful CIPN (CIPN+) was determined based upon European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Chemotherapy-Induced Peripheral Neuropathy 20 changes conducted 9 months after chemotherapy, and imaging data analysed using standard software.

RESULTS

Of 30 patients recruited (two lung, nine gynaecological, and 19 colorectal malignancies), data from 20 patients at 9 months after chemotherapy was available for analysis. Twelve were classified as CIPN+ (mean age, 63.2[9.6] yr, 9.6; six female), eight as CIPN- (mean age 62.9 [SD 5.5] yr, four female). In response to punctate stimulation, group contrast analysis showed that CIPN+ compared with CIPN- had robust activity in sensory, motor, attentional, and affective brain regions. An a priori chosen region-of-interest analysis focusing on the periaqueductal grey, an area hypothesised as relevant for developing CIPN+, showed significantly increased responses in CIPN- compared with CIPN+ patients. No difference in subcortical volumes between CIPN+ and CIPN- patients was detected.

CONCLUSIONS

Before administration of any chemotherapy or appearance of CIPN symptoms, we observed altered patterns of brain activity in response to nociceptive stimulation in patients who later developed chronic sensory CIPN. This suggests the possibility of a pre-existing vulnerability to developing CIPN centred on brainstem regions of the descending pain modulatory system.

Towards a mechanistic understanding of axon transport and endocytic changes underlying paclitaxel-induced peripheral neuropathy

Paclitaxel is a common chemotherapeutic agent widely used to treat solid cancer. However, it frequently causes peripheral sensory neuropathy, resulting in sensory abnormalities and pain in patients receiving treatment for cancer. As one of the most widely used chemotherapeutics, many preclinical studies on paclitaxel-induced peripheral neuropathy (PIPN) have been performed. Yet, there remain no effective options for treatment or prevention. Due to paclitaxel's ability to bind to and stabilize microtubules, a change in microtubule dynamics and subsequent disruptions in axonal transport has been predicted as a major underlying cause of paclitaxel-induced toxicity. However, the systemic understanding of PIPN mechanisms is largely incomplete, and various phenotypes have not been directly attributed to microtubule-related effects. This review aims to provide an overview of the literature involving paclitaxel-induced alteration in microtubule dynamics, axonal transport, and endocytic changes. It also aims to provide insights into how the microtubule-mediated hypothesis may relate to various phenotypes reported in PIPN studies.

Mechanosensory encoding dysfunction emerges from cancer-chemotherapy interaction

Persistent sensory, motor and cognitive disabilities comprise chemotherapy-induced neural disorders (CIND) that limit quality of life with little therapeutic relief for cancer survivors. Our recent preclinical study provides new insight into a condition impacting the severity of chronic CIND. We find that sensorimotor disability observed following cancer treatment exceeds that attributable to chemotherapy alone. A possible explanation for intensified disability emerged from evidence that codependent effects of cancer and chemotherapy amplify defective firing in primary sensory neurons supplying one type of low threshold mechanosensory receptor (LTMR). Here we test whether cancer's modification of chemotherapy-induced sensory defects generalizes across eight LTMR submodalities that collectively generate the signals of origin for proprioceptive and tactile perception and guidance of body movement. Preclinical study enabled controlled comparison of the independent contributions of chemotherapy and cancer to their clinically relevant combined effects. We compared data sampled from rats that were otherwise healthy or bearing colon cancer and treated, or not, with human-scaled, standard-of-care chemotherapy with oxaliplatin. Action potential firing patterns encoding naturalistic mechanical perturbations of skeletal muscle and skin were measured electrophysiologically in vivo from multiple types of LTMR neurons. All expressed aberrant encoding of dynamic and/or static features of mechanical stimuli in healthy rats treated with chemotherapy, and surprisingly also by some LTMRs in cancer-bearing rats that were not treated. By comparison, chemotherapy and cancer in combination worsened encoding aberrations, especially in slowly adapting LTMRs supplying both muscle and glabrous skin. Probabilistic modeling best predicted observed encoding defects when incorporating interaction effects of cancer and chemotherapy. We conclude that for multiple mechanosensory submodalities, the severity of encoding defects is modulated by a codependence of chemotherapy side effects and cancer's systemic processes. We propose that the severity of CIND might be reduced by therapeutically targeting the mechanisms, yet to be determined, by which cancer magnifies chemotherapy's neural side effects as an alternative to reducing chemotherapy and its life-saving benefits.

