Pharmacoepidemiology: A time for a new multidisciplinary approach to precision medicine.

The advent of the genomic age has created a rapid increase in complexity for the development and selection of drug treatments. A key component of precision medicine is the use of genetic information to improve therapeutic effectiveness of drugs and prevent potential adverse drug reactions. Pharmacoepidemiology, as a field, uses observational methods to evaluate the safety and effectiveness of drug treatments in populations. Pharmacoepidemiology by virtue of its focus, tradition, and research orientation can provide appropriate study designs and analysis methods for precision medicine. The objective of this manuscript is to demonstrate how pharmacoepidemiology can impact and shape precision medicine and serve as a reference for pharmacoepidemiologists interested in contributing to the science of precision medicine. This paper depicts the state of the science with respect to the need for pharmacoepidemiology and pharmacoepidemiological methods, tools and approaches for precision medicine; the need for and how pharmacoepidemiologists use their skills to engage with the precision medicine community; and recommendations for moving the science of precision medicine pharmacoepidemiology forward. We propose a new integrated multidisciplinary approach dedicated to the emerging science of precision medicine pharmacoepidemiology.

Clinical decisions surrounding genomic and proteomic testing among United States veterans treated for lung cancer within the Veterans Health Administration.

BACKGROUND: Current clinical guidelines recommend epidermal growth factor receptor (EGFR) mutational testing in patients with metastatic non-small cell lung cancer (NSCLC) to predict the benefit of the tyrosine kinase inhibitor erlotinib as first-line treatment. Proteomic (VeriStrat) testing is recommended for patients with EGFR negative or unknown status when erlotinib is being considered. Departure from this clinical algorithm can increase costs and may result in worse outcomes. We examined EGFR and proteomic testing among patients with NSCLC within the Department of Veterans Affairs (VA). We explored adherence to guidelines and the impact of test results on treatment decisions and cost of care. METHODS: Proteomic and EGFR test results from 2013 to 2015 were merged with VA electronic health records and pharmacy data. Chart reviews were conducted. Cases were categorized based on the appropriateness of testing and treatment. RESULTS: Of the 69 patients with NSCLC who underwent proteomic testing, 33 (48%) were EGFR-negative and 36 (52%) did not have documented EGFR status. We analyzed 138 clinical decisions surrounding EGFR/proteomic testing and erlotinib treatment. Most decisions (105, or 76%) were concordant with clinical practice guidelines. However, for 24 (17%) decisions documentation of testing or justification of treatment was inadequate, and 9 (7%) decisions represented clear departures from guidelines. CONCLUSION: EGFR testing, the least expensive clinical intervention analyzed in this study, was significantly underutilized or undocumented. The records of more than half of the patients lacked information on EGFR status. Our analysis illustrated several clinical scenarios where the timing of proteomic testing and erlotinib diverged from the recommended algorithm, resulting in excessive costs of care with no documented improvements in health outcomes.

Dosing recommendations for pharmacogenetic interactions related to drug metabolism.

OBJECTIVE: Pharmacogenomic studies have established the important contribution of drug-metabolizing enzyme genotype toward drug toxicity and treatment failure; however, clinical implementation of pharmacogenomics has been slow. The aim of this study was to systematically review the information on drug-metabolizing enzyme pharmacogenomics available in the US drug labeling, practice guidelines, and recommendations. METHODS: Drug-metabolizing enzyme genotype and phenotype information was assessed in US FDA drug labeling, clinical practice guidelines, and independent technology assessors to evaluate the consistency in information sources for healthcare providers. RESULTS: Eighty four gene-drug pairs were identified as having drug-metabolizing enzyme genotype or phenotype information within the label. The manner in which pharmacogenomic information was presented was heterogeneous both within the label and between clinical practice recommendations. CONCLUSION: For proper implementation of pharmacogenomics in clinical practice, information sources for healthcare providers should relay consistent and clear information for the appropriate use of biomarkers.

An overview of recommendations and translational milestones for genomic tests in cancer.

