Human prostatic carcinoma cells produce an increase in the synthesis of interleukin-6 by human osteoblasts

Genetic analysis of high bone mass cases from the BARCOS cohort of Spanish postmenopausal women

The aims of the study were to establish the prevalence of high bone mass (HBM) in a cohort of Spanish postmenopausal women (BARCOS) and to assess the contribution of LRP5 and DKK1 mutations and of common bone mineral density (BMD) variants to a HBM phenotype. Furthermore, we describe the expression of several osteoblast-specific and Wnt-pathway genes in primary osteoblasts from two HBM cases. A 0.6% of individuals (10/1600) displayed Z-scores in the HBM range (sum Z-score >4). While no mutation in the relevant exons of LRP5 was detected, a rare missense change in DKK1 was found (p.Y74F), which cosegregated with the phenotype in a small pedigree. Fifty-five BMD SNPs from Estrada et al. [NatGenet 44:491-501,2012] were genotyped in the HBM cases to obtain risk scores for each individual. In this small group of samples, Z-scores were found inversely related to risk scores, suggestive of a polygenic etiology. There was a single exception, which may be explained by a rare penetrant genetic variant, counterbalancing the additive effect of the risk alleles. The expression analysis in primary osteoblasts from two HBM cases and five controls suggested that IL6R, DLX3, TWIST1 and PPARG are negatively related to Z-score. One HBM case presented with high levels of RUNX2, while the other displayed very low SOX6. In conclusion, we provide evidence of lack of LRP5 mutations and of a putative HBM-causing mutation in DKK1. Additionally, we present SNP genotyping and expression results that suggest additive effects of several genes for HBM.

Prognostic impact of C-reactive protein for determining overall survival of patients with castration-resistant prostate cancer treated with docetaxel

OBJECTIVE

To verify the prognostic impact of C-reactive protein (CRP) for patients with castration-resistant prostate cancer (CRPC) treated with docetaxel in a single institution.

METHODS

A group of 80 consecutive patients with CRPC were treated with docetaxel in our institution from January 2005 to May 2010. The patients received 75 mg/m(2) of docetaxel intravenously every 3 weeks. The prognostic value of all covariables, including CRP, was assessed using the Cox proportional hazard model. Risk stratification for overall survival was described from the results of the multivariable analysis.

RESULTS

The median survival period for all patients was 14.5 months. The multivariable analysis showed that CRP and hemoglobin levels were independent prognostic factors for overall survival. Based on the presence of an elevated CRP concentration and/or a low hemoglobin level, all patients were stratified into 3 risk groups: those with no risk factors (low-risk group), those with 1 risk factor (intermediate-risk group), and those with 2 risk factors (high-risk group). The overall survival curves were clearly tiered according to the risk groups, with the 1-year overall survival rates being 86.3%, 60.5%, and 23.0% for the low-, intermediate-, and high-risk groups, respectively (P <.001).

CONCLUSION

CRP is an independent prognostic factor for overall survival of patients with CRPC treated with docetaxel. Risk stratification based on CRP and hemoglobin could be helpful for estimating the overall survival.

Mechanisms of persistent activation of the androgen receptor in CRPC: recent advances and future perspectives

BACKGROUND

The emergence of castration resistance has remained the primary obstacle in prostate cancer therapy for several decades. Mechanisms likely to be involved in castration-resistant progression have been studied extensively, but have failed to yield many meaningful and effective targets. The re-activation of the androgen receptor (AR) in castration-resistant prostate cancer (CRPC) is now recognized as the central event in this process, and therapeutic modalities are being devised to combat it.

METHODS

A review of literature was performed to highlight the important factors that play a role in the aberrant activation of the AR in CRPC.

RESULTS

Seminal and exciting advances made in the past few years in the discovery of the roles of new intrinsic factors such as intracrine androgens, gene fusions involving the ETS oncogenes, and splice variants of the AR are reviewed. New and emerging hypotheses about the involvement of factors such as cytokines and other signaling pathways are discussed.

CONCLUSIONS

This review summarizes the most recent advances in the persistent activation of the androgen receptor signaling pathway and provides a perspective about their significance in CRPC progression.

Enhancement of osteoclastogenic activity in osteolytic prostate cancer cells by physical contact with osteoblasts

BACKGROUND

The interaction between prostate cancer cells and osteoblasts is critical for the development of bone metastasis. Metastatic cancer cells may physically contact osteoblasts in the bone microenvironment; however, the biological significance of this interaction is not fully understood.

