Estrogen markedly reduces circulating low-density neutrophils and enhances pro-tumoral gene expression in neutrophil of tumour-bearing mice

Background

Neutrophils are important for immune surveillance of tumour cells. Neutrophils may also be epigenetically programmed in the tumour microenvironment to promote tumour progression. In addition to the commonly known high-density neutrophils (HDN) based on their separation on density gradient, recent studies have reported the presence of high levels of low-density neutrophils (LDN) in tumour-bearing mice and cancer patients. We reported previously that estrogen promotes the growth of estrogen receptor α-negative mammary tumours in mice undergoing mammary involution through stimulating pro-tumoral activities of neutrophils in the mammary tissue.

Methods

Female BALB/cAnNTac mice at 7–8 weeks old were mated and bilateral ovariectomy was performed 2 days post-partum. At 24 h after forced-weaning of pups to induce mammary involution, post-partum female mice were injected with either E2V, or vehicle control on alternative days for 2-weeks. On 48 h post-weaning, treated female mice were inoculated subcutaneously with 4 T1-Luc2 cells into the 9th abdominal mammary gland. Age-matched nulliparous female was treated similarly. Animals were euthanized on day 14 post-tumour inoculation for analysis. To evaluate the short-term effect of estrogen, post-partum females were treated with only one dose of E2V on day 12 post-tumour inoculation.

Results

Estrogen treatment for 2-weeks reduces the number of blood LDN by more than 10-fold in tumour-bearing nulliparous and involuting mice, whilst it had no significant effect on blood HDN. The effect on tumour-bearing mice is associated with reduced number of mitotic neutrophils in the bone marrow and increased apoptosis in blood neutrophils. Since estrogen enhanced tumour growth in involuting mice, but not in nulliparous mice, we assessed the effect of estrogen on the gene expression associated with pro-tumoral activities of neutrophils. Whilst 48 h treatment with estrogen had no effect, 2-weeks treatment significantly increased the expression of Arg1, Il1b and Tgfb1 in both HDN and LDN of involuting mice. In contrast, estrogen increased the expression of Arg1 and Ccl5 in HDN and LDN of nulliparous mice.

Conclusions

Prolonged estrogenic stimulation in tumour-bearing mice markedly hampered tumour-associated increase of LDN plausibly by inhibiting their output from the bone marrow and by shortening their life span. Estrogen also alters the gene expression in neutrophils that is not seen in tumour-free mice. The results imply that estrogen may significantly influence the tumour-modulating activity of blood neutrophils.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08751-2.

Pomc Plays an Important Role in Sexual Size Dimorphism in Tilapia

Sexual dimorphism is common across the animal kingdom. Knowledge of the mechanisms of sexual size dimorphism is limited although it is important in biology and aquaculture. Tilapia is the common name for ~ 100 species of cichlid fish. Some are important aquaculture species and males outgrow females. To gain novel insights into the mechanisms underlying sexual size dimorphism, we analyzed the differences of brain transcriptomes between males and females in Mozambique tilapia and studied the function of the pro-opiomelanocortin (Pomc) gene in tilapia and zebrafish. The transcriptome analysis identified 123, 55, and 2706 sex-biased genes at 5, 30, and 90 dph (days post-hatch), respectively, indicating sexual dimorphism of gene expressions in the brain. The expression of Pomc in the tilapia brain was a female-biased at 30, 90, and 120 dph. An analysis of the DNA sequence located upstream of the tilapia Pomc transcriptional start site identified two estrogenic response elements. In vitro luciferase assay of the two elements revealed that β-estradiol significantly enhanced the expression of luciferase activity, suggesting that the expression of Pomc is mediated by estrogen. We knocked out Pomc in zebrafish using Crispr/Cas-9. The Pomc-knockout zebrafish showed faster growth and higher sensitivity to feeding as compared to the wild-type fish. Taken together, our results indicate that Pomc contributes to sexual size dimorphism and suggest that the high estrogen level in females promotes the expression of Pomc and suppresses feeding in female tilapias, which leads to the slower growth of female tilapias.

Protein arginine methyltransferase 6 enhances ligand-dependent and -independent activity of estrogen receptor α via distinct mechanisms

Recent studies reported that protein arginine methyltransferase 6 (PRMT6) enhances estrogen-induced activity of estrogen receptor α (ERα) and dysfunction of PRMT6 is associated with overall better survival for ERα-positive breast cancer patients. However, it is unclear how PRMT6 promotes ERα activity. Here we report that PRMT6 specifically interacts with ERα at its ligand-binding domain. PRMT6 also methylates ERα both in vitro and in vivo. In addition to enhancing estrogen-induced ERα activity, PRMT6 over-expression up-regulates estrogen-independent activity of ERα and PRMT6 gene silencing in MCF7 cells inhibits ligand-independent ERα activation. More interestingly, the effect of PRMT6 on the ligand-independent ERα activity does not require its methyltransferase activity. Instead, PRMT6 competes with Hsp90 for ERα binding: PRMT6 and Hsp90 bindings to ERα are mutually exclusive and PRMT6 over-expression reduces ERα interaction with Hsp90. In conclusion, PRMT6 requires its methyltransferase activity to enhance ERα's ligand-induced activity, but its effect on ligand-independent activity is likely mediated through competing with Hsp90 for binding to the C-terminal domain of ERα. PRMT6-ERα interaction would prevent ERα-Hsp90 association. Since Hsp90 and associated chaperones serve to maintain ERα conformation for ligand-binding yet functionally inactive, inhibition of ERα-Hsp90 interaction would relieve ERα from the constraint of chaperone complex.