PURPOSE: To understand the translational trajectory of genomic tests in cancer screening, diagnosis, prognosis, and treatment, we reviewed tests that have been assessed by recommendation and guideline developers. METHODS: For each test, we marked translational milestones by determining when the genomic association with cancer was first discovered and studied in patients, and when a health application for a specified clinical use was successfully demonstrated and approved or cleared by the US Food and Drug Administration. To identify recommendations and guidelines, we reviewed the websites of cancer, genomic, and general guideline developers and professional organizations. We searched the in vitro diagnostics database of the US Food and Drug Administration for information, and we searched PubMed for translational milestones. Milestones were examined against type of recommendation, Food and Drug Administration approval or clearance, disease rarity, and test purpose. RESULTS: Of the 45 tests we identified, 9 received strong recommendations for their usage in clinical settings, 14 received positive but moderate recommendations, and 22 were not currently recommended. For 18 tests, two or more different sources had issued recommendations, with 67% concordance. Only five tests had Food and Drug Administration approval, and an additional five had clearance. The median time from discovery to recommendation statement was 14.7 years. CONCLUSION: In general, there were no associations found between translational trajectory and recommendation category.Genet Med 17 6, 431-440.

Palliative Intent Treatment and Palliative Care Delivery for Individuals With Advanced Nonsmall Cell Lung Cancer and Melanoma: A Patterns of Care Study.

Introduction: This study aimed to describe the patterns of palliative intent treatment and/or palliative care (PC) delivery among a population-based sample of individuals diagnosed with advanced nonsmall cell lung cancer (NSCLC) or advanced melanoma. Methods: Data from 655 advanced-stage melanoma patients and 2688 advanced-stage NSCLC patients included in the National Cancer Institute's 2017/2018 Patterns of Care study were analyzed. Bivariate and multivariate logistic regression analyses examined factors associated with (1) receipt of PC (including palliative surgery, radiation, and/or systemic therapy after cancer diagnosis, and PC consultations); and (2) timing from diagnosis to receipt of PC. Proportional hazards models also examined factors associated with timing of receipt of PC after diagnosis. Results: A total of 23.5% of those with melanoma and 52.6% of those with NSCLC received some type of PC. For melanoma, stage 4 (vs. stage 3) was associated with higher receipt of PC and receipt within three months of diagnosis. For NSCLC, stage 4 (vs. stage 3) and a diagnosis of depression or psychosocial distress within three months of diagnosis were significantly associated with receipt of PC and receipt within three months of diagnosis. Conclusion: Study findings indicate that those with advanced-stage cancer or who report distress are more likely to receive palliative intent treatment and/or PC. Given that individuals with advanced cancers are living longer and often experience long-lasting symptoms, it is critical to identify and overcome barriers for broadly delivering comprehensive palliative and supportive care.

Overview of Research on Germline Genetic Variation in Immune Genes and Cancer Outcomes.

Since the late 19th century, the immune system has been known to play a role in cancer risk, initiation, and progression. Genome-wide association studies (GWAS) have identified hundreds of genetic risk loci for autoimmune and inflammatory diseases, yet the connection between human genetic variation and immune-mediated response to cancer treatments remains less well-explored. Understanding inherited genetic variation, with respect to germline genetic polymorphisms that affect immune system pathways, could lead to greater insights about how these processes may best be harnessed to successfully treat cancer. Our goal in this manuscript was to understand progress and challenges in assessing the role of inherited genetic variation in response to cancer treatments. Overall, the 39 studies reviewed here suggest that germline genetic variation in immune system-related genes may potentially affect responses to cancer treatments. Although further research is needed, considering information on germline immune genetic variation may help, in some cases, to optimize cancer treatment.

Survivorship for Individuals Living With Advanced and Metastatic Cancers: National Cancer Institute Meeting Report.

