The Role of Checkpoint Kinase 1 in Sensitivity to Topoisomerase I Poisons

Agents that target topoisomerase I are widely utilized to treat human cancer. Previous studies have indicated that both the ataxia telangiectasia mutated (ATM)/ checkpoint kinase (Chk) 2 and ATM- and Rad 3-related (ATR)/Chk1 checkpoint pathways are activated after treatment with these agents. The relative contributions of these two pathways to survival of cells after treatment with topoisomerase I poisons are currently unknown. To address this issue, we assessed the roles of ATR, Chk1, ATM, and Chk2 in cells treated with the topoisomerase I poisons camptothecin and 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan. Colony forming assays demonstrated that down-regulation of ATR or Chk1 sensitized cells to SN-38 and camptothecin. In contrast, ATM and Chk2 had minimal effect of sensitivity to SN-38 or camptothecin. Additional experiments demonstrated that the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin, which down-regulates Chk1, also sensitized a variety of human carcinoma cell lines to SN-38. Collectively, these results show that the ATR/Chk1 pathway plays a predominant role in the response to topoisomerase I inhibitors in carcinoma cells and identify a potential approach for enhancing the efficacy of these drugs

Late onset lens particle glaucoma as a consequence of spontaneous dislocation of an intraocular lens in pseudoexfoliation syndrome

PURPOSE: To report acute onset lens particle glaucoma associated with pseudoexfoliation-related dislocation of an intraocular lens implant 12 years after cataract surgery. METHODS: Case report. RESULTS: An 80-year-old woman presented with acute onset of left eye pain that was associated with white fleck-like particles circulating in the anterior chamber and an intraocular pressure of 48 mm Hg. The posterior chamber intraocular lens within the capsular bag was positioned more posteriorly to the iris plane than usual, and pseudoexfoliative material was present on the lens capsule and the zonules. Anterior chamber aspirate confirmed the presence of lens cortical fibers. CONCLUSION: Spontaneous dislocation of the posterior chamber intraocular lens in patients with pseudoexfoliation syndrome several years after cataract surgery may liberate lens cortical material, causing lens particle glaucoma

Infectious keratitis after LASIK

To report the clinical course, management, and outcomes of culture-proven infectious keratitis in 15 eyes of 13 subjects after LASIK. Retrospective, noncomparative, interventional case series. Fifteen eyes of 13 subjects who underwent LASIK and developed culture-positive keratitis. Infectious keratitis was encountered in the operative eyes between 1 day and 450 days. Cultures were obtained, and topical antibiotic therapy was administered in all cases. Some cases required flap lifting, irrigation, and soaking of the bed with antibiotics, flap amputation, or further surgical intervention. Time periods from onset to diagnosis, from clinical diagnosis to clinical resolution, final acuities, microbiologic profiles, and medical and surgical interventions were reviewed. Onset of symptoms of infection varied, depending on the infectious organism. Bacterial organisms tended to present earlier, whereas mycobacterial and fungal organisms had a later mean onset of presentation. Furthermore, the atypical organisms such as mycobacteria, fungus, and acanthamoeba also had a more delayed diagnosis, resulting in a prolonged disease course. Infectious keratitis after LASIK is a potentially vision-threatening complication. Onset of symptoms varies depending on causative agents. Furthermore, atypical organisms in the interface or beneath the flap can pose both diagnostic and therapeutic dilemmas. Location in the interface can make it more difficult to culture the organisms and prevent adequate penetration of topical antibiotics

Photodynamic Therapy with Verteporfin in a Rabbit Model of Corneal Neovascularization

