The HSP90 Inhibitor NVP-AUY922 Radiosensitizes by Abrogation of Homologous Recombination Resulting in Mitotic Entry with Unresolved DNA Damage

Heat shock protein 90 (HSP90) is a molecular chaperone responsible for the conformational maintenance of a number of client proteins that play key roles in cell cycle arrest, DNA damage repair and apoptosis following radiation. HSP90 inhibitors exhibit antitumor activity by modulating the stabilisation and activation of HSP90 client proteins. We sought to evaluate NVP-AUY922, the most potent HSP90 inhibitor yet reported, in preclinical radiosensitization studies.NVP-AUY922 potently radiosensitized cells in vitro at low nanomolar concentrations with a concurrent depletion of radioresistance-linked client proteins. Radiosensitization by NVP-AUY922 was verified for the first time in vivo in a human head and neck squamous cell carcinoma xenograft model in athymic mice, as measured by delayed tumor growth and increased surrogate end-point survival (p = <0.0001). NVP-AUY922 was shown to ubiquitously inhibit resolution of dsDNA damage repair correlating to delayed Rad51 foci formation in all cell lines tested. Additionally, NVP-AUY922 induced a stalled mitotic phenotype, in a cell line-dependent manner, in HeLa and HN5 cell lines irrespective of radiation exposure. Cell cycle analysis indicated that NVP-AUY922 induced aberrant mitotic entry in all cell lines tested in the presence of radiation-induced DNA damage due to ubiquitous CHK1 depletion, but resultant downstream cell cycle effects were cell line dependent.These results identify NVP-AUY922 as the most potent HSP90-mediated radiosensitizer yet reported in vitro, and for the first time validate it in a clinically relevant in vivo model. Mechanistic analysis at clinically achievable concentrations demonstrated that radiosensitization is mediated by the combinatorial inhibition of cell growth and survival pathways, ubiquitous delay in Rad51-mediated homologous recombination and CHK1-mediated G(2)/M arrest, but that the contribution of cell cycle perturbation to radiosensitization may be cell line specific

Customized corneal cross-linking

3nononePersonalized accelerated crosslinking nomograms for the management of corneal ectasia were conceived after comparative analysis of demarcation lines and cell viability observed after customized accelerated epithelium-off crosslinking CXL treatments by spectral domain corneal OCT and scanning laser in vivo confocal microscopy matching all the clinical and instrumental data with mathematical models. Accelerated high-fluence Topography-guided CXL at 30 mW/cm2 UV-Power and Accelerated epithelium-off CXL with 9 and 15 mW/cm2 UV-A power with standardized Fluence of 5.4 J/cm2 were safe and effective demostrating a keratocytes apoptosis and demarcation line depth between 280 and 340 μm. The 30 mW ACXL showed a penetration with continuous and pulsed light between 150 and 200 μm. No endothelial damage was reported in any case. In vivo morphological studies demonstrated that Accelerated CXL allow a pachymetry-guided cutomization of CXL maintainig the standard Fluence of 5.4 J/cm2 and a total treatment time under 20 min. Moreover a pachymetry-guided ACXL nomogram (M nomogram) developed by Mazzotta C and Friedman M matching the physical and mathematical calculations with the miscostructural IVCM and OCT observations of demarcation lines depths allow an efficacous CXL management of primary and iatrogenic ectatic corneas also allowing a safe management of thin ectatic corneas.noneMazzotta C.; Rechichi M.; Ferrise M.Mazzotta, C.; Rechichi, M.; Ferrise, M