Mining of public sequencing databases supports a non-dietary origin for putative foreign miRNAs: underestimated effects of contamination in NGS

The report that exogenous plant miRNAs are able to cross the mammalian gastrointestinal tract and exert gene-regulation mechanism in mammalian tissues has yielded a lot of controversy, both in the public press and the scientific literature. Despite the initial enthusiasm, reproducibility of these results was recently questioned by several authors. To analyze the causes of this unease, we searched for diet-derived miRNAs in deep-sequencing libraries performed by ourselves and others. We found variable amounts of plant miRNAs in publicly available small RNA-seq data sets of human tissues. In human spermatozoa, exogenous RNAs reached extreme, biologically meaningless levels. On the contrary, plant miRNAs were not detected in our sequencing of human sperm cells, which was performed in the absence of any known sources of plant contamination. We designed an experiment to show that cross-contamination during library preparation is a source of exogenous RNAs. These contamination-derived exogenous sequences even resisted oxidation with sodium periodate. To test the assumption that diet-derived miRNAs were actually contamination-derived, we sought in the literature for previous sequencing reports performed by the same group which reported the initial finding. We analyzed the spectra of plant miRNAs in a small RNA sequencing study performed in amphioxus by this group in 2009 and we found a very strong correlation with the plant miRNAs which they later reported in human sera. Even though contamination with exogenous sequences may be easy to detect, cross-contamination between samples from the same organism can go completely unnoticed, possibly affecting conclusions derived from NGS transcriptomics

Circulating SNORD57 rather than piR-54265 is a promising biomarker for colorectal cancer: common pitfalls in the study of somatic piRNAs in cancer

There is increasing interest among cancer researchers in the study of Piwi-interacting RNAs (piRNAs), a group of small RNAs important for maintaining genome stability in the germline. Aberrant expression of piRNAs in cancer could imply an involvement of these regulatory RNAs in neoplastic transformation. On top of that, it could enable early cancer diagnosis based on RNA analysis in liquid biopsies, as piRNAs are not expected to widely circulate in the bloodstream of healthy individuals. Indeed, it has recently been shown that serum piR-54265 allows for excellent discrimination between colorectal cancer patients and healthy controls. However, we have also shown that most somatic piRNAs reported to date in mammals are actually fragments of other noncoding RNAs. Herein, we show that reports positioning piR-54265 as a noninvasive biomarker for colorectal cancer were actually measuring variations in the levels of a full-length (72 nt) small nucleolar RNA in serum. This should place a cautionary note for future research in somatic and cancer-specific piRNAs. We deeply encourage this line of research but discuss proper ways to identify somatic piRNAs without the interference of erroneous entries contained in piRNA databases.Wealso introduce the concept of miscellaneous-piRNAs (m-piRNAs) to distinguish between canonical piRNAs and other small RNAs circumstantially associated with PIWI proteins in somatic cells.ANII: FCE_3_2018_1_ 148745ANII: FSS_X_2018_1_14907

Ribonucleic artefacts: are some extracellular RNA discoveries driven by cell culture medium components?

In a recently published study, Anna Krichevsky and colleagues raise the important question ofwhether results of in vitro extracellular RNA (exRNA) studies, including extracellular vesicle (EV)investigations, are confounded by the presence of RNA in cell culture medium components suchas foetal bovine serum (FBS). The answer, according to their data, is a resounding“yes”. Even afterlengthy ultracentrifugation to remove bovine EVs from FBS, the majority of exRNA in FBSremained. Although technical factors may affect the degree of depletion, residual EVs andexRNA in FBS could influence the conclusions of in vitro studies: certainly, for secreted RNA,and possibly also for cell-associated RNA. In this commentary, we critically examine some of theliterature in this field, including a recent study from some of the authors of this piece, in light ofthe Wei et al. study and explore how cell culture-derived RNAs may affect what we think we knowabout EV RNAs. These findings hold particular consequence as the field moves towards a deeperunderstanding of EV–RNA associations and potential functions

