David Cachia

Abstract 1: Galectins in glioblastoma: opportunities for combined therapy

Background: Despite aggressive treatment, including surgical resection, radiation and chemotherapy, over 90% of glioblastoma (GB) patients experience tumor recurrence. This may be due to high migratory potential, angiogenesis, molecular heterogeneity and a strong immunosuppressive environment. GB expresses high levels of carbohydrate-binding galectin proteins and histone deacetylase (HDAC) activity. The aim of this study was: 1) identify the differential expressions of galectin 1-15 protein levels in human GB patient samples as compared to normal tissue (obtained from Institutional Tissue Bank) and (2) modulate the galectin functions with and without a HDAC inhibitor (DATS: Dially Triisulfide and SAHA: Suberoylanilide Hydroxamic Acid ) or bevacizumab in in vitro GB models. Methods: The effects of TMZ, ionizing radiation, or combined chemoradiation on galectin protein secretion and expression were assessed in human GB cells and human umbilical vein endothelial cells (HUVECs). Results: We found increased galectin-1 protein expression in human GB tissue. We also observed that HUVEC co-culture with GB cells increased galectin-1 protein expression by 14 - 20% following bevacizumab, and conferred a bevacizumab protective benefit to GB cells. Our in vitro models promisingly demonstrated that 72 hr treatments with 25 µM of galectin 1 inhibitor + HDAC inhibitor induce antitumor activity in GB cells. Western blot and activities assay results also demonstrated that combination blockade of HDAC activity and galectin-1 augmented apoptosis in GB cells, which mechanistically involves activation of caspase-3 and inhibition of anti-apoptotic protein (survivin, p-Akt, and Mcl-1 expression). Conclusion: Our in vitro culture results suggest possible benefit in combining a galectin inhibitor with an HDAC inhibitor in GB. Further studies in different animal models are warranted. Citation Format: David Cachia, Arindam Rano Chatterjee, William Alexander Vandergrift, Sunil J. Patel, Gabriel A. Rabinovich, Arabinda Das. Galectins in glioblastoma: opportunities for combined therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1. doi:10.1158/1538-7445.AM2017-1

Synergistic Effects of Crizotinib and Temozolomide in Experimental FIG-ROS1 Fusion-Positive Glioblastoma

Glioblastoma (GB) is the most common malignant brain tumor. Drug resistance frequently develops in these tumors during chemotherapy. Therefore, predicting drug response in these patients remains a major challenge in the clinic. Thus, to improve the clinical outcome, more effective and tolerable combination treatment strategies are needed. Robust experimental evidence has shown that the main reason for failure of treatments is signal redundancy due to coactivation of several functionally linked receptor tyrosine kinases (RTKs), including anaplastic lymphoma kinase (ALK), c-Met (hepatocyte growth factor receptor), and oncogenic c-ros oncogene1 (ROS1: RTK class orphan) fusion kinase FIG (fused in GB)-ROS1. As such, these could be attractive targets for GB therapy. The study subjects consisted of 19 patients who underwent neurosurgical resection of GB tissues. Our in vitro and ex vivo models promisingly demonstrated that treatments with crizotinib (PF-02341066: dual ALK/c-Met inhibitor) and temozolomide in combination induced synergistic antitumor activity on FIG-ROS1-positive GB cells. Our results also showed that ex vivo FIG-ROS1+ slices (obtained from GB patients) when cultured were able to preserve tissue architecture, cell viability, and global gene-expression profiles for up to 14 days. Both in vitro and ex vivo studies indicated that combination blockade of FIG, p-ROS1, p-ALK, and p-Met augmented apoptosis, which mechanistically involves activation of Bim and inhibition of survivin, p-Akt, and Mcl-1 expression. However, it is important to note that we did not see any significant synergistic effect of crizotinib and temozolomide on FIG-ROS1-negative GB cells. Thus, these ex vivo culture results will have a significant impact on patient selection for clinical trials and in predicting response to crizotinib and temozolomide therapy. Further studies in different animal models of FIG-ROS1-positive GB cells are warranted to determine useful therapies for the management of human GBs.