METHODS

Human prostate cancer cells (the osteolytic cell line PC-3 and the osteoblastic cell line MDA-PCa 2b) and human osteoblasts (hFOB1.19) were cocultured under two different conditions (bilayer and contact conditions). Differential gene expression profiles of prostate cancer cells were then investigated using microarray analysis. Differentially expressed genes were analysed using RT-PCR and western blotting, and the effect of anti-cadherin neutralising antibodies on their expression was assayed. The osteoclastogenic activity of cells grown under these different conditions was also investigated using an in vitro assay.

RESULTS

When PC-3 or MDA-PCa 2b cells were cocultured with hFOB1.19 cells under contact conditions, the expression of eight genes was upregulated and that of one gene was downregulated in PC-3 cells compared with gene expression in bilayer culture. No differentially expressed genes were detected in MDA-PCa 2b cells. Four of the eight upregulated genes (interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), IL-6 and the third component of complement (C3)) have already been reported to participate in osteoclastogenesis. Indeed, a cell lysate of PC-3 cells grown under contact coculture conditions significantly enhanced osteoclastogenesis in vitro (P<0.005). neutralisation of cadherin-11 with a specific antibody inhibited upregulation of COX-2 and C3 mRNA in PC-3 cells. In contrast, neutralisation of N-cadherin induced upregulation of COX-2 mRNA.

CONCLUSION

Physical contact between osteolytic prostate cancer cells and osteoblasts may upregulate osteoclastogenesis-related gene expression in prostate cancer cells and enhance osteoclastogenesis. Additionally, cadherin-11 and N-cadherin are involved in this process. These data provide evidence supporting new therapies of prostate cancer bone metastasis that target direct cancer-cell-osteoblast cell-cell contact.

Effect of IL-1beta, PGE(2), and TGF-beta1 on the expression of OPG and RANKL in normal and osteoporotic primary human osteoblasts

The RANKL/RANK/OPG pathway is essential for bone remodeling regulation. Many hormones and cytokines are involved in regulating gene expression in most of the pathway components. Moreover, any deregulation of this pathway can alter bone metabolism, resulting in loss or gain of bone mass. Whether osteoblasts from osteoporotic and nonosteoporotic patients respond differently to cytokines is unknown. The aim of this study was to compare the effect of interleukin (IL)-1beta, proftaglandin E(2) (PGE(2)), and transforming growth factor-beta1 (TGF-beta1) treatments on OPG and RANKL gene expression in normal (n = 11) and osteoporotic (n = 8) primary osteoblasts. OPG and RANKL mRNA levels of primary human osteoblastic (hOB) cell cultures were assessed by real-time PCR. In all cultures, OPG mRNA increased significantly in response to IL-1beta treatment and decreased in response to TGF-beta1 whereas PGE(2) treatment had no effect. RANKL mRNA levels were significantly increased by all treatments. Differences in OPG and RANKL responses were observed between osteoporotic and nonosteoporotic hOB: in osteoporotic hOB, the OPG response to IL-1beta treatment was up to three times lower (P = 0.009), whereas that of RANKL response to TGF-beta1 was five times higher (P = 0.002) after 8 h of treatment, as compared with those in nonosteoporotic hOBs. In conclusion, osteoporotic hOB cells showed an anomalous response under cytokine stimulation, consistent with an enhanced osteoclastogenesis resulting in high levels of bone resorption.

Amino-terminus domain of the androgen receptor as a molecular target to prevent the hormonal progression of prostate cancer

Prostate cancer has a propensity to metastasize to the bone. Currently the only effective systemic treatment for these patients is androgen ablation therapy. However, the tumor will invariably progress to an androgen-independent stage and the patient will succumb to his disease within approximately 2 years. The earliest indication of hormonal progression is the rising titer of serum prostate specific antigen. Current evidence implicates the androgen receptor (AR) as a key factor in maintaining the growth of prostate cancer cells in an androgen-depleted state. Under normal conditions, binding of ligand activates the receptor, allowing it to effectively bind to its respective DNA element. However, AR is also transformed in the absence of androgen (ligand-independent activation) in prostate cells via multiple protein kinase pathways and the interleukin-6 (IL-6) pathway that converge upon the N-terminal domain of the AR. This domain is the main region for phosphorylation and is also critical for normal coregulator recruitment. Here we discuss evidence supporting the role of the AR, IL-6 and other protein kinase pathways in the hormonal progression of prostate cancer to androgen independence and the mechanisms involved in activation of the AR by these pathways. Receptor-targeted therapy, especially potential drugs targeting the N-terminal domain, may effectively prevent or delay the hormonal progression of AR-dependent prostate cancer.

