Development of a high sensitivity, nested Q-PCR assay for mouse and human aromatase

Biomolecular evaluation of cryopreserved amniotic membranes for ophthalmological use by ELISA and RT-PCR at one and eighteen months

PURPOSE

To study the presence of certain proteins - EGF (epidermal growth factor), KGF (keratinocyte growth factor), IL-10 (interleukin 10), HGF (hepatocyte growth factor), Alpha2-macroglobulin and IL-1RA (interleukin 1 receptor antagonist) in cryopreserved amniotic membranes at 1 and 18 months and, as a secondary objective, to detect mRNA corresponding to KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, TGF beta (transforming growth factor beta) and Lumican by RT-PCR in membranes preserved at 1 and 18 months.

MATERIAL AND METHODS

Four samples of amniotic membrane were divided into 2 groups: the first group (N=2) cryopreserved for 1 month and the second group (N=2) cryopreserved for 18 months, in order to be studied by RT-PCR and ELISA.

RESULTS

RT-PCR detected KGF, IL-1Ra, Alpha2-macroglobulin, Fas Ligand, and Lumican. Of these, FAS Ligand mRNA was found in samples preserved for 1and 18 months. KGF, Lumican, and alpha2-microglobulin mRNA were found only at 1 month, and IL-1Ra mRNA was absent in both sample groups. RT-PCR for TGF-beta was inconclusive. ELISA was performed for detection and quantification of 6 proteins (EGF, KGF, IL-10, HGF, Alpha2-macroglobulin and IL-1Ra) in both amniotic membrane groups. All 6 proteins were found in all samples, with a lower concentration at 18 months compared to 1 month of preservation.

CONCLUSION

This study shows that membranes cryopreserved in 50% glycerol for 18 months do retain the proteins necessary for regeneration of the corneal surface, giving these membranes their biochemical properties.

The Hypertension Related Gene G-Protein Coupled Receptor Kinase 4 Contributes to Breast Cancer Proliferation

PURPOSE

Clinical studies have shown that breast cancer risk is increased in hypertensive women. The underlying molecular mechanism remains undetermined. The current study tests our hypothesis that G protein coupled receptor kinase 4 (GRK4) is a molecule that links hypertension and breast cancer. GRK4 plays an important role in regulation of renal sodium excretion. Sustained activation of GRK4 as in the circumstances of single nucleotide polymorphism (SNPs) causes hypertension. Expression of GRK4 in the kidney is regulated by cMyc, an oncogene that is amplified in breast cancer.

METHODS

Western analysis was used to evaluate GRK4 protein expression in seven breast cancer cell lines. GRK4 gene single nucleotide polymorphism in breast cancer cell lines and in breast cancer cDNA arrays were determined using TaqMan Genotyping qPRC. The function of GRK4 was evaluated in MCF-7 cells with cMyc knock-down and GRK4 re-expression and in MDA-MB-468 cells expressing inducible GRK4 shRNA lentivirus constructs. Nuclei counting and 5-Bromo-2'-deoxy-uridine (BrdU) labeling were used to evaluate cell growth and proliferation.

RESULTS

Genotyping of GRK4 SNPs in breast cancer cDNA arrays (n = 94) revealed that the frequency of carrying two hypertension related SNPs A142 V or R65 L is threefold higher in breast cancer patients than in healthy people (P = 7.53E-11). GRK4 protein is expressed in seven breast cancer cell lines but not the benign mammary epithelial cell line, MCF-10A. Three hypertension related SNPs in the GRK4 gene were identified in the breast cancer cell lines. Except for BT20, all other breast cancer lines have 1-3 GRK4 SNPs of which A142 V occurs in all 6 lines. MDA-MB-468 cells contain homozygous A142 V and R65 L SNPs. Knocking down cMyc in MCF-7 cells significantly reduced the growth rate, which was rescued by re-expression of GRK4. We then generated three stable GRK4 knock-down MDA-MB-468 lines using inducible lentiviral shRNA vectors. Doxycycline (Dox) induced GRK4 silencing significantly reduced GRK4 mRNA and protein levels, growth rates, and proliferation. As a marker of cell proliferation, the percentage of BrdU-labeled cells decreased from 45 ± 3% in the cells without Dox to 32 ± 5% in the cells treated with 0.1 µg/mL Dox.

CONCLUSIONS

GRK4 acts as an independent proliferation promotor in breast cancer. Our results suggest that targeted inhibition of GRK4 could be a new therapy for both hypertension and breast cancer.

Pro-Apoptotic Effects of Estetrol on Long-Term Estrogen-Deprived Breast Cancer Cells and at Low Doses on Hormone-Sensitive Cells

Purpose:

Postmenopausal women with estrogen receptor-positive breast cancers often respond initially to tamoxifen or aromatase inhibitor therapy. Resistance to these treatments usually develops within 12 to 18 months. Clinical studies have demonstrated that high-dose estrogen can induce regression of these endocrine-resistant tumors. However, side-effects of high-dose estradiol (E₂) or diethylstilbestrol (DES) limit their usage. Estetrol (E₄) is the most abundant estrogen during pregnancy and has a long half-life and a low potential for side-effects. Estetrol might then provide benefits similar to DES on tumor regression but with lesser toxicity.

Methods:

In this study, we systematically evaluated the effects of E₄ on cell proliferation and apoptosis in wild-type MCF-7 and long-term estrogen-deprived (LTED) MCF-7 cells and compared its effects with E₂ and estriol (E₃).

