The Role of Transporters in the Toxicity of Chemotherapeutic Drugs: Focus on Transporters for Organic Cations

The equivalence of different types of electric pulses for electrochemotherapy with cisplatin - an in vitro study

BACKGROUND

Electrochemotherapy (ECT) is a treatment involving the administration of chemotherapeutics drugs followed by the application of 8 square monopolar pulses of 100 μs duration at a repetition frequency of 1 Hz or 5000 Hz. However, there is increasing interest in using alternative types of pulses for ECT. The use of high-frequency short bipolar pulses has been shown to mitigate pain and muscle contractions. Conversely, the use of millisecond pulses is interesting when combining ECT with gene electrotransfer for the uptake of DNA-encoding proteins that stimulate the immune response with the aim of converting ECT from a local to systemic treatment. Therefore, the aim of this study was to investigate how alternative types of pulses affect the efficiency of the ECT.

MATERIALS AND METHODS

We performed in vitro experiments, exposing Chinese hamster ovary (CHO) cells to conventional ECT pulses, high-frequency bipolar pulses, and millisecond pulses in the presence of different concentrations of cisplatin. We determined cisplatin uptake by inductively coupled plasma mass spectrometry and cisplatin cytotoxicity by the clonogenic assay.

RESULTS

We observed that the three tested types of pulses potentiate the uptake and cytotoxicity of cisplatin in an equivalent manner, provided that the electric field is properly adjusted for each pulse type. Furthermore, we quantified that the number of cisplatin molecules, resulting in the eradication of most cells, was 2-7 × 107 per cell.

CONCLUSIONS

High-frequency bipolar pulses and millisecond pulses can potentially be used in ECT to reduce pain and muscle contraction and increase the effect of the immune response in combination with gene electrotransfer, respectively.

OCT1-dependent uptake of structurally diverse pyrrolizidine alkaloids in human liver cells is crucial for their genotoxic and cytotoxic effects

Pyrrolizidine alkaloids (PAs) are important plant hepatotoxins, which occur as contaminants in plant-based foods, feeds and phytomedicines. Numerous studies demonstrated that the genotoxicity and cytotoxicity of PAs depend on their chemical structure, allowing for potency ranking and grouping. Organic cation transporter-1 (OCT1) was previously shown to be involved in the cellular uptake of the cyclic PA diesters monocrotaline, retrorsine and senescionine. However, little is known about the structure-dependent transport of PAs. Therefore, we investigated the impact of OCT1 on the uptake and toxicity of three structurally diverse PAs (heliotrine, lasiocarpine and riddelliine) differing in their degree and type of esterification in metabolically competent human liver cell models and hamster fibroblasts. Human HepG2-CYP3A4 liver cells were exposed to the respective PA in the presence or absence of the OCT1-inhibitors D-THP and quinidine, revealing a strongly attenuated cytotoxicity upon OCT1 inhibition. The same experiments were repeated in V79-CYP3A4 hamster fibroblasts, confirming that OCT1 inhibition prevents the cytotoxic effects of all tested PAs. Interestingly, OCT1 protein levels were much lower in V79-CYP3A4 than in HepG2-CYP3A4 cells, which correlated with their lower susceptibility to PA-induced cytotoxicity. The cytoprotective effect of OCT1 inhibiton was also demonstrated in primary human hepatocytes following PA exposure. Our experiments further showed that the genotoxic effects triggered by the three PAs are blocked by OCT1 inhibition as evidenced by strongly reduced γH2AX and p53 levels. Consistently, inhibition of OCT1-mediated uptake suppressed the activation of the DNA damage response (DDR) as revealed by decreased phosphorylation of checkpoint kinases upon PA treatment. In conclusion, we demonstrated that PAs, independent of their degree of esterification, are substrates for OCT1-mediated uptake into human liver cells. We further provided evidence that OCT1 inhibition prevents PA-triggered genotoxicity, DDR activation and subsequent cytotoxicity. These findings highlight the crucial role of OCT1 together with CYP3A4-dependent metabolic activation for PA toxicity.

