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In this chapter, we describe the possible link between gut microbiota, melatonin, and breast cancer disease. It is widely described that changes in melatonin production due to circadian disruption is one of the causes of breast cancer. In addition, recently it is described that dysbiosis caused by changes in the gut microbiota composition could be as well constitute an important factor to induce breast cancer. The dysbiosis process, in turn, induces the stimulation of kynurenine pathway, leading to reduced circulating melatonin levels. Therefore, in this chapter we deep into the relationship between circadian disruption, dysbiosis, and breast cancer disease. This constitutes an important step in the therapeutic approach and prevention of this pathology.

Resistance to Immune Checkpoint Blockade (ICB) constitutes the current limiting factor for the optimal implementation of this novel therapy that otherwise demonstrates durable responses with acceptable toxicity scores. This limitation is exacerbated by a lack of robust biomarkers. In this study, we have dissected the basal TME composition at the gene expression and cellular levels that predict response to Nivolumab and prognosis. BCR, TCR and HLA profiling were employed for further characterization of the molecular variables associated with response. The findings were validated using a single-cell RNA-seq data of metastatic melanoma patients treated with ICB and by multispectral immunofluorescence. Finally, machine learning was employed to construct a prediction algorithm that was validated across eight metastatic melanoma cohorts treated with ICB. Using this strategy, we have unmasked a major role played by basal intratumoral plasma cells expressing high levels of IGKC in efficacy. IGKC, differentially expressed in good responders, was also identified within the Top response-related BCR clonotypes, together with IGK variants. These results were validated at gene, cellular and protein levels; CD138+ Plasma-like and Plasma cells were more abundant in good responders and correlated with the same RNA-seq defined fraction. Finally, we generated a 15-genes prediction model that outperformed the current reference score in eight ICB-treated metastatic melanoma cohorts. The evidenced major contribution of basal intratumoral IGKC and plasma cells in good response and outcome in ICB in metastatic melanoma is a groundbreaking finding in the field beyond the role of T lymphocytes.

Resistance to Immune Checkpoint Blockade (ICB) constitutes the current limiting factor for the optimal implementation of this novel therapy, which otherwise demonstrates durable responses with acceptable toxicity scores. This limitation is exacerbated by a lack of robust biomarkers. In this study, we have dissected the basal TME composition at the gene expression and cellular levels that predict response to Nivolumab and prognosis. BCR, TCR and HLA profiling were employed for further characterization of the molecular variables associated with response. The findings were validated using a single-cell RNA-seq data of metastatic melanoma patients treated with ICB, and by multispectral immunofluorescence. Finally, machine learning was employed to construct a prediction algorithm that was validated across eight metastatic melanoma cohorts treated with ICB. Using this strategy, we have unmasked a major role played by basal intratumoral Plasma cells expressing high levels of IGKC in efficacy. IGKC, differentially expressed in good responders, was also identified within the Top response-related BCR clonotypes, together with IGK variants. These results were validated at gene, cellular and protein levels; CD138+ Plasma-like and Plasma cells were more abundant in good responders and correlated with the same RNA-seq-defined fraction. Finally, we generated a 15-gene prediction model that outperformed the current reference score in eight ICB-treated metastatic melanoma cohorts. The evidenced major contribution of basal intratumoral IGKC and Plasma cells in good response and outcome in ICB in metastatic melanoma is a groundbreaking finding in the field beyond the role of T lymphocytes.

Melatonin is a molecule with different antitumor actions in breast cancer and has been described as an inhibitor of vascular endothelial growth factor (VEGF). Despite the recognition of the key role exerted by VEGF in tumor angiogenesis, limitations arise when developing models to test new antiangiogenic molecules. Thus, the aim of this study was to develop rapid, economic, high capacity and easy handling angiogenesis assays to test the antiangiogenic effects of melatonin and demonstrate its most effective dose to neutralize and interfere with the angiogenic sprouting effect induced by VEGF and MCF-7. To perform this, 3D endothelial cell (HUVEC) spheroids and a chicken embryo chorioallantoic membrane (CAM) assay were used. The results showed that VEGF and MCF-7 were able to stimulate the sprouting of the new vessels in 3D endothelial spheroids and the CAM assay, and that melatonin had an inhibitory effect on angiogenesis. Specifically, as the 1 mM pharmacological dose was the only effective dose able to inhibit the formation of ramifications around the alginate in the CAM assay model, this inhibition was shown to occur in a dose-dependent manner. Taken together, these techniques represent novel tools for the development of antiangiogenic molecules such as melatonin, with possible implications for the therapy of breast cancer. Funding: This work was funded in part by PE-0106–2019 from the Consejería de Salud de la Junta de Andalucía, C19047–2018 from Fundación Unicaja and UMA18-FEDERJA-042 from UMA-FEDER & ALIANZA MIXTA ANDALUCÍA-ROCHE. Alicia González González is a recipient of a postdoctoral grant Margarita Salas (RMS-08) from European Union-NextGenerationEU, Spanish Ministry of Universities and Recovery Transformation and Resilience Plan, through a call from University of Cantabria. Aurora Laborda Illanes is a recipient of a predoctoral grant, PFIS-ISCIII (FI19–00112), co-funded by the Fondo Social Europeo (FSE). Lidia Sanchez Alcoholado is a recipient of a postdoctoral grant (RH-0026–2021) from the Consejería de Salud y Familia (co-funded by the Fondo Europeo de Andalucía 2014–2020, Andalucía, Spain). Daniel Castellano Castillo is a recipient of a postdoctoral grant Sara Borrell (CD21/00164) from Instituto de Salud Carlos III.

