Expression of endothelial factors in prostate cancer: a possible role of caveolin-1 for tumour progression

Solid tumours need to induce their own vascular supply, and microvessel density (MVD) has emerged as a prognostic factor in several tumours. We hypothesized that mRNA levels of some endothelial factors in prostate cancer tissue would correlate with histologically measured MVD, or other pathological parameters. Expression levels of the endothelial factors CD31, CD34, CD105, CD144, CD146, CAV1 and VEGFR2 were assessed by RT-qPCR in matched freshly frozen normal and tumour tissues from 69 patients that underwent radical prostatectomy. The results were compared to pathological parameters and the MVD in the corresponding paraffin-embedded material, as determined by immunohistochemistry against CD31 and CD34. Comparing mRNA expression in matched normal and tumour samples, only CAV1 showed relevant differences, being down-regulated in tumour tissues (fold change=-1.89, P<0.0001). CAV1 down-regulation correlated with pT category (P=0.006) and the Gleason score (P=0.041). In a univariate analysis, lower CAV1 mRNA expression was associated with biochemical recurrence (P=0.019). By immunohistochemistry, CAV1 was mainly localized in endothelial and stromal cells and showed a weaker staining pattern in the tumour compared to normal tissue. Furthermore, MVD significantly correlated with tumour grade and pT category. There was no significant association between endothelial mRNA expression and histologically determined MVD in tumour tissues, but only a trend for CD31 mRNA (P=0.074) and an inverse trend for CAV1 mRNA (P=0.056). In conclusion, there is only a weak correlation between the mRNA expression of endothelial factors and MVD in prostatic tumour tissue. However, loss of CAV1 mRNA expression may play a role in prostate cancer progression.     

A possible role of BDNF in prostate cancer detection

Many studies have demonstrated that both normal and malignant prostate cells respond to a variety of growth factors, while several significant differences were found between normal and tumoural cells. The aim of this study was to focus on the localization and distribution of the immuno-reactivity for neurotrophins (NTs) and neurotrophin receptors (NTRs) in normal, hyperplastic and prostate cancer cells, obtained from 40 subjects. We studied samples obtained from 16 prostate cancer (PC, retropubic radical prostatectomy), 20 benign prostatic hyperplasia (BPH, supra-pubic prostatectomy) and normal peripheral prostate tissue from four fresh male cadavers. Samples were examined via immunohistochemical techniques in order to detect the expression of nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3) and their own receptors TrkA, p75, TrkB and TrkC. We observed a high expression of BDNF and TrkB in PC and BPH, though no immuno-reactivity was found for p75. Low expression was reported by other NTs and NTRs in the normal peripheral prostate zone, BPH and PC. These data suggest a possible predictive role for NTs and NTRs, especially for BDNF and TrkB, in the diagnosis and/or management of prostate cancer. The absence of p75 expression confirms its supposed role in apoptotic phenomenon.     

The role of metastasis-associated protein 1 in prostate cancer progression

Distinguishing aggressive prostate cancer from indolent disease represents an important clinical challenge, as current therapy requires over treating men with prostate cancer to prevent the progression of a few cases. Expression of the metastasis-associated protein 1 (MTA1) has previously been found to be associated with progression to the metastatic state in various cancers. Analyzing DNA microarray data, we found MTA1 to be selectively overexpressed in metastatic prostate cancer compared with clinically localized prostate cancer and benign prostate tissue. These results were validated by demonstrating overexpression of MTA1 in metastatic prostate cancer by immunoblot analysis. MTA1 protein expression was evaluated by immunohistochemistry in a broad spectrum of prostate tumors with tissue microarrays containing 1940 tissue cores from 300 cases. Metastatic prostate cancer demonstrated significantly higher mean MTA1 protein expression intensity (score = 3.4/4) and percentage of tissue cores staining positive for MTA1 (83%) compared with clinically localized prostate cancer (score = 2.8/4, 63% positive cores) or benign prostate tissue (score = 1.5/4, 25% positive cores) with a mean difference of 0.54 and 1.84, respectively (P < 0.00001 for both). Paradoxically, for localized disease, higher MTA1 protein expression was associated with lower rates of prostate specific antigen recurrence after radical prostatectomy for localized disease. In summary, this study identified an association of MTA1 expression and prostate cancer progression.     