Interaction of ALK Inhibitors with Polyspecific Organic Cation Transporters and the Impact of Substrate-Dependent Inhibition on the Prediction of Drug-Drug Interactions

Small molecules targeting aberrant anaplastic lymphoma kinase (ALK) are active against ALK-positive non-small-cell lung cancers and neuroblastoma. Several targeted tyrosine kinase inhibitors (TKIs) have been shown to interact with polyspecific organic cation transporters (pOCTs), raising concerns about potential drug-drug interactions (DDIs). The purpose of this study was to assess the interaction of ALK inhibitors with pOCTs and the impact of substrate-dependent inhibition on the prediction of DDIs. Inhibition assays were conducted in transporter-overexpressing cells using meta-iodobenzylguanidine (mIBG), metformin, or 1-methyl-4-phenylpyridinium (MPP+) as the substrate. The half-maximal inhibitory concentrations (IC50) of brigatinib and crizotinib for the substrates tested were used to predict their potential for in vivo transporter mediated DDIs. Here, we show that the inhibition potencies of brigatinib and crizotinib on pOCTs are isoform- and substrate-dependent. Human OCT3 (hOCT3) and multidrug and toxin extrusion protein 1 (hMATE1) were highly sensitive to inhibition by brigatinib and crizotinib for all three tested substrates. Apart from hMATE1, substrate-dependent inhibition was observed for all other transporters with varying degrees of dependency; hOCT1 inhibition showed the greatest substrate dependency, with differences in IC50 values of up to 22-fold across the tested substrates, followed by hOCT2 and hMATE2-K, with differences in IC50 values of up to 16- and 12-fold, respectively. Conversely, hOCT3 inhibition only showed a moderate substrate dependency (IC50 variance < 4.8). Among the substrates used, metformin was consistently shown to be the most sensitive substrate, followed by mIBG and MPP+. Pre-incubation of ALK inhibitors had little impact on their potencies toward hOCT2 and hMATE1. Our results underscore the complexity of the interactions between substrates and the inhibitors of pOCTs and have important implications for the clinical use of ALK inhibitors and their DDI predictions.

Influence of proton pump inhibitors on the pathological response of rectal cancer: a multicentre study

Background

The standard neoadjuvant therapy for rectal cancer involves fluoropyrimidines and radiotherapy and, most recently, total neoadjuvant therapy (TNT). A drug-drug interaction between fluoropyrimidines and proton-pump inhibitors (PPI) was suggested, with a negative impact on oncological outcomes in breast, colon and gastric cancers. Little is known about such an effect on rectal tumours. We aimed to evaluate the impact of PPI utilisation on the pathological response after chemoradiation for rectal cancer.

Materials and methods

Retrospective multicentre study of rectal cancer patients treated with neoadjuvant chemoradiotherapy with capecitabine (cohort 1) or 5-fluororuracil (5-FU) (cohort 2); TNT with oxaliplatin-based regimens was allowed. The pathological response was considered a complete (ypCR) or complete + partial (ypCR + ypPR) according to American Joint Committee on Cancer. PPI use was considered at any time during the neoadjuvant period if concomitant to fluoropyrimidines.

Results

From January 2007 to November 2020, 251 patients received capecitabine and 196 5-FU. The rates of PPI use in cohorts 1 and 2 were 20.3% and 26.5%, respectively. TNT was offered to 18.3% in cohort 1. PPI use did not influence ypCR in cohort 1 (yes versus no: 29.4% versus 19.5%; p = 0.13) or 2 (yes versus no: 25.0% versus 26.4%; p = 1.0). Similar ypCR + ypPR were observed in both cohorts 1 (76.5% versus 72.0%; p = 0.60) and 2 (86.5% versus 76.4%; p = 0.16). PPI use was not associated with pathological response in multivariable analysis. PPI users experienced more grade 3 or higher diarrhoea and infections.

Conclusion

PPI concomitant to capecitabine/5-FU chemoradiation did not influence the pathological response in rectal cancer but was associated with more treatment-related adverse events.

Nanosecond electric pulses are equally effective in electrochemotherapy with cisplatin as microsecond pulses

BACKGROUND

Nanosecond electric pulses showed promising results in electrochemotherapy, but the underlying mechanisms of action are still unexplored. The aim of this work was to correlate cellular cisplatin amount with cell survival of cells electroporated with nanosecond or standardly used 8 × 100 μs pulses and to investigate the effects of electric pulses on cisplatin structure.

