Summary Inactivation of the TCA cycle enzyme, fumarate hydratase (FH), drives a metabolic shift to aerobic glycolysis in FH-deficient kidney tumors and cell lines from patients with hereditary leiomyomatosis renal cell cancer (HLRCC), resulting in decreased levels of AMP-activated kinase (AMPK) and p53 tumor suppressor, and activation of the anabolic factors, acetyl-CoA carboxylase and ribosomal protein S6. Reduced AMPK levels leads to diminished expression of the DMT1 iron transporter, and the resulting cytosolic iron deficiency activates the iron regulatory proteins, IRP1 and IRP2, and increases expression of the hypoxia inducible factor HIF-1α, but not HIF-2α. Silencing of HIF-1α or activation of AMPK diminishes invasive activities, indicating that alterations of HIF-1α and AMPK contribute to the oncogenic growth of FH-deficient cells.

Drugs that target novel surfaces on the androgen receptor (AR) and/or novel AR regulatory mechanisms are promising alternatives for the treatment of castrate-resistant prostate cancer. The 52 kDa FK506 binding protein (FKBP52) is an important positive regulator of AR in cellular and whole animal models and represents an attractive target for the treatment of prostate cancer. We used a modified receptor-mediated reporter assay in yeast to screen a diversified natural compound library for inhibitors of FKBP52-enhanced AR function. The lead compound, termed MJC13, inhibits AR function by preventing hormone-dependent dissociation of the Hsp90-FKBP52-AR complex, which results in less hormonebound receptor in the nucleus. Assays in early and late stage human prostate cancer cells demonstrated that MJC13 inhibits AR-dependent gene expression and androgen-stimulated prostate cancer cell proliferation.immunophilin | FKBP4 | steroid hormone receptor A ndrogens are a major stimulator of prostate tumor growth, and all current therapies act as classic antagonists by competing with androgens for binding the androgen receptor (AR) hormone binding pocket. This mechanism of action exploits the dependence of AR on hormone activation, but current treatment options become ineffective in castrate-resistant prostate cancer (CRPC), although CRPC remains ligand/AR-dependent. Thus, drugs that target novel surfaces on AR and/or novel AR regulatory mechanisms may provide promising alternatives for the treatment of CRPC (reviewed in ref. 1).The maturation of cytoplasmic steroid hormone receptors (SHR) to a mature hormone binding conformation is a highly ordered, dynamic process that involves multiple chaperone and cochaperone components (reviewed in ref. 2), all of which present potential opportunities for therapeutic intervention. The final mature complex in which the receptor is capable of high affinity hormone binding includes heat shock protein 90 (Hsp90), a 23 kDa cochaperone (p23), and one of a class of proteins (termed FKBPs) characterized by their Hsp90-binding tetratricopeptide repeat (TPR) domain. The 52 kDa FK506 binding protein (FKBP52) associates with receptor-Hsp90 complexes by way of a C-terminal TPR domain and is a specific positive regulator of AR, glucocorticoid receptor (GR), and progesterone receptor (PR) signaling (3-5). FKBP52 is required for normal male sexual differentiation and development in mice as the fkbp52-deficient mice (52KO) display characteristics of partial androgen insensitivity syndrome including dysgenic prostate (4, 6). FKBP proteins are validated targets of immunosuppressive drugs. FK506 (Tacrolimus) is used clinically to suppress the immune system following organ transplantation. FK506 binds within the peptidyl-prolyl isomerase (PPIase) catalytic pocket of a related family member, FKBP12. The chemical groups of FK506 that project out from the PPIase pocket allow the FKBP12-drug complex to bind tightly to and inhibit calcineurin, which ultimately leads to immunosupression (7). Although FK506 binding ...

Castration-resistant prostate cancer (CRPC) is characterized by reactivation of androgen receptor (AR) signaling, in part by elevated expression of AR splice variants (ARv) including ARv7, a constitutively active, ligand binding domain (LBD)-deficient variant whose expression has been correlated with therapeutic resistance and poor prognosis. In a screen to identify small-molecule dual inhibitors of both androgen-dependent and androgen-independent AR gene signatures, we identified the chalcone C86. Binding studies using purified proteins and CRPC cell lysates revealed C86 to interact with Hsp40. Pull-down studies using biotinylated-C86 found Hsp40 present in a multiprotein complex with full-length (FL-) AR, ARv7, and Hsp70 in CRPC cells. Treatment of CRPC cells with C86 or the allosteric Hsp70 inhibitor JG98 resulted in rapid protein destabilization of both FL-AR and ARv, including ARv7, concomitant with reduced FL-AR- and ARv7-mediated transcriptional activity. The glucocorticoid receptor, whose elevated expression in a subset of CRPC also leads to androgen-independent AR target gene transcription, was also destabilized by inhibition of Hsp40 or Hsp70. , Hsp40 or Hsp70 inhibition demonstrated single-agent and combinatorial activity in a 22Rv1 CRPC xenograft model. These data reveal that, in addition to recognized roles of Hsp40 and Hsp70 in FL-AR LBD remodeling, ARv lacking the LBD remain dependent on molecular chaperones for stability and function. Our findings highlight the feasibility and potential benefit of targeting the Hsp40/Hsp70 chaperone axis to treat prostate cancer that has become resistant to standard antiandrogen therapy. These findings highlight the feasibility of targeting the Hsp40/Hsp70 chaperone axis to treat CRPC that has become resistant to standard antiandrogen therapy. .

PURPOSE We previously demonstrated that thalidomide appears to add to the activity of docetaxel in metastatic castration-resistant prostate cancer (CRPC). Phase II studies combining docetaxel with bevacizumab have had substantial antitumor activity. We hypothesized that the combination of docetaxel plus these antiangiogenic drugs with different targets would have substantial clinical activity. To explore safety and efficacy, this was tested in mice and in human patients. PATIENTS AND METHODS Preclinical efficacy of the combination therapy was evaluated in PC3 xenograft mice. Sixty patients with progressive metastatic CRPC received intravenous docetaxel and bevacizumab plus oral thalidomide and prednisone. The primary end point was a prostate-specific antigen (PSA) decline of > or = 50%. Secondary end points included time to progression, overall survival, and safety. Results In the mouse model, combination therapy of docetaxel, bevacizumab, and thalidomide inhibited tumor growth most effectively. In the clinical trial, 90% of patients receiving the combination therapy had PSA declines of > or = 50%, and 88% achieved a PSA decline of > or = 30% within the first 3 months of treatment. The median time to progression was 18.3 months, and the median overall survival was 28.2 months in this group with a Halabi-predicted survival of 14 months. While toxicities were manageable, all patients developed grade 3/4 neutropenia. CONCLUSION The addition of bevacizumab and thalidomide to docetaxel is a highly active combination with manageable toxicities. The estimated median survival is encouraging, given the generally poor prognosis of this patient population. These results suggest that definitive clinical trials combining antiangiogenic agent combinations with docetaxel are warranted to improve treatment outcomes for patients with metastatic CRPC.