The DLD 1 4Ub bcr-abl Luc assay was used to a higher throughput screening system. Initially, over 30,000 compounds from plant extract selections and chemical libraries were screened, which led to several strikes amongst which physalin T was identified from a methanol extract of P. angulata aerial parts. The game of physalin B was then confirmed using the low automated assay. As illustrated in B, physalin W caused a and time dependent increase in bioluminescence from DLD 1 4Ub Luc cells, reflecting its influence of stabilization of the 4Ub Luc reporter protein in these cells and therefore the inhibition of 4Ub Luc degradation by the proteasome. A substantial upsurge in bioluminescence was already observed after 6 h, with an Induction Factor of 17fold at 5 mM. The maximal action was obtained at 5 mM and Ivacaftor structure after 16 h with a 33 fold upsurge in bioluminescence. The increase in bioluminescence was less essential at 10 mM, which might derive from a cytotoxic effect. Consistently with physalin W induced escalation in bioluminescence, ubiquitinated proteins were accumulated in DLD 1 4Ub Luc cells treated with physalin B in a period and concentrationdependent manner. A high degree of protein deposition was seen at 5 mM from 8 h and remained high until 48 h. More especially, treatment of DLD 1 4Ub Luc cells with 5 mM physalin T for 16 h induced accumulation of the cdk inhibitor p27, among the well-known substrate of ubiquitin proteasome pathway. Such effects were in keeping with the scientific effects judged as representative of proteasome inhibition. More over, to exclude the possibility that physalin B induced inhibition of ubiquitin proteasome pathway was due to a low level of ATP in DLD 1 4Ub cells, we assessed the results of physalin T on the level of ATP, at times where inhibition of the ubiquitinproteasome pathway was mentioned. Papillary thyroid cancer Using an ATPlite equipment analysis, in line with the measurement of ATP produced from viable cells, we observed that physalin T at 5 mM for 6, 8 or 16 h did fatty acid amide hydrolase inhibitors not alter the level of ATP in DLD 1 4Ub cells. This suggests therefore that the inhibition of the degradation of 4Ub Luc writer protein and ubiquitinated proteins induced by physalin W after 6 16 h can’t be due to a loss of ATP. Its consequences on the chymotrypsin like, trypsin like and caspase like activities of the filtered proteasome were analyzed, then to find out whether physalin T inhibits ubiquitin proteasome pathway through inhibition of catalytic activities of proteasome. Physalin B at levels around 100 mM did not interfere with these enzymatic activities. On the other hand, bortezomib, epoxomicin or clastolactacystin inhibited chymotrypsinlike activity with IC50 values of 0. 02 mM, 0. 09 mM, and 0. 33 mM, respectively.