Cell surface GRP78 expression on T and NK cell sub-populations of breast cancer patients.

Abstract

11561 Background: The targeting of unfolded protein response (UPR) in tumor cells has received much attention. However, data are sparse on the impact of UPR on T and NK cells. The master regulator of UPR is the glucose-regulated protein 78 (GRP78) that is expressed in some tumor cells or normal stressed cells. There are few studies concerning GRP78 expression on T and NK cells in cancer and its relationship to stress induction by chemotherapy. We aimed to reveal the effect of UPR activation on the peripheral T and NK cells of breast cancer patients by the evaluation of cell surface GRP78 expression on T and NK cells before and after neoadjuvant chemotherapy. Methods: Forty-seven patients with triple negative, ER positive/Her2 negative and Her2 positive breast cancer were included. FACS analysis of their blood specimens before and after neoadjuvant treatment was performed. For multicolor FACS analysis, anti-CD3, CD4, CD8, CD56, CD16, NKG2D, CD45RA, CD45RO, CCR7 CD62L and anti-GRP78 antibody (AF488) were added to one of the tubes. A second tube was incubated with IgG-AF488 as isotype control. Analysis of the different T and NK subpopulations that expressed cell surface GRP78 were analyzed with the Gallios Flow cytometer and Kaluza Flow Analysis Software (Beckman Coulter, Inc.). Results: The percentage of cell surface GRP78 baseline expression in CD3 (1.8±0.9), CD8 (2.9±1.5), NKG2D (4.8±2) and CD45RO/CD62L/CCR7 active T memory cells (2.1±0.5) in Her2 positive patients were significantly higher than in triple negative and ER positive/Her2 negative patients. GRP78 expression on CD56, CD16 and NKG2D cells measured after neoadjuvant treatment was significantly higher in patients with complete response (CR) compared to patients without CR. 89% of the CR patients presented with Her2+ subtype. The non-CR patients include triple negative and Her2 negative subtypes. Conclusions: GRP78 was found to be expressed in the different T and NK sub-populations. The level of expression changed with each breast cancer subtype and response to chemotherapy. These novel findings suggest that GRP78 may be used as a new predictive biomarker. It sets the stage for understanding the mechanism of UPR activation on the immune system in breast cancer.