Loss of the Phenolic Hydroxyl Group and Aromaticity from the Side Chain of Anti-Proliferative 10-Methyl-aplog-1 a Simplified Analog of Aplysiatoxin Enhances Its Tumor-Promoting and Proinflammatory Activities

摘要

Aplysiatoxin (ATX) is a protein kinase C (PKC) activator with potent tumor-promoting activity. In contrast, 10-methyl-aplog-1 (>1), a simplified analog of ATX, was anti-proliferative towards several cancer cell lines without significant tumor-promoting and proinflammatory activities. To determine the effects of the phenolic group on the biological activities of >1, we synthesized new derivatives (>2, >3) that lack the phenolic hydroxyl group and/or the aromatic ring. Compound >2, like >1, showed potent anti-proliferative activity against several cancer cell lines, but little with respect to tumor-promoting and proinflammatory activities. In contrast, >3 exhibited weaker growth inhibitory activity, and promoted inflammation and tumorigenesis. The binding affinity of >3 for PKCδ, which is involved in growth inhibition and apoptosis, was several times lower than those of >1 and >2, possibly due to the absence of the hydrogen bond and CH/π interaction between its side chain and either Met-239 or Pro-241 in the PKCδ-C1B domain. These results suggest that both the aromatic ring and phenolic hydroxyl group can suppress the proinflammatory and tumor-promoting activities of >1 and, therefore, at least the aromatic ring in the side chain of >1 is indispensable for developing anti-cancer leads with potent anti-proliferative activity and limited side effects. In accordance with the binding affinity, the concentration of >3 necessary to induce PKCδ-GFP translocation to the plasma membrane and perinuclear regions in HEK293 cells was higher than that of >1 and >2. However, the translocation profiles for PKCδ-GFP due to induction by >1–>3 were similar.