The role of interleukin-6 (IL-6) in the growth of an androgen-independent prostate cancer cell line (PC-3m) was defined and the effect of dexamethasone, which was previously shown to modulate IL-6/IL-6 receptor (IL-6R) on this procedure was investigated. By using a pretty sensitive and specific enzyme immunoassay (ELISA), it was found that PC-3m produced certain IL-6, but there was no difference in IL-6 secretion between the group with or without dexamethasone treatment. It was also found that PC-3m cells could not be stimulated to grow by exogenous IL-6 (P>0. 05), while it could be inhibited to grow by anti-IL-6 monoclonal antibody and dexamethasone with a dose-dependent fashion. Our observation indicated that IL-6 acted as an autocrine growth factor for PC-3m, and dexamethasone could inhibit cell proliferation by a mechanism independent of its effect on IL-6 mRNA expression.

The effect of transforming growth factor β₁ (TGF-β₁) gene transfection on the proliferation of bone marrow-derived mesenchymal stem cells (MSCs) and the mechanism was investigated to provide basis for accelerating articular cartilage repairing using molecular tissue engineering technology. TGF-β₁ gene at different doses was transduced into the rat bone marrow-derived MSCs to examine the effects of TGF-β₁ gene transfection on MSCs DNA synthesis, cell cycle kinetics and the expression of proliferating cell nuclear antigen (PCNA). The results showed that 3 μl lipofectaminemediated 1 μg TGF-β₁ gene transfection could effectively promote the proliferation of MSCs best; Under this condition (DNA/Lipofectamine= 1μg/3μl) flow cytometry and immunohistochemical analyses revealed a significant increase in the³H incorporation, DNA content in S phase and the expression of PCNA. Transfection of gene encoding TGF-β₁ could induce the cells at G0/G1 phase to S1 phase, modulate the replication of DNA through the enhancement of the PCNA expression, increase the content of DNA at S1 phase and promote the proliferation of MSCs. This new molecular tissue engineering approach could be of potential benefit to enhance the repair of damaged articular cartilage, especially those caused by degenerative joint diseases.