Hepatitis B Virus (HBV) X protein (pX) is implicated by an unknown mechanism in hepatocellular carcinoma (HCC) development, characterized by increased rate of chromosomal aberrations. Although most patients clear the infection and develop immunity, chronic infection in 5 to 10% infected patients lead to HCC development in the 4th to 5th decade of life. I demonstrate that tetracycline-regulated pX expression induces multipolar spindles and polyploidy (>4N DNA). To understand the mechanism of pX-mediated polyploidy, I investigated whether pX promotes DNA re-replication. Dual-parameter flow...