Exosomes are discrete populations of small (40-200 nm in diameter) membranous vesicles that are released into the extracellular space by most cell types, eventually accumulating in the circulation. As molecular messengers, exosomes exert a broad array of vital physiologic functions by transporting information between different cell types. Because of these functional properties, they may have potential as biomarker sources for prognostic and diagnostic disease. Recent research has found that exosomes have potential to be utilized as drug delivery agents for therapeutic targets. However, basic researches on exosomes and researches on their therapeutic potential both require the existence of effective and rapid methods for their separation from human samples. In the current absence of a standardized method, there are several methods available for the separation of exosomes, but very few studies have previously compared the efficiency and suitability of these different methods. This review summarized and compared the available traditional and novel methods for the extraction of exosomes from human samples and considered their advantages and disadvantages for use in clinical laboratories and point-of-care settings.

A retrospective cohort study was conducted to identify risk factors for recurrence of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) after curative resection. A total of 317 patients who had received curative resection of pathologically proven small HCC (< or = 3 cm in diameter) were analyzed to ascertain the factors affecting recurrence. The median follow-up period was 33.7 months. Cumulative recurrence rates at 1, 3, and 5 years after resection were 23.5%, 49.5%, and 65.5%, respectively. Male sex, alpha-fetoprotein (AFP) > or = 400 ng/mL, HBV DNA level > or = 4 log(10) copies/mL, prolonged prothrombin time, tumor size > or = 2 cm, microvascular invasion, absence of capsular formation, moderate/poor tumor differentiation, and absence of postoperative interferon-alpha (IFN-alpha) treatment were associated with increased cumulative risk of HCC recurrence. By multivariate analysis, HBV DNA level > or = 4 log(10) copies/mL (P < 0.001, hazard ratio (HR) 2.110), AFP > or = 400 ng/mL (P = 0.011, HR 1.574), microvascular invasion (P < 0.001, HR 1.767), and postoperative IFN-alpha treatment (P = 0.022, HR 0.562) remained to be independently associated with HCC recurrence. Those contributing to late recurrence (>2 years) were older age and HBV DNA level > or = 4 log(10) copies/mL. Patients with persistent HBV DNA level > or = 4 log(10) copies/mL at resection and follow-up had the highest recurrence risk (P < 0.001, HR 4.129). HBV DNA level > or = 4 log(10) copies/mL at the time of resection was the most important risk factor for recurrence. Postoperative IFN-alpha treatment significantly decreased the recurrence risk after resection.

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