MATERIALS AND METHODS

Chinese hamster ovary CHO and mouse melanoma B16F1 cells were exposed to 1 × 200 ns pulse at 12.6 kV/cm or 25 × 400 ns pulses at 3.9 kV/cm, 10 Hz repetition rate or 8 × 100 μs pulses at 1.1 (CHO) or 0.9 (B16F1) kV/cm, 1 Hz repetition rate at three cisplatin concentrations. Cell survival was determined by the clonogenic assay, cellular platinum was measured by inductively coupled plasma mass spectrometry. Effects on the structure of cisplatin were investigated by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.

RESULTS

Nanosecond pulses equivalent to 8 × 100 μs pulses were established in vitro based on membrane permeabilization and cell survival. Equivalent nanosecond pulses were equally efficient in decreasing the cell survival and accumulating cisplatin intracellularly as 8 × 100 μs pulses after electrochemotherapy. The number of intracellular cisplatin molecules strongly correlates with cell survival for B16F1 cells, but less for CHO cells, implying the possible involvement of other mechanisms in electrochemotherapy. The high-voltage electric pulses did not alter the structure of cisplatin.

CONCLUSIONS

Equivalent nanosecond pulses are equally effective in electrochemotherapy as standardly used 8 × 100 μs pulses.

Role of Drug Transporters in Elucidating Inter-Individual Variability in Pediatric Chemotherapy-Related Toxicities and Response

Pediatric cancer treatment has evolved significantly in recent decades. The implementation of risk stratification strategies and the selection of evidence-based chemotherapy combinations have improved survival outcomes. However, there is large interindividual variability in terms of chemotherapy-related toxicities and, sometimes, the response among this population. This variability is partly attributed to the functional variability of drug-metabolizing enzymes (DME) and drug transporters (DTS) involved in the process of absorption, distribution, metabolism and excretion (ADME). The DTS, being ubiquitous, affects drug disposition across membranes and has relevance in determining chemotherapy response in pediatric cancer patients. Among the factors affecting DTS function, ontogeny or maturation is important in the pediatric population. In this narrative review, we describe the role of drug uptake/efflux transporters in defining pediatric chemotherapy-treatment-related toxicities and responses. Developmental differences in DTS and the consequent implications are also briefly discussed for the most commonly used chemotherapeutic drugs in the pediatric population.

Nephrotoxicity in cancer treatment: An update

It has been estimated that nearly 80% of anticancer drug-treated patients receive potentially nephrotoxic drugs, while the kidneys play a central role in the excretion of anticancer drugs. Nephrotoxicity has long been a serious complication that hampers the effectiveness of cancer treatment and continues to influence both mortality and length of hospitalization among cancer patients exposed to either conventional cytotoxic agents or targeted therapies. Kidney injury arising from anticancer drugs tends to be associated with preexisting comorbidities, advanced cancer stage, and the use of concomitant non-chemotherapeutic nephrotoxic drugs. Despite the prevalence and impact of kidney injury on therapeutic outcomes, the field is sorely lacking in an understanding of the mechanisms driving cancer drug-induced renal pathophysiology, resulting in quite limited and largely ineffective management of anticancer drug-induced nephrotoxicity. Consequently, there is a clear imperative for understanding the basis for nephrotoxic manifestations of anticancer agents for the successful management of kidney injury by these drugs. This article provides an overview of current preclinical research on the nephrotoxicity of cancer treatments and highlights prospective approaches to mitigate cancer therapy-related renal toxicity.

Contribution of membrane transporters to chemotherapy-induced cardiotoxicity

Membrane transporters play a key role in determining the pharmacokinetic profile, therapeutic safety, and efficacy of many chemotherapeutic drugs by regulating cellular influx and efflux. Rapidly emerging evidence has shown that tissue-specific expression of transporters contributes to local drug accumulation and drug-drug interactions and that functional alterations in these transporters can directly influence an individual's susceptibility to drug-induced toxicity. Comprehending the complex mechanism of transporter function in regulating drug distribution in tissues, such as the heart, is necessary in order to acquire novel therapeutic strategies aimed at evading unwanted drug accumulation and toxicities and to ameliorate the safety of current therapeutic regimens. Here, we provide an overview of membrane transporters with a role in chemotherapy-induced cardiotoxicity and discuss novel strategies to improve therapeutic outcomes.

