ABSTRACT
BACKGROUND: To assess the activity of docetaxel in combination with hormonal therapy in preclinical models of prostate cancer. MATERIALS AND METHODS: Since prostate cancer has a predilection for the bone, we assessed the antitumor activity of docetaxel in in vivo models of both bone metastasis and localized prostate cancer, using MDA PCa 2b and PC3 cells in SCID mice. RESULTS: Dramatic antitumor efficacy was observed regardless of whether the tumor cells were implanted in the prostate or in the bone. Antitumor activity was also evident in both osteolytic and osteoblastic lesions. Reasoning that docetaxel efficacy might be enhanced if it were to be used earlier in the course of the disease, we studied the sequence of docetaxel and androgen ablation (part of standard treatment for early-stage prostate cancer) in the MDA PCa 2b xenograft model. The activity was similar whether docetaxel and androgen ablation were used alone, simultaneously, or in sequence, indicating a lack of synergism or antagonism. Finally, we studied the combination of docetaxel and estramustine on androgen-sensitive and androgen-independent cell lines in vitro and in vivo. Estramustine did not increase the activity of docetaxel in these models. CONCLUSION: These results provide a strong preclinical rationale for the clinical development of docetaxel for the treatment of both locally advanced and disseminated prostate cancer.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/pharmacology , Prostatic Neoplasms/therapy , Taxoids/pharmacology , Animals , Antineoplastic Agents, Hormonal/administration & dosage , Antineoplastic Agents, Hormonal/pharmacology , Antineoplastic Agents, Phytogenic/administration & dosage , Antineoplastic Agents, Phytogenic/pharmacology , Bone Neoplasms/drug therapy , Bone Neoplasms/secondary , Bone Neoplasms/therapy , Cell Line, Tumor , Docetaxel , Dose-Response Relationship, Drug , Drug Administration Schedule , Drug Synergism , Estramustine/administration & dosage , Humans , Male , Mice , Mice, SCID , Orchiectomy , Prostatic Neoplasms/drug therapy , Prostatic Neoplasms/surgery , Taxoids/administration & dosage , Xenograft Model Antitumor AssaysSubject(s)
Cell Separation/methods , Prostatic Neoplasms/pathology , Animals , Cell Line, Tumor , Humans , Male , Tumor Cells, CulturedABSTRACT
PURPOSE: Prostate cancer specifically metastasizes to bone where it leads to bone formation. We previously reported that coculturing MDA PCa 2b prostate cancer cells with primary mouse osteoblasts (PMOs) induced PMO proliferation and differentiation. An osteoblastic reaction was also observed in vivo after injection of MDA PCa 2b cells into the bones of severe combined immunodeficient disease mice. The aim of this study was to identify the sequence of events that leads to these osteoblastic lesions in vivo and, using this in vitro model, to define the contributions of various genes and cellular pathways in the pathophysiology of osteoblastic bone metastases of prostate cancer. EXPERIMENTAL DESIGN AND RESULTS: We show histological evidence of de novo bone formation as early as 2 weeks after injection of MDA PCa 2b cells in the bone of severe combined immunodeficient disease mice. In vitro, we show that PMOs induce MDA PCa 2b proliferation, suggesting a synergistic paracrine loop between these cells and PMOs. Endothelin (ET)-1, which is a mitogen for several cell types, is produced by all prostate cancer cell lines tested, and Atrasentan, an antagonist of ET-1 receptor A, partially reversed PMO proliferation induced by MDA PCa 2b cells. ET-1 is known to be comitogenic with a number of growth factors, including insulin-like growth factor (IGF)-I. In this study, we report that IGF-binding protein (IGFBP)-3 transcripts (that regulate levels of free IGF) are down-regulated in prostate cancer cells cocultured with PMO, whereas prostate-specific antigen (a protease known to cleave IGFBP-3) is detected in the 150-400 ng/ml range. Accordingly, IGFBP-3 has antiproliferative effects in PMOs, which were attenuated in our in vitro system. Taken together, our studies also implicate the IGF axis to play a role in this model of bone metastases. Secondly, the transcript level of mouse double minute 2 (a protein that regulate p53) was increased in prostate cancer cells grown with PMOs. The p53-dependent and -independent oncogenic activities of mouse double minute 2 suggest that osteoblasts induce a survival advantage in prostate cancer cells. Lastly, we show that expression of osteoprotegerin is decreased and of receptor activator of nuclear factor-kappaB ligand is increased in PMOs cultured in the presence of MDA PCa 2b cells, two events associated with osteoclast activation and bone resorption. CONCLUSIONS: Our results provide evidence that multiple and distinct molecular events affecting both bone formation and bone resorption concur to the increase bone mass in prostate cancer bone metastases. These data also provide a rationale for developing therapeutic strategies designed to target these molecular changes.
Subject(s)
Glycoproteins/biosynthesis , Osteoblasts/metabolism , Prostatic Neoplasms/metabolism , Prostatic Neoplasms/pathology , Receptors, Cytoplasmic and Nuclear/biosynthesis , Alkaline Phosphatase/metabolism , Animals , Blotting, Northern , Carrier Proteins/metabolism , Cell Differentiation , Cell Division , Cell Line, Tumor , Cell Survival , Coculture Techniques , Culture Media, Conditioned/pharmacology , DNA/metabolism , DNA, Complementary/metabolism , Down-Regulation , Humans , Insulin-Like Growth Factor Binding Protein 3/metabolism , Insulin-Like Growth Factor I/metabolism , Male , Membrane Glycoproteins/metabolism , Mice , Mice, SCID , Models, Biological , Neoplasm Metastasis , Oligonucleotide Array Sequence Analysis , Osteoprotegerin , Phenotype , RANK Ligand , RNA/metabolism , RNA, Messenger/metabolism , Receptor Activator of Nuclear Factor-kappa B , Receptors, Tumor Necrosis FactorABSTRACT
Current therapy for advanced prostate cancer is largely based on androgen deprivation and is mostly palliative because all patients eventually relapse with androgen-independent disease. Doxorubicin (Dx), an anthracycline used commonly as a chemotherapeutic agent in relapsed prostate cancer, is a strong inducer of p53 expression and p21(CIP1/WAF1) (p21) transactivation. Previous reports suggest that p21 may have a role in the modulation to chemotherapy-induced apoptosis, prostate cancer progression and androgen regulation. In order to investigate if p21 has a pro-survival role in the response of prostate cancer cells to cellular stress, we exposed two androgen-regulated human prostate cancer cell lines (MDA PCa 2b and LNCaP) to Dx and growth factor withdrawal. We then studied expression of p53 and p21, cell-cycle kinetics and apoptosis. We have found that p53 protein accumulated in a dose- and time-dependent manner after Dx treatment, while p21 expression increased over time with low but decreased with high Dx doses. Apoptosis occurred in parallel with p21 down-modulation. Dx treatment of p53 knockout cells demonstrated that p21 induction was strictly p53 dependent. Reduction of p21 levels in prostate cancer cells with an antisense p21 adenovirus resulted in sensitization to Dx and accelerated onset of apoptosis in response to growth factor withdrawal. The evidence presented here also suggests that caspase activation mediates the apoptosis in this system and supports that p21 may modulate the threshold of apoptosis in prostate cancer. These observations may thus provide implications onto the integration of chemotherapy and androgen ablation.
