Estrogen induces apoptosis in a rat prostatic adenocarcinoma: association with an increased expression of TGF-beta 1 and its type-I and type-II receptors

The Pros and Cons of Estrogens in Prostate Cancer: An Update with a Focus on Phytoestrogens

The role of estrogens in prostate cancer (PCa) is shrouded in mystery, with its actions going from angelic to devilish. The findings by Huggins and Hodges establishing PCa as a hormone-sensitive cancer have provided the basis for using estrogens in therapy. However, despite the clinical efficacy in suppressing tumor growth and the panoply of experimental evidence describing its anticarcinogenic effects, estrogens were abolished from PCa treatment because of the adverse secondary effects. Notwithstanding, research work over the years has continued investigating the effects of estrogens, reporting their pros and cons in prostate carcinogenesis. In contrast with the beneficial therapeutic effects, many reports have implicated estrogens in the disruption of prostate cell fate and tissue homeostasis. On the other hand, epidemiological data demonstrating the lower incidence of PCa in Eastern countries associated with a higher consumption of phytoestrogens support the beneficial role of estrogens in counteracting cancer development. Many studies have investigated the effects of phytoestrogens and the underlying mechanisms of action, which may contribute to developing safe estrogen-based anti-PCa therapies. This review compiles the existing data on the anti- and protumorigenic actions of estrogens and summarizes the anticancer effects of several phytoestrogens, highlighting their promising features in PCa treatment.

Lipid Peroxidation and Transforming Growth Factor-β1 Levels in Gastric Cancer at Pathologic Stages

OBJECTIVE

High levels of TGF-β1 and enhanced TGF-β1 receptor signaling are related to the pathology of gastric cancer. This effect is caused by oxidative stress and lipid peroxidation products. The aim of this study was to investigate the levels of TGF-β1 and lipid peroxidation products in gastric cancer patients and their correlation with pathologic stage.

MATERIAL AND METHODS

Lipid peroxidation products and TGF-β1 levels were studied in the serum samples of 50 gastric cancer patients and 18 control subjects.

RESULTS

HNE-protein adducts and TGF-β1 levels were significantly higher in T2, T3 and T4 gastric cancers than in either the T1 stage or controls (p<0.001). Pathologic stage was correlated with TGF-β1 levels (r=0.702, p<0.05).

CONCLUSION

These markers production may contribute to tumor angiogenesis and aid in the prognosis of the gastric cancer.

Mechanisms of prostate atrophy after LHRH antagonist cetrorelix injection: an experimental study in a rat model of benign prostatic hyperplasia

In the present study, we investigated the roles of TGF-β signaling pathway in a rat benign prostatic hyperplasia (BPH) model treated with cetrorelix. TGF-β1 and c-Myc expression were measured by qRT-PCR and Western blotting in the proximal and distal region of ventral prostatic lobes, respectively. We observed that treatment with cetrorelix led to a significant reduction of ventral prostate weight in a dose-dependent manner. In the proximal region, after cetrorelix treatment, the expression of TGF-β1 was dramatically increased (P<0.05), while the expression of c-Myc was significantly decreased (P<0.05). In comparison with the control group, the cetrorelix groups had more TUNEL-positive cells. Our findings strongly suggest that the TGF-β signaling pathway may be one of the major causes responsible for prostate volume reduction in BPH rats after cetrorelix treatment.