Genome-wide association study of aromatase inhibitor discontinuation due to musculoskeletal symptoms

OBJECTIVE

Aromatase inhibitors (AIs) are commonly used to treat hormone receptor positive (HR +) breast cancer. AI-induced musculoskeletal syndrome (AIMSS) is a common toxicity that causes AI treatment discontinuation. The objective of this genome-wide association study (GWAS) was to identify genetic variants associated with discontinuation of AI therapy due to AIMSS and attempt to replicate previously reported associations.

METHODS

In the Exemestane and Letrozole Pharmacogenetics (ELPh) study, postmenopausal patients with HR + non-metastatic breast cancer were randomized to letrozole or exemestane. Genome-wide genotyping of germline DNA was conducted followed by imputation. Each imputed variant was tested for association with time-to-treatment discontinuation due to AIMSS using a Cox proportional hazards model assuming additive genetic effects and adjusting for age, baseline pain score, prior taxane treatment, and AI arm. Secondary analyses were conducted within each AI arm and analyses of candidate variants previously reported to be associated with AIMSS risk.

RESULTS

Four hundred ELPh participants were included in the combined analysis. Two variants surpassed the genome-wide significance level in the primary analysis (p value < 5 × 10-8), an intronic variant (rs79048288) within CCDC148 (HR = 4.42, 95% CI: 2.67-7.33) and an intergenic variant (rs912571) upstream of PPP1R14C (HR = 0.30, 95% CI: 0.20-0.47). In the secondary analysis, rs74418677, which is known to be associated with expression of SUPT20H, was significantly associated with discontinuation of letrozole therapy due to AIMSS (HR = 5.91, 95% CI: 3.16-11.06). We were able to replicate associations for candidate variants previously reported to be associated with AIMSS in this cohort, but were not able to replicate associations for any other variants previously reported in other patient cohorts.

CONCLUSIONS

Our GWAS findings identify several candidate variants that may be associated with AIMSS risk from AI generally or letrozole specifically. Validation of these associations in independent cohorts is needed before translating these findings into clinical practice to improve treatment outcomes in patients with HR + breast cancer.

Genetic polymorphism of pleiotrophin is associated with pain experience in Japanese adults: Case-control study

Genetic factors play a role in individual differences in pain experience. Here, we performed a genome-wide association study (GWAS) to identify novel loci regulating pain processing. We conducted a 2-stage GWAS and the candidate single-nucleotide polymorphisms (SNPs) association study on pain experience using an exploratory cohort of patients with cancer pain. The confirmatory cohort comprised of participants from the general population with and without habitual use of analgesic medication. In the exploratory cohort, we evaluated pain intensity using a numerical rating scale, recorded daily opioid dosages, and calculated pain reduction rate. In the confirmatory cohort, pain experience was defined as habitual nonsteroidal anti-inflammatory drug usage. Using linear regression models, we identified candidate SNP in the exploratory samples, and tested the association between phenotype and experienced pain in the confirmatory samples. We found 1 novel SNP (rs11764598)-located on the gene encoding for pleiotrophin on chromosome 7-that passed the genome-wide suggestive significance at 20% false discovery rate (FDR) correction in the exploratory samples of patients with cancer pain (P = 1.31 × 10-7, FDR = 0.101). We confirmed its significant association with daily analgesic usage in the confirmatory cohort (P = .028), although the minor allele affected pain experience in an opposite manner. We identified a novel genetic variant associated with pain experience. Further studies are required to validate the role of pleiotrophin in pain processing.

Cellular Pathogenesis of Chemotherapy-Induced Peripheral Neuropathy: Insights From Drosophila and Human-Engineered Skin Models

Chemotherapy-induced peripheral neuropathy (CIPN) is a highly prevalent and complex condition arising from chemotherapy cancer treatments. Currently, there are no treatment or prevention options in the clinic. CIPN accompanies pain-related sensory functions starting from the hands and feet. Studies focusing on neurons in vitro and in vivo models significantly advanced our understanding of CIPN pathological mechanisms. However, given the direct toxicity shown in both neurons and non-neuronal cells, effective in vivo or in vitro models that allow the investigation of neurons in their local environment are required. No single model can provide a complete solution for the required investigation, therefore, utilizing a multi-model approach would allow complementary advantages of different models and robustly validate findings before further translation. This review aims first to summarize approaches and insights from CIPN in vivo models utilizing small model organisms. We will focus on Drosophila melanogaster CIPN models that are genetically amenable and accessible to study neuronal interactions with the local environment in vivo. Second, we will discuss how these findings could be tested in physiologically relevant vertebrate models. We will focus on in vitro approaches using human cells and summarize the current understanding of engineering approaches that may allow the investigation of pathological changes in neurons and the skin environment.

