Tubulin binding potentially clears up Bortezomib and Carfilzomib differential neurotoxic effect

Abstract

Proteasome inhibitors (PIs) represent the gold standard in the treatment of multiple myeloma. Among PIs, Bortezomib (BTZ) is frequently used as first line therapy, but peripheral neuropathy (PN), occurring approximately in 50% of patients, impairs their life, representing a dose-limiting toxicity. Carfilzomib (CFZ), a second-generation PI, induces a significantly less severe PN. We investigated possible BTZ and CFZ off-targets able to explain their different neurotoxicity profiles. In order to identify the possible PIs off-targets we used the SPILLO-PBSS software that performs a structure-based in silico screening on a proteome-wide scale. Among the top-ranked off-targets of BTZ identified by SPILLO-PBSS we focused on tubulin which, by contrast, did not turn out to be an off-target of CFZ. We tested the hypothesis that the direct interaction between BTZ and microtubules would inhibit the tubulin alfa GTPase activity, thus reducing the microtubule catastrophe and consequently furthering the microtubules polymerization. This hypothesis was validated in a cell-free model, since BTZ (but not CFZ) reduces the concentration of the free phosphate released during GTP hydrolysis. Moreover, NMR binding studies clearly demonstrated that BTZ, unlike CFZ, is able to interact with both tubulin dimers and polymerized form. Our data suggest that different BTZ and CFZ neurotoxicity profiles are independent from their proteasome inhibition, as demonstrated in adult mice dorsal root ganglia primary sensory neurons, and, first, we demonstrate, in a cell free model, that BTZ is able to directly bind and perturb microtubules.

Axonal degeneration in chemotherapy-induced peripheral neurotoxicity: clinical and experimental evidence

“… 5 Similarly, in vitro data showed that bortezomib is also able to enhance tubulin polymerisation 16 and disrupt axonal transport, 17 while the non-neurotoxic proteasome inhibitor carfilzomib has no effect on microtubules at antineoplastic concentrations. 18 Further, bortezomib has been linked to delta 2 tubulin accumulation, altering microtubule stability and dynamics with consequent axonopathy and altered mitochondria motility. 19 Notably, neurographic in vivo molecular imaging demonstrated axonal transport alterations following platinum chemotherapy.…”

The microtubule cytoskeleton: An old validated target for novel therapeutic drugs

“…It has now been demonstrated that bortezomib, a widely used 26S proteasomal subunit inhibitor, with anti-tumor activity in hematological malignancies, also has a stabilizing effect on MTs ( Staff et al, 2013 ; Meregalli et al, 2014 ; Malacrida et al, 2021 ). This effect can account for bortezomib anti-cancer activity.…”

MV1035 Overcomes Temozolomide Resistance in Patient-Derived Glioblastoma Stem Cell Lines

“…It may be expected that the presence of MV1035 makes it difficult for the methylated nucleobase within DNA to reach the right site for the enzymatic reaction ( Figure 2 C,D). Noteworthy, the PBS for MV1035 within ALKBH2 was identified despite being partially closed and apparently inaccessible to the ligand (see Supplementary Figure S1 and Supplementary Table S2 ) thanks to SPILLO-PBSS’s ability to take into account protein flexibility [ 16 , 28 , 29 ].…”