Abstract 4049: Neutrophil elastase induces post-transcriptional increase of surface MHC class I expression on lung cancer cells

Neutrophil infiltration and the presence of the neutrophil-associated serine protease neutrophil elastase (NE) is a poor prognosis factor for lung cancer patients. NE protein contains the nonomeric epitope for PR1, an immunogenic leukemia associated antigen recognized by a circulating population of functional cytotoxic T lymphocytes (CTL) in healthy individuals. As previously reported by our laboratory, solid tumor cells such as breast cancer cells internalize NE and cross-present PR1 in the context of the CTL ligand, MHC class I molecules, specifically HLA-A2. Internalization of NE by lung cancer cell lines has previously been reported by other groups. Therefore, we hypothesized that lung cancer cells internalize NE and cross-present PR1 on HLA-A2. A panel of lung cancer cell lines did not endogenously express proteins containing the PR1 epitope, NE and proteinase 3, at the transcript or protein level, using RT-PCR, western blot analysis and flow cytometry. Intracellular staining of NE was detected in lung cancer cell lines by flow cytometry after pulsing overnight with 10 μg/mL purified soluble NE. Subsequently, elevated surface expression of PR1:HLA-A2 complexes was determined using the PR1:HLA-A2-specific antibody generated within our laboratory (A. Sergeeva, et al., Blood 2011). Furthermore, an enhancement of HLA-A2 (antibody clone BB7.2) and pan-HLA-I (antibody clone W6/32) was observed. Through RT-PCR analysis, MHC class I genes (heavy chains HLA-A, -B, -C and the β2-microglobulin light chain) were not altered by NE exposure. Additionally, genes associated with the antigen processing machinery remained unchanged (tapasin, calnexin, calreticulin, and the Transporter associated with Antigen Processing 1 and 2). Thus exposure of lung cancer cells to NE enhances surface MHC class I molecules beyond the transcript level. MHC class I molecules serve as ligands for the T cell receptor of cytotoxic T lymphocytes, which can cause direct lysis of the target cell presenting a foreign or tumor-associated antigen. In these studies, we have detected enhanced expression of surface MHC class I molecules on lung cancer cells after exposure to NE. Thus these studies indicate that immunotherapies augmenting CTL activation could have the greatest efficacy for the poor prognosis lung cancer patients with high neutrophil infiltration or elevated plasma NE. NE contains the immunogenic PR1 epitope, and our studies have detected its cross-presentation on lung cancer cells. Therefore, anti-PR1 immunotherapies that have been developed for treatment of leukemia and lymphoma, could seamlessly be translated into lung cancer patients, and remains an area of active investigation in our laboratory. Citation Format: Haley L. Peters, Satyendra C. Tripathi, Hiro Katayama, Celine Kerros, Alex Perakis, Lisa S. St. John, Gheath Al-Atrash, Samir Hanash, Jeffrey J. Molldrem. Neutrophil elastase induces post-transcriptional increase of surface MHC class I expression on lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4049. doi:10.1158/1538-7445.AM2015-4049