Frequency, underdiagnosis, and heterogeneity of epidermal growth factor receptor exon 20 insertion mutations using real-world genomic datasets.

Epidermal growth factor receptor (EGFR) exon 20 insertion mutations (ex20ins) account for ≤ 12% of all EGFR-mutant nonsmall cell lung cancers. We analysed real-world datasets to determine the frequency of ex20ins variants, and the ability of polymerase chain reaction (PCR) and next-generation sequencing (NGS) to identify them. Three real-world United States NGS databases were used: GENIE, FoundationInsights, and GuardantINFORM. Mutation profiles consistent with in-frame EGFR ex20ins were summarized. GENIE, FoundationInsights, and GuardantINFORM datasets identified 180, 627, and 627 patients with EGFR ex20ins respectively. The most frequent insertion region of exon 20 was the near loop (~ 70%), followed by the far loop (~ 30%) and the helical (~ 3-6%) regions. GENIE, FoundationInsights, and GuardantINFORM datasets identified 41, 102, and 96 unique variants respectively. An analysis of variants projected that ~ 50% of EGFR ex20ins identified by NGS would have been missed by PCR-based assays. Given the breadth of EGFR ex20ins identified in the real-world US datasets, the ability of PCR to identify these mutations is limited. NGS platforms are more appropriate to identify patients likely to benefit from EGFR ex20ins-targeted therapies.

Prevalence, Treatment Patterns, and Outcomes of Individuals with EGFR Positive Metastatic Non-Small Cell Lung Cancer in a Canadian Real-World Setting: A Comparison of Exon 19 Deletion, L858R, and Exon 20 Insertion EGFR Mutation Carriers.

Real-world evidence surrounding EGFR positive NSCLC patients in Canada is limited. Administrative databases in Alberta, Canada were used to evaluate EGFR testing and mutation prevalence in de novo metastatic NSCLC, as well as the characteristics, treatment patterns, and outcomes of individuals with Exon 19, L858R and Exon20ins mutations. Between 2013-2019, 2974 individuals underwent EGFR testing, of which 451 (15.2%) were EGFR positive. Among EGFR positive individuals, 221 (49.0%) had an Exon 19 mutation, 159 (35.3%) had an L858R mutation, and 18 (4%) had an Exon20ins mutation. The proportion of individuals who initiated 1L systemic therapy was 89.1% for Exon19, 85.5% for L858R, and 72.2% for Exon20ins carriers. The primary front-line systemic therapy was gefitinib or afatinib monotherapy for individuals with Exon 19 (93.4%) and L858R (94.1%) mutations versus platinum combination therapy for individuals with Exon20ins mutations (61.5%). The Exon20ins cohort had worse median overall survival from initiation of 1L systemic therapy (10.5 months [95% CI: 8.0-not estimable]) than the Exon19 (20.6 months [95% CI: 18.4-24.9]), and L858R cohorts (19.1 months [95% CI: 14.5-23.1]). These findings highlight that Exon20ins mutations represent a rare subset of NSCLC in which treatment options are limited and survival outcomes are worse relative to individuals with more common types of EGFR mutations.

A retrospective observational population-based study to assess the prevalence and burden of illness of type 2 diabetes with an estimated glomerular filtration rate < 90 mL/min/1.73 m2 in Ontario, Canada.

AIM: To better understand the healthcare burden of people with type 2 diabetes (T2D) and estimated glomerular filtration rate (eGFR) < 90 mL/min/1.73 m2 in Ontario, Canada. MATERIALS AND METHODS: We used administrative data to evaluate the prevalence of T2D, eGFR < 90 mL/min/1.73 m2 and adverse cardiovascular co-morbidities in individuals aged ≥ 30 years living in Ontario, Canada. We also examined incremental healthcare costs and healthcare resource utilization (HCRU) for these patients with specific incident cardiovascular and renal outcomes, in comparison with controls without these outcomes. RESULTS: While the prevalence of T2D in the general population aged ≥ 30 years in Ontario increased by 1.8% over a 5-year period (2011-2012 to 2015-2016), the prevalence of eGFR < 90 mL/min/1.73 m2 among people with T2D increased by 35%. In comparison with corresponding controls without these outcomes, the per patient average total costs (Canadian dollars) over a 2-year analysis period were higher for patients with cardiovascular disease/chronic kidney disease related death ($69 827; n = 32 407), doubling of serum creatinine ($52 260; n = 22 825), those who started dialysis ($150 627; n = 3499) or received a kidney transplant ($50 664; n = 651). Similarly, HCRU was significantly greater for patients with these incident outcomes. CONCLUSIONS: This real-world retrospective study highlights an increasing prevalence of T2D, eGFR < 90 mL/min/1.73 m2 , and the substantially higher healthcare costs and HCRU when these patients have adverse cardiovascular and renal outcomes. The existence of such a large economic burden underpins the importance of preventing these diabetes-related complications.

