Expression of platelet-derived endothelial cell growth factor and its mRNA in uterine endometrium during the menstrual cycle

Solving the Puzzle: What Is the Role of Progestogens in Neovascularization?

Ovarian sex steroids can modulate new vessel formation and development, and the clarification of the underlying mechanism will provide insight into neovascularization-related physiological changes and pathological conditions. Unlike estrogen, which mainly promotes neovascularization through activating classic post-receptor signaling pathways, progesterone (P4) regulates a variety of downstream factors with angiogenic or antiangiogenic effects, exerting various influences on neovascularization. Furthermore, diverse progestins, the synthetic progesterone receptor (PR) agonists structurally related to P4, have been used in numerous studies, which could contribute to unequal actions. As a result, there have been many conflicting observations in the past, making it difficult for researchers to define the exact role of progestogens (PR agonists including naturally occurring P4 and synthetic progestins). This review summarizes available evidence for progestogen-mediated neovascularization under physiological and pathological circumstances, and attempts to elaborate their functional characteristics and regulatory patterns from a comprehensive perspective.

Thymidine phosphorylase: A potential new target for treating cardiovascular disease

We recently found that thymidine phosphorylase (TYMP), also known as platelet-derived endothelial cell growth factor, plays an important role in platelet activation in vitro and thrombosis in vivo by participating in multiple signaling pathways. Platelets are a major source of TYMP. Since platelet-mediated clot formation is a key event in several fatal diseases, such as myocardial infarction, stroke and pulmonary embolism, understanding TYMP in depth may lead to uncovering novel mechanisms in the development of cardiovascular diseases. Targeting TYMP may become a novel therapeutic for cardiovascular disorders. In this review article, we summarize the discovery of TYMP and the potential molecular mechanisms of TYMP involved in the development of various diseases, especially cardiovascular diseases. We also offer insights regarding future studies exploring the role of TYMP in the development of cardiovascular disease as well as in therapy.

Sex steroids in uterine endometrial cancers

Some uterine endometrial cancers conserve estrogen dependency in advancement. However, the concept of advancement in tumor is complicated, because it involves simple growth in primary tumor and secondary spreading. The expression manner of estrogen receptor alpha exon 5 splicing variant, ER beta, progesterone receptor-A (N-terminus deletion mutant) is associated with metastatic potential in uterine endometrial cancers. Increased estrogen-related receptor alpha expression is related to tumor advancement with the loss of estrogen dependency. Steroid receptor coactivator-3 contributes to tumor progression and can be used as a treatment target for advanced uterine endometrial cancers. Estrogen responsive oncogenes, c-jun and c-Ha-ras, are not modi-fied by progestin in uterine endometrial cancer cells and are considered to be an instinct phenotype as such cancers. By contrast, metastatic potential of estrogen-dependent uterine endometrial cancers can be partially controlled by progestin via metastasis-related genes, E-cadherin/catenins, plasminogen activator inhibitor-1, vascular endothelial growth factor. Thus, sex steroids related phenomena are impress-ive in the advancement of uterine endometrial cancers.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

Thymidine phosphorylase (TP), also known as "platelet-derived endothelial cell growth factor" (PD-ECGF), is an enzyme, which is upregulated in a wide variety of solid tumors including breast and colorectal cancers. TP promotes tumor growth and metastasis by preventing apoptosis and inducing angiogenesis. Elevated levels of TP are associated with tumor aggressiveness and poor prognosis. Therefore, TP inhibitors are synthesized in an attempt to prevent tumor angiogenesis and metastasis. TP is also indispensable for the activation of the extensively used 5-fluorouracil prodrug capecitabine, which is clinically used for the treatment of colon and breast cancer. Clinical trials that combine capecitabine with TP-inducing therapies (such as taxanes or radiotherapy) suggest that increasing TP expression is an adequate strategy to enhance the antitumoral efficacy of capecitabine. Thus, TP plays a dual role in cancer development and therapy: on the one hand, TP inhibitors can abrogate the tumorigenic and metastatic properties of TP; on the other, TP activity is necessary for the activation of several chemotherapeutic drugs. This duality illustrates the complexity of the role of TP in tumor progression and in the clinical response to fluoropyrimidine-based chemotherapy.