An important and often overlooked subpopulation of cancer survivors is individuals who are diagnosed with or progress to advanced or metastatic cancer. Living longer with advanced or metastatic cancer often comes with a cost of burdensome physical and psychosocial symptoms and complex care needs; however, research is limited on this population. Thus, in May 2021, the National Cancer Institute convened subject matter experts, researchers, clinicians, survivors, and advocates for a 2-day virtual meeting. The purpose of this report is to provide a summary of the evidence gaps identified by subject matter experts and attendees and key opportunities identified by the National Cancer Institute in 5 research areas: epidemiology and surveillance, symptom management, psychosocial research, health-care delivery, and health behaviors. Identified gaps and opportunities include the need to develop new strategies to estimate the number of individuals living with advanced and metastatic cancers; understand and address emerging symptom trajectories; improve prognostic understanding and communication between providers, patients, and caregivers; develop and test models of comprehensive survivorship care tailored to these populations; and assess patient and provider preferences for health behavior discussions throughout the survivorship trajectory. To best address the needs of individuals living with advanced and metastatic cancer and to deliver comprehensive evidence-based quality care, research is urgently needed to fill evidence gaps, and it is essential to incorporate the survivor perspective. Developing such an evidence base is critical to inform policy and practice.

Epidemiologic Research of Rare Cancers: Trends, Resources, and Challenges.

BACKGROUND: The goals of this project were to assess the status of NCI's rare cancer-focused population science research managed by the Division of Cancer Control and Population Sciences (DCCPS), to develop a framework for evaluation of rare cancer research activities, and to review available resources to study rare cancers. METHODS: Cancer types with an overall age-adjusted incidence rate of less than 20 cases per 100,000 individuals were identified using NCI Surveillance, Epidemiology and End Results (SEER) Program data. SEER data were utilized to develop a framework based on statistical commonalities. A portfolio analysis of DCCPS-supported active grants and a review of three genomic databases were conducted. RESULTS: For the 45 rare cancer types included in the analysis, 123 active DCCPS-supported rare cancer-focused grants were identified, of which the highest percentage (18.7%) focused on ovarian cancer. The developed framework revealed five clusters of rare cancer types. The cluster with the highest number of grants (n = 43) and grants per cancer type (10.8) was the cluster that included cancer types of higher incidence, average to better survival, and high prevalence (in comparison with other rare cancers). Resource review revealed rare cancers are represented in available genomic resources, but to a lesser extent compared with more common cancers. CONCLUSIONS: This article provides an overview of the rare cancer-focused population sciences research landscape as well as information on gaps and opportunities. IMPACT: The findings of this article can be used to develop efficient and comprehensive strategies to accelerate rare cancer research.See related commentary by James V. Lacey Jr, p. 1300.

Population-based utilization and costs associated with tyrosine kinase inhibitors for first-line treatment of chronic myelogenous leukemia among elderly patients.

BACKGROUND: Following approval of imatinib, a breakthrough tyrosine kinase inhibitor (TKI), survival significantly improved by more than 20% since 2001 among treated chronic myelogenous leukemia (CML) patients. Subsequently, more expensive second-generation TKIs with varying selectivity profiles have been approved. Population-based studies are needed to evaluate the real-world utilization of TKI therapies, particularly given their escalating costs and recommendations for maintenance therapy. OBJECTIVE: To assess the utilization patterns of first-line TKIs, overall and by specific agent, among elderly CML patients in the United States, and the cost implications. METHODS: CML patients aged 65 years and older at diagnosis between 2007 and 2015 were identified from population-based cancer registries in the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database. The percentage of CML patients receiving imatinib, dasatinib, or nilotinib within the first year of diagnosis was calculated along with time to first-line treatment initiation. Bivariate comparisons and Cox proportional hazards models were used to identify factors associated with TKI initiation. Average monthly patient responsibility, including patient out-of-pocket (OOP) costs, stratified by Part D low-income subsidy (LIS) status were also calculated. RESULTS: Among the 1,589 CML patients included, receipt of any TKI within 1 year of diagnosis increased from 66.2% to 78.9%. In 2015, the distribution of first-line TKI therapies was 41.3% imatinib, 28.3% dasatinib, and 9.3% nilotinib. Almost 60% of patients initiated TKI treatment within 3 months of diagnosis. Multivariable analysis indicated that TKI use in the first year was lower among the very elderly (aged > 75 years vs. 65-69 years: HR = 0.72; 95% CI = 0.63-0.83), patients with more comorbidities (Hierarchical Condition Category risk score > 2 vs. HR = 0.74, 95% CI = 0.62-0.88), and patients ineligible for LIS (HR = 0.75; 95% CI = 0.65-0.87). Average monthly patient OOP cost was significantly lower for LIS-eligible versus LIS-ineligible patients: imatinib (2016: $12 vs. $487), dasatinib (2016: $34 vs. $557), and nilotinib (2016: $1 vs. $526). CONCLUSIONS: TKI use has increased significantly since 2007. While imatinib remained the most frequently prescribed first-line agent, by 2015 newer TKIs represented one third of the market share. Utilization patterns indicated persistent age, comorbidity, and financial barriers. TKI use is indicated for long-term therapy, and increased adoption of newer, more expensive agents raises concerns about the sustained affordability of CML treatment, particularly among unsubsidized patients. DISCLOSURES: No outside funding supported this study. There are no reported conflicts of interest.

