Hirsutinolide Series Inhibit Stat3 Activity, Alter GCN1, MAP1B, Hsp105, G6PD, Vimentin, TrxR1, and Importin α‑2 Expression, and Induce Antitumor Effects against Human Glioma

We report that hirsutinolide series, <b>6</b>, <b>7</b>, <b>10</b>, <b>11</b>, <b>20</b>, and <b>22</b>, and the semisynthetic analogues, <b>30</b>, <b>31</b>, <b>33</b>, and <b>36</b>, inhibit constitutively active signal transducer and activator of transcription (Stat)­3 and malignant glioma phenotype. A position 13 lipophilic ester group is required for activity. Molecular modeling and nuclear magnetic resonance structural analyses reveal direct hirsutinolide:Stat3 binding. One-hour treatment of cells with <b>6</b> and <b>22</b> also upregulated importin subunit α-2 levels and repressed translational activator GCN1, microtubule-associated protein (MAP)­1B, thioredoxin reductase (TrxR)­1 cytoplasmic isoform 3, glucose-6-phosphate 1-dehydrogenase isoform a, Hsp105, vimentin, and tumor necrosis factor α-induced protein (TNAP)­2 expression. Active hirsutinolides inhibited anchorage-dependent and three-dimensional spheroid growth, survival, and migration of human glioma lines and glioma patients’ tumor-derived xenograft cells harboring constitutively active Stat3. Oral gavage delivery of <b>6</b> or <b>22</b> inhibited human glioma tumor growth in subcutaneous mouse xenografts. The inhibition of Stat3 signaling represents part of the hirsutinolide-mediated mechanisms to induce antitumor effects