Regulation of 5-hydroxymethylcytosine by TET2 contributes to Squamous Cell Carcinoma tumorigenesis

Inhibition of cytosine 5-hydroxymethylation during progression of cancer precursor lesions in the uterine cervix

Methylation and hydroxymethylation of cytosine moieties in CpG islands of specific genes are epigenetic processes shown to be involved in the development of cervical (pre)neoplastic lesions. We studied global (hydroxy)methylation during the subsequent steps in the carcinogenic process of the uterine cervix by using immunohistochemical protocols for the detection of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in paraffin-embedded tissues of the normal epithelia and (pre)malignant lesions. This approach allowed obtaining spatially resolved information of (epi)genetic alterations for individual cell populations in morphologically heterogeneous tissue samples. The normal ectocervical squamous epithelium showed a high degree of heterogeneity for both modifications, with a major positivity for 5-mC in the basal and parabasal layers in the ectocervical region, while 5-hmC immunostaining was even more restricted to the cells in the basal layer. Immature squamous metaplasia, characterized by expression of SOX17, surprisingly showed a decrease of 5-hmC in the basal compartments and an increase in the more superficial layers of the epithelium. The normal endocervical glandular epithelium showed a strong immunostaining reactivity for both modifications. At the squamocolumnar junctions, a specific 5-hmC pattern was observed in the squamous epithelium, resembling that of metaplasia, with the typical weak to negative reaction for 5-hmC in the basal cell compartment. The reserve cells underlying the glandular epithelium were also largely negative for 5-hmC but showed immunostaining for 5-mC. While the overall methylation status remained relatively constant, about 20% of the high-grade squamous lesions showed a very low immunostaining reactivity for 5-hmC. The (pre)malignant glandular lesions, including adenocarcinoma in situ (AIS) and adenocarcinoma showed a progressive decrease of hydroxymethylation with advancement of the lesion, resulting in cases with regions that were negative for 5-hmC immunostaining. These data indicate that inhibition of demethylation, which normally follows cytosine hydroxymethylation, is an important epigenetic switch in the development of cervical cancer.

Decreased TET2/5-hmC reduces the integrity of the epidermal barrier via epigenetic dysregulation of filaggrin in psoriatic lesions

BACKGROUND

TET2 participates in tumor progression and intrinsic immune homeostasis via epigenetic regulation. TET2 has been reported to be involved in maintaining epithelial barrier homeostasis and inflammation. Abnormal epidermal barrier function and TET2 expression have been detected in psoriatic lesions. However, the mechanisms underlying the role of TET2 in psoriasis have not yet been elucidated.

OBJECTIVE

To define the role of TET2 in maintaining epithelial barrier homeostasis and the exact epigenetic mechanism in the dysfunction of the epidermal barrier in psoriasis.

METHODS

We analyzed human psoriatic skin lesions and datasets from the GEO database, and detected the expression of TET2/5-hmC together with barrier molecules by immunohistochemistry. We constructed epidermal-specific TET2 knockout mice to observe the effect of TET2 deficiency on epidermal barrier function via toluidine blue penetration assay. Further, we analyzed changes in the expression of epidermal barrier molecules by immunofluorescence in TET2-specific knockout mice and psoriatic model mice.

RESULTS

We found that decreased expression of TET2/5-hmC correlated with dysregulated barrier molecules in human psoriatic lesions. Epidermal-specific TET2 knockout mice showed elevated transdermal water loss associated with abnormal epidermal barrier molecules. Furthermore, we observed that TET2 knockdown in keratinocytes reduced filaggrin expression via filaggrin promoter methylation.

CONCLUSION

Aberrant epidermal TET2 affects the integrity of the epidermal barrier through the epigenetic dysregulation of epidermal barrier molecules, particularly filaggrin. Reduced TET2 expression is a critical factor contributing to an abnormal epidermal barrier in psoriasis.

Dynamics and Epigenetics of the Epidermal Differentiation Complex

Epidermis is the outer skin layer built of specialized cells called keratinocytes. Keratinocytes undergo a unique differentiation process, also known as cornification, during which their gene expression pattern, morphology and other properties change remarkably to the effect that the terminally differentiated, cornified cells can form a physical barrier, which separates the underlying tissues from the environment. Many genes encoding proteins that are important for epidermal barrier formation are located in a gene cluster called epidermal differentiation complex (EDC). Recent data provided valuable information on the dynamics of the EDC locus and the network of interactions between EDC gene promoters, enhancers and other regions, during keratinocytes differentiation. These data, together with results concerning changes in epigenetic modifications, provide a valuable insight into the mode of regulation of EDC gene expression.

Decrease of 5-hydroxymethylcytosine in primary cutaneous CD4+ small/medium sized pleomorphic T-cell lymphoproliferative disorder

BACKGROUND

Primary cutaneous CD4+ small/medium-sized pleomorphic T-Cell lymphoproliferative disorder (PC-SMTLD) has been considered as a controversial dermatological disease that has been included in cutaneous T-cell lymphoma group, presenting most commonly as a solitary nodule and/or plaque with a specific and characteristic head and neck predilection. Due to the considerable overlap between PC-SMTLD and pseudolymphoma (PL), the differential diagnosis is often challenging. Methylation of DNA at position 5 of cytosine, and the subsequent reduction in intracellular 5-hydroxymethylcytosine (5-hmC) levels, is a key epigenetic event in several cancers, including systemic lymphomas. However, it has rarely been studied in cutaneous lymphomas.

