Genetic variation of CYP3A5 influences paclitaxel/carboplatin-induced toxicity in Chinese epithelial ovarian cancer patients

Platinum-based chemotherapy: trends in organic nanodelivery systems

Despite the investment in platinum drugs research, cisplatin, carboplatin and oxaliplatin are still the only Pt-based compounds used as first line treatments for several cancers, with a few other compounds being approved for administration in some Asian countries. However, due to the severe and worldwide impact of oncological diseases, there is an urge for improved chemotherapeutic approaches. Furthermore, the pharmaceutical application of platinum complexes is hindered by their inherent toxicity and acquired resistance. Nanodelivery systems rose as a key strategy to overcome these challenges, with recognized versatility and ability towards improving the safety, bioavailability and efficacy of the available drugs. Among the known nanocarriers, organic systems have been widely applied, taking advantage of their potential as drug vehicles. Researchers have mainly focused on the development of lipidic and polymeric carriers, including supramolecular structures, with an overall improvement of encapsulated platinum complexes. Herein, an overview of recent trends and strategies is presented, with the main focus on the encapsulation of platinum compounds into organic nanocarriers, showcasing the evolution in the design and development of these promising systems. This comprehensive review highlights formulation methods as well as characterization procedures, providing insights that may be helpful for the development of novel platinum nanocarriers aiming at future pharmaceutical applications.

Targeting Cytochrome P450 Enzymes in Ovarian Cancers: New Approaches to Tumor-Selective Intervention

Over the past decade, there have been significant developments in treatment for ovarian cancer, yet the lack of targeted therapy with few side effects still represents a major issue. The cytochrome P450 (CYP) enzyme family plays a vital role in the tumorigenesis process and metabolism of drugs and has a negative impact on therapy outcomes. Gaining more insight into CYP expression is crucial to understanding the pathophysiology of ovarian cancer since many isoforms are essential to the metabolism of xenobiotics and steroid hormones, which drive the disease's development. To the best of our knowledge, no review articles have documented the intratumoral expression of CYPs and their implications in ovarian cancer. Therefore, the purpose of this review is to provide a clear understanding of differential CYP expression in ovarian cancer and its implications for the prognosis of ovarian cancer patients, together with the effects of CYP polymorphisms on chemotherapy metabolism. Finally, we discuss opportunities to exploit metabolic CYP expression for the development of novel therapeutic methods to treat ovarian cancer.

CYP3A genetic variation and taxane-induced peripheral neuropathy: a systematic review, meta-analysis, and candidate gene study

Background: Taxane-induced peripheral neuropathy (TIPN) is an important cause of premature treatment cessation and dose-limitation in cancer therapy. It also reduces quality of life and survivorship in affected patients. Genetic polymorphisms in the CYP3A family have been investigated but the findings have been inconsistent and contradictory. Methods: A systematic review identified 12 pharmacogenetic studies investigating genetic variation in CYP3A4*22 and CYP3A5*3 and TIPN. In our candidate gene study, 288 eligible participants (211 taxane participants receiving docetaxel or paclitaxel, and 77 control participants receiving oxaliplatin) were successfully genotyped for CYP3A4*22 and CYP3A5*3. Genotyping data was transformed into a combined CYP3A metaboliser phenotype: Poor metabolisers, intermediate metabolisers and extensive metabolisers. Individual genotypes and combined CYP3A metaboliser phenotypes were assessed in relation to neurotoxicity, including by meta-analysis where possible. Results: In the systematic review, no significant association was found between CYP3A5*3 and TIPN in seven studies, with one study reporting a protective association. For CYP3A4*22, one study has reported an association with TIPN, while four other studies failed to show an association. Evaluation of our patient cohort showed that paclitaxel was found to be more neurotoxic than docetaxel (p < 0.001). Diabetes was also significantly associated with the development of TIPN. The candidate gene analysis showed no significant association between either SNP (CYP3A5*3 and CYP3A4*22) and the development of TIPN overall, or severe TIPN. Meta-analysis showed no association between these two variants and TIPN. Transformed into combined CYP3A metaboliser phenotypes, 30 taxane recipients were poor metabolisers, 159 were intermediate metabolisers, and 22 were extensive metabolisers. No significant association was observed between metaboliser status and case-control status. Summary: We have shown that the risk of peripheral neuropathy during taxane chemotherapy is greater in patients who have diabetes. CYP3A genotype or phenotype was not identified as a risk factor in either the candidate gene analysis or the systematic review/meta-analysis, although we cannot exclude the possibility of a minor contribution, which would require a larger sample size.

