Glutathione S-Transferase pi-1 Knockdown Reduces Pancreatic Ductal Adenocarcinoma Growth by Activating Oxidative Stress Response Pathways.

Rahul R Singh,Jiyan Mohammad,Katie M Reindl,Megan Orr

doi:10.3390/cancers12061501

Rahul R Singh, Jiyan Mohammad + Show 2 more

Open Access

https://doi.org/10.3390/cancers12061501

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Journal: Cancers	Publication Date: Jun 9, 2020
Citations: 18	License type: CC BY 4.0

Affiliation: North Dakota State University

Abstract

Glutathione S-transferase pi-1 (GSTP1) plays an important role in regulating oxidative stress by conjugating glutathione to electrophiles. GSTP1 is overexpressed in breast, colon, lung, and prostate tumors, where it contributes to tumor progression and drug resistance; however, the role of GSTP1 in pancreatic ductal adenocarcinoma (PDAC) is not well understood. Using shRNA, we knocked down GSTP1 expression in three different PDAC cell lines and determined the effect on cell proliferation, cell cycle progression, and reactive oxygen species (ROS) levels. Our results show GSTP1 knockdown reduces PDAC cell growth, prolongs the G0/G1 phase, and elevates ROS in PDAC cells. Furthermore, GSTP1 knockdown results in the increased phosphorylation of c-Jun N-terminal kinase (JNK) and c-Jun and the decreased phosphorylation of extracellular signal-regulated kinase (ERK), p65, the reduced expression of specificity protein 1 (Sp1), and the increased expression of apoptosis-promoting genes. The addition of the antioxidant glutathione restored cell viability and returned protein expression levels to those found in control cells. Collectively, these data support the working hypothesis that the loss of GSTP1 elevates oxidative stress, which alters mitogen-activated protein (MAP) kinases and NF-κB signaling, and induces apoptosis. In support of these in vitro data, nude mice bearing orthotopically implanted GSTP1-knockdown PDAC cells showed an impressive reduction in the size and weight of tumors compared to the controls. Additionally, we observed reduced levels of Ki-67 and increased expression of cleaved caspase-3 in GSTP1-knockdown tumors, suggesting GSTP1 knockdown impedes proliferation and upregulates apoptosis in PDAC cells. Together, these results indicate that GSTP1 plays a significant role in PDAC cell growth and provides support for the pursuit of GSTP1 inhibitors as therapeutic agents for PDAC.

Highlights

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortalities in the Western world and is responsible for more than 45,000 deaths per year in the US alone [1].Less than 9% of pancreatic ductal adenocarcinoma (PDAC) patients survive for five years or more after diagnosis [2]
We investigated the expression of Glutathione S-transferase pi-1 (GSTP1) in various PDAC cell lines
Our results indicate that GSTP1 inhibition impairs PDAC cell growth, suggesting that GSTP1 is a viable target for PDAC therapy

Summary

Introduction

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related mortalities in the Western world and is responsible for more than 45,000 deaths per year in the US alone [1]. Less than 9% of PDAC patients survive for five years or more after diagnosis [2]. The conventional treatment approaches, such as chemotherapy, radiation therapy, surgery, and any combination of these, have had little impact on the course of this aggressive malignancy [3,4,5,6]. New therapeutic strategies based on the unique molecular biology and physiology of pancreatic cancer are needed [7,8,9]. The constant need for cellular building blocks drives the overzealous metabolism in cancer cells [10]. Abundant byproducts such as reactive oxygen species (ROS) and reactive nitrogen

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