Interaction of Cisplatin with the human organic cation transporter 2.

PURPOSE: Cisplatin is predominantly eliminated in the urine through active secretion. As the solute carrier organic cation transporter 2 (OCT2) is highly expressed in the basolateral membrane of proximal tubules, we determined its contribution to cisplatin transport and assessed the relation of variation in the gene encoding OCT2 (SLC22A2) with the disposition of cisplatin. EXPERIMENTAL DESIGN: Cell lines were transfected using the Flp-In 293 system with the full-length OCT2 cDNA, and platinum concentrations were measured using flameless atomic absorption spectrometry. Pharmacokinetic data were available from 106 cancer patients, and DNA was screened for eight nonsynonymous SLC22A2 variants using direct sequencing. RESULTS: mRNA expression was 36-fold higher and uptake of the model substrate tetraethylammonium was significantly increased (P < 0.0001) in OCT2-transfected cells compared with empty vector-transfected controls. OCT2-mediated transport of cisplatin was saturable, and uptake was increased by approximately 4-fold (P < 0.0001) relative to control cells. Cisplatin inhibited OCT2-mediated transport of tetraethylammonium by up to 97%. The mean +/- SD systemic clearance of unbound cisplatin-derived platinum in the patient population was 29.2 +/- 8.39 L/h, and renal clearance was particularly variable. Only one single nucleotide polymorphism (Ala270Se; rs316019) was identified (minor allele frequency, 7.6%), and it was not found to be associated with any of the studied pharmacokinetic variables (P > 0.05). CONCLUSION: These findings support the hypothesis that OCT2 is a key renal transporter involved in cisplatin elimination. However, known variants in SLC22A2 do not substantially contribute to explaining interindividual pharmacokinetic variability, suggesting that other mechanisms, controlling OCT2 expression, might be involved.

Interaction of imatinib with human organic ion carriers.

PURPOSE: The activity of imatinib in leukemia has recently been linked with expression of the organic cation transporter 1 (OCT1) gene SLC22A1. Here, we characterized the contribution of solute carriers to imatinib transport in an effort to further understand mechanisms involved in the intracellular uptake and retention (IUR) of the drug. EXPERIMENTAL DESIGN: IUR of [3H]imatinib was studied in Xenopus laevis oocytes and HEK293 cells expressing OATP1A2, OATP1B1, OATP1B3, OCT1-3, OCTN1-2, or OAT1-3. Gene expression was determined in nine leukemia cell lines using the Affymetrix U133 array. RESULTS: Imatinib was not found to be a substrate for OCT1 in oocytes (P = 0.21), whereas in HEK293 cells IUR was increased by only 1.20-fold relative to control cells (P = 0.002). Furthermore, in 74 cancer patients, the oral clearance of imatinib was not significantly altered in individuals carrying reduced-function variants in SLC22A1 (P = 0.99). Microarray analysis indicated that SLC22A1 was interrelated with gene expression of various transporters, including ABCB1, ABCC4, ABCG2 (negative), and OATP1A2 (positive). Imatinib was confirmed to be a substrate for the three efflux transporters (P < 0.05) as well as for OATP1A2 (P = 0.0001). CONCLUSIONS: This study suggests that SLC22A1 expression is a composite surrogate for expression of various transporters relevant to imatinib IUR. This observation provides a mechanistic explanation for previous studies that have linked SLC22A1 with the antitumor activity of imatinib. Because of its high expression in the intestine, ciliary body, gliomas, and leukemia cells, OATP1A2 may play a key role in imatinib pharmacokinetics-pharmacodynamics.