Nitric oxide-mediated inhibition of androgen receptor activity: possible implications for prostate cancer progression

Chronic inflammation increases the risk of cancer and many cancers, including prostate cancer, arise at sites of chronic inflammation. Inducible nitric oxide synthase (iNOS) is an enzyme dominantly expressed during inflammatory reactions. Although synthesis of high amounts of nitric oxide (NO) by iNOS has been demonstrated in pathophysiological processes, such as acute or chronic inflammation, autoimmune diseases or tumorigenesis, the role of iNOS activity in most of these diseases is poorly understood. Analysing prostate cancer biopsies by immunohistochemistry we found iNOS protein expression in tumor cells strongly paralleled by nitrotyrosine suggesting that iNOS is fully active. In vitro, NO inhibits androgen receptor-dependent promoter activity and prostate specific antigen production as well as DNA-binding activity of the androgen receptor (AR) in a concentration-dependent manner. Inhibition of the activity of androgen receptor-dependent reporter constructs is neither owing to diminished AR protein levels nor owing to an inhibition of its nuclear import. In addition, NO inhibits the proliferation of androgen receptor-positive prostate cancer cells significantly more efficiently than proliferation of androgen receptor-negative prostate cancer cells. In summary, our findings suggest that intratumoral iNOS activity favors development of prostate cancer cells that are able to proliferate androgen receptor-independently, thereby promoting prostate tumor progression.     

Definitive radiotherapy of prostate cancer: the possible role of staging lymphadenectomy

PURPOSE: To evaluate the postradiotherapy 5-year cancer-specific (CSS), clinical progression-free (cPFS), and overall (OS) survival rates in patients with pN0 M0 prostate cancer (PC). METHODS: Between 1989 and 1996, 203 consecutive pN0 M0 PC patients (T1-2, 66; T3-4, 137) received conformal prostatic four-field radiotherapy (median target dose 66 Gy). Any hormone manipulation was delayed until clinical progression (growth of the primary tumor or development of distant metastases). RESULTS: After a median observation time of 87 months (range 11-156), 99 patients had relapsed clinically and 70 patients were dead, 37 of them as a result of prostate cancer. Five-year CSS, cPFS, and OS rates were, respectively, 90% (95% CI 86-94%), 64% (95% CI 57-71%), and 82% (95% CI 77-87%), with no difference of OS compared with age-matched males from the general population. Gleason score (< or =7A vs. > or =7B) and the T category predicted cPFS, whereas CSS was associated with Gleason score only. Preradiotherapy PSA failed to predict survival. Patients with T1-2 Gleason score < or =7A had a 97% 5-year CCS, as compared with 89% for all other patients. A median of eight lymph nodes (range 0-29) were described in the specimens from pelvic lymphadenectomy (LA). CONCLUSION: Despite still preliminary observations, our 5-year results challenge the use of combined hormone radiotherapy in patients who are proven to be pN0 by preradiotherapy LA; in particular, in patients with T1-2/Gleason score < or =7A, whereas the survival in all other patients with pN0 M0 prostate cancer may be improved by adjuvant androgen deprivation.     

Stromal-epithelial interaction in prostate cancer progression

Cancer is not a single-cell disease, and its existence and behavior are constantly modulated by the host. Cancer gene expression and genetics are also highly dynamic and are regulated epigenetically by the host through gene-environment interaction. In this article, we describe the molecular pathways leading to an unusual property of cancer cells: the ability to mimic the host microenvironment and, in particular, the characteristics of osteomimicry and vasculogenic mimicry, which are likely to be regulated by soluble and insoluble factors in the tumor-adjacent microenvironment. We also discuss the importance of host inflammatory and stem cells that contribute to the growth and survival of cancer cells. By understanding the salient features of cancer-host interaction, novel therapeutics might be developed to target the cancer and its host in the treatment of lethal prostate cancer metastases.     

