EBV DNA Content and Expression in Nasopharyngeal Carcinoma
We have analyzed EBV DNA content in nasopharyngeal carcinoma tissue (NPC) samples from endemic and nonendemic regions. The samples were histopathologically classified as 1) squamous cell carcinomas, 2) nonkeratinizing carcinomas, or 3) undifferentiated carcinomas. Southern blots, prepared from DNA purified from NPC tissues, were hybridized to 32p-labeled cloned restriction enzyme fragments of EBV. Twenty-six samples of all three histopathologic classifications regions were positive for EBV DNA. We have also attempted to identify the state of viral expression within the tumor at either the level of transcription or by identification of viral polypeptides.
The EBV sequences which encode mRNA in latently infected lymphocytes are transcribed inmost tumor specimens. Some NPC tumor specimens and tumors grown in nude mice contain RNA encoded by additional sequences. We have identified by Northern blot analyses some of the EBVmRNAs encoded by these sequences. Many are similar in size to EBV mRNAs which are believed to encode early functions.
To investigate the possibility of viral activation, immunoblots of tumor tissue lysates were prepared and reacted with high-titer EBV-specific antisera and a monoclonal antibody to the diffuse component of the early antigen (EAd). Proteins which may be viral specific were detected in some specimens; however EAd could not be detected in twenty-two tumor samples including those which had activated transcription.
KeywordsNude Mouse Nasopharyngeal Carcinoma Raji Cell Undifferentiated Carcinoma Viral Capsid Antigen
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