A Multiplexed Assay That Monitors Effects of Multiple Compound Treatment Times Reveals Candidate Immune-Enhancing Compounds

A phenotypic screen for compounds that reverse cAMP-mediated suppression of T cell functions

The solid tumor microenvironment (TME) suppresses immune responses. Three alterations in the TME converge on a pathway triggered by elevated cyclic AMP (cAMP) that suppresses T cell receptor (TCR) signaling. We developed a phenotypic assay to screen for small molecules that interfere with this pathway using TALL-104 human leukemic cytotoxic T lymphocytes pretreated with prostaglandin E2 to elevate cAMP. Beads coated with anti-CD3 antibodies stimulate lytic granule exocytosis, which is detected via binding of an antibody against lysosome associated membrane protein 1 (LAMP-1) measured with flow cytometry. Confirming that the assay can find compounds with desired activity, treating cells with a phorbol ester restores exocytosis. The assay behaves well in 96-well format and we screened a collection of compounds expected to have effects on epigenetic regulatory proteins. Compounds in this collection affected lytic granule exocytosis after 24-hour treatment, but none prevented cAMP from suppressing lytic granule exocytosis. We used a fully automated 384-well version of the assay to screen the Prestwick Compound Library but obtained no confirmed hits. Analyzing this assay's performance reveals two points of interest. First, cytometry offers multiple ways to quantify signals. Z' was higher using percent positive cells than mean fluorescence because the relationship between the two measures saturates, but using percent positive could make it harder to find hits in some assays. Second, variance was higher in positive controls than in negative controls in this assay, which degrades assay performance less than if variance was higher in negative controls.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

The National Cancer Institute's Plated Compound Sets Can Be a Valuable Resource for Academic Researchers

Academic researchers looking for material to screen may benefit from plated compound collections provided at no cost except shipping by the U.S. National Cancer Institute (NCI). Four plated sets are available, two of which comprise diverse synthetic compounds. These collections, of ~900 and ~1500 compounds, are a convenient size to screen without automated equipment, and a great deal of data about the compounds is available that increases their usefulness. Despite these positive attributes, the collections contain a relatively large number of compounds that are pan-assay interfering and nonspecific (PAINS) or may have other chemical liabilities. Our experience with the compound collections suggests that, perhaps because they contain PAINS and other compounds with liabilities, the collections will yield hits in many assays. This makes them a valuable resource for testing primary screens and follow-up workflows, but by the same token means that hits might not be attractive leads for further development. The NCI sets have a great deal of value for academic researchers as a source of material for early screening. It might be possible, however, to create a better collection specifically for this purpose. One possibility is to pool ~5000-10,000 carefully selected lead-like compounds into ~1000 wells. A collection like this might also generate hits in a wide variety of assays but avoid the downside of those hits often having liabilities.