Publisher Correction: A cdk1 gradient guides surface contraction waves in oocytes.

A Supplementary Information file from a different paper was inadvertently published with the original version of this Article. This file was replaced with the correct Supplementary Information file on 24 October 2017.

Nivolumab for recurrent cutaneous squamous cell carcinoma: three cases.

Programmed cell death ligand 1 (PD-L1) is frequently expressed in cutaneous squamous cell cancer (CSCC) and preliminary data from an ongoing clinical trial suggest that programmed death receptor 1 (PD-1) checkpoint inhibitors may be useful to treat patients with metastatic non-melanoma skin cancer. To report a series of three patients with advanced CSCC treated with nivolumab, showing that commercially available PD-1 checkpoint inhibitors may be useful in non-melanoma skin cancer patients without access to a clinical trial. All patients had previous chemotherapy. All cancers were PD-1 ligand (PD-L1)-positive based on immunohistochemistry. Patients consented to off-label therapy with nivolumab, which is commercially available in Switzerland. Two patients had a partial tumour response, and have been receiving therapy for more than 12 months. One patient had stable disease after three months, and therapy is also ongoing. So far, no severe adverse effects have occurred. Our cases confirm previous reports demonstrating a clinical effect and tolerability of PD-1 checkpoint inhibitors for heavily pre-treated patients with metastatic CSCC. Commercially available PD-1 checkpoint inhibitors may be useful in these patients who should be considered for PD-1 checkpoint inhibitor therapy, preferentially within clinical trials.

A cdk1 gradient guides surface contraction waves in oocytes.

Surface contraction waves (SCWs) in oocytes and embryos lead to large-scale shape changes coupled to cell cycle transitions and are spatially coordinated with the cell axis. Here, we show that SCWs in the starfish oocyte are generated by a traveling band of myosin II-driven cortical contractility. At the front of the band, contractility is activated by removal of cdk1 inhibition of the RhoA/RhoA kinase/myosin II signaling module, while at the rear, contractility is switched off by negative feedback originating downstream of RhoA kinase. The SCW's directionality and speed are controlled by a spatiotemporal gradient of cdk1-cyclinB. This gradient is formed by the release of cdk1-cyclinB from the asymmetrically located nucleus, and progressive degradation of cyclinB. By combining quantitative imaging, biochemical and mechanical perturbations with mathematical modeling, we demonstrate that the SCWs result from the spatiotemporal integration of two conserved regulatory modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.Surface contraction waves (SCWs) are prominent shape changes coupled to cell cycle transitions in oocytes. Here the authors show that SCWs are patterned by the spatiotemporal integration of two conserved modules, cdk1-cyclinB for cell cycle regulation and RhoA/Rok/NMYII for actomyosin contractility.

Tension and Elasticity Contribute to Fibroblast Cell Shape in Three Dimensions.

The shape of animal cells is an important regulator for many essential processes such as cell migration or division. It is strongly determined by the organization of the actin cytoskeleton, which is also the main regulator of cell forces. Quantitative analysis of cell shape helps to reveal the physical processes underlying cell shape and forces, but it is notoriously difficult to conduct it in three dimensions. Here we use direct laser writing to create 3D open scaffolds for adhesion of connective tissue cells through well-defined adhesion platforms. Due to actomyosin contractility in the cell contour, characteristic invaginations lined by actin bundles form between adjacent adhesion sites. Using quantitative image processing and mathematical modeling, we demonstrate that the resulting shapes are determined not only by contractility, but also by elastic stress in the peripheral actin bundles. In this way, cells can generate higher forces than through contractility alone.

Optogenetic control of RhoA reveals zyxin-mediated elasticity of stress fibres.

Cytoskeletal mechanics regulates cell morphodynamics and many physiological processes. While contractility is known to be largely RhoA-dependent, the process by which localized biochemical signals are translated into cell-level responses is poorly understood. Here we combine optogenetic control of RhoA, live-cell imaging and traction force microscopy to investigate the dynamics of actomyosin-based force generation. Local activation of RhoA not only stimulates local recruitment of actin and myosin but also increased traction forces that rapidly propagate across the cell via stress fibres and drive increased actin flow. Surprisingly, this flow reverses direction when local RhoA activation stops. We identify zyxin as a regulator of stress fibre mechanics, as stress fibres are fluid-like without flow reversal in its absence. Using a physical model, we demonstrate that stress fibres behave elastic-like, even at timescales exceeding turnover of constituent proteins. Such molecular control of actin mechanics likely plays critical roles in regulating morphodynamic events.

