Role of Enzymic Antioxidants in Mediating Oxidative Stress and Contrasting Wound Healing Capabilities in Oral Mucosal/Skin Fibroblasts and Tissues

Unlike skin, oral mucosal wounds are characterized by rapid healing and minimal scarring, attributable to the "enhanced" healing properties of oral mucosal fibroblasts (OMFs). As oxidative stress is increasingly implicated in regulating wound healing outcomes, this study compared oxidative stress biomarker and enzymic antioxidant profiles between patient-matched oral mucosal/skin tissues and OMFs/skin fibroblasts (SFs) to determine whether superior oral mucosal antioxidant capabilities and reduced oxidative stress contributed to these preferential healing properties. Oral mucosa and skin exhibited similar patterns of oxidative protein damage and lipid peroxidation, localized within the lamina propria/dermis and oral/skin epithelia, respectively. SOD1, SOD2, SOD3 and catalase were primarily localized within epithelial tissues overall. However, SOD3 was also widespread within the lamina propria localized to OMFs, vasculature and the extracellular matrix. OMFs were further identified as being more resistant to reactive oxygen species (ROS) generation and oxidative DNA/protein damage than SFs. Despite histological evaluation suggesting that oral mucosa possessed higher SOD3 expression, this was not fully substantiated for all OMFs examined due to inter-patient donor variability. Such findings suggest that enzymic antioxidants have limited roles in mediating privileged wound healing responses in OMFs, implying that other non-enzymic antioxidants could be involved in protecting OMFs from oxidative stress overall.

RNA sequencing and lipidomics uncovers novel pathomechanisms in recessive X-linked ichthyosis

Recessive X-linked ichthyosis (RXLI), a genetic disorder caused by deletion or point mutations of the steroid sulfatase (STS) gene, is the second most common form of ichthyosis. It is a disorder of keratinocyte cholesterol sulfate retention and the mechanism of extracutaneous phenotypes such as corneal opacities and attention deficit hyperactivity disorder are poorly understood. To understand the pathomechanisms of RXLI, the transcriptome of differentiated primary keratinocytes with STS knockdown was sequenced. The results were validated in a stable knockdown model of STS, to confirm STS specificity, and in RXLI skin. The results show that there was significantly reduced expression of genes related to epidermal differentiation and lipid metabolism, including ceramide and sphingolipid synthesis. In addition, there was significant downregulation of aldehyde dehydrogenase family members and the oxytocin receptor which have been linked to corneal transparency and behavioural disorders respectively, both of which are extracutaneous phenotypes of RXLI. These data provide a greater understanding of the causative mechanisms of RXLI's cutaneous phenotype, and show that the keratinocyte transcriptome and lipidomics can give novel insights into the phenotype of patients with RXLI.

Regulation of human trophoblast gene expression by endogenous retroviruses

The placenta is a fast-evolving organ with large morphological and histological differences across eutherians, but the genetic changes driving placental evolution have not been fully elucidated. Transposable elements, through their capacity to quickly generate genetic variation and affect host gene regulation, may have helped to define species-specific trophoblast gene expression programs. Here we assess the contribution of transposable elements to human trophoblast gene expression as enhancers or promoters. Using epigenomic data from primary human trophoblast and trophoblast stem-cell lines, we identified multiple endogenous retrovirus families with regulatory potential that lie close to genes with preferential expression in trophoblast. These largely primate-specific elements are associated with inter-species gene expression differences and are bound by transcription factors with key roles in placental development. Using genetic editing, we demonstrate that several elements act as transcriptional enhancers of important placental genes, such as CSF1R and PSG5. We also identify an LTR10A element that regulates ENG expression, affecting secretion of soluble endoglin, with potential implications for preeclampsia. Our data show that transposons have made important contributions to human trophoblast gene regulation, and suggest that their activity may affect pregnancy outcomes.

