Procaspase-3 Activation as an Anti-Cancer Strategy: Structure−Activity Relationship of Procaspase-Activating Compound 1 (PAC-1) and Its Cellular Co-Localization with Caspase-3

Abstract

A goal of personalized medicine as applied to oncology is to identify compounds that exploit a defined molecular defect in a cancerous cell. A compound called procaspase-activating compound 1 (PAC-1) was reported that enhances the activity of procaspase-3 in vitro and induces apoptotic death in cancer cells in culture and in mouse xenograft models. Experimental evidence indicates that PAC-1 activates procaspase-3 in vitro through chelation of inhibitory zinc ions. Described herein is the synthesis and biological activity of a family of PAC-1 derivatives where key functional groups have been systematically altered. Analysis of these compounds reveals a strong correlation between the in vitro procaspase-3 activating effect and their ability to induce death in cancer cells in culture. Importantly, we also show that a fluorescently-labeled version of PAC-1 co-localizes with sites of caspase-3 activity in cancer cells. The data presented herein further bolster the hypothesis that PAC-1 induces apoptosis in cancer cells through the direct activation of procaspase-3, has implications for the design and discovery of next-generation procaspase-3 activating compounds, and sheds light on the anti-apoptotic role of cellular zinc.

Synergistic antitumor activity of pro‐apoptotic agent PAC‐1 with cisplatinum by the activation of CASP3 in pulmonary adenocarcinoma cell line H1299

“…40 Mechanistically, PAC-1 may bind Zn ions competitively and promote cleavage of CASP3 into C-CASP. 14,41 PAC-1-mediated C-CASP3 activation was also confirmed by confocal microscopy in our study. In EGFR wt KRAS wt ALK wt H1299 cells, PAC-1 induced greater levels of C-CASP3 compared with EGFR or KRAS mutant cells, suggesting that in H1299 cells, CASP3 might be activated more readily by PAC-1, consistent with the flow cytometry results, which showed sequential treatment of Cis followed by PAC-1 could cause a high rate of apoptosis in H1299 cells.…”

“…12 Promotion of the pro-apoptotic activation process is one strategy for cancer treatment. 13 In this study, cell models with different genetic alterations, such as EGFR and KRAS mutations and ALK gene rearrangements, were used to evaluate the antitumor activity of the caspase 3 activator "procaspaseactivating compound 1" (PAC-1) 14 and its potential synergistic anti-cancer effects when combined with cisplatinum (Cis). We also sought to determine the underlying molecular mechanisms.…”

Zinc-mediated Allosteric Inhibition of Caspase-6

“…Treatment of HL-60 cells with zinc chelators increases apoptosis via activation of caspase-3 (32). The small molecule procaspase-3 activator PAC-1 releases procaspase-3 from zinc-mediated inhibition (33)(34)(35). The details of caspase-3 zinc-mediated inhibition have not been reported.…”

Systems Analysis of Cancer Cell Heterogeneity in Caspase-dependent Apoptosis Subsequent to Mitochondrial Outer Membrane Permeabilization

“…This fact becomes important when designing and applying chemotherapeutic drugs that aim to enhance or restore apoptosis by targeting a particular protein or a particular protein interaction. As such, Smac mimetics (44) enhance apoptosis by blocking the apoptosis inhibitor XIAP, whereas some compounds directly activate caspases (45)(46)(47), and others target protein degradation (48 -50). Because these drugs target specific protein interactions and because the relative importance of protein interactions may differ between cancer cells, the impact of these drugs on cancer cell apoptosis may vary between different cell lines, different patients, and different cancers.…”