Microtubule Disruption Reduces Metastasis More Effectively Than Primary Tumor Growth

Background: Clinical breast cancer imaging inevitably focuses on tumor growth rather than the metastatic dissemination that is a greater challenge for patient survival. Emerging preclinical evidence indicates that chemotherapy can elevate levels of circulating tumor cells (CTCs) and increase metastatic recurrence. Targeting metastatic phenotypes of CTCs could reveal therapeutic strategies to reduce metastasis that would be overlooked by measurements of tumor growth.Methods: We investigated how the FDA-approved microtubule-depolymerizing Vinca alkaloid, Vinorelbine, affects three metastatic phenotypes of reattachment, clustering and microtentacles (McTNs). Microfluidic cell tethering technology (TetherChip) was used to measure Vinorelbine effects on McTNs and clustering while xCelligence impedance was used for reattachment assays. Bioluminescence imaging monitored tumor growth and metastasis in mice. ANGLE Parsortix and Vortex Biosciences VTX-1 were used to capture live tumor cells from blood samples for confocal microscopy to rapidly measure tumor cell responses to Vinorelbine.Results: We demonstrate that a focused (1h) Vinorelbine treatment is sufficient to inhibit reattachment, clustering and McTNs in non-adherent breast tumor cells. Quantitative analysis of treated non-adherent cells reveals that McTNs are significantly lower in number (p= 0.012) and shorter in length (p= 0.000034). Treating mice with Vinorelbine (5mg/kg) for only 24h did not significantly affect primary tumor survival. However, median metastatic tumor survival after injection of circulating tumor cells extended from 8 weeks to 30 weeks after a focused 24h treatment with Vinorelbine. Microtentacle inhibition by Vinorelbine was also detectable within 1h, using live tumor cells isolated from blood samples and analyzed with confocal microscopy for McTNs on TetherChip microfluidic surfaces. As few as 11 tumor cells were sufficient to yield 90% power to detect this 1h Vinorelbine drug response, demonstrating feasibility with the small number of tumor cells available from patient biopsies.Conclusions: This study establishes a proof-of-concept that targeted microtubule disruption can selectively inhibit metastasis and reveals that existing FDA-approved therapies could have anti-metastatic actions that are currently overlooked when focusing exclusively on tumor growth. Moreover, the anti-metastatic actions of Vinorelbine could be detected in less than one hour using microfluidic TetherChip technology, establishing a new approach for precision medicine aimed at reducing metastasis.