RESUMO
N-Butylbenzenesulfonamide (NBBS) is a plasticizer and emerging contaminant that has been detected in a wide array of environmental samples. There are very little toxicity data available with which to evaluate potential risk from exposure to NBBS or other structurally-related sulfonamide plasticizers. To address this knowledge gap, NBBS was selected by the National Toxicology Program for evaluation. The current short-term pre- and post-natal (perinatal) study aims to provide preliminary toxicity and gestational transfer data for NBBS. NBBS was administered via dosed feed at concentrations of 0, 625, 1250, 2500, 5000, and 10,000 ppm to time-mated Sprague Dawley (Hsd:Sprague Dawley SD®) rats from gestation day (GD) 6 through postnatal day (PND) 28. The high concentration of 10,000 ppm NBBS was overtly toxic to dams, and the group was removed on GD 17-18. Exposure to NBBS resulted in lower maternal weights during the gestational period in the 5000 and 10,000 ppm groups as compared to control weights. Dams also displayed lower weights in the lactational period, which resolved to control levels by PND 28. NBBS exposure did not affect pregnancy or littering parameters in F0 dams. However, pup survival was lower in the 5000 ppm group, and pup weights were dose-responsively lower than control pup weights with the difference expanding over the postnatal period. The lowest observed effect level (LOEL) based on significantly lower body weights was 5000 ppm NBBS for F0 dams and 2500 ppm NBBS for F1 pups. Preliminary data for NBBS levels indicated that the chemical was transferred from dams to offspring during the gestational period.
RESUMO
Oncogenic fusion proteins, such as EWS-FLI1, are excellent therapeutic targets as they are only located within the tumor. However, there are currently no agents targeted toward transcription factors, which are often considered to be 'undruggable.' A considerable body of evidence is accruing that refutes this claim based upon the intrinsic disorder of transcription factors. Our previous studies show that RNA Helicase A (RHA) enhances the oncogenesis of EWS-FLI1, a putative intrinsically disordered protein. Interruption of this protein-protein complex by small molecule inhibitors validates this interaction as a unique therapeutic target. Single enantiomer activity from a chiral compound has been recognized as strong evidence for specificity in a small molecule-protein interaction. Our compound, YK-4-279, has a chiral center and can be separated into two enantiomers by chiral HPLC. We show that there is a significant difference in activity between the two enantiomers. (S)-YK-4-279 is able to disrupt binding between EWS-FLI1 and RHA in an immunoprecipitation assay and blocks the transcriptional activity of EWS-FLI1, while (R)-YK-4-279 cannot. Enantiospecific effects are also established in cytotoxicity assays and caspase assays, where up to a log-fold difference is seen between (S)-YK-4-279 and the racemic YK-4-279. Our findings indicate that only one enantiomer of our small molecule is able to specifically target a protein-protein interaction. This work is significant for its identification of a single enantiomer effect upon a protein interaction suggesting that small molecule targeting of intrinsically disordered proteins can be specific. Furthermore, proving YK-4-279 has only one functional enantiomer will be helpful in moving this compound towards clinical trials.