Neuroprotective activity of ursodeoxycholic acid in CHMP2BIntron5 models of frontotemporal dementia.

Frontotemporal dementia (FTD) is one of the most prevalent forms of early-onset dementia. It represents part of the FTD-Amyotrophic Lateral Sclerosis (ALS) spectrum, a continuum of genetically and pathologically overlapping disorders. FTD-causing mutations in CHMP2B, a gene encoding a core component of the heteromeric ESCRT-III Complex, lead to perturbed endosomal-lysosomal and autophagic trafficking with impaired proteostasis. While CHMP2B mutations are rare, dysfunctional endosomal-lysosomal signalling is common across the FTD-ALS spectrum. Using our established Drosophila and mammalian models of CHMP2BIntron5 induced FTD we demonstrate that the FDA-approved compound Ursodeoxycholic Acid (UDCA) conveys neuroprotection, downstream of endosomal-lysosomal dysfunction in both Drosophila and primary mammalian neurons. UDCA exhibited a dose dependent rescue of neuronal structure and function in Drosophila pan-neuronally expressing CHMP2BIntron5. Rescue of CHMP2BIntron5 dependent dendritic collapse and apoptosis with UDCA in rat primary neurons was also observed. UDCA failed to ameliorate aberrant accumulation of endosomal and autophagic organelles or ubiquitinated neuronal inclusions in both models. We demonstrate the neuroprotective activity of UDCA downstream of endosomal-lysosomal and autophagic dysfunction, delineating the molecular mode of action of UDCA and highlighting its potential as a therapeutic for the treatment of FTD-ALS spectrum disorders.

Vorinostat and bortezomib synergistically cause ubiquitinated protein accumulation in prostate cancer cells.

PURPOSE: Protein ubiquitination is a novel strategy used to treat malignancies. We investigated whether the histone deacetylase inhibitor vorinostat (Cayman Chemical, Ann Arbor, Michigan) and the proteasome inhibitor bortezomib (LC Laboratories, Woburn, Massachusetts) would synergistically cause the accumulation of ubiquitinated proteins in prostate cancer cells. MATERIALS AND METHODS: LNCaP, PC-3 and DU 145 cells (ATCC™) were treated with vorinostat and/or bortezomib. Cell viability and induction of apoptosis were assessed. In vivo efficacy was evaluated in a murine subcutaneous tumor model using PC-3 cells. The influence of androgen receptor expression on bortezomib efficacy was examined using RNA interference. Changes in the expression of ubiquitinated proteins, cell cycle associated proteins and acetylated histone were evaluated. RESULTS: Androgen receptor expression seemed to decrease bortezomib activity. PC-3 and DU 145 cells were more susceptible to bortezomib than LNCaP cells and the silencing of androgen receptor expression in LNCaP cells enhanced bortezomib activity. Vorinostat and bortezomib synergistically induced apoptosis, inhibited prostate cancer cell growth and suppressed tumor growth in a murine xenograft model. The combination decreased cyclin D1 and cyclin-dependent kinase 4 expression, and increased p21 expression. The combination synergistically caused the accumulation of ubiquitinated proteins and histone acetylation. This histone acetylation was a consequence of the accumulation of ubiquitinated proteins. CONCLUSIONS: Vorinostat and bortezomib inhibit the growth of prostate cancer cells synergistically by causing ubiquitinated proteins to accumulate in cells. The current study provides a framework for testing the combination in patients with advanced prostate cancer.

Ritonavir interacts with bortezomib to enhance protein ubiquitination and histone acetylation synergistically in renal cancer cells.

OBJECTIVE: To investigate the combined effects of the HIV protease inhibitor ritonavir and proteasome inhibitor bortezomib on renal cancer cells. Ritonavir induces endoplasmic reticulum (ER) stress and we hypothesized that inhibiting proteasome activity under ER stress would further inhibit cancer cell growth by enhancing protein ubiquitination. METHODS: The effectiveness of the combination of ritonavir and bortezomib on renal cancer cells (Caki-1, ACHN, 786-O, 769-P) was assessed by MTS assay, colony formation assay, cell cycle analysis, and annexin-V assay. In vivo efficacy was evaluated using mice subcutaneous tumor models. Induction of ER stress, protein ubiquitination, histone acetylation, and changes in the expression of histone deacetylase (HDAC) were evaluated by Western blotting. RESULTS: Ritonavir in combination with bortezomib induced apoptosis and inhibited renal cancer growth synergistically at clinically feasible concentrations. In subcutaneous tumor models using Caki-1 cells, 10-day treatment with the combination was well tolerated and inhibited tumor growth significantly. Ritonavir induced ER stress and the combination enhanced protein ubiquitination synergistically. The combination was also found to induce histone acetylation by suppressing the HDAC expression. CONCLUSION: The combination of ritonavir and bortezomib inhibits renal cancer growth synergistically. The effectiveness of the combination is caused by protein ubiquitination and histone acetylation. Our results provide a rationale for investigating the combination in patients with renal cancer.