Prognostic significance of plasma chromogranin a levels in patients with hormone-refractory prostate cancer treated in Cancer and Leukemia Group B 9480 study

New circulating biomarkers for prostate cancer

The introduction of prostate-specific antigen (PSA) revolutionized prostate cancer (PCa) screening and ushered the PSA era. However, its use as a screening tool remains controversial and changes in the epidemiology of PCa have strongly limited its prognostic role. Therefore, we need novel approaches to improve our ability to detect PCa and foretell the course of the disease. To improve the specificity of total PSA, several approaches based on PSA derivatives have been investigated such as age-specific values, PSA density (PSAD), PSAD of the transition zone, PSA velocity and assessment of various isoforms of PSA. With recent advances in biotechnology such as high-throughput molecular analyses, many potential blood biomarkers have been identified and are currently under investigation. Given the plethora of candidate PCa biomarkers, we have chosen to discuss a select group of candidate blood-based biomarkers including human glandular kallikrein, early prostate cancer antigens, insulin-like growth factor-I (IGF-I) and its binding proteins (IGFBP-2 and IGFBP-3), urokinase plasminogen activation system, transforming growth factor-beta1, interleukin-6, chromogranin A, prostate secretory protein, prostate-specific membrane antigen, PCa-specific autoantibodies and alpha-methylacyl-CoA racemase. While these and other markers have shown promise in early phase studies, no single biomarker is likely to have the appropriate degree of certainty to dictate treatment decisions. Consequently, the future of cancer prognosis may rely on small panels of markers that can accurately predict PCa presence, stage, metastasis, and serve as prognosticators, targets and/or surrogate end points of disease progression and response to therapy.

New blood-based biomarkers for the diagnosis, staging and prognosis of prostate cancer

The introduction of prostate-specific antigen (PSA) has revolutionized the detection and management of patients with prostate cancer. Despite this there has always been a concern among clinicians about the usefulness of total PSA levels as a marker for prostate cancer. We discuss the use of calculated variables and molecular forms of PSA. The precursor forms of PSA have been associated with the presence and biological behaviour of prostate cancer. With recent advances in biotechnology, e.g. high-throughput molecular analyses, many potential blood biomarkers have been identified and are currently under investigation. Given the plethora of candidate biomarkers we discuss a selected group of novel blood-based biomarkers, e.g. human glandular kallikrein, early prostate cancer antigen, insulin-like growth factors, urokinase plasminogen activators, transforming growth factor-beta, interleukin-6, chromogranin A, and prostate secretory protein. While these and other markers have shown promise in early-phase studies, no single biomarker is likely to have the appropriate degree of certainty to dictate treatment decisions. Consequently, the future of cancer prognosis might rely on small panels of markers that can accurately predict cancer presence, stage and metastasis, and serve as prognosticators, targets, and/or surrogate endpoints of disease progression and response to therapy.

Localization of immunoreactive HIF-1alpha and HIF-2alpha in neuroendocrine cells of both benign and malignant prostate glands

BACKGROUND

Hypoxia induces increased tumor growth by promoting angiogenic and glycolytic pathways. Tumors expressing hypoxia-inducible factor-1alpha (HIF-1alpha), an important transcriptional activator of oxygen-regulated genes, are resistant to chemotherapy and radiotherapy. The major challenge in prostate cancer therapy today is to gain a better understanding of the development of hormone-refractory tumors, which is often characterized by neuroendocrine differentiation. Here we studied the expression of HIF-1alpha and HIF-2alpha in neuroendocrine cells of the benign prostate and in prostate cancer.

METHODS

Tissue sections from 30 patients who underwent radical prostatectomy and from 21 patients operated by transurethral resection of the prostate were selected for immunohistochemical analysis for expression of HIF-1alpha, HIF-2alpha, androgen receptor (AR), neuroendocrine markers (chromogranin A, synaptophysin), and two gene products downstream of HIF-1alpha: VEGF and GAPDH.