Ichthyosis linked to sphingosine 1-phosphate lyase insufficiency is due to aberrant sphingolipid and calcium regulation

Sphingosine 1-phosphate lyase (SGPL1) insufficiency (SPLIS) is a syndrome which presents with adrenal insufficiency, steroid-resistant nephrotic syndrome, hypothyroidism, neurological disease, and ichthyosis. Where a skin phenotype is reported, 94% had abnormalities such as ichthyosis, acanthosis, and hyperpigmentation. To elucidate the disease mechanism and the role SGPL1 plays in the skin barrier we established clustered regularly interspaced short palindromic repeats-Cas9 SGPL1 KO and a lentiviral-induced SGPL1 overexpression (OE) in telomerase reverse-transcriptase immortalised human keratinocytes (N/TERT-1) and thereafter organotypic skin equivalents. Loss of SGPL1 caused an accumulation of S1P, sphingosine, and ceramides, while its overexpression caused a reduction of these species. RNAseq analysis showed perturbations in sphingolipid pathway genes, particularly in SGPL1_KO, and our gene set enrichment analysis revealed polar opposite differential gene expression between SGPL1_KO and _OE in keratinocyte differentiation and Ca2+ signaling genesets. SGPL1_KO upregulated differentiation markers, while SGPL1_OE upregulated basal and proliferative markers. The advanced differentiation of SGPL1_KO was confirmed by 3D organotypic models that also presented with a thickened and retained stratum corneum and a breakdown of E-cadherin junctions. We conclude that SPLIS associated ichthyosis is a multifaceted disease caused possibly by sphingolipid imbalance and excessive S1P signaling, leading to increased differentiation and an imbalance of the lipid lamellae throughout the epidermis.

Investigating wound healing characteristics of gingival and skin keratinocytes in organotypic cultures

OBJECTIVES

The gingiva heals at an accelerated rate with reduced scarring when compared to skin. Potential well-studied factors include immune cell number, angiogenesis disparities and fibroblast gene expression. Differential keratinocyte gene expression, however, remains relatively understudied. This study explored the contrasting healing efficiencies of gingival and skin keratinocytes, alongside their differential gene expression patterns.

METHODS

3D organotypic culture models of human gingiva and skin were developed using temporarily immortalised primary keratinocytes. Models were wounded for visualisation of re-epithelialisation and analysis of keratinocyte migration to close the wound gap. Concurrently, differentially expressed genes between primary gingival and skin keratinocytes were identified, validated, and functionally assessed.

RESULTS

Characterisation of the 3D cultures of gingiva and skin showed differentiation markers that recapitulated organisation of the corresponding in vivo tissue. Upon wounding, gingival models displayed a significantly higher efficiency in re-epithelialisation and stratification versus skin, repopulating the wound gap within 24 hours. This difference was likely due to distinct patterns of migration, with gingival cells demonstrating a form of sheet migration, in contrast to skin, where the leading edge was typically 1-2 cells thick. A candidate approach was used to identify several genes that were differentially expressed between gingival and skin keratinocytes. Knockdown of PITX1 resulted in reduced migration capacity of gingival cells.

CONCLUSION

Gingival keratinocytes retain in vivo superior wound healing capabilities in in vitro 2D and 3D environments. Intrinsic gene expression differences could result in gingival cells being 'primed' for healing and play a role in faster wound resolution.

CLINICAL SIGNIFICANCE STATEMENT

The successful development of organotypic models, that recapitulate re-epithelialisation, will underpin further studies to analyse the oral response to wound stimuli, and potential therapeutic interventions, in an in vitro environment.

3D model of harlequin ichthyosis reveals inflammatory therapeutic targets

The biology of harlequin ichthyosis (HI), a devastating skin disorder caused by loss-of-function mutations in the gene ABCA12, is poorly understood, and to date, no satisfactory treatment has been developed. We sought to investigate pathomechanisms of HI that could lead to the identification of new treatments for improving patients' quality of life. In this study, RNA-Seq and functional assays were performed to define the effects of loss of ABCA12 using HI patient skin samples and an engineered CRISPR/Cas9 ABCA12 KO cell line. The HI living skin equivalent (3D model) recapitulated the HI skin phenotype. The cytokines IL-36α and IL-36γ were upregulated in HI skin, whereas the innate immune inhibitor IL-37 was strongly downregulated. We also identified STAT1 and its downstream target inducible nitric oxide synthase (NOS2) as being upregulated in the in vitro HI 3D model and HI patient skin samples. Inhibition of NOS2 using the inhibitor 1400W or the JAK inhibitor tofacitinib dramatically improved the in vitro HI phenotype by restoring the lipid barrier in the HI 3D model. Our study has identified dysregulated pathways in HI skin that are feasible therapeutic targets.

