Vascular endothelial growth factor-D over-expressing tumor cells induce differential effects on uterine vasculature in a mouse model of endometrial cancer

BACKGROUND

It has been hypothesised that increased VEGF-D expression may be an independent prognostic factor for endometrial cancer progression and lymph node metastasis; however, the mechanism by which VEGF-D may promote disease progression in women with endometrial cancer has not been investigated. Our aim was to describe the distribution of lymphatic vessels in mouse uterus and to examine the effect of VEGF-D over-expression on these vessels in a model of endometrial cancer. We hypothesised that VEGF-D over-expression would stimulate growth of new lymphatic vessels into the endometrium, thereby contributing to cancer progression.

METHODS

We initially described the distribution of lymphatic vessels (Lyve-1, podoplanin, VEGFR-3) and VEGF-D expression in the mouse uterus during the estrous cycle, early pregnancy and in response to estradiol-17beta and progesterone using immunohistochemistry. We also examined the effects of VEGF-D over-expression on uterine vasculature by inoculating uterine horns in NOD SCID mice with control or VEGF-D-expressing 293EBNA tumor cells.

RESULTS

Lymphatic vessels positive for the lymphatic endothelial cell markers Lyve-1, podoplanin and VEGFR-3 profiles were largely restricted to the connective tissue between the myometrial circular and longitudinal muscle layers; very few lymphatic vessel profiles were observed in the endometrium. VEGF-D immunostaining was present in all uterine compartments (epithelium, stroma, myometrium), although expression was generally low. VEGF-D immunoexpression was slightly but significantly higher in estrus relative to diestrus; and in estradiol-17beta treated mice relative to vehicle or progesterone treated mice. The presence of VEGF-D over-expressing tumor cells did not induce endometrial lymphangiogenesis, although changes were observed in existing vessel profiles. For myometrial lymphatic and endometrial blood vessels, the percentage of profiles containing proliferating endothelial cells, and the cross sectional area of vessel profiles were significantly increased in response to VEGF-D in comparison to control tumor cells. In contrast, no significant changes were noted in myometrial blood vessels. In addition, examples of invading cells or tumor emboli were observed in mice receiving VEGF-D expressing 293EBNA cells.

CONCLUSIONS

These results illustrate that VEGF-D over-expression has differential effects on the uterine vasculature. These effects may facilitate VEGF-D's ability to promote endometrial cancer metastasis and disease progression.

Progesterone, but not estrogen, stimulates vessel maturation in the mouse endometrium

The human endometrium undergoes regular periods of growth and regression, including concomitant changes in the vasculature, and is one of the few adult tissues where significant angiogenesis and vascular maturation occurs on a routine, physiological basis. The aim of this study was to investigate the effects of estrogen and progesterone on endometrial vascular maturation in mice. Endometrial tissues were collected from early pregnant mice (d 1-4) and ovariectomized mice given a single 17beta-estradiol (100 ng) injection 24 h before dissection (short-term estrogen regime) or three consecutive daily injections of progesterone (1 mg) with/without estrogen priming (progesterone regime). Experiments were then repeated with the inclusion of mice treated concurrently with progesterone and either RU486 or a vascular endothelial growth factor-A antiserum. Proliferating vascular mural cells (PVMC) were observed on d 3-4 of pregnancy, corresponding with an increase in circulating progesterone. A significant increase in PVMC and alpha-smooth muscle actin (labels mural cells) coverage of vessel profiles were observed in mice treated with progesterone in comparison to controls; no significant change was noted in mice treated with estrogen or with vascular endothelial growth factor antiserum. RU486 treatment did not inhibit the progesterone-induced increases in PVMC and mural cell coverage, although progesterone-induced changes in endothelial and epithelial cell proliferation were inhibited. These results show that progesterone, but not estrogen, stimulates vessel maturation in the mouse endometrium. The work illustrates the relevancy of the mouse model for understanding endometrial vascular remodeling during the menstrual cycle and in response to the clinically important progesterone receptor antagonist RU486.

Lymphangiogenesis of normal endometrium and endometrial adenocarcinoma

BACKGROUND

Information about lymphatics and lymphangiogenesis in the human endometrium is limited. We investigated the distribution of endometrial lymphatic vessels during the normal menstrual cycle and in association with endometrial adenocarcinoma and investigated the expression of lymphangiogenic growth factors, vascular endothelial growth factor (VEGF)-C, VEGF-D and VEGF receptor-3 (VEGF-R3).

