Abstract 2103: NETs promote tumor resistance to anthracyclines

Abstract

Multiple Myeloma (MM) is an incurable blood cancer characterized by the clonal proliferation of plasma cells that accumulate in the bone marrow (BM). Resistance to chemotherapy represents one of the main challenges in the treatment of this disease. We have previously shown that neutrophils, one of the major cellular populations in the BM, protect MM cells from chemotherapies including anthracyclines; however, the mechanisms of this effect remain unknown. Thus, we set out to investigate the mechanisms by which neutrophils reduce sensitivity of tumor cells to anthracyclines. Neutrophil extracellular traps (NETs) are structures composed of chromatin and protein formed by neutrophils that are a part of an innate immune mechanism of binding and killing pathogens. Recently, NETs have been shown to form in cancer patients as well as tumor-bearing animals and have been implicated in solid tumor progression; however, their role in hematological malignancies remain poorly understood. Utilizing an in vitro culture system, we demonstrated that MM cells were able to induce NET formation by BM neutrophils. Interestingly, neutrophils isolated from the BM of patients with MM have a significantly higher ability to produce NETs in response to tumor cells as compared to BM neutrophils from donors. NET formation was accompanied by an increase in the level of extracellular DNA. Using imaging flow cytometry and confocal microscopy we demonstrated that extracellular DNA is internalized by tumor cells and localizes to the cytoplasm. This internalized DNA was able to bind to doxorubicin and other anthracyclines thereby reducing their cytotoxic effects. Significantly increased cell-free DNA levels were detected in BM aspirates from MM patients as well as in tumor-bearing mice. Targeting the extracellular DNA in vivo using the clinically available DNase, Pulmozyme, restored the sensitivity of tumor cells to doxorubicin resulting in prolonged survival of tumor-bearing animals. Here, we have identified a novel mechanism of resistance to anthracyclines that is mediated by neutrophils in the tumor microenvironment and provided evidence to support the premise that targeting this mechanism would be of significant benefit in the treatment of MM. Citation Format: Cindy Lin, Sarah E. Herlihy, Marina Li, Hui Deng, Luca Bernabei, Dmitry I. Gabrilovich, Dan T. Vogl, Yulia Nefedova. NETs promote tumor resistance to anthracyclines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2103.

Targeting neutrophils: Mechanism and advances in cancer therapy

“…Research on resistance has never failed to attract scholars’ attention. The presence of NETs is partly responsible for the poor prognosis after treatment, as the mechanisms through which NETs coat tumour cells and promote resistance to chemotherapy, immunotherapy and radiotherapy have already been described 9,52–54 . Under certain chemical conditions, tumour cells secrete interleukin‐1β (IL‐1β), which subsequently induces the generation of NETs.…”

NETosis as an oncologic therapeutic target: a mini review

“…NETosis has been linked to chemotherapy resistance in cancers. In a mouse model of multiple myeloma, neutrophils promoted chemoresistance to doxorubicin and melphalan through soluble factors released in the tumor microenvironment during NETosis ( 47 , 48 ). MMP9, released in NETs, are a key driver of angiogenesis in cancers and corelates with poorer sensitivity to oxaliplatin in gastric cancer.…”

“…DNAse I is another potential agent to inhibit NETosis. In a mouse model of multiple myeloma, pulmozyme, a DNAse targeting extracellular DNA in NETosis, can reverse tumor resistance to doxycycline ( 48 ). DNAse I has successfully block NETs in lung cancer, with subsequent reduction in number of metastases in murine models ( 40 ).…”

Neutrophil Extracellular Traps and Cancer: Trapping Our Attention with Their Involvement in Ovarian Cancer

“…Recent studies in multiple myeloma demonstrated a TAN-dependent chemoprotection driven by soluble factors released into the TME [ 117 ]. Extending these investigations, authors showed that NETs could be internalized by neoplastic cells and detoxify drugs such as doxorubicin [ 118 ]. Moreover, they showed that the treatment with DNase restored chemosensitivity in their animal models.…”