Histone deacetylase inhibitors (HDACs) are known to exhibit antiproliferative effects on various carcinoma cells. In this study, the in vivo efficiency of two HDACs, sodium butyrate and tributyrin, on prostate cancer growth inhibition were investigated. To gain an insight into the possible underlying pathways, cell culture experiments were performed focusing on the expression of p21, Rb and cmyc. For in vivo testing, prostate cancer cell lines (PC3 and TSU-Pr1) were seeded on the chorioallantois membrane (CAM) and implanted in a xenograft model using nude mice. Standard Western blot analysis was performed for protein expression of p21, Rb and c-myc in HDAC-treated vs untreated prostate cancer cells. Both sodium butyrate and tributyrin had a considerable treatment effect on microtumours on the chicken egg at already very low concentrations of 0.1 mM. Tributyrin-treated tumours showed the strongest effect with 38% apoptotic nuclei in the prostate cancer cell line PC3. In the mouse model, there was almost no difference between sodium butyrate and tributyrin. In untreated animals the tumours were almost double the size 4 weeks after implantation. Tumours of the treatment groups had a significantly lower percentage of Ki-67-positive-stained nuclei. As demonstrated by Western blot analysis, these effects seem to be independent of p53 status and a pathway via p21 -Rb -c-myc is possibly involved. In this study we have demonstrated a substantial in vivo treatment effect, which can be induced by the application of sodium butyrate or the orally applicable tributyrin in human prostate cancer. The given results may provide the rationale to apply these drugs in well-controlled clinical trials in patients being at high risk of recurrence after specific therapy or in patients with locally or distant advanced prostate cancer.
Progression to androgen independence remains the main problem that impacts on survival and quality of life in prostate cancer patients. We have investigated the potency of tributyrin, an orally available prodrug of butyrate, to induce growth arrest, differentiation and apoptosis in LNCaP, PC-3 and TSU-PR1 human prostate cancer cell lines. Cells were treated with 0.1 to 5 mM tributyrin or sodium butyrate. Growth inhibition, cell cycle arrest and apoptosis induction was assessed using standard methods. Both agents induced a more differentiated, fibroblast-like phenotype in androgen-sensitive as well as androgen-resistant cell lines. Expression of prostate-specific antigen was increased in LNCaP cells by tributyrin as a indicator of differentiation. The IC(50) for sodium butyrate was 2.5 mM in PC-3 and TSU-PR1 cells. LNCaP cells exhibited <50% growth inhibition at 5 mM sodium butyrate. However, the IC(50) for tributyrin was 0.8 mM in PC-3 cells, 1.2 mM in TSU-PR1 cells and 3.1 mM in LNCaP cells. Flow cytometry revealed a strong G1-arrest after exposure to tributyrin or sodium butyrate. Both agents resulted in a strong increase of apoptosis rates compared with mock-treated cells. Overall, tributyrin had a 2.5- to 3-fold growth inhibitory and apoptosis-inducing potency compared with equimolar concentrations of sodium butyrate. Our results demonstrate that tributyrin is more potent than butyrate in regard to cell growth inhibition and apoptosis induction at pharmacologically relevant concentrations. Hence, tributyrin may be a promising candidate for clinical protocols in prostate cancer.
Progression to androgen independence remains the main problem that impacts on survival and quality of life in prostate cancer patients. We have investigated the potency of tributyrin, an orally available prodrug of butyrate, to induce growth arrest, differentiation and apoptosis in LNCaP, PC‐3 and TSU‐PR1 human prostate cancer cell lines. Cells were treated with 0.1 to 5 mM tributyrin or sodium butyrate. Growth inhibition, cell cycle arrest and apoptosis induction was assessed using standard methods. Both agents induced a more differentiated, fibroblast‐like phenotype in androgen‐sensitive as well as androgen‐resistant cell lines. Expression of prostate‐specific antigen was increased in LNCaP cells by tributyrin as a indicator of differentiation. The IC50 for sodium butyrate was 2.5 mM in PC‐3 and TSU‐PR1 cells. LNCaP cells exhibited <50% growth inhibition at 5 mM sodium butyrate. However, the IC50 for tributyrin was 0.8 mM in PC‐3 cells, 1.2 mM in TSU‐PR1 cells and 3.1 mM in LNCaP cells. Flow cytometry revealed a strong G1‐arrest after exposure to tributyrin or sodium butyrate. Both agents resulted in a strong increase of apoptosis rates compared with mock‐treated cells. Overall, tributyrin had a 2.5‐ to 3‐fold growth inhibitory and apoptosis‐inducing potency compared with equimolar concentrations of sodium butyrate. Our results demonstrate that tributyrin is more potent than butyrate in regard to cell growth inhibition and apoptosis induction at pharmacologically relevant concentrations. Hence, tributyrin may be a promising candidate for clinical protocols in prostate cancer. Int. J. Cancer 88:245–251, 2000. © 2000 Wiley‐Liss, Inc.
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