Use of Next-Generation Sequencing Tests to Guide Cancer Treatment: Results From a Nationally Representative Survey of Oncologists in the United States.

Purpose: There are no nationally representative data on oncologists' use of next-generation sequencing (NGS) testing in practice. The purpose of this study was to investigate how oncologists in the United States use NGS tests to evaluate patients with cancer and to inform treatment recommendations. Methods: The study used data from the National Survey of Precision Medicine in Cancer Treatment, which was mailed to a nationally representative sample of oncologists in 2017 (N = 1,281; cooperation rate = 38%). Weighted percentages were calculated to describe NGS test use. Multivariable modeling was conducted to assess the association of test use with oncologist practice characteristics. Results: Overall, 75.6% of oncologists reported using NGS tests to guide treatment decisions. Of these oncologists, 34.0% used them often to guide treatment decisions for patients with advanced refractory disease, 29.1% to determine eligibility for clinical trials, and 17.5% to decide on off-label use of Food and Drug Administration-approved drugs. NGS test results informed treatment recommendations often for 26.8%, sometimes for 52.4%, and never or rarely for 20.8% of oncologists. Oncologists younger than 50 years of age, holding a faculty appointment, having genomics training, seeing more than 50 unique patients per month, and having access to a molecular tumor board were more likely to use NGS tests. Conclusion: In 2017, most oncologists in the United States were using NGS tests to guide treatment decisions for their patients. More research is needed to establish the clinical usefulness of these tests, to develop evidence-based clinical guidelines for their use in practice, and to ensure that patients who can benefit from these new technologies receive appropriate testing and treatment.

Updating the landscape of direct-to-consumer pharmacogenomic testing.

Pharmacogenomics has identified important drug-gene interactions that affect the safety and efficacy of medications. Direct-to-consumer genetic testing, when first introduced, included some pharmacogenomic-related genes. The current landscape of pharmacogenomic direct-to-consumer testing is reviewed. Prior published reviews of the literature were updated through February 2017 and a scan of the current availability of direct-to-consumer genomic testing by companies was conducted. Results of the review demonstrate a shift toward physician-approved ordering.

Epidermal Growth Factor Receptor Mutational Testing and Erlotinib Treatment Among Veterans Diagnosed With Lung Cancer in the United States Department of Veterans Affairs.

INTRODUCTION: We examined mutational testing of the epidermal growth factor gene (EGFR) and erlotinib treatment among veterans diagnosed with non-small-cell lung cancer in the United States Department of Veterans Affairs (VA). Our objectives were to identify the prevalence of clinically actionable EGFR mutations, to determine whether testing and treatment were guideline concordant, to evaluate the impact of testing and treatment on survival, and to estimate the rate of testing. PATIENTS AND METHODS: Test results were linked to electronic health records from VA Corporate Data Warehouse and the VA Central Cancer Registry. We analyzed patient demographic and clinical characteristics, prevalence of EGFR mutations, and timing of EGFR mutational testing and erlotinib treatment based on pharmacy records. Overall survival was assessed by Kaplan-Meier analysis. RESULTS: Among 973 patients tested at 70 VA medical centers between 2011 and 2013, 64 (7%) had sensitizing EGFR mutations, 694 (71%) were EGFR wild type, and 168 (17%) had clinically insignificant polymorphisms or variants of unknown significance. Results were not documented in 47 tests (5%). Erlotinib administration was in agreement with test results in 843 cases (87%). CONCLUSION: Veterans have a much lower rate of sensitizing EGFR mutations than the reported average of 10% to 15%, which correlates with a high rate of smoking among veterans. This may partially explain clinicians' reluctance to prescribe EGFR testing, which results in underutilization. Although test results appear to have influenced erlotinib treatment decisions, we documented a substantial number of cases where treatment was not applied in accordance with clinical guidelines, potentially resulting in worse outcomes and unnecessary cost.

BRCA testing within the Department of Veterans Affairs: concordance with clinical practice guidelines.

