Estimation of Absolute and Relative Body Fat Content Using Noninvasive Surrogates: Can DXA Be Bypassed?

Dual-energy x-ray absorptiometry (DXA) scanning is used for objective determination of body composition, but instrumentation is expensive and not generally available in customary clinical practice. Anthropometric surrogates are often substituted as anticipated correlates of absolute and relative body fat content in the clinical management of obesity and its associated medical risks. DXA and anthropometric data from a cohort of 9230 randomly selected American subjects, available through the ongoing National Health and Nutrition Examination Survey, was used to evaluate combinations of surrogates (age, height, total weight, waist circumference) as predictors of DXA-determined absolute and relative body fat content. Multiple regression analysis yielded linear combinations of the 4 surrogates that were closely predictive of DXA-determined absolute fat content (R2  = 0.93 and 0.96 for male and female subjects). Accuracy of the new algorithm was improved over customary surrogate-based predictors such as body mass index. However prediction of relative body fat was less robust (R2  less than 0.75), probably due to the nonlinear relation between degree of obesity (based on body mass index) and relative body fat. The paradigm was validated using an independent cohort from the National Health and Nutrition Examination Survey, as well as two independent external subject groups. The described regression-based algorithm is likely to be a sufficiently accurate predictor of absolute body fat (but not relative body fat) to substitute for DXA scanning in many clinical situations. Further work is needed to assess algorithm validity for subgroups of individuals with "atypical" body construction.

Clinical Consequences of Altered Drug Disposition in Obesity: Call for Change.

Obesity is a serious condition with many known comorbid conditions and other health risks. Despite the rising global rates of obesity, drug disposition in this population is typically understudied, which results in limited information guiding the use of drugs in patients with obesity. Presently, dosing adjustments for patients with obesity typically focus on addressing altered drug clearance with body size and are therefore limited to chronic dosing recommendations. These instructions are variable and rarely based on dedicated studies in people with obesity. This review briefly discusses the current clinical use of body measurements to guide chronic dosing instructions and highlights the need for obesity-specific dosing instructions when the half-life of a drug is prolonged (typically through increased volume of distribution) in people with obesity. Examples of drugs with apparent opportunities for either ramp-up, loading, or washout instructions for patients based on body mass index are identified, specifically for vortioxetine, posaconazole, and brexpiprazole. We call for inclusion of people with obesity in clinical studies as a special subpopulation during drug development and propose the use of body mass index to guide dosing decisions among these patients.

Incomplete Data and Potential Risks of Drugs in People with Obesity.

PURPOSE OF REVIEW: To provide examples of knowledge gaps in current pharmaceutical treatments for people with obesity and call for changes to regulatory and pharmaceutical clinical research requirements during the drug discovery and development process. RECENT FINDINGS: Treatment of obesity and its comorbidities often require the use of prescription drugs, many of which have not been fully evaluated in people with obesity. Despite a growing body of research on this topic, the impact of obesity on the pharmacokinetics and pharmacodynamics of drugs is often under-studied by drug sponsors and regulators, and subsequently underappreciated by clinicians and caretakers. There are currently multiple opportunities for pharmaceuticals to include dosing information specifically for patients with obesity in order to ensure safety and efficacy of drugs in this population. Additionally, there are serious gaps between what is known about the effects of obesity on drug disposition and the current use of drugs according to drug prescribing information and clinical practice. There is currently no requirement to test drugs in people with obesity during the drug approval process, even when preliminary data suggests there may be altered kinetics in this population. The lack of information on the safe and effective use of drugs in people with obesity may be contributing to poorer health outcomes in this population.

Drug Disposition in Subjects With Obesity: The Research Work of Darrell R. Abernethy.