Distinctive clinical and histological characteristics of atrophic and hypertrophic facial photoageing

BACKGROUND

Photoageing describes complex cutaneous changes which occur following chronic exposure to solar ultraviolet radiation (UVR). Amongst White Northern Europeans, facial photoageing appears as distinct clinical phenotypes: 'hypertrophic' photoageing (HP) and 'atrophic' photoageing (AP). Deep, coarse wrinkles predominate in individuals with HP, whereas those with AP have relatively smooth, unwrinkled skin with pronounced telangiectasia. AP individuals have an increased propensity for developing keratinocyte cancers.

OBJECTIVES

To investigate whether histological differences underlie these distinct phenotypes of facial photoageing.

METHODS

Facial skin biopsies were obtained from participants with AP (10 M, 10 F; mean age: 78.7 years) or HP (10 M, 10 F; mean age: 74.5 years) and were assessed histologically and by immunohistochemistry.

RESULTS

Demographic characterization revealed 95% of AP subjects, as compared to 35% with HP, were Fitzpatrick skin type I/II; of these, 50% had a history of one or more keratinocyte cancers. There was no history of keratinocyte cancers in the HP cohort. Analysis of UVR-induced mitochondrial DNA damage confirmed that all volunteers had received similar lifetime cumulative doses of sun exposure. Histologically, male AP had a significantly thicker epidermis than did AP females or those of either sex with HP. HP facial skin exhibited severe solar elastosis, whereas in AP facial skin, solar elastosis was apparent only in females. Loss of papillary dermal fibrillin-rich microfibrils occurred in all HP and AP female subjects, but not in AP males. Furthermore, male AP had a significant reduction in collagen VII at the dermal-epidermal junction than did AP females or those of either sex with HP.

CONCLUSIONS

This study provides further evidence that AP and HP represent distinct clinical and histological entities. Knowledge of these two phenotypes is clinically relevant due to the increased prevalence of keratinocyte cancers in those - particularly males - with the AP phenotype.

Loss of the laminin subunit alpha-3 induces cell invasion and macrophage infiltration in cutaneous squamous cell carcinoma

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is a common cancer that invades the dermis through the basement membrane. The role of the basement membrane in poorly differentiated cSCC is not well understood.

OBJECTIVES

To study the effect that loss of the laminin subunit alpha-3 (α3) chain from the tumour microenvironment has on tumour invasion and inflammatory cell recruitment.

METHODS

We examined the role of the basement membrane proteins laminin subunits α3, β3 and γ2 in SCC invasion and inflammatory cell recruitment using immunohistochemistry, short hairpin RNA knockdown, RNA-Seq, mouse xenograft models and patient tumour samples.

RESULTS

Analysis of SCC tumours and cell lines using antibodies specific to laminin chains α3, β3 and γ2 identified a link between poorly differentiated SCC and reduced expression of laminin α3 but not the other laminin subunits investigated. Knockdown of laminin α3 increased tumour invasion both in vitro and in vivo. Western blot and immunohistochemical staining identified increased phosphorylated myosin light chain with loss of laminin α3. Inhibition of ROCK (rho-associated protein kinase) but not Rac1 significantly reduced the invasive potential of laminin α3 knockdown cells. Knockdown of laminin subunits α3 and γ2 increased monocyte recruitment to the tumour microenvironment. However, only the loss of laminin α3 correlated with increased tumour-associated macrophages both in xenografted tumours and in patient tumour samples.

CONCLUSIONS

These data provide evidence that loss of the laminin α3 chain in cSCC has an effect on both the epithelial and immune components of cSCC, resulting in an aggressive tumour microenvironment.