CANadian CAnagliflozin REgistry: Patient-Reported Outcomes of Canagliflozin in the Treatment of Type 2 Diabetes Mellitus in Canadian Clinical Practice.

OBJECTIVES: To describe patient-reported outcomes (PROs) after initiation of treatment with canagliflozin (CANA) for type 2 diabetes mellitus (T2DM) in a real-world Canadian setting. METHODS: CANadian CAnagliflozin REgistry (CanCARE) is a prospective, observational, single-arm, real-world Canadian study of the effectiveness and safety of CANA for the treatment of T2DM in 527 subjects. PRO measures were collected in CanCARE using the Current Health Satisfaction Questionnaire (CHES-Q) at baseline and after 3, 6 and 12 months of CANA treatment to examine patient satisfaction regarding weight and overall health. Associations between changes in satisfaction with weight, systolic blood pressure (SBP) and glycated hemoglobin (A1C) levels were also investigated. RESULTS: Proportion of patients satisfied with their body weight and overall health increased from 22.1% and 26.9% at baseline to 32.4% and 49.2% after 12 months of CANA treatment, respectively. Satisfaction rates also increased on CHES-Q domains representing physical and emotional health. Correlations were found between improvement in satisfaction with body weight and weight loss (r=-0.29; p<0.01) and between improvements in satisfaction with overall health and weight loss (r=-0.13; p=0.03) and SBP (r=-0.17; p<0.01), but not with changes in A1C level. CONCLUSIONS: Treatment with CANA is associated with improvements in satisfaction with body weight and overall health, which may be important drivers of patient self-management and hold the potential to positively influence long-term outcomes in T2DM.

CANadian CAnagliflozin REgistry: Effectiveness and safety of canagliflozin in the treatment of type 2 diabetes mellitus in Canadian clinical practice.

AIM: There is limited information concerning the effects of canagliflozin (CANA), a sodium-glucose co-transporter 2 inhibitor (SGLT2i) in a real-world clinical setting in Canada. CanCARE is a 12-month, prospective, observational analysis to demonstrate the effectiveness and safety of CANA in usual clinical practice in Canada. MATERIALS AND METHODS: SGLT2i-naïve adult patients with type 2 diabetes mellitus (T2DM) (n = 527) on a stable antihyperglycemic agent (AHA) regimen with glycated hemoglobin (A1C) ≥ 7%, an estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73m2 , were initiated on CANA as part of their usual treatment approach, and were followed for a period of 12 months. The primary effectiveness objective was the mean change in HbA1c from baseline to 6 and 12 months. RESULTS: Significant improvement from baseline in mean HbA1c levels were observed at 6 months (-0.90%; 95% CI, -1.02, -0.78) and at 12 months (-1.04%; 95% CI, -1.15, -0.92), regardless of duration of diabetes or background AHA treatment regimen. Similarly, significant decreases in systolic blood pressure (-4.65 mm Hg); body weight (-3.24 kg), waist circumference (-2.91 cm) and body mass index (-1.15 kg/m2 ) were observed at 12 months. Additionally, 40.5% of patients achieved the double endpoint (≥0.5% HbA1c reduction and ≥ 3% weight loss), while 24.3% of patients achieved the triple composite endpoint (≥0.5% HbA1c reduction, ≥3% weight loss and ≥ 4 mm Hg systolic blood pressure reduction). No unexpected adverse events were reported. CONCLUSION: CANA provided sustained clinically meaningful improvements in cardiometabolic parameters in this study in a real-world setting, confirming findings from randomized controlled trials.

The adenosine transporter, ENT1, in cardiomyocytes is sensitive to inhibition by ethanol in a kinase-dependent manner: implications for ethanol-dependent cardioprotection and nucleoside analog drug cytotoxicity.