Medical genomics contribution in clinical decisions in oncology

Agustina Arias: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Daniela Arin: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Martina Barbierato: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Agustina Maffioli: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Marcia Pérez: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Mathias Queirolo: Estudiante de Facultad de Medicina, Universidad de la República. Montevideo, Uruguay.-- Virginia Rodríguez Sande: Docente supervisor. Departamento Básico de Medicina, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Uruguay. Correo electrónico: [email protected] Alfonso Cayota: Docente supervisor. Departamento Básico de Medicina, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, UruguayEn las últimas décadas grandes avances en genética y biología molecular han contribuido a establecer las bases moleculares en la comprensión y diagnóstico de muchos procesos patológicos. De este modo surge la medicina genómica y el concepto de Medicina Personalizada o de Precisión. La información genética de cada individuo permite identificar variantes en el genoma que confieren riesgo a padecer enfermedades como el cáncer o responder diferencialmente a terapias. Realizamos una revisión bibliográfica de tipo sistemática y cualitativa, con el objetivo de conocer y evaluar la contribución de la genómica en la toma de decisiones en la clínica oncológica, centrándonos en los síndromes de predisposición hereditaria al cáncer de mama/ovario y colorrectal, debido a su mayor frecuencia, y conocer en qué situación nos encontramos a nivel Nacional. El desarrollo y aplicación de la genómica en la práctica clínica oncológica a nivel local ha ido en aumento, con aplicaciones en la prevención, diagnóstico y tratamiento de los síndromes de predisposición hereditaria al cáncer. Sin embargo, se destaca la falta de difusión de su importancia y cómo contactarse con los centros que brindan estos servicios, entre el personal de la salud y usuarios.In recent decades, great advances in genetics and molecular biology have contributed to establishing the molecular bases for understanding and diagnosing many pathological processes. Genomic medicine and the concept of personalized medicine arise. The genetic information of each individual makes it possible to identify variants in the genome that confer risk for diseases such as cancer or respond differentially to therapies. We carried out a systematic and qualitative bibliographic review, with the aim of knowing and evaluating the contribution of genomics in decision making in clinical oncology, focusing on hereditary predisposition syndromes to breast/ovarian and colorectal cancer, due to its greater frequency, to know in what situation we find ourselves in at a national level. The development and application of genomics in oncology clinical practice in our country has been increasing, with applications in the prevention, diagnosis and treatment of hereditary predisposition syndromes to cancer. However, the lack of dissemination of its importance and how to contact the centers that provide these services, among health personnel and users, is highlighted

Fragmentation of extracellular ribosomes and tRNAs shapes the extracellular RNAome

A major proportion of extracellular RNAs (exRNAs) do not copurify with extracellular vesicles (EVs) and remain in ultracentrifugation supernatants of cell-conditioned medium or mammalian blood serum. However, little is known about exRNAs beyond EVs. We have previously shown that the composition of the nonvesicular exRNA fraction is highly biased toward specific tRNA-derived fragments capable of forming RNase-protecting dimers. To solve the problem of stability in exRNA analysis, we developed a method based on sequencing the size exclusion chromatography (SEC) fractions of nonvesicular extracellular samples treated with RNase inhibitors (RI). This method revealed dramatic compositional changes in exRNA population when enzymatic RNA degradation was inhibited. We demonstrated the presence of ribosomes and full-length tRNAs in cell-conditioned medium of a variety of mammalian cell lines. Their fragmentation generates some small RNAs that are highly resistant to degradation. The extracellular biogenesis of some of the most abundant exRNAs demonstrates that extracellular abundance is not a reliable input to estimate RNA secretion rates. Finally, we showed that chromatographic fractions containing extracellular ribosomes are probably not silent from an immunological perspective and could possibly be decoded as damage-associated molecular patterns

Socioeconomic, Clinical, and Molecular Features of Breast Cancer Influence Overall Survival of Latin American Women

