Micro-ribonucleic acids: potential noninvasive biomarkers for hepatocellular carcinoma Limin Li, Wenli Diao, Ke Zen Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, People's Republic of China Abstract: Hepatocellular carcinoma (HCC) is one of the most common malignancies globally. Each year, more than 500,000 people worldwide are diagnosed with HCC. The onset of HCC is typically unnoticeable, and the prognosis is usually poor. The early diagnosis of HCC and dynamic monitoring of this disease can contribute to more effective therapeutic interventions and improve patient outcomes. To achieve early diagnosis, more sensitive, specific, and easily detectable biomarkers are necessary. Recently, scientists have focused on identifying novel, sensitive, and minimally invasive or noninvasive biomarkers. Micro-ribonucleic acids (miRNAs) are a class of endogenous noncoding single-stranded RNAs that regulate gene expression at the posttranscriptional level. By negatively regulating target-gene expression, miRNAs play a critical role in diverse biological processes, including apoptosis, proliferation, differentiation, and developmental timing. Unique changes in miRNA expression in serum or plasma samples from HCC patients have been reported, suggesting that miRNAs may serve as novel noninvasive biomarkers for diagnosing HCC and evaluating therapeutic responses or as potential therapeutic targets in HCC. This review focuses on recent progress in understanding the role of miRNAs in HCC pathogenesis and progression, and highlights their diagnostic and prognostic value for HCC patients. Keywords: hepatocellular carcinoma, miRNA, biomarker, diagnosis, prognosis