Different gastrointestinal disorders, including inflammatory bowel diseases (IBD), have been linked to alterations of the gut microbiota composition, namely dysbiosis. Fecal microbiota transplantation (FMT) is considered an encouraging therapeutic approach for ulcerative colitis patients, mostly as a consequence of normobiosis restoration. We recently showed that therapeutic effects of FMT during acute experimental colitis are linked to functional modulation of the mucosal immune system and of the gut microbiota composition. Here we analysed the effects of therapeutic FMT administration during chronic experimental colitis, a condition more similar to that of IBD patients, on immune-mediated mucosal inflammatory pathways. Mucus and feces from normobiotic donors were orally administered to mice with established chronic Dextran Sodium Sulphate (DSS)-induced colitis. Immunophenotypes and functions of infiltrating colonic immune cells were evaluated by cytofluorimetric analysis. Compositional differences in the intestinal microbiome were analyzed by 16S rRNA sequencing. Therapeutic FMT in mice undergoing chronic intestinal inflammation was capable to decrease colonic inflammation by modulating the expression of pro-inflammatory genes, antimicrobial peptides, and mucins. Innate and adaptive mucosal immune cells manifested a reduced pro-inflammatory profile in FMT-treated mice. Finally, restoration of a normobiotic core ecology contributed to the resolution of inflammation. Thus, FMT is capable of controlling chronic intestinal experimental colitis by inducing a concerted activation of anti-inflammatory immune pathways, mechanistically supporting the positive results of FMT treatment reported in ulcerative colitis patients.

CD8+ T cells are a major prognostic determinant in solid tumors, including colorectal cancer (CRC). However, understanding how the interplay between different immune cells impacts on clinical outcome is still in its infancy. Here, we describe that the interaction of tumor infiltrating neutrophils expressing high levels of CD15 with CD8+ T effector memory cells (TEM) correlates with tumor progression. Mechanistically, stromal cell-derived factor-1 (CXCL12/SDF-1) promotes the retention of neutrophils within tumors, increasing the crosstalk with CD8+ T cells. As a consequence of the contact-mediated interaction with neutrophils, CD8+ T cells are skewed to produce high levels of GZMK, which in turn decreases E-cadherin on the intestinal epithelium and favors tumor progression. Overall, our results highlight the emergence of GZMKhigh CD8+ TEM in non-metastatic CRC tumors as a hallmark driven by the interaction with neutrophils, which could implement current patient stratification and be targeted by novel therapeutics.

Purpose Post-finasteride syndrome (PFS) has been reported in a subset of patients treated with finasteride (an inhibitor of the enzyme 5alpha-reductase) for androgenetic alopecia. These patients showed, despite the suspension of the treatment, a variety of persistent symptoms, like sexual dysfunction and cognitive and psychological disorders, including depression. A growing body of literature highlights the relevance of the gut microbiota-brain axis in human health and disease. For instance, alterations in gut microbiota composition have been reported in patients with major depressive disorder. Therefore, we have here analyzed the gut microbiota composition in PFS patients in comparison with a healthy cohort. Methods Fecal microbiota of 23 PFS patients was analyzed by 16S rRNA gene sequencing and compared with that reported in ten healthy male subjects. Results Sexual dysfunction, psychological and cognitive complaints, muscular problems, and physical alterations symptoms were reported in more than half of the PFS patients at the moment of sample collection. The quality sequence check revealed a low library depth for two fecal samples. Therefore, the gut microbiota analyses were conducted on 21 patients. The α-diversity was significantly lower in PFS group, showing a reduction of richness and diversity of gut microbiota structure. Moreover, when visualizing β-diversity, a clustering effect was found in the gut microbiota of a subset of PFS subjects, which was also characterized by a reduction in Faecalibacterium spp. and Ruminococcaceae UCG-005, while Alloprevotella and Odoribacter spp were increased compared to healthy control. Conclusion Gut microbiota population is altered in PFS patients, suggesting that it might represent a diagnostic marker and a possible therapeutic target for this syndrome.

Background The association between microbes and cancer has been reported repeatedly; however, it is not clear if molecular tumour properties are connected to specific microbial colonisation patterns. This is due mainly to the current technical and analytical strategy limitations to characterise tumour-associated bacteria. Methods Here, we propose an approach to detect bacterial signals in human RNA sequencing data and associate them with the clinical and molecular properties of the tumours. The method was tested on public datasets from The Cancer Genome Atlas, and its accuracy was assessed on a new cohort of colorectal cancer patients. Results Our analysis shows that intratumoural microbiome composition is correlated with survival, anatomic location, microsatellite instability, consensus molecular subtype and immune cell infiltration in colon tumours. In particular, we find Faecalibacterium prausnitzii, Coprococcus comes, Bacteroides spp., Fusobacterium spp. and Clostridium spp. to be strongly associated with tumour properties. Conclusions We implemented an approach to concurrently analyse clinical and molecular properties of the tumour as well as the composition of the associated microbiome. Our results may improve patient stratification and pave the path for mechanistic studies on microbiota-tumour crosstalk.