The Mechanism of Drug Nephrotoxicity and the Methods for Preventing Kidney Damage

Acute kidney injury (AKI) is a global health challenge of vast proportions, as approx. 13.3% of people worldwide are affected annually. The pathophysiology of AKI is very complex, but its main causes are sepsis, ischemia, and nephrotoxicity. Nephrotoxicity is mainly associated with the use of drugs. Drug-induced AKI accounts for 19-26% of all hospitalized cases. Drug-induced nephrotoxicity develops according to one of the three mechanisms: (1) proximal tubular injury and acute tubular necrosis (ATN) (a dose-dependent mechanism), where the cause is related to apical contact with drugs or their metabolites, the transport of drugs and their metabolites from the apical surface, and the secretion of drugs from the basolateral surface into the tubular lumen; (2) tubular obstruction by crystals or casts containing drugs and their metabolites (a dose-dependent mechanism); (3) interstitial nephritis induced by drugs and their metabolites (a dose-independent mechanism). In this article, the mechanisms of the individual types of injury will be described. Specific groups of drugs will be linked to specific injuries. Additionally, the risk factors for the development of AKI and the methods for preventing and/or treating the condition will be discussed.

Targeted delivery in scleroderma fibrosis

Systemic sclerosis (SSc) is considered one of the most challenging and difficult to treat among rheumatic disorders, due to its severity, multiorgan manifestation and different outcomes. It manifests fibrosis in different organs, mostly in skin and lungs. The skin fibrosis expression is considered the first sign of the disease and usually it is followed by internal organ fibrosis. An aberrant immune system activation seems to relate to the expression of the disease, but even environmental influences and dysregulation of many molecules signalling pathways are involved in the development of the disease. Current therapies are limited and characterized by multiple side effects: systemic route is the elective administration route, which decreases patient adherence to the therapy, as they are often already bothered by pain and disfigurement. Treatments available are organ-based, originally indicated for other conditions and there is no therapy available to reduce the fibroblast population size within existing fibrotic lesions. Disease-modifying therapies or immunomodulatory agents that are highly effective in other rheumatic diseases have shown disappointing results in SSc. There are thus no standardized and effective treatments for this disease, and there are even unanswered questions related to the insurgence of the pathology and all the mechanisms involved. An ideal approach could be considered "targeted therapy" that will be an increasingly attainable objective insofar as our understanding of the disease improves. The advantages in identifying the molecule and the signalling pathways involved in the pathology have helped to find some novel compounds for the therapy of scleroderma fibrosis or following innovative uses for already-approved drugs, corroborated by many clinical studies.

Tucatinib Inhibits Renal Transporters OCT2 and MATE Without Impacting Renal Function in Healthy Subjects

Tucatinib is a potent tyrosine kinase inhibitor selective for human epidermal growth factor receptor 2 (HER2) approved by the US Food and Drug Administration for the treatment of HER2‐positive metastatic breast cancer and in development for other HER2‐positive solid tumors. Modest, reversible serum creatinine (SCr) elevations have been observed in tucatinib clinical trials. SCr is conveyed by the renal drug transporters organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) and 2‐K (MATE2‐K) and can increase in the presence of inhibitors of these transporters. In vitro, tucatinib inhibited OCT2‐, MATE1‐, and MATE2‐K‐mediated transport of metformin, with IC₅₀ values of 14.7, 0.340, and 0.135 µM, respectively. Tucatinib also inhibited OCT2‐ and MATE1‐mediated transport of creatinine, with IC₅₀ values of 0.107 and 0.0855 µM, respectively. A phase 1 study with metformin administered orally in the absence and presence of tucatinib was conducted in 18 healthy subjects. Renal function was assessed by measuring glomerular filtration rate (GFR; based on iohexol plasma clearance) and endogenous markers (SCr, cystatin C‐based estimated glomerular filtration rate [eGFR]) with and without tucatinib. Metformin exposure increased (1.4‐fold) and renal clearance decreased (29.99‐17.64 L/h) with tucatinib, with no effect on metformin maximum concentration. Creatinine clearance transiently decreased 23% with tucatinib. GFR and eGFR, which are unaffected by OCT2 and/or MATE1/2‐K transport, were unchanged with tucatinib. These data demonstrate that tucatinib inhibits OCT2‐ and MATE1/2‐K‐mediated tubular secretion of creatinine, which may manifest as mild SCr elevations that are not indicative of renal impairment.