Heparanase promotes bone destruction and invasiveness in prostate cancer

Heparanase is an endoglycosidase that plays an important role in angiogenesis and metastasis of cancer. Herein we evaluate the effect of heparanase overexpression on invasiveness and bone destruction in prostate cancer bone metastases. The human prostate cancer cell line PC-3 was stably transfected with a plasmid containing the cDNA for human heparanase or with the vector alone as a control. Overexpression of heparanase did not affect the growth of PC-3 cells, but did promote invasiveness of the cells in an in vitro assay. Both cell types were injected into the tibias of nude mice. Four weeks later, the mice were examined radiologically prior to sacrifice and samples of leg tissue were taken to investigate bone destruction and metastasis. Mice injected with PC-3 cells overexpressing heparanase had more severe bone destruction and larger, more invasive, tumors. These results demonstrate that heparanase overexpression can facilitate tumor invasion and accelerate bone destruction caused by prostate cancer bone metastasis.

A phase II trial of bortezomib and prednisone for castration resistant metastatic prostate cancer

PURPOSE

We defined the antitumor effects of bortezomib alone and in combination with prednisone in patients with progressive, castration resistant metastatic prostate cancer.

MATERIALS AND METHODS

A total of 30 men with progressive castration resistant disease were treated in 2 groups. Cohort 1 received 1.5 mg/m2 bortezomib intravenously twice weekly for 2 cycles (2 weeks on and 1 week off), followed by 1.6 mg/m2 weekly (4 weeks on and 2 weeks off). Prednisone (10 mg) was given orally throughout. Cohort 2 comprised patients with limited chemotherapy exposure who received a decreased dose of bortezomib (1.3 mg/m2) during the induction period with prednisone added only at disease progression. The primary end point was no evidence of disease progression at 12 weeks, defined as no increase in prostate specific antigen from baseline and no radiographic progression. Interleukin-6 was assessed to correlate with antitumor effects.

RESULTS

One of 24 evaluable patients (4%) achieved the primary end point. In cohort 1, 18 patients were treated, 13 were evaluable for response and 4 discontinued treatment due to toxicities, including 3 before attaining the point of being evaluable. No patient achieved the primary end point. In cohort 2, 12 patients were treated and 11 were evaluable for response. Toxicity was slightly mitigated compared with that in cohort 1. One patient achieved the primary end point. Interleukin-6 did not correlate with posttreatment prostate specific antigen changes in either cohort.

CONCLUSIONS

Although interleukin-6 and other pathways regulated by nuclear factor-kappa B may be legitimate targets, treatment with bortezomib alone and with prednisone does not appear to have significant antitumor effects in patients with castration resistant metastatic prostate cancer.

Apoptosis evasion: the role of survival pathways in prostate cancer progression and therapeutic resistance

The ability of a tumor cell population to grow exponentially represents an imbalance between cellular proliferation and cellular attrition. There is an overwhelming body of evidence suggesting the ability of tumor cells to avoid programmed cellular attrition, or apoptosis, is a major molecular force driving the progression of human tumors. Apoptotic evasion represents one of the true hallmarks of cancer and appears to be a vital component in the immunogenic, chemotherapeutic, and radiotherapeutic resistance that characterizes the most aggressive of human cancers [Hanahan and Weinberg, 2000]. The challenges in the development of effective treatment modalities for advanced prostate cancer represent a classic paradigm of the functional significance of anti-apoptotic pathways in the development of therapeutic resistance.