Progesterone receptor positive colorectal tumors have lower thymidine phosphorylase expression: an immunohistochemical study

Present study aimed to find the clinicopathological significance of PgR and its association with TP expression in colorectal cancer. Immunohistochemical studies were performed on 83 colorectal adenocarcinoma patients using corresponding monoclonal antibodies of PgR and TP and LSAB detection kit. Mucin producing cells showed PgR expression and its expression was detected in 15.6% of normal and 59% of malignant tissues. Significant association were observed between PgR negative expression in malignant tissues and larger tumor size (p = 0.006), higher incidence of secondary organ metastasis (p = 0.014) and tumor pathological stage (p = 0.041). A close association was observed between PgR and lack of TP expression in malignant tissues that means out of 49 PgR (+) tumors, 43 cases (86%) were TP negative (p = 0.046). It seems that tumors with better prognosis were more likely to express PgR in their malignant tissues, which affects the expression of TP as one of the major therapeutic targets in CRC. Present study suggests progesterone therapy as a possible effective strategy to suppress colorectal cancers and as a novel anti-angiogenic therapy for tumor dormancy which needs complimentary studies for confirmation.

Targeting platelet-derived endothelial cell growth factor/thymidine phosphorylase for cancer therapy

Thymidine phosphorylase (TP) is a key enzyme in the pyrimidine nucleoside salvage pathway, but it also recognizes and inactivates various anti-cancer chemotherapeutic agents. Moreover, TP is identical to platelet-derived endothelial cell growth factor (PD-ECGF), an angiogenic factor with anti-apoptotic properties. Increased expression of PD-ECGF/TP is found in many tumor and stromal cells, and elevated TP levels are associated with aggressive disease and/or poor prognosis. Thus, progression and metastasis of TP-expressing tumors might be abrogated by TP inhibitors that are used as single agents or in combination with (TP-sensitive) nucleoside analogues. On the other hand, increased TP activity in tumors may be exploited for the tumor-specific activation of fluoropyrimidine prodrugs, such as capecitabine. This review will focus on the different biological activities of PD-ECGF/TP and their implications for cancer progression and treatment.

Sex steroid-dependent angiogenesis in uterine endometrial cancers

In general, tumors induce angiogenic factors specific to them, which leads to angiogenesis with advancement. However, angiogenesis in uterine endometrial cancers is complicated because hormone dependency in growth also modifies the angiogenic potential. Therefore, anti-angiogenic therapy for tumor dormancy in uterine endometrial cancers must be thoroughly considered. The upstream of vascular endothelial growth factor (VEGF) gene conserves estrogen-responsive elements. Progesterone primed with estrogen induces thymidine phosphorylase (TP) in uterine endometrium. Sex steroid-dependent VEGF and TP are highly expressed in cases of early stage and well-differentiated uterine endometrial cancers, and basic fibroblast growth factor (bFGF) in cases of advanced and poorly differentiated uterine endometrial cancers. A transcriptional factor for angiogenesis, ETS-1, is linked to VEGF in well-differentiated uterine endometrial cancers, and to bFGF in poorly differentiated uterine endometrial cancers. Therefore, even if dedifferentiation and angiogenic switching occur due to advancement and long-term hormone therapy, the inhibition of ETS-1 along with main angiogenic factors might be an effective strategy to suppress uterine endometrial cancers as a novel anti-angiogenic therapy.

Clinical implications of expression of cyclooxygenase-2 related to angiogenesis in uterine endometrial cancers

BACKGROUND

Angiogenesis is essential for development, growth and advancement of solid tumors. Cyclooxygenase (cox)-2 is recognized as an angiogenic factor in various tumors. This prompted us to study the clinical implications of cox-2 expression and angiogenesis in uterine endometrial cancers.

