On April 18, 2023 Genprex, Inc. ("Genprex" or the "Company") (NASDAQ: GNPX), a clinical-stage gene therapy company focused on developing life-changing therapies for patients with cancer and diabetes, reported that independent researchers recently presented preclinical data on the tumor suppressor gene, TUSC2, reporting that it functions as a novel tumor suppressor for glioblastoma (Press release, Genprex, APR 18, 2023, View Source [SID1234630239]). TUSC2 is the tumor suppressor gene that is reexpressed in tumors using REQORSA Therapy treatment, Genprex’s lead drug candidate. Genprex has no affiliation with these researchers.

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The independent researchers presented their abstract, titled, "Investigating TUSC2 for its tumor suppressive functions in glioblastoma and its role in gliomagenesis," at the 2023 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting on April 17. The abstract reports TUSC2 protein expression, but not mRNA expression, to be significantly decreased in glioblastoma as compared to normal brain. TUSC2 protein is destabilized in glioblastoma due to polyubiquitination by E3 ligase, neural precursor cell-expressed developmentally downregulated gene 4 (NEDD4), and degradation by the proteasome. The researchers determined that NEDD4 targets TUSC2 on lysine residue K71.

The researchers also reported that TUSC2 overexpression reduced colony formation and neurosphere formation and promoted apoptosis of glioblastoma cells in vitro, and suppressed tumor growth in vivo. Further, glioblastoma cells with CRISPR-mediated knockout (KO) of TUSC2 were highly aggressive in vitro and in vivo, demonstrating the role of TUSC2 as a novel tumor suppressor for glioblastoma.

In the study, researchers performed immunoprecipitation-mass spectrometry analysis to identify TUSC2-interacting proteins in both normal human astrocytes and glioblastoma cell lines. Results showed 95 and 88 TUSC2-interacting proteins in astrocytes and glioblastoma cell lines respectively, and 27 proteins were found to interact with TUSC2 in both astrocytes and glioblastoma.

"This research supports the growing body of studies evaluating TUSC2 as a target in oncology, and potentially an effective treatment, for many types of cancer," said Rodney Varner, Chairman, President and Chief Executive Officer of Genprex. "We are encouraged by the increasing number of research institutions and independent researchers producing positive data on TUSC2, which provide additional support for REQORSA and its therapeutic potential against cancers."

REQORSA Therapy is currently in development for the treatment of non-small cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). REQORSA consists of the TUSC2 gene expressing plasmid encapsulated in non-viral nanoparticles made from lipid molecules (the Company’s ONCOPREX Nanoparticle Delivery System) with a positive electrical charge. REQORSA is injected intravenously and specifically targets cancer cells, taking advantage of leaky tumor vascularity, increased tumor pinocytosis, and attraction of positively charged lipid nanoparticles to negatively charged cancer cells. REQORSA is designed to deliver the functioning TUSC2 gene to cancer cells while minimizing their uptake by normal tissue.

According to the National Brain Tumor Society, glioblastoma is one of the most complex, deadly, and treatment-resistant cancers. More than 13,000 Americans were expected to receive a glioblastoma diagnosis in 2022. Glioblastoma accounts for 49.1 percent of all primary malignant brain tumors. There have only been five drugs and one device ever approved by the U.S. Food and Drug Adminstration for the treatment of glioblastoma.

Other independent researchers and studies have found that TUSC2 therapy may benefit other types of cancer, including head and neck, breast (including triple-negative breast cancer), renal cell (kidney), thyroid, and soft tissue sarcoma, as well as NSCLC and SCLC. For more information and additional studies supporting TUSC2, please refer to our Bibliography Page.