The role of PTEN in the progression and survival of prostate cancer

PTEN (phosphatase and tensin homologue deleted on chromosome-10), a dual specificity phosphatase, is a tumor suppressor gene whose inactivation has been associated with many different types of cancer including prostate cancer. Prostate adenocarcinoma is one of the most commonly diagnosed malignancies afflicting the male population in both the United States and Europe. The frequency of PTEN inactivation appears to increase during the progression of prostatic cancer. The physical loss of the PTEN genetic locus in prostate cancer progression has been well characterized, however the molecular implication of this loss of PTEN remains enigmatic. The purpose of this review is to describe the functional role of PTEN in the molecular pathogenesis of prostatic disease. We review the function of PTEN discussing its association with the phosphoinositol 3-kinase (PI3K) and mitogen activated protein kinase (MAPK) signal transduction pathways. Additionally, we discuss the role of PTEN in the regulation of apoptotic pathways involving the anti-apoptotic gene bcl-2 and the pro-apoptotic ligand TRAIL. We also review the mechanisms that can lead to the loss of PTEN function. We describe genetic inactivation including loss of heterozygosity, haploinsufficiency and mutation. We conclude by outlining epigenetic loss including methylation, post-translational modifications and oxidative stress.     

The role of vitamin D and retinoids in controlling prostate cancer progression

Prostate cancer is a leading cause of cancer-related deaths in many countries. Premalignant lesions and invasive cancer occur more frequently in the prostate than in any organ other than the skin. Yet, the incidence of clinically detected prostate cancer is much lower than the histopathological incidence. The slow growth of prostate cancer and the low incidence of clinically manifest disease in some geographical locations or racial/ethnic groups suggest that prostate cancer can be controlled, perhaps by dietary factors. Vitamin D and retinoids have emerged as leading candidates both to prevent and to treat prostate cancer. Many of the activities of these compounds, established from epidemiological studies, research with cell culture and animal models, and clinical trials, are consistent with tumor suppressor effects. However, retinoids may have additional tumor enhancer properties that balance or negate anti-cancer activity. This perhaps explains the overall lack of protective effects of vitamin A compounds against prostate cancer found in epidemiological studies, and the minimal efficacy of retinoids in clinical trials to treat prostate cancer. While current efforts focus on developing strategies to use vitamin D compounds to control prostate cancer, the possibility exists that prostate cancer cells may become resistant to tumor suppressor effects of vitamin D. Analyses of experimental model systems show that prostate cancer cells become less sensitive to vitamin D through loss of receptors or signaling molecules that mediate vitamin D's actions, or through changes in metabolic enzymes that synthesize or degrade vitamin D compounds. The potential promise of exploiting vitamin D to control prostate cancer is tempered by the possibility that prostate cancer, perhaps even at early stages, may develop mechanisms to escape tumor suppressor activities of vitamin D and/or retinoids.     

Serum resistin levels in benign prostate hyperplasia and non-metastatic prostate cancer: possible role in cancer progression

Resistin is a member of adipokine family involved in the regulation of inflammatory reactions and insulin sensitivity. In presented study its possible role in the development of benign prostate hyperplasia and prostate cancer was evaluated. Blood samples and prostate specimens were collected from 26 patients with benign prostate hyperplasia (BPH) and from 42 patients with prostate cancer (PCa) stage pT2 (n=18) and pT3 (n=24). Selected metabolic and biochemical parameters and serum resistin levels were measured and anthropometric measurements were performed as well as tissue immunohistochemistry for resistin. Serum resistin levels did not differ significantly between benign hyperplasia and prostate cancer but in cancer patients there was a trend towards decrease with higher cancer stage. Moreover, serum resistin levels were significantly lower in patients with seminal vesicle invasion in comparison to those without invasion. While in BPH serum resistin levels correlated with insulin resistance, inflammatory status and cortisol, in PCa positive correlation with F/T PSA ratio and cortisol was observed. Tissue immunohistochemistry did not show any differences in staining pattern between benign and neoplastic prostate tissue. We conclude that serum resistin levels do not significantly differ between patients with benign prostate hyperplasia and prostate cancer, but there is a trend towards decrease in resistin serum levels in advanced cancer cases. Key words: Immunohistochemistry, inflammation, insulin resistance, prostate cancer, resistin.     

The role of insulin-like growth factor-II in cancer growth and progression evidenced by the use of ribozymes and prostate cancer progression models.

