Colibactin‐producing E. coli (CoPEC) are frequently detected in colorectal cancer (CRC) and exhibit procarcinogenic properties. Because increasing evidence show the role of immune environment and especially of antitumor T‐cells in CRC development, we investigated the impact of CoPEC on these cells in human CRC and in the APCMin/+ mice colon. T‐cell density was evaluated by immunohistochemistry in human tumors known for their CoPEC status. APCmin/+ mice were chronically infected with a CoPEC strain (11G5). Immune cells (neutrophils and T‐cell populations) were then quantified by immunofluorescent staining of the colon. The quantification of lymphoid populations was also performed in the mesenteric lymph nodes (MLNs). Here, we show that the colonization of CRC patients by CoPEC is associated with a decrease of tumor‐infiltrating T lymphocytes (CD3+ T‐cells). Similarly, we demonstrated, in mice, that CoPEC chronic infection decreases CD3+ and CD8+ T‐cells and increases colonic inflammation. In addition, we noticed a significant decrease in antitumor T‐cells in the MLNs of CoPEC‐infected mice compared to that of controls. Moreover, we show that CoPEC infection decreases the antimouse PD‐1 immunotherapy efficacy in MC38 tumor model. Our findings suggest that CoPEC could promote a procarcinogenic immune environment through impairment of antitumor T‐cell response, leading to tumoral resistance to immunotherapy. CoPEC could thus be a new biomarker predicting the anti‐PD‐1 response in CRC.

SummarySurvival following pancreatic cancer remains poor despite incremental advances in surgical and adjuvant therapy, and new strategies for treatment are needed. Oncolytic virotherapy is an attractive approach for cancer treatment. In this study, we have evaluated the effectiveness of the Lister vaccine strain of vaccinia virus armed with the endostatin-angiostatin fusion gene (VVhEA) as a novel therapeutic approach for pancreatic cancer. The Lister vaccine strain of vaccinia virus was effective against all human pancreatic carcinoma cells tested in vitro, especially those insensitive to oncolytic adenovirus. The virus displayed inherently high selectivity for cancer cells, sparing normal cells both in vitro and in vivo, with effective infection of tumors after both intravenous (IV) and intratumoral (IT) administration. The expression of endostatin-angiostatin fusion protein was confirmed in a pancreatic cancer model both in vitro and in vivo, with evidence of inhibition of angiogenesis. This novel vaccinia virus demonstrated significant antitumor potency in vivo against the Suit-2 model by IT administration. The present study suggests that the novel Lister strain of vaccinia virus armed with the endostatin-angiostatin fusion gene is a potential therapeutic agent for pancreatic cancer.

This study demonstrated that despite the detrimental effect observed in vitro, insertion of the reporter gene NIS in an oncolytic adenovirus did not affect its therapeutic efficacy in vivo. We conclude that NIS is a highly relevant reporter gene to monitor the fate of oncolytic adenovectors in live subjects.

Tetraspanin 8 (TSPAN8) overexpression is correlated with poor prognosis in human colorectal cancer (CRC). A murine mAb Ts29.2 specific for human TSPAN8 provided significant efficiency for immunotherapy in CRC pre-clinical models. We therefore evaluate the feasability of targeting TSPAN8 in CRC with radiolabeled Ts29.2. Staining of tissue micro-arrays with Ts29.2 revealed that TSPAN8 espression was restricted to a few human healthy tissues. DOTA-Ts29.2 was radiolabeled with 111In or 177Lu with radiochemical purities >95%, specific activity ranging from 300 to 600 MBq/mg, and radioimmunoreactive fractions >80%. The biodistribution of [111In]DOTA-Ts29.2 in nude mice bearing HT29 or SW480 CRC xenografts showed a high specificity of tumor localization with high tumor/blood ratios (HT29: 4.3; SW480-TSPAN8: 3.9 at 72h and 120h post injection respectively). Tumor-specific absorbed dose calculations for [177Lu]DOTA-Ts29.2 was 1.89 Gy/MBq, establishing the feasibility of using radioimmunotherapy of CRC with this radiolabeled antibody. A significant inhibition of tumor growth in HT29 tumor-bearing mice treated with [177Lu]DOTA-Ts29.2 was observed compared to control groups. Ex vivo experiments revealed specific DNA double strand breaks associated with cell apoptosis in [177Lu]DOTA-Ts29.2 treated tumors compared to controls. Overall, we provide a proof-of-concept for the use of [111In/177Lu]DOTA-Ts29.2 that specifically target in vivo aggressive TSPAN8-positive cells in CRC.