PURPOSE. To determine the efficacy of photodynamic therapy (PDT) with verteporfin (Visudyne; Novartis AG, Basel, Switzerland) for treatment of corneal neovascularization in a rabbit eye model. METHODS. Corneal neovascularization was induced in Dutch belted rabbits by placing an intrastromal silk suture near the limbus. Verteporfin was administered by intravenous injection at a dose of 1.5 mg/kg, and the pharmacokinetics of verteporfin distribution in the anterior segment or PDT-induced (laser energy levels 17, 50, and 150 J/cm 2 ) regression of corneal blood vessels were then determined. To assess PDT-induced toxicity of the anterior segment, corneal and iris/ciliary body histology, and IOP were evaluated after PDT. RESULTS. Verteporfin accumulation in vascularized regions of the cornea and the iris/ciliary body tissue were time dependent and maximum levels achieved at 60 minutes after injection. In rabbits, PDT of corneal vessels using laser energy of 17 or 50 J/cm 2 resulted in 30% to 50% regression of corneal neovascularization; however, in these animals, a rapid regrowth of new blood vessels occurred between 3 and 5 days. In the rabbits receiving PDT using laser energies of 150 J/cm 2 , the mean vessel regression was 56%. During the nine days of the laser therapy follow-up period, no vessel regrowth was observed in these rabbits. Histologic examination of the anterior segment after PDT (150 J/cm 2 ) showed localized degeneration of the corneal blood vessels without observable change in other anterior segment structures. CONCLUSIONS. These results provide evidence that PDT can produce significant regression of neovascular corneal vessels with no observable toxicity to the anterior segments. However, the optimal laser energy necessary to induce long-term regression (150 J/cm 2 ) was three times that used to treat choroidal neovascularization. (Invest Ophthalmol Vis Sci. 2003;44: 2954 -2958) DOI:10.1167/iovs.02-0572 C orneal neovascularization affects an estimated 1.4 million Americans and is a major cause of blindness worldwide. 1 Several corneal disorders including infections, chemical burns, immunologic diseases, degenerative disorders, and prior trauma can induce corneal neovascularization. In the United States, the most frequently associated etiology is long-time contact lens wear, especially that of soft hydrogel lenses. The primary treatment for actively proliferating corneal vessels is topical corticosteroids. 2 However, in corneas where vessels have been established for an extended period, corticosteroid treatment is often ineffective. Recently, angiogenic inhibitors have also been used to treat corneal neovascularization. 3,4 Photodynamic treatment (PDT) offers another potential treatment for corneal neovascularization. In PDT, systemically administered porphyrin derivatives accumulate in proliferating endothelial cells. Laser energy is then used to activate the porphyrin derivates 2,5-9 liberating cytotoxic oxygen free radicals. The ensuing cytotoxic response results in occlusion of neovascular vessels. Photodynamic treatment using verteporfin (Visudyne; Novartis AG, Basel, Switzerland), a benzoporphyrin derivative monoacid ring A, has been recently approved for the treatment of subfoveal choroidal neovascularization. -12 The purpose of this study was to evaluate the efficacy of the FDA-approved verteporfin formulation and dose and laser treatment for corneal neovascularization. These studies examined the pharmacokinetic characteristics of verteporfin in the anterior segment of rabbit eyes with corneal neovascularization, the PDT-induced toxicity of adjacent ocular structures (e.g., the corneal endothelium and iris/ciliary body), and the optimal laser parameters for treatment of corneal neovascularization. Our results demonstrate that significant amounts of verteporfin can be found in vascularized areas of the cornea as early as 15 minutes after drug injection and that PDT is efficacious in producing and maintaining regression of corneal blood vessels up to 9 days after PDT. However, the optimal laser energy necessary to induce long-term regression (150 J/cm 2 ) was three times that used to treat choroidal neovascularization. MATERIALS AND METHODS Dutch-belted rabbits, weighing 1.5 to 2 kg were maintained in a standard 12-hour light-dark cycle with free access to food and water. Corneal neovascularization was induced using a modified technique described by Schmidt-Erfurth et al. To determine the area of corneal neovascularization, slit-lamp photographs in a standardized magnification were taken on days 1, 4, 7