Towards understanding the IGF system during cancer growth and progression, progressive prostate cancer models, such as SV40 large T antigen immortalized human prostate epithelial cells (P69, M2182, M2205, and M12) and LNCaP sublines (C4, C4-2, and C4-2B4), were used. IGF-II mRNA levels progressively increase as prostate cancer cells become more tumorigenic and metastatic, suggesting that IGF-II contributes in part to prostate cancer progression. The role of IGF-II in cancer cell growth was evaluated in LNCaP, PC3, and M12 prostate cancer cell lines and MCF-7 breast cancer cell line by ribozyme/antisense strategies which were previously shown to suppress endogenous IGF-II expression and cell growth in PC-3 cells [Xu et al., Endocrinol 140 (1999) 2134]. Retroviral mediated transient expression of IGF-II-specific ribozyme (RZ) caused extensive cell death. In stably cloned cell lines, both RZ and mutant ribozyme (MRZ) inhibited cancer cell growth, suggesting that antisense effects of MRZ may be sufficient for cell growth inhibition. These results confirm an important role of IGF-II in cancer cell growth and progression, and support further development of gene therapy targeting IGF-II.     

Integrins in prostate cancer progression

Integrins, which are transmembrane receptors for extracellular matrix proteins, play a key role in cell survival, proliferation, migration, gene expression, and activation of growth factor receptors. Their functions and expression are deregulated in several types of cancer, including prostate cancer. In this article, we review the role of integrins in prostate cancer progression and their potential as therapeutic targets.     

Angiogenesis in prostate cancer: its role in disease progression and possible therapeutic approaches

The interaction between cancer cells and their microenvironment is a promising area for the development of novel therapeutic anti-cancer modalities. The formation of new blood vessels, angiogenesis, is an important step in cancer progression. Angiogenesis is a complex multistep process involving close orchestration of endothelial cells, extracellular matrix, and soluble factors. Essentially every step has been found to be regulated by inducers and inhibitors. Prostate cancer has the ability to produce angiogenic factors such as metalloproteinases, vascular endothelial growth factor, fibroblast growth factor 2, transforming growth factor-beta and cyclooxygenase-2. In several studies in prostate cancer an increased microvessel density is associated with poorer prognosis. On the other hand several endogenous inhibitors of angiogenesis have been described in prostate cancer e.g., angiostatin, endostatin, prostate specific antigen (PSA), thrombospondin-1, interleukin 10, interferons and retinoids. The expanding insight in the process of angiogenesis has resulted in a large number of pharmaceutical agents that have been tested in preclinical studies and are currently tested in clinical trials. These agents inhibit endothelial cell proliferation or migration and induce apoptosis. This ultimately will affect the formation of new vessels thereby inducing tumor dormancy. Because antiangiogenic treatment is cytostatic rather than cytotoxic, patients will need long-term therapy to prevent regrowth of the tumor. Prostate cancer is an ideal tumor for antiangiogenic studies because of the availability of a reliable tumor marker, PSA, the indolent clinical course of this cancer and the low rate of proliferation even in metastatic sites. Furthermore, clinical studies showed limited side effects, which is advantageous in this elderly patient group. Whether the ultimate antiangiogenic treatment is effective as a single agent or in combination with radiation therapy, chemotherapy or immunotherapy remains to be determined.     

The role of chromosome 8p22 deletion for predicting disease progression and pathological staging in prostate cancer

The natural course of human prostate cancer is highly variable, and we still lack reliable tools to predict the patient's outcome. Recent publications suggest that the deletion of chromosome 8p22 has an important role for tumor progression in prostate cancer. Totally, 97 patients (41 Japanese and 56 Swedish) were studied to detect the status of chromosome 8p22 deletion by the fluorescence in situ hybridization (FISH) technique. Seventy-seven underwent surgery (59 radical prostatectomies or 18 lymph node dissections), and the specimens were prepared by touch biopsy. Fine-needle aspiration biopsies (FNAB) were obtained from another non-operative 20 cases. Disease progression was evaluated in 57 patients with a median follow-up of 59 months. 8p22 deletions were detected in 58 (60 %) of all cases. The frequency of 8p22 deletion did not significantly differ between different preparations of specimens (touch biopsy vs. FNAB) as well as between different races (Japanese vs. Swedish). Cases with more than pT3 tumors had a significantly higher frequency of 8p22 deletion than those with pT2 (p < 0.01). Multivariate analysis demonstrated that 8p22 deletion was the strongest parameter to predict disease progression (hazard ratio = 5.75; p = 0.0001). Studies on chromosomal deletions of 8p22 by the FISH technique may serve as a universal genetic marker to optimize the treatment strategy in patients with prostate cancer.     

