Comparison of Gene Expression Profiles between Keratinocytes, Melanocytes and Fibroblasts

Oral fibroblasts rescue osteogenic differentiation of mesenchymal stem cells after exposure to Zoledronic acid in a paracrine effect

Background: Medication-related osteonecrosis of the jaw is a serious complication that develops in oncologic patients treated with Zoledronic acid. Although used for over 30 years, the influence of Zoledronic acid on bone has been thoroughly investigated, mainly on osteoclasts. While decreasing osteoclast differentiation and function, for many years it was thought that Zoledronic acid increased osteoblast differentiation, thus increasing bone volume. Moreover, despite the influence of soft tissue on the bone healing process, the impact of zoledronic acid on the interaction between soft tissue and bone was not investigated. Aim: Our goal was to investigate the influence of Zoledronic Acid and soft tissue cells on osteogenic differentiation of mesenchymal stem cells (MSCs). Materials and methods: Osteogenic differentiation of MSCs was examined after exposure to Zoledronic Acid. To determine the influence of soft tissue cells on MSCs' osteogenic differentiation, conditioned media from keratinocytes and oral fibroblasts were added to osteogenic medium supplemented with Zoledronic Acid. Proteomic composition of keratinocytes' and fibroblasts' conditioned media were analyzed. Results: Zoledronic Acid decreased osteogenic differentiation of MSCs by seven-fold. The osteogenic differentiation of MSCs was restored by the supplementation of fibroblasts' conditioned medium to osteogenic medium, despite Zoledronic acid treatment. Five osteogenic proteins involved in the TGFβ pathway were exclusively identified in fibroblasts' conditioned medium, suggesting their role in the rescue effect. Conclusion: Oral fibroblasts secrete proteins that enable osteogenic differentiation of MSCs in the presence of Zoledronic Acid.

Comprehensive RNA sequencing in primary murine keratinocytes and fibroblasts identifies novel biomarkers and provides potential therapeutic targets for skin-related diseases

BACKGROUND

Keratinocytes and fibroblasts represent the major cell types in the epidermis and dermis of the skin and play a significant role in maintenance of skin homeostasis. However, the biological characteristics of keratinocytes and fibroblasts remain to be elucidated. The purpose of this study was to compare the gene expression pattern between keratinocytes and fibroblasts and to explore novel biomarker genes so as to provide potential therapeutic targets for skin-related diseases such as burns, wounds, and aging.

METHODS

Skin keratinocytes and fibroblasts were isolated from newborn mice. To fully understand the heterogeneity of gene expression between keratinocytes and fibroblasts, differentially expressed genes (DEGs) between the two cell types were detected by RNA-seq technology. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the known genes of keratinocytes and fibroblasts and verify the RNA-seq results.

RESULTS

Transcriptomic data showed a total of 4309 DEGs (fold-change > 1.5 and q-value < 0.05). Among them, 2197 genes were highly expressed in fibroblasts and included 10 genes encoding collagen, 16 genes encoding transcription factors, and 14 genes encoding growth factors. Simultaneously, 2112 genes were highly expressed in keratinocytes and included 7 genes encoding collagen, 14 genes encoding transcription factors, and 8 genes encoding growth factors. Furthermore, we summarized 279 genes specifically expressed in keratinocytes and 33 genes specifically expressed in fibroblasts, which may represent distinct molecular signatures of each cell type. Additionally, we observed some novel specific biomarkers for fibroblasts such as Plac8 (placenta-specific 8), Agtr2 (angiotensin II receptor, type 2), Serping1 (serpin peptidase inhibitor, clade G, member 1), Ly6c1 (lymphocyte antigen 6 complex, locus C1), Dpt (dermatopontin), and some novel specific biomarkers for keratinocytes such as Ly6a (lymphocyte antigen 6 complex, locus A) and Lce3c (late cornified envelope 3C), Ccer2 (coiled-coil glutamate-rich protein 2), Col18a1 (collagen, type XVIII, alpha 1) and Col17a1 (collagen type XVII, alpha 1). In summary, these data provided novel identifying biomarkers for two cell types, which can provide a resource of DEGs for further investigations.