Mechanisms of oxysterol-induced carcinogenesis

Oxysterols are oxidation products of cholesterol that are generated by enzymatic reactions mediated by cytochrome P450 family enzymes or by non-enzymatic reactions involving reactive oxygen and nitrogen species. Oxysterols play various regulatory roles in normal cellular processes such as cholesterol homeostasis by acting as intermediates in cholesterol catabolism. Pathological effects of oxysterols have also been described, and various reports have implicated oxysterols in several disease states, including atherosclerosis, neurological disease, and cancer. Numerous studies show that oxysterols are associated with various types of cancer, including cancers of the colon, lung, skin, breast and bile ducts. The molecular mechanisms whereby oxysterols contribute to the initiation and progression of cancer are an area of active investigation. This review focuses on the current state of knowledge regarding the role of oxysterols in carcinogenesis. Mutagenicity of oxysterols has been described in both nuclear and mitochondrial DNA. Certain oxysterols such as cholesterol-epoxide and cholestanetriol have been shown to be mutagenic and genotoxic. Oxysterols possess pro-oxidative and pro-inflammatory properties that can contribute to carcinogenesis. Oxysterols can induce the production of inflammatory cytokines such as interleukin-8 and interleukin-1β. Certain oxysterols are also involved in the induction of cyclo-oxygenase-2 expression. Inflammatory effects can also be mediated through the activation of liver-X-receptor, a nuclear receptor for oxysterols. Thus, several distinct molecular mechanisms have been described showing that oxysterols contribute to the initiation and progression of cancers arising in various organ systems.

Treating prostate cancer: a rationale for targeting local oestrogens

Prostate cancer is the most commonly diagnosed cancer and the second most common cause of cancer-related death in men, and benign prostatic hyperplasia is the most common benign condition known to occur in ageing men. Oestrogen has been implicated in the development of prostate cancer, and offers a promising new avenue for treatment. Despite this, the role of oestrogens in the prostate is complex. This Perspective presents a rationale for a targeted approach for the treatment of prostate disease through the use of selective oestrogen-receptor modulators in conjunction with contemporary androgen-ablation therapy.

Sex steroid hormone receptors in human thymoma

In this study we examined the immunohistochemical localization of sex steroid receptors for estrogen alpha (ER alpha) and ER beta, progesterone-A (PR-A) and PR-B, and androgen (AR) in human thymoma (n = 132) and correlated these findings with various clinicopathological parameters. We used RT-PCR and real-time PCR to further study the expression of these receptors in 20 thymoma cases. Immunoreactivity for all sex steroid receptors was detected in the nuclei of thymoma epithelial cells. The percentage of immunopositive cases and the H-score values for each receptor (mean +/- SD) were: ER alpha, 66% and 85.8 +/- 80.2; ER beta, 7% and 7.2 +/- 8.7; PR-A, 4% and 2.7 +/- 4.9; PR-B, 49% and 55.8 +/- 68.3; and AR, 15% and 14.1 +/- 11.7, respectively. The results of real-time PCR were consistent with those of immunohistochemistry, especially results for ER alpha, PR-B, and AR. A significant positive correlation was detected between immunoreactivity for ER alpha and PR-B. ER alpha immunoreactivity was inversely correlated with tumor size, clinical stage, WHO classification, and Ki-67 labeling index. In addition, the status of ER alpha immunoreactivity was significantly associated with a better clinical outcome in thymoma patients. Results from our study suggest that estrogens may inhibit thymoma growth via ER alpha, and that ER alpha immunoreactivity may act as a prognostic factor in human thymoma.

Mechanisms for 2-methoxyestradiol-induced apoptosis of prostate cancer cells

Prostate and breast carcinomas are sex hormone-related carcinomas, which are known to be associated with an over-expression of the proto-oncogene Bcl-2. Here, we report that 2-methoxyestradiol (2-ME), an endogenous metabolite of estrogen that does not bind to nuclear estrogen receptors, effectively induces apoptosis in Bcl-2-expressing human prostate and breast carcinoma cells in vitro and in a rat prostate tumor model in vivo. In several cell lines derived from prostate, breast, liver and colorectal carcinomas, 2-ME treatment led to an activation of c-Jun N-terminal kinase (JNK) and phosphorylation of Bcl-2, which preceded the induction of apoptosis. In summary, our data suggest that 2-ME induces apoptosis in epithelial carcinomas by causing phosphorylation of JNK, which appears to be correlated with phosphorylation of Bcl-2.