Human prostate cancer cells adhere specifically to hemoglobin: a possible role in bone-specific metastasis

From the supernatant of rabbit bone marrow, we isolated an organ-specific factor, which was related with the metastasis of prostate cancer to the bone and examined its adhesion to prostate cancer cells (PC-3). Molecular weight and amino acid sequence analyses of the active component obtained by high performance liquid chromatography revealed that a component identical to the alpha chain of hemoglobin accounted for 80% of the biological activity. Hemoglobin showed over 50% adhesion to PC-3 cells but only 10% adhesion to human colon cancer cell lines, representative of organ non-specific metastasis, and leukemia cells line, representative of a non-solid tumor. Some substance in the bone marrow may promote the first step of adhesion of cancer cells to bone marrow in the metastasis of prostate cancer to the bone, possibly an amino acid sequence or some tertiary structure similar to hemoglobin.     

Human kallikrein 7 induces epithelial-mesenchymal transition-like changes in prostate carcinoma cells: a role in prostate cancer invasion and progression

Human tissue kallikrein 7 (hK7), a chymotrypsin-like secreted serine protease, catalyzes the degradation of intercellular adhesive structures in the cornified layer of the skin, leading to desquamation. Thus, hK7 is implicated in cancer invasion and metastasis. Although hK7 is highly expressed in prostate tissues, its biological role in prostate cancer progression is poorly understood. In the current study, we established an hK7-expressing cell model for prostate tumors by stably transfecting prostate carcinoma 22RV1 and DU145 cells with an expression vector encoding hK7. We found that there were no obvious differences in cell proliferation between cells overexpressing hK7 and cells transfected with empty vector (p>0.05). Intriguingly, a Matrigel invasion assay revealed that hK7 remarkably increased the migration and invasion of prostate cancer cells (p<0.01). Furthermore, hK7 induced epithelial-mesenchymal transition-like changes in prostate carcinoma cells, as evidenced by scattered cellular growth, mesenchyma-like morphology, and up-regulated expression of vimentin, a mesenchymal marker. These novel findings suggest that hK7 plays an important role in mediating prostate cancer progression and that hK7 promotes invasion and metastasis, at least in part, through inducing the epithelial-mesenchymal transition of prostatic carcinoma cells.     

The Ste20 kinase MST4 plays a role in prostate cancer progression

MST4, a member of the Sterile 20 serine/threonine kinase family, was found to be expressed in prostate carcinoma tumor samples and cell lines. In addition, expression levels appeared to correlate with tumorigenicity and androgen receptor status of the cells. Ectopic expression of wild-type and kinase-inactive MST4 was used to alter cellular MST4 activity levels in three widely studied human prostate tumor cell lines: LNCaP, DU 145, and PC-3. Overexpression of wild-type MST4 induced anchorage-independent growth of the LNCaP cell line, and increased both in vitro proliferation and in vivo tumorigenesis of the DU 145 cell line. On the other hand, expression of a kinase-inactive form reverted the anchorage-independent growth phenotype and highly tumorigenic behavior of the PC-3 cell line. MST4 kinase activity was stimulated significantly by epidermal growth factor receptor ligands, which are known to promote growth of prostate cancer cells. Together, our studies suggest a potential role for MST4 in the signal transduction pathways involved in prostate cancer progression.     

Role of diet in prostate cancer development and progression.

Increasing evidence supports the important role of nutrition in cancer prevention, including prevention of prostate cancer. In this review, we summarize data for some of the most consistently observed dietary associations for prostate cancer incidence, briefly consider possible postdiagnostic effects of nutrition on prostate cancer progression/survival, discuss new but limited data on diet-gene interactions, and comment on current areas of controversy for future research focus. Potential protective dietary elements include tomatoes/lycopene, other carotenoids, cruciferous vegetables, vitamin E, selenium, fish/marine omega-3 fatty acids, soy, isoflavones and polyphenols; whereas milk, dairy, calcium, zinc at high doses, saturated fat, grilled meats, and heterocyclic amines may increase risk. It is important to note that randomized clinical trial data exist only for vitamin E, calcium, beta-carotene, and selenium (all of which suggest inverse or no association). Several genes, such as MnSOD, XRCC1, and GST, may modify the association of specific nutrients and foods with prostate cancer risk; and further research is warranted to confirm these initial observed relationships. Until further clinical trial data are available on specific supplements and prostate cancer prevention, it would be prudent to emphasize a diet consisting of a wide variety of plant-based foods and fish; this is similar to what is recommended (and what is more well established) for the primary prevention of heart disease.     