Ototoxicity and Platinum Uptake Following Cyclic Administration of Platinum-Based Chemotherapeutic Agents

Cisplatin is a widely used anti-cancer drug used to treat a variety of cancer types. One of the side effects of this life-saving drug is irreversible ototoxicity, resulting in permanent hearing loss in many patients. In order to understand why cisplatin is particularly toxic to the inner ear, we compared the hearing loss and cochlear uptake of cisplatin to that of two related drugs, carboplatin and oxaliplatin. These three drugs are similar in that each contains a core platinum atom; however, carboplatin and oxaliplatin are considered less ototoxic than cisplatin. We delivered these three drugs to mice using a 6-week cyclic drug administration protocol. We performed the experiment twice, once using equimolar concentrations of the drugs and once using concentrations of the drugs more proportional to those used in the clinic. For both concentrations, we detected a significant hearing loss caused by cisplatin and no hearing loss caused by carboplatin or oxaliplatin. Cochlear uptake of each drug was measured using inductively coupled plasma mass spectrometry (ICP-MS) to detect platinum. Cochlear platinum levels were highest in mice treated with cisplatin followed by oxaliplatin, while carboplatin was largely excluded from the cochlea. Even when the drug doses were increased, cochlear platinum remained low in mice treated with oxaliplatin or carboplatin. We also examined drug clearance from the inner ear by measuring platinum levels at 1 h and 24 h after drug administration. Our findings suggest that the reduced cochlear platinum we observed with oxaliplatin and carboplatin were not due to increased clearance of these drugs relative to cisplatin. Taken together, our data indicate that the differential ototoxicity among cisplatin, carboplatin, and oxaliplatin is attributable to differences in cochlear uptake of these three drugs.

Organic Cation Transporters (OCTs) in EpiAirway™, A Cellular Model of Normal Human Bronchial Epithelium

Organic cation transporters (OCTs) and novel organic cation transporters (OCTNs) are responsible for drug delivery in the intestine and kidney; in the lung, OCTs mediate inhaled drugs’ transport, although their physiological role in airways remains poorly understood. The studies addressing OCTs/OCTNs in human airways were mostly performed in immortal or transformed cell lines; here, we studied OCTs in EpiAirway™, a recently developed in vitro model of normal bronchial epithelium. Calu-3 monolayers were used for comparison. The activity of OCTs was evaluated by measuring the uptake of 1-methyl-4-phenylpyridinium (MPP⁺) at the apical and basolateral side of monolayers and protein expression through Western Blot analysis. OCTs and OCTNs expression, along with that of Amino acid Transporter B^0,+ (ATB^0,+)transporter, was determined by measuring the number of mRNA molecules through quantitative Polymerase Chain Reaction (qPCR). The interaction of the transporters with bronchodilators was also assessed. Results highlight significant differences between Calu-3 cells and EpiAirway™, since, in the latter, OCTs are active only on the basolateral membrane where they interact with the bronchodilator ipratropium. No activity of OCTs is detectable at the apical side; there, the most abundant carrier is, instead, SLC6A14/ATB^0,+, that can thus be potentially listed among organic cation transporters responsible for drug delivery in the lung.

Drug-induced acute kidney injury: diverse mechanisms of tubular injury

PURPOSE OF REVIEW

Medications are a relatively common cause of acute kidney injury (AKI), especially in hospitalized patients who are exposed to numerous agents. Drug-related acute tubular/tubulointerstitial injury is the most common cause of AKI associated with these agents. Toxic effects of drugs and their renal handling often lead to various forms of AKI.

RECENT FINDINGS

The inherent nephrotoxicity of drugs and their transport and metabolism by the kidneys play an important role in the occurrence of acute tubular injury. Apical transport of the aminoglycosides by endocytosis and apical pinocytosis of filtered hydroxyethyl starch into cells lead to acute tubular dysfunction. Transport of tenofovir and cisplatin by organic anion and cation transporters in the basolateral surface of the proximal tubule, respectively, are associated with intracellular drug accumulation and injury. Intratubular deposition of drug crystals with associated AKI occurs with several drugs, in particular the anticancer agent methotrexate. A potentially new mechanism of drug-induced AKI was described with vancomycin - acute vancomycin-related cast nephropathy. Immune-mediated acute tubulointerstitial injury is another cause of drug-induced AKI, as seen with immune checkpoint inhibitors.

SUMMARY

Drugs lead to AKI through mechanisms that involve their inherent toxicity as well as their transport and handling by the kidneys.

