K16 is a further new candidate for homotypic intermediate filament protein interactions

Emerging Insights into Keratin 16 Expression during Metastatic Progression of Breast Cancer

Simple Summary

The mechanisms leading to tumor metastasis remain poorly understood, and therefore, phenotyping of circulating tumor cells from cancer patients may contribute to translating these mechanisms. In in silico analysis, high expression of keratin 16 was associated with higher tumor aggressiveness. According to our results, keratin 16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility by reorganizing the actin cytoskeleton, which is the driving force behind disrupting intercellular adhesion and directional migration. In metastatic breast cancer patients, circulating tumor cells expressing keratin 16 were associated with shorter relapse-free survival. This is an important issue for future research to determine the exact function of keratin 16 in tumor dissemination and metastasis development by analyzing keratin 16 status in disseminating tumor cells. Furthermore, gaining a better knowledge of keratin 16’s biology would give crucial mechanistic insights that might lead to a unique treatment option.

Abstract

Keratins are the main identification markers of circulating tumor cells (CTCs); however, whether their deregulation is associated with the metastatic process is largely unknown. Previously we have shown by in silico analysis that keratin 16 (KRT16) mRNA upregulation might be associated with more aggressive cancer. Therefore, in this study, we investigated the biological role and the clinical relevance of K16 in metastatic breast cancer. By performing RT-qPCR, western blot, and immunocytochemistry, we investigated the expression patterns of K16 in metastatic breast cancer cell lines and evaluated the clinical relevance of K16 expression in CTCs of 20 metastatic breast cancer patients. High K16 protein expression was associated with an intermediate mesenchymal phenotype. Functional studies showed that K16 has a regulatory effect on EMT and overexpression of K16 significantly enhanced cell motility (p < 0.001). In metastatic breast cancer patients, 64.7% of the detected CTCs expressed K16, which was associated with shorter relapse-free survival (p = 0.0042). Our findings imply that K16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility. Furthermore, determining K16 status in CTCs provides prognostic information that helps to identify patients whose tumors are more prone to metastasize.

Effect of Vitamin D3 on Regulating Human Tenon's Fibroblasts Activity

Purpose

To study the in vitro effect of vitamin D3 on the healing response of human Tenon's fibroblasts (HTF) and its possible role in preventing excessive postoperative subconjunctival fibrosis.

Methods

Effect of vitamin D3 on cytotoxicity and cell survival of primary cultured HTF was measured by lactate dehydrogenase and PrestoBlue assays, respectively. Proliferation and migration of vitamin D3-treated HTF (D3-HTF) was determined by CyQUANT proliferation and scratch assay, respectively. The mRNA expression profiles of control-HTF and D3-HTF from six subjects (three with glaucoma and long-term use of topical medications, three with primary pterygium) were assessed by RNA sequencing analyses to identify potential biomarkers for the inhibitory effect on HTF by vitamin D3. Validation of these biomarkers and their potential pathways were performed by quantitative real-time polymerase chain reaction (qRT-PCR) detection.

Results

Pure monolayers of HTF from controls (retinal detachment or squint surgeries), pterygium, and glaucoma subjects were successfully prepared and passaged. Proliferation and migration of pterygium and glaucoma HTF were inhibited by vitamin D3 in a dose-dependent manner, and without cytotoxicity or decrease in cellular viability with concentrations up to 10 µM. The qRT-PCR results were consistent with the transcriptome analyses, vitamin D3 appears to enhance CYP24A1, SHE, KRT16 but suppresses CILP expression in HTF.

Conclusions

Vitamin D3 can inhibit the in vitro activity of HTF without compromising cellular survivability at concentration up to 10 µM. This has potential clinical application for improving the outcome of pterygium and filtering surgeries.

Translational Relevance

Vitamin D3 can suppress the in vitro proliferation, migration, and transdifferentiation of human Tenon's fibroblasts, without the cytotoxicity of mitomycin-C, the current standard antifibrotic agent in clinical use.

