EACR25-2129

Impact of the intratumoral bacteria on immunotherapy outcomes in hepatocellular carcinoma

U. Balaseviciute1,2, M. Rahbari3,4,5, F. Springer6, R. Pinyol1, A. Gris-Oliver1, M. Piqué-Gili1,2, J. Zucman-Rossi7,8, G. Zeller6,9, J. Llovet1,2,10, M. Heikenwälder3,5,11
1August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Translational Research in Hepatic Oncology, Barcelona, Spain
2Icahn School of Medicine at Mount Sinai, Liver Cancer Program, Division of Liver Diseases, New York, United States
3German Cancer Research Center (DKFZ), Division of Chronic Inflammation and Cancer, Heidelberg, Germany
4University of Heidelberg, Department of Surgery, University Hospital Mannheim, Medical Faculty Mannheim, Heidelberg, Germany
5The M3 Research Center, Eberhard-Karls Universität Tübingen, Tübingen, Germany
6European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
7Centre de Recherche des Cordeliers, Equipe Labellisée Ligue Nationale Contre le Cancer, Labex OncoImmunology, Paris, France
8Institut du Cancer Paris CARPEM, Department of Oncology, Hopital Européen Georges Pompidou, Paris, France
9Leiden University Center for Infectious Diseases (LUCID), Leiden University Medical Center, Leiden, Netherlands
10Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
11Eberhard Karls University, Cluster of Excellence iFIT (EXC 2180), Tübingen, Germany
Introduction:

Intratumoral bacteria are increasingly recognized as influential within the tumor microenvironment (TME). However, their role remains poorly unexplored in hepatocellular carcinoma (HCC), the third most common cause of cancer-related death worldwide. We recently reported two distinct HCC TME subtypes in patients treated with atezolizumab+bevacizumab (atezo+bev): ImmunePos, enriched with CD8+ T effector cells and CXCL10+ macrophages and associated with atezo+bev responses, and ImmuneNeg, lacking immune cell infiltration. Here, we aimed to explore the clinical relevance of tumor resident bacteria in response to atezo+bev in HCC.

Material and method:

We characterized the intratumoral microbiome in 290 HCC samples from patients treated with atezo+bev (n=247) and atezo alone (n=43) from the IMbrave150 and GO30140 clinical trials. RNAseq was used to profile the HCC resident microbiome at the genus level. Microbial content was identified by screening transcriptomic reads using the PathSeq pipeline within the Genome Analysis Toolkit. Reads aligning to the human GRCh38 genome were removed, and the remaining reads were mapped to microbial reference genomes. To filter out contaminants and adjust for batch effects, we retained only genera with a relative abundance of ≥ 10-3. The association between bacterial prevalence (relative abundance present in > 10% of samples) and abundance with progression-free survival (PFS), overall survival (OS), and our TME classification was evaluated.

Result and discussion:

Here we show that the prevalence of Bacillus in HCCs of atezo+bev treated patients, was associated with a significantly longer PFS (p=0.006) and a trend toward prolonged OS (p=0.075) compared to those without Bacillus. In addition, Bacillus prevalence and abundance were significantly higher in atezo+bev responders (prevalence: p=0.0029, abundance: p=0.0032 vs non-responders) but not in responders to atezo alone. Especially, ImmunePos responders to atezo+bev, were significantly enriched with Bacillus (prevalence: p=0.0009 vs non-responders; abundance: p=0.01 vs ImmuneNeg responders; p=0.0002 vs non-responders).

Conclusion:

We identified Bacillus specifically associated with a significantly longer PFS and a trend towards longer OS in atezo+bev-treated HCC patients. Moreover, responders to atezo+bev, particularly those with ImmunoPos characteristics, showed significantly higher abundance and prevalence of Bacillus, which suggests that TME has a role in determining the bacterial landscape.