The Potential of the Fibronectin Inhibitor Arg-Gly-Asp-Ser in the Development of Therapies for Glioblastoma.

Glioblastoma (GBM) is the most lethal and common malignant primary brain tumor in adults. An important feature that supports GBM aggressiveness is the unique composition of its extracellular matrix (ECM). Particularly, fibronectin plays an important role in cancer cell adhesion, differentiation, proliferation, and chemoresistance. Thus, herein, a hydrogel with mechanical properties compatible with the brain and the ability to disrupt the dynamic and reciprocal interaction between fibronectin and tumor cells was produced. High-molecular-weight hyaluronic acid (HMW-HA) functionalized with the inhibitory fibronectin peptide Arg-Gly-Asp-Ser (RGDS) was used to produce the polymeric matrix. Liposomes encapsulating doxorubicin (DOX) were also included in the hydrogel to kill GBM cells. The resulting hydrogel containing liposomes with therapeutic DOX concentrations presented rheological properties like a healthy brain. In vitro assays demonstrated that unmodified HMW-HA hydrogels only caused GBM cell killing after DOX incorporation. Conversely, RGDS-functionalized hydrogels displayed per se cytotoxicity. As GBM cells produce several proteolytic enzymes capable of disrupting the peptide-HA bond, we selected MMP-2 to illustrate this phenomenon. Therefore, RGDS internalization can induce GBM cell apoptosis. Importantly, RGDS-functionalized hydrogel incorporating DOX efficiently damaged GBM cells without affecting astrocyte viability, proving its safety. Overall, the results demonstrate the potential of the RGDS-functionalized hydrogel to develop safe and effective GBM treatments.

Relevance of HOTAIR rs920778 and rs12826786 Genetic Variants in Bladder Cancer Risk and Survival.

The long non-coding RNA HOX transcript antisense intergenic RNA (HOTAIR) is associated with oncogenic features in bladder cancer and is predictive of poor clinical outcomes in patients diagnosed with this disease. In this study, we evaluated the impact of the HOTAIR single nucleotide polymorphisms rs920778 and rs12826786 on bladder cancer risk and survival. This case-control study included 106 bladder cancer patients and 199 cancer-free controls. Polymorphisms were evaluated through PCR-restriction fragment length polymorphism. The odds ratio and 95% confidence intervals were tested using univariable and multivariable logistic regressions. The effects on patient survival were evaluated using the log-rank test and Cox regression models. Our data showed that the HOTAIR rs920778 and rs12826786 genetic variants are not associated with the risk of developing bladder cancer. Nevertheless, survival analyses suggested that the HOTAIR rs920778 TT genotype and rs12826786 CC genotype are associated with increased survival in male bladder cancer patients and in patients, both male and female, who have primary tumors with a pathological stage of pT2. Together, these results suggest that, despite not being associated with bladder cancer risk, HOTAIR rs920778 and rs12826786 polymorphisms might represent new prognostic factors in this type of cancer. This is particularly important as these polymorphisms might be easily evaluated in bladder cancer patients in a minimally invasive manner to better predict their clinical outcomes.

Epigenetically-regulated miR-30a/c-5p directly target TWF1 and hamper ccRCC cell aggressiveness.

