Effects of chemotherapy and immunotherapy on microbial diversity in TME and engineered bacterial-mediated tumor therapy

Most patients diagnosed with resected pancreatic adenocarcinoma (PDAC) survive less than 5-years, but a minor subset survives longer. Here, we dissect the role of the tumor microbiota and the immune system in influencing long-term survival. Using 16S rRNA gene sequencing, we analyzed the tumor microbiome composition in PDAC patients with short and long-term survival (STS, LTS). We found higher alpha-diversity in the tumor microbiome of LTS patients and identified an intra-tumoral microbiome signature (Pseudoxanthomonas/Streptomyces/Saccharopolyspora/Bacillus clausii) highly predictive of long term survivorship in both discovery and validation cohorts. Through human-into-mice Fecal Microbiota Transplantation (FMT) experiments from STS, LTS or control donors, we were able to differentially modulate the tumor microbiome and affect tumor growth as well as tumor immune infiltration. Our study demonstrates that PDAC microbiome composition, which cross-talks to the gut microbiome, influences the host immune response and natural history of the disease. The distinct tumor microbiome from pancreatic cancer long-term survivors can be used to predict PDAC survival in humans, and transfer of long-term survivor gut microbiomes can alter the tumor microbiome and tumor growth in mouse models.

Several infectious agents are considered to be causes of cancer in humans. The fraction of the different types of cancer, and of all cancers worldwide and in different regions, has been estimated using several methods; primarily by reviewing the evidence for the strength of the association (relative risk) and the prevalence of infection in different world areas. The estimated total of infection-attributable cancer in the year 2002 is 1.9 million cases, or 17.8% of the global cancer burden. The principal agents are the bacterium Helicobacter pylori (5.5% of all cancer), the human papilloma viruses (5.2%), the hepatitis B and C viruses (4.9%), Epstein-Barr virus (1%), human immunodeficiency virus (HIV) together with the human herpes virus 8 (0.9%). Relatively less important causes of cancer are the schistosomes (0.1%), human T-cell lymphotropic virus type I (0.03%) and the liver flukes (0.02%). There would be 26.3% fewer cancers in developing countries (1.5 million cases per year) and 7.7% in developed countries (390,000 cases) if these infectious diseases were prevented. The attributable fraction at the specific sites varies from 100% of cervix cancers attributable to the papilloma viruses to a tiny proportion (0.4%) of liver cancers (worldwide) caused by liver flukes. Copyright 2006 Wiley-Liss, Inc.