Unlocking Tumor Suppression: The Potency of EZN-4482 in Targeting GLI2 and Enhancing Cancer Survival

The Hedgehog signaling pathway plays a significant role in the development of various human cancers and cancer stem cells. The pathway is activated when Hh ligands relieve PTCH1's inhibition of Smoothened (SMO), leading to the activation of transcription factors GLI2 and GLI3, which in turn induce the transcription of their target genes. These genes are implicated in the activation of the Hh pathway and are often amplified or overexpressed in malignancies. Targeting GLI1 and GLI2 with RNA antagonists, such as small interfering RNA (siRNA) and antisense molecules, is a potential therapeutic strategy for cancer treatment.

In this study, the biological activities of two LNA-based GLI2 mRNA antagonists, EZN-4482 and 4496, were explored. The antagonists' ability to reduce mRNA and cell growth was assessed in vitro using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and MTS assays. In vivo, the antagonists' impact on GLI2 mRNA levels in tumors was evaluated after intravenous administration in mice bearing tumors on their flanks. The effects of the antagonists on tumor growth and mouse survival were also examined in PC3 prostate tumors and A549 lung carcinoma cells that had metastasized to the liver.

Both antagonists effectively reduced GLI2 mRNA levels in tumor cells, leading to caspase activation and growth inhibition. Notably, the antagonists could down-regulate GLI2 mRNA and inhibit the growth of multiple cell lines without the need for a transfection reagent, indicating a specific effect. In mice, EZN-4482 reduced GLI2 mRNA in PC3 prostate tumors and also inhibited GLI1/2 and PTCH1 in the same tumors. The antagonist showed moderate tumor growth inhibition in the PC3 xenograft model and prolonged the survival of mice with liver metastasis from A549 cells.

The study concludes that GLI2 antagonists can potently and specifically inhibit GLI2 mRNA expression and tumor growth in two different tumor models. The efficacy of these antagonists may be due to the inhibition of mRNA levels of GLI1/2 and PTCH1 in mouse stromal cells. While small molecule inhibitors of SMO are being clinically evaluated, they are limited to tumors with pathway activation upstream of GLIs or those resistant to such inhibitors. Therefore, a GLI2 RNA antagonist could be a promising therapy for a wide range of cancers, including those that do not respond to SMO inhibitor therapy.