Bone-marker levels in patients with prostate cancer: potential correlations with outcomes

Bone Biomarkers and Subsequent Survival in Men with Hormone-sensitive Prostate Cancer: Results from the SWOG S1216 Phase 3 Trial of Androgen Deprivation Therapy with or Without Orteronel

BACKGROUND

Bone biomarkers are strongly prognostic for overall survival (OS) in men with castration-resistant prostate cancer but not fully established for hormone-sensitive prostate cancer (HSPC).

OBJECTIVE

Bone biomarkers in HSPC were prospectively evaluated as part of a phase 3 study of androgen deprivation therapy ± the CYP17 inhibitor orteronel.

DESIGN, SETTING, AND PARTICIPANTS

Patients were randomly divided into training (n = 316) and validation (n = 633) sets. Recursive partitioning and Cox proportional hazard models were employed.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Bone resorption (C-telopeptide and pyridinoline) and bone formation markers (C-terminal collagen propeptide and bone alkaline phosphatase) were assessed from patient sera.

RESULTS AND LIMITATIONS

Of 1279 men, 949 had evaluable baseline bone biomarkers. Optimal cutoffs were identified to define elevated levels of each of the four biomarkers (all p < 0.05) that were associated with worse OS. After adjusting for clinical risk factors in the validation set, elevated bone biomarkers were statistically significantly associated with an increased risk of death (hazard ratios ranging from 1.37 to 1.92). Recursive partitioning algorithms applied to the training set identified three risk groups (low, intermediate, and poor) with differential OS outcomes (median OS: 8.2, 5.1, and 2.1 yr, respectively) based on combinations of bone biomarkers. These results were confirmed in the validation set.

CONCLUSIONS

In men with HSPC initiating androgen deprivation therapy, bone biomarkers are strongly and independently prognostic for OS. Bone biomarker levels alone or in combination with clinical covariates identify unique subsets of men with differential OS outcomes. These results validate the clinical value of bone biomarker assessment in the HSPC state, extending bone biomarker utility beyond the castration-resistant state.

PATIENT SUMMARY

In men with newly diagnosed metastatic prostate cancer, high levels of bone turnover biomarkers are associated with a shorter lifespan.

Bone Metastases and Health in Prostate Cancer: From Pathophysiology to Clinical Implications

Clinically relevant bone metastases are a major cause of morbidity and mortality for prostate cancer patients. Distinct phenotypes are described: osteoblastic, the more common osteolytic and mixed. A molecular classification has been also proposed. Bone metastases start with the tropism of cancer cells to the bone through different multi-step tumor-host interactions, as described by the "metastatic cascade" model. Understanding these mechanisms, although far from being fully elucidated, could offer several potential targets for prevention and therapy. Moreover, the prognosis of patients is markedly influenced by skeletal-related events. They can be correlated not only with bone metastases, but also with "bad" bone health. There is a close correlation between osteoporosis-a skeletal disorder with decreased bone mass and qualitative alterations-and prostate cancer, in particular when treated with androgen deprivation therapy, a milestone in its treatment. Systemic treatments for prostate cancer, especially with the newest options, have improved the survival and quality of life of patients with respect to skeletal-related events; however, all patients should be evaluated for "bone health" and osteoporotic risk, both in the presence and in the absence of bone metastases. Treatment with bone-targeted therapies should be evaluated even in the absence of bone metastases, as described in special guidelines and according to a multidisciplinary evaluation.

Bufalin suppresses the migration and invasion of prostate cancer cells through HOTAIR, the sponge of miR-520b

Bufalin, the major active component of the traditional Chinese medicine ChanSu obtained from the skin and parotid venom glands of toads, has long been known as an anticancer agent. Recent studies show that microRNAs (miRs) are involved in the anticancer activities of bufalin, while long non-coding RNAs (lncRNAs) are known to interact with miRNAs to regulate various biological functions. In this paper, we investigated the possible network related to the antimetastatic effect of bufalin in prostate cancer (PCa) cells. We demonstrated that bufalin (0.05-10 µM) dose-dependently suppressed the proliferation of prostate cancer DU145 and PC3 cells with IC50 values of 0.89 and 1.28 µM, respectively. Furthermore, bufalin treatment significantly suppressed the cell migration and invasion. To explore the role of lncRNAs in the antimetastatic activity of bufalin, we used an lncRNA microarray and found that HOX transcript antisense RNA (HOTAIR) was the most markedly downregulated lncRNA in bufalin-treated PCa cells. Overexpression of HOTAIR counteracted the suppressing effects of bufalin on DU145 and PC3 cells. We then predicted and verified that HOTAIR upregulated FGFR1 expression by sponging miR-520b in PCa cells. In 40 patients with PCa bone metastasis, we used in situ hybridization or immunohistochemical assay to assess the HOTAIR and FGFR1 expression, which revealed that both HOTAIR and FGFR1 expression were significantly higher in bone metastasis tissues than in the primary PCa tissues. In addition, the level of serum HOTAIR was positively associated with the levels of serum bone metabolic markers (CTx, OST, B-ALP and PINP) and may serve as a reasonable biomarker for PCa bone metastasis. Taken together, this is the first study revealing that HOTAIR promotes PCa bone metastasis, and bufalin may be a promising candidate for the treatment of this disease.