Sexual dimorphic impacts of systemic vincristine on lower urinary tract function

Vincristine (VCR) is one of the most common chemotherapy agents used in pediatric oncology. Despite the well-known VCR-induced peripheral neuropathy, potential impacts of VCR on lower urinary tract (LUT) function remain poorly defined. We investigated the effects of systemic VCR exposure in childhood on LUT function by using juvenile mice treated with VCR (4 mg/kg) or saline and evaluated at 5 weeks later. VCR induced a decreased urinary frequency with increased functional bladder capacity and non-void contractions. There were no changes in detrusor contractility between the groups. VCR exposure caused sexual dimorphic changes; in females, increased intravesical pressure at micturition and downregulations of a major player in bladder afferent firing, Htr3b, in the bladders, and Cav1.2 in the lumbosacral dorsal root ganglia (Ls-DRG), while male mice displayed increases in bladder compliance and detrusor activity, upregulations of IL-2, Trpa1 and Itga1 in the bladders and neuroinflammation-related genes, P2×4, P2×7, IL-2 and CD68 in the Ls-DRG. These results suggest that that systemic VCR exposure caused sensory neuropathy via sex-dimorphic mechanisms, leading to altered LUT function. These changes might clinically present as gender-specific signs or symptoms of LUT dysfunction, and follow-up urological assessment may be of benefit for pediatric cancer patients treated with VCR.

Genetic variants predictive of chemotherapy-induced peripheral neuropathy symptoms in gynecologic cancer survivors

OBJECTIVE

To identify genetic variants associated with chemotherapy-induced peripheral neuropathy (CIPN) symptoms among gynecologic cancer survivors and determine the variants' predictive power in addition to age and clinical factors at time of diagnosis.

METHODS

Participants of a prospective cohort study on gynecologic cancers provided a DNA saliva sample and reported CIPN symptoms (FACT/GOG-Ntx). Genotyping of 23 single nucleotide polymorphisms (SNPs) previously identified as related to platinum- or taxane-induced neuropathy was performed using iPLEX Gold method. Risk allele carrier frequencies of 19 SNPs that passed quality checks were compared between those with/without high CIPN symptoms using logistic regression, adjusting for age. Receiver operating characteristic (ROC) curves using clinical risk factors (age, diabetes, BMI, Charlson Comorbidity Index, previous cancer diagnosis) with and without the identified SNPs were compared.

RESULTS

107 individuals received platinum or taxane-based chemotherapy and provided sufficient DNA for analysis. Median age was 65.1 years; 39.6% had obesity and 8.4% diabetes; most had ovarian (58.9%) or uterine cancer (29.0%). Two SNPs were significantly associated with high CIPN symptomatology: rs3753753 in GPX7, OR = 2.55 (1.13, 5.72) and rs139887 in SOX10, 2.66 (1.18, 6.00). Including these two SNPs in a model with clinical characteristics led to an improved AUC for CIPN symptomatology (0.65 vs. 0.74, p = 0.04).

CONCLUSIONS

Genetic and clinical characteristics were predictive of higher CIPN symptomatology in gynecologic cancer survivors, and combining these factors resulted in superior predictive power compared with a model with clinical factors only. Prospective validation and assessment of clinical utility are warranted.

Current opinion on the pharmacogenomics of paclitaxel-induced toxicity

Introduction: Paclitaxel is a microtubule stabilizer that is currently one of the most utilized chemotherapeutic agents. Its efficacy in breast, uterine, lung and other neoplasms made its safety profile enhancement a subject of great interest. Neurotoxicity is the most common paclitaxel-associated toxicities. In addition, hypersensitivity reactions, hematological, gastrointestinal, and cardiac toxicities are all encountered.Areas covered: The current review explores paclitaxel-induced toxicities mechanisms and risk factors. Studies investigating these toxicities pharmacogenomic biomarkers are reviewed and summarized. There is a limited margin of consistency between the retrieved associations. Variants in genes related to neuro-sensitivity are the most promising candidates for future studies.Expert opinion: Genome-wide association studies highlighted multiple-candidate biomarkers relevant to neuro-sensitivity. Most of the identified paclitaxel-neurotoxicity candidate genes are derived from congenital neuropathy and diabetic-induced neurotoxicity pathways. Future studies should explore these sets of genes while considering the multifactorial nature of paclitaxel-induced neurotoxicity. In the absence of certain paclitaxel-toxicity biomarkers, future research should avoid earlier studies' caveats. Genes in paclitaxel's pharmacokinetic pathways could not provide consistent results in any of its associated toxicities. There is a need to dig deeper into toxicity-development mechanisms and personal vulnerability factors, rather than targeting only the genes suspected to affect drug exposure.