METHODS AND RESULTS

Full thickness uterine samples (n = 23 proliferative; n = 23 secretory) and endometrial adenocarcinoma samples (n = 7 grade I; n = 10 grade III) were collected for the study and analysed by immunohistochemistry and western blotting. Lymphatic vessels of the functionalis were significantly reduced compared with basalis (P = 0.001) across the menstrual cycle with lymphatics of the basalis sometimes intimately associated with spiral arterioles. Lymphatic vessels of endometrial adenocarcinomas were located intra-tumoural and peri-tumoural with significant increases in the peri-tumoural lymphatic vessels compared with normal basalis (P = 0.02). Interestingly, high-grade adenocarcinoma vessels containing tumour emboli demonstrated a mixed blood/lymphatic endothelial cell phenotype. VEGF-C and VEGF-D were immunolocalized in glandular epithelium and some stromal cells with the staining intensity of this localization increasing in endometrial adenocarcinoma. Protein analysis identified VEGF-C (58, 41, 31 and 21 kD) and VEGF-D (56, 41, 31 and 21 kD) and VEGF-R3 (148 and 65 kD) peptides in normal endometrium, with significant increases in several of these peptides for VEGF-C and VEGF-D and no changes in protein expression for VEGF-R3 in endometrial adenocarcinoma.

CONCLUSION

Endometrial lymphatics are significantly reduced in the functionalis, and increases in endometrial adenocarcinoma peri-tumoural lymphatics are associated with increases in VEGF-C and VEGF-D peptides.

Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle

This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.

Increased expression of the relaxin receptor (LGR7) in human endometrium during the secretory phase of the menstrual cycle

Relaxin (RLX) is a structural homolog of insulin that is the ligand for the LGR7 receptor. Although the 6k peptide is produced by the ovaries to cause connective tissue remodeling of the rodent and pig reproductive tracts to facilitate parturition, in human reproduction, the role of RLX is less well understood. Binding of human gene 2 (H2) [(33)P]-RLX, expression of RLX peptides and the LGR7 receptor was examined in the human uterus at different stages of the menstrual cycle. A significant increase in RLX receptor binding in endometrium was identified by quantitative autoradiography in the secretory compared with the proliferative phase. H2RLX competed with [(33)P]-H2RLX binding with higher affinity than porcine RLX during both the proliferative and secretory phases. Increased LGR7 receptor gene expression during the secretory phase paralleled the changes in [(33)P]-H2RLX binding. Human gene 1 RLX transcripts were not detected in the uterus, and H2RLX gene expression was low and not influenced by the stage of the menstrual cycle. The studies show that binding to and gene expression of the LGR7 RLX receptor changes markedly with the phases of the menstrual cycle, suggesting a specific role for the hormone in the physiology of the human uterus.

Lack of correlation between vascular endothelial growth factor production and endothelial cell proliferation in the human endometrium

The role of vascular endothelial growth factor (VEGF) in endometrial angiogenesis was examined by measuring its production in human endometrial tissues from different stages of the menstrual cycle and relating these data to endothelial cell proliferation in the same tissues. Conditioned medium was collected from explant, and separated glandular epithelial and stromal cells cultured from 24 normal human endometrial biopsies and VEGF measured by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was also used to assess VEGF and the percentage of proliferating microvessels in the samples. Wide variation in results between individual endometrial samples at each stage of the menstrual cycle was observed for all parameters measured. There was no significant difference in VEGF secretion by explant, glandular epithelial or stromal cell cultures across the menstrual cycle, or in the percentage of proliferating vessels. VEGF immunostaining in the stroma was elevated during the early proliferative stage (P = 0.03). Epithelial cells secreted more VEGF than stromal cells (1.76 +/- 0.46 versus 0.46 +/- 0.06 ng per 10(5) cells; P = 0.002). There was no correlation between VEGF secreted by cultured explants, epithelial or stromal cells, VEGF immunostaining and the proportion of proliferating microvessels. These results show that the majority of endometrial VEGF is produced by glands, but neither total glandular nor stromal VEGF is correlated with endometrial endothelial cell proliferation. There is still no clear understanding on the regulation of human endometrial angiogenesis.

High predictive accuracy for detection of left main coronary artery disease by antilog signal processing of two-dimensional echocardiographic images

Two-dimensional echocardiography has been used to image the left main coronary artery. We have successfully imaged the left main coronary artery in 16 of 19 patients with left main coronary artery disease (LMCAD) and in 14 of 18 control patients using a dynamically focused 3-1/2 MHz experimental phased array sector scanner. Images were displayed with standard logarithmic compression grey scale allocation and with a modified antilog curve which enhances high intensity echoes. All of the 16 patients with LMCAD were identified from the antilog processed image. Only 1 of the 18 control patients had a false positive study. Modified antilog processed images provide high sensitivity (100%) and specificity (93%) for detecting LMCAD. This noninvasive technique could be used to screen patients for the presence or absence of LMCAD.