Tumor contexture has emerged as a major determinant to establish prognosis and guide novel therapies and tumor infiltrating CD8+ T cells have been associated with a better prognosis in several solid tumors, including early-stage colorectal cancer (CRC). However, the tumor immune infiltrate is highly heterogeneous and understanding how the interplay between different immune cell compartments impacts on the clinical outcome is still in its infancy. Here, we describe in a prospective cohort a novel CD8+ T effector memory population, which is characterized by high levels of Granzyme K (GZMKhigh CD8+ TEM) and correlated with CD15high tumor infiltrating neutrophils. We provide both in vitro and in vivo evidence of the role of stromal cell-derived factor 1 (CXCL12/SDF-1) in driving functional changes on neutrophils at the tumor site, promoting their retention and increasing crosstalk with CD8+ T cells. Mechanistically, as a consequence of the interaction with neutrophils, CD8+ T cells are skewed towards a CD8+ TEM phenotype, producing high levels of GZMK, which in turn decreased E-cadherin pathway. The correlation of GZMKhigh CD8+ TEM and neutrophils with both tumor progression in mice and early relapse in CRC patients demonstrate the role of GZMKhigh CD8+ TEM in promoting malignancy. Indeed, a gene signature defining GZMKhigh CD8+ TEM was associated with worse prognosis on a larger independent cohort of CRC patients and a similar analysis was extended to lung cancer (TCGA). Overall, our results highlight the emergence of GZMKhigh CD8+ TEM in early-stage CRC tumors as a hallmark driven by the interaction with neutrophils, which could implement current patient stratification and be targeted by novel therapeutics.

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422 Background: Gastric adenocarcinoma (GA) represents a leading cause of cancer death worldwide. For localized and locally advanced (LA) GA, accounting for 30% of new diagnoses, surgery, with or without peri-operative chemotherapy (CTX), remains the cornerstone of treatment. Nevertheless, the cure rate remains unsatisfactory. Genomic biomarkers have been tested to tailor anticancer treatments, but no one is able to guide the treatment choice in GA. Gut microbiota represents an emerging area of investigation in cancer, as a key modulator of host immune response. However, its role in GA on treatment tolerability and outcome is not unraveled. Additionally, radiomics, which can perform massive data mining to increase diagnostic power, and extensive dietary assessment are fast-growing tools. Our aim is to set an innovative approach to mapping the interaction among nutrition, microbiome, genomics, and radiomics and correlate them with clinical outcomes. Methods: We are conducting a prospective observational trial in GA patients (pts), candidates to receive peri-operative CTX or upfront surgery. For each patient, we longitudinally collect blood, fecal and salivary samples, alongside clinical and nutritional information. Additionally, past dietary consumption is measured using the food frequency questionnaire. At baseline, CT scan for staging, radiomic analysis, upper digestive endoscopy with biopsy, and molecular biomarkers are performed. Additional samples are taken from tumor and surrounding normal mucosa (1 to 3 cm) for microbiome analysis. Genomic DNA from stool, buccal and gastric tissue samples will be extracted and subjected to 16S metagenomic sequencing. Taxonomic and functional features within and between anatomical compartments will be correlated with clinical and radiomic data. Results: Here, we are presenting preliminary data of fecal samples from 35 GA pts in comparison with a cohort of healthy subjects (HCs) collected at our Institution. Pts’ characteristics are outlined here. We observed that the structure of the gut microbiota of GA pts is distinct from HCs in terms of beta diversity, and this difference is maintained after CTX. In particular, GA’s microbiota was enriched in S. anginosus, among other taxa. Conclusions: Our preliminary data support the feasibility of the study. The differences in structure and composition of the gut microbiota of GA pts compared to HCs confirm previous reports while providing the rationale for developing gut microbiota profiling into a non-invasive biomarker, to implement early diagnosis and prevention. The study is ongoing and actively recruiting.[Table: see text]

Background: The high resistance of melanoma to targeted therapy has made it a persistently lethal cancer type. Although the advent of immune checkpoint inhibition (ICI) therapy markedly improved outcome for melanoma in recent years, response remains heterogenous, with only 20-40% of patients achieving clinical response for anti-CTLA4 or anti-PD1 therapy. This variability in response has urged research towards host factors that drive response to immunotherapy, and studies have come out to show that the gut microbiota influences immunotherapy response. More importantly, mouse studies and more recent human clinical trials demonstrate that transplantation of responder (R) microbiota improves host immunity and alleviates tumor growth during immunotherapy. Although these findings confirm a close relationship between the gut microbiota and antitumor host immunity, FMT human clinical trials on melanoma patients report success in only 30-40% of patients, suggesting that current knowledge of underlying immunomodulatory mechanisms of the gut microbiota are still limited, and that analysis of data collected only before start of therapy is insufficient. Notably, there is a lack of published longitudinal studies that monitor gut microbiome changes during melanoma immunotherapy. Methods: We performed longitudinal analysis of the gut microbiota in melanoma patients undergoing NEOAJUVANT immunotherapy, revealing distinct dynamics between R and non-responders (NR) over the course of treatment. Sequencing data were paralleled with a quantitative analysis of circulating inflammatory molecules, suggesting a dynamic interaction between the gut microbiota and immune system. Here, we will present key modulators of the immune cell compartment. Conclusions: Overall, our results highlight the importance of longitudinal analysis to dissect the role of the gut microbiota on response to immunotherapy. Citation Format: Angeli Dominique Macandog, Carlotta Catozzi, Ester Cassano, Sara Gandini, Pier Francesco Ferrucci, Emilia Cocorocchio, Teresa Manzo, Luigi Nezi. Gut microbiota shift in melanoma patients undergoing immunotherapy is associated with clinical response [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P073.