Planning and Conducting a Pharmacogenetics Association Study

Pharmacogenetics (PGx) association studies are used to discover, replicate, and validate the association between an inherited genotype and a treatment outcome. The objective of this tutorial is to provide trainees and novice PGx researchers with an overview of the major decisions that need to be made when designing and conducting a PGx association study. The first critical decision is to determine whether the objective of the study is discovery, replication, or validation. Next, the researcher must identify a patient cohort that has all of the data necessary to conduct the intended analysis. Then, the investigator must select and define the treatment outcome, or phenotype, that will be analyzed. Next, the investigator must determine what genotyping approach and genetic data will be included in the analysis. Finally, the association between the genotype and phenotype is tested using some statistical analysis methodology. This tutorial is divided into five sections; each section describes commonly used approaches and provides suggestions and resources for designing and conducting a PGx association study. Successful PGx association studies are necessary to discover and validate associations between inherited genetic variation and treatment outcomes, which enable clinical translation to improve efficacy and reduce toxicity of treatment.

Integrins protect sensory neurons in models of paclitaxel-induced peripheral sensory neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a major side effect from cancer treatment with no known method for prevention or cure in clinics. CIPN often affects unmyelinated nociceptive sensory terminals. Despite the high prevalence, molecular and cellular mechanisms that lead to CIPN are still poorly understood. Here, we used a genetically tractable Drosophila model and primary sensory neurons isolated from adult mouse to examine the mechanisms underlying CIPN and identify protective pathways. We found that chronic treatment of Drosophila larvae with paclitaxel caused degeneration and altered the branching pattern of nociceptive neurons, and reduced thermal nociceptive responses. We further found that nociceptive neuron-specific overexpression of integrins, which are known to support neuronal maintenance in several systems, conferred protection from paclitaxel-induced cellular and behavioral phenotypes. Live imaging and superresolution approaches provide evidence that paclitaxel treatment causes cellular changes that are consistent with alterations in endosome-mediated trafficking of integrins. Paclitaxel-induced changes in recycling endosomes precede morphological degeneration of nociceptive neuron arbors, which could be prevented by integrin overexpression. We used primary dorsal root ganglia (DRG) neuron cultures to test conservation of integrin-mediated protection. We show that transduction of a human integrin β-subunit 1 also prevented degeneration following paclitaxel treatment. Furthermore, endogenous levels of surface integrins were decreased in paclitaxel-treated mouse DRG neurons, suggesting that paclitaxel disrupts recycling in vertebrate sensory neurons. Altogether, our study supports conserved mechanisms of paclitaxel-induced perturbation of integrin trafficking and a therapeutic potential of restoring neuronal interactions with the extracellular environment to antagonize paclitaxel-induced toxicity in sensory neurons.

Peripheral Neuropathy under Oncologic Therapies: A Literature Review on Pathogenetic Mechanisms

Peripheral neurologic complications are frequent adverse events during oncologic treatments and often lead to dose reduction, administration delays with time elongation of the therapeutic plan and, not least, worsening of patients’ quality of life. Experience skills are required to recognize symptoms and clinical evidences and the collaboration between different health professionals, in particular oncologists and hospital pharmacists, grants a correct management of this undesirable occurrence. Some classes of drugs (platinates, vinca alkaloids, taxanes) typically develop this kind of side effect, but the genesis of chemotherapy-induced peripheral neuropathy is not linked to a single mechanism. This paper aims from one side at summarizing and explaining all the scattering mechanisms of chemotherapy-induced peripheral neuropathy through a detailed literature revision, on the other side at finding new approaches to possible treatments, in order to facilitate the collaboration between oncologists, hematologists and hospital pharmacists.

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.

Precise uncertain significance prediction using latent space matrix factorization models: genomics variant and heterogeneous clinical data-driven approaches

Several studies to date have proposed different types of interpreters for measuring the degree of pathogenicity of variants. However, in predicting the disease type and disease-gene associations, scholars face two essential challenges, namely the vast number of existing variants and the existence of variants which are recognized as variant of uncertain significance (VUS). To tackle these challenges, we propose algorithms to assign a significance to each gene rather than each variant, describing its degree of pathogenicity. Since the interpreters identified most of the variants as VUS, most of the gene scores were identified as uncertain significance. To predict the uncertain significance scores, we design two matrix factorization-based models: the common latent space model uses genomics variant data as well as heterogeneous clinical data, while the single-matrix factorization model can be used when heterogeneous clinical data are unavailable. We have managed to show that the models successfully predict the uncertain significance scores with low error and high accuracy. Moreover, to evaluate the effectiveness of our novel input features, we train five different multi-label classifiers including a feedforward neural network with the same feature set and show they all achieve high accuracy as the main impact of our approach comes from the features. Availability: The source code is freely available at https://github.com/sabdollahi/CoLaSpSMFM.

