Regulation of TET2 gene expression and 5mC oxidation in breast cancer cells by estrogen signaling.

Estrogen signaling plays important roles in diverse physiological and pathophysiological processes. However, the relationship between estrogen signaling and epigenetic regulation is not fully understood. Here, we explored the effect of estrogen signaling on the expression of Ten-Eleven Translocation (TET) family genes and DNA hydroxylmethylation in estrogen receptor alpha positive (ERα+) breast cancer cells. By analyzing the RNA-seq data, we identified TET2 as an estradiol (E2)-responsive gene in ERα+ MCF7 cells. RT-qPCR and Western blot analyses confirmed that both the mRNA and protein levels of TET2 gene were upregulated in MCF7 cells by E2 treatment. ChIP-seq and qPCR analyses showed that the enrichment of ERα and H3K27ac on the upstream regulatory regions of TET2 gene was increased in MCF7 cells upon E2 treatment. Moreover, E2 treatment also led to a significant increase in the global 5-hydroxymethylcytosine (5hmC) level, while knockout of TET2 abolished such E2-induced 5hmC increase. Conversely, treatment with ICI 182780, a potent and selective estrogen receptor degrader (SERD), inhibited TET2 gene expression and down-regulated the 5hmC level in MCF7 cells. Taken together, our study identified an ERα/TET2/5hmC epigenetic pathway, which may participate in the estrogen-associated physiological and pathophysiological processes.

Tumour suppressor TET2 safeguards enhancers from aberrant DNA methylation and epigenetic reprogramming in ERα-positive breast cancer cells.

Aberrant DNA methylation is an epigenetic hallmark of malignant tumours. The DNA methylation level is regulated by not only DNA methyltransferases (DNMTs) but also Ten-Eleven Translocation (TET) family proteins. However, the exact role of TET genes in breast cancer remains controversial. Here, we uncover that the ERα-positive breast cancer patients with high TET2 mRNA expression had better overall survival rates. Consistently, knockout of TET2 promotes the tumorigenesis of ERα-positive MCF7 breast cancer cells. Mechanistically, TET2 loss leads to aberrant DNA methylation (gain of 5mC) at a large proportion of enhancers, accompanied by significant reduction in H3K4me1 and H3K27ac enrichment. By analysing the epigenetically reprogrammed enhancers, we identify oestrogen responsive element (ERE) as one of the enriched motifs of transcriptional factors. Importantly, TET2 loss impairs 17beta-oestradiol (E2)-induced transcription of the epigenetically reprogrammed EREs-associated genes through attenuating the binding of ERα. Taken together, these findings shed light on our understanding of the epigenetic mechanisms underlying the enhancer reprogramming during breast cancer pathogenesis.

Retraction Note: TET2 inhibits tumorigenesis of breast cancer cells by regulating caspase-4.

This paper has been retracted at the request of the authors.

TET2 inhibits tumorigenesis of breast cancer cells by regulating caspase-4.

Epigenetic regulators have been shown to influence breast cancer progression. However, the detailed mechanism by which TET2 plays the suppressive role in tumorigenesis remains not completely understood. We employed RT-qPCR and westernblot to examine genes expression. Next, the bisulphite sequencing PCR was used to determine the methylation level at CASP4 promoter in the cells. Phenotypically, we utilized growth curve analysis, colony formation in soft agar and xenograft tumor assay to assess tumorigenesis of MCF-7 cell. We found that TET2 knockout enhanced colony formation ability and in vivo tumor formation ability of MCF-7 cell, whereas TET2 depletion not affected the growth rate of MCF-7 cell in the culture. Mechanistically, TET2 loss led to a significant decrease in caspase-4 expression possibly via increasing DNA methylation of CASP4 promoter in MCF-7 cell. To validate, TET2 overexpression led to higher level of caspase-4 in MDA-MB-231 and 293T cells, which was dependent on TET2 enzymatic activity. Finally, we observed that caspase-4 could revert, at least partially, TET2 deletion-induced tumorigenesis of MCF-7. In summary, we reveal a novel mechanism that TET2 suppresses tumorigenesis of breast cancer cells through caspase-4. Our findings will facilitate development of new diagnostic markers or therapeutical therapies for breast cancer.

ERα is a negative regulator of PD-L1 gene transcription in breast cancer.

