Abstract LB-003: Intracellular delivery of SOCS3 suppresses solid tumor progression

Abstract

Abstract Introduction Suppressor of cytokine signaling 3 (SOCS3) functions as a negative-feedback regulator of JAK/STAT signaling that suppresses JAK kinase activity and promotes degradation of the activated cytokine receptor complex. Loss of SOCS3 enhances the growth and survival of some solid tumors; therefore, methods to replenish intracellular levels of the protein may provide an effective therapy against solid tumors dependent on JAK/STAT signaling for growth or survival. Objective The present study utilized advanced macromolecule transduction domain (aMTD) sequences to develop improved cell-permeable (iCP-) SOCS3 as a protein-based biotherapeutic against solid tumors including gastric-, colorectal, lung-, breast-cancer and glioblastoma. Methods Cell-permeable SOCS3 proteins, with (iCP-SOCS3) and without (Non-CP-SOCS3) a 12-amino acid aMTD sequence or containing an earlier generation of MTD based on the signal peptide of FGF4, termed membrane-translocating motif (MTM) were expressed and purified from E. coli. The proteins also contained a solubilization domain (SD) to enhance the solubility of the recombinant proteins in physiological buffers. The therapeutic potential of iCP-SOCS3 as anti-cancer agent for solid tumors was examined both in cultured cells and in human-mouse xenograft models. Results Compared to CP-SOCS3, iCP-SOCS3 fused to aMTD exhibited higher solubility and yield (25- and 300-folds higher, respectively) that are qualified to be developed for clinical use. Moreover, it exhibited cell-/tissue-permeability along with strong biological activity that was shown by significantly suppressed IFN-γ-induced phosphorylation of STAT1 and STAT3. In vitro study conducted with various cancer cell lines demonstrated that iCP-SOCS3 significantly suppresses cancer-associated phenotypes (e.g., >80% inhibition of proliferation in lung cancer and glioblastoma, >70% induction of apoptosis in gastric cancer, >65% inhibition of migration/invasion in gastric cancer) and induces changes in biomarker expression (e.g., p21, cleavage caspase-3 in breast cancer). In addition, iCP-SOCS3 significantly suppressed the tumor growth of human solid tumor xenografts (65% inhibition in gastric-, 79% in colorectal-, 69% in lung-, 63% in breast-cancer and 78% in glioblastoma CDXs, respectively). Conclusion In conclusion, these results provide further evidence that SOCS3 can function as a tumor suppressor and intracellular delivery of SOCS3 with iCP-SOCS3 may provide novel protein therapy against solid tumors. Citation Format: Seulmee Shin. Intracellular delivery of SOCS3 suppresses solid tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-003.