Suppression of TGFβ and Angiogenesis by Type VII Collagen in Cutaneous SCC

BACKGROUND

Individuals with severe generalized recessive dystrophic epidermolysis bullosa (RDEB), an inherited blistering disorder caused by mutations in the COL7A1 gene, develop unexplained aggressive squamous cell carcinomas (SCC). Here we report that loss of type VII collagen (Col7) in SCC results in increased TGFβ signaling and angiogenesis in vitro and in vivo.

METHODS

Stable knockdown (KD) of Col7 was established using shRNA, and cells were used in a mouse xenograft model. Angiogenesis was assessed by immunohistochemistry, endothelial tube-forming assays, and proteome arrays. Mouse and zebrafish models were used to examine the effect of recombinant Col7 on angiogenesis. Findings were confirmed in anonymized, archival human tissue: RDEB SCC tumors, non-EB SCC tumors, RDEB skin, normal skin; and two human RDEB SCC cell lines. The TGFβ pathway was examined using immunoblotting, immunohistochemistry, biochemical inhibition, and siRNA. All statistical tests were two-sided.

RESULTS

Increased numbers of cross-cut blood vessels were observed in Col7 KD compared with control xenografts (n = 4 to 7 per group) and in RDEB tumors (n = 21) compared with sporadic SCC (n = 24, P < .001). Recombinant human Col7 reversed the increased SCC angiogenesis in Col7 KD xenografts in vivo (n = 7 per group, P = .04). Blocking the interaction between α2β1 integrin and Col7 increased TGFB1 mRNA expression 1.8-fold and p-Smad2 levels two-fold. Increased TGFβ signaling and VEGF expression were observed in Col7 KD xenografts (n = 4) compared with control (n = 4) and RDEB tumors (TGFβ markers, n = 6; VEGF, n = 17) compared with sporadic SCC (TGFβ markers, n = 6; VEGF, n = 21). Inhibition of TGFβ receptor signaling using siRNA resulted in decreased endothelial cell tube formation (n = 9 per group, mean tubes per well siC = 63.6, SD = 17.1; mean tubes per well siTβRII = 29.7, SD = 6.1, P = .02).

CONCLUSIONS

Type VII collagen suppresses TGFβ signaling and angiogenesis in cutaneous SCC. Patients with RDEB SCC may benefit from anti-angiogenic therapy.

A Novel Fully Humanized 3D Skin Equivalent to Model Early Melanoma Invasion

Metastatic melanoma remains incurable, emphasizing the acute need for improved research models to investigate the underlying biologic mechanisms mediating tumor invasion and metastasis, and to develop more effective targeted therapies to improve clinical outcome. Available animal models of melanoma do not accurately reflect human disease and current in vitro human skin equivalent models incorporating melanoma cells are not fully representative of the human skin microenvironment. We have developed a robust and reproducible, fully humanized three-dimensional (3D) skin equivalent comprising a stratified, terminally differentiated epidermis and a dermal compartment consisting of fibroblast-generated extracellular matrix. Melanoma cells incorporated into the epidermis were able to invade through the basement membrane and into the dermis, mirroring early tumor invasion in vivo. Comparison of our novel 3D melanoma skin equivalent with melanoma in situ and metastatic melanoma indicates that this model accurately recreates features of disease pathology, making it a physiologically representative model of early radial and vertical growth-phase melanoma invasion.

Metalloproteinases and Wound Healing

Significance: Matrix metalloproteinases (MMPs) are present in both acute and chronic wounds. They play a pivotal role, with their inhibitors, in regulating extracellular matrix degradation and deposition that is essential for wound reepithelialization. The excess protease activity can lead to a chronic nonhealing wound. The timed expression and activation of MMPs in response to wounding are vital for successful wound healing. MMPs are grouped into eight families and display extensive homology within these families. This homology leads in part to the initial failure of MMP inhibitors in clinical trials and the development of alternative methods for modulating the MMP activity. MMP-knockout mouse models display altered wound healing responses, but these are often subtle phenotypic changes indicating the overlapping MMP substrate specificity and inter-MMP compensation. Recent Advances: Recent research has identified several new MMP modulators, including photodynamic therapy, protease-absorbing dressing, microRNA regulation, signaling molecules, and peptides. Critical Issues: Wound healing requires the controlled activity of MMPs at all stages of the wound healing process. The loss of MMP regulation is a characteristic of chronic wounds and contributes to the failure to heal. Future Directions: Further research into how MMPs are regulated should allow the development of novel treatments for wound healing.