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.

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.

Pharmacogenomics of anticancer drugs: Personalising the choice and dose to manage drug response

The field of pharmacogenomics has made great strides in oncology over the last 20 years and indeed a significant number of pre-emptive genetic tests are now routinely undertaken prior to anticancer drug administration. Many of these gene-drug interactions are the fruits of candidate gene and genome-wide association studies, which have largely focused on common genetic variants (allele frequency>1%). Examples where there is clinical utility include genotyping or phenotyping for G6PD to prevent rasburicase-induced RBC haemolysis, and TPMT to prevent thiopurine-induced bone marrow suppression. Other associations such as CYP2D6 status in determining the efficacy of tamoxifen are more controversial because of contradictory evidence from different sources, which has led to variability in the implementation of testing. As genomic technology becomes ever cheaper and more accessible, we must look to the additional data our genome can provide to explain interindividual variability in anticancer drug response. Clearly genes do not act on their own and it is therefore important to investigate genetic factors in conjunction with clinical factors, interacting concomitant drug therapies and other factors such as the microbiome, which can all affect drug disposition. Taking account of all of these factors, in conjunction with the somatic genome, is more likely to provide better predictive accuracy in determining anticancer drug response, both efficacy and safety. This review summarises the existing knowledge related to the pharmacogenomics of anticancer drugs and discusses areas of opportunity for further advances in personalisation of therapy in order to improve both drug safety and efficacy.

ABCB1 and ERCC1 gene polymorphisms are associated with nephro- and hepatotoxicity to carboplatin/paclitaxel-based chemotherapy in patients with gynecologic cancers

BACKGROUND

Paclitaxel/carboplatin combination is the standard chemotherapeutic protocol for gynecologic cancers, but severe toxicities may compromise treatment. There is great inter-individual variability regarding the incidence and severity of toxicities, which may be due to single-nucleotide polymorphisms (SNPs) affecting drug disposition or cellular sensitivity. Here we investigate the impact of selected SNPs in ERCC1, ABCB1, CYP2C8, and CYP3A5 genes on the incidence of severe toxicities, including nephro- and hepatotoxicity.

METHODS

A cohort of 507 gynecological cancer patients receiving paclitaxel/carboplatin was recruited at the Brazilian National Cancer Institute (INCA-Brazil). Clinical data were obtained during routine consultations or from electronic medical records. Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE 5.0). Genotyping was performed using real-time PCR.

RESULTS

ABCB1 c.1236C>T was associated with moderate-to-severe (grades 2-4) nephrotoxicity (OR_adjusted 2.40; 95% CI 1.39-4.15), even after adjustment for age (≥ 65) and diabetes. The risk association between ABCB1 c.1236C>T and moderate-to-severe nephrotoxicity following paclitaxel/carboplatin chemotherapy was also present among non-diabetic patients (OR_adjusted 2.16; 95% CI 1.22-3.82). ERCC1 c.118C>T was the only individual variable associated with an increased risk for moderate-to-severe (grades 2-4) hepatotoxicity (OR 3.71; 95% CI 1.08-12.77), severe nausea (OR 4.18; 95% CI 1.59-10.95), and severe myalgia (OR 1.95; 95% CI 1.12-3.40).

CONCLUSIONS

ABCB1 c.1236C>T and ERCC1 c.118C>T might serve as potential biomarkers for the risk of moderate-to-severe toxicities to carboplatin/paclitaxel chemotherapy of gynecological cancers.

Expression and Function of Eicosanoid-Producing Cytochrome P450 Enzymes in Solid Tumors

Oxylipins derived from the oxidation of polyunsaturated fatty acids (PUFAs) act as important paracrine and autocrine signaling molecules. A subclass of oxylipins, the eicosanoids, have a broad range of physiological outcomes in inflammation, the immune response, cardiovascular homeostasis, and cell growth regulation. Consequently, eicosanoids are implicated in the pathophysiology of various diseases, most notably cancer, where eicosanoid mediated signaling is involved in tumor development, progression, and angiogenesis. Cytochrome P450s (CYPs) are a superfamily of heme monooxygenases generally involved in the clearance of xenobiotics while a subset of isozymes oxidize PUFAs to eicosanoids. Several eicosanoid forming CYPs are overexpressed in tumors, elevating eicosanoid levels and suggesting a key function in tumorigenesis and progression of tumors in the lung, breast, prostate, and kidney. This review summarizes the current understanding of CYPs' involvement in solid tumor etiology and progression providing supporting public data for gene expression from The Cancer Genome Atlas.

