Biodistribution and Efficacy Studies of the Proteasome Inhibitor BSc2118 in a Mouse Melanoma Model

Abstract

Inhibition of the proteasome offers many therapeutic possibilities in inflammation as well as in neoplastic diseases. However, clinical use of proteasome inhibitors is limited by the development of resistance or severe side effects. In our study we characterized the anti-tumor properties of the novel proteasome inhibitor BSc2118. The sensitivity of tumor lines to BSc2118 was analyzed in comparison to bortezomib using crystal violet staining in order to assess cell viability. The In Vivo distribution of BSc2118 in mouse tissues was tracked by a fluorescent-modified form of BSc2118 (BSc2118-FL) and visualized by confocal microscopy. Inhibition of the 20S proteasome was monitored both in cultured cell lines and in mice, respectively. Finally, safety and efficacy of BSc2118 was evaluated in a mouse melanoma model. BSc2118 inhibits proliferation of different tumor cell lines with a similar potency as compared with bortezomib. Systemic administration of BSc2118 in mice is well tolerated, even when given in a dose of 60 mg/kg body weight. After systemic injection of BSc2118 or bortezomib similar proteasome inhibition patterns are observed within the murine organs. Detection of BSc2118-FL revealed correlation of distribution pattern of BSc2118 with inhibition of proteasomal activity in cells or mouse tissues. Finally, administration of BSc2118 in a mouse melanoma model shows significant local anti-tumor effects. Concluding, BSc2118 represents a novel low-toxic agent that might be alternatively used for known proteasome inhibitors in anti-cancer treatment.

Cell‐Based Optimization of Covalent Reversible Ketoamide Inhibitors Bridging the Unprimed to the Primed Site of the Proteasome β5 Subunit

“…Furthermore fluorescence is concentrated in clusters, which are most likely aggresomes consisting of misfolded polyubiquitinated proteins aggregating with proteasomes, which is reported to be a result of proteasome inhibition. [32] These results are in line with previous reports of green [33] as well as red-shifted [34] fluorescent derivatives of peptidic aldehyde 5 colocalizing with proteasome in aggresomes and allowing selective proteasome-staining. The uptake of fluorescent ketoamides in Danio rerio embryos is most intense upon treatment with 33, while 32 and 34 show only slightly increased fluorescence compared to control embryos (Figure 6d).…”

Anti-tumor activity of the proteasome inhibitor BSc2118 against human multiple myeloma

“…The anti-tumor activity of BSc2118 has first been evaluated in melanoma cell lines and mouse models [37,38]. The results demonstrate that BSc2118 is more potent and stable than MG-132 in the reduction of tumor cell viability through inhibition of the 20S proteasome in vitro and in vivo, while BSc2118 is well tolerated, compared to bortezomib.…”

The proteasomal deubiquitinating enzyme PSMD14 regulates macroautophagy by controlling Golgi-to-ER retrograde transport

“…Proteasome activity was quantitatively assessed in H4 cell extracts using the β5-selective fluorogenic substrate succinyl-leucine-leucine-valine-tyrosine-4-methyl-7-courmarylamide (Suc-LLVY-AMC, Calbiochem, Burlington, MA, USA) using an adapted protocol 87 . Briefly, cells were left untreated or treated for 4 h with different amounts of CZM (between 2 and 10 μM) or with 10 μM MG132.…”