LCN2 and colon cancer — Have we hit the jackpot.

Abstract

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.