In 1979, the late Dr. Darrell R. Abernethy and colleagues began a series of clinical studies aimed at understanding the pertinent determinants of drug distribution, elimination, and clearance in obesity, and how those variables are interconnected. The studies confirmed that volume of distribution (Vd ) and clearance are the principal independent biological variables, which conjointly determine elimination of half-life as a dependent variable. For drugs distributed by passive diffusion, their pharmacokinetic Vd - after correcting for plasma protein binding - was increased in obesity, depending in part on the physicochemical lipophilicity of the individual drugs, and the quantitative extent of obesity in overweight individuals. Across all studies, the ratio of mean clearance in obese divided by control groups had an overall median value of 1.21 (range, 0.75-3.11), indicating a small and variable effect of obesity on clearance, without clear directionality. Since drug clearance was not clearly related to lipophilicity or degree of obesity, the prolonged half-life of lipophilic drugs in patients with obesity was largely explained by the increased Vd . Dr. Abernethy further identified delayed attainment of steady state after initiation of multiple-dose treatment, and delayed washout after termination of dosage, as potential clinical consequences of the extended half-life in people with obesity. These consequences for specific drugs have been recently emphasized in contemporary studies of chronic dosage in subjects with obesity. Without data identifying an obesity-related change in clearance for a specific drug, maintenance doses (in milligrams) should be based on ideal weight rather than adjusted upward on the basis of total weight.

Progressive multifocal leukoencephalopathy genetic risk variants for pharmacovigilance of immunosuppressant therapies.

Background: Progressive multifocal leukoencephalopathy (PML) is a rare and often lethal brain disorder caused by the common, typically benign polyomavirus 2, also known as JC virus (JCV). In a small percentage of immunosuppressed individuals, JCV is reactivated and infects the brain, causing devastating neurological defects. A wide range of immunosuppressed groups can develop PML, such as patients with: HIV/AIDS, hematological malignancies (e.g., leukemias, lymphomas, and multiple myeloma), autoimmune disorders (e.g., psoriasis, rheumatoid arthritis, and systemic lupus erythematosus), and organ transplants. In some patients, iatrogenic (i.e., drug-induced) PML occurs as a serious adverse event from exposure to immunosuppressant therapies used to treat their disease (e.g., hematological malignancies and multiple sclerosis). While JCV infection and immunosuppression are necessary, they are not sufficient to cause PML. Methods: We hypothesized that patients may also have a genetic susceptibility from the presence of rare deleterious genetic variants in immune-relevant genes (e.g., those that cause inborn errors of immunity). In our prior genetic study of 184 PML cases, we discovered 19 candidate PML risk variants. In the current study of another 152 cases, we validated 4 of 19 variants in both population controls (gnomAD 3.1) and matched controls (JCV+ multiple sclerosis patients on a PML-linked drug ≥ 2 years). Results: The four variants, found in immune system genes with strong biological links, are: C8B, 1-57409459-C-A, rs139498867; LY9 (alias SLAMF3), 1-160769595-AG-A, rs763811636; FCN2, 9-137779251-G-A, rs76267164; STXBP2, 19-7712287-G-C, rs35490401. Carriers of any one of these variants are shown to be at high risk of PML when drug-exposed PML cases are compared to drug-exposed matched controls: P value = 3.50E-06, OR = 8.7 [3.7-20.6]. Measures of clinical validity and utility compare favorably to other genetic risk tests, such as BRCA1 and BRCA2 screening for breast cancer risk and HLA-B*15:02 pharmacogenetic screening for pharmacovigilance of carbamazepine to prevent Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis. Conclusion: For the first time, a PML genetic risk test can be implemented for screening patients taking or considering treatment with a PML-linked drug in order to decrease the incidence of PML and enable safer use of highly effective therapies used to treat their underlying disease.

Impact of Obesity on Brexpiprazole Pharmacokinetics: Proposal for Improved Initiation of Treatment.

Brexpiprazole is an oral antipsychotic agent indicated for use in patients with schizophrenia or as adjunctive treatment for major depressive disorder. As obesity (body mass index ≥35 kg/m2 ) has the potential to affect drug pharmacokinetics and is a common comorbidity of both schizophrenia and major depressive disorder, it is important to understand changes in brexpiprazole disposition in this population. This study uses a whole-body physiologically based pharmacokinetic model to compare the pharmacokinetics of brexpiprazole in obese and normal-weight (body mass index 18-25 kg/m2 ) individuals known to be cytochrome P450 2D6 extensive metabolizers (EMs) and poor metabolizers (PMs). The physiologically based pharmacokinetic simulations demonstrated significant differences in the time to effective concentrations between obese and normal-weight individuals within metabolizer groups according to the label-recommended titration. Simulations using an alternative dosing strategy of 1 week of twice-daily dosing in obese EMs or 2 weeks of twice-daily dosing in obese poor metabolizers, followed by a return to once-daily dosing, yielded more consistent plasma concentrations between normal-weight and obese patients without exceeding the area under the plasma concentration-time curve observed in the normal-weight EMs. These alternative dosing strategies reduce the time to effective concentrations in obese patients and may improve clinical response to brexpiprazole.