PATIENTS AND METHODS

Fifty patients underwent curative resection for uterine endometrial cancers. In uterine endometrial cancers, cox-2 levels were determined by enzyme immunoassay, and the localization and counts of microvessels were determined by immunohistochemistry.

RESULTS

There was a significant correlation between microvessel counts and cox-2 levels in uterine endometrial cancers. Cox-2 localized in the cancer cells, but not in the stromal cells of uterine endometrial cancer tissues. Cox-2 levels decreased with the advancement. Furthermore, cox-2 levels significantly correlated with VEGF levels in uterine endometrial cancers.

CONCLUSIONS

VEGF associated with cox-2 might work on angiogenesis at an early status in growth. Therefore, long-term administration of cox-2 inhibitors might be effective in the suppression of recurrent initiation of uterine endometrial cancers after curative resection.

Modulation of vascular endothelial growth factor and thymidine phosphorylase in normal human endometrial stromal cells

OBJECTIVE

To study the regulation of vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP), two angiogenic factors, in cultured endometrial stromal cells. The effects of steroids, E2, and P, the gonadotropin, hCG, and hypoxia were investigated.

DESIGN

Quantitative experimental study.

SETTING

Academic medical department.

PATIENT(S)

Women undergoing hysterectomy for benign causes.

INTERVENTION(S)

Endometrial cells were collected from subjects and cultured.

MAIN OUTCOME MEASURE(S)

The secretion of VEGF in supernatant media and the numbers of cells expressing VEGF or TP.

RESULT(S)

Estradiol increased VEGF secretion and the number of cells that contained VEGF and TP, and those effects were inhibited by hCG. Human chorionic gonadotropin alone could increase number of cells that expressed VEGF and TP. Hypoxia increased both VEGF secretion and number of cells containing VEGF and TP. Progesterone had no observed effect on VEGF secretion or number of VEGF- or TP-containing cells.

CONCLUSION(S)

Vascular endothelial growth factor and TP are present in stromal cells of normal endometrium, and E2 may interact with gonadotropins to regulate angiogenic compounds to modulate stromal functioning.

Dihydropyrimidine dehydrogenase in normal and malignant endometrium: relationship with cell proliferation and thymidine phosphorylase

Dihydropyrimidine dehydrogenase (DPD) is a pyrimidine salvage enzyme responsible for degradation of thymine, which is produced from thymidine by thymidine phosphorylase (TP). Our purpose was to determine the relationship between DPD, cell proliferation and TP expression in human endometrium. We examined DPD gene expression using reverse transcription-polymerase chain reaction, DPD protein levels using enzyme-linked immunosorbent assay, and DPD protein localization using immunohistochemistry in 58 normal endometria and 28 endometrial cancers. DPD gene expression was then related to the proliferating cell nuclear antigen index and to TP gene expression. DPD gene expression, which was correlated with DPD protein level, was relatively stable throughout various menstrual phases but was significantly elevated in postmenopausal status. It was significantly lower in endometrial cancer than in normal endometrium. Localization analysis revealed that DPD protein was located primarily in epithelial cells, but was also present in stromal cells. DPD gene expression correlated inversely with the PCNA index. TP gene expression pattern contrasted with that of DPD in postmenopausal and malignant endometrium. A high ratio of TP to DPD gene expression was significantly more frequent in endometrial cancer than in normal endometrium in any menstrual phase. DPD may act cooperatively with TP to affect cell function by maintaining the pyrimidine nucleotide pool balance in normal and malignant endometrium.

