ritonavir and tanespimycin

Our previous study showed that the combination of a histone deacetylase (HDAC) inhibitor and an HIV protease inhibitor is effective against renal cancer cells. Because HDAC inhibition disrupts the chaperon function of heat shock protein (HSP) 90, we hypothesized that the combination of 17-allylamino-17-demethoxygeldanamycin (17-AAG), an inhibitor of HSP90, and the HIV protease inhibitor ritonavir would also act against renal cancer. The combination of 17-AAG and ritonavir induced apoptosis and inhibited the proliferation of renal cancer cells effectively. It also suppressed the expression of cyclin-dependent kinase 4 and cyclin D1, leading to the accumulation of the cells in the sub-G1 fraction. The expression of HSPs 27, 70 and 90 was increased by 17-AAG alone but reduced by 17-AAG combined with ritonavir. The combination decreased the expression of heat shock factor-1 (HSF-1), an HSP transcription factor, and this might be one of the mechanisms of the effect of the combination. We have also found that silencing of HSF-1 by siRNA inhibited the proliferation of renal cancer cells and that in surgically resected specimens the levels of HSF-1 expression in renal cancer tissue are higher than those in normal parenchyma. This is the first study showing the beneficial effect of combining 17-AAG and ritonavir and our data suggest that HSF-1 may be a novel therapeutic target in the treatment of renal cancer.

Topics: Antineoplastic Agents; Apoptosis; Benzoquinones; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin D1; Cyclin-Dependent Kinase 4; DNA-Binding Proteins; Drug Synergism; G1 Phase Cell Cycle Checkpoints; Gene Expression; Gene Expression Profiling; Gene Knockdown Techniques; Heat Shock Transcription Factors; HSP90 Heat-Shock Proteins; Humans; Kidney Neoplasms; Lactams, Macrocyclic; Ritonavir; RNA Interference; Transcription Factors

Certain ritonavir resistance mutations impair HIV infectivity through incomplete Gag processing by the mutant viral protease. Analysis of the mutant virus phenotype indicates that accumulation of capsid-spacer peptide 1 precursor protein in virus particles impairs HIV infectivity and that the protease mutant virus is arrested during the early postentry stage of HIV infection before proviral DNA synthesis. However, activation of the target cell can rescue this defect, implying that specific host factors expressed in activated cells can compensate for the defect in ritonavir-resistant HIV. This ability to rescue impaired HIV replication presented a unique opportunity to identify host factors involved in postentry HIV replication, and we designed a functional genetic screen so that expression of a given host factor extracted from activated T cells would lead directly to its discovery by rescuing mutant virus replication in nonactivated T cells. We identified the cellular heat shock protein 90 kDa α (cytosolic), class B member 1 (HSP90AB1) as a host factor that can rescue impaired replication of ritonavir-resistant HIV. Moreover, we show that pharmacologic inhibition of HSP90AB1 with 17-(allylamino)-17-demethoxygeldanamycin (tanespimycin) has potent in vitro anti-HIV activity and that ritonavir-resistant HIV is hypersensitive to the drug. These results suggest a possible role for HSP90AB1 in postentry HIV replication and may provide an attractive target for therapeutic intervention.

Topics: Benzoquinones; Drug Resistance, Viral; Gene Expression Regulation, Viral; HIV; HIV Infections; HSP90 Heat-Shock Proteins; Humans; Jurkat Cells; Lactams, Macrocyclic; Lymphocyte Activation; Proviruses; Ritonavir; T-Lymphocytes; Virus Replication