Growth factors: roles in andrology

Mesenchymal-epithelial interactions are extremely important during growth and development and in the functional cytodifferentiation of male sex accessory organs. Interactions between mesenchyme and epithelium occur mainly through a paracrine action that is mediated by various growth factors. The role of androgens is very important for these organs and the androgenic effect is mediated by paracrine interactions. A number of growth factors have been studied in prostate and seminal vesicles from mice, rats, and humans because they are potent mediators of cellular proliferation, differentiation, and death. This review provides an overview of current knowledge about growth factors involved in the development of male sex accessory organs, with particular emphasis on the prostate.

Role of transforming growth factor-beta1 in prostate cancer

TGF-beta1 is an important regulator of the normal and malignant prostate. In the non-malignant prostate, TGF-beta1 stimulates cell differentiation, inhibits epithelial cell proliferation, and induces epithelial cell death. TGF-beta1 is secreted into semen where it is an important immunosuppressive factor. Prostate cancer cells express high levels of TGF-beta1, which seems to enhance prostate cancer growth and metastasis by stimulating angiogenesis and by inhibiting immune responses directed against tumour cells. Prostate cancer cells frequently lose their TGF-beta receptors and acquire resistance to the anti-proliferative and pro-apoptotic effects of TGF-beta1. Accordingly, high expression of TGF-beta1 and loss of TGF-beta receptor expression have been associated with a particularly bad prognosis in human prostate cancer patients. TGF-beta1 also seems to be a mediator of castration-induced apoptosis in androgen dependent normal and malignant prostate epithelial cells. The ability of some prostate tumours to avoid castration-induced apoptosis may not, however, be simply due to loss of TGF-beta receptor type I or type II expression in the tumour cells. It may also be related to an inability of these cells to up-regulate TGF-beta receptor levels in response to castration or possibly due to defects downstream of the receptors. Short-term therapy-induced changes in the TGF-beta system in prostate tumours can probably be used to predict the long-term response to androgen ablation treatment. Further investigations into the TGF-beta system in the prostate are needed, however, to elucidate how alterations in this system affect the behaviour of prostate tumours, and whether this system can be manipulated for therapeutical purposes.

A novel gene overexpressed in the prostate of castrated rats: hormonal regulation, relationship to apoptosis and to acquired prostatic cell androgen independence

We have identified a novel complementary DNA (cDNA) corresponding to a gene overexpressed in the rat ventral prostate after castration. This cDNA displays 89.4% identity with 453 bp of a mouse EST and 81.5% identity with 157 bp of a human EST and was named PARM-1 for prostatic androgen-repressed message-1. The complete cDNA is 1187 bp long and codes for a protein of 298 amino acids that contains four potential glycosylation sites and three half cystinyl residues. The PARM-1 gene was found to be expressed at quite low levels in most rat tissues including those of the urogenital tract. The kinetic of induction of PARM-1 gene in the prostate was highly correlated to the development of apoptosis in the whole organ. Supplementation of castrated animals with androgens reversed both the process of apoptosis and the overexpression of PARM-1 gene. Supplementation with estrogens did not result in an increase in the PARM-1 messenger RNA levels when compared with the castration alone. However, the treatment resulted in a more rapid return to intact levels in the castrated plus estrogen group. When apoptosis of testis and prostate was induced in vivo by hypophysectomy, it was found that PARM-1 was only overexpressed in the prostate. Therefore, PARM-1 seems to be regulated by androgens only in the prostate. Using in situ hybridization and immunohistological techniques, we have shown that PARM-1 gene product is found exclusively in the epithelial cells of involuting prostate. Analysis by flow cytometry of MAT LyLu epithelial cells transiently expressing PARM-1 protein did not allow us to demonstrate a direct effect of PARM-1 gene overexpression on the programmed death of the transfected cells. Treatment of MAT LyLu cells by transforming growth factor-beta induced apoptosis but had no effect on PARM-1 production. However PARM-1 protein has been detected by Western blotting in various cell lines such as MAT LyLu, MAT Lu, and PIF, which are androgen independent. This would suggest that PARM-1 gene product would be a marker for acquired androgen-independence of these tumor cells.

