Chromatin and transcription factor profiling in rare stem cell populations using CUT&Tag.

Muscle stem cells (MuSCs) are a rare stem cell population that provides myofibers with a remarkable capacity to regenerate after tissue injury. Here, we have adapted the Cleavage Under Target and Tagmentation technology to the mapping of the chromatin landscape and transcription factor binding in 50,000 activated MuSCs isolated from injured mouse hindlimb muscles. We have applied this same approach to human CD34+ hematopoietic stem and progenitor cells. This protocol could be adapted to any rare stem cell population. For complete details on the use and execution of this protocol, please refer to Robinson et al. (2021).

Cardiotoxicity and pro-inflammatory effects of the immune checkpoint inhibitor Pembrolizumab associated to Trastuzumab.

BACKGROUND: The immunotherapy has revolutionized the world of oncology in the last decades with considerable advantages in terms of overall survival in cancer patients. The association of Pembrolizumab and Trastuzumab was recently proposed in clinical trials for the treatment of Trastuzumab-resistant advanced HER2-positive breast cancer. Although immunotherapies are frequently associated with a wide spectrum of immune-related adverse events, the cardiac toxicity has not been properly studied. PURPOSE: We studied, for the first time, the putative cardiotoxic and pro-inflammatory effects of Pembrolizumab associated to Trastuzumab. METHODS: Cell viability, intracellular calcium quantification and pro-inflammatory studies (analyses of the production of Interleukin 1ß, 6 and 8, the expression of NF-kB and Leukotriene B4) were performed in human fetal cardiomyocytes. Preclinical studies were also performed in C57BL6 mice by analyzing fibrosis and inflammation in heart tissues. RESULTS: The combination of Pembrolizumab and Trastuzumab leads to an increase of the intracellular calcium overload (of 3 times compared to untreated cells) and to a reduction of the cardiomyocytes viability (of 65 and 20-25%, compared to untreated and Pembrolizumab or Trastuzumab treated cells, respectively) indicating cardiotoxic effects. Notably, combination therapy increases the inflammation of cardiomyocytes by enhancing the expression of NF-kB and Interleukins. Moreover, in preclinical models, the association of Pembrolizumab and Trastuzumab increases the Interleukins expression of 40-50% compared to the single treatments; the expression of NF-kB and Leukotriene B4 was also increased. CONCLUSION: Pembrolizumab associated to Trastuzumab leads to strong cardiac pro-inflammatory effects mediated by overexpression of NF-kB and Leukotriene B4 related pathways.

Kinin-B2 Receptor Activity in Skeletal Muscle Regeneration and Myoblast Differentiation.

The bioactive peptide bradykinin obtained from cleavage of precursor kininogens activates the kinin-B2 receptor functioning in induction of inflammation and vasodilatation. In addition, bradykinin participates in kidney and cardiovascular development and neuronal and muscle differentiation. Here we show that kinin-B2 receptors are expressed throughout differentiation of murine C2C12 myoblasts into myotubes. An autocrine loop between receptor activation and bradykinin secretion is suggested, since bradykinin secretion is significantly reduced in the presence of the kinin-B2 receptor antagonist HOE-140 during differentiation. Expression of skeletal muscle markers and regenerative capacity were decreased after pharmacological inhibition or genetic ablation of the B2 receptor, while its antagonism increased the number of myoblasts in culture. In summary, the present work reveals to date no functions described for the B2 receptor in muscle regeneration due to the control of proliferation and differentiation of muscle precursor cells.

Anthracycline and trastuzumab-induced cardiotoxicity in breast cancer.

OBJECTIVE: Breast cancer is the most common cancer among women. In the last twenty years early diagnosis, neoadjuvant and adjuvant systemic treatment that targeted to specific molecular targets have significantly reduced the mortality from breast cancer. However, the increase in survival has allowed to observe the cardiotoxic effects of anticancer therapy and increased mortality from cardiovascular causes, resulting in a large literature where experts try to identify the correct management of this critical problem. Even thought the increased attention in this field, many questions have not yet answers and new studies are needed. MATERIALS AND METHODS: We conducted a broad search of the English-language literature in Medline using the following search terms: cardiotoxicity, anthracyclines, trastuzumab, breast cancer, left ventricular dysfunction, heart failure. A manual examination of the articles found has been performed. RESULTS: We provide a comprehensive assessment of the current knowledge about cardiotoxicity induced by anthracycline plus trastuzumab in women affected by breast cancer. CONCLUSIONS: Early identification and prompt treatment of subclinical cardiotoxicity may improve cardiologic prognosis of these patients and may allow oncologists to avoid withdrawal of chemotherapy. That is why it becomes always more important the creation of multidisciplinary teams where cardiologists and oncologists work together to ensure optimal care to oncologic patients treated with cardiotoxic agents.

