Analysis of Cell-free Epstein-Barr Virus-associated RNA in the Plasma of Patients with Nasopharyngeal Carcinoma

Chen et al. (1) and Nawroz et al. (2) have reported that tumor-derived DNA is detectable in the plasma and serum of cancer patients and have opened up a new molecular approach for the early detection of malignancy. It is not known, however, whether circulating tumor-derived RNA is also present in plasma, because of the lability of RNA. To address this possibility, we used nasopharyngeal carcinoma (NPC) as a model system and attempted to detect Epstein-Barr virus (EBV)-latent gene transcripts in cell-free plasma samples from NPC patients.NPC constitutes one of the commonest cancers in Hong Kong and Southern China (3). Previous studies have indicated that EBV is consistently detected in all undifferentiated NPC cases and is present in all cancer cells (3). Latent EBV infection is an early event in the development of this cancer (4). These findings suggested that the EBV genome and latency products may serve as potential markers for the screening and diagnosis of this cancer. Among the EBV-latent genes, the small EBV-encoded RNAs (EBERs) are expressed in all NPC cases and are the most abundant latency-associated transcripts in NPC cells (∼105 to 106 …