Clear cell renal cell carcinoma (ccRCC) is highly prone to metastasize and displays an extremely low 5-year survival rate. Not only miRNAs (miRs) are key gene expression regulators but can also be epigenetically modified. Abnormal miR expression has been linked with epithelial-mesenchymal transition (EMT)-driven ccRCC progression. MiR-30a/c-5p were found downregulated in ccRCC and associated with aggressiveness. Herein, we sought to unravel miR-30a/c-5p mechanistic role in ccRCC. RNA sequencing and genome-wide methylome data of ccRCC and normal tissue samples from The Cancer Genome Atlas database were integrated to identify candidate miRs cytosine-phosphate-guanine (CpG) loci deregulated in ccRCC. TargetScan was searched to identify miR putative targets. MiR-30a/c-5p expression and promoter methylation was evaluated in vitro, by PCR. Western blot, functional and luciferase assays were performed after cell transfection with either pre-miR, antimiR, or siRNA against twinfilin-1 (TWF1). Immunohistochemistry (IHC) was performed in ccRCC tissues. We found miR-30c-5p downregulation and aberrant promoter methylation in ccRCC tissues. In vitro studies revealed concomitant miR-30a/c-5p downregulation and increased promoter methylation, as well as a significant re-expression following decitabine treatment. Functional assays demonstrated that both miRs significantly decreased cell aggressiveness and the protein levels of EMT-promoting players, while upregulating epithelial markers, namely Claudin-1 and ZO-1. Importantly, we confirmed TWF1 as a direct target of both miRs, and its potential involvement in epithelial-mesenchymal transition/mesenchymal-epithelial transition regulation. IHC analysis revealed higher TWF1 expression in primary tissues from patients that developed metastases, after surgical treatment. Our results implicate miR-30a/c-5p in ccRCC cells' aggressiveness attenuation by directly targeting TWF1 and hampering EMT.

Chronic Stress Does Not Influence the Survival of Mouse Models of Glioblastoma.

The existence of a clear association between stress and cancer is still a matter of debate. Recent studies suggest that chronic stress is associated with some cancer types and may influence tumor initiation and patient prognosis, but its role in brain tumors is not known. Glioblastoma (GBM) is a highly malignant primary brain cancer, for which effective treatments do not exist. Understanding how chronic stress, or its effector hormones glucocorticoids (GCs), may modulate GBM aggressiveness is of great importance. To address this, we used both syngeneic and xenograft in vivo orthotopic mouse models of GBM, in immunocompetent C57BL/6J or immunodeficient NSG mice, respectively, to evaluate how different paradigms of stress exposure could influence GBM aggressiveness and animals' overall survival (OS). Our results demonstrated that a previous exposure to exogenous corticosterone administration, chronic restraint stress, or chronic unpredictable stress do not impact the OS of these mice models of GBM. Concordantly, ex vivo analyses of various GBM-relevant genes showed similar intra-tumor expression levels across all experimental groups. These findings suggest that corticosterone and chronic stress do not significantly affect GBM aggressiveness in murine models.

Cadherin switches during epithelial-mesenchymal transition: CDH4/RCAD downregulation reduces bladder cancer progression.

PURPOSE: Non-muscle invasive bladder cancer (NMIBC) is a highly recurrent disease that progresses to muscle-invasive bladder cancer (MIBC) in 5-25% of the cases. Epithelial-mesenchymal transition (EMT) has been associated with features of disease progression. Thus, we aimed to characterize the cadherin switch (CS), an EMT hallmark, and its regulatory mechanisms in bladder cancer (BlCa) progression, as well as the biological role of RCAD, a lesser-known cadherin, in bladder carcinogenesis. METHODS: Cadherin mRNA and promoter methylation levels were retrieved from The Cancer Genome Atlas (TCGA). Validation was performed in an independent set of 121 primary BlCa (NMIBC and MIBC) and 40 normal bladder samples from IPO Porto, using RT-qPCR and qMSP. Immunohistochemistry was performed in these samples and in 14 additional sarcomatoid BlCa. CRISPR-Cas9 was performed to explore the potential in vitro impact of RCAD on BlCa cell migration and invasion. RESULTS: In both the TCGA and IPO Porto BlCa cohorts, cadherin gene deregulation was observed compared to normal tissue samples, independent of promoter methylation. At the protein level, decreased E-cadherin and increased P- and R-cadherin expression was noted in BlCa tissues. In sarcomatoid BlCa the same trend was observed, with a more intense staining compared to that in conventional MIBCs. RCAD knockout considerably reduced the malignant properties of BlCa cells. CONCLUSIONS: Our data indicate that E-, P- and R-cadherin switches occur in BlCa, being associated with tumor progression. Promoter methylation is not the likely mechanism underlying cadherin expression deregulation. Our findings suggest an oncogenic role of RCAD in BlCa progression.

Bringing vascularization into glioblastoma in vitro models.