Lysine methylation of progesterone receptor at activation function 1 regulates both ligand-independent activity and ligand sensitivity of the receptor

Progesterone receptor (PR) exists in two isoforms, PRA and PRB, and both contain activation functions AF-1 and AF-2. It is believed that AF-1 is primarily responsible for the ligand-independent activity, whereas AF-2 mediates ligand-dependent PR activation. Although more than a dozen post-translational modifications of PR have been reported, no post-translational modification on AF-1 or AF-2 has been reported. Using LC-MS/MS-based proteomic analysis, this study revealed AF-1 monomethylation at Lys-464. Mutational analysis revealed the remarkable importance of Lys-464 in regulating PR activity. Single point mutation K464Q or K464A led to ligand-independent PR gel upshift similar to the ligand-induced gel upshift. This upshift was associated with increases in both ligand-dependent and ligand-independent PR phosphorylation and PR activity due to the hyperactivation of AF-1. In contrast, mutation of Lys-464 to the bulkier phenylalanine to mimic the effect of methylation caused a drastic decrease in PR activity. Importantly, PR-K464Q also showed heightened ligand sensitivity, and this was associated with increases in its functional interaction with transcription co-regulators NCoR1 and SRC-1. These results suggest that monomethylation of PR at Lys-464 probably has a repressive effect on AF-1 activity and ligand sensitivity.

Acetylation at lysine 183 of progesterone receptor by p300 accelerates DNA binding kinetics and transactivation of direct target genes

The identification of lysine acetylation of steroid hormone receptors has previously been based on the presence of consensus motif (K/R)XKK. This study reports the discovery by mass spectrometry of a novel progesterone receptor acetylation site at Lys-183 that is not in the consensus motif. In vivo acetylation and mutagenesis experiments revealed that Lys-183 is a primary site of progesterone receptor (PR) acetylation. Lys-183 acetylation is enhanced by p300 overexpression and abrogated by p300 gene silencing, suggesting that p300 is the major acetyltransferase for Lys-183 acetylation. Furthermore, p300-mediated Lys-183 acetylation is associated with heightened PR activity. Accordingly, the acetylation-mimicking mutant PRB-K183Q exhibited accelerated DNA binding kinetics and greater activity compared with the wild-type PRB on genes containing progesterone response element. In contrast, Lys-183 acetylation had no influence on PR tethering effect on the nuclear factor κ-light chain enhancer of activated B cells (NFκB). Additionally, increases of Lys-183 acetylation by p300 overexpression or inhibition of deacetylation resulted in increases of Ser-294 phosphorylation levels. In conclusion, PR acetylation at Lys-183 by p300 potentiates PR activity through accelerated binding of its direct target genes without affecting PR tethering on other transcription factors. The effect may be mediated by enhancing Ser-294 phosphorylation.

Down-regulation of tripartite-motif containing 22 expression in breast cancer is associated with a lack of p53-mediated induction

Tripartite-motif containing 22 (TRIM22) is a direct p53 target gene and inhibits the clonogenic growth of leukemic cells. Its expression in Wilms tumors is negatively associated with disease relapse. This study addresses if TRIM22 expression is de-regulated in breast carcinoma. Western blotting analysis of a panel of 10 breast cancer cell lines and 3 non-malignant mammary epithelial cell lines with a well-characterized TRIM22 monoclonal antibody showed that TRIM22 protein is greatly under-expressed in breast cancer cells as compared to non-malignant cell lines. Similarly, TRIM22 protein is significantly down-regulated in breast tumors as compared to matched normal breast tissues. Study of cell lines with methylation inhibitor and bisulfite sequencing indicates that TRIM22 promoter hypermethylation may not be the cause for TRIM22 under-expression in breast cancer. Instead, we found that TRIM22 protein level correlates strongly (R=0.79) with p53 protein level in normal breast tissue, but this correlation is markedly impaired (R=0.48) in breast cancer tissue, suggesting that there is some defects in p53 regulation of TRIM22 gene in breast cancer. This notion is supported by cell line studies, which showed that TRIM22 was no longer inducible by p53-activating genotoxic drugs in breast cancer cell lines and in a p53 null cell line H1299 transfected with wild type p53. In conclusion, this study shows that TRIM22 is greatly under-expressed in breast cancer. p53 dysfunction may be one of the mechanisms for TRIM22 down-regulation.

