Advances in prostate cancer

Enhancing the utility of prostascint SPECT scans for patient management

This project investigated reducing the artifact content of In-ill ProstaScint SPECT scans for use in treatment planning and management. Forty-one patients who had undergone CT or MRI scans and simultaneous Tc-99m RBC/In-111 ProstaScint SPECT scans were included. SPECT volume sets, reconstructed using Ordered Set-Expectation Maximum (OS-EM) were compared against those reconstructed with standard Filtered Back projection (FBP). Bladder activity in Tc-99m scans was suppressed within an ellipsoidal volume. Tc-99m voxel values were subtracted from the corresponding In-111 after scaling based on peak activity within the descending aorta. The SPECT volume data sets were merged with the CT or MRI scans before and after processing. Volume merging, based both on visual assessment and statistical evaluation, was not affected. Thus iterative reconstruction together with bladder suppression and blood pool subtraction may improve the interpretation and utility of ProstaScint SPECT scans for patient management.

Transcriptional activation of the human prostatic acid phosphatase gene by NF-kappaB via a novel hexanucleotide-binding site

Human prostatic acid phosphatase (PAcP) is a prostate epithelium-specific differentiation antigen. Cellular PAcP functions as a neutral protein tyrosine phosphatase and is involved in regulating androgen-promoted prostate cancer cell proliferation. Despite the fact that the promoter of the PAcP gene has been cloned, the transcriptional factors that regulate PAcP expression remain unidentified. This article describes our analyses of the promoter of the PAcP gene. Deletion analyses of the promoter sequence up to -4893 (-4893/+87) revealed that a 577 bp fragment (-1356/-779) represents the unique positive cis-active element in human prostate cancer cells but not in HeLa cervix carcinoma cells. Interestingly, the 577 bp fragment contains a non-consensus nuclear factor kappaB (NF-kappaB)-binding site that is required for NF-kappaB up-regulation in prostate cancer cells, while NF-kappaB failed to have the same effect in HeLa cells. Conversely, inhibition of the NF-kappaB pathway stopped p65 NF-kappaB activation of the p1356 promoter activity. Gel shift and mutation analyses determined that AGGTGT (-1254/-1249) is the core sequence for NF-kappaB-binding and activation. Biologically, tumor necrosis factor-alpha (TNF-alpha) activated endogenous PAcP expression in LNCaP human prostate cancer cells. The data collectively indicate that NF-kappaB up-regulates PAcP promoter activity via its binding to the AGGTGT motif, a novel binding sequence located inside the cis-active enhancer element in human prostate cancer cells.

Inverse association between prostate cancer and the use of calcium channel blockers

Calcium channel blockers block calcium signal-mediated apoptosis. It is hypothesized that the use of these drugs may be associated with the development of cancer. This study investigated the association between daily use of calcium channel blockers and prostate cancer in a community-based cohort of men who participated in a longitudinal study of lower urinary tract symptoms. Study subjects were men ages 40 to 79 years by January 1, 1990, and were randomly selected from Olmsted County in Minnesota. At baseline, participants underwent an interview to determine all medications taken on a daily basis, including calcium channel blockers and to elicit a family history of prostate cancer. During follow-up, all men with a histological diagnosis of prostate cancer were identified through patient self-report and by a review of the complete medical record. Over 12,668 person years of follow-up, 15 (6.8%) of 220 calcium channel blocker users and 120 (10.5%) of 1142 nonusers developed prostate cancer (P = 0.09; odds ratio, 0.62; 95% confidence interval, 0.36-1.10). With adjustment for age and family history of prostate cancer, the risk (odds ratio, 95% confidence interval) of prostate cancer was 0.55 (0.31-0.97) in calcium channel blocker users compared with nonusers. In analyses stratified by family history of prostate cancer, the risk of prostate cancer was 0.45 (0.23-0.88) in men without a family history and 2.64 (0.82-8.47) in men with a family history of prostate cancer (P = 0.006). These findings suggest an association between prostate cancer and daily use of calcium channel blockers that varies by family history of prostate cancer.

Differences in the epidemic rise and decrease of prostate cancer among geographical areas in Southern Europe. an analysis of differential trends in incidence and mortality in France, Italy and Spain

This is a population-based study aimed at evaluating incidence and mortality trends for prostate cancer in France, Italy and Spain, during the prostate-specific antigen (PSA) era, considering elderly people aged 70 years and over and younger adults aged between 40 and 69 years. Trends were estimated by a log-linear Poisson regression model and expressed as an Estimated Annual Percent Change (EAPC). Incidence increased sharply in almost all areas. Spain showed the lowest increases. Incidence started to rise around 1985 in France and after 1990 in Italy and Spain. Mortality increased until the late 1980s in all countries, then declined in France and Italy (-2.5% in 40-69 year age group), but not in Spain. Younger people showed a much higher rise in incidence than the elderly, while mortality decreased mainly in the younger adults. The decrease in mortality was more marked in those areas and the younger age group where the rise in incidence was higher and started earlier, i.e. in France and in younger people, suggesting that the PSA test may have had a positive effect on mortality, although other clinical advances also have to be taken into account.