Guideline-concordant cancer care is a priority within the Department of Veterans Affairs (VA). In 2009, the VA expanded its capacity to treat breast cancer patients within VA medical centers (VAMCs). We sought to determine whether male and female Veterans diagnosed with breast cancer received BRCA testing as recommended by the National Comprehensive Cancer Network (NCCN) guidelines on Genetic/Familial High-Risk Assessment in Breast and Ovarian Cancer (v. 1.2010-1.2012). Using the 2011-2012 VA Central Cancer Registry and BRCA test orders from Myriad Genetics, we conducted a retrospective study. The outcome variable was a recommendation for genetic counseling or BRCA testing, determined by chart review. Independent variables expected to predict testing included region, site of care, and patient characteristics. We performed descriptive analysis of all patients and conducted multivariable logistic regression on patients who sought care at VAMCs that offered BRCA testing. Of the 462 Veterans who met NCCN testing criteria, 126 (27 %) received guideline-concordant care, either a referral for counseling or actual testing. No BRCA testing was recommended in 49 (50 %) VAMCs that provide cancer treatment. Surprisingly, patients with second primary breast cancer were less likely to be referred/tested (OR 0.39; CI 0.17, 0.89; p = 0.025). For patients under age 51, a yearly increase in age decreased likelihood of referral or testing (OR 0.85; CI 0.76, 0.94; p < 0.001). There were no differences in testing by race. In conclusion, there was significant underutilization and lack of access to BRCA testing for Veterans diagnosed with breast cancer. Our research suggests the need for clinical decision support tools to facilitate delivery of guideline-concordant cancer care and improve Veteran access to BRCA testing.

Using Immune Marker Panels to Evaluate the Role of Inflammation in Cancer: Summary of an NCI-sponsored Workshop.

Chronic inflammation is recognized to play a role in the development of several cancers. Past investigations of inflammation and cancer have typically been small, used varied assay platforms, and included a narrow range of analytes. Multiplex technologies have now been developed to measure larger numbers of inflammatory markers using small volumes of specimens. This has created an opportunity for systematic, large-scale epidemiological studies to evaluate the role of inflammation in cancer. However, lack of consensus on the approach to these studies, the technologies/assays to be used, and the most adequate analysis/interpretation of findings have thus far hindered progress. In June of 2014, the National Cancer Institute convened a workshop involving epidemiologists, immunologists, statisticians, and laboratory biologists to share their experiences with new inflammation marker technologies and findings from association studies using such methods and technologies (http://epi.grants.cancer.gov/workshops/). Consensus and gaps in our understanding of the role of chronic inflammation in cancer were identified and recommendations made to improve future efforts in this area. These recommendations are summarized herein, along with specific suggestions for how they may be implemented. By facilitating discussions among various groups, and encouraging interdisciplinary collaborations, we anticipate that the pace of research in this field will be accelerated and duplication of efforts can be minimized.

Pharmacogenomics in oncology care.

Cancer pharmacogenomics have contributed a number of important discoveries to current cancer treatment, changing the paradigm of treatment decisions. Both somatic and germline mutations are utilized to better understand the underlying biology of cancer growth and treatment response. The level of evidence required to fully translate pharmacogenomic discoveries into the clinic has relied heavily on randomized control trials. In this review, the use of observational studies, as well as, the use of adaptive trials and next generation sequencing to develop the required level of evidence for clinical implementation are discussed.

Multi-marker Solid Tumor Panels Using Next-generation Sequencing to Direct Molecularly Targeted Therapies.

In contemporary oncology practices there is an increasing emphasis on concurrent evaluation of multiple genomic alterations within the biological pathways driving tumorigenesis. At the foundation of this paradigm shift are several commercially available tumor panels using next-generation sequencing to develop a more complete molecular blueprint of the tumor. Ideally, these would be used to identify clinically actionable variants that can be matched with available molecularly targeted therapy, regardless of the tumor site or histology. Currently, there is little information available on the post-analytic processes unique to next-generation sequencing platforms used by the companies offering these tests. Additionally, evidence of clinical validity showing an association between the genetic markers curated in these tests with treatment response to approved molecularly targeted therapies is lacking across all solid-tumor types. To date, there is no published data of improved outcomes when using the commercially available tests to guide treatment decisions. The uniqueness of these tests from other genomic applications used to guide clinical treatment decisions lie in the sequencing platforms used to generate large amounts of genomic data, which have their own related issues regarding analytic and clinical validity, necessary precursors to the evaluation of clinical utility. The generation and interpretation of these data will require new evidentiary standards for establishing not only clinical utility, but also analytical and clinical validity for this emerging paradigm in oncology practice.