Brexpiprazole Pharmacokinetics in CYP2D6 Poor Metabolizers: Using Physiologically Based Pharmacokinetic Modeling to Optimize Time to Effective Concentrations.

Brexpiprazole is an oral antipsychotic agent indicated for use in patients with schizophrenia, or as adjunctive treatment for major depressive disorder. As cytochrome P450 (CYP) 2D6 contributes significantly to brexpiprazole metabolism, there is a label-recommended 50% reduction in dose among patients with the CYP2D6 poor metabolizer phenotype. This study uses a whole-body physiologically based pharmacokinetic (PBPK) model to compare the pharmacokinetics of brexpiprazole in patients known to be extensive metabolizers (EMs) and poor metabolizers (PMs). A PBPK model was constructed, verified, and validated against brexpiprazole clinical data, and simulations of 500 subjects were performed to establish the median time to effective concentrations in EMs and PMs. The PBPK simulations captured brexpiprazole PK well and demonstrated significant differences in the time to effective concentrations between EMs and PMs according to the label-recommended titration. Additionally, these simulations suggest that CYP2D6 PMs consistently achieve lower minimum concentrations during the dosing interval than CYP2D6 EMs. Simulations using an alternative dosing strategy of twice-daily dosing (as opposed to once daily) in PMs during the first week of brexpiprazole dosing yielded more consistent plasma concentrations between EMs and PMs, without exceeding the area under the plasma concentration-time curve observed in the EMs. Taken together, the results of these PBPK simulations suggest that product labeling for brexpiprazole titration in CYP2D6 PMs likely overcompensates for the decreased clearance seen in this population. We propose an alternative dosing strategy that decreases the time to effective concentrations and recommend a reevaluation of steady-state PK in this population to potentially allow for higher daily doses in CYP2D6 PMs.

Effect of lipophilicity on drug distribution and elimination: Influence of obesity.

AIMS: For a given passively-distributed lipophilic drug, the extent of in vivo distribution (pharmacokinetic volume of distribution, Vd ) in obese individuals increases in relation to the degree of obesity. The present study had the objective of evaluating drug distribution in relation to in vitro lipophilicity, and the relative increase in Vd associated with obesity across a series of drugs. METHODS: Cohorts of normal-weight control and obese subjects received single doses of drugs ranging from hydrophilic (acetaminophen, salicylate) to lipophilic (imipramine, verapamil). Lipid solubility was measured by the log-transformed values of the high-pressure liquid chromatographic (HPLC) retention index (Log10 (HPLC)), and the octanol-water partition coefficient (LogP). RESULTS: Among normal-weight controls, Vd normalized for protein binding was highly correlated with Log10 (HPLC) (R2 = .65) and with LogP (R2 = .78). Vd of all drugs was increased in the obese cohort, but the relative increase (compared to controls) for individual drugs was disproportionately greater as lipid solubility increased. Since clearance was unrelated to lipophilicity, the increased Vd produced a parallel disproportionate increase in elimination half-life in the obese cohort that was associated with Log10 (HPLC) (R2 = .62). CONCLUSION: Lipophilicity is a principal correlate of in vivo Vd , as well as the increased Vd of drugs in obese patients. The consequent prolongation of half-life in obesity has clinical safety implications in terms of delayed drug accumulation and washout during and after chronic dosage. The magnitude and importance of this effect for a given drug depends on the degree of obesity, as well as the lipid-solubility of the specific drug.

Germline Genetic Risk Variants for Progressive Multifocal Leukoencephalopathy.