Genetic associations of docetaxel-based chemotherapy-induced myelosuppression in Chinese Han population

WHAT IS KNOWN AND OBJECTIVE

Myelosuppression, an adverse drug reaction (ADR), often causes medical treatment termination in cancer patients. It has been known that genetic components, such as single-nucleotide polymorphisms (SNPs), influence the risk of myelosuppression at the individual-patient level. However, due to ethnic variation in frequency of genetic polymorphisms, results reported in Caucasian patients may not be generalizable to the Chinese Han population. Until now, few researches on myelosuppression included Chinese Han patients. In this study, we conducted a systematic study of potential biomarkers for docetaxel-induced myelosuppression in Han Chinese patients.

METHODS

We examined 61 SNPs in 36 genes that code for drug transporters, metabolism enzymes, nuclear receptors and DNA repair pathway in 110 Chinese Han patients receiving docetaxel-based chemotherapy. Genotyping was conducted using the Sequenom MassARRAY system. Significant SNPs were identified by logistic regression, and gene-gene interactions were investigated by generalized multifactor dimensionality reduction (GMDR) analysis.

RESULTS AND DISCUSSION

Our results revealed that 11 SNPs in nine genes (SLC15A1, SLCO1A2, CYP2D6, FMO3, UGT1A1, NAT2, SULT2A1, PXR and HNF4α) were associated with docetaxel-induced myelosuppression. GMDR analyses suggested that a 3-locus model: SLC15A1 rs2297322-PXR rs3732359-FMO3 rs2266782 was an appropriate predictive model of docetaxel-induced myelosuppression (P = .017, Testing Bal.Acc = 0.653, CV Consistency = 10/10).

WHAT IS NEW AND CONCLUSION

Our findings suggest multiple novel predictive biomarkers of docetaxel-induced myelosuppression: SLC15A1 rs2297322, PXR rs3732359 and FMO3 rs2266782. These discoveries should help in advancing future personalized therapy of docetaxel-based chemotherapy specific to Chinese Han patients.

Impact of gene polymorphisms on the systemic toxicity to paclitaxel/carboplatin chemotherapy for treatment of gynecologic cancers

PURPOSE

Gynecologic malignancies are often detected in advanced stages, requiring chemotherapy with taxane/platinum combinations, which may cause severe toxicities, such as neutropenia and peripheral neuropathy. Gene polymorphisms are suspected as possible causes for the interindividual variability on chemotherapy toxicities.

OBJECTIVE

To evaluate the role of ABCB1 1236C>T, 3435C>T; CYP2C8*3; CYP3A5*3C variants on paclitaxel/carboplatin toxicities.

METHODS

A cohort of 503 gynecologic cancer patients treated with paclitaxel/carboplatin at the Brazilian National Cancer Institute (INCA-Brazil) was recruited (2013-2017). Polymorphisms were genotyped by real-time PCR, and toxicities were evaluated by patients' interviews at each chemotherapy cycle and by data collection from electronic records. The association of clinical features and genotypes with severe toxicities was estimated using Pearson's Chi square tests and multiple regression analyses, with calculation of adjusted odds ratios (OR_adjusted), and respective 95% confidence intervals (95% CI).

RESULTS

CYP2C8*3 was significantly associated with increased risks of severe (grades 3-4) neutropenia (OR_adjusted 2.11; 95% CI 1.24-3.6; dominant model) and severe thrombocytopenia (OR_adjusted 4.93; 95% CI 1.69-14.35; recessive model), whereas ABCB1 variant genotypes (OR_adjusted 2.13; 95% CI 1.32-3.42), in association with CYP2C8*3 wild type (GG) (OR_adjusted 1.93; 95% CI 1.17-3.19), were predictive of severe fatigue.

CONCLUSIONS

The present study suggests that CYP2C8*3 is a potential predictor of hematological toxicities related to paclitaxel/carboplatin treatment. Since hematological toxicities, especially neutropenia, may lead to dose delay or treatment interruption, such prognostic evaluation may contribute to clinical management of selected patients with paclitaxel-based chemotherapy.

