Rate of CRL4(CRBN) substrate Ikaros and Aiolos degradation underlies differential activity of lenalidomide and pomalidomide in multiple myeloma cells by regulation of c-Myc and IRF4.

Recent discoveries suggest that the critical events leading to the anti-proliferative activity of the IMiD immunomodulatory agents lenalidomide and pomalidomide in multiple myeloma (MM) cells are initiated by Cereblon-dependent ubiquitination and proteasomal degradation of substrate proteins Ikaros (IKZF1) and Aiolos (IKZF3). By performing kinetic analyses, we found that the downregulation or proteasomal degradation of Ikaros and Aiolos led to specific and sequential downregulation of c-Myc followed by IRF4 and subsequent growth inhibition and apoptosis. Notably, to ensure growth inhibition and cell death, sustained downregulation of Ikaros and Aiolos, c-Myc or IRF4 expression was required. In addition, we found that the half-maximal rate, rather than the final extent of Ikaros and Aiolos degradation, correlated to the relative efficacy of growth inhibition by lenalidomide or pomalidomide. Finally, we observed that all four transcription factors were elevated in primary MM samples compared with normal plasma cells. Taken together, our results suggest a functional link between Ikaros and Aiolos, and the pathological dysregulation of c-Myc and IRF4, and provide a new mechanistic understanding of the relative efficacy of lenalidomide and pomalidomide based on the kinetics of substrate degradation and downregulation of their downstream targets.

Experimental studies on synergism between aminoglycosides and the antimicrobial antiinflammatory agent diclofenac sodium.

The antiinflammatory agent diclofenac sodium (Dc) exhibited remarkable antibacterial effects both in vitro and in vivo. Fifteen different bacteria sensitive to Dc as well as to a number of common antibiotics were tested for synergistic effects in vitro. Disc diffusion test with Dc and aminoglycosides assessed by stringent computation showed clear-cut synergism. Synergism between Dc and streptomycin (Sm) was found to be statistically significant (p < or = 0.01) when compared with their individual effects. By the checkerboard assessment procedure, the fractional inhibitory concentration (FIC) index of this combination was found to be 0.49, confirming synergism. The mouse protective capacity of this combination was then evaluated in vivo against S. typhimurium as the virulent infecting bacterium, and the size of bacterial load determined from infected autopsied animals. Statistical analysis by Student's 't' test suggested this drug combination is highly synergistic; synergism was also noted between Dc and other aminoglycosides.

A new powerful antibacterial synergistic combination of trimethoprim and trimeprazine.

The antihistaminic phenothiazine trimeprazine (Tz) was found to exhibit significant antibacterial activity on the basis of in vitro and in vivo tests. For the study of synergism due to a combination between Tz and trimethoprim (Tm), drug soaked filter paper discs were placed on young culture lawns of sensitive bacteria on nutrient agar plates. Calculation of the area of inhibition zones for determining the degree of synergism between Tz and Tm showed the increase to be statistically significant (p<0.01) when compared with their individual effects. By the checkerboard assessment procedure, the fractional inhibitory concentration (FIC) index was found to be 0.18, confirming synergism. The protective capacity of this combination was then assessed in Swiss white mice using S. typhimurium as the challenge bacterium, and the level of bacterial load was determined from infected autopsied animals. Statistical analysis of the data by students 't' test finally proved that a combination of Tz+Tm was highly synergistic.