Combination Strategy Targeting the Hypoxia Inducible Factor-1α with Mammalian Target of Rapamycin and Histone Deacetylase Inhibitors

• Published in: Clinical cancer research Vol. 14; no. 11; pp. 3589 - 3597
• Main Authors: VERHEUL, Henk M. W, SALUMBIDES, Brenda, VAN ERP, Karen, HAMMERS, Hans, QIAN, David Z, SANNI, Tolib, ATADJA, Peter, PILI, Roberto
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.06.2008
• Subjects: Antineoplastic agents; Antineoplastic Combined Chemotherapy Protocols - administration & dosage; Biological and medical sciences; Blotting, Western; Cell Line, Tumor; Endothelial Cells - drug effects; Enzyme Inhibitors - administration & dosage; HDAC inhibitor; Histone Deacetylases - drug effects; Humans; Hydroxamic Acids - administration & dosage; Hypoxia-Inducible Factor 1, alpha Subunit - antagonists & inhibitors; Hypoxia-Inducible Factor 1, alpha Subunit - drug effects; Immunohistochemistry; Indoles; Medical sciences; mTOR inhibitor; Neoplasms, Experimental - drug therapy; Neovascularization, Pathologic - drug therapy; Oncogene Protein v-akt - drug effects; Oncogene Protein v-akt - metabolism; Pharmacology. Drug treatments; Phosphorylation - drug effects; Protein Kinases - drug effects; renal cell carcinoma; Signal Transduction - drug effects; Sirolimus - administration & dosage; TOR Serine-Threonine Kinases; Vascular Endothelial Growth Factor A - biosynthesis; Vascular Endothelial Growth Factor A - drug effects; Xenograft Model Antitumor Assays; Protein kinase mTOR; Target; Histone deacetylase inhibitor; Transcription factor HIF1; Targeting; Mammalian target of rapamycin
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-07-4306

Purpose: The hypoxia-inducible factor-1α (HIF-α) is a key regulator of tumor angiogenesis. Mammalian target of rapamycin (mTOR) and histone deacetylase (HDAC) inhibitors suppress tumor-induced angiogenesis by reducing tumor HIF-1α protein expression. Thus, we hypothesized that combination treatment of rapamycin and the HDAC inhibitor LBH589 has greater antiangiogenic and antitumor activity compared with single agents. Experimental Design: To evaluate the effect of LBH589 and rapamycin on HIF-1α in human prostate PC3, renal C2 carcinoma cell lines, and endothelial cells (human umbilical vein endothelial cells), we did Western blot analysis. To determine the antitumor activity of LBH589 and rapamycin, cell proliferation assays and xenograft experiments were conducted. Results: Western blotting showed that combination treatment of human umbilical vein endothelial cells, C2 and PC3, significantly reduced HIF-1α protein expression compared with single agents. Treatment with rapamycin resulted in inhibition of the downstream signals of the mTOR pathway and increased phosphorylation of Akt in C2 cells, whereas the constitutively activated Akt in PC3 cells was not modulated. LBH589 decreased both constitutively expressed and rapamycin-induced phosphorylated Akt levels in PC3 and C2 cell lines. In clonogenic assays, the combination treatment had a greater inhibitory effect in PC3 cells (93 ± 1.4%) compared with single agents (66 ± 9% rapamycin and 43 ± 4% LBH589). Combination of rapamycin and LBH589 significantly inhibited PC3 and C2 in vivo tumor growth and angiogenesis as measured by tumor weight and microvessel density. Conclusions: Combination treatment of mTOR and HDAC inhibitors represents a rational therapeutic strategy targeting HIF-1α that warrants clinical testing.