Tenacigenin B ester derivatives from Marsdenia tenacissima actively inhibited CYP3A4 and enhanced in vivo antitumor activity of paclitaxel

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima (Roxb.) Wight et Arn is a vine distributed in southwest area of China and used in folk medicine for treatment of tumors. Recent decades of studies on this plant reveal its synergistic effects with certain anticancer drugs in cancer therapy. In our previous study, an extract ETA which contains total aglycones made from M. tenacissima significantly enhanced antitumor activity of paclitaxel in tumor-bearing mice. However, the effective constituents in ETA and the underlying mechanisms remain unclear.

AIM OF THE STUDY

Reveal the active components in ETA as well as the molecular mechanism in enhancing antitumor efficacy of paclitaxel.

MATERIAL AND METHODS

Main constituents in ETA were purified by chemical methods. Effects of the purified constituents on metabolic activity of CYP450 enzymes were evaluated in human liver microsomes. Ability of the constituents to enhance antitumor activity of paclitaxel were investigated in nude mice bearing HeLa tumors. Pharmacokinetic study was performed in SD rats. Molecular docking was carried out for investigation of drug-protein interactions.

RESULTS

Three main C₂₁ steroidal aglycones, 11α-O-tigloyl-12β-O-acetyl-tenacigenin B (MT1), 11α-O-2-methylbutanoyl-12β-O-tigloyl-tenacigenin B (MT2) and 11α-O-2-methylbutanoyl-12β-O-acetyl-tenacigenin B (MT3), together with tenacigenin B (MT4) was prepared from ETA. Among them, MT1, MT2 and MT3 strongly inhibit the metabolic activity of CYP3A4. MT2 also showed inhibitory effects on CYP2C8, CYP2B6 and CYP2C19. In HeLa tumor xenografts, MT1, MT2 and MT3 (30 mg/kg) did not affect tumor growth themselves, but significantly enhanced paclitaxel-induced growth inhibition. In addition, coadministration of MT2 with paclitaxel resulted in significant reduction of liver CYP2C8. In pharmacokinetic study, MT2 significantly increased the blood concentration of paclitaxel with increased AUC value by 2.2-5.3 folds. Molecular docking analysis suggested hydrophobic interaction modes of tenacigenin B derivatives with CYP3A4, and also the essential roles of the C-11 and C-12 ester groups for effective interaction with CYP3A4.

CONCLUSION

Our study proves that, 11α-O-tigloyl-12β-O-acetyl-tenacigenin B, 11α-O-2-methylbutanoyl-12β-O-tigloyl-tenacigenin B and 11α-O-2-methylbutanoyl-12β-O-acetyl-tenacigenin B, which are the main constituents of ETA, are active inhibitors of CYP3A4 with potential to increase therapeutic efficacy of anticancer drugs that are substrates of CYP3A4. Tenacigenin B derivatives with C-11 and C-12 ester group substitutions, or at least a large part of them, are active components in ETA and M. tenacissima to enhance in vivo antitumor efficacies of paclitaxel.

GSTP1 rs1695 is associated with both hematological toxicity and prognosis of ovarian cancer treated with paclitaxel plus carboplatin combination chemotherapy: a comprehensive analysis using targeted resequencing of 100 pharmacogenes

Purpose

To find genetic variants that predicted toxicity and/or efficacy of paclitaxel plus carboplatin combination therapy (TC therapy).

Patients and methods

In a retrospective case-control study, we analyzed 320 patients who had received TC therapy for gynecological cancers (ovarian, fallopian tube, peritoneal, uterine, and cervical cancers) and collected their germline DNA. We performed a comprehensive pharmacogenomic analysis using a targeted resequencing panel of 100 pharmacogenes. For 1,013 variants passing QC, case-control association studies and survival analyses were conducted.

Results

GSTP1 rs1695 showed the smallest p value for hematotoxicity association, and the ¹⁰⁵Ile wild type allele had a significantly higher risk of severe hematotoxicity (neutropenia G4, thrombocytopenia ≥ G3 and anemia ≥ G3) than the ¹⁰⁵Val allele (p=0.00034, odds ratio=5.71 (95% confidence interval:1.77-18.44)). Next, we assessed 5-year progression-free survival (PFS) and overall survival (OS) in 56 advanced ovarian cancer patients who received tri-weekly TC as a first-line chemotherapy. Patients with the ¹⁰⁵Ile/¹⁰⁵Ile genotype showed significantly better PFS (p=0.00070) and OS (p=0.0012) than those with the ¹⁰⁵Ile/¹⁰⁵Val or ¹⁰⁵Val/¹⁰⁵Val genotype.