Inhibitory effect of strawberry geranium (Saxifraga stolonifera) on Toll-like receptor 2-mediated inflammatory response in human skin keratinocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Strawberry geranium (Saxifraga stolonifera [L.] Meeb) has traditionally been used as a drug to treat skin disorders in Japan. However, little is known about its physiological effects on skin keratinocytes.

AIM OF THE STUDY

We investigated the anti-inflammatory effects of a strawberry geranium extract (SGE) on human skin keratinocytes.

MATERIALS AND METHODS

The human keratinocyte cell line, HaCaT, was treated with SGE, and then stimulated with tumor necrosis factor (TNF)-α. The expression of 207 genes related to the innate immune system was analyzed using DNA microarrays. The effect of SGE on the target proteins in primary human epidermal keratinocytes was confirmed by quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. The mechanisms of action and active components involved in the suppressive effect of SGE were evaluated by fractionation and a transcription assay.

RESULTS

The microarray analysis revealed that SGE primarily suppressed Toll-like receptor (TLR)2 expression through procyanidin B2 3,3'-di-O-gallate, without TLR2 downregulation, in TNF-α-stimulated HaCaT cells. SGE suppressed TLR2 expression and interleukin (IL)-8 production induced by TLR2 ligands in primary human epidermal keratinocytes and HaCaT cells. Multiple components downregulating TLR2 expression suppressed the Sp1 activity.

CONCLUSIONS

We identified a novel physiological function of SGE, which suppresses TLR2 expression and TLR2-mediated inflammation in human skin keratinocytes. This study provides significant insights into the anti-inflammatory effect of SGE in human skin.

Primary Ciliary Signaling in the Skin-Contribution to Wound Healing and Scarring

Primary cilia (PC) are solitary, post-mitotic, microtubule-based, and membrane-covered protrusions that are found on almost every mammalian cell. PC are specialized cellular sensory organelles that transmit environmental information to the cell. Signaling through PC is involved in the regulation of a variety of cellular processes, including proliferation, differentiation, and migration. Conversely, defective, or abnormal PC signaling can contribute to the development of various pathological conditions. Our knowledge of the role of PC in organ development and function is largely based on ciliopathies, a family of genetic disorders with mutations affecting the structure and function of PC. In this review, we focus on the role of PC in their major signaling pathways active in skin cells, and their contribution to wound healing and scarring. To provide comprehensive insights into the current understanding of PC functions, we have collected data available in the literature, including evidence across cell types, tissues, and animal species. We conclude that PC are underappreciated subcellular organelles that significantly contribute to both physiological and pathological processes of the skin development and wound healing. Thus, PC assembly and disassembly and PC signaling may serve as attractive targets for antifibrotic and antiscarring therapies.

OVOL2 induces mesenchymal-to-epithelial transition in fibroblasts and enhances cell-state reprogramming towards epithelial lineages

Mesenchymal-to-epithelial transition (MET) is an important step in cell reprogramming from fibroblasts (a cell type frequently used for this purpose) to various epithelial cell types. However, the mechanism underlying MET induction in fibroblasts remains to be understood. The present study aimed to identify the transcription factors (TFs) that efficiently induce MET in dermal fibroblasts. OVOL2 was identified as a potent inducer of key epithelial genes, and OVOL2 cooperatively enhanced MET induced by HNF1A, TP63, and KLF4, which are known reprogramming TFs to epithelial lineages. In TP63/KLF4-induced keratinocyte-like cell-state reprogramming, OVOL2 greatly facilitated the activation of epithelial and keratinocyte-specific genes. This was accompanied by enhanced changes in chromatin accessibility across the genome. Mechanistically, motif enrichment analysis revealed that the target loci of KLF4 and TP63 become accessible upon induction of TFs, whereas the OVOL2 target loci become inaccessible. This indicates that KLF4 and TP63 positively regulate keratinocyte-associated genes whereas OVOL2 suppresses fibroblast-associated genes. The exogenous expression of OVOL2 therefore disrupts fibroblast lineage identity and facilitates fibroblast cell reprogramming into epithelial lineages cooperatively with tissue-specific reprogramming factors. Identification of OVOL2 as an MET inducer and an epithelial reprogramming enhancer in fibroblasts provides new insights into cellular reprogramming improvement for future applications.

