Abstract 207P
Background
Bioactive derivatives of cholesterol have been demonstrated to regulate immune cell function and migration, the tumor microenvironment (TME), and consequently tumor progression. Ch25h, a key enzyme involved in cholesterol metabolism and 25- hydroxycholesterol(25-HC) production, was positively correlated with overall survival in melanoma, breast cancer and colon cancer patients. High Ch25h expression is correlated with good response to immunotherapy in melanoma and glioblastoma patients. Expression levels of Ch25h in human tumors are also positively correlated with lymphatic signature. However, the function and mechanism of lymphatic vessel expressed Ch25h in tumor microenvironment remain unknown.
Methods
Mouse B16-OVA-VEGFC melanoma, MC38 colon cancer, and E0771 breast cancer models are used on Ch25h conditional knockout mice with C57/bl6 and immunodeficient background to study the impact of lymphatic endothelial cells (LECs) derived oxysterol on anti-tumor immunity. CpG-based tumor vaccination and activated CD8 T cell adoptive transfer are used to study the impact of LEC-derived Ch25h under immunotherapy.
Results
Our RNA sequencing data on lymphangiogenic murine melanoma showed an increase of Ch25h expression in tumor-associated LECs. Using conditional-knockout mice, we found that Ch25h deficiency in LECs leads to a significant decrease of tumor interstitial 25HC, as well as increased tumor aggressiveness and suppressed immune cell infiltration. Specific deletion of Ch25h in LECs impedes intra-tumoral effector T cell accumulation upon T cell adoptive transfer. Further, mice with LEC-specific Ch25h deficiency show earlier relapse in tumor vaccination and T cell adoptive transfer experiments, whereas littermates maintain the control of tumor growth. Mechanistically, we found that anti-CSFR1 administration upon tumor vaccination promotes tumor relapse in control groups, whereas in contrast, introducing 25-HC intratumorally can prevent tumor relapse in LEC-Ch25h conditional-knockout mice.
Conclusions
Our results suggest a novel active way of lymphatic vessels participating in anti-tumor immunity by regulating anti-tumor immune response through oxysterol.
Legal entity responsible for the study
The authors.
Funding
Swiss Cancer League.
Disclosure
All authors have declared no conflicts of interest.