An integrative approach to cisplatin chronic toxicities in mice reveals importance of organic cation-transporter-dependent protein networks for renoprotection

Cisplatin (CDDP) is one of the most important chemotherapeutic drugs in modern oncology. However, its use is limited by severe toxicities, which impair life quality after cancer. Here, we investigated the role of organic cation transporters (OCT) in mediating toxicities associated with chronic (twice the week for 4 weeks) low-dose (4 mg/kg body weight) CDDP treatment (resembling therapeutic protocols in patients) of wild-type (WT) mice and mice with OCT genetic deletion (OCT1/2^-/-). Functional and molecular analysis showed that OCT1/2^-/- mice are partially protected from CDDP-induced nephrotoxicity and peripheral neurotoxicity, whereas ototoxicity was not detectable. Surprisingly, proteomic analysis of the kidneys demonstrated that genetic deletion of OCT1/2 itself was associated with significant changes in expression of proinflammatory and profibrotic proteins which are part of an OCT-associated protein network. This signature directly regulated by OCT consisted of three classes of proteins, viz., profibrotic proteins, proinflammatory proteins, and nutrient sensing molecules. Consistent with functional protection, CDDP-induced proteome changes were more severe in WT mice than in OCT1/2^-/- mice. Laser ablation-inductively coupled plasma-mass spectrometry analysis demonstrated that the presence of OCT was not associated with higher renal platinum concentrations. Taken together, these results redefine the role of OCT from passive membrane transporters to active modulators of cell signaling in the kidney.

Paclitaxel-tyroserleutide Conjugates Self-assembly into Nanocarrier for Drug Delivery

Background:

The drug-drug self-assembly was considered as a simple and efficient approach to prepare high drug loading nano-drug carriers and present new opportunities for cancer therapeutics. The strategy of PTX amphiphiles preparation would be a possible way to solve the poor water solubility of PTX.

Methods:

The PTX-YSL conjugate were synthesized and characterized. The PTX-YSL nanocarriers was prepared by a simple self-assembly method. In vitro cell studies and pharmacokinetic studies were evaluated for their in vitro anti-tumor activities and blood retention time.

Results:

The structures of PTX-YSL conjugate were confirmed by LC-MS, 1H NMR and FTIR. The size and morphology of the PTX-YSL self-assembled nanocarriers were observed with TEM and DLS. PTX-YSL nanocarriers could facilitate cellular uptake and had low cytotoxicity. PTX-YSL nanocarriers have longer blood retention for enhancing accumulation in the tumor tissues via EPR effect.

Conclusion:

This drug delivery system formed by PTX-YSL conjugates constitutes a promising and effective drug carrier in cancer therapy.

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

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

Managing Pharmacotherapy in People Living With HIV and Concomitant Malignancy

Objective: To describe data with selected malignancies in people living with HIV (PLWH) and HIV in individuals affected by both conditions and to summarize drug-drug interactions (DDIs) with clinical recommendations for point-of-care review of combination therapies. Data Sources: Literature searches were performed (2005 to December 2018) in MEDLINE and EMBASE to identify studies of malignancies in PLWH in the modern era. Study Selection and Data Extraction: Article bibliographies and drug interaction databases were reviewed. Search terms included HIV, antiretroviral therapy, antineoplastic agents, malignancies, and drug interactions. Data Synthesis: In the pre-antiretroviral therapy (ART) era, malignancies in PLWH were AIDS-defining illnesses, and life expectancy was shorter. Nowadays, PLWH are living longer and developing malignancies, including lung, anal, and prostate cancers. Concurrently, the oncology landscape has evolved, with novel oral targeted agents and immunotherapies becoming routine elements of care. The increased need for and complexity with antineoplastics in PLWH has led to recommendations for multidisciplinary care of this unique population. Evaluation of DDIs requires review of metabolic pathways, absorption mechanisms, and various drug transporters associated with antineoplastics and ART. Relevance to Patient Care and Clinical Practice: This review summarizes available data of non-AIDS-defining malignancies, principles of HIV care in the patient with malignancy, and guidance for assessing DDIs between antineoplastics and ART. Summary DDI tables provide point-of-care recommendations. Conclusions: The availability of ART has transformed AIDS into a chronic medical condition, and PLWH are experiencing age-related malignancies. Pharmacists play an important role in the management of this patient population.

Pharmacology behind Common Drug Nephrotoxicities

Patients are exposed to numerous prescribed and over-the-counter medications. Unfortunately, drugs remain a relatively common cause of acute and chronic kidney injury. A combination of factors including the innate nephrotoxicity of drugs, underlying patient characteristics that increase their risk for kidney injury, and the metabolism and pathway of excretion by the kidneys of the various agents administered enhance risk for drug-induced nephrotoxicity. This paper will review these clinically relevant aspects of drug-induced nephrotoxicity for the clinical nephrologist.