Body Surface Area and Baseline Blood Pressure Predict Subclinical Anthracycline Cardiotoxicity in Women Treated for Early Breast Cancer.

BACKGROUND AND AIMS: Anthracyclines are highly effective chemotherapeutic agents which may cause long-term cardiac damage (chronic anthracycline cardiotoxicity) and heart failure. The pathogenesis of anthracycline cardiotoxicity remains incompletely understood and individual susceptibility difficult to predict. We sought clinical features which might contribute to improved risk assessment. METHODS: Subjects were women with early breast cancer, free of pre-existing cardiac disease. Left ventricular ejection fraction was measured using cardiovascular magnetic resonance before and >12 months after anthracycline-based chemotherapy (>3 months post-Trastuzumab). Variables associated with subclinical cardiotoxicity (defined as a fall in left ventricular ejection fraction of ≥5%) were identified by logistic regression. RESULTS: One hundred and sixty-five women (mean age 48.3 years at enrollment) completed the study 21.7 months [IQR 18.0-26.8] after starting chemotherapy. All received anthracyclines (98.8% epirubicin, cumulative dose 400 [300-450] mg/m2); 18% Trastuzumab. Baseline blood pressure was elevated (≥140/90mmHg, mean 147.3/86.1mmHg) in 18 subjects. Thirty-four subjects (20.7%) were identified with subclinical cardiotoxicity, independent predictors of which were the number of anthracycline cycles (odds ratio, OR 1.64 [1.17-2.30] per cycle), blood pressure ≥140/90mmHg (OR 5.36 [1.73-17.61]), body surface area (OR 2.08 [1.36-3.20] per standard deviation (0.16m2) increase), and Trastuzumab therapy (OR 3.35 [1.18-9.51]). The resultant predictive-model had an area under the receiver operating characteristics curve of 0.78 [0.70-0.86]. CONCLUSIONS: We found subclinical cardiotoxicity to be common even within this low risk cohort. Risk of cardiotoxicity was associated with modestly elevated baseline blood pressure-indicating that close attention should be paid to blood pressure in patients considered for anthracycline based chemotherapy. The association with higher body surface area suggests that indexing of anthracycline doses to surface area may not be appropriate for all, and points to the need for additional research in this area.

Mechanisms of Action and Reduced Cardiotoxicity of Pixantrone; a Topoisomerase II Targeting Agent with Cellular Selectivity for the Topoisomerase IIα Isoform.

Pixantrone is a new noncardiotoxic aza-anthracenedione anticancer drug structurally related to anthracyclines and anthracenediones, such as doxorubicin and mitoxantrone. Pixantrone is approved in the European Union for the treatment of relapsed or refractory aggressive B cell non-Hodgkin lymphoma. This study was undertaken to investigate both the mechanism(s) of its anticancer activity and its relative lack of cardiotoxicity. Pixantrone targeted DNA topoisomerase IIα as evidenced by its ability to inhibit kinetoplast DNA decatenation; to produce linear double-strand DNA in a pBR322 DNA cleavage assay; to produce DNA double-strand breaks in a cellular phospho-histone γH2AX assay; to form covalent topoisomerase II-DNA complexes in a cellular immunodetection of complex of enzyme-to-DNA assay; and to display cross-resistance in etoposide-resistant K562 cells. Pixantrone produced semiquinone free radicals in an enzymatic reducing system, although not in a cellular system, most likely due to low cellular uptake. Pixantrone was 10- to 12-fold less damaging to neonatal rat myocytes than doxorubicin or mitoxantrone, as measured by lactate dehydrogenase release. Three factors potentially contribute to the reduced cardiotoxicity of pixantrone. First, its lack of binding to iron(III) makes it unable to induce iron-based oxidative stress. Second, its low cellular uptake may limit its ability to produce semiquinone free radicals and redox cycle. Finally, because the ß isoform of topoisomerase II predominates in postmitotic cardiomyocytes, and pixantrone is demonstrated in this study to be selective for topoisomerase IIα in stabilizing enzyme-DNA covalent complexes, the attenuated cardiotoxicity of this agent may also be due to its selectivity for targeting topoisomerase IIα over topoisomerase IIß.