AGE-modified basement membrane cooperates with Endo180 to promote epithelial cell invasiveness and decrease prostate cancer survival

Biomechanical strain imposed by age-related thickening of the basal lamina and augmented tissue stiffness in the prostate gland coincides with increased cancer risk. Here we hypothesized that the structural alterations in the basal lamina associated with age can induce mechanotransduction pathways in prostate epithelial cells (PECs) to promote invasiveness and cancer progression. To demonstrate this, we developed a 3D model of PEC acini in which thickening and stiffening of basal lamina matrix was induced by advanced glycation end-product (AGE)-dependent non-enzymatic crosslinking of its major components, collagen IV and laminin. We used this model to demonstrate that antibody targeted blockade of CTLD2, the second of eight C-type lectin-like domains in Endo180 (CD280, CLEC13E, KIAA0709, MRC2, TEM9, uPARAP) that can recognize glycosylated collagens, reversed actinomyosin-based contractility [myosin-light chain-2 (MLC2) phosphorylation], loss of cell polarity, loss of cell-cell junctions, luminal infiltration and basal invasion induced by AGE-modified basal lamina matrix in PEC acini. Our in vitro results were concordant with luminal occlusion of acini in the prostate glands of adult Endo180(Δ) (Ex2-6/) (Δ) (Ex2-6) mice, with constitutively exposed CTLD2 and decreased survival of men with early (non-invasive) prostate cancer with high epithelial Endo180 expression and levels of AGE. These findings indicate that AGE-dependent modification of the basal lamina induces invasive behaviour in non-transformed PECs via a molecular mechanism linked to cancer progression. This study provides a rationale for targeting CTLD2 in Endo180 in prostate cancer and other pathologies in which increased basal lamina thickness and tissue stiffness are driving factors. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The receptor tyrosine kinase Axl regulates cell-cell adhesion and stemness in cutaneous squamous cell carcinoma

Axl is a receptor tyrosine kinase (RTK) upregulated in various tumors including cutaneous squamous cell carcinoma (SCC). Axl expression correlates with poor prognosis and induction of epithelial-mesenchymal transition (EMT), hence we hypothesized that Axl is involved in the disruption of cell-cell adhesion to allow invasion and chemotherapy resistance of the cancer stem cell population. Cutaneous SCC cell lines with stable knockdown of Axl were generated using retroviral vectors. Axl depletion altered expression of intercellular junction molecules increasing cell-cell adhesion with downregulation of Wnt and TGFβR signaling. Furthermore, Axl expression correlated with the expression of putative cancer stem cell markers, CD44 and ALDH1, increased resistance to chemotherapy drugs, enhanced sphere formation ability and expression of EMT features by cancer stem cells. Axl depletion resulted in loss of tumor formation in an in vivo zebrafish xenograft model. In conclusion, these data suggest that abrogation of Axl results in loss of cancer stem cell properties indicating a role for Axl as a therapeutic target in chemotherapy-resistant cancer.

miR-23b regulates cytoskeletal remodeling, motility and metastasis by directly targeting multiple transcripts

Uncontrolled cell proliferation and cytoskeletal remodeling are responsible for tumor development and ultimately metastasis. A number of studies have implicated microRNAs in the regulation of cancer cell invasion and migration. Here, we show that miR-23b regulates focal adhesion, cell spreading, cell-cell junctions and the formation of lamellipodia in breast cancer (BC), implicating a central role for it in cytoskeletal dynamics. Inhibition of miR-23b, using a specific sponge construct, leads to an increase of cell migration and metastatic spread in vivo, indicating it as a metastatic suppressor microRNA. Clinically, low miR-23b expression correlates with the development of metastases in BC patients. Mechanistically, miR-23b is able to directly inhibit a number of genes implicated in cytoskeletal remodeling in BC cells. Through intracellular signal transduction, growth factors activate the transcription factor AP-1, and we show that this in turn reduces miR-23b levels by direct binding to its promoter, releasing the pro-invasive genes from translational inhibition. In aggregate, miR-23b expression invokes a sophisticated interaction network that co-ordinates a wide range of cellular responses required to alter the cytoskeleton during cancer cell motility.