Cultured Epidermal Melanocyte Transplantation in Vitiligo: A Review Article

BACKGROUND

The color of the skin is highly heritable but can be influenced by the environments and endocrine factors. Many other factors, sometimes destructive, are also involved in the formation of skin color, which sometimes affects pigmentation patterns. Vitiligo is an autoimmune hypopigmentation painless disorder with appearance of white patches and psychological effects on patients. It is a disease in which melanocytes of the skin are destroyed in certain areas; therefore depigmentation appears.

METHODS

We studied more than 60 articles. Several therapeutic methods have been used to return the color of skin in vitiligo. These methods include non-invasive treatment and surgical techniques. Among all these therapies, cell transplantation is an advanced procedure in regenerative medicine. Extraction of melanocytes from normal skin and then their cultivation in the laboratory provides a large number of these cells, the transplanting of which to depigmentation areas stimulates the site to irreversibly produce melanin.

RESULTS

The transplantation methods of these cells have been evolved over many years and the methods of producing blister have been changed to the injection of these cells to the target sites.

CONCLUSION

In this review, autologous cultured melanocyte transplantation has been considered to be the most viable, safe, and effective method in the history of vitiligo treatments.

Possible Role of Single Stranded DNA Binding Protein 3 on Skin Hydration by Regulating Epidermal Differentiation

Background

Skin hydration is a common problem both in elderly and young people as dry skin may cause irritation, dermatological disorders, and wrinkles. While both genetic and environmental factors seem to influence skin hydration, thorough genetic studies on skin hydration have not yet been conducted.

Objective

We used a genome-wide association study (GWAS) to explore the genetic elements underlying skin hydration by regulating epidermal differentiation and skin barrier function.

Methods

A GWAS was conducted to investigate the genetic factors influencing skin hydration in 100 Korean females along with molecular studies of genes in human epidermal keratinocytes for functional study in vitro.

Results

Among several single nucleotide polymorphisms identified in GWAS, we focused on Single Stranded DNA Binding Protein 3 (SSBP3) which is associated with DNA replication and DNA damage repair. To better understand the role of SSBP3 in skin cells, we introduced a calcium-induced differentiation keratinocyte culture system model and found that SSBP3 was upregulated in keratinocytes in a differentiation dependent manner. When SSBP3 was overexpressed using a recombinant adenovirus, the expression of differentiation-related genes such as loricrin and involucrin was markedly increased.

Conclusion

Taken together, our results suggest that genetic variants in the intronic region of SSBP3 could be determinants in skin hydration of Korean females. SSBP3 represents a new candidate gene to evaluate the molecular basis of the hydration ability in individuals.

Are the Effects of the Cholera Toxin and Isoproterenol on Human Keratinocytes' Proliferative Potential Dependent on Whether They Are Co-Cultured with Human or Murine Fibroblast Feeder Layers?