Conclusion

Our study indicates that the GSTP1 rs1695 ¹⁰⁵Ile/¹⁰⁵Ile genotype is associated with both severe hematotoxicity and high efficacy of TC therapy, identifying a possible prognostic indicator for patients with TC therapy.

The role of the globular heads of the C1q receptor in paclitaxel-induced human ovarian cancer cells apoptosis by a mitochondria-dependent pathway

As a mitochondrial membrane protein, globular C1q receptor (gC1qR) can mediate a variety of biological responses. Our study aims to investigate the role of gC1qR in paclitaxel-induced apoptosis of human ovarian cancer cells and to elucidate its potential molecular mechanism. The level of gC1qR was examined using real-time PCR and western blot analyses. Human ovarian cancer cells viability, migration, and proliferation were detected using the water-soluble tetrazolium salt (WST-1) assay, the transwell assay, and H-thymidine incorporation into DNA (H-TdR) assay, respectively. Apoptosis in cells was assessed using flow cytometric analysis. The intracellular reactive oxygen species was estimated by the fluorescence of H2DCFDA and the mitochondrial membrane potential was tested using a JC-1 probe. The expression of the gC1qR gene decreased significantly in human ovarian cancer tissues relative to the surrounding non-neoplastic ovarian tissues. Cells treated with paclitaxel showed increased gC1qR gene expression, cell apoptosis, and mitochondria dysfunction, and the effects on these cells could be abrogated by the addition of gC1qR small-interfering RNA or α-lipoic acid that was used to protect the mitochondria function. In summary, these data support a mechanism that gC1qR-induced mitochondria dysfunction was involved in the paclitaxel-mediated apoptosis of ovarian cancer cells.

Modification of single-nucleotide polymorphism in a fully humanized CYP3A mouse by genome editing technology

Cytochrome P450, family 3, subfamily A (CYP3A) enzymes metabolize approximately 50% of commercially available drugs. Recently, we developed fully humanized transchromosomic (Tc) CYP3A mice with the CYP3A cluster including CYP3A4, CYP3A5, CYP3A7, and CYP3A43. Our humanized CYP3A mice have the CYP3A5*3 (g.6986G) allele, resulting in the almost absence of CYP3A5 protein expression in the liver and intestine. To produce model mice for predicting CYP3A5′s contribution to pharmacokinetics, we performed a single-nucleotide polymorphism (SNP) modification of CYP3A5 (g.6986G to A, *3 to *1) on the CYP3A cluster using genome editing in  both mouse ES cells and fertilized eggs, and produced humanized CYP3A5*1 mice recapitulating the CYP3A5*1 carrier phenotype in humans. The humanized CYP3A mouse with CYP3A5*1 is the first Tc mouse for predicting the SNP effect on pharmacokinetics in humans. The combination of Tc technology and genome editing enables the production of useful humanized models that reflect humans with different SNPs.

The molecular genetics of chemotherapy-induced peripheral neuropathy: A systematic review and meta-analysis

Chemotherapy-induced peripheral neuropathy (CIPN) can adversely affect completion of systemic anti-cancer treatment and cause long-term morbidity. Increasingly pharmacogenetic studies have been performed to explore susceptibility to this important adverse effect. A systematic review was conducted to identify pharmacogenetic studies, assess their quality and findings and undertake meta-analysis where possible. 93 studies were included. Notable methodological issues included lack of standardisation and detail in phenotype definition and acknowledgement of potential confounding factors. Insufficient data was presented in many studies meaning only a minority could be included in meta-analysis showing mainly non-significant effects. Nonetheless, SNPs in CYP2C8, CYP3A4, ARHGEF10, EPHA and TUBB2A genes (taxanes), FARS2, ACYP2 and TAC1 (oxaliplatin), and CEP75 and CYP3A5 (vincristine) are of potential interest. These require exploration in large cohort studies with robust methodology and well-defined phenotypes. Seeking standardisation of phenotype, collaboration and subsequently, individual-patient-data meta-analysis may facilitate identifying contributory SNPs which could be combined in a polygenic risk score to predict those most at risk of CIPN.