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disorder of the brain caused by reactivation of the JC virus (JCV), a polyomavirus that infects at least 60% of the population but is asymptomatic or results in benign symptoms in most people. PML occurs as a secondary disease in a variety of disorders or as a serious adverse event from immunosuppressant agents, but is mainly found in three groups: HIV-infected patients, patients with hematological malignancies, or multiple sclerosis (MS) patients on the immunosuppressant therapy natalizumab. It is severely debilitating and is deadly in ~50% HIV cases, ~90% of hematological malignancy cases, and ~24% of MS-natalizumab cases. A PML risk prediction test would have clinical utility in all at risk patient groups but would be particularly beneficial in patients considering therapy with immunosuppressant agents known to cause PML, such as natalizumab, rituximab, and others. While a JC antibody test is currently used in the clinical decision process for natalizumab, it is suboptimal because of its low specificity and requirement to periodically retest patients for seroconversion or to assess if a patient's JCV index has increased. Whereas a high specificity genetic risk prediction test comprising host genetic risk variants (i.e., germline variants occurring at higher frequency in PML patients compared to the general population) could be administered one time to provide clinicians with additional risk prediction information that is independent of JCV serostatus. Prior PML case reports support the hypothesis that PML risk is greater in patients with a genetically caused immunodeficiency disorder. To identify germline PML risk variants, we performed exome sequencing on 185 PML cases (70 in a discovery cohort and 115 in a replication cohort) and used the gnomAD variant database for interpretation. Our study yielded 19 rare variants (maximum allele frequency of 0.02 in gnomAD ethnically matched populations) that impact 17 immune function genes (10 are known to cause inborn errors of immunity). Modeling of these variants in a PML genetic risk test for MS patients considering natalizumab treatment indicates that at least a quarter of PML cases may be preventable.

HLA associations with infliximab-induced liver injury.

Biomarkers that are able to identify patients at risk of drug-induced liver injury (DILI) after treatment with infliximab could be important in increasing the safety of infliximab use. We performed a genetic analysis to identify possible human leukocyte antigen (HLA) associations with DILI in European Caucasian users of infliximab in a retrospective study of 16 infliximab-DILI patients and 60 matched controls. In infliximab-associated liver injury, multiple potentially causal individual HLA associations were observed, as well as possible haplotypes. The strongest associated HLA allele was HLA-B*39:01 (P = 0.001; odds ratio [OR] 43.6; 95% confidence interval [CI] 2.8-infinity), which always appeared with another associated allele C*12:03 (P = 0.032; OR 6.1; 95% CI 0.9-47.4). Other associations were observed with HLAs DQB1*02:01 (P = 0.007; OR 5.7; 95% CI 1.4-24.8), DRB1*03:01 (P = 0.012; OR 4.9; 95% CI 1.2-20.5), and B*08:01 (P = 0.048; OR 3.4; 95% CI 0.9-13.2), which also appeared together whenever present in cases. Additional associations were found with HLA-DPB1*10:01 (P = 0.042; OR 20.9; 95% CI 0.7-infinity) and HLA-DRB1*04:04 (P = 0.042; OR 20.9; 95% CI 0.7-infinity). A strong association with HLA-B*39:01 was identified as a potentially causal risk factor for infliximab-induced DILI. Future work should aim to validate this finding and explore possible mechanisms through which the biologic interacts with this particular allele.

Quantitative Method to Track Proteolytic Invasion in 3D Collagen.

Since many tumors are associated with a pronounced collagen-rich stromal reaction, there is increasing interest in understanding mechanisms by which cancer cells invade through the collagen barrier. Here we describe a quantitative method to track cell invasion in 3D collagen I gels. We analyze invasion by quantifying proteolytic tracks generated by invading cancer cells through a 3D collagen microenvironment. We provide a detailed protocol for this quantitative assay, which can be used to characterize signaling pathways that regulate invasion in the 3D microenvironment.

Sustained Impairment of Lurasidone Clearance After Discontinuation of Posaconazole: Impact of Obesity, and Implications for Patient Safety.

PURPOSE/BACKGROUND: The antipsychotic agent lurasidone (Latuda®) is metabolized by Cytochrome P450-3A (CYP3A) enzymes. Coadministration with strong CYP3A inhibitors (such as ketoconazole, posaconazole, and ritonavir) is contraindicated due to the risk of sedation and movement disorders from high levels of lurasidone. This study evaluated the time-course of recovery from the posaconazole drug interaction, and the effect of obesity on the recovery process. METHODS/PROCEDURES: Healthy normal-weight volunteers (n = 11, mean body mass index, BMI, = 23.1 kg/m) and otherwise healthy obese subjects (n = 13, mean BMI = 49.3 kg/m) received single doses of lurasidone in the baseline control condition, again during coadministration of posaconazole, and at 4 additional time points during the 2 weeks after posaconazole discontinuation. FINDINGS/RESULTS: With posaconazole coadministration, lurasidone area under the concentration curve (AUC) increased by an arithmetic mean factor of 6.2 in normals, and by 4.9 in obese subjects. Post-treatment washout of posaconazole was slow in normals (mean half-life 31 hours), and further prolonged in obese subjects (53 hours). Recovery of lurasidone AUC toward baseline was correspondingly slow, and was incomplete. AUC remained significantly elevated above baseline both in normals (factor of 2.1) and obese subjects (factor of 3.4) even at 2 weeks after stopping posaconazole. IMPLICATIONS/CONCLUSIONS: Product labeling does not address the necessary delay after discontinuation of a strong CYP3A inhibitor before lurasidone can be safely administered. We recommend requiring normal-weight and obese patients to limit the dosage of lurasidone, or undergo a washout period, for two and three weeks, respectively, after discontinuation of posaconazole.