Tumor blood vessels create optimal conditions for glioblastoma (GBM) growth and therapy resistance. Therefore, tissue engineering techniques evolved towards allowing its inclusion in preclinical in vitro GBM models. In comparison with conventional ones, less representative of tumor biology, these new tools might significantly improve GBM treatment, contributing to a higher throughput screening in drug research and to the clinical translation of these therapies.

Plexin-A4 Mediates Cytotoxic T-cell Trafficking and Exclusion in Cancer.

Cytotoxic T cell (CTL) infiltration of the tumor carries the potential to limit cancer progression, but their exclusion by the immunosuppressive tumor microenvironment hampers the efficiency of immunotherapy. Here, we show that expression of the axon guidance molecule Plexin-A4 (Plxna4) in CTLs, especially in effector/memory CD8+ T cells, is induced upon T-cell activation, sustained in the circulation, but reduced when entering the tumor bed. Therefore, we deleted Plxna4 and observed that Plxna4-deficient CTLs acquired improved homing capacity to the lymph nodes and to the tumor, as well as increased proliferation, both achieved through enhanced Rac1 activation. Mice with stromal or hematopoietic Plxna4 deletion exhibited enhanced CTL infiltration and impaired tumor growth. In a melanoma model, adoptive transfer of CTLs lacking Plxna4 prolonged survival and improved therapeutic outcome, which was even stronger when combined with anti-programmed cell death protein 1 (PD-1) treatment. PLXNA4 abundance in circulating CTLs was augmented in melanoma patients versus healthy volunteers but decreased after the first cycle of anti-PD-1, alone or in combination with anti-cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4), in those patients showing complete or partial response to the treatment. Altogether, our data suggest that Plxna4 acts as a "checkpoint," negatively regulating CTL migration and proliferation through cell-autonomous mechanisms independent of the interaction with host-derived Plxna4 ligands, semaphorins. These findings pave the way toward Plxna4-centric immunotherapies and propose Plxna4 detection in circulating CTLs as a potential way to monitor the response to immune checkpoint blockade in patients with metastatic melanoma.

Cadherin-3 is a novel oncogenic biomarker with prognostic value in glioblastoma.

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. The prognosis of patients is very poor, with a median overall survival of ~ 15 months after diagnosis. Cadherin-3 (also known as P-cadherin), a cell-cell adhesion molecule encoded by the CDH3 gene, is deregulated in several cancer types, but its relevance in GBM is unknown. In this study, we investigated the functional roles, the associated molecular signatures, and the prognostic value of CDH3/P-cadherin in this highly malignant brain tumor. CDH3/P-cadherin mRNA and protein levels were evaluated in human glioma samples. Knockdown and overexpression models of P-cadherin in GBM were used to evaluate its functional role in vitro and in vivo. CDH3-associated gene signatures were identified by enrichment analyses and correlations. The impact of CDH3 in the survival of GBM patients was assessed in independent cohorts using both univariable and multivariable models. We found that P-cadherin protein is expressed in a subset of gliomas, with an increased percentage of positive samples in grade IV tumors. Concordantly, CDH3 mRNA levels in glioma samples from The Cancer Genome Atlas (TCGA) database are increased in high-grade gliomas. P-cadherin displays oncogenic functions in multiple knockdown and overexpression GBM cell models by affecting cell viability, cell cycle, cell invasion, migration, and neurosphere formation capacity. Genes that were positively correlated with CDH3 are enriched for oncogenic pathways commonly activated in GBM. In vivo, GBM cells expressing high levels of P-cadherin generate larger subcutaneous tumors and cause shorter survival of mice in an orthotopic intracranial model. Concomitantly, high CDH3 expression is predictive of shorter overall survival of GBM patients in independent cohorts. Together, our results show that CDH3/P-cadherin expression is associated with aggressiveness features of GBM and poor patient prognosis, suggesting that it may be a novel therapeutic target for this deadly brain tumor.

MCT1 Is a New Prognostic Biomarker and Its Therapeutic Inhibition Boosts Response to Temozolomide in Human Glioblastoma.