Expression of ETS-1 related to angiogenesis in uterine endometrium during the menstrual cycle

ETS-1 has been identified as a transcription factor for angiogenesis, which is essential for the development and growth of the uterine endometrium. This characteristic prompted us to study whether ETS-1 functions as an angiogenic mediator in uterine endometrium. Immunohistochemical staining revealed that the localization of ETS-1 was similar to that of vascular endothelial cells. There was a significant correlation between microvessel counts and both ETS-1 histoscores and ets-1 mRNA levels in uterine endometrium. The ETS-1 histoscores and ets-1 mRNA levels increased in the proliferative phase, reached a peak during peri-ovulation and decreased in the secretory phase. Furthermore, the ETS-1 histoscores and ets-1 mRNA levels correlated with vascular endothelial growth factor (VEGF) levels in the proliferative phase. This indicates that ETS-1 might be an angiogenic mediator in uterine endometrium linked to VEGF in the proliferative phase.

Effects of various steroids on platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA expression in uterine endometrial cancer cells

Progestins diminish the estrogen-induced angiogenic potential related to basic fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) in uterine endometrial cancer cells. This led us to study the effect of various steroids on the expression of platelet-derived endothelial cell growth factor (PD-ECGF) as the other pertinent angiogenic factor in well-differentiated uterine endometrial cancer cell line Ishikawa. In Ishikawa cells, estradiol induced the expression of PD-ECGF and its mRNA. The estrogen-induced expression was increased approximately two-fold by progesterone and by its metabolite, 17alpha-hydroxyprogesterone, but not by medroxyprogesterone acetate (MPA). Therefore, progesterone and 17alpha-hydroxyprogesterone as endogenous steroids might induce PD-ECGF-related angiogenic potential in uterine endometrial cancer cells, but not MPA as a synthetic steroid. In conclusion, the failure of PD-ECGF induction by MPA might be the great merit of anti-angiogenic treatment with MPA for uterine endometrial cancers.

Clinical implications of expression of ETS-1 related to angiogenesis in uterine endometrial cancers

BACKGROUND

Angiogenesis is essential for development, growth and advancement of solid tumors. During angiogenesis, ETS-1 is strongly expressed in vascular endothelial cells and the adjacent interstitial cells, while the inhibition of ETS-1 expression leads to suppression of angiogenesis. This prompted us to study the clinical implications of ETS-1 in relation to angiogenesis in uterine endometrial cancers.

PATIENTS AND METHODS

Sixty patients underwent resection for uterine endometrial cancers. From the tissues of 60 uterine endometrial cancers, the levels of ets-1 mRNA, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived endothelial cell growth factor (PD-ECGF) and interleukin (IL)-8 were determined by competitive RT-PCR using recombinant RNA and enzyme immunoassay, and the localization and counts of microvessel were determined by immunohistochemistry.

RESULTS

There was a significant correlation between microvessel count and ets-1 gene expression levels in uterine endometrial cancers. Immunohistochemical staining revealed that the localization of ETS-1 was similar to that of vascular endothelial cells. The level of ets-1 mRNA tended to increase with increasing disease stage. Furthermore, the level of ets-1 mRNA correlated with levels of VEGF in well-differentiated adenocarcinomas (G1) and of bFGF in moderately differentiated adenocarcinomas (G2) and poorly differentiated adenocarcinomas (G3).

CONCLUSIONS

ETS-1 is a possible angiogenic mediator in uterine endometrial cancers.

Angiogenesis extent and expression of matrix metalloproteinase-2 and -9 agree with progression of ovarian endometriomas

BACKGROUND

Changes in angiogenesis and expression of extracellular matrix-degrading enzymes have been substantiated in tumour changeover and progression.

METHODS

Tissues from 44 biopsies of stage III and IV ovarian endometriomas, and 10 biopsies of normal (control) endometrium were investigated immunohistochemically to count microvessels, and by in situ hybridization to assess the expression of mRNA of matrix metalloproteinase-2 (MMP-2) and MMP-9. Implants of the tissues were investigated in the chick embryo chorioallantoic membrane (CAM) assay to determine their angiogenic capacity.