The programmed death-ligand 1 (PD-L1) expression by tumors results in potent antitumor immune suppression through binding to programmed death-1 (PD-1) on T cells and subsequent inhibition of T cells activity. Although recent pathological studies have shown that PD-L1 is actively expressed in certain ERα-negative breast cancer, little is known about whether ER signaling regulates PD-L1 gene expression. Here, we investigated the relationship between ERα and PD-L1 in breast cancer. Analysis of Comprehensive Cell Line Encyclopedia (CCLE) data showed that the average mRNA level of PD-L1 in ERα-positive breast cancer cell lines was significantly lower than that in ERα-negative breast cancer cell lines. E2 treatment inhibited PD-L1 mRNA expression in hormone-depleted ERα-positive MCF7 cells. Moreover, ectopic expression of ERα in triple-negative MDA-MB-231 cells reduced PD-L1 mRNA and protein expression. Consistently, analysis of The Cancer Genome Atlas (TCGA) data revealed an inverse correlation between ERα and PD-L1 expression in ERα-positive breast cancer. Taken together, our results identify ERα as a negative regulator of PD-L1 gene transcription in breast cancer cells, suggesting that ERα loss-of-function may facilitate the immune evasion of breast cancer cells via up-regulation of PD-L1.

C-FLIPL Modulated Wnt/ß-Catenin Activation via Association with TIP49 Protein.

Cellular FLICE-like inhibitory protein (c-FLIPL) is a key inhibitory protein in the extrinsic apoptotic pathway. Recent studies showed that c-FLIPL could translocate into the nucleus and might be involved in the Wnt signaling pathway. The nuclear function of c-FLIPL was still unclear. Here we found a novel c-FLIPL-associated protein TIP49, which is a nuclear protein identified as a cofactor in the transcriptional regulation of ß-catenin. They had co-localization in the nucleus and the DED domain of c-FLIPL was required for the association with TIP49. By performing ChIP experiments, C-FLIPL was detected in the ITF-2 locus and facilitated TIP49 accumulation in the formation of complexes at the T-cell-specific transcription factor site of human ITF-2 promoter. When TIP49 knockdown, c-FLIPL-driven Wnt activation, and cell proliferation were inhibited, suggesting that a role of nuclear c-FLIPL involved in modulation of the Wnt pathway was in a TIP49-dependent manner. Elevated expression of c-FLIPL and TIP49 that coincided in human lung cancers were analyzed in silico using the Oncomine database. Their high expressions were reconfirmed in six lung cancer cell lines and correlated with cell growth. The association of c-FLIPL and TIP49 provided an additional mechanism involved in c-FLIPL-mediated functions, including Wnt activation.

A novel dermal matrix generated from burned skin as a promising substitute for deep-degree burns therapy.

The extensive skin defects induced by severe burns are dangerous and can be fatal. Currently, the most common therapy is tangential excision to remove the necrotic or denatured areas of skin, followed by skin grafting. Xenogeneic dermal substitutes, such as porcine acellular dermal matrix (ADM), are typically used to cover the burn wounds, and may accelerate wound healing. It is assumed that burned skin that still maintains partial biological activity may be recycled to construct an autologous acellular dermal matrix, termed 'deep­degree burned dermal matrix (DDBDM)'. In theory, DDBDM may avoid the histoincompatibility issues associated with foreign or xenogeneic dermal matrices, and reduce therapy costs by making full use of discarded skin. In the present study, the collagens within prepared DDBDM were thickened, disorganized and partially fractured, however, they still maintained their reticular structure and tensile strength (P<0.01). Through microarray analysis of the cytokines present in ADM and DDBDM, it was determined that the DDBDM did not produce excessive levels of harmful burn toxins. Following 4 weeks of subcutaneous implantation, ADM and DDBDM were incompletely degraded and maintained good integrity. No significant inflammatory reaction or rejection were observed, which indicated that ADM and DDBDM have good histocompatibility. Therefore, DDBDM may be a useful material for the treatment of deep­degree burns.

[Advances in the research of the biological activities of degradation products of extracellular matrix].

ECM is a supporting structure for stabilizing the location of cells and preserving the structure of tissues. Recently, it has been discovered that ECM and its degradation products may exert profound influences on tissues and cells, such as activities of inflammatory cells and immune cells. Angiogenesis may be stimulated or inhibited by degradation products of ECM. Matrikines, liberated by partial proteolysis of ECM macromolecules, are found to regulate cell functional activities and play a significant role in wound healing or tumor invasion. Post-burn denatured dermal matrix is being studied in burn healing now. The study of post-burn denatured or necrotic dermal matrix should be emphasized in future.

[Experimental study on the recycling of denatured acellular dermal matrix after burn].