The adenosine transporter 1 (ENT1) transports nucleosides, such as adenosine, and cytotoxic nucleoside analog drugs. ENT1 is well established to play a role in adenosinergic signaling in the cardiovascular system by modulating adenosine levels. Moderate ethanol consumption is cardioprotective and underlying mechanisms of action are not clear although adenosinergic signaling has been implicated. Here, we show that ethanol (5-200 mM) significantly reduces ENT1-dependent [(3)H] 2-chloroadenosine uptake (by up to 27 %) in the cardiomyocyte cell line, HL-1. Inhibition or absence of ENT1 is known to be cardioprotective, suggesting that the interaction of ethanol with ENT1 may promote adenosinergic cardioprotective pathways in the cardiovasculature.Ethanol sensitivity of adenosine uptake is altered by pharmacological activation of PKA and PKC. Primary cardiomyocytes from PKCε-null mice have significantly greater sensitivity to inhibition (by approximately 37 %) of adenosine uptake by ethanol than controls. These data suggest that the presence of ethanol may compromise ENT1-dependent nucleoside analog drug cytotoxicity, and indeed, ethanol (5 mM) reduces the cytotoxic effects of gemcitabine (2 nM), an anti-cancer drug, in the human cancer cell line, HTB2. Thus, the pharmacological inhibition of ENT1 by ethanol may contribute to ethanol-dependent cardioprotection but compromise gemcitabine cytotoxicity.

Absence of equilibrative nucleoside transporter 1 in ENT1 knockout mice leads to altered nucleoside levels following hypoxic challenge.

AIMS: Equilibrative nucleoside transporters (ENT) modulate the flux of adenosine. The ENT1-null (KO) mouse heart is endogenously cardioprotected but the cellular basis of this phenotype is unknown. Therefore, we investigated the cellular mechanisms underlying ENT1-mediated cardioprotection. MAIN METHODS: Circulating adenosine levels were measured in WT and KO mice. Cellular levels of nucleosides and nucleotides were investigated in isolated adult cardiomyocytes from WT and KO mice using HPLC following hypoxic challenge (30 min, 2% O(2)). Changes in hypoxic gene expression were analyzed by PCR arrays and cAMP levels were measured to investigate contributions from adenosine receptors. KEY FINDINGS: Circulating adenosine levels were significantly higher in KO (416±42nmol/l, n=12) compared to WT animals (208±21, n=13, p<0.001). Absence of ENT1 led to an elevated expression of genes involved in cardioprotective pathways compared to WT cardiomyocytes. Following hypoxic challenge, extracellular adenosine levels were significantly elevated in KO (4360±1840 pmol/mg protein) versus WT cardiomyocytes (3035±730 pmol/mg protein, n≥12, p<0.05). This effect was enhanced in the presence of dipyridamole (30 µM), which inhibits ENT1 and ENT2. Enhanced extracellular adenosine levels in ENT1-null cardiomyocytes appeared to come from a pool of extracellular nucleotides including IMP, AMP and ADP. Adenosine receptor (AR) activation mimicked increases in cAMP levels due to hypoxic challenge suggesting that ENT1 modulates AR-dependent signaling. SIGNIFICANCE: ENT1 contributes to modulation of extracellular adenosine levels and subsequent purinergic signaling via ARs. ENT1-null mice possess elevated circulating adenosine levels and reduced cellular uptake resulting in a perpetually cardioprotected phenotype.

Nucleoside transporter expression profiles in human cardiac tissue show striking individual variability with overall predominance of hENT1.

Nucleoside transporters (NTs) are integral membrane transport proteins that modulate the flux of nucleosides such as adenosine across cell membranes. Two families of NTs exist, the concentrative NTs (CNTs, SLC28) and the equilibrative NTs (ENTs, SLC29). CNTs and ENTs transport anti-cancer and anti-viral nucleoside analog drugs and ENTs are also targets of drugs used to treat cardiac pathologies. Levels of some NT profiles have been shown to relate to clinical outcomes in the use of nucleoside analog drugs. However, currently, patient NT profile is not assessed prior to pharmacological administration of analog drugs. Here we describe a reliable method to determine a complete individual NT expression profile from human tissue using quantitative real-time PCR. We developed this assay on tissue (right atrial appendage, left internal mammary, aorta) from individuals undergoing cardiac surgery and compared these findings to the NT expression profiles in pooled whole heart tissue (normal and diseased). Data show that hENT1 is the most abundantly expressed NT, with highest expression levels in the aorta. However, NT expression profiles are highly variable among individuals and changes in NT expression between normal and diseased tissues were observed. These data are the first to describe the RNA expression patterns of all seven NT isoforms in the human heart. The methodology described here may be useful for quantitatively characterizing complete NT expression profiles in any human target tissue.

Characterization of mammalian equilibrative nucleoside transporters (ENTs) by mass spectrometry.

