Mechanotransduction pathways promoting tumor progression are activated in invasive human squamous cell carcinoma.

Cutaneous squamous cell carcinomas (SCCs) are commonly diagnosed skin cancers that may progress to invasiveness in the absence of early intervention. Using a murine model of SCC, we have previously demonstrated that activation of the Rho-associated kinase (ROCK) signaling pathway promotes rapid progression of pre-neoplastic lesions to invasive SCC. Herein we demonstrate that in human cutaneous SCC, ROCK signaling is increasingly up-regulated with tumor progression in both tumor cells and cells of the tumor microenvironment and is accompanied by key tumor-promoting changes in the extracellular matrix protein composition. The mechanotransduction pathway mediated by integrin signaling through FAK, GSK3ß, and the transcription coactivator ß-catenin is also progressively activated in human cutaneous SCC. Our observations indicate that ROCK activation is a tumor promoter in human cutaneous SCC and acts via mechanotransduction of signals to ß-catenin. Our experiments raise the possibility that inhibition of ROCK signaling could be a useful therapeutic approach to halt cutaneous SCC progression by reducing the signal flux through this pathway to physiologic levels, thereby normalizing the extracellular matrix composition.

Macrophage presence is essential for the regeneration of ascending afferent fibres following a conditioning sciatic nerve lesion in adult rats.

BACKGROUND: Injury to the peripheral branch of dorsal root ganglia (DRG) neurons prior to injury to the central nervous system (CNS) DRG branch results in the regeneration of the central branch. The exact mechanism mediating this regenerative trigger is not fully understood. It has been proposed that following peripheral injury, the intraganglionic inflammatory response by macrophage cells plays an important role in the pre-conditioning of injured CNS neurons to regenerate. In this study, we investigated whether the presence of macrophage cells is crucial for this type of regeneration to occur. We used a clodronate liposome technique to selectively and temporarily deplete these cells during the conditioning phase of DRG neurons. RESULTS: Retrograde and anterograde tracing results indicated that in macrophage-depleted animals, the regenerative trigger characteristic of pre-conditioned DRG neurons was abolished as compared to injury matched-control animals. In addition, depletion of macrophage cells led to: (i) a reduction in macrophage infiltration into the CNS compartment even after cellular repopulation, (ii) astrocyte up-regulation at rostral regions and down-regulation in brain derived neurotrophic factor (BDNF) concentration in the serum. CONCLUSION: Activation of macrophage cells in response to the peripheral nerve injury is essential for the enhanced regeneration of ascending sensory neurons.

A Negative Regulatory Mechanism Involving 14-3-3ζ Limits Signaling Downstream of ROCK to Regulate Tissue Stiffness in Epidermal Homeostasis.

ROCK signaling causes epidermal hyper-proliferation by increasing ECM production, elevating dermal stiffness, and enhancing Fak-mediated mechano-transduction signaling. Elevated dermal stiffness in turn causes ROCK activation, establishing mechano-reciprocity, a positive feedback loop that can promote tumors. We have identified a negative feedback mechanism that limits excessive ROCK signaling during wound healing and is lost in squamous cell carcinomas (SCCs). Signal flux through ROCK was selectively tuned down by increased levels of 14-3-3ζ, which interacted with Mypt1, a ROCK signaling antagonist. In 14-3-3ζ(-/-) mice, unrestrained ROCK signaling at wound margins elevated ECM production and reduced ECM remodeling, increasing dermal stiffness and causing rapid wound healing. Conversely, 14-3-3ζ deficiency enhanced cutaneous SCC size. Significantly, inhibiting 14-3-3ζ with a novel pharmacological agent accelerated wound healing 2-fold. Patient samples of chronic non-healing wounds overexpressed 14-3-3ζ, while cutaneous SCCs had reduced 14-3-3ζ. These results reveal a novel 14-3-3ζ-dependent mechanism that negatively regulates mechano-reciprocity, suggesting new therapeutic opportunities.

Sciatic nerve conditioning lesion increases macrophage response but it does not promote the regeneration of injured optic nerves.

UNLABELLED: Injured optic nerves in the matured central nervous system (CNS), alike injured neurons in other CNS regions, fail to regenerate. Interestingly, activation of inflammatory cells (macrophages) following optic lens injury or implantation of peripheral nerve fragments into the vitreous body, have been previously reported to stimulate retinal ganglion cells (RGCs) to regenerate axons across the injury site and into the distal optic nerve. In addition, the beneficial role of macrophage cells has also been demonstrated in the regeneration of lesioned spinal neurons following sciatic nerve injury. However, it is not known whether these locally activated macrophage cells also contribute to the regeneration of remotely injured neurons within the CNS. Adult Sprague Dawley rats received a conditioning sciatic nerve injury followed by an optic nerve crush (ONC). Retrograde and anterograde tracing results revealed that injured optic axons did not regenerate after peripheral dorsal root ganglion (DRG) lesion, as the beneficial effects of this injury extended only locally. However, a greater inflammatory infiltration/activation was found in injury-combined animals compared to controls, although this was not sufficient to trigger a systemic regenerative response. Proximity of cell body response to injury, accompanied by a timely macrophage activation are critical factors for regeneration of injured CNS neurons to occur. Immune cell surveillance into the CNS compartment was enhanced following peripheral nerve injury. SCOPE: nervous system development, regeneration and aging.