OBJECTIVE: To explore the feasibility of burn denatured acellular dermal matrix (DADM) as dermal substitute in repairing wounds. METHODS: (1) Nine Wistar rats received a deep partial-thickness scald on the back. Full-thickness wounded skin was collected on post scald day (PBD) 1, 2, and 3 (with 3 rats at each time point), and it was treated with 2.5 g/L trypsin/0.5% Triton X-100 to remove cells to prepare DADM, respectively called DADM-1 d, DADM-2 d, and DADM-3 d. Another 3 rats without scald injury were treated with the same method as above to prepare acellular dermal matrix (ADM) to serve as control. Gross and histological observations and microbiological and biomechanical tests, including ultimate tensile strength, maximum tension, stretched length at breaking, stress-strain relationship, were conducted for the resulting ADM and DADM. (2) Another 64 rats were divided into ADM group and DADM-1 d, DADM-2 d, and DADM-3 d groups according to the random number table, with 16 rats in each group. A skin flap in size of 2.0 cm×1.8 cm was raised on the back of each rat. The above-mentioned ADM, DADM-1 d, DADM-2 d, and DADM-3 d were cut into pieces in the size of 1.8 cm×1.5 cm, and they were respectively implanted under the skin flaps of rats in corresponding group. At post surgery week (PSW) 1, 3, 5, or 9, 4 rats in each group were used to observe wound healing condition and change in implants with naked eye, and histological observation of the implants was conducted. Data were processed with one-way analysis of variance and t test. RESULTS: (1) The freshly prepared DADM was milky white, soft in texture with flexibility, but poor in elasticity as compared with ADM. No epithelial structure or cellular component was observed in ADM or DADM under light microscope. Collagen fibers of DADM were seen to be thickened unevenly and arranged in disorder and eosinophilic. All microbiological results of DADM were negative. There was no statistically significant difference among DADM-1 d, DADM-2 d, and DADM-3 d in levels of ultimate tensile strength, maximum tension, stretched length at breaking, and stress-strain relationship (with F values from 0.088 to 3.591, P values all above 0.05). Values of the above-mentioned four indexes were the highest in DADM-3 d, they were respectively (13.0 ± 2.4) MPa, (61 ± 4) N, (173 ± 7)%, (45.7 ± 2.0)%. Values of the four indexes of ADM were respectively (19.0 ± 2.6) MPa, (95 ± 4) N, (201 ± 5)%, (62.5 ± 2.2)%, which were higher than those of DADM-1 d, DADM-2 d, and DADM-3 d (with t values from 6.424 to 17.125, P values all below 0.01). (2) No exudate or swelling in the wounds of rats, and no contraction or curling of implants were observed in every group at PSW 1, but inflammatory cells infiltration and Fbs inward migration were observed in the wound. At PSW 3, the growth of hair was normal in the wound in DADM-1 d, DADM-2 d, and ADM groups, but few and scattered hair grew in DADM-3 d group. The inflammatory cells decreased, while Fbs increased, and new capillaries were found to grow inwardly in each group. The decrease in inflammatory cells was slightly delayed in DADM-3 d group. At PSW 5, hair growth became normal, and implants shrank and thinned with fiber membrane wrapped densely and bundles of ingrowing large caliber blood vessels in all groups. The dermal matrix in each group merged with the surrounding normal tissue. At PSW 9, ADM and DADM became white, thin, and soft tissue sheet which was closely connected with the inner side of the flap. There was no infiltration of inflammatory cells in implants in either group. The collagen fibers arranged regularly and densely, and they were integrated with normal collagen tissue. CONCLUSIONS: The burned DADM does not have obvious immunogenicity, but with good biocompatibility. It is prospective to become as a dermal substitute in repairing wounds.

Ro52/SSA sensitizes cells to death receptor-induced apoptosis by down-regulating c-FLIP(L).

Ro52/SSA is an autoantigen that presents in patients with SS (Sjögren's syndrome) and SLE (systemic lupus erythematosus). It increases cell death and redistributes itself to apoptotic blebs, but its pro-apoptotic function has not been completely identified. Overexpression of Ro52/SSA promoted cell apoptosis induced by DR (death receptor) in caspase-8-dependent manner. Ro52/SSA expression down-regulated c-FLIP(L) [cellular (Fas-associated death domain)-like interleukin 1ß-converting enzyme-inhibitory protein long form] expression, and Ro52/SSA siRNAs (small interfering RNAs) increased c-FLIP(L) production, indicating that Ro52/SSA plays a role in c-FLIP(L) regulation. Ro52/SSA negatively regulated c-FLIP(L) transcriptional level probably by suppressing NF-κB (nuclear factor κB) signalling. The data suggest that Ro52/SSA is involved in DR-mediated apoptosis by regulating c-FLIP(L).