Persistence of a Posaconazole-Mediated Drug-Drug Interaction With Ranolazine After Cessation of Posaconazole Administration: Impact of Obesity and Implications for Patient Safety.

The antianginal agent ranolazine (Ranexa®) is metabolized primarily by cytochrome P450-3A (CYP3A) enzymes. Coadministration with strong CYP3A inhibitors, such as ketoconazole and posaconazole, is contraindicated due to risk of QT prolongation from high levels of ranolazine. This study evaluated the time course of recovery from the posaconazole drug interaction in normal-weight and otherwise healthy obese subjects. Subjects received single doses of ranolazine in the baseline control condition, again during coadministration of posaconazole, and at 4 additional time points during the 2 weeks after posaconazole discontinuation. With posaconazole coadministration, the geometric mean ratio of ranolazine area under the concentration curve (AUC) increased by a factor of 3.9 in normals and by 2.8 in obese subjects. Posttreatment washout of posaconazole was slow in normals (mean half-life 36 hours) and further prolonged in obese subjects (64 hours). Recovery of ranolazine AUC toward baseline was delayed. AUC remained significantly elevated above baseline in normal-weight and obese subjects for 7-14 days after stopping posaconazole. Current product labeling does not address the need for delay or a reduced dose of ranolazine after discontinuation of a strong CYP3A inhibitor before ranolazine can be safely administered. We recommend that administration of ranolazine should be limited to 500 mg twice daily for 7 days after posaconazole discontinuation in patients with body mass index 18.5-24.9 kg/m2 and for 12 days in patients with body mass index ≥35 kg/m2 after ranolazine is resumed.

Vortioxetine Disposition in Obesity: Potential Implications for Patient Safety.

BACKGROUND: Obesity and depression are common comorbid conditions. The objective of the study was to evaluate the effect of obesity on the pharmacokinetics of the serotonergic antidepressant vortioxetine. METHODS: Vortioxetine pharmacokinetics were evaluated in 16 otherwise healthy obese volunteers (mean weight, 119 kg; mean body mass index (BMI) 41.8 kg/m) and in 14 normal-weight subjects (mean weight, 68 kg; mean BMI, 23.0 kg/m) matched for age. All subjects received a single 5-mg oral dose of vortioxetine once daily for 29 days. Pre-dose plasma vortioxetine concentrations were measured during the 29 days of dosing, and during a 4-week washout period after the last dose. Full 24-hour profiles were obtained after the first and last doses. RESULTS: Vortioxetine accumulated extensively over the 29 days; the accumulation ratio was not significantly different between obese and control groups (means: 5.24 and 4.46, respectively). Steady-state concentration (Css) and steady-state clearance also did not differ between groups. However mean washout half-life (T1/2) was significantly prolonged in obese vs. control subjects (3.26 days vs. 2.21 days, P < 0.01). Up to 89% of the individual variability in T1/2 was explained by the product of Css and numeric indicators of the degree of obesity. CONCLUSIONS: The half-life of vortioxetine washout after discontinuation of therapy is significantly prolonged in obese individuals compared to normal weight controls. To avoid a potential risk of serotonin syndrome, obese patients who plan to change their medication from vortioxetine to a monoamine oxidase inhibitor (MAOI) should extend the time between vortioxetine discontinuation and MAOI initiation beyond what is recommended in the product label.

Minimal Physiologically Based Pharmacokinetic and Drug-Drug-Disease Interaction Model of Rivaroxaban and Verapamil in Healthy and Renally Impaired Subjects.

