OBJECTIVETo establish a syngeneic mouse model of liver tumor stably expressing hepatitis B virus (HBV) antigens.

METHODSMelanoma cell line B16 cells were transfected with pLXSN-2HBV. Cells (named B16/HBV) stably and persistently expressing HBV surface (HBsAg) and core (HBcAg) antigens were identified. The cells were injected into the hepatic subcapsular space of fifteen C57BL/6J mice. The mice were divided into 3 groups, receiving 100, 1000 or 5000 cells in a total volume of 5 µl per mouse, respectively, five mice in each group. Two weeks after the tumor cell inoculation, serum samples from the mice were collected weekly and the serum concentration of HBsAg and anti-HBs was quantified by ELISA. The tumor growth in the mouse liver was monitored by a high-resolution ultrasound system. Expression of HBsAg and HBcAg in the tumor tissues was determined by immunohistochemistry.

RESULTSLiver tumors were formed in all the mice receiving 1000 and 5000 B16/HBV cells per mouse, and in 80% of the mice receiving 100 B16/HBV cells. HBsAg and anti-HBs were detectable in their sera from 2 weeks after tumor cell inoculation. The mice receiving 100 cells per mouse began to die 4 weeks, those receiving 1000 cells per mouse began to die 3 - 4 weeks and those receiving 5000 cells began to die 2 - 3 weeks after the cell inoculation. All the tumor cells expressed HBsAg and HBcAg.

CONCLUSIONSThe B16/HBV cells stably and persistently express HBV antigens both in vitro and in vivo. A mouse model of transplanted liver tumor stably expressing HBV antigens has been successfully established by inoculation of those cells into the hepatic subcapsular space.