Abstract 1735: Cathepsin B knocked down in pancreatic cancer cell lines fail to establish tumor in nude mice and influences the differential expression of circular RNA
Authors: Gnanamony Manu , Ge Liang , Chatterjee Tulika , Gondi Christopher S. 
Published: August 2019

Abstract
Most malignant tumors show increased transcriptional activation of cathepsin B. Over expression of cathepsin B has been associated with different malignancies and this has made it an attractive pharmacological target. Tumor progression can be defined in several steps with respect to proteases. The first step requires that surrounding tissue be cleared to create a pathway for growth by modification and degradation of the extracellular matrix and basement membrane. Cathepsin B is one of the cathepsins that has been directly linked to extracellular matrix degradation. The second is a proteolytic cascade where activation of matrix metalloproteinases and urokinase plasminogen activator (uPA), results in further tissue invasion, this activation is known to be mediated by Cathepsin B. The last is cleavage of E-cadherin at adherin junctions, detaching cells to enter circulation and migrate. Cathepsin B plays a central role in these processes.
Methods: In this study, we used two pancreatic cancer cell lines PANC-1 and MIA PaCa-2 that show differential sensitivity to gemcitabine. We knocked down the expression of cathepsin B in both PANC-1 and MIA PaCa-2 cells using CrisperCas9. We determined the tumorogenic potential of these down regulated cells and determined changes in gemcitabine sensitivity. Further, we determined the global expression profiles of circular RNA to predict the post-transcriptional regulation of associated microRNAs associated with chemo-sensitivity.
Results: From the tumorogenic studies, we observed that both PANC-1 and MIA PaCa-2 cells downregulated for Cathepsin B failed to develop tumors in nude mice subcutaneous tumor models. Further, from the gemcitabine sensitivity studies using the MTT assay we observed that Cathepsin B down regulation reduced IC50 in both PANC and MIA PaCa-2 by at least 25%. Global analysis of circular RNA expression showed that Cathepsin B downregulated PANC-1 cells showed a 4.2 fold increase in the expression of hsa_circRNA_081069 and a 3.8 fold decrease in the expression of hsa_circRNA_104169. In case of MIA PaCa-2 cells downregulated for Cathepsin B, we observed that hsa_circRNA_042488 was upregulated by 15.9 fold and hsa_circRNA_101692 was decreased by 20.5 fold.
Conclusions: From our observations, we conclude that Cathepsin B expression is necessary for (1) tumor establishment and development; (2) gemcitabine resistance and (3) modulation of circular RNA expression that regulate oncogenic and metabolic pathways necessary for tumorigenesis.
Citation Format: Manu Gnanamony, Liang Ge, Tulika Chatterjee, Christopher S. Gondi. Cathepsin B knocked down in pancreatic cancer cell lines fail to establish tumor in nude mice and influences the differential expression of circular RNA [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 1735.