title: A microRNA biomarker of hepatocellular carcinoma recurrence following liver transplantation accounting for within-patient heterogeneity.
abstract: BACKGROUND
  Liver cancer, of which hepatocellular carcinoma (HCC) is by far the most common type, is the second most deadly cancer (746,000 deaths in 2012). Currently, the only curative treatment for HCC is surgery to remove the malignancy (resection) or to remove the entire diseased liver followed by transplantation of healthy liver tissue. Given the shortage of healthy livers, it is crucial to provide transplants to patients that have the best chance of long-term survival. Currently, transplantation is determined via the Milan criteria-patients within Milan (single tumor < 5 cm or 2-3 tumors < 3 cm with no extrahepatic spread nor intrahepatic vascular invasion) are typically eligible for transplantation. However, combining microRNA expression profiling with the Milan criteria can improve prediction of recurrence. HCC often presents with multiple distinct tumor foci arising from local spread of a primary tumor or from the oncogenic predisposition of the diseased liver. Substantial genomic heterogeneity between tumor foci within a single patient has been reported; therefore, biomarker development must account for the possibility of highly heterogeneous genomic profiles from the same individual.
  
  
  METHODS
  MicroRNA profiling was performed on 180 HCC tumor samples from 89 patients who underwent liver transplantation at the University of Rochester Medical Center. The primary outcome was recurrence-free survival time, and patients were observed for 3 years post-transplantation.
  
  
  RESULTS
  MicroRNA expression profiles were used to develop a biomarker that distinguishes HCC patients at greater risk of recurrence post-transplantation. Unsupervised clustering uncovered two distinct subgroups with vast differences in standard transplantation selection criteria and recurrence-free survival times. These subgroups were subsequently used to identify microRNAs strongly associated with HCC recurrence. Our results show that reduced expression of five specific microRNAs is significantly associated with HCC recurrence post-transplantation.
  
  
  CONCLUSIONS
  MicroRNA profiling of distinct tumor foci, coupled with methods that address within-subject tumor heterogeneity, has the potential to significantly improve prediction of HCC recurrence post-transplantation. The development of a clinically applicable HCC biomarker would inform treatment options for patients and contribute to liver transplant selection criteria for practitioners.
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, NY, USA.
authors.forename: Qing Yan
authors.initials: QY
authors.lastname: Xie
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, NY, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Almudevar
authors.affiliation: Department of Pathology, University of Rochester Medical Center, Rochester, NY, USA.
authors.forename: Christa L
authors.initials: CL
authors.lastname: Whitney-Miller
authors.affiliation: Department of Surgery, University of Rochester Medical Center, Rochester, NY, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Barry
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester Medical Center, Rochester, NY, USA. mccallm@gmail.com.|Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY, USA. mccallm@gmail.com.
authors.forename: Matthew N
authors.initials: MN
authors.lastname: McCall
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D016000:Cluster Analysis; D018572:Disease-Free Survival; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D018740:Genetic Heterogeneity; D006801:Humans; D053208:Kaplan-Meier Estimate; D008113:Liver Neoplasms / Q000235:genetics*; D016031:Liver Transplantation; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D009364:Neoplasm Recurrence, Local / Q000235:genetics* / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D035683:MicroRNAs
keywords: Biomarker; Hepatocellular carcinoma (HCC); Liver transplantation; Recurrence; microRNA