Osteopontin and interleukin-8 expression is independently associated with prostate cancer recurrence.

PURPOSE: Lack of reliable biomarkers limits accurate prediction of prostate-specific antigen biochemical recurrence (disease progression) in prostate cancer. The two inflammatory chemokines, osteopontin and interleukin-8 (IL-8), are associated with tumor angiogenesis and metastasis. We investigated whether osteopontin and IL-8 expression in prostate cancer correlates with disease progression. EXPERIMENTAL DESIGN: Archival prostatectomy specimens (n = 103) were obtained from patients with minimum 72-month follow-up. Osteopontin and IL-8 expression was evaluated by immunohistochemistry and graded for intensity and the area. Association of osteopontin and IL-8 staining with biochemical recurrence was evaluated by univariate and multivariate models. RESULTS: In tumor cells, osteopontin and IL-8 staining was higher in the recurred group (203.2 +/- 78.4; 181.1 +/- 89.3) than in the nonrecurred group (122.7 +/- 76.6; 96.4 +/- 85.6; P < 0.001). Higher osteopontin and IL-8 staining was also observed in benign areas adjacent to tumor in the recurred group, than in nonrecurred group. In univariate analysis, except age, all preoperative and postoperative variables and osteopontin and IL-8 staining scores were significantly associated with biochemical recurrence (P < 0.05). In multivariate analysis, margin status and osteopontin staining independently associated with biochemical recurrence within 72 months. Osteopontin, either alone or with IL-8 and seminal vesicle invasion, was a significant variable in predicting biochemical recurrence within 24 months. Osteopontin and IL-8 staining predicted recurrence with high sensitivity (75.5%; 73.6%) and specificity (76%; 70.6%). CONCLUSION: In prostatectomy specimens, osteopontin expression is independently associated with biochemical recurrence. Both osteopontin and IL-8 may be predictors of early disease progression.     

Drug insight: role of the androgen receptor in the development and progression of prostate cancer

Functional androgen receptor (AR) signaling is necessary for the development of prostate cancer. The therapeutic effect of androgen deprivation therapy for prostate cancer was described over 60 years ago and this treatment remains the mainstay of systemic therapy despite its transient response duration. It has become clear that AR expression and signaling remains intact as the disease evolves from androgen-sensitive cancer to classically (but perhaps inaccurately) termed hormone refractory prostate cancer. Through several genetic and epigenetic adaptations, prostate tumors continue to rely on AR growth signaling and they thus remain targets of 'hormonal' therapy. The development of new strategies and drugs that can abrogate AR signaling will probably result in important clinical benefits. The biology of androgen independence and the development of new approaches targeting AR signaling are reviewed herein.     

SGEF is overexpressed in prostate cancer and contributes to prostate cancer progression

The purpose of this study was to investigate the potential roles of the SH3-containing guanine nucleotide exchange factor (SGEF) in human prostate cancer. Experimental data showed that SGEF was overexpressed in human prostate cancer cells and specimens. The reduction of SGEF expression through an SGEF-targeting siRNA in androgen-independent C4-2 and C4-2B cells suppressed both anchorage-dependent and anchorage-independent growth. In addition, the androgen receptor (AR) antagonist bicalutamide further strengthened this inhibitory effect due to the suppression of the elevated AR transactivation after knockdown of SGEF. Collectively, our results provide the first demonstration that SGEF is a novel promoter of human prostate cancer progression and development.     

PrLZ is expressed in normal prostate development and in human prostate cancer progression.