RESULTS

Immunoreactive HIF-1alpha was detected in a subpopulation of AR-negative neuroendocrine cells in benign and malignant prostate tissue. Analysis of serial sections showed that the levels of expression of GAPDH and VEGF proteins are increased in AR-negative malignant neuroendocrine cells expressing HIF-1alpha. In situ-hybridization indicated that HIF-1alpha mRNA levels are not higher in neuroendocrine prostate cancer cells relative to corresponding non-neuroendocrine tumor cells. We also demonstrated induced stabilization of nuclear HIF-1alpha in LNCaP cells by hypoxia and long-term stimulation with interleukin-6. Focal HIF-2 expression was detected in benign neuroendocrine-like cells and in malignant prostatic cells.

CONCLUSIONS

The expression of HIF-1alpha and HIF-2alpha in prostate cancer has been confirmed, but we also identified immunoreactive HIF-1alpha and downstream gene products in benign and malignant prostate neuroendocrine cells.

Chromogranin A expression in patients with hormone naïve prostate cancer predicts the development of hormone refractory disease

PURPOSE

We assessed chromogranin A as a tissue biomarker in prostate needle biopsies or as a plasma biomarker, a risk factor for hormone refractory prostate cancer.

MATERIALS AND METHODS

A total of 211 patients with newly diagnosed prostate cancer treated with luteinizing hormone releasing hormone analogues constituted the study cohort. Univariate and multivariate Cox regression analyses were used to assess the predictive role of tissue and plasma chromogranin A expression.

RESULTS

Chromogranin A expression in less than 30% or in 30% or more tumor cells was significantly associated with a shorter time to hormone refractory disease on univariate analysis (HR 2.0, 95% CI 1.3-3.1 and HR 6.0, 95% CI 2.7-12.9), or on multivariate analysis after adjusting for Gleason score, serum prostate specific antigen and disease stage (HR 1.7, 95% CI 1.0-2.8 and HR 3.9, 95% CI 1.7-9.0), respectively. Plasma chromogranin A measured at baseline (HR 3.0, 95% CI 1.8-5.2), and after 1 year (HR 5.8, 95% CI 3.1-10.1) and 2 years (HR 3.5, 95% CI 1.6-7.6), was predictive of hormone refractory risk confirming the tissue results. Plasma as well as tissue chromogranin A expression negatively correlated with overall survival.

CONCLUSIONS

Chromogranin A expression in prostate cancer biopsies is an independent predictive factor of hormone refractory disease in patients with newly diagnosed prostate cancer on early androgen deprivation therapy. Plasma chromogranin A is also a reliable predictive marker and the predictive significance is maintained over time. These results deserve validation in another data set.

Secretagogin is a new neuroendocrine marker in the human prostate

BACKGROUND

Neuroendocrine (NE) differentiation in prostate cancer (PCa), promoted by NE cell secreted products, appears to be associated with tumor progression, poor prognosis, and hormone-refractory disease. We recently reported secretagogin, a hexa-EF-hand Ca(2+) binding protein, as a novel NE marker in carcinoid tumors of the lung and the gastrointestinal tract. The present study analyzes the expression of secretagogin in normal and malign prostate tissue.

METHODS

We analyzed immunoreactivity for secretagogin, chromogranin A (CgA), neuron specific enolase (NSE), and synaptophysin (SYN) in consecutive sections from 87 formalin-fixed paraffin-embedded (FFPE) benign hyperplastic (n = 10) and prostate adenocarcinoma (n = 77) specimens. The intracellular distribution of secretagogin, CgA, and NSE was examined by confocal fluorescent microscopy, and we characterized secretagogin in eight samples by Western blotting.

RESULTS

Secretagogin is cytoplasmic and nuclear expressed in NE and NE differentiated cells, and to a lesser extent in epithelial cells, in the benign prostate and prostate adenocarcinoma cells. Secretagogin stained 82% (46/56) of benign and 71% (48/68) of prostate adenocarcinomas and co-localized with the NE markers CgA and NSE. The expression of secretagogin is significantly correlated to CgA (P < 0.001) and NSE (P < 0.048) in prostate adenocarcinoma and to CgA in normal epithelium (P < 0.028).

