Targeting Transgelin-2 by novel small molecule inhibitors to circumvent resistance in glioblastoma
PO-1145
Abstract
Targeting Transgelin-2 by novel small molecule inhibitors to circumvent resistance in glioblastoma
Authors: Ashok Kumar1, Priyani Rajasekera1, Valesio Becker1, Sarah Biehn2, Sasha Beyer1, Joseph McElroy3, Aline Becker1, Benjamin Johnson1, Tiantian Cui1, Anca-L. Grosu4, Steffen Lindert2, Erica Bell1, Heather Manring1, Jahar Haque1, Arnab Chakravarti1
1The Ohio State University Wexner Medical Center, Department of Radiation Oncology, Columbus, Ohio, USA; 2The Ohio State University, Department of Chemistry & Biochemistry, Columbus, Ohio, USA; 3The Ohio State University, Department of Biomedical Informatics, Columbus, Ohio, USA; 4University of Freiburg Medical Center, Radiation Oncology, Freiburg, Germany
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Purpose or Objective
Transgelin-2 is an actin-binding protein known to regulate actin cytoskeleton dynamics, thereby playing critical roles in cell proliferation, migration, invasion, and therapeutic resistance in GBM and other malignancies. Our clinical correlative studies revealed that TAGLN2 was upregulated in GBM patients with wild-type IDH1/2 compared to those with mutant IDH1/2, which was associated with worse patient outcomes suggesting that Transgelin-2 might serve as a novel biomarker and a potential therapeutic target in GBM. Accordingly, we hypothesize that targeting Transgelin-2 by small molecule inhibitors (SMIs) may improve patient outcome by circumventing therapeutic resistance in GBM. To this end, this study aims to identify novel SMIs of Transgelin-2 and demonstrate the potential of these inhibitors in overcoming treatment resistance in GBM.
Material and Methods
RNAi-mediated TAGLN2 knockdown (KD) approach was employed to assess the functions of Transgelin-2 in PDX GBM cell lines. Computational screening of NCI libraries was employed to identify SMIs that were able to bind to Transgelin-2. SMIs were screened for their ability to permeate BBB, using SwissADME webtool. A series of in vitro binding/functional assays were performed to measure their potential to bind and inhibit Transgelin-2-dependent functions in GBM 08-387 and -3359 PDX cell lines. Further, the potential of these inhibitors to sensitize GBM cells towards standard TMZ and/or RT was evaluated.
Results
TAGLN2 KD significantly inhibited proliferation, survival, clonal expansion, and invasion of GBM cell lines in vitro. We also found that Transgelin-2 KD significantly increased the sensitivity of these cells to both RT and TMZ in vitro. In-silico virtual screenings identified potential SMIs of Transgelin-2. In-silico analysis predicted SMIs that permeated BBB. In vitro binding studies confirmed that select SMIs were able to bind to Transgelin-2 with high affinity and inhibit the Transgelin-2-dependent actin-polymerization. Further, these SMIs significantly inhibited the proliferation, survival, migration/invasion and clonal expansion of GBM cells. Importantly, they did not exhibit toxicity to normal human cells (Normal Human Astrocytes, Human Lung Fibroblasts) in vitro. In addition, select SMIs reduced the level of Transgelin-2 protein in a dose- and time- dependent fashion in GBM cells. Our in vitro data also suggest that these inhibitors significantly sensitized GBM cell lines towards TMZ and/or RT in a dose- and time-dependent fashion.
Conclusion
Our data suggest that Transgelin-2 contributes to the proliferation, invasion and resistance to chemo-radiation treatment of PDX cells with wt-IDH1/2 in vitro. We identified novel SMIs of Transgelin-2 and validated their potential to bind and inhibit Transgelin-2 mediated functions in PDX cell lines without detectable toxicity in normal human cells, thereby serving as potential candidates for preclinical trials.