Current dosing recommendations for rivaroxaban advocate dosage reduction in patients with moderate to severe renal impairment and avoidance of concomitant strong inhibitors of CYP3A or P-glycoprotein. However, rivaroxaban dosing in patients with mild renal impairment taking concomitant moderate inhibitors of CYP3A and P-glycoprotein is not addressed. To quantify the impacts of concomitant verapamil administration and renal impairment on rivaroxaban pharmacokinetics, a minimal physiologically based pharmacokinetic model system was developed and used to evaluate potential increases in rivaroxaban exposure and the consequent increase in risk of major bleeding. Data from a phase 1, drug-drug interaction study were used to qualify the minimal physiologically based pharmacokinetic model system. Model-based simulations indicate that coadministration of rivaroxaban with verapamil substantially increases rivaroxaban exposure across all renal function categories, resulting in an exponential increase in bleeding risk. Reduction of the daily rivaroxaban dose to 10 to 15 mg reduces the major bleeding risk below the designated 4.5% threshold in the majority of patients with normal or mildly impaired renal function. A reduction to 10 mg daily in patients with moderate to severe renal impairment provides additional risk reduction so that 90% of those patients fall below the 4.5% threshold. A risk threshold of 4.5% was selected because it is the median predicted risk in patients treated concomitantly with ketoconazole, which is contraindicated for use with rivaroxaban. Patients taking both rivaroxaban and verapamil should take a reduced daily dose of rivaroxaban to minimize bleeding risk.

Impaired Rivaroxaban Clearance in Mild Renal Insufficiency With Verapamil Coadministration: Potential Implications for Bleeding Risk and Dose Selection.

Pharmacokinetics and antithrombotic effects of the Factor Xa inhibitor rivaroxaban were studied in subjects with mild renal insufficiency concurrently taking the P-glycoprotein and moderate CYP3A inhibitor verapamil, a drug commonly administered to patients with hypertension, ischemic heart disease, or atrial fibrillation. Age-matched controls with normal renal function were studied concurrently. Subjects' overall mean age was 59 years. Mean creatinine clearance values in the 2 groups were 105 and 71 mL/min. After single 20-mg oral doses, rivaroxaban area under the curve (AUC) was increased by a factor of 1.11 (ratio of geometric means [RGM]) in mild renal insufficiency compared to controls. Verapamil coadministration independently increased AUC to the same extent in both the mild renal insufficiency and control groups (RGM, 1.39 and 1.43). Concurrent mild renal insufficiency and verapamil produced additive inhibition compared to controls without verapamil (RGM, 1.58). Prothrombin time (PT) prolongation and Factor Xa inhibition tracked plasma rivaroxaban, and were enhanced by verapamil. Concentration-response relationships for PT (linear) and Factor Xa inhibition (hyperbolic) were unaffected by renal function or verapamil. The absolute and relative increases in rivaroxaban AUC caused by verapamil in mild renal insufficiency subjects are potentially associated with an increased bleeding risk. Modification of recommended dosage may be required in this combination of circumstances to reduce risk to patients.

Slug inhibits pancreatic cancer initiation by blocking Kras-induced acinar-ductal metaplasia.

Cells in the pancreas that have undergone acinar-ductal metaplasia (ADM) can transform into premalignant cells that can eventually become cancerous. Although the epithelial-mesenchymal transition regulator Snail (Snai1) can cooperate with Kras in acinar cells to enhance ADM development, the contribution of Snail-related protein Slug (Snai2) to ADM development is not known. Thus, transgenic mice expressing Slug and Kras in acinar cells were generated. Surprisingly, Slug attenuated Kras-induced ADM development, ERK1/2 phosphorylation and proliferation. Co-expression of Slug with Kras also attenuated chronic pancreatitis-induced changes in ADM development and fibrosis. In addition, Slug attenuated TGF-α-induced acinar cell metaplasia to ductal structures and TGF-α-induced expression of ductal markers in ex vivo acinar explant cultures. Significantly, blocking the Rho-associated protein kinase ROCK1/2 in the ex vivo cultures induced expression of ductal markers and reversed the effects of Slug by inducing ductal structures. In addition, blocking ROCK1/2 activity in Slug-expressing Kras mice reversed the inhibitory effects of Slug on ADM, ERK1/2 phosphorylation, proliferation and fibrosis. Overall, these results increase our understanding of the role of Slug in ADM, an early event that can eventually lead to pancreatic cancer development.

Interaction of tRNA with MEK2 in pancreatic cancer cells.

