Fig 2.

KSHV production and cell viability in ORF50ΔSTAD BCBL-1 cells treated with increasing DOX. (A) KSHV virions, assayed as protected KSHV DNA. TPA induces KSHV virion production in the absence of DOX. With DOX at low concentrations, induction of ORF50ΔSTAD blocks KSHV virion production. However, at high DOX concentrations (≥5 μg/ml), DOX not only fails to block KSHV virion production triggered by TPA treatment but also is associated with the induction of high levels of KSHV virion production. (B) High DOX concentrations (≥5 μg/ml) are associated with a decrease in cell viability as measured by trypan blue exclusion. (C) The cells were examined with flow cytometry for apoptotic markers using propidium iodide (PI) and annexin V (Ann). At high DOX (≥5 μg/ml), most cells scored positive for PI and Ann staining, indicating apoptosis. Ann-/PI-, no staining for either annexin V or propidium iodide; Ann+, positive staining for annexin V alone; PI+, positive staining for propidium iodide alone; Ann+/PI+, positive staining for both annexin V and propidium iodide.