Human keratinocyte culture has provided the means to treat burns, wounds and skin pathologies. To date, to efficiently culture keratinocytes, cells are cultured on an irradiated feeder layer (iFL), either comprising human (iHFL) or murine (i3T3FL) fibroblasts, and the culture medium is supplemented with a cyclic adenosine monophosphate (cAMP) accumulation inducing agent such as isoproterenol (ISO) or cholera toxin (CT). Previous studies have characterized how the feeder layer type and the cAMP inducer type influence epithelial cells' phenotype independently from one another, but it is still unknown if an optimal combination of feeder layer and cAMP inducer types exists. We used sophisticated statistical models to search for a synergetic effect of feeder layer and cAMP inducer types on human keratinocytes' proliferative potential. Our data suggests that, when culturing human keratinocytes, using iHFL over i3T3FL increases population doublings and colony-forming efficiency through signaling pathways involving Ak mouse strain thymoma (Akt, also known as protein kinase B) isoforms 1 to 3, signal transducer and activator of transcription 5 (STAT5), p53, and adenosine monophosphate activated protein kinase α1 (AMPKα1). Both tested cAMP inducers ISO and CT yielded comparable outcomes. However, no significant synergy between feeder layer and cAMP inducer types was detected. We conclude that, to promote human keratinocyte growth in the early passages of culture, co-culturing them with a human feeder layer is preferable to a murine feeder layer.

Identification of tissue damage, extracellular matrix remodeling and bacterial challenge as common mechanisms associated with high-risk cutaneous squamous cell carcinomas

In this study we used a genetic extracellular matrix (ECM) disease to identify mechanisms associated with aggressive behavior of cutaneous squamous cell carcinoma (cSCC). cSCC is one of the most common malignancies and usually has a good prognosis. However, some cSCCs recur or metastasize and cause significant morbidity and mortality. Known factors that are associated with aggressiveness of cSCCs include tumor grading, size, localization and microinvasive behavior. To investigate molecular mechanisms that influence biologic behavior we used global proteomic and histologic analyses of formalin-fixed paraffin-embedded tissue of primary human cSCCs. We compared three groups: non-recurring, non-metastasizing low-risk sporadic cSCCs; metastasizing sporadic cSCCs; and cSCCs from patients with recessive dystrophic epidermolysis bullosa (RDEB). RDEB is a genetic skin blistering and ECM disease caused by collagen VII deficiency. Patients commonly suffer from high-risk early onset cSCCs that frequently metastasize. The results indicate that different processes are associated with formation of RDEB cSCCs compared to sporadic cSCCs. Sporadic cSCCs show signs of UV damage, whereas RDEB cSCCs have higher mutational rates and display tissue damage, inflammation and subsequent remodeling of the dermal ECM as tumor initiating factors. Interestingly the two high-risk groups - high-risk metastasizing sporadic cSCCs and RDEB cSCCs - are both associated with tissue damage and ECM remodeling in gene-ontology enrichment and Search Tool for the Retrieval of Interacting Genes/Proteins analyses. In situ histologic analyses validate these results. The high-risk cSCCs also show signatures of enhanced bacterial challenge. Histologic analyses confirm correlation of bacterial colonization with worse prognosis. Collectively, this unbiased study - performed directly on human patient material - reveals that common microenvironmental alterations linked to ECM remodeling and increased bacterial challenges are denominators of high-risk cSCCs. The proteins identified here could serve as potential diagnostic markers and therapeutic targets in high-risk cSCCs.

Coffee, tea and caffeine intake and the risk of non-melanoma skin cancer: a review of the literature and meta-analysis

PURPOSE

Laboratory studies suggested that caffeine and other nutrients contained in coffee and tea may protect against non-melanoma skin cancer (NMSC). However, epidemiological studies conducted so far have produced conflicting results.

METHODS

We performed a literature review and meta-analysis of observational studies published until February 2016 that investigated the association between coffee and tea intake and NMSC risk. We calculated summary relative risk (SRR) and corresponding 95 % confidence intervals (95 % CI) by using random effects with maximum likelihood estimation.

RESULTS

Overall, 37,627 NMSC cases from 13 papers were available for analysis. Intake of caffeinated coffee was inversely associated with NMSC risk (SRR for those in the highest vs. lowest category of intake: 0.82, 95 % CI 0.75-0.89, I ² = 48 %), as well as intake of caffeine (SRR 0.86, 95 % CI 0.80-0.91, I ² = 48 %). In subgroup analysis, these associations were limited to the basal cell cancer (BCC) histotype. There was no association between intake of decaffeinated coffee (SRR 1.01, 95 % CI 0.85-1.21, I ² = 0) and tea (0.88, 95 % CI 0.72-1.07, I ² = 0 %) and NMSC risk. There was no evidence of publication bias affecting the results. The available evidence was not sufficient to draw conclusions on the association between green tea intake and NMSC risk.