The Usefulness of Bone Biomarkers for Monitoring Treatment Disease: A Comparative Study in Osteolytic and Osteosclerotic Bone Metastasis Models

BACKGROUND: The skeleton is the most common site of colonization by metastatic cancers. Zoledronic acid (ZA) has been shown to be effective for the treatment of bone metastases regardless of whether the bone lesions are osteolytic or osteoblastic. Biochemical markers of bone turnover may be useful tools to quantify the degree of bone remodeling in the presence of bone metastases. The aim of this work was to establish the correlation between tumor dispersion (bioluminescence) and biochemical markers of bone turnover in two osteolytic and osteoblastic metastasis models in mice. METHODS: The A549M1 cell line that produces osteolytic metastases and the LADOB cell line extracted from a patient with a lung carcinoma and osteoblastic metastases cells were retrovirally transduced with a luciferase reporter gene for in vivo image analysis. Forty-four-week–old mice were inoculated in the left cardiac ventricle with A549M1 or LADOB cells. Twenty mouse of each group were treated with a single dose of ZA (70 μg/kg) 5 days after i.c. Ten animals of each group were sacrificed at 21 and 28 days postinoculation in A549M1 and 60 and 75 days in the LADOB assay. Bioluminescence analysis was quantified 7, 14, 21 ,and 28 days postinoculation in A549M1 mice and 33, 45, 60, and 75 days after inoculation in LADOB mice. Osteocalcin (BGP), aminoterminal propeptide of procollagen I (PINP), carboxiterminal telopeptide of type I collagen (CTX), and 5b isoenzyme of tartrate-resistant acid phosphatase were measured by ELISA (IDS, UK). RESULTS: Bioluminescence imaging revealed a significant increase of tumor burden on time in both osteolytic and osteoblastic mice models. ZA administration resulted in a significant decrease in tumor burden at 21 and 28 days in the A549M1 animals and 60 and 70 days postinoculation in the LADOB line. Biomarkers levels were significantly increased in the untreated group at every point in the osteolytic model. In the osteoblastic model, 2 months after inoculation, all biomarkers were significantly increased. However, 2.5 months postinoculation, only PINP and CTX were significantly increased. Serum bone remodeling markers decreased in ZA-treated mice as compared with tumor groups in both models. With respect to the correlation between bone turnover markers and tumor burden, in the osteolytic model, PINP and BGP demonstrate a strong correlation with bioluminescence in both tumoral and ZA animals, and only CTX was significantly associated with bioluminescence in the group of animals that were not treated with ZA. CONCLUSIONS: We found that the best biomarkers for the diagnosis of both osteolytic and osteoblastic metastasis are formation markers, especially BGP. Moreover, these markers can be useful in the follow-up of the treatment with ZA in both types of metastasis.

The Present and Future of Biomarkers in Prostate Cancer: Proteomics, Genomics, and Immunology Advancements

Prostate cancer (PC) is the second most common form of cancer in men worldwide. Biomarkers have emerged as essential tools for treatment and assessment since the variability of disease behavior, the cost and diversity of treatments, and the related impairment of quality of life have given rise to a need for a personalized approach. High-throughput technology platforms in proteomics and genomics have accelerated the development of biomarkers. Furthermore, recent successes of several new agents in PC, including immunotherapy, have stimulated the search for predictors of response and resistance and have improved the understanding of the biological mechanisms at work. This review provides an overview of currently established biomarkers in PC, as well as a selection of the most promising biomarkers within these particular fields of development.

Prostate cancer and bone: the elective affinities

The onset of metastases dramatically changes the prognosis of prostate cancer patients, determining increased morbidity and a drastic fall in survival expectancy. Bone is a common site of metastases in few types of cancer, and it represents the most frequent metastatic site in prostate cancer. Of note, the prevalence of tumor relapse to the bone appears to be increasing over the years, likely due to a longer overall survival of prostate cancer patients. Bone tropism represents an intriguing challenge for researchers also because the preference of prostate cancer cells for the bone is the result of a sequential series of targetable molecular events. Many factors have been associated with the peculiar ability of prostate cancer cells to migrate in bone marrow and to determine mixed osteoblastic/osteolytic lesions. As anticipated by the success of current targeted therapy aimed to block bone resorption, a better understanding of molecular affinity between prostate cancer and bone microenvironment will permit us to cure bone metastasis and to improve prognosis of prostate cancer patients.