Equivalence Ratio for Daunorubicin to Doxorubicin in Relation to Late Heart Failure in Survivors of Childhood Cancer.

PURPOSE: Cumulative anthracycline dose is one of the strongest predictors of heart failure (HF) after cancer treatment. However, the differential risk for cardiotoxicity between daunorubicin and doxorubicin has not been rigorously evaluated among survivors of childhood cancer. These risks, which are based on hematologic toxicity, are currently assumed to be approximately equivalent. PATIENTS AND METHODS: Data from 15,815 survivors of childhood cancer who survived at least 5 years were used. Survivors were from the Emma Children's Hospital/Academic Medical Center (n = 1,349), the National Wilms Tumor Study (n = 364), the St Jude Lifetime Cohort Study (n = 1,695), and the Childhood Cancer Survivor Study (n = 12,407). The hazard ratio (HR) for clinical HF through age 40 years for doses of daunorubicin and doxorubicin (per 100-mg/m(2) increments) was estimated by using Cox regression adjusted for sex, age at diagnosis, treatment with other anthracycline agents and chest radiation, and cohort membership. RESULTS: In total, 5,144 (32.5%) patients received doxorubicin as part of their cancer treatment, whereas 2,243 (14.7%) received daunorubicin. On the basis of 271 occurrences of HF during a median follow-up time after cohort entry of 17.3 years (range, 0.0 to 35.0 years), the cumulative incidence of HF at age 40 years was 3.2% (95% CI, 2.8% to 3.7%). The average ratio of HRs for daunorubicin to doxorubicin was 0.45 (95% CI, 0.23 to 0.73). A similar ratio was obtained by using a linear dose-response model, which yielded an HR of 0.49 (95% CI, 0.28 to 0.70). CONCLUSION: Compared with doxorubicin, daunorubicin was less cardiotoxic among survivors of childhood cancer than most current guidelines suggest. This may have implications for follow-up guidelines. The feasibility of substitution of doxorubicin with daunorubicin in childhood cancer treatment protocols to reduce cardiotoxicity should be additionally investigated.

Administration of DNA Encoding the Interleukin-27 Gene Augments Antitumour Responses through Non-adaptive Immunity.

DNA-mediated immunization of a tumour antigen is a possible immunotherapy for cancer, and interleukin (IL)-27 has diverse functions in adaptive immunity. In this study, we examined whether IL-27 DNA administration enhanced antitumour effects in mice vaccinated with DNA encoding a putative tumour antigen, ß-galactosidase (ß-gal). An intramuscular injection of cardiotoxin before DNA administration facilitated the exogenous gene expression. In mice received ß-gal and IL-27 DNA, growth of ß-gal-positive P815 tumours was retarded and survival of the mice was prolonged. Development of ß-gal-positive Colon 26 tumours was suppressed by vaccination of ß-gal DNA and further inhibited by additional IL-27 DNA administration or IL-12 family cytokines. Nevertheless, a population of ß-gal-specific CD8(+) T cells did not increase, and production of anti-ß-gal antibody was not enhanced by IL-27 DNA administration. Spleen cells from mice bearing IL-27-expressing Colon 26 tumours showed greater YAC-1-targeted cytotoxicity although CD3(-)/DX5(+) natural killer (NK) cell numbers remained unchanged. Recombinant IL-27 enhanced YAC-1-targeted cytotoxicity of IL-2-primed splenic NK cells and augmented a phosphorylation of signal transducer and activator of transcription 3 and an expression of perforin. These data collectively indicate that IL-27 DNA administration activates NK cells and augments vaccination effects of DNA encoding a tumour antigen through non-adaptive immune responses.

Establishment of a new anal sphincter injury model in rats based on cardiotoxin.

BACKGROUND/PURPOSE: Mainstream models for anal sphincter injury use large animals. We developed a simple and stable anal sphincter injury model in a small animal (i.e., rats) to obtain manometry measurements by using a miniaturized probe and applying cardiotoxin. METHODS: The histological structure of the anal canal was evaluated by using manometry in normal rats (n=40). We damaged the internal and external anal sphincters by locally administering snake poison (cardiotoxin; 20 uM, 100µL 8 points). We evaluated the anal canal function through manometry measurements (n=5) and examined the histology using hematoxylin-eosin staining (at each time point, n=3; total n=15). RESULTS: The manometry parameters and structure of the anal canal of normal rats were similar to those of humans, because rats have resting pressure, rectoanal reflex in the manometry, and an external and internal anal sphincter. After inducing injury, the following findings were observed: rhythmic wave loss and a remarkable reduction in the anal sphincter resting pressure; and local bleeding and advanced infiltration of the inflammatory cells (day 1) and the loss of muscle fibers (day 3). CONCLUSION: This new rat model will contribute to increasing the knowledge on the anal canal.

