Abstract A009: Plinabulin, a novel tubulin targeting agent, collapses the tumor microtube network in primary and recurrent patient derived glioblastoma cell lines to inhibit neurosphere invasion and survival
Authors: Eisenmann Kathryn M. , Lloyd Kenneth , Pettee Krista M. , Becker Kathryn M. , Schroeder Jason L. , Reinard Kevin , Tonra James R. , Mohanlol Ramon , Huang Lan 
Published: March 2024

Abstract
Glioblastoma multiforme (GBM) is the most common adult primary brain malignancy. Aggressive, diffuse invasion is regulated by a dynamic cytoskeleton and significantly contributes to poor survival. Intraparenchymal tumor cell dissemination prevents complete surgical resection and compromises essential brain functions. Invasive cells are inherently less sensitive to traditional cytotoxic therapies. Recent investigation into targeted therapies has failed to address invasion/cytoskeleton based GBM therapy resistance. Furthermore, established GBM cell line modeling in 2 or 3 dimensions (3D) does not capture the genetic diversity or clinical relevance of patient derived primary (1') GBM cell lines, which may uncover/predict differential responses in tumors to novel therapies. Cytoskeleton remodeling and cell invasion in patient-derived primary GBM cells generates unique structures called tumor microtubes (TMs) not seen in established, cultured GBM cell lines. TMs are ultralong, pro-invasive, tubulin-enriched protrusions that promote chemo- and radioresistance in GBM patient derived primary cells. Using our extensive GBM cell line biobank derived from 1' and/or therapy resistant recurrent (2') tumors, we investigated the effects of a novel drug targeting the microtubule cytoskeleton. Plinabulin is a tubulin targeting agent that crosses the blood brain barrier and demonstrated anticancer efficacy in Phase III trial patients with non-small cell lung carcinoma. Plinabulin also has antiproliferative properties in 2D GBM cells. Here, we evaluate the efficacy of plinabulin treatment upon 3D neurosphere viability and invasion in 5 GBM 1' and 2' recurrent patient derived cell lines. Within 24h of matrigel embedding, 3D GBM patient neurospheres generate robust pro-invasive TMs. Plinabulin treatment (10-30 nM) at embedding followed by drug washout after 24h eliminated existing TMs and inhibited single cell invasion (80% relative to controls) in both 1' and 2' GBM patient neurospheres. Cell survival was significantly reduced in plinabulin treated neurospheres (30 nM). Plinabulin efficacy was evaluated in a clinically relevant therapeutic ITR model: GBM patient neurospheres invaded (I) for 48h to establish TM networks; were treated (T) with 1-50 nM plinabulin for 24h prior to drug washout; and recovered (R) for 96h. In 1', 2', or matched 1' and 2' cell line pairs from the same patient, 10-40 nM plinabulin sustained invasion inhibition (&gt;90%) through 96h post washout and completely blocked TM extension relative to controls, consistent with established clinical concentrations of plinabulin. This study reveals plinabulin as a potent GBM therapeutic targeting pro-invasion TM networks and survival in 1' and therapy resistant 2' GBM patient cell lines.
Citation Format: Kathryn M. Eisenmann, Kenneth Lloyd, Krista M. Pettee, Kathryn M. Becker, Jason L. Schroeder, Kevin Reinard, James R. Tonra, Ramon Mohanlol, Lan Huang. Plinabulin, a novel tubulin targeting agent, collapses the tumor microtube network in primary and recurrent patient derived glioblastoma cell lines to inhibit neurosphere invasion and survival [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A009.