Abstract 5014: Neutrophils protect B-cell lymphomas against chemotherapy via cell-cell interactions mediated by CD44 and ICAM1 receptors
Authors: Hirz Taghreed , Esmenjaud Justine , Evesque Anne , Mathe-Poloni Doriane , Dumontet Charles 
Published: August 2015

Abstract
Background: Neutrophils are innate immune cells that play an established role in the killing of microorganisms. While much less studied than adaptive immune cells, neutrophils are detected in different solid tumors. Current evidence suggests that neutrophils show high functional plasticity and can display either protumor or antitumor activity. Given the abundance of significant portion of tumor-associated neutrophils in many cancer models and due to lack of information about the role of neutrophils in lymphoma, we investigated the impact of neutrophils on the sensitivity of B cell lymphomas to chemotherapy.
Methods: Freshly isolated human neutrophils were cocultured with different types of human B cell non Hodgkin lymphomas (NHL) in the presence of various chemotherapies (vincristine, doxorubicin, cisplatin, bortezomib and mafosfamide). Chemotherapeutic effect on cell proliferation and cytotoxicity was assessed by flow cytometry using CFSE and DAPI assays, respectively. Expression profiling of cells exposed to neutrophils was performed by Illumina cDNA array. Blocking antibodies were added to the coculture system. In vivo, RL cells were co-injected with neutrophils subcutaneously into SCID CB17 mice and treated with vincristine. Ex vivo, peripheral blood was obtained from chronic lymphocytic leukemia (CLL) patients. CLL B cells were cocultured with autologous neutrophils then exposed to vincristine, ibrutinib or idelalisib. CLL cells were analyzed for their content in Bcl2, BclXL and Mcl1.
Results: We found that freshly isolated human neutrophils protect NHL cells against the chemotherapeutic cytotoxicity. Neutrophils protective role was not due to sequestration of chemotherapy. This effect was not due to soluble factors produced by neutrophils and required direct cell-cell interactions between neutrophils and NHL cells. Expression profiling of RL cells in the presence of neutrophils showed enhanced expression of CD44. Blocking antibodies against CD44 and ICAM1 receptors inhibit neutrophil-mediated protection of RL cells against chemotherapy in vitro. In vivo, freshly isolated human neutrophils co-injected with tumor cells reduced sensitivity of RL cells to vincristine resulting in enhanced tumor growth. Similarly autologous neutrophils protected fresh CLL cells from the cytotoxic effect of various agents. Exposure of CLL cells to neutrophils increased the content of Bcl2 and Mcl1 with no effect on BclXL.
Conclusion: Neutrophils protect B cell lymphomas against chemotherapy in vitro and in vivo. This protective role is due to cell-cell interactions mediated by CD44 and ICAM1 receptors. Our results also suggest that neutrophils enhance CLL survival by inducing the expression of anti apoptotic proteins Bcl2 and Mcl1. Our findings underline the importance of neutrophils in tumor growth or chemoresistance and may contribute to therapeutic strategies to inhibit their protective effect.
Citation Format: Taghreed Hirz, Justine Esmenjaud, Anne Evesque, Doriane Mathe-Poloni, Charles Dumontet. Neutrophils protect B-cell lymphomas against chemotherapy via cell-cell interactions mediated by CD44 and ICAM1 receptors. [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 5014. doi:10.1158/1538-7445.AM2015-5014