LRP5 knockdown: effect on prostate cancer invasion growth and skeletal metastasis in vitro and in vivo

Prostate cancer (PCa) is a common hormone-dependent malignancy associated with the development of skeletal metastases. This is due to the increased expression of a number of growth factors, cytokines, and proteases which collectively drive the metastatic cascade in general and increased propensity to develop skeletal metastasis in particular. While a number of signaling pathways have been implicated in PCa progression, the highly complex wnt/β-catenin pathway is unique due to its ability to regulate gene expression, cell invasion, migration, survival, proliferation, and differentiation to contribute in the initiation and progression of PCa. Members of the wnt family bind to the Frizzle proteins or lipoprotein-related receptor proteins 5, 6 (LRP5, -6) to activate this key pathway. In the current study, we have investigated the role of wnt/β-catenin pathway in PCa progression, skeletal metastasis, and gene expression using the dominant negative plasmid of LRP5 (DN-LRP5) and human PCa cells PC-3. Inactivation of LRP5 resulted in mesenchymal to epithelial shift, lack of translocation of β-catenin to cell surface, increased tumor cell proliferation, decreased colony formation, migration and invasion in vitro. These effects were attributed to decreased expression of pro-invasive and pro-metastatic genes. In in vivo studies, PC-3-DN-LRP5 cells developed significantly smaller tumors and a marked decrease in skeletal lesion area and number as determined by X-ray, micro (μ) CT and histological analysis. Collectively results from these studies demonstrate the dominant role of this key pathway in PCa growth and skeletal metastasis and its potential as a viable therapeutic target.

Pathobiology and management of prostate cancer-induced bone pain: recent insights and future treatments

Prostate cancer (PCa) has a high propensity for metastasis to bone. Despite the availability of multiple treatment options for relief of PCa-induced bone pain (PCIBP), satisfactory relief of intractable pain in patients with advanced bony metastases is challenging for the clinicians because currently available analgesic drugs are often limited by poor efficacy and/or dose-limiting side effects. Rodent models developed in the past decade show that the pathobiology of PCIBP comprises elements of inflammatory, neuropathic and ischemic pain arising from ectopic sprouting and sensitization of sensory nerve fibres within PCa-invaded bones. In addition, at the cellular level, PCIBP is underpinned by dynamic cross talk between metastatic PCa cells, cellular components of the bone matrix, factors associated with the bone microenvironment as well as peripheral components of the somatosensory system. These insights are aligned with the clinical management of PCIBP involving use of a multimodal treatment approach comprising analgesic agents (opioids, NSAIDs), radiotherapy, radioisotopes, cancer chemotherapy agents and bisphosphonates. However, a major drawback of most rodent models of PCIBP is their short-term applicability due to ethical concerns. Thus, it has been difficult to gain insight into the mal(adaptive) neuroplastic changes occurring at multiple levels of the somatosensory system that likely contribute to intractable pain at the advanced stages of metastatic disease. Specifically, the functional responsiveness of noxious circuitry as well as the neurochemical signature of a broad array of pro-hyperalgesic mediators in the dorsal root ganglia and spinal cord of rodent models of PCIBP is relatively poorly characterized. Hence, recent work from our laboratory to develop a protocol for an optimized rat model of PCIBP will enable these knowledge gaps to be addressed as well as identification of novel targets for drug discovery programs aimed at producing new analgesics for the improved relief of intractable PCIBP.

Molecular classification of prostate cancer progression: foundation for marker-driven treatment of prostate cancer

Recently, many therapeutic agents for prostate cancer have been approved that target the androgen receptor and/or the prostate tumor microenvironment. Each of these therapies has modestly increased patient survival. A better understanding of when in the course of prostate cancer progression specific therapies should be applied, and of what biomarkers would indicate when resistance arises, would almost certainly improve survival due to these therapies. Thus, applying the armamentarium of therapeutic agents in the right sequences in the right combination at the right time is a major goal in prostate cancer treatment. For this to occur, an understanding of prostate cancer evolution during progression is required. In this review, we discuss the current understanding of prostate cancer progression, but challenge the prevailing view by proposing a new model of prostate cancer progression, with the goal of improving biologic classification and treatment strategies. We use this model to discuss how integrating clinical and basic understanding of prostate cancer will lead to better implementation of molecularly targeted therapeutics and improve patient survival.

