Comparison of high throughput screening technologies for luminescence cell-based reporter screens.

As higher density formats become more and more common in HTS labs, the expectations for maintaining faster, lower cost screens puts great pressure on traditional 96-well screens. In some cases higher density formats are not compatible with the assay. This seems especially true in cell-based assays. In our case, the nature of the cells' response forced us to remain in 96-well plates. In this paper, we describe the development of a luminescence reporter assay and its performance in two detection modes, flash and glow. The advantages in cost and throughput for each technique are explored, along with automation considerations. An additional new technology, the use of pins for low-volume transfers, is also briefly described because of its dramatic effect on our screen's throughput. However, it will be more thoroughly presented in a future publication. Comparing the technologies available for HTS aids in designing automated systems that meet the unique needs of each assay.

Development and use of a high-throughput bacterial DNA gyrase assay to identify mammalian topoisomerase II inhibitors with whole-cell anticancer activity.

A high-throughput screen (HTS) was developed and used to identify inhibitors of bacterial DNA gyrase. Among the validated hits were 53 compounds that also inhibited mammalian topoisomerase II with IC(50) values of <12.5 micro g/mL for 51 of them. Using computational methods, these compounds were subjected to cluster analysis to categorize them according to their chemical and structural properties. Nine compounds from different clusters were tested for their whole-cell inhibitory activity against 3 cancer cell lines-NCI-H460 (lung), MCF7 (breast), and SF-268 (CNS)-at a concentration of 100 micro M. Five compounds inhibited cell growth by >50% for all 3 cell lines tested. These compounds were tested further against a panel of 53 to 57 cell lines representing leukemia, melanoma, colon, CNS, ovarian, renal, prostate, breast, and non-small cell lung cancers. In this assay, PGE-7143417 was found to be the most potent compound, which inhibited the growth of all the cell lines by 50% at a concentration range of 0.31 to 2.58 micro M, with an average of 1.21 micro M. An additional 17 compounds were also tested separately against a panel of 10 cell lines representing melanoma, colon, lung, mammary, ovarian, prostate, and renal cancers. In this assay, 4 compounds-PGE-3782569, PGE-7411516, PGE-2908955, and PGE-3521917-were found to have activity with concentrations for 50% cell growth inhibition in the 0.59 to 3.33, 22.5 to 59.1, 7.1 to >100, and 24.7 to >100 micro M range.

The effect of room-temperature storage on the stability of compounds in DMSO.

The stability of approximately 7200 compounds stored as 20-mM DMSO solutions under ambient conditions was monitored for 1 year. Compound integrity was measured by flow injection analysis using positive and negative electrospray ionization mass spectrometry. Each sample was assessed at the beginning of the study, after 12 months of storage, and at a randomized time point between the initial and final time points of the study. The relationship between length of storage and the probability of observing the compound was described by a repeated-measures logistic regression model. The probability of observing the compound was 92% after 3 months of storage at room temperature, 83% after 6 months, and 52% after 1 year in DMSO. An acceptable limit for compound loss and corresponding maximum storage time for samples in DMSO can be determined based on these results.

The effect of freeze/thaw cycles on the stability of compounds in DMSO.

A diverse set of 320 compounds from the Procter & Gamble Pharmaceuticals organic compound repository was prepared as 20-mM DMSO solutions and stored at 4 degrees C under argon in pressurized canisters to simulate a low-humidity environment. The plates were subjected to 25 freeze/thaw cycles while being exposed to ambient atmospheric conditions after each thaw to simulate the time and manner by which compound plates are exposed to the atmosphere during typical liquid-handling and high-throughput screening processes. High-performance liquid chromatography-mass spectrometry with evaporative light-scattering detection was used to quantitate the amount of compound remaining after every 5th freeze/thaw cycle. Control plates were stored either at room temperature under argon or at 4 degrees C under argon without freeze/thaw cycling and were evaluated at the midpoint and the endpoint of the study. The study was conducted over a short time period (i.e., 7 weeks) to minimize the effect of compound degradation over time due to the exposure of the compounds to DMSO. The results from this study will be used to determine the maximum number of freeze/thaw cycles that can be achieved while maintaining acceptable compound integrity.