Viral latent proteins as targets for Kaposi's sarcoma and Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) induced lymphoma.
Herpesvirus 8, Human
Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) is present in all Kaposi's sarcoma tumor cells as well as in several lymphomas that are linked to this agent. Every tumor cell expresses the viral latent protein LANA, which is required for KSHV latent replication and proper segregation of the viral episome. In certain tumors, other latent KSHV proteins (LANA-2/vIRF3, v-cyclin, v-IL6) are expressed as well. Since all herpesviruses persist for life in infected individuals, only eradication of latent virus can cure infection. The KSHV latent genes serve as bona fide tumor markers, but do they also provide targets for anti-tumor and/or anti-viral drugs? To decide this question we review the known biochemical interactions between KSHV latent proteins and their viral and cellular partners. Recent epidemiological studies show that KSHV lytic replication precedes KSHV associated cancers. Gancilovir has been linked to KS tumor regression, which implicates the KSHV-encoded polymerase as a potential intervention point. Yet, KSHV specific transactivators might represent more specific targets, as they have no cellular homologs. In particular Rta/orf50 is necessary and sufficient for lytic replication and deserves serious consideration as a target for KSHV-specific antivirals.