Background: Glioblastomas (GBMs) present remarkable metabolism reprograming, in which many cells display the "Warburg effect", with the production of high levels of lactate that are extruded to the tumour microenvironment by monocarboxylate transporters (MCTs). We described previously that MCT1 is up-regulated in human GBM samples, and MCT1 inhibition decreases glioma cell viability and aggressiveness. In the present study, we aimed to unveil the role of MCT1 in GBM prognosis and to explore it as a target for GBM therapy in vivo. Methods: MCT1 activity and protein expression were inhibited by AR-C155858 and CHC compounds or stable knockdown with shRNA, respectively, to assess in vitro and in vivo the effects of MCT1 inhibition and on response of GBM to temozolomide. Survival analyses on GBM patient cohorts were performed using Cox regression and Log-rank tests. Results: High levels of MCT1 expression were revealed to be a predictor of poor prognosis in multiple cohorts of GBM patients. Functionally, in U251 GBM cells, MCT1 stable knockdown decreased glucose consumption and lactate efflux, compromising the response to the MCT1 inhibitors CHC and AR-C155858. MCT1 knockdown significantly increased the survival of orthotopic GBM intracranial mice models when compared to their control counterparts. Furthermore, MCT1 downregulation increased the sensitivity to temozolomide in vitro and in vivo, resulting in significantly longer mice survival. Conclusions: This work provides first evidence for MCT1 as a new prognostic biomarker of GBM survival and further supports MCT1 targeting, alone or in combination with classical chemotherapy, for the treatment of GBM.

A New Chalcone Derivative with Promising Antiproliferative and Anti-Invasion Activities in Glioblastoma Cells.

Glioblastoma (GBM) is the most common and most deadly primary malignant brain tumor. Current therapies are not effective, the average survival of GBM patients after diagnosis being limited to few months. Therefore, the discovery of new treatments for this highly aggressive brain cancer is urgently needed. Chalcones are synthetic and naturally occurring compounds that have been widely investigated as anticancer agents. In this work, three chalcone derivatives were tested regarding their inhibitory activity and selectivity towards GBM cell lines (human and mouse) and a non-cancerous mouse brain cell line. The chalcone 1 showed the most potent and selective cytotoxic effects in the GBM cell lines, being further investigated regarding its ability to reduce critical hallmark features of GBM and to induce apoptosis and cell cycle arrest. This derivative showed to successfully reduce the invasion and proliferation capacity of tumor cells, both key targets for cancer treatment. Moreover, to overcome potential systemic side effects and its poor water solubility, this compound was encapsulated into liposomes. Therapeutic concentrations were incorporated retaining the potent in vitro growth inhibitory effect of the selected compound. In conclusion, our results demonstrated that this new formulation can be a promising starting point for the discovery of new and more effective drug treatments for GBM.

Adenosine Inhibits Cell Proliferation Differently in Human Astrocytes and in Glioblastoma Cell Lines.

Glioblastoma (GBM) is the most common brain primary tumour. Hypoxic regions in GBM are associated to tumour growth. Adenosine accumulates in hypoxic regions and can affect cell proliferation and survival. However, how proliferating GBM cells respond/adapt to increased adenosine levels compared to human astrocytes (HA) is not clarified and was addressed in the present work. GBM cell lines and HA were treated for 3 days with test drugs. Thirty Adenosine (30 µM) caused a 43% ± 5% (P < 0.05) reduction of cell proliferation/viability in HA, through an adenosine receptor-independent mechanism, but had no effect in GBM cell lines U87MG, U373MG and SNB19. Contrastingly, inhibition of adenosine phosphorylation (using the adenosine kinase (ADK) inhibitor 5-iodotubercidin (ITU) (25 µM)), produced a strong and similar decrease on cell proliferation in both HA and GBM cells. The effect of adenosine on HA proliferation/viability was potentiated by 100 µM-homocysteine. Combined application of 30 µM-adenosine and 100 µM-homocysteine reduced the cell proliferation/viability in all three GBM cell lines, but this reduction was much lower than that observed in HA. Adenosine alone did not induce cell death, assessed by lactate dehydrogenase (LDH) release, both in HA and GBM cells, but potentiated the cytotoxic effect of homocysteine in HA and in U87MG and U373MG cells. Results show a strong attenuation of adenosine anti-proliferative effect in GBM cells compared to HA, probably resulting from increased adenosine elimination by ADK, suggesting a proliferative-prone adaptation of tumour cells to increased adenosine levels.

