Levels of estrogen receptor B splice variant (ERBΔ5) mRNA correlates with progesterone receptor in breast carcinomas

It is well known that breast tumors which are estrogen positive ER(+) are more likely to respond to hormone therapy. However, a certain percentage of ER(+)/PR(+) tumors do not respond to this therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ERβ), as well as the existence of numerous isoforms/splice variants of both ERα and ERβ, suggests that a complex regulation of estrogen action exists. In this study, we analyzed the expression ratio of ERβ1 isoform and ERβΔ5 splice variant mRNAs, and its correlation with ER/PR status by quantitative RT-PCR and clinical and histopathological parameters. We found that the relative proportion of ERβΔ5 in the total ERβ1 transcript 'pool' inversely correlates with the PR level (p = -0,359, p< 0,003, Spearman). It may be that the ERβΔ5 variant modulates the ERα activity of downstream targets. In addition, we suggest that the determination of the expression profiles of ERα and ERβ isoforms and splice variants in the defined groups of patients are necessary for elucidating their involvement in endocrine resistance

The role of estrogen receptors isoforms in breast cancer

Background: Estrogen and progesterone receptor (ER/PR) status is an accepted predictive marker in breast cancer. It is well known that breast tumors, which are ER(+) are more likely to respond to endocrine therapy. However, certain percentage of ER(+)/PR(+) tumors do not respond to endocrine therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ERβ), as well as the existence of numerous isoforms/splice variants of both ERα and ERβ, suggests that complex regulation of estrogen action exists. In this study, we analyze does the expression of two ERβ isoforms correlates with ERα/PR status. Methods: Sixty samples of primary operable breast carcinomas were analyzed for ERα and PR protein levels and for mRNA expression of two ERβ isoforms (ERβ1 and ERβΔ5). ERα and PR proteins were measured by classical biochemical techniques, and ERβ mRNAs were measured by real-time RT-PCR. Results: Tumors are divided in three groups according to relative level of mRNA for ERβ1 and ERβΔ5. We found that there is no correlation of ERβ1 mRNA expression with ERα and PR protein levels. We confirmed the existence of inverse correlation of ERβΔ5 with PR and of ERβΔ5 with ERα in the group of postmenopausal patients. In the subsets of tumors defined by ERα/PR status, we found that percentage of tumors, which concomitantly expressed high levels of both transcripts, are parallel with those that do not response to tamoxifen treatment. Conclusion: Inverse correlation of ERα with ERβΔ5 and PR with ERβΔ5isoform suggests that ERβΔ5 may have inhibitory effect on ERα activity in postmenopausal patients. In addition, we point out that determination of expression profiles of ERα and ERβ isoforms in the defined groups of patient are necessary for elucidating its involvement in endocrine resistance.nul

Transcriptional ratio of estrogen receptor β mRNAs in carcinomas and in normal tissues

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The role of estrogen receptors isoforms in breast cancer

Background: Estrogen and progesterone receptor (ER/PR) status is an accepted predictive marker in breast cancer. It is well known that breast tumors, which are ER(+) are more likely to respond to endocrine therapy. However, certain percentage of ER(+)/PR(+) tumors do not respond to endocrine therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ERβ), as well as the existence of numerous isoforms/splice variants of both ERα and ERβ, suggests that complex regulation of estrogen action exists. In this study, we analyze does the expression of two ERβ isoforms correlates with ERα/PR status. Methods: Sixty samples of primary operable breast carcinomas were analyzed for ERα and PR protein levels and for mRNA expression of two ERβ isoforms (ERβ1 and ERβΔ5). ERα and PR proteins were measured by classical biochemical techniques, and ERβ mRNAs were measured by real-time RT-PCR. Results: Tumors are divided in three groups according to relative level of mRNA for ERβ1 and ERβΔ5. We found that there is no correlation of ERβ1 mRNA expression with ERα and PR protein levels. We confirmed the existence of inverse correlation of ERβΔ5 with PR and of ERβΔ5 with ERα in the group of postmenopausal patients. In the subsets of tumors defined by ERα/PR status, we found that percentage of tumors, which concomitantly expressed high levels of both transcripts, are parallel with those that do not response to tamoxifen treatment. Conclusion: Inverse correlation of ERα with ERβΔ5 and PR with ERβΔ5isoform suggests that ERβΔ5 may have inhibitory effect on ERα activity in postmenopausal patients. In addition, we point out that determination of expression profiles of ERα and ERβ isoforms in the defined groups of patient are necessary for elucidating its involvement in endocrine resistance.nul