OBJECTIVES

The authors aimed to explore the role of differential 5-hmC immunostaining as a useful marker to distinguish PC-SMTLD from PL.

METHODS

Retrospective case series study with immunohistochemical and immunofluorescence analysis of 5-hmC was performed in PL and PC-SMTLD.

RESULTS

Significant decrease of 5-hmC nuclear staining was observed in PC-SMTLD when compared with PL (p < 0.0001). By semi-quantitative grade integration, there were statistical differences in the final 5-hmC scores in the two study groups. The IF co-staining of 5-hmC with CD4 revealed a decrease of 5-hmC in CD4+ lymphocytes of PC-SMTLD.

STUDY LIMITATIONS

The small clinical sample size of the study.

CONCLUSIONS

The immunorreactivity of 5-hmC in CD4+ lymphocytes was highly suggestive of a benign process as PL. Furthermore, the decrease of 5-hmC nuclear staining in PC-SMTLD indicated its lymphoproliferative status and helped to make the differential diagnosis with PL.

Toward Elucidating Epigenetic and Metabolic Regulation of Stem Cell Lineage Plasticity in Skin Aging

Skin is the largest organ in human body, harboring a plethora of cell types and serving as the organismal barrier. Skin aging such as wrinkling and hair graying is graphically pronounced, and the molecular mechanisms behind these phenotypic manifestations are beginning to unfold. As in many other organs and tissues, epigenetic and metabolic deregulations have emerged as key aging drivers. Particularly in the context of the skin epithelium, the epigenome and metabolome coordinately shape lineage plasticity and orchestrate stem cell function during aging. Our review discusses recent studies that proposed molecular mechanisms that drive the degeneration of hair follicles, a major appendage of the skin. By focusing on skin while comparing it to model organisms and adult stem cells of other tissues, we summarize literature on genotoxic stress, nutritional sensing, metabolic rewiring, mitochondrial activity, and epigenetic regulations of stem cell plasticity. Finally, we speculate about the rejuvenation potential of rate-limiting upstream signals during aging and the dominant role of the tissue microenvironment in dictating aged epithelial stem cell function.

Loss of TET2 Tips the Scales Toward Tumorigenesis

DNA methylation and demethylation function in the balance between cellular differentiation and cancer. Although the roles of DNA methyltransferases have been extensively explored in epidermal biology, ten-eleven translocation (TET) demethylase enzymes are poorly understood. In their new article in the Journal of Investigative Dermatology, Boudra et al. present evidence for a tumor-suppressive role of TET2 and its regulation of 5-hydroxymethylcytosine in the prevention of squamous cell carcinomas.

Ascorbic acid 2-glucoside preconditioning enhances the ability of bone marrow mesenchymal stem cells in promoting wound healing

Background

Nowadays, wound is associated with a complicated repairing process and still represents a significant biomedical burden worldwide. Bone marrow mesenchymal stem cells (BMSCs) possess multidirectional differentiation potential and secretory function, emerging as potential cellular candidates in treating wounds. Ascorbic acid 2-glucoside (AA2G) is a well-known antioxidant and its function in BMSC-promoting wound healing is worth exploring.

Methods

The in vitro cell proliferation, migration, and angiogenesis of BMSCs and AA2G-treated BMSCs were detected by flow cytometry, EDU staining, scratch assay, transwell assay, and immunofluorescence (IF). Besides, the collagen formation effect of AA2G-treated BMSCs conditioned medium (CM) on NIH-3T3 cells was evaluated by hydroxyproline, qRT-PCR and IF staining detection. Next, in the wound healing mouse model, the histological evaluation of wound tissue in PBS, BMSCs, and AA2G-treated BMSCs group were further investigated. Lastly, western blot and ELISA were used to detect the expression levels of 5-hmc, TET2 and VEGF protein, and PI3K/AKT pathway activation in BMSCs treated with or without AA2G.

Results

The in vitro results indicated that AA2G-treated BMSCs exhibited stronger proliferation and improved the angiogenesis ability of vascular endothelial cells. In addition, the AA2G-treated BMSCs CM enhanced migration and collagen formation of NIH-3T3 cells. In vivo, the AA2G-treated BMSCs group had a faster wound healing rate and a higher degree of vascularization in the new wound, compared with the PBS and BMSCs group. Moreover, AA2G preconditioning might enhance the demethylation process of BMSCs by regulating TET2 and up-regulating VEGF expression by activating the PI3K/AKT pathway.

Conclusions

AA2G-treated BMSCs promoted wound healing by promoting angiogenesis and collagen deposition, thereby providing a feasible strategy to reinforce the biofunctionability of BMSCs in treating wounds.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02797-0.