Abstract P2-02-03: The Collagen Receptor Endo180: A Metastatic Plasma Marker In Breast Cancer Modulated By Bisphosphonate Treatment

Purpose: To establish whether the collagen remodelling receptor, Endo180, should be given consideration as a useful plasma marker in metastatic breast cancer.

Patients and Methods: Analysis of MCF-7 and MDA-MB-231 cell conditioned medium validated the anti-human (39.10) monoclonal antibody as suitable for the detection of soluble Endo180 in plasma. Eighty-seven breast cancer patients with early primary, locally advanced and metastatic disease were included in the study. Correlations between Endo180, CA 15–3 antigen (MUC1; mucin 1) and bisphosphonate treatment were investigated.

Results: Endo180 was elevated in metastatic compared to early breast cancer (P &lt;.0001) and was able to differentiate locoregional disease and visceral and/or osseous metastasis (P = .0005). In combination CA 15–3 antigen (cut-off: 28 U/mL) and Endo180 (relative plasma level cut-off range: 0.95–1.65) had sensitivity of 94–97% and specificity of 52–68%. Endo180 levels were significantly higher in patients who were treatment naive (2.17 ± 0.82, N = 13) compared to those previously (1.82 ± 0.33, N = 5) or currently (1.37 ± 0.74, N = 24) receiving bisphosphonates (P = .011). In the bisphosphonate naive setting (N = 57) the combination of Endo180 (relative plasma level cut-off range: 0.95–1.65) and CA 15–3 antigen (cut-off: 28 U/mL) had a sensitivity of 87–92% and specificity of 72–79%.

Conclusion: Endo180 is a plasma marker with high sensitivity in metastatic breast cancer that can be modulated by bisphosphonate treatment.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-02-03.

TGFβ1-Endo180-dependent collagen deposition is dysregulated at the tumour-stromal interface in bone metastasis

Cellular niches in adult tissue can harbour dysregulated microenvironments that become the driving force behind disease progression. The major environmental change when metastatic cells arrive in the bone is the destruction of mineralized type I collagen matrix. Once metastatic niches establish in bone, the invading tumour cells initiate a vicious cycle of osteolytic lesion formation via the dysregulation of paracrine signals and uncoupling of normal bone resorption and production. Here we report that the collagen receptor Endo180 (CD280, MRC2, uPARAP) participates in collagen deposition by primary human osteoblasts during de novo osteoid formation. This newly recognized function of Endo180 was suppressed in osteoblasts following heterotypic direct cell-cell contact in co-culture with prostate tumour cells. Reciprocal Endo180 up-regulation in osteolytic prostate tumour cells (PC3 and DU145) followed their direct contact with osteoblasts and promoted de novo collagen internalization, which is a previously characterized function of the constitutively recycling Endo180 receptor. The osteoblastic suppression and tumour cell-associated enhancement of Endo180 expression were equally sustained in these direct co-cultures. These findings are the first to demonstrate that increased tumour cell participation in collagen degradation and decreased collagen formation by osteoblasts in the osteolytic microenvironment are linked to the divergent regulation of a collagen-binding receptor. Immunohistochemical analysis of core biopsies from bone metastasis revealed higher levels of Endo180 expression in tumour cell foci than cells in the surrounding stroma. Additional experiments in prostate cell-osteoblast co-cultures indicate that divergent regulation of Endo180 is the result of dysregulated TGFβ1 signalling. The findings of this study provide a rationale for targeting collagen remodelling by Endo180 in bone metastases and other collagen matrix pathologies.