1502P Heavy pre-treatment is associated with microbiome dysbiosis, reduced immune infiltration, and potential resistance to immune checkpoint inhibitors in metastatic sarcoma

Abstract

A unique feature of sarcoma metastasis is the escape from aseptic positions(mesenchymal) to aseptic organ such as lung. Here, we explore the lung microbiome of sarcoma in association with immune-microenvironment and immunotherapy. We investigated the microbiome landscape of 100 recurrent sarcoma samples by shot-gun metagenomic sequencing of osteosarcoma(n=90) and other sarcoma(n=10), including 24 tumor-adjacent lung tissue, 73 pleural effusion, and 3 abdomen/subdermal effusion. The microbiome characteristics were investigated in association with immune infiltration and T-cell receptor(TCR) repertoire in 58 samples, and with the clinical efficacy of PD-1 blockade in 22 patients. We identified a mean of 99 genera in lung tissue, 41 in pleural effusion and 18 in other effusion. There was a significant association of prior-lines of chemotherapy with microbiome diversity in terms of quantity (Chao) and diversity (Shannon). Hierarchical clustering suggested 3 clusters of microbiome composition-C1:abundance subtype (high-quantity and diversity, n=43); C2:disrupted subtype (high-quantity, low-diversity, n=35) and C3:depleted subtype (low-quantity, low diversity, n=22). Furthermore, patients with heavier therapy were enriched in C2 (disrupted) and C3 (depleted) subtypes. Interestingly, we observed a significantly higher TCR diversity, IFN-gamma, and CD8-T cells in the C1 (abundance) microenvironment. Comparing 15 samples from responders (cutoff=4 months) versus 18 non-responders, we found 61 genera associated with PD-1 inhibition efficacy, including known immune-stimulatory microbes, such as Streptococcus (reminiscent of Coley-toxins), Rhodanobacter, Bifidobacterium, Anaerococcus, etc. Surprisingly, these microbiome was highly prosperous in C1 (abundance) and low in the C2 (disrupted), but were either missing or in complete dysbiosis in the C3 (depleted) subtype. Our report depicts the first landscape of lung microbiome associated with metastatic sarcoma, which suggests the potential of avoiding microbiome dysbiosis during chemotherapy and boosting microbiome for immunotherapy in metastatic sarcoma.