PARP-1 is a critical enzyme in the repair of DNA strand breaks. Inhibition of PARP-1 increases the effectiveness of radiation in killing tumor cells. However, although the mechanism(s) are well understood for these radiosensitizing effects in vitro, the underlying mechanism(s) in vivo are less clear. Nicotinamide, a drug structurally related to the first generation PARP-1 inhibitor, 3-aminobenzamide, reduces tumor hypoxia by preventing transient cessations in tumor blood flow, thus improving tumor oxygenation and sensitivity to radiotherapy. Here, we investigate whether olaparib, a potent PARP-1 inhibitor, enhances radiotherapy, not only by inhibiting DNA repair but also by changing tumor vascular hemodynamics in non-small cell lung carcinoma (NSCLC). In irradiated Calu-6 and A549 cells, olaparib enhanced the cytotoxic effects of radiation (sensitizer enhancement ratio at 10% survival ¼ 1.5 and 1.3) and DNA double-strand breaks persisted for at least 24 hours after treatment. Combination treatment of Calu-6 xenografts with olaparib and fractionated radiotherapy caused significant tumor regression (P ¼ 0.007) relative to radiotherapy alone. To determine whether this radiosensitization was solely due to effects on DNA repair, we used a dorsal window chamber model to establish the drug/radiation effects on vessel dynamics. Olaparib alone, when given as single or multiple daily doses, or in combination with fractionated radiotherapy, increased the perfusion of tumor blood vessels. Furthermore, an ex vivo assay in phenylephrine preconstricted arteries confirmed olaparib to have higher vasodilatory properties than nicotinamide. This study suggests that olaparib warrants consideration for further development in combination with radiotherapy in clinical oncology settings such as NSCLC. Mol Cancer Ther; 10(10); 1949-58. Ó2011 AACR.

A series of laboratory studies were undertaken to investigate the survival of salmonid alphaviruses (SAV) under a range of conditions relevant to waste disposal, persistence and spread in the field, and to laboratory studies and testing. SAV was found to be rapidly inactivated in the presence of high levels of organic matter at 60 degrees C at pH 7.2 and at pH 4 and pH 12 at 4 degrees C, suggesting that composting, ensiling and alkaline hydrolysis would all be effective at inactivating virus in fish waste. Testing was conducted under sterile conditions at 4, 10, 15 and 20 degrees C in sea water, half-strength sea water and fresh (hard) water, both in the absence and the presence of added organic matter. Virus survival was shown to be inversely related to temperature, and to be reduced by the presence of organic matter. Calculated half lives (t(1/2)) under these conditions ranged from 61.0 to 1.5 days. Testing in non-sterile sea water resulted in reduced t(1/2) values. The half life of SAV in serum was also found to be inversely related to temperature, emphasizing the need for rapid shipment of samples at 4 degrees C to laboratories for virus isolation studies.

A range of commercially available disinfectants were tested for efficacy against salmonid alphavirus under a range of different conditions including variations in concentration, temperature, contact time, water type and presence or absence of organic matter. Testing was based on the protocol defined in the draft European Standard prEN 14675, for which the effective standard is a 4 log(10) reduction in viral titre. All disinfectants were found to be effective under at least some of the conditions tested. However, the presence of organic matter in particular was shown to be detrimental in some cases, either through rendering some disinfectants ineffective, or by production of a visible inhomogeneity.

Therapeutic inhibition of poly(ADP-ribose) polymerase (PARP), as monotherapy or to supplement the potencies of other agents, is a promising strategy in cancer treatment. We previously reported that the first PARP inhibitor to enter clinical trial, rucaparib (AG014699), induced vasodilation in vivo in xenografts, potentiating response to temozolomide. We now report that rucaparib inhibits the activity of the muscle contraction mediator myosin light chain kinase (MLCK) 10-fold more potently than its commercially available inhibitor ML-9. Moreover, rucaparib produces additive relaxation above the maximal degree achievable with ML-9, suggesting that MLCK inhibition is not solely responsible for dilation. Inhibition of nitric oxide synthesis using L-NMMA also failed to impact rucaparib’s activity. Rucaparib contains the nicotinamide pharmacophore, suggesting it may inhibit other NAD+-dependent processes. NAD+ exerts P2 purinergic receptor-dependent inhibition of smooth muscle contraction. Indiscriminate blockade of the P2 purinergic receptors with suramin abrogated rucaparib-induced vasodilation in rat arterial tissue without affecting ML-9-evoked dilation, although the specific receptor subtypes responsible have not been unequivocally identified. Furthermore, dorsal window chamber and real time tumor vessel perfusion analyses in PARP-1-/- mice indicate a potential role for PARP in dilation of tumor-recruited vessels. Finally, rucaparib provoked relaxation in 70% of patient-derived tumor-associated vessels. These data provide tantalising evidence of the complexity of the mechanism underlying rucaparib-mediated vasodilation.