Background JAK/STAT signaling, regulated by SOCS family proteins, plays a role in the progression of the inflammation, growth and metastasis of pancreatic adenocarcinoma. SOCS3 suppresses JAK kinase activity and degrades the activated cytokine receptor complex, and its loss contributes to pancreatic cancer development. We have developed advanced macromolecule transduction domains (aMTDs) to deliver recombinant proteins into to cells and tissues. In principle, aMTD enabled SOCS3 could provide an effective treatment for pancreatic tumors that depends on JAK/STAT signaling for growth or survival. Objective The present study utilized aMTD sequences to develop improved cell-permeable (iCP-) SOCS3 as a protein-based biotherapeutic against pancreatic cancer. Method Improved cell-permeable SOCS3 proteins, with and without a 12-amino acid aMTD sequence, were expressed at high yields in E. coli. The proteins also contained a solubilization domain (SD) to enhance the solubility of the recombinant proteins in physiological buffers. Results The iCP-SOCS3 exhibited high solubility, cell-/tissue-permeability and biological activity in pancreatic cancer cell lines (BxPC3, HPAC and PANC-1) with decreased endogenous SOCS3 levels, hyperactived JAK/STAT signaling and hypermethylated socs3 promoter region. The iCP-SOCS3 suppressed cancer-associated phenotypes (i.e., up to 90% inhibition of cell viability, 52% induction of apoptosis, 14.8% inhibition of cell cycle progression, 54% inhibition of migration and 61.5% inhibition of invasion) in pancreatic cancer cells dependent on elevated JAK/STAT signaling, whereas, these effects were not observed in non-cancer cells (H6c7, pancreatic duct epithelial cell) or with proteins lacking the aMTD sequence. In contrast, gemcitabine, a conventional pancreatic cancer therapeutic, showed undesirable cytotoxic effects including decreased cell viability and induced apoptosis in non-cancer cells. Furthermore, iCP-SOCS3 (30 mg/kg) induced tumor regression (-168% at day 18) in PANC-1 CDX model. In BxPC-3 orthotopic CDX model, iCP-SOCS3 suppressed tumor growth by 98% which was significantly higher compared to the suppressed tumor growth induced by gemcitabine (77%). Correlating to the tumor suppression, iCP-SOCS3 significantly decreased the secretion of TNF-α and the expression of p-STAT1, p-STAT3 and VEGF in tumor tissues. Conclusion These results provide further evidence that SOCS3 can function as a tumor suppressor and intracellular delivery of SOCS3 with iCP-SOCS3 may provide a novel protein therapy against pancreatic cancer.
Citation Format: Kuysook Lee, Seulmee Shin, Yunseo Hwang, Youngsil Choi, Daewoong Jo. Intracellular delivery of SOCS3 suppresses pancreatic cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-007.