OBJECTIVETo establish a bone metastasis model of prostate cancer by intratibia injection of Du145 in nude mice, observe the local growth of tumor in tibia and then assess application value of this model.

METHODSFor 9 male nude mice, Du145 (5 x 10(6)) was injected in tibia by a TB syringe with a 29-gauge needle at a dose of 30 microl per mouse. Then the vital signs of the nude mice were observed. When the mice were dying, they were sacrificed, and the tissues of right hindlimbs, lymphatic nodes, lungs and livers were taken out, fixed in 10% formalin, embedded in paraffin, stained by HE and then observed microscopically.

RESULTSIncidence of bone tumor after intratibia injection was 67% (6 out of 9). About 48 days later, there were some small palpable nodes in right hind-limbs of the 6 mice and they couldn't walk normally. About 55 days later, cachexia occurred in them. After dissection, some carrion-like tissue grew from marrow cavity to muscular spatium, which was identified as tumor tissue by HE. The envelop of livers became crampy, and acute hepatitis could be diagnosed through microscopy, which represented a large scale of hepatocytic death, liver sinus dilatation and hyperemia, hepatic lobule infiltrated by lymphocyte, macrophage and inconspicuous hyperplasia. Since hypohepatia occurred too early, we couldn't detected distant metastases.

CONCLUSIONThe intratibia injection model is an optimal animal model to study metastasis of prostate cancer. It mimics the natural situation of human prostate cancer and will help to understand the mechanisms of androgen-independence and osseous metastasis, and tumor-host determinants of PSA expression.