CONCLUSIONS

Coffee intake appears to exert a moderate protective effect against BCC development, probably through the biological effect of caffeine. However, the observational nature of studies included, subject to bias and confounding, suggests taking with caution these results that should be verified in randomized clinical trials.

Sox9 is a β-catenin-regulated transcription factor that enhances the colony-forming activity of squamous cell carcinoma cells

Squamous cell carcinoma (SCC) is a common skin cancer, of which the incidence is relatively high, ranking second among the non‑melanoma skin cancers. It is known that numerous intracellular signal regulators are involved in the pathogenesis of SCC. The Wnt/β-catenin signaling pathway serves an important role in cancer development. However, the downstream effectors of β‑catenin remain to be clearly elucidated yet. The present study investigated the functional importance of Wnt/β‑catenin signaling in cutaneous SCC. β‑catenin expression was reduced using recombinant adenovirus expressing specific microRNA (miR). Knockdown of β‑catenin resulted in a marked reduction of the colony-forming activity of the SCC cells, SCC12. In an attempt to identify the β‑catenin downstream genes, it was found that Sox9 was regulated by β‑catenin in SCC12 cells. Overexpression of a constitutively active form of β‑catenin led to the induction of Sox9, while knockdown of β‑catenin resulted in downregulation of Sox9. When the expression of Sox9 was reduced using specific miR, colony-forming activity of the SCC12 cells was significantly reduced. When Sox9 was overexpressed in cells where β‑catenin was knocked down, it partially restored the colony‑forming potential. Taken together, the present results suggested that Sox9 is a β-catenin downstream transcription factor and is positively involved in SCC development.

LINE-1 hypomethylation and mutational status in cutaneous melanomas

Epigenetic dysregulation is an important emerging hallmark of cutaneous melanoma development. The global loss of DNA methylation in gene-poor regions and transposable DNA elements of cancer cells contributes to increased genomic instability. Long interspersed element-1 (LINE-1) sequences are the most abundant repetitive sequence of the genome and can be evaluated as a surrogate marker of the global level of DNA methylation. In this work, LINE-1 methylation levels were evaluated in cutaneous melanomas and normal melanocyte primary cell cultures to investigate their possible association with both distinct clinicopathological characteristics and tumor mutational profile. A set of driver mutations frequently identified in cutaneous melanoma was assessed by sequencing (actionable mutations in BRAF, NRAS, and KIT genes, and mutations affecting the TER T promoter) or multiplex ligation-dependent probe amplification (MLPA) (CDKN2A deletions). Pyrosequencing was performed to investigate the methylation level of LINE-1 and CDKN2A promoter sequences. The qualitative analysis showed a trend toward an association between LINE-1 hypomethylation and CDKN2A inactivation (p=0.05). In a quantitative approach, primary tumors, mainly the thicker ones (>4 mm), exhibited a trend toward LINE-1 hypomethylation when compared with control melanocytes. To date, this is the first study reporting in cutaneous melanomas a possible link between the dysregulation of LINE-1 methylation and the presence of driver mutations.

Identification of a possible susceptibility locus for UVB-induced skin tanning phenotype in Korean females using genomewide association study

A two-stage genomewide association (GWA) analysis was conducted to investigate the genetic factors influencing ultraviolet (UV)-induced skin pigmentation in Korean females after UV exposure. Previously, a GWA study evaluating ~500 000 single nucleotide polymorphisms (SNPs) in 99 Korean females identified eight SNPs that were highly associated with tanning ability. To confirm these associations, we genotyped the SNPs in an independent replication study (112 Korean females). We found that a novel SNP in the intron of the WW domain-containing oxidoreductase (WWOX) gene yielded significant replicated associations with skin tanning ability (P-value = 1.16 × 10(-4) ). To understand the functional consequences of this locus located in the non-coding region, we investigated the role of WWOX in human melanocytes using a recombinant adenovirus expressing a microRNA specific for WWOX. Inhibition of WWOX expression significantly increased the expression and activity of tyrosinase in human melanocytes. Taken together, our results suggest that genetic variants in the intronic region of WWOX could be determinants in the UV-induced tanning ability of Korean females. WWOX represents a new candidate gene to evaluate the molecular basis of the UV-induced tanning ability in individuals.

