Human dermal fibroblasts and mouse NIH/3T3 cells acquired the transformed phenotype (‘criss-cross' pattern of growth) after infection with ultraviolet-irradiated murine gammaherpesvirus (MuHV-4 strain 68; MHV-68). These cells with changed phenotype could be serially cultured for 5-6 passages (35-40 days), and then they entered into crisis and most of them died. In a small number of cultures, however, foci of newly transformed cells appeared from which two stable cell lines were derived. After 6-9 cell culture passages of the MHV-68 transformed cell lines, MHV-68 DNA and virus antigen could be detected by PCR and immunofluorescence assay along with the disappearance of actin bundles, indicating that both transformed cell lines might be oncogenic.

Three strains of herpes simplex virus, K17syn- and HSZPsyn+ of type 1 (HSV-1) and USsyn- of type 2 (HSV-2), were photoinactivated in the presence of methylene blue and used to infect 3 cell lines, normal human lung tissue cells (MRC-5), mouse epithelial cells (NIH3T3), and human lung carcinoma cells (A549). The virus titer and phenotype of cells were evaluated to compare the characteristics of normal and carcinoma cells infected with non-syncytial (non-syn) and syncytial (syn) strains of herpes simplex viruses. We found that the cells of both normal cell lines infected with photoinactivated K17syn- and USsyn- but not HSZPsyn+ acquired transformed phenotype accompanied by the presence of virus. Surprisingly, the infection with photoinactivated viruses K17syn- and USsyn- but not HSZPsyn+ resulted in the suppression of the transformed phenotype of A549 cells. Using nested PCR, herpesviral DNA was identified in newly transformed cells and cells that lost the transformed phenotype. The effect of putative herpesvirus-related growth factors (HRGF) produced by cells infected with photoinactivated viruses was quantified and compared. Since methylene blue is currently used in phototherapy of herpetic lesions, these results raise the question of whether such therapy is risky to human health.

Infection of human MRC-5 cells and mouse NIH-3T3 cells with a murine gamma-herpesvirus (MuHV-4 strain 68; MHV-68) photoinactivated by visible light in the presence of methylene blue (MB) resulted in nonproductive infection and the appearance of morphologically transformed cells. Two stably transformed cell lines were derived from both of these cell types and were confirmed to contain both viral DNA and antigen. Next, a quiescent MHV-68 infection in MRC-5 and NIH-3T3 cells was established after cultivation at 41°C in the presence of phosphonoacetic acid. Following the exposure of quiescently infected cells to visible light for 120 s (5 times daily for 6 days) in the presence of MB, both MRC-5 and NIH-3T3 cells were observed to acquire transformed phenotypes. The cytopathic effect was observed in cells after 4-5 passages, after which the cells degenerated. However, when human interferon (IFN)-α and mouse IFN-β were added to the media of quiescently infected MRC-5 and NIH-3T3 cells during the photoinactivating procedure, 2 stable transformed cell lines containing both viral DNA and the antigen were obtained and resembled those attained following nonproductive infection with photoinactivated virus.

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SúhrnĽudské vírusy herpes simplex typ 1 a 2 (HSV-1, HSV-2) sa väčšinou na základe séroepidemiologických štúdií dávajú do súvislosti s viacerými nádorovými ochoreniami. Nepredpokladá sa však, že by pri vzniku nádorov mali priamu úlohu. Pôsobia pravdepodobne len ako kofaktory. Experimentálne sa podarilo dokázať ich schopnosť transformovať bunky in vitro odstránením ich vysokej lytickej schopnosti určitou dávkou UV žiarenia alebo fotoinaktiváciou v prítomnosti fotosenzitizérov, napr. neutrálnej červene alebo metylénovej modrej alebo kultiváciou v podmienkách potláčajúcich ich lytickú schopnosť. K vzniku nádorov by mohli prispieť niekoľkými mechanizmami. Podľa mechanizmu "hit and run" navodí vírusová DNA interakciou s bunkovou DNA a indukciou genetických a epigenetických zmien len iniciáciu transformácie a na ďalšom procese neoplastickej progresie sa už nepodiela. Podľa mechanizmu "hijacking" môže vírusový produkt v infikovaných bunkách aktivovať signálnu dráhu a spôsobiť tým nekontrolovateľnú proliferáciu. Takýmto produktom je napr. produkt génu HSV-2 označovaného ako ICP10, ktorý kóduje onkoproteín RR1PK aktivujúci signálnu dráhu Ras. V dvoch prípadoch, v prípade serózneho karcinómu vaječníkov a v niektorých nádoroch prostaty boli dokázané vírusom kódované mikroRNA ako možní spolopôvodcovia vzniku nádorov. Možnú úlohu by mohli hrať aj nedávno popísané rastové faktory asociované s herpetickými vírusmi s transformačným a transformáciu potláčajúcim účinkom. Nakoniec, existuje rad dôkazov, že HSV-2 môže zvyšovať riziko vzniku cervikálneho karcinómu po infekcii s ľudskými papilómovými vírusmi. Kľúčové slová HSV-1 -HSV-2 -nádory -mechanizmy transformácie SummarySeroepidemiological studies suggest that human herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) are linked with several types of cancer; however, they do not appear to play a direct role and are considered to be cofactors. The abilities of HSV-1 and -2 to transform cells in vitro can be demonstrated by suppress ing their lytic ability via irradiation with a specific dose of ultraviolet light, photoinactivation in the presence of photosensitizers (e. g., neutral red or methylene blue), and culture under specific conditions. Several mechanisms have been proposed to explain the actions of these viruses. Accord ing to the hit-and-run mechanism, viral DNA initiates transformation by interact ing with cellular DNA and thereby induc ing mutations and epigenetic changes, but is not involved in other stages of neoplastic progression. By contrast, accord ing to the hijack ing mechanism, viral products in infected cells can activate signal ing pathways and thereby cause uncontrolled proliferation. Such products include RR1PK, an oncoprotein that activates the Ras pathway and is encoded by the HSV-2 gene ICP10 . Virus-encoded microRNAs may act as cofactors in tumorigenesis of serous ovarian carcinoma and some prostate tumors. Herpes virus-associated growth factors that facilitate or suppress transformation may play important roles in tumor formation. Finally, there is much ...