Notch Signaling Activity Determines Uptake and Biological Effect of Imatinib in Systemic Sclerosis Dermal Fibroblasts

Tyrosine kinase inhibitors have emerged as a therapeutic option for rheumatic diseases such as systemic sclerosis (SSc). Because tyrosine kinases like c-Abl kinase are important for fibroblast activation and fibrosis development in SSc, the c-Abl inhibitor imatinib was proposed for SSc treatment. Transporters for organic cations have become increasingly recognized as an important determinant for uptake and efficacy of tyrosine kinase inhibitors. Therefore, we investigated the role of organic cation transporters in the uptake of imatinib. Moreover, the influence of important SSc pathogenetic factors, like PDGF and Notch pathway activation on these uptake processes, has been studied. We showed that organic cation transporters OCT1-3, novel organic cation transporters OCTN1/2, and the multidrug and toxin extrusion protein MATE1 are expressed in healthy dermal and SSc fibroblasts. Decreased expression levels of MATE1 and decreased imatinib uptake were measured in SSc fibroblasts. In small interfering RNA experiments, MATE1 was identified as key transporter for imatinib uptake and biological effect in dermal fibroblasts. Furthermore, PDGF reduced imatinib uptake by decreasing MATE1 expression in SSc fibroblasts, but not in healthy fibroblasts. Blocking the Notch pathway in SSc fibroblasts increased MATE1 transporter expression and imatinib uptake. In conclusion, MATE1-mediated transport governs therapeutic efficacy of imatinib in SSc.

Interaction of the New Monofunctional Anticancer Agent Phenanthriplatin With Transporters for Organic Cations

Cancer treatment with platinum compounds is an important achievement of modern chemotherapy. However, despite the beneficial effects, the clinical impact of these agents is hampered by the development of drug resistance as well as dose-limiting side effects. The efficacy but also side effects of platinum complexes can be mediated by uptake through plasma membrane transporters. In the kidneys, plasma membrane transporters are involved in their secretion into the urine. Renal secretion is accomplished by uptake from the blood into the proximal tubules cells, followed by excretion into the urine. The uptake process is mediated mainly by organic cation transporters (OCT), which are expressed in the basolateral domain of the plasma membrane facing the blood. The excretion of platinum into the urine is mediated by exchange with protons via multidrug and toxin extrusion proteins (MATE) expressed in the apical domain of plasma membrane. Recently, the monofunctional, cationic platinum agent phenanthriplatin, which is able to escape common cellular resistance mechanisms, has been synthesized and investigated. In the present study, the interaction of phenanthriplatin with transporters for organic cations has been evaluated. Phenanthriplatin is a high affinity substrate for OCT2, but has a lower apparent affinity for MATEs. The presence of these transporters increased cytotoxicity of phenanthriplatin. Therefore, phenanthriplatin may be especially effective in the treatment of cancers that express OCTs, such as colon cancer cells. However, the interaction of phenanthriplatin with OCTs suggests that its use as chemotherapeutic agent may be complicated by OCT-mediated toxicity. Unlike cisplatin, phenanthriplatin interacts with high specificity with hMATE1 and hMATE2K in addition to hOCT2. This interaction may facilitate its efflux from the cells and thereby decrease overall efficacy and/or toxicity.

Sodium cholate-enhanced polymeric micelle system for tumor-targeting delivery of paclitaxel

PURPOSE

Polymeric micelles are attractive nanocarriers for tumor-targeted delivery of paclitaxel (PTX). High antitumor efficacy and low toxicity require that PTX mainly accumulated in tumors with little drug exposure to normal tissues. However, many PTX-loaded micelle formulations suffer from low stability, fast drug release, and lack of tumor-targeting capability in the circulation. To overcome these challenges, we developed a micellar formulation that consists of sodium cholate (NaC) and monomethoxy poly (ethylene glycol)-block-poly (d,l-lactide) (mPEG-PDLLA).

METHODS

PTX-loaded NaC-mPEG-PDLLA micelles (PTX-CMs) and PTX-loaded mPEG-PDLLA micelles (PTX-Ms) were formulated, and their characteristics, particle size, surface morphology, release behavior in vitro, pharmacokinetics and in vivo biodistributions were researched. In vitro and in vivo tumor inhibition effects were systematically investigated. Furthermore, the hemolysis and acute toxicity of PTX-CMs were also evaluated.