The Role of Network Science in Glioblastoma.

Network science has long been recognized as a well-established discipline across many biological domains. In the particular case of cancer genomics, network discovery is challenged by the multitude of available high-dimensional heterogeneous views of data. Glioblastoma (GBM) is an example of such a complex and heterogeneous disease that can be tackled by network science. Identifying the architecture of molecular GBM networks is essential to understanding the information flow and better informing drug development and pre-clinical studies. Here, we review network-based strategies that have been used in the study of GBM, along with the available software implementations for reproducibility and further testing on newly coming datasets. Promising results have been obtained from both bulk and single-cell GBM data, placing network discovery at the forefront of developing a molecularly-informed-based personalized medicine.

Fucoidan/chitosan nanoparticles functionalized with anti-ErbB-2 target breast cancer cells and impair tumor growth in vivo.

The work herein presented reports the development of fucoidan/chitosan nanoparticles (NPs) loaded with gemcitabine and functionalized with ErbB-2 antibody at their surface (NPs + Gem + Ab). The maximum immobilization of ErbB-2 on NPs' surface was set at 10 µg mL-1 and resulted in NPs with a size around 160 nm, a polydispersity index of 0.18, and a zeta potential of 21 mV. ErbB-2 is overexpressed in some subtypes of breast cancers, and the targeting capability of the NPs + Gem + Ab system was confirmed by an increased cellular uptake of SKBR3 cells (ErbB-2 positive) when compared to MDA-MB-231 (ErbB-2 negative). To validate the targeting efficacy of NPs + Gem + Ab, a co-culture system with human endothelial and SKBR3 cells was established. Cytotoxic effects over endothelial cells were similar for all the tested conditions (between 25 and 30%). However, the NPs + Gem + Ab system presented increased toxicity over breast cancer cells, above 80% after 24 h, when compared to free Gem and NPs + Gem (around 15% and 20%, respectively). In vivo studies demonstrated that the developed targeting system significantly reduced tumor growth and the appearance of lung metastasis compared to untreated controls. In summary, the efficacy of the NPs + Gem + Ab system to target cancer cells was established and validated both in vitro and in vivo, being a compelling alternative strategy to current chemotherapeutic approaches.

Widespread overexpression from the four DNA hypermethylated HOX clusters in aggressive (IDHwt) glioma is associated with H3K27me3 depletion and alternative promoter usage.

In human, the 39 coding HOX genes and 18 referenced noncoding antisense transcripts are arranged in four genomic clusters named HOXA, B, C, and D. This highly conserved family belongs to the homeobox class of genes that encode transcription factors required for normal development. Therefore, HOX gene deregulation might contribute to the development of many cancer types. Here, we study HOX gene deregulation in adult glioma, a common type of primary brain tumor. We performed extensive molecular analysis of tumor samples, classified according to their isocitrate dehydrogenase (IDH1) gene mutation status, and of glioma stem cells. We found widespread expression of sense and antisense HOX transcripts only in aggressive (IDHwt) glioma samples, although the four HOX clusters displayed DNA hypermethylation. Integrative analysis of expression, DNA methylation, and histone modification signatures along the clusters revealed that HOX gene upregulation relies on canonical and alternative bivalent CpG island promoters that escape hypermethylation. H3K27me3 loss at these promoters emerges as the main cause of widespread HOX gene upregulation in IDHwt glioma cell lines and tumors. Our study provides the first comprehensive description of the epigenetic changes at HOX clusters and their contribution to the transcriptional changes observed in adult glioma. It also identified putative 'master' HOX proteins that might contribute to the tumorigenic potential of glioma stem cells.

Glioblastoma: Is There Any Blood Biomarker with True Clinical Relevance?