Angiogenesis: bFGF and VEGF in breast carcinoma

Angiogenesis, or neovascularization, is a complex process leading to formation of new blood vessels from the pre-existing vascular network of the tissue. Angiogenesis plays a central role in various physiological and pathological conditions, including embryonic development, reproduction, inflammation and wound healing, infertility, heart diseases, ulcers, rheumatoid arthritis, diabetic blindness and cancer. It is a multistep process involving EC activation, basement membrane and extracellular matrix (ECM) degradation, EC proliferation, migration and differentiation, synthesis of new basement membrane and maturation of new blood vessels. Tumor vasculature is considered to be of an "immature" nature with series of structural abnormalities. There are reciprocal paracrine interactions between ECs, tumor cells, stroma and ECM. Angiogenesis plays a key role in transformation of normal to malignant cell, tumor progression and metastasis. It is similar to the metastatic process in that it requires EC attachment, proteolysis, and locomotion to proceed. A close relationship exists between the tumor and ECs invasiveness of the tissue. The switch to the angiogenic phenotype involves a change in the local equilibrium between positive and negative regulators of the growth of microvessels. Basic fibroblast growth factor (bFGF) and vas­cular endothelial growth factor (VEGF) are positive regulators of angiogenesis. Intimate cross-talk exists among bFGF and the different members of the VEGF family during angiogenesis, lymphangiogenesis, and vasculogenesis. A substantial body of experimental evidence supports the hypothesis that angiogenesis and angiogenic factors may be strong prognostic and predictive factors in breast carcinoma. This article reviews the current knowledge on angiogenesis and its positive regulators: bFGF and VEGF.

The importance of simultaneous determination of breast cancer biomarkers

It is shown that steroid hormone receptors by themselves are not sufficiently strong prognostic factors in management of breast cancer. For that reason, simultaneous consideration of different biomarkers seems to be more appropriate for clinical use, i.e. selections of patients with high/inter-mediate/low risk of disease outcome. However, the amount of tumor material available from breast carcinoma can preclude determination of estrogen- regulated biomarkers together with estrogen receptor and progesterone receptor. The aim of this study was to assess the possibility of estrogen receptor and progesterone receptor determination by a single-point instead of five-point biochemical method. Our results demonstrated that the correlation between measurements of estrogen and progesterone receptor contents obtained by the five-point and single-point assay in the total population was very high. Consequently, we could use the single-point assay instead of five-point assay for estrogen receptor and progesterone receptor determination, thus making possible determination of other molecular biomarkers from the same breast carcinoma

Correlation between steroid receptors, angiogenic factors, and classical prognostic parameters in node-negative breast cancer patients

Breast cancer (BC) progression is an estrogen receptor (ER) signaling- and angiogenesis-dependent process. This study investigated relationships between classical prognostic factors and biomarkers ER, PR, VEGF, and bFGF in node-negative BC patients. Positive correlation between ER and both PR (p < 0.001) or FGF (p = 0.04) levels indicates ER-regulated expression of these factors and a potential synergistic effect of ER and bFGF in tumor progression. Aside from correlation of age with ER and bFGF levels (p = 0.003; p = 0.05; respectively), no correlation of biomarkers with classical prognostic parameters was found, indicating that those biomarkers could be independent prognostic factors