Milder degenerative effects of Carfilzomib vs. Bortezomib in the Drosophila model: a link to clinical adverse events

Abstract

Proteasome inhibitors, e.g. Bortezomib (BTZ) and Carfilzomib (CFZ), have demonstrated clinical efficacy against haematological cancers. Interestingly, several adverse effects are less common, compared to BTZ, in patients treated with CFZ. As the molecular details of these observations remain not well understood we assayed the pathophysiological effects of CFZ vs. BTZ in the Drosophila experimental model. Mass Spectrometry analyses showed that neither CFZ nor BTZ are hydrolysed in flies’ tissues, while at doses inducing similar inhibition of the rate limiting for protein breakdown chymotrypsin-like (CT-L) proteasomal activity, CFZ treatment resulted in less intense increase of oxidative stress or activation of antioxidant and proteostatic modules. Also, despite comparable cardiotoxicity likely due to disrupted mitochondrial function, CFZ did not affect developmental processes, showed minimal neuromuscular defects and reduced to a lesser extent flies’ healthspan. Studies in flies, human cancer cell lines and blood cells isolated from Multiple Myeloma patients treated with CFZ or BTZ revealed, that the increased BTZ toxicity likely relates to partial co-inhibition of the caspase-like (C-L) proteasomal activity Supportively, co-treating flies with CFZ and a C-L selective proteasome inhibitor exacerbated CFZ-mediated toxicity. Our findings provide a reasonable explanation for the differential adverse effects of CFZ and BTZ in the clinic.

Proteomic approach for understanding milder neurotoxicity of Carfilzomib against Bortezomib

“…The peripheral neuropathy effects of the BTZ combination were approximately 5 fold higher than CFZ combination 13 . A very recent study, showed the mechanisms of milder cardiotoxic effects of CFZ compared to BTZ in the Drosophila model 14 .…”

Non‐lethal proteasome inhibition activates pro‐tumorigenic pathways in multiple myeloma cells

“…As reported before, 16,17 we noted that for both JJN3 ( Figure S2C) and RPMI 8226 ( Figure S2D) cells, the Rub999, Rub1024 and PR671A inhibitors selectively suppressed the CT-L, C-L and T-L activities, respectively. Thus, as was suggested, [19][20][21] the high percentage of cell death in MM cells achieved by BTZ and EPOX (and likely CFZ) is associated with co-inhibition of more than one proteasomal peptidases. These findings also support the notion that the CT-L activity is the rate limiting for protein breakdown and accordingly, selective inhibition of the β5 peptidase by Rub999 increased cell death, yet, as mentioned less effectively and at higher concentrations as compared to BTZ or EPOX, and likely CFZ.…”

“…Thus, co-inhibition of either the C-L or the T-L sites is required to effectively inhibit protein breakdown and to increase sensitivity of MM cells and/or other types of cancer cells (eg solid tumours) to PIs. 16,19,20 In support, head-to-head comparison of clinically available PIs showed that in the clinically relevant setting only the co-inhibition of C-L or T-L with CT-L activity achieves meaningful functional proteasome inhibition and cytotoxicity; in this setting, the selective CT-L/T-L inhibition of both constitutive and immunoproteasome is the most cytotoxic. 21 In terms of the affected cell signalling pathways, non-lethal proteasome inhibition induced PI-, time-and cell type-specific readouts, likely due to differences in the genetic backgrounds of the cell lines under study 29 ; this heterogeneity at both the genome and transcriptome levels among tumours from different patients is a MM hallmark seen also at the clinical setting.…”

“…Nonetheless, as is evident by the enhanced (vs Rub999) BTZ and CFZ cytotoxicity in MM cells, the inhibition of CT‐L alone is rarely sufficient to efficiently block protein degradation. Thus, co‐inhibition of either the C‐L or the T‐L sites is required to effectively inhibit protein breakdown and to increase sensitivity of MM cells and/or other types of cancer cells (eg solid tumours) to PIs . In support, head‐to‐head comparison of clinically available PIs showed that in the clinically relevant setting only the co‐inhibition of C‐L or T‐L with CT‐L activity achieves meaningful functional proteasome inhibition and cytotoxicity; in this setting, the selective CT‐L/T‐L inhibition of both constitutive and immunoproteasome is the most cytotoxic …”

Alterations in Organismal Physiology, Impaired Stress Resistance, and Accelerated Aging inDrosophilaFlies Adapted to Multigenerational Proteome Instability

“…UPP inhibitors which have demonstrated clinical efficacy include bortezomib (BTZ) [19] and carfilzomib [20]. BTZ is a slowly reversible inhibitor that binds the catalytic site of the 26S proteasome enabling inhibition of the CT-L and, to a lesser extent, of C-L and T-L activities [19, 21, 22]. Nevertheless, the development of severe adverse effects linked to the usage of proteasome inhibitors, such as peripheral neuropathies and/or cardiovascular diseases, along with inherent or acquired drug resistance remain a significant clinical problem [19, 23].…”