The role of chemotherapy in advanced prostate cancer

The development of hormone resistance is an unfortunate final common pathway in most patients with advanced prostate cancer, resulting in a narrowing of therapeutic options for the clinician, and limited median survival of 10-12 months for the patient. While cytotoxic chemotherapy has been utilized for many years, its efficacy has been disappointing. Quality of life assessments are increasingly used in assessing response in hormone-resistant prostate cancer (HRPC), and PSA has emerged as an important surrogate marker of response in both local and advanced disease. Estramustine and the taxanes have been investigated, as monotherapy and in combination, in the treatment of HRPC in phase 2 and 3 clinical trials, a number of which are ongoing. Substantial advances in the management of HRPC over the past decade have led to renewed optimism that improvement in survival can be achieved, and support the belief that chemotherapy plays a role in this pursuit. In tandem with the development of new agents, refined means of assessing response have been developed, and represent a key component of new research strategies in HRPC.     

Role of neuroendocrine cells in prostate cancer progression

Neuroendocrine (NE) cells represent the third epithelial cell type on normal prostatic tissue (in addition to basal and secretory cells). They are localized in all regions of the human prostate at birth but rapidly decrease in the peripheral prostate after birth, and then reappear at puberty. After puberty, their number seems to increase until an apparently optimum level is reached, which persists between the age of 25 and 54. NE cells were defined by Pearse as APUD to refer to chemical characteristics of amine precursor uptake and decarboxylation, common to the cells of this system. The most predominant product of prostatic NE cells is Chromogranin A, but they also produce serotonin, CgB, secretogranin or CgC, thyroid-stimulating hormone-like peptide, calcitonin, katacalcin, PTHrP and a-human chorionic gonadotropin-like peptide. NE cells in normal and neoplastic prostates are devoid of androgen receptors, but they express epidermal growth factor (EGF) receptor and c-erbB-2. For these reason NE cells are androgen-insensitive. The NE component of prostate adenocarcinoma is resistant to hormone therapy; some studies showed that the number of NE tumor cells and CgA serum levels increase with the recovery of human prostate tumor from hormonal therapy. Currently there are no clinical data available to support an active role of radiotherapy in NE differentiation.     

The role of inhibins and activins in prostate cancer pathogenesis

Successful prostate cancer diagnosis and management continue to provide challenges for the clinician. While interventions aimed at the containment of both early and late disease continue to fail in a significant number of patients, the search for answers must incorporate an analysis of the processes of normal and aberrant growth and development within the gland itself. Inhibin and its structurally related protein, activin, are members of the transforming-growth-factor beta (TGFbeta) superfamily. Originally identified as regulators of FSH, these proteins are now recognised to have widespread biological functions. This might be expected of proteins that are structurally homologous to TGFbeta itself, which is recognised to have regulatory roles in both normal and malignant prostate tissue. The aim of this review is to examine the relationship between inhibins, activins and their related proteins and the development of prostate cancer. The homology with TGF, the pluripotent effects of activin on various tissues and the roles for inhibins in ovarian cancer make activins and inhibins candidate growth factors for involvement at multiple sites in the progression from benign disease to cancer. In compiling this review, we aim to delineate the changes in inhibins and activins in this pathway and in doing so implicate their potential roles in the progression of carcinogenesis. We will compare the changes in inhibin and its related proteins in prostate cancer to those that are known in ovarian cancer. We will discuss the similarities and differences between the putative role of activins and TGFbeta in prostate carcinogenesis. The importance of this review lies in demonstrating that inhibin, an endocrine hormone, and its related proteins may contribute to endocrine-related cancers, such as that of the prostate gland.     

The role of chemotherapy in prostate cancer. Minireview

Hormonal therapy in disseminated prostate cancer is effective in 70-80% of patients and prolongs their lives of a mean 1-2 years. Sooner or later, androgen independence develops due to a multifactorial mechanism. A smaller part of patients may respond to second-line hormonal manipulations (antiandrogen withdrawal, adrenal enzymes synthesis inhibitors, corticosteroids). In hormone-refractory disease only about 30% of patients would respond to chemotherapy. In the standard chemotherapy the mostly used cytotoxic agents are anthracyclines, platinum derivatives, vinca alkaloids and cyclophosphamide. However, combined chemotherapy is not more effective than monotherapy. Conventional chemotherapy may improve especially the quality of life. The median survival in chemotherapy patients (6-12 months) is not significantly longer when compared with the best supportive care. In recent years the main concern has been focused on new cytotoxic drugs and different combinations with hormonal agents. In Phase II studies the combinations of estramustine with oral etoposide, estramustine with taxanes and alternating weekly regimens (doxorubicin, ketoconazole/estramustine, vinblastine) show higher response rates (53-69% of patients with prostate-specific antigen decline of more than 50%) and longer survival (13-19 months) than conventional chemotherapy.     

