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Exosomes are cell-derived vesicles that convey key elements with the potential to modulate intercellular communication. They are known to be secreted from all types of cells, and are crucial messengers that can regulate cellular processes by 'trafficking' molecules from cells of one tissue to another. The exosomal content has been shown to be broad, composed of different types of cytokines, growth factors, proteins, or nucleic acids. Besides messenger RNA (mRNA) they can also contain noncoding transcripts such as microRNAs (miRNAs), which are small endogenous cellular regulators of protein expression. In diseases such as cancer, exosomes can facilitate tumor progression by altering their vesicular content and supplying the tumor niche with molecules that favor the progression of oncogenic processes such as proliferation, invasion and metastasis, or even drug resistance. The packaging of their molecular content is known to be tissue specific, a fact that makes them interesting tools in clinical diagnostics and ideal candidates for biomarkers. In the current report, we describe the main properties of exosomes and explain their involvement in processes such as cell differentiation and cell death. Furthermore, we emphasize the need of developing patient-targeted treatments by applying the conceptualization of exosomal-derived miRNA-based therapeutics.

Summary. We determined the hepatitis C virus (HCV) antibodies (anti-HCV) and the hepatitis B virus (HBV) surface antigen (HBsAg) in a cohort of 68 consecutive non-Hodgkin's lymphoma (NHL) patients diagnosed and treated in our institution between December 1997 and March 1999. 27 cases were diagnosed as low-grade, 33 as intermediate-grade, and eight as high-grade NHL. In 35 cases (51´4%) we found evidence of either HCV or HBV infection. Anti-HCV antibodies were found in 20 patients (29´5%) and HBsAg was found in 21 patients (30´8%). In six patients both anti-HCV and HBsAg were present. Anti-HCV were present in 12/27 low-grade NHL cases (44´4%) and in 8/41 intermediate/high-grade (aggressive) NHL cases (19´5%, P < 0´03). HBsAg was found in 10/27 low-grade NHL cases (37%) and in 11/41 aggressive NHL cases (26´8%). Evidence of liver disease, as re¯ected by elevated aminotransferases or typical alterations at liver biopsy, was present in eight patients. Cryoglobulins were present in six patients, all anti-HCV positive and with low-grade NHL. The prevalence of both HCV antibodies and HBsAg was signi®cantly higher (P < 0´0001) in our NHL cases than in a sample of the general Romanian population, where the prevalence of anti-HCV was 4´9% and that of HBsAg was 6´3%. It is dif®cult to say whether either HCV or HBV had actually been involved in lymphomagenesis or if a-interferon treatment would be effective in this subset of patients.

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