Although the translational function of tRNA has long been established, extra translational functions of tRNA are still being discovered. We previously developed a computational method to systematically predict new tRNA-protein complexes and experimentally validated six candidate proteins, including the mitogen-activated protein kinase kinase 2 (MEK2), that interact with tRNA in HEK293T cells. However, consequences of the interaction between tRNA and these proteins remain to be elucidated. Here we tested the consequence of the interaction between tRNA and MEK2 in pancreatic cancer cell lines. We also generated disease and drug resistance-derived MEK2 mutants (Q60P, P128Q, S154F, E207K) to evaluate the function of the tRNA-MEK2 interaction. Our results demonstrate that tRNA interacts with the wild-type and mutant MEK2 in pancreatic cancer cells; furthermore, the MEK2 inhibitor U0126 significantly reduces the tRNA-MEK2 interaction. In addition, tRNA affects the catalytic activity of the wild type and mutant MEK2 proteins in different ways. Overall, our findings demonstrate the interaction of tRNA with MEK2 in pancreatic cancer cells and suggest that tRNA may impact MEK2 activity in cancer cells.

Cancer Cell Invasion in Three-dimensional Collagen Is Regulated Differentially by Gα13 Protein and Discoidin Domain Receptor 1-Par3 Protein Signaling.

Cancer cells can invade in three-dimensional collagen as single cells or as a cohesive group of cells that require coordination of cell-cell junctions and the actin cytoskeleton. To examine the role of Gα13, a G12 family heterotrimeric G protein, in regulating cellular invasion in three-dimensional collagen, we established a novel method to track cell invasion by membrane type 1 matrix metalloproteinase-expressing cancer cells. We show that knockdown of Gα13 decreased membrane type 1 matrix metalloproteinase-driven proteolytic invasion in three-dimensional collagen and enhanced E-cadherin-mediated cell-cell adhesion. E-cadherin knockdown reversed Gα13 siRNA-induced cell-cell adhesion but failed to reverse the effect of Gα13 siRNA on proteolytic invasion. Instead, concurrent knockdown of E-cadherin and Gα13 led to an increased number of single cells rather than groups of cells. Significantly, knockdown of discoidin domain receptor 1 (DDR1), a collagen-binding protein that also co-localizes to cell-cell junctions, reversed the effects of Gα13 knockdown on cell-cell adhesion and proteolytic invasion in three-dimensional collagen. Knockdown of the polarity protein Par3, which can function downstream of DDR1, also reversed the effects of Gα13 knockdown on cell-cell adhesion and proteolytic invasion in three-dimensional collagen. Overall, we show that Gα13 and DDR1-Par3 differentially regulate cell-cell junctions and the actin cytoskeleton to mediate invasion in three-dimensional collagen.

Differential Regulation of ZEB1 and EMT by MAPK-Interacting Protein Kinases (MNK) and eIF4E in Pancreatic Cancer.

UNLABELLED: Human pancreatic ductal adenocarcinoma (PDAC) tumors are associated with dysregulation of mRNA translation. In this report, it is demonstrated that PDAC cells grown in collagen exhibit increased activation of the MAPK-interacting protein kinases (MNK) that mediate eIF4E phosphorylation. Pharmacologic and genetic targeting of MNKs reverse epithelial-mesenchymal transition (EMT), decrease cell migration, and reduce protein expression of the EMT-regulator ZEB1 without affecting ZEB1 mRNA levels. Paradoxically, targeting eIF4E, the best-characterized effector of MNKs, increases ZEB1 mRNA expression through repression of ZEB1-targeting miRNAs, miR-200c and miR-141. In contrast, targeting the MNK effector hnRNPA1, which can function as a translational repressor, increases ZEB1 protein without increasing ZEB1 mRNA levels. Importantly, treatment with MNK inhibitors blocks growth of chemoresistant PDAC cells in collagen and decreases the number of aldehyde dehydrogenase activity-positive (Aldefluor+) cells. Significantly, MNK inhibitors increase E-cadherin mRNA levels and decrease vimentin mRNA levels in human PDAC organoids without affecting ZEB1 mRNA levels. Importantly, MNK inhibitors also decrease growth of human PDAC organoids. IMPLICATIONS: These results demonstrate differential regulation of ZEB1 and EMT by MNKs and eIF4E, and identify MNKs as potential targets in pancreatic cancer.