Inhibitory effect of Paeonia lactiflora Pallas extract (PE) on poly (I:C)-induced immune response of epidermal keratinocytes

Epidermal keratinocytes provide protective role against external stimuli by barrier formation. In addition, kertinocytes exerts their role as the defense cells via activation of innate immunity. Disturbance of keratinocyte functions is related with skin disorders. Psoriasis is a common skin disease related with inflammatory reaction in epidermal cells. We attempted to find therapeutics for psoriasis, and found that Paeonia lactiflora Pallas extract (PE) has an inhibitory potential on poly (I:C)-induced inflammation of keratinocytes. PE significantly inhibited poly (I:C)-induced expression of crucial psoriatic cytokines, such as IL-6, IL-8, CCL20 and TNF-α, via down-regulation of NF-κB signaling pathway in human keratinocytes. In addition, PE significantly inhibited poly (I:C)-induced inflammasome activation, in terms of IL-1β and caspase-1 secretion. Finally, PE markedly inhibited poly (I:C)-increased NLRP3, an important component of inflammasome. These results indicate that PE has an inhibitory effect on poly (I:C)-induced inflammatory reaction of keratinocytes, suggesting that PE can be developed for the treatment of psoriasis.

Inhibitory effect of cucurbitacin B on imiquimod-induced skin inflammation

Psoriasis is a common skin disease, of which pathogenesis involves the increase of inflammatory reaction in epidermal cells. In an attempt to find therapeutics for psoriasis, we found that cucurbitacin B has an inhibitory potential on imiquimod-induced inflammation of keratinocytes. Cucurbitacin B significantly inhibited imiquimod-induced expression of crucial psoriatic cytokines, such as IL-8 and CCL20, via down-regulation of NF-κB and STAT3 signaling pathway in human keratinocytes. In addition, keratinocyte proliferation was markedly inhibited by cucurbitacin B. The potential beneficial effect of cucurbitacin B on psoriasis was further validated in imiquimod-induced psoriasiform dermatitis of experimental animal. Topical application of cucurbitacin B resulted in significant reduction of epidermal hyperplasia and inflammatory cytokines production, and ameliorated the psoriatic symptom. Taken together, these results suggest that cucurbitacin B may be a potential candidate for the treatment of psoriasis.

Melanocytes in the skin--comparative whole transcriptome analysis of main skin cell types

Melanocytes possess several functions besides a role in pigment synthesis, but detailed characteristics of the cells are still unclear. We used whole transcriptome sequencing (RNA-Seq) to assess differential gene expression of cultivated normal human melanocytes with respect to keratinocytes, fibroblasts and whole skin. The present results reveal cultivated melanocytes as highly proliferative cells with possible stem cell-like properties. The enhanced readiness to regenerate makes melanocytes the most vulnerable cells in the skin and explains their high risk of developing into malignant melanoma.

Regulation of keratinocyte differentiation by O-GlcNAcylation

BACKGROUND

O-linked β-N-acetylglucosamine (O-GlcNAc) modification is one of the posttranslational modification, emerging as an important regulatory mechanism in various cellular events.

OBJECTIVE

We attempted to investigate whether O-GlcNAcylation is involved in keratinocyte differentiation.

METHODS

Immunohistochemistry and Western blot were performed to demonstrate O-GlcNAcylation in keratinocyte differentiation.

