Diverse microtubule-destabilizing drugs induce equivalent molecular pathway responses in endothelial cells

Drugs that modulate microtubule (MT) dynamics are well-characterized at the molecular level, yet the mechanisms linking these molecular effects to their distinct clinical outcomes remain unclear. Several MT-destabilizing drugs, including vinblastine, combretastatin A4, and plinabulin, are widely used, or are under evaluation for cancer treatment. Although all three depolymerize MTs, they do so through distinct biochemical mechanisms. Furthermore, their clinical profiles and therapeutic uses differ considerably. To investigate whether differential modulation of molecular pathways might account for clinical differences, we compared gene expression and signaling pathway responses in human pulmonary microvascular endothelial cells (HPMECs), alongside the MT-stabilizing drug docetaxel and the pro-inflammatory cytokine TNF-. RNA-sequencing and phosphoproteomics revealed that all three MT destabilizers triggered equivalent molecular responses. The substantial changes in gene expression caused by MT destabilization were completely dependent on Rho family GTPase activation. These findings suggest that the distinct clinical profiles of the destabilizing drugs depend on differences in pharmacokinetics (PK) and tissue distribution rather than molecular actions. The washout rate of the three drugs differed, which likely translates to PK differences. Our data provide insights into how MT destabilization triggers signaling changes, potentially explaining how these drugs induce cell cycle re-entry in quiescent cells and how plinabulin ameliorates chemotherapy-induced neutropenia. Significance StatementMicrotubule (MT)-destabilizing drugs, despite their potential for toxicity, are used to treat a surprising range of diseases, including cancers, inflammatory disorders, and parasitic infections. To investigate how drugs with apparently similar actions on MTs achieve diverse clinical effects, we compared the molecular pathways that are activated by three drugs with different clinical profiles, vinblastine, combretastatin A4, and plinabulin. All three elicited similar gene expression responses via Rho GTPase activation. This finding suggests that their distinct clinical effects are not caused by different effects on MTs, but rather by differences in drug transport, pharmacokinetics or tubulin isotype affinity. Our findings provide insights into how plinabulin might protect the bone marrow and may help medicinal chemists design MT drugs for new applications.