AGR2蛋白在前列腺癌组织中的表达及意义

目的探讨AGR2蛋白在前列腺癌组织中的表达及意义。方法利用Real-time RT-PCR、RT-PCR和免疫组织化学方法检测AGR2在不同的细胞系以及前列腺癌组织中的表达。结果 AGR2的表达与前列腺癌的进展呈正相关。结论 AGR2蛋白可作为前列腺癌进展诊断的候选分子标志物。     

The role of prostate specific antigen measurement in the detection and management of prostate cancer

The introduction of prostate specific antigen (PSA) testing has revolutionised the early detection, management and follow-up of patients with prostate cancer and it is considered to be one of the best biomedical markers currently available in the field of oncology. Its use with annual digital rectal examination in prostate cancer screening programmes has led to a marked change in the distribution of stage at presentation towards earlier disease and led to a significant increase in the detection of potentially curable disease. In order to improve the specificity of PSA testing and thereby reduce the number of unnecessary prostatic biopsies, a number of refinements of PSA evaluation have been proposed. These include free to total PSA ratio, PSA density, PSA density, PSA density of the transition zone, PSA velocity and age-specific PSA reference ranges. The utility of these approaches is considered in this review. The role of PSA monitoring in the detection of recurrence following radical prostatectomy and radiotherapy is discussed, as well as its role in monitoring patients treated with endocrine therapy is discussed, as well as its role in monitoring patients treated with endocrine therapy in terms of correlating PSA response with outcome, in detecting disease progression and in guiding the use of subsequent therapies. Large continuing multicentre screening and outcome studies will provide important information enabling greater refinement of the use of this important diagnostic and monitoring tool in the future detection and management of prostate cancer.     

The role of SPARC expression in pancreatic cancer progression and patient survival

Abstract

Background. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that has been implicated in tumor–stroma interactions in pancreatic cancer. Here we evaluated the expression of SPARC during the progression of pancreatic cancer and its correlation with survival following curative intent surgery. Methods. The expression profile of SPARC was investigated in normal pancreas, invasive adenocarcinoma, and lymph node metastasis by immunohistochemistry. Kaplan–Meier and multivariate Cox regression were used to assess for mortality risk. Results. None (0%) of 10 normal pancreata, 68 (77%) of 88 primary tumors, and 28 (67%) of 42 lymph node metastases were labeled with the SPARC antibody used in this study. SPARC was expressed exclusively in stromal cells. The survival of patients with high stromal SPARC expression was significantly worse than that of the patients with low stromal SPARC expression (11.5 vs 25.3 months; p = 0.020). Multivariate analysis showed that stromal SPARC expression (hazard ratio (HR) 2.12; p = 0.012), tumor location (body/tail) (HR 2.95; p = 0.003), and adjuvant chemotherapy (HR 0.55; p = 0.018) were significant independent risk factors. Conclusion. This study describes the pattern of SPARC expression in pancreatic neoplastic progression and supports the role of stromal SPARC expression as a prognostic factor and target for directed therapy.     

肿瘤微环境在胰腺癌研究中的进展

肿瘤微环境是决定肿瘤细胞行为的主要影响因素.胰腺癌肿瘤微环境能促进肿瘤生长、侵袭,保护其免受免疫系统的攻击.此文主要介绍了胰腺癌肿瘤微环境的主要组成部分及其各组成部分之间的相互作用,并阐述微环境中一些重要的蛋白酶、生长因子的作用.     

Mechanisms of prostate cancer progression to androgen independence

Prostate cancer is a major health problem in the United States and worldwide. In 2007, more than 27,000 men were estimated to have died from prostate cancer in the United States alone. Although important advances have been made in the diagnosis and treatment of prostate cancer, therapies focused on the removal or inhibition of androgen action remain the most important components of therapy for individuals with metastatic disease. Despite the application of such modalities, the vast majority of patients with metastatic disease progress with a median survival of less than 2 years. A number of different mechanisms have been identified that may potentially contribute to the progression of prostate cancer. These insights suggest that signaling via the androgen receptor (AR) -- either via alternate signaling pathways impinging on the AR or through the in situ formation of androgens within progressive tumors -- is an important contributor to such progressive disease. It is anticipated that such mechanistic insights will lead to the development of useful new therapies in the future.     

The emerging role of diffusion-weighted MRI in prostate cancer management

A significant amount of research has focused on the role of diffusion-weighted MRI (DW-MRI) in the management of patients with prostate cancer. Although uncertainties remain, a clearer picture of where this technique fits into clinical practice is now available. A combination of DW-MRI and T2-weighted MRI (T2W-MRI) demonstrates improved accuracy for lesion detection and localization compared with T2W-MRI alone, and has been suggested as a tool to guide tissue biopsy. DW-MRI could also have roles in active surveillance, evaluating treatment efficacy, and predicting disease recurrence. Furthermore, DW-MRI offers the exciting possibility of gathering information about tumor characteristics and aggressiveness in a noninvasive manner. Validation in large prospective multicenter trials is critical if this technique is to be integrated into current management algorithms for prostate cancer.