Overlapping and divergent actions of estrogen and the neurotrophins on cell fate and p53-dependent signal transduction in conditionally immortalized cerebral cortical neuroblasts

The developing cerebral cortex undergoes overlapping periods of neurogenesis, suicide, and differentiation to generate the mature cortical plate. The following experiments examined the role of the gonadal hormone estrogen in comparison to the neurotrophins, in the regulation of p53-dependent cortical cell fate. To synchronize choices between neurogenesis, apoptosis, and neural differentiation, embryonic rat cerebral cortical neuroblasts were conditionally immortalized with the SV40 large T antigen containing the tsA58/U19 temperature-sensitive mutations. At the nonpermissive temperature, cessation of large T antigen expression was accompanied by induction of p53, as well as the p53-dependent proteins, wild-type p53-activated fragment-1/Cdk (cyclin-dependent kinase)-interacting protein-1 (p21/Waf1), Bcl (B-cell lymphoma)-associated protein (Bax), and murine double minute 2 (MDM2), that lead to cell cycle-arrest, suicide, and p53 inhibition, respectively. Simultaneously, neuroblasts exit cell cycle and die apoptotically or differentiate primarily into astrocytes and immature postmitotic neuroblasts. At the nonpermissive temperature, estrogen specifically induced an antagonist-independent increase in phosphorylated p53 expression, while increasing p21/Waf1 and decreasing Bax. Coincidentally, estrogen rapidly increased and then decreased MDM2 relative to controls, suggesting temporal modulation of p53 function. Both estrogen and neurotrophins prevented DNA fragmentation, a marker for apoptosis. However, estrogen also induced a transient increase in released lactate dehydrogenase, suggesting that estrogen simultaneously induced rapid cell death in a subpopulation of cells. In contrast to the neurotrophins, estrogen also increased cell proliferation. Both estrogen and the neurotrophins supported neuronal differentiation. However, in contrast to the neurotrophins, estrogen only supported the expression of a subset of oligodendrocytic markers. These results suggest that estrogen and the neurotrophins support overlapping and distinct aspects of differentiation in the developing cerebral cortex.

Identification of the genes responsive to etoposide-induced apoptosis: application of DNA chip technology

DNA chip technology was used in an attempt to identify target genes responsible for apoptosis induced by etoposide, a p53 activating topoisomerase II inhibitor used clinically as an antitumor agent. 62 Individual mRNAs whose mass changed significantly were identified after screening oligonucleotide arrays capable of detecting 6591 unique human mRNA species. 12 (Nine induced and three repressed) of the etoposide-responsive genes were further studied by Northern analysis and an agreement rate of 92%, was reached. Among the 12 genes studied, two (WAF1/p21 and PCNA) are known p53 regulatory genes, two (glutathione peroxidase and S100A2 calcium-binding protein) appear to be the novel p53 target genes and the others appear to be p53-independent. Based upon these findings, the signalling pathways that possibly mediate etoposide-induced apoptosis are proposed.

Female cats have lower rates of apoptosis in peripheral blood lymphocytes than male cats: correlation with estradiol-17beta, but not with progesterone blood levels

