From the Cyclooxygenase-2 Inhibitor Celecoxib to a Novel Class of 3-Phosphoinositide-Dependent Protein Kinase-1 Inhibitors

TLDR

Celecoxib blocks Akt activation by inhibiting PDK‑1, but its weak potency (IC₅₀ ≈48 µM) limits its antitumor effects. The study aimed to structure‑based optimize celecoxib into more potent PDK‑1 inhibitors to enhance enzyme inhibition and cancer cell growth suppression. Using ATP‑competitive kinetics, structure‑activity analysis, and docking, two analogs (OSU‑03012 and OSU‑03013) were designed that inhibit PDK‑1 with low‑µM IC₅₀ and induce apoptosis in PC‑3 cells. These compounds caused Akt dephosphorylation, p70 S6K inhibition, and ~3 µM growth inhibition across 60 cell lines, and overexpression of active PDK‑1/Akt partially rescued apoptosis, underscoring their translational potential.

Abstract

Abstract The blockade of Akt activation through the inhibition of 3-phosphoinositide-dependent kinase-1 (PDK-1) represents a major signaling mechanism whereby celecoxib mediates apoptosis. Celecoxib, however, is a weak PDK-1 inhibitor (IC50, 48 μm), requiring at least 30 μm to exhibit discernable effects on the growth of tumor cells in vitro. Here, we report the structure-based optimization of celecoxib to develop PDK-1 inhibitors with greater potency in enzyme inhibition and growth inhibition. Kinetics of PDK-1 inhibition by celecoxib with respect to ATP suggest that celecoxib derivatives inhibit PDK-1 by competing with ATP for binding, a mechanism reminiscent to that of many kinase inhibitors. Structure-activity analysis together with molecular modeling was used to generate compounds that were tested for their potency in inhibiting PDK-1 kinase activity and in inducing apoptosis in PC-3 prostate cancer cells. Docking of potent compounds into the ATP-binding site of PDK-1 was performed for lead optimization, leading to two compounds, OSU-03012 and OSU-03013, with IC50 values in PDK-1 inhibition and apoptosis induction in the low μm range. Exposure of PC-3 cells to these agents led to Akt dephosphorylation and inhibition of p70 S6 kinase activity. Moreover, overexpression of constitutively active forms of PDK-1 and Akt partially protected OSU-03012-induced apoptosis. Screening in a panel of 60 cell lines and more extensive testing in PC-3 cells indicated that the mean concentration for total growth inhibition was ∼3 μm for both agents. Considering the conserved role of PDK-1/Akt signaling in promoting tumorigenesis, these celecoxib analogs are of translational relevance for cancer prevention and therapy.