RESULTS

The size of PTX-CMs was 53.61±0.75 nm and the ζ-potential was -19.73±0.68 mV. PTX was released much slower from PTX-CMs than PTX-Ms in vitro. Compared with PTX-Ms, the cellular uptake of PTX-CMs was significantly reduced in macrophages and significantly increased in human cancer cells, and therefore, PTX-CMs showed strong growth inhibitory effects on human cancer cells. In vivo, the plasma AUC0-t of PTX-CMs was 1.8-fold higher than that of PTX-Ms, and 5.2-fold higher than that of Taxol. The biodistribution study indicated that more PTX-CMs were accumulated in tumor than PTX-Ms and Taxol. Furthermore, the significant antitumor efficacy of PTX-CMs was observed in mice bearing BEL-7402 hepatocellular carcinoma and A549 lung carcinoma. Results from drug safety assessment studies including acute toxicity and hemolysis test revealed that the PTX-CMs were safe for in vivo applications.

CONCLUSION

These results strongly revealed that NaC-mPEG-PDLLA micelles can tumor-target delivery of PTX and enhance drug penetration in tumor, suggesting that NaC-mPEG-PDLLA micelles are promising nanocarrier systems for anticancer drugs delivery.

Role of Pannexin1 channels in the resistance of I-10 testicular cancer cells to cisplatin mediated by ATP/IP3 pathway

Cisplatin (DDP) is the most commonly used drug in testicular cancer. However, drug resistance severely limits its clinical use and the underlying mechanisms need to be further clarified. The aim of present study was to investigate the role of ATP/IP₃ pathway mediated by pannexin1 (Panx-1) channels on DDP-induced apoptosis and to reveal the potential mechanisms of DDP-resistance in testicular cancer. We found that the expression of Panx-1 in I-10/DDP cells (DDP-resistance) was decreased compared with parental I-10 cells determined by western blotting and immunofluorescence assay. To further clarify the role of Panx-1 in DDP resistance, Panx-1 function was modulated by overexpression and knockdown of Panx-1 expression. Panx-1 overexpression increased DDP-induced apoptosis, ATP release and IP₃ levels. On the contrary, Panx-1 silencing decreased DDP-induced apoptosis, ATP release and IP₃ levels. Apyrase (hydrolyzing extracellular ATP) or xestospongin C (antagonizing IP₃ receptor) also decreased DDP-induced apoptosis. Our findings demonstrate that Panx-1 is involved in DDP-resistance and ATP/IP₃ pathway mediated by Panx-1 channels participates in DDP-induced apoptosis in testicular cancer. Panx-1 modulation may be interesting to amplify the clinical effect of DDP and reverse the resistance of testicular cancer cells to DDP.

Intracellular uptake of an antitumor-active azole-bridged dinuclear platinum(II) complex in cisplatin-resistant tumor cells

A cationic azolato-bridged dinuclear platinum(II) complex, [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-methyl-pyrazolate)]²⁺ (4M-PzPt), was developed to overcome resistance to cisplatin (CDDP). This study aimed to assess the cytotoxicity of 4M-PzPt against a CDDP-resistant cell line, H4-II-E/CDDP, and compare the intracellular accumulation of CDDP and 4M-PzPt. H4-II-E and H4-II-E/CDDP displayed similar sensitivity to 4M-PzPt; however, the sensitivity of H4-II-E/CDDP to CDDP was approximately 19-fold lower than that of H4-II-E. The difference in the sensitivity to both platinum complexes corresponded with the difference in the amount of intracellular platinum accumulation after exposure to CDDP or 4M-PzPt in both cell lines. In H4-II-E, HepG2, and HuH-7 cells, the intracellular uptake of CDDP and 4M-PzPt occurred via active transport and passive transport. Results of co-exposure with the transport inhibitors ouabain, tetraethylammonium, and cimetidine indicated that the intracellular uptake of CDDP was dependent on Na⁺/K⁺-ATPase and that of 4M-PzPt was dependent on organic cation transporters (OCTs), probably OCT1. This study suggested that 4M-PzPt could inhibit the growth of a CDDP-resistant tumor via an intracellular uptake mechanism different from that of CDDP.