Equilibrative nucleoside transporters (ENTs) are integral membrane proteins that facilitate the movement of nucleosides and hydrophilic nucleoside analog (NA) drugs across cell membranes. ENTs are also targets for cardioprotectant drugs, which block re-uptake of the purine nucleoside adenosine, thereby enhancing purinergic receptor signaling pathways. ENTs are therefore important contributors to drug bioavailability and efficacy. Despite this important clinical role, very little is known about the structure and regulation of ENTs. Biochemical and structural studies on ENT proteins have been limited by their low endogenous expression levels, hydrophobicity and labile nature. To address these issues, we developed an approach whereby tagged mammalian ENT1 protein was over-expressed in mammalian cell lines, confirmed to be functional and isolated by affinity purification to sufficient levels to be analyzed using MALDI-TOF and tandem MS mass spectrometry. This proteomic approach will allow for a more detailed analysis of the structure, function and regulation of ENTs in the future.

Equilibrative nucleoside transporter 1 plays an essential role in cardioprotection.

To better understand the role of equilibrative nucleoside transporters (ENT) in purine nucleoside-dependent physiology of the cardiovascular system, we investigated whether the ENT1-null mouse heart was cardioprotected in response to ischemia (coronary occlusion for 30 min followed by reperfusion for 2 h). We observed that ENT1-null mouse hearts showed significantly less myocardial infarction compared with wild-type littermates. We confirmed that isolated wild-type adult mouse cardiomyocytes express predominantly ENT1, which is primarily responsible for purine nucleoside uptake in these cells. However, ENT1-null cardiomyocytes exhibit severely impaired nucleoside transport and lack ENT1 transcript and protein expression. Adenosine receptor expression profiles and expression levels of ENT2, ENT3, and ENT4 were similar in cardiomyocytes isolated from ENT1-null adult mice compared with cardiomyocytes isolated from wild-type littermates. Moreover, small interfering RNA knockdown of ENT1 in the cardiomyocyte cell line, HL-1, mimics findings in ENT1-null cardiomyocytes. Taken together, our data demonstrate that ENT1 plays an essential role in cardioprotection, most likely due to its effects in modulating purine nucleoside-dependent signaling and that the ENT1-null mouse is a powerful model system for the study of the role of ENTs in the physiology of the cardiomyocyte.

Inosine and equilibrative nucleoside transporter 2 contribute to hypoxic preconditioning in the murine cardiomyocyte HL-1 cell line.

The purine nucleoside adenosine is a physiologically important molecule in the heart. Brief exposure of cardiomyocytes to hypoxic challenge results in the production of extracellular adenosine, which then interacts with adenosine receptors to activate compensatory signaling pathways that lead to cellular resistance to subsequence hypoxic challenge. This phenomenon is known as preconditioning (PC), and, while adenosine is clearly involved, other components of the response are less well understood. Flux of nucleosides, such as adenosine and inosine, across cardiomyocyte membranes is dependent on equilibrative nucleoside transporters 1 and 2 (ENT1 and ENT2). We have previously shown in the murine cardiomyocyte HL-1 cell line that hypoxic challenge leads to an increase in intracellular adenosine, which exits the cell via ENT1 and preconditions via A1 and A3 adenosine receptor-dependent mechanisms. However, the role and contribution of inosine and ENT2 are unclear. In this study, we confirmed that ENT1 and ENT2 are both capable of transporting inosine. Moreover, we found that hypoxic challenge leads to a significant increase in levels of intracellular inosine, which exits the cell via both ENT1 and ENT2. Exogenously added inosine (5 microM) preconditions cardiomyocytes in an A1 adenosine receptor-dependent manner since preconditioning can be blocked by the A1 adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (1 microM) but not the A3 adenosine receptor antagonist MRS-1220 (200 nM). These data suggest that cardiomyocyte responses to hypoxic PC are more complex than previously thought, involving both adenosine and inosine and differing, but overlapping, contributions of the two ENT isoforms.

Physiology of nucleoside transporters: back to the future. . . .

Nucleoside transporters (NTs) are integral membrane proteins responsible for mediating and facilitating the flux of nucleosides and nucleobases across cellular membranes. NTs are also responsible for the uptake of nucleoside analog drugs used in the treatment of cancer and viral infections, and they are the target of certain compounds used in the treatment of some types of cardiovascular disease. The important role of NTs as drug transporters and therapeutic targets has necessarily led to intense interest into their structure and function and the relationship between these proteins and drug efficacy. In contrast, we still know relatively little about the fundamental physiology of NTs. In this review, we discuss various aspects of the physiology of NTs in mammalian systems, particularly noting tissues and cells where there has been little recent research. Our central thesis is reference back to some of the older literature, combined with current findings, will provide direction for future research into NT physiology that will lead to a fuller understanding of the role of these intriguing proteins in the everyday lives of cells, tissues, organs, and whole animals.