Table 4.

Studies on animal models; KC mice: p48^Cre; LSL-Kras^G12D. KPC mice: Pdx1^Cre; LSL-Kras^G12D; p53R^172H; Rag1. KO: C57BL/6J mice carrying a Rag1^tm1Mom. WT: wild-type.

Ref.	Experimental Model	Microbiota Association	Main Findings/Authors’ Conclusion
Geller et al., 2017 [65]	Mouse model of colon cancer	Increased Gammaproteobacteria in PDAC	Gammaproteobacteria possessing a long isoform of cytidine deaminase can metabolize gemcitabine.
Pushalkar et al., 2018 [80]	KC and KPC mice	Bacteroidetes and Firmicutes and select Actinobacteria- and Deferribacteres-associated genera were more prevalent in the early-KPC and advanced-KPC cohorts compared with WT	Gut microbiota migrates into the pancreas in mice models. Germ-free mice are protected against PDAC progression. Modulation of gut microbiota influences PDAC tumor progression and has a potential to augment PDAC responsiveness to immune therapy.
Thomas et al., 2018 [81]	KrasG12D/PTENlox/+ mice	Acinetobacter, Enterobacter, Pseudomonas, Delftia, Enterococcus, Streptococcus, Corynebacterium, Propionibacterium, Klebsiella, Sphingomonas and Staphylococcus. Klebsiella as disproportionally overrepresented in PDAC versus HC	Intestinal microbiota exerts long-distance modulation and enhances PDAC carcinogenesis in transgenic and xenograft mouse models of PDAC.
Sethi et al., 2018 [82]	Rag1 KO, KPC, Ptenfl/fl mice	Antibiotics induced a significant decrease in α-diversity, decrease in the relative abundance of Bacteroidetes and Firmicutes in the stool of KPC-bearing mice as well as reversed Bacteroidales: Clostridiales abundance ratio and colonization of the gut by likely antibiotic-resistant Proteobacteria and Tenericutes	Gut microbiome depletion significantly reduced tumor burden in all the models tested, except for Rag1-knockout mice, which lack mature T and B cells.
Aykut et al., 2019 [69]	KC, KPC and WT mice	Malassezia, at about 20% abundance Malassezia spp., most prevalent genus in pancreata of KC mice and exerts a tumor-promoting effect.	Ablation of the mycobiome with the antifungal drugs in mice protected against the PDAC progression and enhanced the effects of gemcitabine by 15 to 25 percent.