Cancer-secreted AGR2 induces programmed cell death in normal cells.

Elizabeth A Vitello,Alvin Y Liu,Pamela Troisch,Heather Kincaid,Sue-Ing Quek,Thomas Fuchs,Daniel J Crichton

doi:10.18632/oncotarget.9921

Abstract

Anterior Gradient 2 (AGR2) is a protein expressed in many solid tumor types including prostate, pancreatic, breast and lung. AGR2 functions as a protein disulfide isomerase in the endoplasmic reticulum. However, AGR2 is secreted by cancer cells that overexpress this molecule. Secretion of AGR2 was also found in salamander limb regeneration. Due to its ubiquity, tumor secretion of AGR2 must serve an important role in cancer, yet its molecular function is largely unknown. This study examined the effect of cancer-secreted AGR2 on normal cells. Prostate stromal cells were cultured, and tissue digestion media containing AGR2 prepared from prostate primary cancer 10-076 CP and adenocarcinoma LuCaP 70CR xenograft were added. The control were tissue digestion media containing no AGR2 prepared from benign prostate 10-076 NP and small cell carcinoma LuCaP 145.1 xenograft. In the presence of tumor-secreted AGR2, the stromal cells were found to undergo programmed cell death (PCD) characterized by formation of cellular blebs, cell shrinkage, and DNA fragmentation as seen when the stromal cells were UV irradiated or treated by a pro-apoptotic drug. PCD could be prevented with the addition of the monoclonal AGR2-neutralizing antibody P3A5. DNA microarray analysis of LuCaP 70CR media-treated vs. LuCaP 145.1 media-treated cells showed downregulation of the gene SAT1 as a major change in cells exposed to AGR2. RT-PCR analysis confirmed the array result. SAT1 encodes spermidine/spermine N1-acetyltransferase, which maintains intracellular polyamine levels. Abnormal polyamine metabolism as a result of altered SAT1 activity has an adverse effect on cells through the induction of PCD.

Highlights

In the tumor microenvironment, cancer cells interact with surrounding cells in likely different pathways
All the adenocarcinoma media tested were positive for Anterior Gradient 2 (AGR2) as shown for LuCaP 23.1, LuCaP 23.12, LuCaP 70CR, and LuCaP 35CR (CR = castration resistant)
Immunostaining of adenocarcinoma and small cell carcinoma obtained from autopsies showed the difference in AGR2 expression between these two cancer types (Figure 2)

Summary

Introduction

Cancer cells interact with surrounding cells in likely different pathways. The interaction between cancer cells and other cells could be mediated by cell-cell contact and diffusible molecules. Cell-cell contact mediates expression of prostate-specific antigen in the prostate [1]. Three major cell types can be distinguished: CD26+ luminal secretory cells, CD104+ basal epithelial cells and CD49a+ stromal cells [3]. In tumor glands only two major cell types are distinguished: CD26+ cancer epithelial cells and CD90+ cancer-associated stromal cells [4, 5]. Both CD104+ basal cells and CD49a+ normal stromal cells are missing. The cause of the disappearance of these cell types is unknown

Methods

Results

Conclusion