Modulation of survival in osteoblasts from postmenopausal women

Osteoblast survival is one of the determinants of postmenopausal osteoporosis development. Recent data from animal experiments suggest that cytokines, in particular Fas ligand (FasL), contribute to postmenopausal osteoporosis. We now address the effect of Fas activation in postmenopausal osteoblast survival and the potential modulatory effect of estrogen and raloxifene analog (LY117018). The expression of Fas mRNA, Fas protein, and the sensitivity to Fas-induced apoptosis were studied in primary cultures of human osteoblasts from postmenopausal women and in osteoblastic MG-63 cells. Human postmenopausal osteoblasts constitutively expressed Fas receptors in the cell surface. TNFalpha increased the expression of Fas mRNA and cell surface Fas expression. Neither estradiol nor raloxifene analog prevented this increase in Fas expression. In addition, activation of Fas receptor resulted in apoptosis of postmenopausal osteoblasts. While TNFalpha did not induce human osteoblast apoptosis, it did increase the lethal effect of Fas activation. Therapeutic concentrations of estradiol or raloxifene analog did not modulate lethal cytokine-induced apoptosis. Both postmenopausal osteoblasts and MG-63 cells express FasL. FasL expression was not modulated by TNFalpha. In conclusion, estrogen and raloxifene analog do not appear to affect the sensitivity of postmenopausal osteoblasts to Fas-mediated apoptosis.

Phase I trial of the proteasome inhibitor bortezomib in patients with advanced solid tumors with observations in androgen-independent prostate cancer

PURPOSE

To determine the dose-limiting toxicity and maximum-tolerated dose of the proteasome inhibitor bortezomib administered intravenously weekly for 4 every 5 weeks; to determine the bortezomib pharmacokinetics and pharmacodynamics using plasma levels and an assay for 20S proteasome inhibition (PI) in whole blood; to correlate toxicity with bortezomib dose and degree of 20S PI; and to conduct a preliminary determination of the antitumor activity of bortezomib in patients with androgen independent prostate cancer (AIPCa).

PATIENTS AND METHODS

Fifty-three patients (48 with AIPCa) received 128 cycles of bortezomib in doses ranging from 0.13 to 2.0 mg/m(2)/dose, utilizing a careful escalation scheme with a continuous reassessment method. Pharmacokinetic and pharmacodynamic studies were performed in 24 patients (at 1.45 to 2.0 mg/m(2)).

RESULTS

A dose-related 20S PI was seen, with dose-limiting toxicity at 2.0 mg/m(2) (diarrhea, hypotension) occurring at an average 1-hour post-dose of >/= 75% 20S PI. Other side effects were fatigue, hypertension, constipation, nausea, and vomiting. No relationship was seen between body-surface area and bortezomib clearance over the narrow dose range tested. There was evidence of biologic activity (decline in serum prostate-specific antigen and interleukin-6 levels) at >/= 50% 20S PI. Two patients with AIPCa had prostate-specific antigen response and two patients had partial response in lymph nodes.

CONCLUSION

The maximum-tolerated dose and recommended phase II dose of bortezomib in this schedule is 1.6 mg/m(2). Biologic activity (inhibition of nuclear factor-kappa B-related markers) and antitumor activity is seen in AIPCa at tolerated doses of bortezomib. This agent should be further explored with chemotherapy agents in advanced prostate cancer.

Modulation of prostate cancer growth in bone microenvironments

Bone remains one of the major sites, and most lethal host organs, for prostate cancer metastasis. Prostate cell spread and establishment in bone depends on multiple reciprocal modifications of bone stromal and epithelial cancer cell behaviors. This review focuses on recent advances in the characterization of cell-cell and cell-matrix interplay, effects on cell growth, adhesion and invasion, and several therapeutic possibilities for co-targeting prostate cancer cells and bone stroma. We address the topic from three main perspectives: (1) the normal and aging bone stromal environment, (2) the "reactive" bone stromal environment, and (3) the cancerous prostate epithelial cells themselves. First, normal, and especially aging, bones provide uniquely rich and "fertile soil" for roaming cancer cells. The interactions between prostate cancer cells and insoluble extracellular matrices, soluble growth factors, and/or sex steroid hormones trigger bone remodeling, through increased osteoclastogenesis and furthur matrix metalloproteinase activity. Second, after cancer cell arrival and establishment in the bone, host stromal cells respond, becoming "reactive" in a process again involving extracellular matrix remodeling, together with growth factor and steroid receptor signaling this process ultimately enhances cancer cell migration, stromal transdifferentiation, and invasion of the cancer tissues by stromal, inflammatory, and immune-responsive cells. Third, prostate cancer cells also respond to supportive bone microenvironments, where soluble and matrix-associated molecules affect cancer cell growth and gene expression, especially altering cancer cell surface receptor and integrin-mediated cell signaling. We discuss both integrin cell-matrix and gap junctional cell-cell communication between cancer cells and their microenvironments during prostate cancer progression.