RESULTS

The endometriomas displayed significantly higher counts than normal endometria and the highest values were associated with the deepest invasion level (stage IV). Microvessels localized in close association with ectopic endometrial cells in the form of winding and arborized tubes, often dilated in microaneurysmatic segments. These were absent in normal endometrium. Expression of MMP-2 and MMP-9 mRNA, evaluated as percentages of positive biopsies and intensity of expression, was up-regulated in endometriomas and more pronounced in stage IV. MMP-2 and MMP-9 mRNA were also expressed by host stromal cells, including microvascular endothelial cells, fibroblasts and macrophages, whereas the control endometrium showed very little expression of MMP-2 mRNA in a few endothelial cells and no expression of MMP-9 mRNA. Implants from stage IV endometrioma induced a more intense vasoproliferative response than those from stage III, while no vasoproliferative response was induced by the normal endometrium.

CONCLUSION

These data suggest that angiogenesis and degradation of extracellular matrix occur together in endometriosis and are more pronounced in stage IV, and that endometriosis cells and some host stromal cell populations co-operate in disease progression.

Angiogenesis: regulators and clinical applications

Angiogenesis is a fundamental process in reproduction and wound healing. Under these conditions, neovascularization is tightly regulated. Unregulated angiogenesis may lead to several angiogenic diseases and is thought to be indispensable for solid tumor growth and metastasis. The construction of a vascular network requires different sequential steps including the release of proteases from "activated" endothelial cells with subsequent degradation of the basement membrane surrounding the existing vessel, migration of endothelial cells into the interstitial space, endothelial cell proliferation, and differentiation into mature blood vessels. These processes are mediated by a wide range of angiogenic inducers, including growth factors, chemokines, angiogenic enzymes, endothelial specific receptors, and adhesion molecules. Finally, when sufficient neovascularization has occurred, angiogenic factors are down-regulated or the local concentration of inhibitors increases. As a result, the endothelial cells become quiescent, and the vessels remain or regress if no longer needed. Thus, angiogenesis requires many interactions that must be tightly regulated in a spatial and temporal manner. Each of these processes presents possible targets for therapeutic intervention. Synthetic inhibitors of cell invasion (marimastat, Neovastat, AG-3340), adhesion (Vitaxin), or proliferation (TNP-470, thalidomide, Combretastatin A-4), or compounds that interfere with angiogenic growth factors (interferon-alpha, suramin, and analogues) or their receptors (SU6668, SU5416), as well as endogenous inhibitors of angiogenesis (endostatin, interleukin-12) are being evaluated in clinical trials against a variety of solid tumors. As basic knowledge about the control of angiogenesis and its role in tumor growth and metastasis increases, it may be possible in the future to develop specific anti-angiogenic agents that offer a potential therapy for cancer and angiogenic diseases.

Steroid receptors and metastatic potential in endometrial cancers

The relative overexpression of estrogen receptor (ER)-alpha exon 5 splicing variant, the disrupted synchronization of ER-beta and ER-alpha expressions, and the suppression of progesterone receptor (PR) form A expression as a transcriptional repressor might be related to metastatic potential of uterine endometrial cancers, leading to poor patient prognosis related to estrogen refractoriness.

Vascular endothelial growth factor and platelet-derived endothelial cell growth factor expression are implicated in the angiogenesis of endometrial cancer

