title: Overexpression of miR-21-5p as a predictive marker for complete tumor regression to neoadjuvant chemoradiotherapy in rectal cancer patients.
abstract: BACKGROUND
  Neoadjuvant chemoradiotherapy (nCRT) followed by radical surgery is the preferred treatment strategy for locally advanced rectal cancer. However, complete tumor regression is observed in a significant proportion of patients after nCRT, making them ideal candidates for alternative treatment strategies to this considerably morbid procedure. Identification of such patients based on clinical findings (complete clinical response - cCR) is difficult mainly because it relies on subjective clinical and imaging studies. Our goal was to identify biomarkers capable of predicting complete response to nCRT.
  
  
  METHODS
  We analyzed miRNA expression profile using deep sequencing in rectal tumor biopsies prior to nCRT. Differential expression was investigated by EdgeR for a training (n = 27) and a validation (n = 16) set of patients to identify miRNAs associated with treatment response (complete vs. incomplete). In vitro experiments with two cancer cell lines were also performed in order to evaluate the possible role of miRNAs on response to nCRT.
  
  
  RESULTS
  We found 4 miRNAs differentially expressed between complete and incomplete responders to nCRT. In addition, validation was performed using an independent group of patients and miR-21-5p was confirmed as being overexpressed in complete responders. Overall sensitivity and specificity of miR-21-5p expression in predicting complete response to nCRT was 78% and 86% respectively. Interestingly, in a subset of patients with cCR followed by early local recurrence, the expression level of miR-21-5p was considerably low, similarly to incomplete responders. We also found SATB1, a miR-21-5p target gene and known multidrug resistance gene, whose expression was inversely correlated with miR-21-5p expression. Finally, we performed functional experiments and showed that miR-21-5p and SATB1 may be directly involved with poor response to nCRT in rectal cancer patients.
  
  
  CONCLUSIONS
  This study suggests miR-21-5p as a promising predictive biomarker, which should aid in the selection of patients with cCR to nCRT that potentially could be spared from radical surgery.
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. cramos@mochsl.org.br.|Fundação Antônio Prudente, São Paulo, Brazil. cramos@mochsl.org.br.
authors.forename: Camila Miranda
authors.initials: CM
authors.lastname: Lopes-Ramos
authors.affiliation: Angelita & Joaquim Gama Institute, São Paulo, Brazil. gamange@uol.com.br.|University of São Paulo School of Medicine, São Paulo, Brazil. gamange@uol.com.br.
authors.forename: Angelita
authors.initials: A
authors.lastname: Habr-Gama
authors.affiliation: Ludwig Institute for Cancer Research, São Paulo, Brazil. gluts2005@gmail.com.
authors.forename: Bruna de Souza
authors.initials: Bde S
authors.lastname: Quevedo
authors.affiliation: Angelita & Joaquim Gama Institute, São Paulo, Brazil. nmfelicio@gmail.com.|Hospital Alemão Oswaldo Cruz, São Paulo, Brazil. nmfelicio@gmail.com.
authors.forename: Natália Mariana
authors.initials: NM
authors.lastname: Felício
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. fbettoni@mochsl.org.br.
authors.forename: Fabiana
authors.initials: F
authors.lastname: Bettoni
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. fkoyama@mochsl.org.br.
authors.forename: Fernanda Christtanini
authors.initials: FC
authors.lastname: Koyama
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. pasprino@mochsl.org.br.
authors.forename: Paula Fontes
authors.initials: PF
authors.lastname: Asprino
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. pgalante@mochsl.org.br.
authors.forename: Pedro Alexandre
authors.initials: PA
authors.lastname: Galante
authors.affiliation: Angelita & Joaquim Gama Institute, São Paulo, Brazil. gama@ajgama.com.br.|University of São Paulo School of Medicine, São Paulo, Brazil. gama@ajgama.com.br.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Gama-Rodrigues
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. aacamargo@mochsl.org.br.|Ludwig Institute for Cancer Research, São Paulo, Brazil. aacamargo@mochsl.org.br.
authors.forename: Anamaria Aranha
authors.initials: AA
authors.lastname: Camargo
authors.affiliation: Angelita & Joaquim Gama Institute, São Paulo, Brazil. rodrigo.operez@gmail.com.|University of São Paulo School of Medicine, São Paulo, Brazil. rodrigo.operez@gmail.com.|Ludwig Institute for Cancer Research, São Paulo, Brazil. rodrigo.operez@gmail.com.
authors.forename: Rodrigo Oliva
authors.initials: RO
authors.lastname: Perez
authors.affiliation: Centro de Oncologia Molecular, Hospital Sírio-Libanês, São Paulo, Brazil. raphaparmigiani@gmail.com.br.
authors.forename: Raphael Bessa
authors.initials: RB
authors.lastname: Parmigiani
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics / Q000473:pathology / Q000628:therapy; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D059248:Chemoradiotherapy; D005260:Female; D005500:Follow-Up Studies; D015972:Gene Expression Regulation, Neoplastic; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008297:Male; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D009367:Neoplasm Staging; D011379:Prognosis; D012004:Rectal Neoplasms / Q000235:genetics / Q000473:pathology / Q000628:therapy*
chemical_list: D014408:Biomarkers, Tumor; C524940:MIRN21 microRNA, human; D036961:Matrix Attachment Region Binding Proteins; D035683:MicroRNAs; C076189:SATB1 protein, human