PURPOSE: We previously reported the isolation and characterization of PrLZ, a novel prostate-specific and androgen-responsive gene of the tumor protein D52 family at chromosome 8q21.1. PrLZ is the only known gene in this locus with prostate specificity. Expression level of PrLZ was elevated specifically in cancer cells, suggesting its association with malignancy. EXPERIMENTAL DESIGN: To define its biological function in the morphogenesis, development, and functional maturation of the prostate gland and to gain further insight into its role in prostate cancer, we examined PrLZ expression in prostate specimens during early embryonic development and in adult tissue. RESULTS: PrLZ first appears in the nuclei of the prostate epithelia at 16 weeks of gestation before its distribution in the cytoplasm at later ages. Its expression peaks at 24 years of age, declines at 31 years of age, and maintains a minimal level in later age. On prostate cancer development, PrLZ expression is reactivated, and its expression increases from primary localized tumor to bone metastasis. Overexpression of PrLZ in prostate cancer cells accelerates their growth in vitro and tumor formation in vivo. CONCLUSION: This work identifies PrLZ as a marker for prostate cancer progression and metastasis, and its pattern of expression is suggestive of a proto-oncogene.     

The role of an 80 kDa fragment of E-cadherin in the metastatic progression of prostate cancer.

PURPOSE: The purpose of this study was to evaluate an 80 kDa proteolytic fragment of E-cadherin as a potential biomarker for prostate cancer progression and to identify putative proteases that are responsible for the cleavage of E-cadherin. EXPERIMENTAL DESIGN: A wide spectrum of prostate cancer tissue and serum specimens representing different stages of prostate cancer was examined for the accumulation of the 80 kDa fragment of E-cadherin. Additionally, an expression array analysis was used to identify putative proteases that may have been involved in the cleavage of E-cadherin. RESULTS: A reproducible E-cadherin fragment was detected as a strong 80 kDa band in tissue samples. This fragment was detectable almost exclusively in metastatic sites. It was not visible in normal prostate tissue and was weak in 1 of 16 localized prostate cancers. The fragment is shed into the extracellular space and was detectable in patient serum in which the expression of the fragment showed a strong association with advanced prostate cancer. On the basis of cDNA expression analysis, several members of the metalloproteinase family could be identified as potentially responsible for the cleavage of the fragment from full-length E-cadherin. CONCLUSIONS: In this study, we present the first report of serum levels of the 80 kDa fragment of E-cadherin in prostate cancer patients. This fragment is exclusively seen in neoplastic prostate tissue and may represent a useful biomarker of prostate cancer disease progression. This study also demonstrates an association of increased levels of several metalloproteinases with metastatic prostate cancer and could provide a useful correlation between metalloproteinase expression/activity and E-cadherin cleavage and the metastatic progression of prostate cancer.     

Role of eicosanoids in prostate cancer progression

Metabolism of arachidonic acid through cyclooxygenase, lipoxygenase, or P450 epoxygenase pathways leads to the formation of various bioactive eicosanoids. In this review, we discuss alterations in expression pattern of eicosanoid-generating enzymes found during prostate tumor progression and expound upon their involvement in tumor cell proliferation, apoptosis, motility, and tumor angiogenesis. The expression of cyclooxygenase-2, 12-lipoxygenase, and 15-lipoxygenase-l are up-regulated during prostate cancer progression. It has been demonstrated that inhibitors of cyclooxygenase-2, 5-lipoxygenase and 12-lipoxygenase cause tumor cell apoptosis, reduce tumor cell motility and invasiveness, or decrease tumor angiogenesis and growth. The eicosanoid product of 12-lipoxygenase, 12(S)-hydroeicosatetraenoic acid, is found to activate Erkl/2 kinases in LNCaP cells and PKC in rat prostate AT2.1 tumor cells. Overexpression of 12-lipoxygenase and 15-lipoxygenase-l in prostate cancer cells stimulate prostate tumor angiogenesis and growth, suggesting a facilitative role for 12-lipoxygenase and 15-lipoxygenase-l in prostate tumor progression. The expression of 15-lipoxygenase-2 is found frequently to be lost during the initiation and progression of prostate tumors. 15(S)-hydroxyeicosatetraenoic acid, the product of 15-lipoxygenase-2, inhibits proliferation and causes apoptosis in human prostate cancer cells, suggesting an inhibitory role for 15-lipoxygenase-2 in prostate tumor progression. The regulation of prostate cancer progression by eicosanoids, in either positive or negative ways, provides an exciting possibility for management of this disease.