RESULTS

During calcium-induced keratinocyte differentiation, overall O-GlcNAcylation was decreased in a temporal manner. We focused our attention on transcription factor Sp-1, which is implicated in keratinocyte differentiation. Total Sp-1 level did not change during keratinocyte differentiation. However, O-GlcNAcylated Sp-1 was decreased in a keratinocyte differentiation-dependent manner. Interestingly, transcriptional activity of Sp-1, in terms of involucrin and loricrin promoter activities, was markedly increased by overexpression of O-GlcNAcase (OGA). In addition, membrane permeable non-O-GlcNAcylated Sp-1 did show transcriptional activity, while membrane permeable O-GlcNAcylated Sp-1 did not, suggesting O-GlcNAcylated Sp-1 is an inactive form in keratinocyte differentiation.

CONCLUSION

Our results reveal that O-GlcNAcylation is a dynamic regulatory mechanism for keratinocyte differentiation.

Nrf2 negatively regulates melanogenesis by modulating PI3K/Akt signaling

Nrf2 plays a role in protection of cells against oxidative stress and xenobiotic damage by regulating cytoprotective genes. In this study, we investigated the effect of Nrf2 on melanogenesis in normal human melanocytes (NHMCs). When NHMCs were transduced with a recombinant adenovirus expressing Nrf2, melanin synthesis was significantly decreased. Consistent with this result, overexpression of Nrf2 decreased the expression of tyrosinase and tyrosinase-related protein 1. The inhibitory effect of Nrf2 was reversed by overexpression of Keap1, an intracellular regulator of Nrf2. Interestingly, Nrf2 overexpression resulted in marked activation of PI3K/Akt signaling. Conversely, inhibition of PI3K activity by treatment with wortmannin reversed the depigmentary effects of Nrf2. Taken together, these results strongly suggest that Nrf2 negatively regulates melanogenesis by modulating the PI3K/Akt signaling pathway.

Imiquimod induces apoptosis of squamous cell carcinoma (SCC) cells via regulation of A20

Imiquimod, a nucleoside analogue of the imidazoquinoline family, is being used to treat various cutaneous cancers including squamous cell carcinoma (SCC). Imiquimod activates anti-tumor immunity via Toll-like receptor 7 (TLR7) in macrophage and other immune cells. Imiquimod can also affect tumor cells directly, regardless of its impact on immune system. In this study, we demonstrated that imiquimod induced apoptosis of SCC cells (SCC12) and A20 was involved in this process. When A20 was overexpressed, imiquimod-induced apoptosis was markedly inhibited. Conversely, knockdown of A20 potentiated imiquimod-induced apoptosis. Interestingly, A20 counteracted activation of c-Jun N-terminal kinase (JNK), suggesting that A20-regulated JNK activity was possible mechanism underlying imiquimod-induced apoptosis of SCC12 cells. Finally, imiquimod-induced apoptosis of SCC12 cells was taken place in a TLR7-independent manner. Our data provide new insight into the mechanism underlying imiquimod effect in cutaneous cancer treatment.

Inhibitory role of Id1 on TGF-β-induced collagen expression in human dermal fibroblasts

Inhibitor of DNA binding 1 (Id1) is a basic helix-loop-helix (bHLH) protein that has a variety of functional roles in cellular events including differentiation, cell cycle and cancer development. In addition, it has been demonstrated that Id1 is related with TGF-β and Smad signaling in various biological conditions. In this study, we investigated the effect of Id1 on TGF-β-induced collagen expression in human dermal fibroblasts. When Id1-b isoform was overexpressed, TGF-β-induced collagen expression was markedly inhibited. Consistent with this result, Id1-b significantly inhibited TGF-β-induced collagen gel contraction. In addition, Id1-b inhibited TGF-β-induced phosphorylation of Smad2 and Smad3. Finally, immunohistochemistry showed that Id1 expression was decreased in fibrotic skin diseases while TGF-β signaling was increased. Together, these results suggest that Id1 is an inhibitory regulator on TGF-β-induced collagen expression in dermal fibroblasts.