Glioblastoma (GBM) is the most frequent malignant primary brain tumor in adults, characterized by a highly aggressive, inflammatory and angiogenic phenotype. It is a remarkably heterogeneous tumor at several levels, including histopathologically, radiographically and genetically. The 2016 update of the WHO Classification of Tumours of the Central Nervous System highlighted molecular parameters as paramount features for the diagnosis, namely IDH1/2 mutations that distinguish primary and secondary GBM. An ideal biomarker is a molecule that can be detected/quantified through simple non- or minimally invasive methods with the potential to assess cancer risk; promote early diagnosis; increase grading accuracy; and monitor disease evolution and treatment response, as well as fundamentally being restricted to one aspect. Blood-based biomarkers are particularly attractive due to their easy access and have been widely used for various cancer types. A number of serum biomarkers with multiple utilities for glioma have been reported that could classify glioma grades more precisely and provide prognostic value among these patients. At present, screening for gliomas has no clinical relevance. This is because of the low incidence, the lack of sensitive biomarkers in plasma, and the observation that gliomas may develop apparently de novo within few weeks or months. To the best of our knowledge, there is no routine use of a serum biomarker for clinical follow-up. The purpose of this paper is to review the serum biomarkers described in the literature related to glioblastoma and their possible relationship with clinical features.

Exploiting the Complexities of Glioblastoma Stem Cells: Insights for Cancer Initiation and Therapeutic Targeting.

The discovery of glioblastoma stem cells (GSCs) in the 2000s revolutionized the cancer research field, raising new questions regarding the putative cell(s) of origin of this tumor type, and partly explaining the highly heterogeneous nature of glioblastoma (GBM). Increasing evidence has suggested that GSCs play critical roles in tumor initiation, progression, and resistance to conventional therapies. The remarkable oncogenic features of GSCs have generated significant interest in better defining and characterizing these cells and determining novel pathways driving GBM that could constitute attractive key therapeutic targets. While exciting breakthroughs have been achieved in the field, the characterization of GSCs is a challenge and the cell of origin of GBM remains controversial. For example, the use of several cell-surface molecular markers to identify and isolate GSCs has been a challenge. It is now widely accepted that none of these markers is, per se, sufficiently robust to distinguish GSCs from normal stem cells. Finding new strategies that are able to more efficiently and specifically target these niches could also prove invaluable against this devastating and therapy-insensitive tumor. In this review paper, we summarize the most relevant findings and discuss emerging concepts and open questions in the field of GSCs, some of which are, to some extent, pertinent to other cancer stem cells.

MicroRNA-30a-5pme: a novel diagnostic and prognostic biomarker for clear cell renal cell carcinoma in tissue and urine samples.

BACKGROUND: The rising incidence of renal cell carcinomas (RCC) constitutes a significant challenge owing to risk of overtreatment. Because aberrant microRNA (miR) promoter methylation contributes to cancer development, we investigated whether altered miR-30a-5p expression associates with DNA promoter methylation and evaluated the usefulness as clear cell RCC (ccRCC) diagnostic and prognostic markers. METHODS: Genome-wide methylome and RNA sequencing data from a set of ccRCC and normal tissue samples from The Cancer Genome Atlas (TCGA) database were integrated to identify candidate CpG loci involved in cancer onset. MiR-30a-5p expression and promoter methylation were quantitatively assessed by PCR in a tissue set (Cohort #1) and urine sets (Cohorts #2 and 3) from IPOPorto and Homburg University Hospital. Non-parametric tests were used for comparing continuous variables. MiR-30a-5p promoter methylation (miR-30a-5pme) performance as diagnostic (receiver operator characteristics [ROC] - validity estimates) and prognostic [metastasis-free (MFS) and disease-specific survival (DSS)] biomarker was further validated in urine samples from ccRCC patients by Kaplan Meier curves (with log rank) and both univariable and multivariable analysis. RESULTS: Two significant hypermethylated CpG loci in TCGA ccRCC samples, correlating with miR-30a-5p transcriptional downregulation, were disclosed. MiR-30a-5pme in ccRCC tissues was confirmed in an independent patient's cohort of IPOPorto and associated with shorter time to relapse. In urine samples, miR-30a-5pme levels identified cancer both in testing and validation cohorts, with 83% sensitivity/53% specificity and 63% sensitivity/67% specificity, respectively. Moreover, higher miR-30a-5pme levels independently predicted metastatic dissemination and survival. CONCLUSION: To the best of our knowledge, this is the first study validating the diagnostic and prognostic potential of miR-30a-5pme for ccRCC in urine samples, providing new insights for its clinical usefulness as non-invasive cancer biomarker.

