Neurotensin suppresses anti-tumor immunity and is associated with poor prognosis in colorectal cancer

Introduction. Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide with substantial heterogeneity in patient outcomes. Neurotensin (NTS) and its high-affinity receptor (NTSR1) have been implicated in CRC progression, particularly in modulating tumor metabolism and immune responses. NTS secretion increases under psychological stress and high-fat intake. Given the widespread expression of NTSR1 on immune cells, we hypothesized that NTS modulates anti-tumor immunity in CRC. The purpose of our current study was to integrate clinical, in vivo , and functional evidence to delineate the impact of NTS on immune responses and patient outcomes. Methods. (i) Clinical survival: Overall survival (OS) was analyzed in a single-institution CRC cohort (University of Kentucky; n=196) stratified by tumor NTS expression, and findings were validated using KMplot (n=1,061). (ii) Transcriptomic correlation: Correlations between NTS and immunosuppressive genes (e.g., IL10, ENTPD1) were assessed utilizing publicly available datasets (GEPIA/TCGA). (iii) In vivo : Murine CRC cells (MC38) were implanted subcutaneously into NTS wild-type (NTSWT) and NTS knockout (NTSKO) mice to compare tumor growth. Tumor-infiltrating immune cells and granzyme B (GZMB) expression were quantified by immunohistochemistry (IHC) and flow cytometry. (iv) In vitro cytotoxicity: MC38 cells were co-cultured with spleen-derived CD8+ T cells from MC38-primed mice, with or without NTS treatment, and cytotoxicity was measured by LDH release. Results. (i) High NTS expression was associated with shorter OS in the institutional cohort (P<0.05) and was validated in the KMplot dataset (n=1,061; P<0.001). (ii) NTS expression showed significant positive correlations with multiple immunosuppressive genes, including IL10 (P=0.0038) and ENTPD1 (P=0.046). (iii) In vivo , NTSKO mice exhibited markedly slower tumor growth, with increased immune-cell infiltration and higher intratumoral GZMB expression. (iv) In vitro , NTS treatment significantly reduced CD8+ T-cell cytotoxicity against MC38 cells, as indicated by decreased LDH release, supporting a direct suppressive effect of NTS on effector T-cell function. Conclusions. High NTS expression identifies CRC patients with poorer prognosis and functionally suppresses anti-tumor immunity by limiting CD8+ T-cell infiltration and cytotoxic activity. Interventions that lower NTS (e.g., stress reduction and dietary optimization) may improve responses to immunotherapy and clinical outcomes. These findings provide a biological rationale for targeting the NTS/NTSR1 axis in combination with immunotherapeutic strategies.