Background Hepatocellular carcinoma (HCC) environmental risk factors include viral infection, alcohol abuse and the metabolic syndrome. While there is evidence that boosting the activity of tumor-specific T cells might benefit patients with HCC, the underlying liver soil (cirrhosis, NASH) renders this cancer’s tumor microenvironment somewhat unique. Despite a significant therapeutic advance in the treatment of advanced HCC, ~75% of patients do not respond to immunotherapies for unclear reasons. Such a heterogeneous response highlights the need to further explore etiology- and organ-specific immunity towards improved patient stratification and the development of new combination therapies.

Materials and Methods With the objective to characterize the innate immunity landscapes of HCC, we employed droplet-based 3’ scRNA-seq of CD45⁺ panTCRαβ^- CD19^- cells, freshly isolated from tumors or adjacent non-tumoral livers of 10 HCC patients. In parallel, we used spatial transcriptomics (10x Genomics, Visium platform) to localize identified cell populations with respect to tumor and tissue features. Functional validation was carried in ex vivo co-culture experimentsusing patient-derived cells and in vivo using mouse models.

Results We present the most comprehensive atlas to date of hepatic innate immunity cells (~100,000 single cell transcriptomes). Besides describing the remarkable diversity of innate immunity cell states, our study identified and functionally characterized previously unexplored subsets of cytotoxic cells with myeloid features (myeNK) and novel myeloid-derived suppressor cell (MDSC) differentiation states. We computed signaling entropy at the single-cell level to characterize the differentiation hierarchy of these poorly annotated cells and show that myeNK cells are highly differentiated and exhibit potent lytic activity against cancer cells. Our analysis also distinguished three main MDSC lineages, a granulocytic (G-MDSC), a monocytic (M-MDSC) and an ‘immature’ subset with TAM-like features. This latter lineage presents the highest entropy and is the most immunosuppressive. Finally, we identify a discriminatory expression of the inflammatory receptor TREM-1 on MDSCs, particularly in NASH setting, and unravel this receptor as a potential therapeutic target in HCC.

Conclusions Our data support the stratification of patients according to etiology to define optimal therapeutic regimens and identify TREM1^high MDSC as deleterious effectors of HCC.

Disclosure Information J. Giraud: None. D. Chalopin: None. E. Ramel: None. M. Derieppe: None. T. Boyer: None. N. Larmonier: None. O. Adotevi: None. J. Blanc: None. L. Chiche: None. B. Le Bail: None. M. Nikolski: None. M. Saleh: None.