gedunin and Neoplasms

The chemotherapy of tumors is frequently limited by the development of resistance and severe side effects. Phytochemicals may offer promising candidates to meet the urgent requirement for new anticancer drugs. We screened 69 phytochemicals, and focused on gedunin to analyze its molecular modes of action. Pearson test-base correlation analyses of the log

Topics: Antineoplastic Agents; ATP-Binding Cassette Transporters; Cell Line, Tumor; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Limonins; Molecular Docking Simulation; Neoplasms; Phytochemicals; Poisons; Proteomics; RNA, Messenger; Tubulin; Tubulin Modulators

Heat shock protein 90 (Hsp90) facilitates the maturation of many newly synthesized and unfolded proteins (clients) via the Hsp90 chaperone cycle, in which Hsp90 forms a heteroprotein complex and relies upon cochaperones, immunophilins, etc., for assistance in client folding. Hsp90 inhibition has emerged as a strategy for anticancer therapies due to the involvement of clients in many oncogenic pathways. Inhibition of chaperone function results in client ubiquitinylation and degradation via the proteasome, ultimately leading to tumor digression. Small molecule inhibitors perturb ATPase activity at the N-terminus and include derivatives of the natural product geldanamycin. However, N-terminal inhibition also leads to induction of the pro-survival heat shock response (HSR), in which displacement of the Hsp90-bound transcription factor, heat shock factor-1, translocates to the nucleus and induces transcription of heat shock proteins, including Hsp90. An alternative strategy for Hsp90 inhibition is disruption of the Hsp90 heteroprotein complex. Disruption of the Hsp90 heteroprotein complex is an effective strategy to prevent client maturation without induction of the HSR. Cucurbitacin D, isolated from Cucurbita texana, and 3-epi-isocucurbitacin D prevented client maturation without induction of the HSR. Cucurbitacin D also disrupted interactions between Hsp90 and two cochaperones, Cdc37 and p23.

Topics: Benzoquinones; Cucurbitaceae; DNA-Binding Proteins; Heat Shock Transcription Factors; HSP90 Heat-Shock Proteins; Humans; Lactams, Macrocyclic; MCF-7 Cells; Molecular Chaperones; Molecular Structure; Neoplasms; Transcription Factors; Triterpenes

Pharmacological inhibition of Hsp90 is an exciting option for cancer therapy. The clinical efficacy of Hsp90 inhibitors is, however, less than expected. Binding of the co-chaperone p23 to Hsp90 and induced overexpression of anti-apoptotic proteins Hsp70 and Hsp27 are thought to contribute to this outcome. Herein, we report that the natural product gedunin may provide a new alternative to inactivate the Hsp90 machine. We show that gedunin directly binds to p23 and inactivates it, without overexpression of Hsp27 and relatively modest induction of Hsp70. Using molecular docking and mutational analysis, we mapped the gedunin-binding site on p23. Functional analysis shows that gedunin inhibits the p23 chaperoning activity, blocks its cellular interaction with Hsp90, and interferes with p23-mediated gene regulation. Cell treatment with gedunin leads to cancer cell death by apoptosis through inactivation of p23 and activation of caspase 7, which cleaves p23 at the C terminus. These results provide important insight into the molecular mechanism of action of this promising lead compound.

Topics: Animals; Apoptosis; Binding Sites; Blotting, Western; Caspase 7; Cell Line, Tumor; Cells, Cultured; HeLa Cells; HSP70 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Humans; Limonins; MCF-7 Cells; Mice; Microscopy, Fluorescence; Models, Molecular; Molecular Chaperones; Mutation; Neoplasms; Protein Binding; Protein Structure, Tertiary; Sf9 Cells; Signal Transduction