Lipocalin 2 is a siderophore‐binding protein that regulates iron homeostasis. Lipocalin 2 expression is elevated in multiple tumor types; however, the mechanisms that drive tumor progression upon Lipocalin 2 expression remain unclear. When Lipocalin 2 is over‐expressed, it leads to resistance to 5‐fluorouracil in colon cancer cell lines in vitro and in vivo by inhibiting ferroptosis. Lipocalin 2 inhibits ferroptosis by decreasing intracellular iron levels and stimulating the expression of glutathione peroxidase4 and a component of the cysteine glutamate antiporter, xCT. The increase in xCT levels is dependent on increased levels of ETS1 in Lipocalin 2 over‐expressing cells. Inhibiting Lipocalin 2 function with a monoclonal antibody leads to a decrease in chemo‐resistance and transformation in vitro, and a decrease in tumor progression and chemo‐resistance in xenograft mouse models. Lipocalin 2 and xCT levels exhibit a positive correlation in human tumor samples suggesting that the pathway we have identified in cell lines is operative in human tumor samples. These results indicate that Lipocalin 2 is a potential therapeutic target and that the monoclonal antibody described in our study can serve as the basis for a potential therapeutic in patients who do not respond to chemotherapy.

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Invasive and metastatic tumor cells show an increase in migration and invasion, making the processes contributing to these phenotypes potential therapeutic targets. Lipocalin 2 (LCN2; also known as neutrophil gelatinase‐associated lipocalin) is a putative therapeutic target in multiple tumor types and promotes invasion and migration, although the mechanisms underlying these phenotypes are unclear. The data in this report demonstrate that LCN2 promotes actin polymerization, invasion, and migration by inhibiting actin glutathionylation. LCN2 inhibits actin glutathionylation by decreasing the levels of reactive oxygen species (ROS) and by reducing intracellular iron levels. Inhibiting LCN2 function leads to increased actin glutathionylation, decreased migration, and decreased invasion. These results suggest that LCN2 is a potential therapeutic target in invasive tumors.

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e15608 Background: Lipocalin2 (LCN2, also known as neutrophil gelatinase-associated lipocalin) is a protein that in humans is encoded by the LCN2 gene. Its abnormal expression serves critical roles in EMT transition, angiogenesis, cell migration and invasion in many cancers. We aim to assess the in vitro and in vivo effects of LCN2 as a potential chemo and radiosensitizer. Methods: Normalized RNAseq RSEM values of LCN2 were compared between normal and tumour samples from TCGA. Differences between median expression levels were assessed using Wilcoxon rank sum test. Kaplan-Meier model was used for survival analysis. Immune cell population in publicly available Colon Adenocarcinoma dataset was estimated using MCP Counter tool. Cell systems used to experimentally study the role of LCN2 in therapy resistance and tumor progression were HCT116, HT29 and DLD1. PKP3 and/or LCN2 were knocked down by shRNA. Tumor regression and therapy (5FU and radiation) sensitivity upon Anti-LCN2 treatment were demonstrated in Xenograft mouse models. Results: Analysis of 23 TCGA datasets containing gene expression data for both tumour and adjacent normal samples indicated that LCN2 levels are elevated in colon tumors. Colon cancer cell line HCT116 derived PKP3 knock-down or LCN2 over-expressing cells showed therapy resistance. A comparison of the tumor cell lines HCT116, HT29 and DLD1 show that increased LCN2 expression correlates with therapy resistance. LCN2 levels correlated with resistance to 5FU (p = 0.006) and its ability to clear ROS (p < 0.05) in vitro. Inhibiting LCN2 led to a decrease in invasion in vitro (p = 0.0005), increased sensitivity to 5FU in vitro (p = 0.001) and inhibition in tumor growth and increased sensitivity to 5FU and radiation (p = 0.005) in xenograft mouse models. On MCP counter analysis of TCGA, in Colon adenoca the normal samples show a correlation between LCN2 expression and T-cells (Pearson r = 0.45, p = 0.0028) and with the T-cell chemoattractant CXCL10 (Pearson r = 0.5, p < 0.0001). Such correlations are broken in tumour samples. Conclusions: LCN2 expression leads to chemo and radio resistance in colon cancer cell lines and xenograft mouse models. Inhibiting LCN2 function can inhibit tumor progression and sensitizes tumors to radiation and 5FU. These results suggest that LCN2 expression could be a marker that can be used to determine the choice of therapy offered to patients and that LCN2 could serve as a therapeutic target that sensitizes cells to radio and chemotherapy. LCN2 affects tumor progression and therapy sensitivity probably through T cell mediated immune pathway.

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