Physical exercise prior and during treatment reduces sub-chronic doxorubicin-induced mitochondrial toxicity and oxidative stress.

Doxorubicin (DOX) is an anti-cancer agent whose clinical usage results in a cumulative and dose-dependent cardiotoxicity. We have previously shown that exercise performed prior to DOX treatment reduces the resulting cardiac(mito) toxicity. We sought to determine the effects on cardiac mitochondrial toxicity of two distinct chronic exercise models (endurance treadmill training-TM and voluntary free-wheel activity-FW) when used prior and during DOX treatment. Male-young Sprague-Dawley rats were divided into six groups (n=6 per group): SAL+SED (saline sedentary), SAL+TM (12-weeks TM), SAL+FW (12-weeks FW), DOX+SED (7-weeks of chronic DOX treatment 2mg/kg per week), DOX+TM and DOX+FW. DOX administration started 5weeks after the beginning of the exercise protocol. Heart mitochondrial ultrastructural alterations, mitochondrial function (oxygen consumption and membrane potential), semi-quantification of oxidative phosphorylation (OXPHOS) proteins and their in-gel activity, as well as proteins involved in mitochondrial oxidative stress (SIRT3, p66shc and UCP2), biogenesis (PGC1α and TFAM), acetylation and markers for oxidative damage (carbonyl groups, MDA,SH, aconitase, Mn-SOD activity) were evaluated. DOX treatment resulted in ultrastructural and functional alterations and decreased OXPHOS. Moreover, DOX decreased complex I activity and content, mitochondrial biogenesis (TFAM), increased acetylation and oxidative stress. TM and FW prevented DOX-induced alteration in OXPHOS, the increase in oxidative stress, the decrease in complex V activity and in complex I activity and content. DOX-induced decreases in TFAM and SIRT3 content were prevented by TM only. Both chronic models of physical exercise performed before and during the course of sub-chronic DOX treatment translated into an improved mitochondrial bioenergetic fitness, which may result in part from the prevention of mitochondrial oxidative stress and damage.

Dexrazoxane exposure and risk of secondary acute myeloid leukemia in pediatric oncology patients.

BACKGROUND: Dexrazoxane may reduce anthracycline-associated cardiotoxicity in pediatric cancer patients. However, concerns of secondary acute myeloid leukemia (AML) have led to restrictions on pediatric dexrazoxane use in Europe. Published data about dexrazoxane-associated secondary AML are limited and conflicting. We sought to estimate the secondary AML risk in children receiving dexrazoxane after anthracycline exposure. PROCEDURE: A retrospective cohort of children with newly identified malignancies (excluding AML) receiving anthracyclines between January 1, 1999 and March 31, 2011 was established using the Pediatric Health Information System (PHIS). Patients were followed for all subsequent admissions to identify dexrazoxane exposures and secondary AML, defined by AML ICD-9 codes and AML induction chemotherapy. Logistic regression was used to model the association of dexrazoxane and secondary AML risk. A propensity score was used to adjust for measurable confounding. RESULTS: Of 15,532 patients in the cohort exposed to anthracyclines, 1,406 received dexrazoxane. The secondary AML rate was 0.21% (3 of 1,046) in dexrazoxane-exposed and 0.55% (77 of 14,126) in unexposed patients. In a propensity score-adjusted multivariate analysis, dexrazoxane exposure was not associated with an increased risk of secondary AML, OR = 0.38, 95% CI 0.11-1.26. CONCLUSIONS: Dexrazoxane was not associated with an increased risk of secondary AML in a large cohort of pediatric cancer patients receiving anthracyclines in US hospitals. While these data support dexrazoxane's safety in the general pediatric oncology population, additional studies are needed to confirm these findings and to quantify dexrazoxane's long-term cardioprotective effects.

Doublecortin marks a new population of transiently amplifying muscle progenitor cells and is required for myofiber maturation during skeletal muscle regeneration.