Molecular profile of breast cancer in Latin-American women was studied in five countries: Argentina, Brazil, Chile, Mexico, and Uruguay. Data about socioeconomic characteristics, risk factors, prognostic factors, and molecular subtypes were described, and the 60- month overall cumulative survival probabilities (OS) were estimated. From 2011 to 2013, 1,300 eligible Latin-American women 18 years or older, with a diagnosis of breast cancer in clinical stage II or III, and performance status ≦̸ 1 were invited to participate in a prospective cohort study. Face-to-face interviews were conducted, and clinical and outcome data, including death, were extracted from medical records. Unadjusted associations were evaluated by Chi-squared and Fisher’s exact tests and the OS by Kaplan–Meier method. Log-rank test was used to determine differences between cumulative probability curves. Multivariable adjustment was carried out by entering potential confounders in the Cox regression model. The OS at 60 months was 83.9%. Multivariable-adjusted death hazard differences were found for women living in Argentina (2.27), Chile (1.95), and Uruguay (2.42) compared with Mexican women, for older (≥60 years) (1.84) compared with younger (≤40 years) women, for basal-like subtype (5.8), luminal B (2.43), and HER2-enriched (2.52) compared with luminal A subtype, and for tumor clinical stages IIB (1.91), IIIA (3.54), and IIIB (3.94) compared with stage IIA women. OS was associated with country of residence, PAM50 intrinsic subtype, age, and tumor stage at diagnosis. While the latter is known to be influenced by access to care, including cancer screening, timely diagnosis and treatment, including access to more effective treatment protocols, it may also influence epigenetic changes that, potentially, impact molecular subtypes. Data derived from heretofore understudied populations with unique geographic ancestry and sociocultural experiences are critical to furthering our understanding of this complexity.Fil: de Almeida, Liz María. Instituto Nacional de Câncer; BrasilFil: Cortés, Sandra. Pontificia Universidad Católica de Chile; ChileFil: Vilensky, Marta. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; ArgentinaFil: Valenzuela, Olivia. Universidad de Sonora; MéxicoFil: Cortes Sanabria, Laura. Hospital de Especialidades Centro Medico Nacional Siglo XXI; MéxicoFil: de Souza, Mirian. Instituto Nacional de Câncer; BrasilFil: Barbeito, Rafael Alonso. Universidad de la República; UruguayFil: Abdelhay, Eliana. Instituto Nacional de Câncer; BrasilFil: Artagaveytia, Nora. Universidad de la Republica; UruguayFil: Daneri Navarro, Adrian. Universidad de Guadalajara; MéxicoFil: Llera, Andrea Sabina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Müller, Bettina. Instituto Nacional del Cáncer; ChileFil: Podhajcer, Osvaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Velazquez, Carlos. Universidad de Sonora; MéxicoFil: Alcoba, Elsa. Hospital Maria Curie; ArgentinaFil: Alonso, Isabel. Centro Hospitalario Pereira Rossell; UruguayFil: Bravo, Alicia I.. Hospital Higa Eva Perón; ArgentinaFil: Camejo, Natalia. Universidad de la República; UruguayFil: Carraro, Dirce Maria. A. C. Camargo Cancer Center; BrasilFil: Castro, Mónica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; ArgentinaFil: Cataldi, Sandra. Instituto Nacional del Cáncer; UruguayFil: Cayota, Alfonso. Instituto Pasteur de Montevideo; UruguayFil: Cerda, Mauricio. Universidad de Chile; ChileFil: Colombo, Alicia. Universidad de Chile; ChileFil: Crocamo, Susanne. Instituto Nacional de Câncer; BrasilFil: Silva-Garcia, Aida A.. Universidad de Guadalajara; MéxicoFil: Viña, Stella. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; ArgentinaFil: Zagame, Livia. Instituto Jalisciense de Cancerología; MéxicoFil: Jones, Beth. University of Yale; Estados UnidosFil: Szklo, Moysés. University Johns Hopkins; Estados Unido

The Transcriptomic Portrait of Locally Advanced Breast Cancer and Its Prognostic Value in a Multi-Country Cohort of Latin American Patients