CONCLUSIONS

Secretagogin is a novel NE marker in the prostate with more extended immunoreactivity compared to the NE markers CgA, SYN, and NSE. Secretagogin is widely expressed in prostatic adenocarcinoma as opposed to adenocarcinomas in other organs.

Is there a role for platinum chemotherapy in the treatment of patients with hormone-refractory prostate cancer?

Docetaxel chemotherapy is the current standard of care for metastatic hormone-refractory prostate cancer (HRPC). Platinum chemotherapy drugs, such as cisplatin and carboplatin, have moderate single-agent activity in HRPC. Next-generation platinum drugs, including satraplatin and oxaliplatin, may have additional activity in the management of HRPC. Furthermore, neuroendocrine differentiation may play a role in disease progression, providing a rationale for platinum-based chemotherapy in the management of HRPC. The authors reviewed the MEDLINE database for reports related to platinum-based chemotherapy in patients with advanced prostate cancer and evaluated studies that reviewed the role of neuroendocrine differentiation in the progression of HRPC. Older studies from the 1970s and 1980s suggested a lack of activity of cisplatin and carboplatin; however, those studies were flawed at least in part by their methods of response assessment. More recent Phase II studies of carboplatin suggested a moderate level of clinical and palliative activity when it was used as a single agent. However, when carboplatin was combined with a taxane and estramustine, high response rates were observed in several recent clinical trials. In addition, a randomized trial suggested that satraplatin plus prednisone improved progression-free survival compared with prednisone alone. For patients who progressed after docetaxel, no standard options existed in the literature that was reviewed. Several preliminary reports suggested that carboplatin and oxaliplatin may have activity as second-line chemotherapy. Platinum chemotherapy drugs historically have been considered inactive in HRPC, although a review of the data suggested otherwise. Carboplatin, in particular, induced very high response rates when it was combined with estramustine and a taxane, but it also appeared to have activity in patients who progressed after docetaxel. Satraplatin plus prednisone is being investigated in a large Phase III trial as second-line chemotherapy for HRPC. Targeting neuroendocrine cells may provide a new therapeutic approach to HRPC.

Comparison between two commercially available chromogranin A assays in detecting neuroendocrine differentiation in prostate cancer and benign prostate hyperplasia

BACKGROUND

Chromogranin A (CgA) is the neuroendocrine (NE) marker most frequently employed in detecting NE differentiation in prostate cancer patients, either at the tissue level or in the general circulation.

METHODS

We compared the two commercially CgA assay kits in detecting NE differentiation, in benign hyperplasia (BPH) or prostate cancer (PC) patients (pts). 170 pts with BPH, 107 with BPH+inflammation, and 136 PC pts entered the study. CgA was measured in each patient with the immunoradiometric assay (IRMA) and with the enzyme-linked immunoabsorbent assay (ELISA).

RESULTS

A moderate relationship was found between CgA measured with IRMA and ELISA in the whole population (Spearman's R=0.65, p<0.05), in BPH pts (R=0.76, p<0.05), in BPH+inflammation pts (R=0.53, p<0.05) and in PC pts (R=0.60, p<0.05). Twenty-two out of 62 pts (35.4%) with elevated ELISA CgA did not have increased IRMA CgA; by contrast, 21/61 pts (34.4%) with elevated IRMA CgA were not recognized as abnormal by the ELISA kit.

CONCLUSIONS

CgA measured by the two assays provided a significant discordance rate, suggesting that the two kits might elicit different information.