Geometry and network connectivity govern the mechanics of stress fibers.

Actomyosin stress fibers (SFs) play key roles in driving polarized motility and generating traction forces, yet little is known about how tension borne by an individual SF is governed by SF geometry and its connectivity to other cytoskeletal elements. We now address this question by combining single-cell micropatterning with subcellular laser ablation to probe the mechanics of single, geometrically defined SFs. The retraction length of geometrically isolated SFs after cutting depends strongly on SF length, demonstrating that longer SFs dissipate more energy upon incision. Furthermore, when cell geometry and adhesive spacing are fixed, cell-to-cell heterogeneities in SF dissipated elastic energy can be predicted from varying degrees of physical integration with the surrounding network. We apply genetic, pharmacological, and computational approaches to demonstrate a causal and quantitative relationship between SF connectivity and mechanics for patterned cells and show that similar relationships hold for nonpatterned cells allowed to form cell-cell contacts in monolayer culture. Remarkably, dissipation of a single SF within a monolayer induces cytoskeletal rearrangements in cells long distances away. Finally, stimulation of cell migration leads to characteristic changes in network connectivity that promote SF bundling at the cell rear. Our findings demonstrate that SFs influence and are influenced by the networks in which they reside. Such higher order network interactions contribute in unexpected ways to cell mechanics and motility.

Model-based traction force microscopy reveals differential tension in cellular actin bundles.

Adherent cells use forces at the cell-substrate interface to sense and respond to the physical properties of their environment. These cell forces can be measured with traction force microscopy which inverts the equations of elasticity theory to calculate them from the deformations of soft polymer substrates. We introduce a new type of traction force microscopy that in contrast to traditional methods uses additional image data for cytoskeleton and adhesion structures and a biophysical model to improve the robustness of the inverse procedure and abolishes the need for regularization. We use this method to demonstrate that ventral stress fibers of U2OS-cells are typically under higher mechanical tension than dorsal stress fibers or transverse arcs.

Swiss clinical practice guidelines on field cancerization of the skin.

Actinic keratosis (AK) affects millions of people worldwide, and its prevalence continues to increase. AK lesions are caused by chronic ultraviolet radiation exposure, and the presence of two or more AK lesions along with photodamage should raise the consideration of a diagnosis of field cancerization. Effective treatment of individual lesions as well as field cancerization is essential for good long-term outcomes. The Swiss Registry of Actinic Keratosis Treatment (REAKT) Working Group has developed clinical practice guidelines for the treatment of field cancerization in patients who present with AK. These guidelines are intended to serve as a resource for physicians as to the most appropriate treatment and management of AK and field cancerization based on current evidence and the combined practical experience of the authors. Treatment of AK and field cancerization should be driven by consideration of relevant patient, disease, and treatment factors, and appropriate treatment decisions will differ from patient to patient. Prevention measures and screening recommendations are discussed, and special considerations related to management of immunocompromised patients are provided.

Internet based health promotion campaign against skin cancer - Results of www.skincheck.ch in Switzerland.

Conventional skin cancer prevention programs appeal to limited populations, and the middle aged male population responds less frequently. Our objective was to establish a complementary health promotion campaign tool for skin cancer prevention. Internet-based education, instruction for self assessment and teledermatological evaluation of skin lesions by an expert commission of dermatologists was used. Compliance and clinical diagnosis was assessed in a subgroup. 12,000 users visited the educational website. There was strong interest among the middle aged male population (53% (N = 262): male; mean age: 42). 28.5% of examined lesions (N = 494) were considered suspicious. Email requests, sent to the group whose lesions where considered suspicious, were answered by 46.0% of females (N = 29) and 59.7% of males (N = 46) with a female distribution predominantly in younger ages (52.6% of females with known age: < 30 years). Males were predominantly represented over 30 years (86.2% of all males). According to user's declarations, at least 8 (8.5%) malignant lesions (1 melanoma in situ, 1 squamous cell carcinoma, 4 basal cell carcinomas, 2 malignant lesions without declared diagnosis) were finally diagnosed by physicians. We conclude that internet-based, interactive, educational programs, in addition to existing health promotion campaigns, can enhance public participation in the middle aged male population in skin cancer prevention.