Purposes: Most molecular-based published studies on breast cancer do not adequately represent the unique and diverse genetic admixture of the Latin American population. Searching for similarities and differences in molecular pathways associated with these tumors and evaluating its impact on prognosis may help to select better therapeutic approaches. Patients and Methods: We collected clinical, pathological, and transcriptomic data of a multi-country Latin American cohort of 1,071 stage II-III breast cancer patients of the Molecular Profile of Breast Cancer Study (MPBCS) cohort. The 5-year prognostic ability of intrinsic (transcriptomic-based) PAM50 and immunohistochemical classifications, both at the cancer-specific (OSC) and disease-free survival (DFS) stages, was compared. Pathway analyses (GSEA, GSVA and MetaCore) were performed to explore differences among intrinsic subtypes. Results: PAM50 classification of the MPBCS cohort defined 42·6% of tumors as LumA, 21·3% as LumB, 13·3% as HER2E and 16·6% as Basal. Both OSC and DFS for LumA tumors were significantly better than for other subtypes, while Basal tumors had the worst prognosis. While the prognostic power of traditional subtypes calculated with hormone receptors (HR), HER2 and Ki67 determinations showed an acceptable performance, PAM50-derived risk of recurrence best discriminated low, intermediate and high-risk groups. Transcriptomic pathway analysis showed high proliferation (i.e. cell cycle control and DNA damage repair) associated with LumB, HER2E and Basal tumors, and a strong dependency on the estrogen pathway for LumA. Terms related to both innate and adaptive immune responses were seen predominantly upregulated in Basal tumors, and, to a lesser extent, in HER2E, with respect to LumA and B tumors. Conclusions: This is the first study that assesses molecular features at the transcriptomic level in a multicountry Latin American breast cancer patient cohort. Hormone-related and proliferation pathways that predominate in PAM50 and other breast cancer molecular classifications are also the main tumor-driving mechanisms in this cohort and have prognostic power. The immune-related features seen in the most aggressive subtypes may pave the way for therapeutic approaches not yet disseminated in Latin America. Clinical Trial Registration: ClinicalTrials.gov (Identifier: NCT02326857).Fil: Llera, Andrea Sabina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Abdelhay, Eliana Saul Furquim Werneck. Instituto Nacional de Cancer; BrasilFil: Artagaveytia, Nora. Universidad de la Republica; UruguayFil: Daneri Navarro, Adrián. Universidad de Guadalajara; MéxicoFil: Müller, Bettina. Instituto Nacional del Cáncer; ChileFil: Velazquez, Carlos. Universidad de Sonora; MéxicoFil: Alcoba, Elsa B.. Hospital Maria Curie; ArgentinaFil: Alonso, Isabel. Centro Hospitalario Pereira Rossell; UruguayFil: Alves Da Quinta, Daniela Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Universidad Argentina de la Empresa; ArgentinaFil: Binato, Renata. Instituto Nacional de Cancer; BrasilFil: Bravo, Alicia Inés. Hospital Regional de Agudos Eva Perón; ArgentinaFil: Camejo, Natalia. Universidad de la Republica; UruguayFil: Carraro, Dirce Maria. Centro Internacional de Pesquisa; BrasilFil: Castro, Mónica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; ArgentinaFil: Castro Cervantes, Juan M.. Umae Hospital de Especialidades Centro Medico Nacional Siglo XXI; MéxicoFil: Cataldi, Sandra. Instituto Nacional del Cáncer; UruguayFil: Cayota, Alfonso. Instituto Pasteur de Montevideo; UruguayFil: Cerda, Mauricio. Universidad de Chile; ChileFil: Colombo, Alicia. Universidad de Chile; ChileFil: Crocamo, Susanne. National Cancer Institute; Estados UnidosFil: Del Toro Arreola, Alicia. Universidad de Guadalajara; MéxicoFil: Delgadillo Cisterna, Raúl. Umae Hospital de Especialidades Centro Medico Nacional Siglo Xxi; MéxicoFil: Delgado, Lucía. Universidad de la Republica; UruguayFil: Fernandez, Elmer Andres. Area de Cs. Agrarias, Ingeniería, Cs. Biológicas y de la Salud de la Universidad Catollica de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Fejerman, Laura. University of California at Davis; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trinchero, Alejandra. Hospital Regional de Agudos Eva Perón; ArgentinaFil: Valenzuela, Olivia. Universidad de Sonora; MéxicoFil: Vedham, Vidya. National Cancer Institute; Estados UnidosFil: Zagame, Livia. Instituto Jalisciense de Cancerología; MéxicoFil: Podhajcer, Osvaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

MicroRNAs and other small silencing RNAs in cancer.

Small noncoding RNAs are key controllers of cellular function, and their deregulation can lead to cancer development and metastatic evolution. This review summarizes the most important examples of small RNAs involved in human cancer and discusses their clinical use as biomarkers and drug targets for diagnosis, prognosis, and treatment of cancer. We also describe the possible mechanisms underlying small RNA-mediated transformation and outline the future describing new small RNA families with great potential in cancer biology. © 2010 IUBMB IUBMB Life, 2010

Non-coding RNA fragments account for the majority of annotated piRNAs expressed in somatic non-gonadal tissues

Juan Pablo Tosar et al. analyze existing databases to investigate whether piRNAs reportedly expressed outside the mammalian gonad are true piRNAs or likely contaminants. They conclude that the majority are fragments of non-coding RNAs from other small RNA classes rather than true piRNAs