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.

Insights into platinum-induced peripheral neuropathy-current perspective

Cancer is a global health problem that is often successfully addressed by therapy, with cancer survivors increasing in numbers and living longer world around. Although new cancer treatment options are continuously explored, platinum based chemotherapy agents remain in use due to their efficiency and availability. Unfortunately, all cancer therapies affect normal tissues as well as cancer, and more than 40 specific side effects of platinum based drugs documented so far decrease the quality of life of cancer survivors. Chemotherapy-induced peripheral neuropathy is a frequent side effects of platinum-based chemotherapy agents. This cluster of complications is often so debilitating that patients occasionally have to discontinue the therapy. Sensory neurons of dorsal root ganglia are at the core of chemotherapy-induced peripheral neuropathy symptoms. In these postmitotic cells, DNA damage caused by platinum chemotherapy interferes with normal functioning. Accumulation of DNA-platinum adducts correlates with neurotoxic severity and development of sensation of pain. While biochemistry of DNA-platinum adducts is the same in all cell types, molecular mechanisms affected by DNA-platinum adducts are different in cancer cells and non-dividing cells. This review aims to raise awareness about platinum associated chemotherapy-induced peripheral neuropathy as a medical problem that has remained unexplained for decades. We emphasize the complexity of this condition both from clinical and mechanistical point of view and focus on recent findings about chemotherapy-induced peripheral neuropathy in in vitro and in vivo model systems. Finally, we summarize current perspectives about clinical approaches for chemotherapy-induced peripheral neuropathy treatment.

RgIA4 Accelerates Recovery from Paclitaxel-Induced Neuropathic Pain in Rats

Chemotherapeutic drugs are widely utilized in the treatment of human cancers. Painful chemotherapy-induced neuropathy is a common, debilitating, and dose-limiting side effect for which there is currently no effective treatment. Previous studies have demonstrated the potential utility of peptides from the marine snail from the genus Conus for the treatment of neuropathic pain. α-Conotoxin RgIA and a potent analog, RgIA4, have previously been shown to prevent the development of neuropathy resulting from the administration of oxaliplatin, a platinum-based antineoplastic drug. Here, we have examined its efficacy against paclitaxel, a chemotherapeutic drug that works by a mechanism of action distinct from that of oxaliplatin. Paclitaxel was administered at 2 mg/kg (intraperitoneally (IP)) every other day for a total of 8 mg/kg. Sprague Dawley rats that were co-administered RgIA4 at 80 µg/kg (subcutaneously (SC)) once daily, five times per week, for three weeks showed significant recovery from mechanical allodynia by day 31. Notably, the therapeutic effects reached significance 12 days after the last administration of RgIA4, which is suggestive of a rescue mechanism. These findings support the effects of RgIA4 in multiple chemotherapeutic models and the investigation of α9α10 nicotinic acetylcholine receptors (nAChRs) as a non-opioid target in the treatment of chronic pain.

Mechanisms of Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most frequent side effects caused by antineoplastic agents, with a prevalence from 19% to over 85%. Clinically, CIPN is a mostly sensory neuropathy that may be accompanied by motor and autonomic changes of varying intensity and duration. Due to its high prevalence among cancer patients, CIPN constitutes a major problem for both cancer patients and survivors as well as for their health care providers, especially because, at the moment, there is no single effective method of preventing CIPN; moreover, the possibilities of treating this syndrome are very limited. There are six main substance groups that cause damage to peripheral sensory, motor and autonomic neurons, which result in the development of CIPN: platinum-based antineoplastic agents, vinca alkaloids, epothilones (ixabepilone), taxanes, proteasome inhibitors (bortezomib) and immunomodulatory drugs (thalidomide). Among them, the most neurotoxic are platinum-based agents, taxanes, ixabepilone and thalidomide; other less neurotoxic but also commonly used drugs are bortezomib and vinca alkaloids. This paper reviews the clinical picture of CIPN and the neurotoxicity mechanisms of the most common antineoplastic agents. A better understanding of the risk factors and underlying mechanisms of CIPN is needed to develop effective preventive and therapeutic strategies.