Muscle satellite cells are indispensable for muscle regeneration, but the functional diversity of their daughter cells is unknown. Here, we show that many Pax7(+)MyoD(-) cells locate both beneath and outside the basal lamina during myofiber maturation. A large majority of these Pax7(+)MyoD(-) cells are not self-renewed satellite cells, but have different potentials for both proliferation and differentiation from Pax7(+)MyoD(+) myoblasts (classical daughter cells), and are specifically marked by expression of the doublecortin (Dcx) gene. Transplantation and lineage-tracing experiments demonstrated that Dcx-expressing cells originate from quiescent satellite cells and that the microenvironment induces Dcx in myoblasts. Expression of Dcx seems to be necessary for myofiber maturation because Dcx-deficient mice exhibited impaired myofiber maturation resulting from a decrease in the number of myonuclei. Furthermore, in vitro and in vivo studies suggest that one function of Dcx in myogenic cells is acceleration of cell motility. These results indicate that Dcx is a new marker for the Pax7(+)MyoD(-) subpopulation, which contributes to myofiber maturation during muscle regeneration.

Tissue LyC6- macrophages are generated in the absence of circulating LyC6- monocytes and Nur77 in a model of muscle regeneration.

There are several open questions regarding the origin, development, and differentiation of subpopulations of monocytes, macrophages (MFs), and dendritic cells. It is a particularly intriguing question how circulating monocyte subsets develop and contribute to the generation of steady-state and inflammatory tissue MF pools and which transcriptional mechanisms contribute to these processes. In this study, we took advantage of a genetic model in which LyC6(-) circulating monocyte development is severely diminished due to the lack of the nuclear receptor, NUR77. We show that, in a mouse model of skeletal muscle injury and regeneration, the accumulation of leukocytes and the generation of LyC6(+) and LyC6(-) MF pools are intact in the absence of circulating LyC6(-) blood monocytes. These data suggest that NUR77, which is required for LyC6(-) blood monocyte development, is expressed but not critically required for LyC6(+) to LyC6(-) tissue MF specification. Moreover, these observations support a model according to which tissue macrophage subtype specification is distinct from that of circulating monocytes. Lastly, our data show that in the used sterile inflammation model tissue LyC6(-) MFs are derived from LyC6(+) cells.

Delayed bupropion cardiotoxicity associated with elevated serum concentrations of bupropion but not hydroxybupropion.

CONTEXT: Bupropion overdose commonly causes generalized seizures and central nervous system depression. Less commonly, cardiotoxicity has been reported. The toxicity of the parent drug compared to its active metabolite hydroxybupropion is uncertain. CASE DETAILS: A 31-year-old man presented to the emergency department with altered mental status after an intentional overdose of bupropion. Three hours after admission he developed status epilepticus requiring intubation, and 13 h after admission he developed marked widening of the QRS complex and prolongation of the QTc interval. Serial serum bupropion levels peaked with the onset of cardiotoxicity (334 ng/mL) and fell into the therapeutic range within 24 h, which coincided with normalization of his ECG intervals. Levels of the metabolite hydroxybupropion peaked later (4302 ng/mL) and remained elevated even after neurological and cardiotoxic symptoms resolved. DISCUSSION: Cardiotoxicity appears to be caused primarily by bupropion rather than its active metabolite hydroxybupropion.

Cardiotoxicity and apoptotic activity in subacute endosulfan toxicity and the protective effect of vitamin C in rabbits: a pathological study.

Cardiovascular disease is one of the most significant causes of mortality in humans and animals, and its etiology is usually unknown. The aim of this study was to investigate the cardiac pathology of endosulfan toxicity and the protective effect of vitamin C in rabbits. Twenty-four rabbits were divided into 4 groups: (1) the END group was given a daily sublethal dose of endosulfan in corn oil by oral gavage for 6 weeks; (2) the END + C group received the endosulfan as well as vitamin C over the same 6-week period; (3) the OIL + C group received corn oil daily and vitamin C every other day; and (4) the OIL group received only corn oil daily. We observed microscopic hemorrhages, single-cell necrosis, inflammatory reactions, and fibrotic changes in the myocardium in the END group. Small hemorrhages and single-cell necrosis also were seen in some hearts in the END + C group, but no inflammation was observed. Caspase-3 immunoreactivity was more significant in myocardial cells in the END group compared with the others. A protective effect of vitamin C on lesions was observed in the END + C group. These results showed that endosulfan resulted in toxic changes in the hearts of rabbits, but this toxicity could be decreased with vitamin C treatment.