Clinical usefulness of bone markers in prostate cancer with bone metastasis

Bone metastases occur in approximately 70% of patients with advanced prostate cancer. Skeletal-related events have been correlated with reduced survival and quality of life of patients with prostate cancer. Biochemical markers of bone metabolism (e.g. bone formation, bone resorption, osteoclastogenesis) might meet an unmet need for useful, non-invasive and sensitive surrogate information for following patients' skeletal health. Recently, zoledronic acid and denosumab have been proven to have the potential for preventing skeletal-related events among prostate cancer patients with bone metastasis. An improved understanding of the mechanisms underlying bone metastasis has also led to the recognition of multiple molecular targets and advances in therapy. However, estimating the efficacy of these agents is difficult. A clinical trial for castration-resistant prostate cancer is currently underway based on the definition of The Prostate Cancer Clinical Trials Working Group, and bone turnover markers are being used as conventional end-points for the clinical trial. Bone turnover markers are useful surrogate markers reflecting the effect of new therapeutic drugs and prognosis, as well as assessment of bone metastases. In particular, N-terminal cross-linked telopeptide of type 1 collagen and bone-specific alkaline phosphatase are widely used bone metabolism markers, and offer reliable surrogate markers to detect bone metastatic spread and to predict prognosis for prostate cancer patients with bone metastases.

BMP4 promotes prostate tumor growth in bone through osteogenesis

Induction of new bone formation is frequently seen in the bone lesions from prostate cancer. However, whether osteogenesis is necessary for prostate tumor growth in bone is unknown. Recently, 2 xenografts, MDA-PCa-118b and MDA-PCa-133, were generated from prostate cancer bone metastases. When implanted subcutaneously in severe combined immunodeficient (SCID) mice, MDA-PCa-118b induced strong ectopic bone formation while MDA-PCa-133 did not. To identify the factors that are involved in bone formation, we compared the expression of secreted factors (secretome) from MDA-PCa-118b and MDA-PCa-133 by cytokine array. We found that the osteogenic MDA-PCa-118b xenograft expressed higher levels of bone morphogenetic protein BMP4 and several cytokines including interleukin-8, growth-related protein (GRO), and CCL2. We showed that BMP4 secreted from MDA-PCa-118b contributed to about a third of the osteogenic differentiation seen in MDA-PCa-118b tumors. The conditioned media from MDA-PCa-118b induced a higher level of osteoblast differentiation, which was significantly reduced by treatment with BMP4 neutralizing antibody or the small molecule BMP receptor 1 inhibitor LDN-193189. BMP4 did not elicit an autocrine effect on MDA-PCa-118b, which expressed low to undetectable levels of BMP receptors. Treatment of SCID mice bearing MDA-PCa-118b tumors with LDN-193189 significantly reduced tumor growth. Thus, these studies support a role of BMP4-mediated osteogenesis in the progression of prostate cancer in bone.

Characterization of a rat model of metastatic prostate cancer bone pain

PURPOSE

The objectives of this study were to establish and characterize a novel animal model of metastatic prostate cancer-induced bone pain.

METHODS

Copenhagen rats were injected with 10(6) MATLyLu (MLL) prostate cancer cells or phosphate-buffered saline by per cutaneous intra femoral injections into the right hind leg distal epiphysis. Over 13 days, rats progressively developed a tumor within the distal femoral epiphysis. On days 3, 7, 10, and 13 post injection, rats were subjected to the incapacitance and Randall-Selitto behavioral tests as they are believed to be indirect reflections of tumor induced pain. Ipsilateral hind limbs were subjected to X-ray and computed tomography (CT) scans and histological sections were stained with hematoxylin and eosin (H&E).

RESULTS

Intra femoral injections of MLL cells resulted in the progressive development of a tumor leading to bone destruction and nociceptive behaviors. Tumor development resulted in the redistribution of weight to the contralateral hind leg and significantly reduced the paw withdrawal threshold of the ipsilateral hind paw as observed via the incapacitance and Randall-Selitto tests, respectively. X-ray and computed tomography scans along with H&E stains indicated tumor-associated structural damage to the distal femur. This model was challenged with administration of meloxicam. Compared with vehicle-injected controls, the meloxicam-treated rats displayed smaller nociceptive responses as observed with the incapacitance and Randall-Selitto tests, suggesting that meloxicam was effective in reducing the pain-related symptoms displayed by model animals and that the model behaved in a predictable way to cyclooxygenase-2 treatment.

CONCLUSIONS

This model is unique from other bone cancer models in that it is a comprehensive model utilizing a competent immune system with a syngeneic tumor. The model establishes a tool that will be useful to investigate mechanisms of cancer pain that are induced by cancer cells.