The Case for Early Chemotherapy for the Treatment of Metastatic Disease

PURPOSE

Several important questions are raised by the data from Southwest Oncology Group 99-16 and TAX 327. What is the optimal timing of chemotherapy for metastatic hormone refractory prostate cancer? Should asymptomatic patients be treated? Is there a theoretical survival advantage for treatment for hormone sensitive prostate cancer? We reviewed arguments for the early use of docetaxel in the hormone sensitive and hormone naïve disease states.

MATERIALS AND METHODS

Androgen independent prostate cancer was traditionally viewed as a chemoresistant disease. At best palliation of bone pain but not improved survival could be achieved with the combination of mitoxantrone and prednisone. Median survival rates for chemotherapy in this disease state were reported to be between 10 and 12 months. Phase II studies administering docetaxel weekly or every 3 weeks as a single agent or in combination with estramustine demonstrated median survival rates of 14 to 23 months, which appeared to be an improvement over standard therapy. Consequently the 2 randomized trials, Southwest Oncology Group 99-16 and TAX 327, were designed to confirm the preliminary observations of improved survival with docetaxel based therapy.

RESULTS

TAX 327 and Southwest Oncology Group 99-16 treated asymptomatic as well as symptomatic patients. Thus, in contrast with mitoxantrone/prednisone, which was approved in symptomatic men with hormone refractory prostate cancer, the exact timing of the initiation of chemotherapy in docetaxel treated patients is still the subject of debate.

CONCLUSIONS

Studies should be performed to investigate the optimal timing of chemotherapy as well as sequencing with androgen ablation in patients at high risk for progression and death from metastatic prostate cancer. Prognostic factors for death that have been identified in patients with androgen independent prostate cancer are hemoglobin, alkaline phosphatase, visceral disease and performance status.

Molecular markers of prostate cancer

Although prostate-specific antigen (PSA) has evolved as a very useful tool for detection of prostate cancer, there remains an urgent need for more accurate biomarkers to diagnose prostate cancer and predict cancer-related outcomes. Recent advances in the study of proteomics and high throughput techniques have led to the discovery of many potential biomarkers for prostate cancer. This article briefly reviews the current status of PSA testing and discusses several candidate protein biomarkers for prostate cancer, as well as highlighting some recent proteomic discoveries with the potential to supplement or even replace PSA for the diagnosis and prognosis of prostate cancer.

Clinical implications of neuroendocrine differentiation in prostate cancer

The cellular signaling pathways of the prostate play a central role in the induction, maintenance, and progression of prostate cancer (CaP). Neuroendocrine (NE) cells demonstrate attributes that suggest they are an integral part of these signaling cascades. We summarize what is known regarding NE cells in CaP focusing on NE cellular transdifferentiation. This significant event in CaP progression appears to be accelerated by androgen deprivation (AD) treatment. We examine biochemical pathways that may impact NE differentiation in a chronological manner focusing on AD therapy (ADT) as a central event in inducing androgen-independent CaP. Our analysis is limited to the common adenocarcinoma pattern of CaP and excludes small-cell and carcinoid prostatic variants. In conclusion, we speculate on the future of treatment and research in this area.

Activities and accomplishments of the cancer and leukemia group B genitourinary committee

The Cancer and Leukemia Group B Genitourinary (GU) Committee has developed a multidisciplinary approach to treatment of GU cancer and has integrated correlative science research into the major research themes of the GU Committee. In localized prostate cancer, trials have evaluated novel approaches in radiation therapy. For patients with recurrence after local therapy, a trial evaluating local recurrence with salvage prostatectomy and a study of systemic therapy with "peripheral androgen blockade" were undertaken. Major contributions have been made in developing and testing therapeutics for advanced, androgen-independent prostate cancer (ketoconazole, suramin, estramustine/docetaxel, and docetaxel/bevacizumab), and in developing predictive markers and algorithms to assess prognosis in these patients. Contributions in kidney cancer have included the development of novel trial methodology, such as the randomized discontinuation trial design, and the testing of antiangiogenics. In addition to these areas, future work of the committee will include further development of therapy for earlier-stage prostate cancer patients and bladder cancer patients.