Biodegradation of metallic magnesium elicits an inflammatory response in primary nasal epithelial cells

Resorbable magnesium-based implants hold great promise for various biomedical applications, such as osteosynthesis and coronary stenting. They also offer a new therapeutic option for the treatment of chronic rhinosinusitis, but little data is yet available regarding the use of magnesium in the nasal cavity. To model this field of application, primary porcine nasal epithelial cells were used to test the biocompatibility of degrading pure magnesium and investigate whether the degradation products may also affect cellular metabolism. Magnesium specimens did not induce apoptosis and we found no major influence on enzyme activities or protein synthesis, but cell viability was reduced and elevated interleukin 8 secretion indicated proinflammatory reactions. Necrotic damage was most likely due to osmotic stress, and our results suggest that magnesium ion build-up is also involved in the interleukin 8 release. Furthermore, the latter seems to be mediated, at least in part, by the p38 signaling pathway. These effects probably depended on the accumulation of very high concentrations of magnesium ions in the in vitro set-up, which might not be achieved in vivo, although we cannot exclude that further, as yet unknown, factors played a role in the inflammatory response during the degradation process. In conclusion, the biocompatibility of pure magnesium with cells in the immediate vicinity appears less ideal than is often supposed, and this needs to be considered in the evaluation of magnesium materials containing additional alloying elements.

Differential keratin expression during epiboly in a wound model of bioengineered skin and in human chronic wounds

Epiboly represents the process by which keratinocytes migrate to envelop a surface. The authors have been investigating a living bilayered skin construct (BSC) that is used in the treatment of lower extremity wounds due to venous insufficiency and diabetes. The construct demonstrates epiboly after injury and incubation in vitro, and this model may be useful for studying epidermal migration and the process of skin maturation. Punch biopsies of the construct in vitro were cultured and immunostained for specific keratins at baseline and at 24 to 72 hours. For comparison, skin biopsy specimens from human chronic venous ulcers and acute healing wounds were similarly processed. The authors found that K1 and K10 were fully expressed in the epidermis of the fully epibolized surface on BSC. K1 was also present in the migrating edge of specimens, whereas K10 was not detectable. K16 and K6 were evident in normal skin and the epibolized area of the construct; K6 expression was very prominent in the migrating edge. Importantly, K17 was distinctly limited to the epibolized surface and the migrating edge, and its expression was very similar to that observed in healing human wounds. In conclusion, differential expression of keratins in this epiboly model closely reflects in vivo studies and supports keratin specificity in the processes of migration and differentiation of new epidermis. Therefore, these findings provide further and important validity for the study of epithelialization and the hope of developing prognostic markers for venous ulcer healing.

Inhibition of keratin 17 expression with antisense and RNAi strategies: exploring novel therapy for psoriasis

Psoriasis is now considered to be a chronic, immune-mediated and inflammatory skin disease. As the precise cause of psoriasis remains unknown, its treatment is challenging for dermatologists. Keratin 17 (K17), an intermediate filament protein, is highly expressed in psoriatic lesions, while not normally expressed in healthy epidermis. Studies have suggested that K17 plays a role in the pathogenesis of psoriasis. However, no study has been performed to determine the potential application of K17 down-regulation as a treatment option for psoriatic lesions. We hypothesized that anti-K17 interference may suppress the development and progression of psoriasis and potentially serve as a novel strategy for the treatment of psoriasis. Therefore, we down-regulated and silenced K17 gene expression in keratinocytes (KCs) using antisense and RNA interference (RNAi) techniques. We found that K17-specific antisense oligonucleotides (ASODN) or siRNAs inhibited proliferation and induced apoptosis in KCs as well as down-regulated K17 expression at both mRNA and protein levels. For our in vivo study, we constructed the SCID-hu xenogeneic transplantation psoriasis mouse model by grafting psoriatic lesions onto SCID mice and topically applied K17-specific ASODN and liposome-encapsulated siRNA to the grafts. We observed morphological and histological improvement in the treated psoriatic grafts. As a result, K17 mRNA and protein expression was significantly decreased in the grafts of the mouse model. Taken together, we conclude that anti-K17 therapy is an effective treatment option for psoriasis, and the K17 molecule, as a new target, may hold tremendous potential for the treatment of psoriasis in the future.