Caspases groups

The group at Pharmacyclics developed a related phenyl hydroxamic add HDACi, PCI-34051 (27e) and demonstrated this to display greater than 200-fold selectivity for HDAC8 (IC5o = 10nM) over the other HDAC isoforms [40b]. Interestingly, this compound induced caspase-dependent apoptosis in T-cell lymphomas and leukemias at low micromolar concentrations, but not in other hematopoietic or solid tumor cell lines. Furthermore, PCI-34051 does not cause detectable tubulin or histone acetylation. 

CTL-mediated cell killing (e.g., removal of active immune cells after an immune response) is effected by at least two major pathways. This includes Fas-mediated apoptosis (R6) and the release of granular perforin (which increases the permeability of the target cell membrane) and a group of proteases (e.g., serine protease granzyme B). Granzyme B can directly activate the target cell caspases (G8). 

Fig. 12. Effect of spontaneous apoptosis on the activation of caspase-3 in human eosinophils. Eosinophils (2 x 10 /ml) were cultured for 3 h. Cells were lysed and caspase-3 activity was measured by caspase-3 colorimetric assay kit (R D Systems). Enzymatic products were measured at 405 nm with BIOTEK EL340 ELISA microplate reader (BIO-TEK Instrument Inc., Vermont). Human recombinant caspase-3 (5 U) (Calbiochem, California) was used as a positive control. The stimulation index was determined by direct comparison to the level of the normal control. Background readings from cell lysates and buffers were substracted from the readings of both induced and uninduced samples samples before calculating the stimulation index in caspase-3 activity. The differences between control and treated groups were assessed by Student s i-test. P < 0.05 P < 0.001 (Z2).

Fig. 8.3. (Bottom) Thiomethylketone D of (88) is used as an example of a caspase 3 inhibitor designed via a docking-based library generation protocol. S1 and S2 denote the interaction sites within the binding pocket of caspase 3. (Top right) The thiomethylketone scaffold that is used as the starting point for library design. (Top left) The eight R-groups used to attach to the R attachment point of the scaffold.

At least ten caspases are known and many observations have confirmed their role in apoptosis (see also Chapter 32). In caspases 1 and 2 the side chains of Cys 285 and His 237 form the catalytic dyad and peptide NH groups of Cys 285 and Gly 238 form the oxyanion hole.333... 

Parallel to our group, a few other researchers also performed significant studies on anticancer (3-lactams. For example, (3-lactam derivatives (Fig. 2) induced DNA damage, inhibited DNA replication, and activated the apoptotic death program in human leukemic Jurkat T cells in a time and concentration-dependent manner. Importantly, (3-lactam 69 also inhibited proliferation and induced apoptosis in other human solid tumor cell lines (breast, prostate, and head-and-neck). It was believed that induction of apoptosis by 69 is associated with activation of p38 mitogen-activated protein (MAP) kinase, release of mitochondrial cytochrome c, and activation of the caspases. It was reported that apoptosis is blocked by a specific inhibitor to p38 kinase, implicating p38 MAP kinase as the major factor in (3-lactam-induced apoptosis [154]. This study was very significant. 

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