Reliability of heart rate recovery indexes after maximal incremental tests / Reproducibilidad de los índices de recuperación de la frecuencia cardiaca después de las pruebas de esfuerzo máximas

INTRODUCTION: The relationship between heart rate (HR) recovery (HRR) and cardiovascular diseases (CAD) is well stablished, being that slower HRR is associated with an increased risk of sudden death and overall death, and it has been demonstrated to be independent predictor for both healthy and cardiac diseases individuals. However, it is not clear about which indexes from fast and slow phase of HRR have greater reliability after maximal exercise. This study aimed to verified which of the HRR indexes (T30 and DeltaHR60s for fast phase of recovery; DeltaHR300s and HR off-kinetics for slow phase) have better reliability in adults after maximal exercise test. MATERIAL AND METHOD: Twelve healthy and moderate physical active young men without heart diseases performed three maximal treadmill tests with an interval of at least 48 h. Treadmill test started with speed of 4 km.h-1, with increase of 1 km.h-1every minute until exhaustion. Beat-to-beat HR was recorded during exercise and 5 min of seated recovery to verify relative and absolute reliability of the T30, DeltaHR60s, DeltaHR300 and HR off-kinetics. RESULTS: It was found very high reproducibility in T30 (ICC = 0.91; SEM = 17.19s; CV = 13.51%), DeltaHR60s (ICC = 0.91; SEM = 2.40 bpm; CV = 9.08%), DeltaHR300s (ICC = 0.90; SEM = 2.69 bpm; CV = 5.42%) and HR off-kinetics parameters (ICC = 0.91-0.94; SEM = 2.43-3.63; CV = 4.06-8.10%), without difference for the variables among the tests (p > 0.05). CONCLUSION: The DeltaHR60s presented better reliability (higher ICC and lower CV) when compared to the T30, being both for fast phase of recovery. For slow phase, ΔHR300s and HR off-kinetics presented equivalent reliability

INTRODUCCIÓN: La relación entre la recuperación de la frecuencia cardíaca (RFC) y las enfermedades cardiovasculares está bien establecida, siendo que la RFC más lenta se asocia con un mayor riesgo de muerte súbita y muerte en general, y se ha demostrado que es un factor predictivo independiente tanto para las personas sanas como para las personas con enfermedades cardíacas. Sin embargo, no está claro qué índices de la fase rápida y lenta de la RFC tienen mayor confiabilidad después del ejercicio máximo. Este estudio tuvo como objetivo verificar cuál de los índices de RFC (T30, DeltaFC60s, DeltaFC300s y cinética de FC) tienen mayor confiabilidad en adultos después de las pruebas máximas de ejercicio. MATERIAL Y MÉTODO: Doce hombres con actividad física saludable y moderada sin enfermedades del corazón realizaron tres pruebas máximas en cinta rodante con un intervalo de al menos 48 h. La prueba en cinta rodante comenzó con una velocidad de 4 km.h-1, con un aumento de 1 km.h-1 cada minuto hasta el agotamiento. La FC de latido a latido se registró durante el ejercicio y 5 minutos de recuperación sentada para verificar la confiabilidad absoluta y relativa del T30, DeltaFC60s, DeltaFC300s y cinética de FC. RESULTADOS: Se encontró una reproducibilidad muy alta en T30 (CCI = 0,91; SEM = 17,19 s; CV = 13,51%), DeltaFC60s (CCI = 0,91; EEM = 2,40 lpm; CV = 9.08%), DeltaHR300s (CCI = 0,90; EEM = 2.69 lpm; CV = 5.42%) y los parámetros de cinética de FC (CCI = 0,91-0,94; EEM = 2,43-3,63; CV = 4,06-8,10%). CONCLUSIÓN: Los DeltaFC60s presentaron mejor confiabilidad (mayor ICC y menor CV) en comparación con el T30 para una rápida fase de recuperación. Para la fase lenta, DeltaFC300s y la cinética de FC fueron equivalentes