Results:

Estetrol induced apoptosis in LTED cells but stimulated growth of MCF-7 cells at concentrations from 10⁻¹¹ to 10⁻⁸ M. These effects of E₄ are similar to those of E₂ but require much higher doses. Differing from E₂, E₄ at 10⁻¹² M induced apoptosis in MCF-7 cells and another pregnancy estrogen, E₃, acted similarly. No antagonistic effect of E₄ or E₃ against E₂ occurred when they were combined.

Conclusions:

The pro-apoptotic effects of E₄ and E₃ on LTED cells and at low doses on MCF-7 cells indicate that these steroids could be used as therapeutic agents for endocrine-resistant or sensitive breast cancer.

Estrogen receptor β promoter methylation: a potential indicator of malignant changes in breast cancer

INTRODUCTION

Estrogen receptor β (ERβ) always lacks expression in estrogen-dependent tumors, which may result from gene inactivation by methylation. In this study, we aimed to determine whether aberrant methylation of the ERβ promoter is associated with decreased ERβ gene expression in breast cancer.

MATERIAL AND METHODS

ERβ methylation status was determined for 132 pairs of breast cancer and adjacent normal tissues via the MethyLight method. Additionally, mRNA relative expression was quantified by real-time polymerase chain reaction (RT-PCR) to determine whether aberrant methylation had a negative correlation with expression. The correlation of ERβ promoter methylation and clinical parameters is also discussed.

RESULTS

Methylation was observed in 96 (72.7%) breast cancer samples, and the median percentage of fully methylated reference (PMR) among methylated tissues was 0.83. Meanwhile, 94 (71.2%) adjacent normal tissues were methylated and the median PMR was 0.48. Compared to adjacent normal tissues, the methylation level of breast cancer was significantly higher (p < 0.001) and mRNA expression was much lower (p < 0.001). There was a significant correlation between ERβ methylation and mRNA expression in adjacent normal breast tissues (p = 0.004). In addition, the methylation rate of cancer tissues whose maximum diameter < 3 cm was significantly higher than those > 3 cm (p = 0.025).

CONCLUSIONS

ERβ promoter methylation level varies between cancerous and adjacent normal breast tissues. There was significant downregulation of ERβ methylation expression in pre-cancerous stages of breast cancer. Therefore, demethylation drugs may offer a potential strategy for preventing the development of pre-cancerous cells.

Inhibitory effects of a bazedoxifene/conjugated equine estrogen combination on human breast cancer cells in vitro

Breast cancer incidence is increased in women receiving menopausal hormone therapy with estrogen plus progestin but not with estrogen alone. The use of a tissue-selective estrogen complex (TSEC) has been proposed as a novel menopausal hormone therapy strategy to eliminate the requirement for a progestogen. Combination of bazedoxifene (BZA) with conjugated estrogens (CEs), the first TSEC, has shown beneficial effects. Whether it would exert antiestrogenic effects on breast cancer is not clear. To address this issue, we compared estradiol (E(2)) and CE alone on proliferation and apoptosis in MCF-7 breast cancer cells. CE stimulated growth of MCF-7 cells at a peak concentration 10-fold higher than required for E(2). Both CE and E(2) alone increased DNA synthesis and reduced apoptosis with activation of MAPK, Akt, and p70S6K and up-regulation of antiapoptotic factors survivin, Bcl-2, and X-linked inhibitor of apoptosis protein, These effects could be completely blocked by BZA. Gene expression studies demonstrated that CE and E(2) were equally potent on expression of cMyc, pS2, and WNT1 inducible signaling pathway protein 2, whereas the stimulatory effects of CE on progesterone receptor and amphiregulin expression were weaker than E(2). BZA effectively blocked each of these effects and showed no estrogen agonistic effects when used alone. Our results indicate that the stimulatory effects of E(2) or CE on breast cancer cells could be completely abrogated by BZA. These studies imply that the CE/BZA, TSEC, exerts antiestrogenic effects on breast cancer cells and might block the growth of occult breast neoplasms in postmenopausal women, resulting in an overall reduction in tumor incidence.

Aromatase immunoreactivity is increased in mammographically dense regions of the breast

Mammographic breast density (MBD) is one of the strongest risk factors for breast cancer. Unfortunately, the biologic basis underlying this association is unknown. This study compared aromatase expression or immunoreactivity (IR) in core biopsies from mammographically dense versus non-dense regions of the breast to examine whether estrogen synthesis in the breast is associated with MBD and one possible mechanism through which MBD may influence breast cancer. Eligible participants were 40+ years, had a screening mammogram with visible MBD and no prior cancer or current endocrine therapy. Mammograms were used to identify dense and non-dense regions and ultrasound-guided core biopsies were performed to obtain tissue from these regions. Immunostaining for aromatase employed the streptavidin-biotin amplification method and #677 mouse monoclonal antibody. Aromatase IR was scored in terms of extent and intensity of staining for each cell type (stroma, epithelium, adipocytes) on histologic sections. A modified histological H-score provided quantitation of aromatase IR in each cell type and overall. Repeated measure analyses evaluated average differences (β(H)) in H-score in dense versus non-dense tissue within and across cell types. Forty-nine women with mean age 50 years (range: 40-82), participated. Aromatase IR was increased in dense (vs. non-dense) tissue in both the stroma (β(H) = 0.58) and epithelium (β(H) = 0.12) (P < 0.01). Adipocytes from non-dense tissue, however, had a greater IR compared to those from dense tissue (β(H) = -0.24, P < 0.01). An overall H-score which integrated results from all cell types demonstrated that aromatase IR was twice as great for dense (mean H-score = 0.90, SD = 0.53) versus non-dense (mean H-score = 0.45, SD = 0.39) breast tissue (β(H) = 0.45; P < 0.001). Overall, aromatase IR was greater for mammographically dense versus non-dense tissue and may partly explain how MBD influences breast cancer.