Cisplatin-induced downregulation of OCTN2 affects carnitine wasting.

PURPOSE: Carnitine is an essential cofactor for mitochondrial fatty acid oxidation that is actively reabsorbed by the luminal transporter Octn2 (Slc22a5). Because the nephrotoxic agent cisplatin causes urinary loss of carnitine in humans, we hypothesized that cisplatin may affect Octn2 function. EXPERIMENTAL DESIGN: Excretion of carnitine and acetylcarnitine was measured in urine collected from mice with or without cisplatin administration. The transport of carnitine was assessed in cells that were transfected with OCT1 or OCT2. The effect of cisplatin treatment on gene expression was analyzed using a mouse GeneChip array and validated using quantitative reverse transcriptase-PCR. RESULTS: In wild-type mice, urinary carnitine excretion at baseline was ∼3-fold higher than in mice lacking the basolateral cisplatin transporters Oct1 and Oct2 [Oct1/2(-/-) mice], indicating that carnitine itself undergoes basolateral uptake into the kidney. Transport of carnitine by OCT2, but not OCT1, was confirmed in transfected cells. We also found that cisplatin caused an increase in the urinary excretion of carnitine and acetylcarnitine in wild-type mice but not in Oct1/2(-/-) mice, suggesting that tubular transport of cisplatin is a prerequisite for this phenomenon. Cisplatin did not directly inhibit the transport of carnitine by Octn2 but downregulated multiple target genes of the transcription factor peroxisome proliferator activated receptor α, including Slc22a5, in the kidney of wild-type mice that were absent in Oct1/2(-/-) mice. CONCLUSION: Our study shows a pivotal role of Oct1 and Oct2 in cisplatin-related disturbances in carnitine homeostasis. We postulate that this phenomenon is triggered by deactivation of peroxisome proliferator activated receptor α and leads to deregulation of carnitine-shuttle genes.

Influence of Oct1/Oct2-deficiency on cisplatin-induced changes in urinary N-acetyl-beta-D-glucosaminidase.

PURPOSE: This study aimed to test the influence of functional renal organic cation transporters (OCT2 in humans, Oct1 and Oct2 in mice) on biomarkers of cisplatin nephrotoxicity, such as urinary activity of N-acetyl-beta-D-glucosaminidase (NAG). EXPERIMENTAL DESIGN: Temporal cisplatin-induced nephrotoxicity was assessed by histopathology and biomarkers. Cisplatin-mediated NAG changes and survival were determined in wild-type and Oct1/2(-/-) mice. Identification of OCT2 inhibitors was done in transfected 293Flp-In cells, and the NCI(60) cell line panel was used to assess contribution of OCT2 to cisplatin uptake in cancer cells. RESULTS: Classical biomarkers such as blood urea nitrogen and serum creatinine were not elevated until 72 hours after cisplatin administration and substantial kidney damage had occurred. Oct1/2(-/-) mice had 2.9-fold lower NAG by 4 hours (P < 0.0001) and 2.3-fold increased survival (P = 0.0097). Among 16 agents, cimetidine strongly inhibited uptake of tetraethylammonium bromide (P = 0.0006) and cisplatin (P < 0.0001), but did not have an influence on cisplatin uptake in SK-OV-3 cells, the cancer line with the highest OCT2 mRNA levels. In wild-type mice, cimetidine inhibited cisplatin-induced NAG changes (P = 0.016 versus cisplatin alone) to a degree similar to that seen in Oct1/2(-/-) mice receiving cisplatin (P = 0.91). Cumulative NAG activity of >0.4 absorbance units (AU) was associated with 21-fold increased odds for severe nephrotoxicity (P = 0.0017), which was linked with overall survival (hazard ratio, 8.1; 95% confidence interval, 2.1-31; P = 0.0078). CONCLUSIONS: Cimetidine is able to inhibit OCT2-mediated uptake of cisplatin in the kidney, and subsequently ameliorate nephrotoxicity likely with minimal effect on uptake in tumor cells.