The anterior gradient homologue 2 (AGR2) co-localises with the glucose-regulated protein 78 (GRP78) in cancer stem cells, and is critical for the survival and drug resistance of recurrent glioblastoma: in situ and in vitro analyses

Abstract

Background Glioblastomas (GBs) are characterised as one of the most aggressive primary central nervous system tumours (CNSTs). Single-cell sequencing analysis identified the presence of a highly heterogeneous population of cancer stem cells (CSCs). The proteins anterior gradient homologue 2 (AGR2) and glucose-regulated protein 78 (GRP78) are known to play critical roles in regulating unfolded protein response (UPR) machinery. The UPR machinery influences cell survival, migration, invasion and drug resistance. Hence, we investigated the role of AGR2 in drug-resistant recurrent glioblastoma cells. Methods Immunofluorescence, biological assessments and whole exome sequencing analyses were completed under in situ and in vitro conditions. Cells were treated with CNSTs clinical/preclinical drugs taxol, cisplatin, irinotecan, MCK8866, etoposide, and temozolomide, then resistant cells were analysed for the expression of AGR2. AGR2 was repressed using single and double siRNA transfections and combined with either temozolomide or irinotecan. Results Genomic and biological characterisations of the AGR2-expressed Jed66_GB and Jed41_GB recurrent glioblastoma tissues and cell lines showed features consistent with glioblastoma. Immunofluorescence data indicated that AGR2 co-localised with the UPR marker GRP78 in both the tissue and their corresponding primary cell lines. AGR2 and GRP78 were highly expressed in glioblastoma CSCs. Following treatment with the aforementioned drugs, all drug-surviving cells showed high expression of AGR2. Prolonged siRNA repression of a particular region in AGR2 exon 2 reduced AGR2 protein expression and led to lower cell densities in both cell lines. Co-treatments using AGR2 exon 2B siRNA in conjunction with temozolomide or irinotecan had partially synergistic effects. The slight reduction of AGR2 expression increased nuclear Caspase-3 activation in both cell lines and caused multinucleation in the Jed66_GB cell line. Conclusions AGR2 is highly expressed in UPR-active CSCs and drug-resistant GB cells, and its repression leads to apoptosis, via multiple pathways.

TGM2, HMGA2, FXYD3, and LGALS4 genes as biomarkers in acquired oxaliplatin resistance of human colorectal cancer: A systems biology approach

“…AHNAK serves as a p53 cofactor among the top down-regulated hub genes [ 99 ] and its overexpression decreases chemoresistance in breast and lung cancer [ 100 ]. Conflicting results are reported throughout the literature regarding the expression of some of uncommon hub genes such as OXCT1 [ 101 , 102 ], AGR2 [ 103 , 104 ], MUC1 [ 105 , 106 ], GRP78 [ 107 , 108 ], and TRIM54 [ 83 ] in drug-resistant cancer cells. The aforementioned results confirm the hypothesis that resistance index affects gene expression and common hub genes which were independent of OX-RI values exhibit more reliable results.…”

Endoplasmic reticulum stress and quality control in relation to cisplatin resistance in tumor cells

“…Hsp27 activation can suppress cell death in HCC cells by promoting autophagy ( Chen et al, 2011 ). Similarly, GRP78-mediated UPR reduces cisplatin-induced apoptosis in hypopharyngeal carcinoma ( Pi et al, 2014 ) and glioblastomas ( Hussein et al, 2022 ), promoting tumor cell survival. In pancreatic cancer, UPR mitigates cisplatin-induced cell death through ER dilation and intracellular Ca 2+ modulation, which Bortezomib can inhibit ( Nawrocki et al, 2005 ).…”

AGR2-mediated unconventional secretion of 14-3-3ε and α-actinin-4, responsive to ER stress and autophagy, drives chemotaxis in canine mammary tumor cells

“…Overexpression of AGR2 is commonly observed in various human adenocarcinomas, where it promotes tumor growth and metastasis, correlating with a poor prognosis [28][29][30]. Moreover, upregulation of AGR2 expression is seen in chemotherapeutics-resistant cancer cells, further contributing to drug resistance [31][32][33][34].…”