Anti-estrogenic mechanism of unliganded progesterone receptor isoform B in breast cancer cells

Over half of breast cancer cases are estrogen-dependent and strategies to combat estrogen-dependent breast cancer have been to either block the activation of estrogen receptor (ER) or diminish the supply of estrogens. Our previous work documented that estrogen-independent expression of progesterone receptor (PR) in MCF-7 cells markedly disrupted the effects of estrogen. In this study, we have developed an adenovirus-mediated gene delivery system to study the specific involvement of PR isoform A (PR-A) and PR-B in the anti-estrogenic effect and its mechanism of action. The results revealed that PR-B, but not PR-A, exhibited distinct anti-estrogenic effect on E2-induced cell growth, gene expression, and ER-ERE interaction in a ligand-independent manner. The anti-estrogenic effect of PR-B was also associated with heightened metabolism and increased cellular uptake of estradiol-17 beta (E2). We have also found that the B-upstream segment of PR-B alone was able to inhibit E2-induced ER-ERE interaction and cellular uptake of E2. Although PR-A alone did not affect E2-induced ER activity, it antagonized the anti-estrogenic effect of PR-B in a concentration-dependent manner. The findings suggest an important mechanism of maintaining a favorable level of ER activity by PR-A and PR-B in estrogen target cells for optimal growth and differentiation. The potential anti-estrogenic mechanism of PR-B may be exploited for breast cancer therapy.

In silico modelling of hormone response elements

BACKGROUND

An important step in understanding the conditions that specify gene expression is the recognition of gene regulatory elements. Due to high diversity of different types of transcription factors and their DNA binding preferences, it is a challenging problem to establish an accurate model for recognition of functional regulatory elements in promoters of eukaryotic genes.

RESULTS

We present a method for precise prediction of a large group of transcription factor binding sites - steroid hormone response elements. We use a large training set of experimentally confirmed steroid hormone response elements, and adapt a sequence-based statistic method of position weight matrix, for identification of the binding sites in the query sequences. To estimate the accuracy level, a table of correspondence of sensitivity vs. specificity values is constructed from a number of independent tests. Furthermore, feed-forward neural network is used for cross-verification of the predicted response elements on genomic sequences.

CONCLUSION

The proposed method demonstrates high accuracy level, and therefore can be used for prediction of hormone response elements de novo. Experimental results support our analysis by showing significant improvement of the proposed method over previous HRE recognition methods.

Establishing a statistic model for recognition of steroid hormone response elements

Identification of hormone response elements (HREs) is essential for understanding the mechanism of hormone-regulated gene expression. To date, there has been a lack of effective bioinformatics tools for recognition of specific HRE such as Progesterone Response Elements (PRE). In this paper, a comprehensive survey and comparison of in silico methods is conducted for establishing a more accurate statistic model. Homogeneity of steroid HRE is analyzed and a reliable training dataset is constructed through extensive searching for experimentally validated response elements from more than 150 literature sources. Based on the observation that the verified HREs carry di-nucleotide preservation in comparison with uniform nucleotide distributions, both mono and di-nucleotide Position Weight Matrices are computed to extract the statistic pattern of the positions. It is followed by the sequence transition pattern recognition using a specifically designed profile Hidden Markov Model. Reciprocal combination of the statistic and transition patterns significantly improves the performance of the model in terms of higher sensitivity and specificity. Upon acquisition of the putative response elements in the promoter areas of vertebrate genes, a qualitative scheme is applied to assess the probability for each gene to be a hormone primary target. Using >650 records of experimentally validated steroid hormone response elements, a high sensitivity level of 73% and high specificity level of one prediction per 8.24 kb is reached, allowing this model to be used for further prediction of primary target genes through the analysis of their upstream promoters, for human or other vertebrate genomes of interest. Additional documents, supplementary data and the web-based program developed for response elements prediction are freely available for academic research at . Submission of putative gene promoter regions for recognition of potential regulatory PREs can be as long as 5 kb.

A Novel Antiestrogenic Mechanism in Progesterone Receptor-transfected Breast Cancer Cells

The expression of progesterone receptor (PR) is normally estrogen-dependent, and progesterone is only active in target cells following estrogen exposure. This study revealed that the effect of estrogen was markedly disrupted by estrogen-independent expression of PR. Transfection of PR in estrogen receptor (ER)-positive MCF-7 cells abolished the estradiol-17beta growth stimulatory effect that was observed in the parental cells and the vector-transfected controls in a ligand-independent manner. The antiestrogenic effect was also observed at the level of gene transcription. Estradiol-17beta (E2)-induced gene expression of pS2 and GREB1 was impaired by 50-75% after 24-72 h of E2 treatment in PR-transfected cells. Promoter interference assay revealed that PR transfection drastically inhibited E2-mediated ER binding to estrogen response elements (ERE). The antiestrogenic effects of transfected PR are associated with enhanced metabolism of E2. HPLC analysis of [3H]E2 in the samples indicated that the percentage of [3H]E2 metabolized by PR-transfected cells in 6 h is similar to that by vector-transfected control cells in 24 h (77 and 80%, respectively). The increased metabolism of E2 may, in turn, be caused by increased cellular uptake of E2, as demonstrated by whole cell binding of [3H]E2. The findings open up a new window for a hitherto unknown functional relationship between the PR and ER. The antiestrogenic effect of transfected PR also provides a potential therapeutic strategy for estrogen-dependent breast cancer.