Abstract 456: Immune-suppressive myeloid cells are induced during disease progression in patients with advanced pancreatic adenocarcinoma.

Abstract

Abstract Background: Pancreatic cancers produce multiple immune-suppressive factors that can be measured in peripheral blood. Elevated levels of myeloid derived suppressor cells (MDSC) induced by tumor derived factors are associated with inhibition of immune responses in gastrointestinal malignancies (Mundy-Bosse, et al., CII, 2011). We hypothesized that levels of MDSC and pro-MDSC cytokines would be elevated in pancreatic adenocarcinoma patients with progressive disease. Methods: Plasma and immune cells from peripheral blood were obtained from 30 pancreatic adenocarcinoma patients. Group A consisted of 15 patients undergoing chemotherapy (11 stage III/IV, 4 stage II). Group B consisted of 15 chemonaive patients (10 stage III/IV, 5 stage II) and group C consisted of 9 normal patients. The nonparametric Wilcoxon test was used to compare the cytokines in the plasma between the various groups (A/B vs C, A vs B). The Bonferroni method was used to adjust for data obtained for 27 cytokines via BioPlex assay. Pathway analysis on cytokine profiles obtained from the BioPlex analysis was performed using IPA. A S100A9 ELISA was performed on chemonaive patients and the Wilcoxon test was used to compare levels between patients with different cancer stages. MDSC (HLADRneg/low, CD33+, CD11b+, CD15+/− and CD14+/−) were phenotyped via flow cytometry. Results: BioPlex analysis was performed on all subjects (Groups A, B and C). Increases in the levels of pro-MDSC cytokines were observed for A/B vs C (IL4 (p=0.005), IL5 (p=0.046), IL10 (p=0.046), GCSF (p=0.027). Increases were also observed in levels of pro-inflammatory cytokines (e.g. RANTES p<0.0027) and angiogenic cytokines (e.g. VEGF p=0.0027 and IL8 p<0.0027) when comparing A/B vs C. When comparing treated vs untreated patients, statistically increases in the level of cytokine IL6 (p=0.011) were observed for group A. Pathway analysis predicted the pro-MDSC protein S100A9 would increase with cancer stage. Levels of S100A9 were greater in plasma of newly diagnosed surgically unresectable patients as compared to surgically resectable patients by a factor of 2.4 fold (p= 0.025). To date, 11 patients who have undergone chemotherapy have been phenotyped and the PD patients (n=7) had statistically higher HLADRneg/low/CD33+ cells (9.1 ± 6.1 %) than SD (n=4) patients (1.4 ± 0.6%), with p=0.01 based on the Mann-Whitney test. MDSC and T cells isolated from a patient with 19.3% HLADRneg/low/CD33+ cells in peripheral blood were co-cultured and demonstrated that MDSC decreases T cell proliferation and responsiveness to interferon stimulation by 85%. Conclusions: Levels of pro-MDSC cytokines are increased in the circulation of pancreatic adenocarcinoma patients. MDSC chemotaxic factors such as S100A9 increase with stage. This study suggests that MDSC in peripheral blood may be a predictive biomarker of chemotherapy failure in pancreatic cancer patients. Citation Format: Joseph Markowitz, Bonnie K. Paul, Taylor R. Brooks, Lai Wei, Jeff Pan, Katherine L. Martin, Eric Luedke, Bethany L. Mundy-Bosse, Gregory B. Lesinski, Tanios Bekaii-Saab, William E. Carson. Immune-suppressive myeloid cells are induced during disease progression in patients with advanced pancreatic adenocarcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 456. doi:10.1158/1538-7445.AM2013-456