During earlier study, we quantified by flow cytometry the rate of apoptotic feline lymphocytes after overnight culture. We found evidence that the sex of the animals influences the rate of apoptosis, intact females showed lower rates of apoptosis in lymphocytes cultured overnight than castrated male cats. This observation was also confirmed for cats that were previously experimentally infected with the feline immunodeficiency virus (FIV). In an attempt to find an explanation for these sexually determined differences, plasma estradiol-17beta and progesterone levels were measured by radio-immuno assay in the blood of these cats. The hormone levels were analyzed with respect to the rate of lymphocyte apoptosis. As expected, castrated males had lower blood levels of estradiol and progesterone than females. However, no overall correlation was found between hormone blood levels and rate of apoptosis under non-stimulating conditions. Interestingly, the rate of apoptosis found in lymphocytes collected from females and stimulated overnight in phytohaemaglutinin-containing medium, showed a strong negative correlation with the estradiol levels in the blood of these cats. To our knowledge, this is the first confirmation that estradiol in physiological concentrations may protect peripheral lymphocytes from apoptosis after stimulation. No correlation was found in male cats. In conclusion, these observations broaden the list of sexually determined differences of the immune system, sex and sex hormones predispose males and females for certain immune responses and dysfunctions. The present observations have to be taken into account when designing or interpreting experiments on apoptosis and, for example, evaluating the influence of a preexisting FIV infection on the rate of apoptosis. It would be highly advisable to include only spayed cats in studies on the immune system so as to minimize the influence of sex hormones.

Inhibitory effects of soy and rye diets on the development of Dunning R3327 prostate adenocarcinoma in rats

METHODS

Dunning R3327 PAP prostate tumors were transplanted in 125 rats, the rats were divided into five groups, and tumor development was examined for 24 weeks during treatment with diets containing 33% of soy flour (SD), rye bran (RB), heat-treated rye bran (HRB), or rye endosperm (RE).

RESULTS

In the SD, RB, and HRB groups, significantly fewer palpable tumors and lower tumor volume were detected 14 and 16 weeks after transplantation when compared with the control, fiber-free dietary (FF) group. The body weight was lower 16 weeks after tumor transplantation in the RB and HRB groups when compared with the control group (P < 0.05). Rats in the RB and the HRB groups had a significant lower energy intake than the FF group during the first metabolic observation period, 3-6 weeks after tumor transplantation (P < 0.05), whereas the energy intake was the same in all groups during the second metabolic observation period, 13-16 weeks after tumor transplantation. However, when the tumor volume was adjusted for the body weight of the animals, there were still significant lower tumor volumes in the SD, RB, and HRB groups compared with the FF group (P < 0.05). A significant increase in daily urinary excretion of the isoflavonoids, daidzein, O-desmethylangolensin, equol, and Genistein, was observed in the rats fed SD, and of the ligands enterolactone and enterodiol in the rats fed RB and HRB during both metabolic periods. There were no differences in testosterone levels between the groups.

CONCLUSIONS

The present study shows that SD inhibits implanted prostate cancer growth. Although RB and HRB had a protective effect, further studies are needed to exclude the possibility that a low energy intake played a role in this respect. The results suggest that phytoestrogens (isoflavonoids and ligands), may be responsible for the delayed prostate tumor growth.

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor α, retinoic acid, vitamin D3, and the transforming growth factor β families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

Apoptosis in rat prostatic adenocarcinoma is associated with rapid infiltration of cytotoxic T-cells and activated macrophages

Rats transplanted with the androgen-sensitive, syngeneic Dunning R3327 PAP prostatic tumor were castrated and treated with estrogen or vehicle for 4, 12 and 24 hr and for 6 weeks. Tumor growth was retarded by castration and further inhibited by estrogen. Immediately after castration, an increased number of activated macrophages and T-cells were found in parallel with increasing apoptotic tumor cells. Administration of an immunosuppressive drug, FK 506, abolished the growth-inhibitory effects of castration and estrogen. The tumor growth rate correlated negatively with the number of R73- and OX8-positive T-cells and NK cells and with the percentage of ED3-positive macrophages. There was a positive correlation between the percentage of TdT-mediated-dUTP nick end labeling (TUNEL)-positive apoptotic cells and that of ED3-positive cells. Our results suggest that apoptosis of prostatic carcinoma cells induced by endocrine treatment in vivo is partly due to a rapid infiltration by immunocompetent cells.