Prostate-specific antigen vaccines for prostate cancer

Prostate cancer is the most common malignant tumour in men and there are few treatment options available once the tumour becomes refractory to hormonal manipulation. Prostate-specific antigen (PSA) is a secretory glycoprotein that is commonly expressed by prostatic epithelial cells and is found in elevated levels in the serum of men with prostate cancer. The identification of T cell specific epitopes within the coding sequence of PSA has led to the development of various vaccine strategies that target PSA in an attempt to treat established prostate cancer. These strategies have included human leukocyte antigen-restricted PSA peptides, dendritic cells pulsed with PSA, recombinant viruses expressing PSA and combinations of different vectors. In addition to PSA, several other antigens have been described that may be useful for targeting prostate tumours by vaccines. Animal studies have established the feasibility and safety for many of these agents and clinical trials are now in progress to evaluate the immunological and clinical responses of PSA vaccines. Further research in manipulating anti-PSA immunity with cytokines, costimulatory molecules and other immune modulating agents will likely improve the therapeutic effectiveness of PSA vaccines. Clinical trials designed to evaluate the effects of vaccination in different stages of disease and through different routes of administration need to be performed to define the optimal schedule for PSA vaccines in patients with prostate cancer, or for those at high risk of developing the disease.

Green tea and prostate cancer

Many laboratory studies and human epidemiological data suggest that most prostate cancer deaths are attributable to lifestyle, including nutritional factors where diet plays a major role in initiation as well as subsequent progression of the disease. Under these circumstances, chemoprevention seems to be a logical and obvious strategy. Because of its long latency and high incidence, prostate cancer is an ideal disease for chemoprevention. The suitable agent(s) for prostate cancer chemoprevention should be the one(s) that has efficacy in the laboratory experiments on one hand, and also possesses proven epidemiological basis on the other hand. In this article, we address the use of green tea for prostate cancer chemoprevention. Experimental as well as the epidemiological basis for this possibility is provided.

Induction of immune responses and safety profiles in rhesus macaques immunized with a DNA vaccine expressing human prostate specific antigen

Prostate specific antigen (PSA) is a widely used marker for prostate cancer, which is secreted by normal prostate cells at low levels, but is produced more substantially by cancer cells. We have previously reported on the use of a DNA vaccine construct that encodes for human PSA gene to elicit host immune responses against cells producing PSA. DNA immunization strategy delivers DNA constructs encoding for a specific immunogen into the host, who becomes the in vivo protein source for the production of antigen. This antigen then is the focus of the resulting immune response. In this study, we examine the induction of immune responses and safety profiles in rhesus macaques immunized with DNA-based PSA vaccine. We observed induction of PSA-specific humoral response as well as positive PSA-specific lymphoproliferative (LPA) response in the vaccinated macaques. We also observed that the stimulated T cells from the PSA-immunized rhesus macaques produced higher levels of Th1 type cytokine IFN-gamma than the control vector immunized animals. On the other hand, DNA immunization did not result in any adverse effects in the immunized macaques, as indicated by complete blood counts, leukocyte differentials and hepatic and renal chemistries. The macaques appeared healthy, without any physical signs of toxicity throughout the observation period. In addition, we did not observe any adverse effect on the vaccination site. The apparent safety and immunogenecity of DNA immunization in this study suggest that further evaluation of this vaccination strategy is warranted.

PDEF, a novel prostate epithelium-specific ets transcription factor, interacts with the androgen receptor and activates prostate-specific antigen gene expression

Prostate cancer, the most frequent solid cancer in older men, is a leading cause of cancer deaths. Although proliferation and differentiation of normal prostate epithelia and the initial growth of prostate cancer cells are androgen-dependent, prostate cancers ultimately become androgen-independent and refractory to hormone therapy. The prostate-specific antigen (PSA) gene has been widely used as a diagnostic indicator for androgen-dependent and -independent prostate cancer. Androgen-induced and prostate epithelium-specific PSA expression is regulated by a proximal promoter and an upstream enhancer via several androgen receptor binding sites. However, little progress has been made in identifying androgen-independent regulatory elements involved in PSA gene regulation. We report the isolation of a novel, prostate epithelium-specific Ets transcription factor, PDEF (prostate-derived Ets factor), that among the Ets family uniquely prefers binding to a GGAT rather than a GGAA core. PDEF acts as an androgen-independent transcriptional activator of the PSA promoter. PDEF also directly interacts with the DNA binding domain of androgen receptor and enhances androgen-mediated activation of the PSA promoter. Our results, as well as the critical roles of other Ets factors in cellular differentiation and tumorigenesis, strongly suggest that PDEF is an important regulator of prostate gland and/or prostate cancer development.