ABSTRACT
Cancer cells adapt their metabolism to support elevated energetic and anabolic demands of proliferation. Folate-dependent one-carbon metabolism is a critical metabolic process underpinning cellular proliferation supplying carbons for the synthesis of nucleotides incorporated into DNA and RNA. Recent research has focused on the nutrients that supply one-carbons to the folate cycle, particularly serine. Tryptophan is a theoretical source of one-carbon units through metabolism by IDO1, an enzyme intensively investigated in the context of tumor immune evasion. Using in vitro and in vivo pancreatic cancer models, we show that IDO1 expression is highly context dependent, influenced by attachment-independent growth and the canonical activator IFNγ. In IDO1-expressing cancer cells, tryptophan is a bona fide one-carbon donor for purine nucleotide synthesis in vitro and in vivo. Furthermore, we show that cancer cells release tryptophan-derived formate, which can be used by pancreatic stellate cells to support purine nucleotide synthesis.
Subject(s)
Carcinoma, Pancreatic Ductal/genetics , Indoleamine-Pyrrole 2,3,-Dioxygenase/genetics , Pancreatic Neoplasms/genetics , Pancreatic Stellate Cells/metabolism , Tumor Escape/drug effects , Allografts , Animals , Antineoplastic Agents/pharmacology , Carbon/immunology , Carbon/metabolism , Carcinoma, Pancreatic Ductal/drug therapy , Carcinoma, Pancreatic Ductal/immunology , Carcinoma, Pancreatic Ductal/mortality , Cell Line, Tumor , Formates/immunology , Formates/metabolism , Gene Expression Regulation, Neoplastic , Humans , Indoleamine-Pyrrole 2,3,-Dioxygenase/immunology , Interferon-gamma/genetics , Interferon-gamma/immunology , Metabolic Networks and Pathways/drug effects , Metabolic Networks and Pathways/genetics , Mice , Mice, Inbred C57BL , Mice, Nude , Oximes/pharmacology , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/immunology , Pancreatic Neoplasms/mortality , Pancreatic Stellate Cells/drug effects , Pancreatic Stellate Cells/immunology , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/immunology , Serine/immunology , Serine/metabolism , Serine/pharmacology , Signal Transduction , Sulfonamides/pharmacology , Tryptophan/immunology , Tryptophan/metabolism , Tryptophan/pharmacology , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/immunologyABSTRACT
Enteropathogenic Escherichia coli (EPEC) is an attaching and effacing (A/E) human pathogen that causes diarrhea during acute infection, and it can also sustain asymptomatic colonization. A/E E. coli depletes host cell DNA mismatch repair (MMR) proteins in colonic cell lines and has been detected in colorectal cancer (CRC) patients. However, until now, a direct link between infection and host mutagenesis has not been fully demonstrated. Here we show that the EPEC-secreted effector protein EspF is critical for complete EPEC-induced depletion of MMR proteins. The mechanism of EspF activity on MMR protein was posttranscriptional and dependent on EspF mitochondrial targeting. EPEC infection also induced EspF-independent elevation of host reactive oxygen species levels. Moreover, EPEC infection significantly increased spontaneous mutation frequency in host cells, and this effect was dependent on mitochondrially targeted EspF. Taken together, these results support the hypothesis that A/E E. coli can promote colorectal carcinogenesis in humans.
