Intracellular colon cancer-associated Escherichia coli promote protumoral activities of human macrophages by inducing sustained COX-2 expression

Abstract

Intestinal dysbiosis has been reported in patients with colorectal cancer, and there is a high prevalence of Escherichia coli belonging to B2 phylogroup and producing a genotoxin, termed colibactin. Macrophages are one of the predominant tumor-infiltrating immune cells supporting key processes in tumor progression by producing protumoral factors such as cyclooxygenase-2 (COX-2). Here, we investigated whether B2 E. coli colonizing colon tumors could influence protumoral activities of macrophages. In contrast to commensal or nonpathogenic E. coli strains that were efficiently and rapidly degraded by macrophages at 24 h after infection, colon cancer-associated E. coli were able to resist killing by human THP-1 macrophages, to replicate intracellularly, and to persist inside host cells until at least 72 h after infection. Significant increases in COX-2 expression were observed in macrophages infected with colon cancer E. coli compared with macrophages infected with commensal and nonpathogenic E. coli strains or uninfected cells at 72 h after infection. Induction of COX-2 expression required live bacteria and was not due to colibactin production, as similar COX-2 levels were observed in macrophages infected with the wild-type colon cancer-associated E. coli 11G5 strain or a clbQ mutant unable to produce colibactin. Treatment of macrophages with ofloxacin, an antibiotic with intracellular tropism, efficiently decreased the number of intracellular bacteria and suppressed bacteria-induced COX-2 expression. This study provides new insights into the understanding of how tumor-infiltrating bacteria could influence cancer progression through their interaction with immune cells. Manipulation of microbes associated with tumors could have a deep influence on the secretion of protumoral molecules by infiltrating macrophages. Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies worldwide, making it the fourth most common cause of cancer deaths throughout the world. 1 CRC is a heterogeneous disease, including at least three major forms: hereditary, sporadic, and colitis-associated CRC. A large body of evidence indicates that genetic mutations, epigenetic changes, chronic inflammation, diet, and lifestyle deeply affect CRC onset. 2,3 In addition to these factors, gut microbiota dysbiosis has been reported in CRC patients. [4][5][6][7][8][9] Recent pyrosequencing analysis of CRC-associated bacterial microbiota has revealed dysbiosis with, in particular, overrepresentation of Fusobacterium and Bacteroides. [10][11][12][13][14] In addition, our group and others have shown that colonic adenomas, carcinomas, and the mucosa of CRC patients are abnormally colonized by Escherichia coli belonging to the B2 phylogroup, with a high prevalence of E. coli producing a genotoxin, termed colibactin, encoded by the pks genomic island. [15][16][17][18][19][20] It has been recently demonstrated that cells that survive infection with colibactin-producing E. coli display hallmarks of cellular senescence accompanied with productio...

Comparative genomics of Crohn's disease-associated adherent-invasiveEscherichia coli

“…As previously demonstrated,51 strain ED1a was killed by THP-1 macrophages, demonstrating efficient bactericidal activity of the cell lines (table 1). As expected, strain K12 was also killed, and strain LF82 resisted macrophage killing (table 1).…”

“…Subramanian et al 57 also observed considerable overlap between the ability of CD and control isolates to replicate within macrophages, and Raisch et al 51 showed that 84% of colon cancer-associated B2 E. coli strains can survive and replicate within THP-1 macrophages. UPEC are also capable of intramacrophage replication 56.…”

Colonic macrophage polarization in homeostasis, inflammation, and cancer

“…This increased permeability, however, could also contribute to tipping the balance in favor of M2 TAMs. CRCassociated E. coli, but not commensal E. coli, has been shown to survive within macrophages derived from the THP-1 human monocyte cell line and to induce Cox-2 expression in these cells (80). Cox-2 activity is important for the M2 phenotype of TAMs, as inhibition of this enzyme skews TAMs toward an M1 phenotype in tumors of Apc Min/ϩ mice (67).…”

The Role of Escherichia coli in the Development and Progression of Cancer

“…Likewise, a recent study suggests that colibactin is not involved on development and maintenance of inflammation. In contrast, the macrophages infiltration into the intestinal epithelium is induced by overgrowth of pks + E. coli strains, and inflammation dependent on COX-2 activation is established (52). Thus, once established the intestinal inflammation, E. coli proliferation is increased and the production of colibactin started after pks island activation.…”