Exercise mitigates cardiac doxorubicin accumulation and preserves function in the rat.

PURPOSE: Doxorubicin (DOX) is an effective antineoplastic agent with well-characterized cardiotoxic effects. Although exercise has been shown to protect against DOX cardiotoxicity, a clear and concise mechanism to explain its cardioprotective effects is lacking. The purpose of this study was to determine if exercise training reduces cardiac DOX accumulation, thereby providing a possible mechanism to explain the cardioprotective effects of exercise against DOX toxicity. METHODS: Sprague-Dawley rats were randomly assigned to 1 of 3 primary experimental groups: sedentary (n = 77), wheel running (n = 65), or treadmill (n = 65). Animals in wheel running and treadmill groups completed 10 weeks of exercise before DOX treatment. DOX was administered 24 hours after the last training session as a bolus intraperitoneal injection at 10 mg/kg. Subgroups of rats from each primary group were killed at 1, 3, 5, 7, and 9 days after DOX exposure to assess cardiac function and DOX accumulation. RESULTS: Ten weeks of exercise preconditioning reduced myocardial DOX accumulation, and this reduction in accumulation was associated with preserved cardiac function. CONCLUSIONS: These data suggest that the cardioprotective effects of exercise against DOX-induced injury may be due, in part, to a reduction in myocardial DOX accumulation.

A novel self-assembly albumin nanocarrier for reducing doxorubicin-mediated cardiotoxicity.

Doxorubicin is an antitumor drug commonly used against a wide spectrum of tumors. However, the clinical application of DOX is restricted by its cardiotoxicity. To reduce the cardiotoxicity, we develop an albumin-based nanocarrier via a new molecular switch method for DOX delivery. Spherically shaped DOX-loaded HSA nanoparticles (NPs-DOX) are prepared with a drug-loading capacity and particle size of 4.3% and 120.1 ± 26 nm, respectively. In vivo studies demonstrate that NPs-DOX is able to preferentially accumulate in tumor and show great tumor inhibition on H22 hepatocellular-carcinoma-bearing mice. As for the toxicity, compared with free DOX, the maximum tolerated dose of NPs-DOX is increased from 10 to over 30 mg/kg, indicating the reduced systematic toxicity. More importantly, the cardiotoxicity induced by NPs-DOX is also significantly reduced because both left ventricular ejection fraction and left ventricular fractional shortening are almost not changed and other cardiotoxicity markers such as serum creatine kinase-MB, lactate dehydrogenase, superoxide dismutase, and malonaldehyde are kept constant. The reduced cardiotoxicity of NPs-DOX is also confirmed by nonhistological changes in the heart tissue. Therefore, such albumin-based nanocarrier can be one of the most promising strategies for the delivery of DOX.

Validation of variants in SLC28A3 and UGT1A6 as genetic markers predictive of anthracycline-induced cardiotoxicity in children.

BACKGROUND: The use of anthracyclines as effective antineoplastic drugs is limited by the occurrence of cardiotoxicity. Multiple genetic variants predictive of anthracycline-induced cardiotoxicity (ACT) in children were recently identified. The current study was aimed to assess replication of these findings in an independent cohort of children. PROCEDURE: . Twenty-three variants were tested for association with ACT in an independent cohort of 218 patients. Predictive models including genetic and clinical risk factors were constructed in the original cohort and assessed in the current replication cohort. RESULTS: . We confirmed the association of rs17863783 in UGT1A6 and ACT in the replication cohort (P = 0.0062, odds ratio (OR) 7.98). Additional evidence for association of rs7853758 (P = 0.058, OR 0.46) and rs885004 (P = 0.058, OR 0.42) in SLC28A3 was found (combined P = 1.6 × 10(-5) and P = 3.0 × 10(-5), respectively). A previously constructed prediction model did not significantly improve risk prediction in the replication cohort over clinical factors alone. However, an improved prediction model constructed using replicated genetic variants as well as clinical factors discriminated significantly better between cases and controls than clinical factors alone in both original (AUC 0.77 vs. 0.68, P = 0.0031) and replication cohort (AUC 0.77 vs. 0.69, P = 0.060). CONCLUSIONS: . We validated genetic variants in two genes predictive of ACT in an independent cohort. A prediction model combining replicated genetic variants as well as clinical risk factors might be able to identify high- and low-risk patients who could benefit from alternative treatment options.