Although many angiogenic factors have been described, it is not well defined which factors are expressed in endometrial cancer. The object of this study was to examine mRNA levels of the two angiogenic factors, vascular endothelial growth factor (VEGF) and platelet-derived endothelial cell growth factor (PD-ECGF) in endometrial cancer tissues and their association with clinicopathological features including microvessel density. The level of VEGF and PD-ECGF mRNAs was assessed by semi-quantitative reverse transcription-polymerase chain reaction using beta-actin as an internal standard in 38 patients with endometrial cancer. Microvessel counts were also assessed by immunostaining for factor VIII-related antigen in the most vascularised area of the specimen. VEGF/beta-actin ratios of non-endometrioid tumours were significantly higher than those of endometrioid tumours (P = 0.013). VEGF/beta-actin ratios of cases with lymph-vascular space involvement were significantly higher than those of cases without lymph-vascular space involvement (P = 0.021). Although it was not statistically significant, PD-ECGF/beta-actin ratios in grade 3 tumours were higher than those in grade 1 and 2 tumours (P = 0.066). The microvessel density was significantly correlated with the level of VEGF and PD-ECGF mRNA expression (P = 0.041 and P < 0.0001, respectively). Our findings provide evidence that the expression of both VEGF and PD-ECGF is involved in the promotion of angiogenesis in endometrial cancer. In addition, VEGF and PD-ECGF might contribute to the aggressive potential of high grade tumours or certain histological subtypes with unfavourable prognosis through the induction of angiogenesis.

Progestins suppress estrogen-induced expression of vascular endothelial growth factor (VEGF) subtypes in uterine endometrial cancer cells

Vascular endothelial growth factor (VEGF) contributes to the early advancement of uterine endometrial cancers that conserve hormone dependency via angiogenic activity. This process prompted us to study sex steroidal suppression of VEGF expression in Ishikawa cells (a line of well-differentiated uterine endometrial cancer cells). Estrogen transiently induced VEGF subtype (VEGF165 and VEGF121) secretion from Ishikawa cells. Progestins (progesterone, medroxyprogesterone acetate (MPA) and 17 alpha-hydroxyprogesterone) suppressed the estrogen-induced events. In conclusion, progestins could suppress VEGF-related angiogenic potential, which contributes to tumor growth in the early stage of uterine endometrial cancers that conserve estrogen dependency.

Expression of platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA in uterine cervical cancers

Angiogenesis contributes to the growth and secondary spreading of solid tumours. Platelet-derived endothelial cell growth factor (PD-ECGF) is identified as such an angiogenic factor. In the present study, the prognosis of the patients with high PD-ECGF uterine cervical cancers was worse than those with low PD-ECGF cancers, and PD-ECGF expression correlated with cellular proliferation and with vascular density and venous invasion in uterine cervical cancers. Therefore, PD-ECGF might contribute to the growth of uterine cervical cancers via angiogenesis related to vascular spreading. Furthermore, PD-ECGF and its mRNA had a wide range and were highly expressed in uterine cervical cancers, especially squamous cell carcinoma, regardless of clinical stage. Therefore, PD-ECGF in uterine cervical cancers might play a role of basic angiogenesis in all processes of advancing of uterine cervical cancers. This indicates that 5'-deoxy-5-fluorouridine might be highly effective in squamous cell carcinoma of the cervix, which possesses a high activity of thymidine phosphorylase to convert 5'-deoxy-5-fluorouridine to 5-fluorouracil, and that some angiogenic inhibitors of new capillary formation might be effective in the inhibition of tumour growth and spreading associated with angiogenesis.

Expression of platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA in uterine endometrial cancers

To determine the potential of growth, invasion and metastasis of uterine endometrial cancer cells associated with neovascularization, the expressions of platelet-derived endothelial cell growth factor (PD-ECGF) and its mRNA in uterine endometrial cancers and in normal uterine endometria as controls were determined and the relationship between their expressions and histological grades, grades of myometrial invasion and clinical stages of uterine endometrial cancers was analyzed. The levels of PD-ECGF were significantly higher in uterine endometrial cancers of well-differentiated grade (G1) with invasion to < or =1/2 myometrium (B) and of stage 1 than in those of moderately and poorly differentiated grades (G2 and G3, respectively) limited to endometrium (A) and with invasion to >1/2 myometrium (C) and of stages II and III/IV and in normal uterine endometria. There was no significant difference in the levels between uterine endometrial cancers of G2 and G3, A and C, or stages II and III/IV and normal uterine endometria. Therefore, the active availability of PD-ECGF might contribute to the acceleration of angiogenic activity in the early process of invasion of well-differentiated uterine endometrial cancers.