Mouse models of nonmelanoma skin cancer

Oncogenic Kras induces spatiotemporally specific tissue deformation through converting pulsatile into sustained ERK activation

Tissue regeneration and maintenance rely on coordinated stem cell behaviours. This orchestration can be impaired by oncogenic mutations leading to cancer. However, it is largely unclear how oncogenes perturb stem cells' orchestration to disrupt tissue. Here we used intravital imaging to investigate the mechanisms by which oncogenic Kras mutation causes tissue disruption in the hair follicle. Through longitudinally tracking hair follicles in live mice, we found that KrasG12D, a mutation that can lead to squamous cell carcinoma, induces epithelial tissue deformation in a spatiotemporally specific manner, linked with abnormal cell division and migration. Using a reporter mouse capture real-time ERK signal dynamics at the single-cell level, we discovered that KrasG12D, but not a closely related mutation HrasG12V, converts ERK signal in stem cells from pulsatile to sustained. Finally, we demonstrated that interrupting sustained ERK signal reverts KrasG12D-induced tissue deformation through modulating specific features of cell migration and division.

Multi-Tissue Characterization of GILZ Expression in Dendritic Cell Subsets at Steady State and in Inflammatory Contexts

Dendritic cells (DCs) are key players in the control of tolerance and immunity. Glucocorticoids (GCs) are known to regulate DC function by promoting their tolerogenic differentiation through the induction of inhibitory ligands, cytokines, and enzymes. The GC-induced effects in DCs were shown to critically depend on increased expression of the Glucocorticoid-Induced Leucine Zipper protein (GILZ). GILZ expression levels were further shown to control antigen-presenting cell function, as well as T-cell priming capacity of DCs. However, the pattern of GILZ expression in DC subsets across tissues remains poorly described, as well as the modulation of its expression levels in different pathological settings. To fill in this knowledge gap, we conducted an exhaustive analysis of GILZ relative expression levels in DC subsets from various tissues using multiparametric flow cytometry. This study was performed at steady state, in the context of acute as well as chronic skin inflammation, and in a model of cancer. Our results show the heterogeneity of GILZ expression among DC subsets as well as the complexity of its modulation, that varies in a cell subset- and context-specific manner. Considering the contribution of GILZ in the control of DC functions and its potential as an immune checkpoint in cancer settings, these results are of high relevance for optimal GILZ targeting in therapeutic strategies.

A genome-wide library of MADM mice for single-cell genetic mosaic analysis

Mosaic analysis with double markers (MADM) offers one approach to visualize and concomitantly manipulate genetically defined cells in mice with single-cell resolution. MADM applications include the analysis of lineage, single-cell morphology and physiology, genomic imprinting phenotypes, and dissection of cell-autonomous gene functions in vivo in health and disease. Yet, MADM can only be applied to <25% of all mouse genes on select chromosomes to date. To overcome this limitation, we generate transgenic mice with knocked-in MADM cassettes near the centromeres of all 19 autosomes and validate their use across organs. With this resource, >96% of the entire mouse genome can now be subjected to single-cell genetic mosaic analysis. Beyond a proof of principle, we apply our MADM library to systematically trace sister chromatid segregation in distinct mitotic cell lineages. We find striking chromosome-specific biases in segregation patterns, reflecting a putative mechanism for the asymmetric segregation of genetic determinants in somatic stem cell division.

Non-invasive targeted iontophoretic delivery of cetuximab to skin

Background: Cetuximab (CTX) is a glycosylated anti-EGFR monoclonal antibody of great interest in the treatment of non-melanoma skin cancers. Its intravenous administration is associated with severe side effects. This is the first report on the noninvasive iontophoretic-targeted topical delivery of CTX to skin.Methods: Iontophoretic transport of CTX (0.5 mA/cm²) was studied as a function of formulation pH (4, 5.5 and 7) and duration of current application (2, 4 and 8 h). CTX cutaneous biodistribution was determined; electrotransport mechanisms and penetration pathways were investigated.Results: Electrophoretic mobility measurements of CTX isoforms and co-iontophoresis of acetaminophen at each pH demonstrated that CTX electrotransport was due to electroosmosis: despite an ~8-fold reduction in charge, CTX skin deposition was greater at pH 7 than pH 4 (8.974 ± 1.952 and 0.482 ± 0.165 μg/mm³) - consistent with the increased electroosmotic flow at pH 7. Iontophoresis of an Alex488-CTX conjugate showed that skin penetration occurred by the intercellular and follicular routes. Therapeutic concentrations of CTX in the viable epidermis, upper dermis and lower dermis were achieved following iontophoresis for 2, 4 and 8 h, respectively.Conclusion: The results demonstrate the topical delivery of a 152 kDa monoclonal antibody into skin in a targeted, controlled and entirely noninvasive manner.

Novel Lipidized Derivatives of the Bioflavonoid Hesperidin: Dermatological, Cosmetic and Chemopreventive Applications

Hesperidin is one of the most important natural flavonoids, known for its antioxidant, anti-inflammatory, anti-mutagenic, and anti-hypertensive properties. Despite its various biological activities, hesperidin is rarely used in the dermo-cosmetic field because of its poor solubility in both water and oil phases that makes difficult formulation, distribution and bioavailability through the skin layers. Moreover, hesperidin is still underestimated in skin care products, and literature data on its stability into a topical formulation are not yet available. In this paper we report the synthesis of five different derivatives of hesperidin and their evaluation in terms of antioxidant, antifungal, antiproliferative, and apoptotic effects on human leukemic K562 cells. Preliminary antiproliferative effects were considered since hyper-proliferation is involved in several cutaneous problems particularly in the case of photo-exposition and environmental pollution. Esp4 and Esp5 were found to be more active in inhibiting K562 cell growth than parent hesperidin. Esp3 exhibited different biological properties, i.e., antioxidant activity in the absence of antiproliferative effects.

Basal Cell Carcinoma Arises from Interfollicular Layer of Epidermis

Background

BCC is currently the most common type of skin cancer in humans. Although having a low-grade malignancy and metastatic potential, BCC is locally aggressive and destructive. Despite numerous studies, the origin of BCC, whether arising from the follicular or interfollicular layer, remains controversial.

Objectives

This study aims to evaluate whether BCC arises from the follicular or interfollicular layer by using immunohistochemical staining.

Methods

Twenty-three specimens of superficial and nodular BCC at its very early stage were examined. The samples were immunohistochemically stained using BerEP4 antibody. The stained specimens were then examined and scored by 2 independent observers.

Results

BerEP4 was found to be strongly positive in all BCC lesions, including a very early lesions budding off the basal layer of the epidermis.

Conclusion

This study confirmed that the origin site of BCC is basal layer of epidermis. This finding suggests that BCC arises from the interfollicular epidermis.