Obesity is considered an important factor that increases the risk of colorectal cancer (CRC). So far, the association of gut microbiota with both obesity and cancer has been described independently. Nevertheless, a specific obesity-related microbial profile linked to CRC development has not been identified. The aim of this study was to determine the gut microbiota composition in fecal samples from CRC patients with (OB-CRC) and without obesity (L-CRC) compared to the microbiota profile present in non-obese healthy controls (L-HC), in order to unravel the possible relationship between gut microbiota and microbial-derived metabolite trimethylamine N-oxide (TMAO), the inflammatory status, and the intestinal permeability in the context of obesity-associated CRC. The presence of obesity does not induce significant changes in the diversity and richness of intestinal bacteria of CRC patients. Nevertheless, OB-CRC patients display a specific gut microbiota profile characterized by a reduction in butyrate-producing bacteria and an overabundance of opportunistic pathogens, which in turn could be responsible, at least in part, for the higher levels of proinflammatory cytokine IL-1&beta, the deleterious bacterial metabolite TMAO, and gut permeability found in these patients. These results suggest a possible role of obesity-related gut microbiota in the development of CRC, which could give new clues for the design of new diagnostic tools for CRC prevention.

Simple Summary In this review we discuss the recent knowledge about the role of breast and gut microbiome in the pathogenesis of breast cancer. We examine the proposed mechanisms of interaction between breast tumors and the microbiome. We focus on the role of the microbiome in: (i) the development and maintenance of estrogen metabolism through bacterial beta-glucuronidase enzymes (ii) the regulation of the host´s immune system and tumor immunity by Treg lymphocyte proliferation through bacterial metabolites such as butyrate and propionate (SCFAs), (iii) the induction of chronic inflammation, (iv) the response and/or resistance to treatments and (v) the epigenetic reprogramming. Moreover, we also discuss that diet, probiotics and prebiotics could exert important anticarcinogenic effects in breast cancer that could indicate their employment as adjuvants in standard-of-care breast cancer treatments. Overall, these findings could give new insights for building up novel strategies for breast cancer prevention and treatment. Abstract In breast cancer (BC) the employment of sequencing technologies for metagenomic analyses has allowed not only the description of the overall metagenomic landscape but also the specific microbial changes and their functional implications. Most of the available data suggest that BC is related to bacterial dysbiosis in both the gut microenvironment and breast tissue. It is hypothesized that changes in the composition and functions of several breast and gut bacterial taxa may contribute to BC development and progression through several pathways. One of the most prominent roles of gut microbiota is the regulation of steroid-hormone metabolism, such as estrogens, a component playing an important role as risk factor in BC development, especially in postmenopausal women. On the other hand, breast and gut resident microbiota are the link in the reciprocal interactions between cancer cells and their local environment, since microbiota are capable of modulating mucosal and systemic immune responses. Several in vivo and in vitro studies show remarkable evidence that diet, probiotics and prebiotics could exert important anticarcinogenic effects in BC. Moreover, gut microbiota have an important role in the metabolism of chemotherapeutic drugs and in the activity of immunogenic chemotherapies since they are a potential dominant mediator in the response to cancer therapy. Then, the microbiome impact in BC is multi-factorial, and the gut and breast tissue bacteria population could be important in regulating the local immune system, in tumor formation and progression and in therapy response and/or resistance.

Colorectal cancer (CRC) is the third most common cancer worldwide and the leading cause of cancer-related deaths. Recently, several studies have demonstrated that gut microbiota can alter CRC susceptibility and progression by modulating mechanisms such as inflammation and DNA damage, and by producing metabolites involved in tumor progression or suppression. Dysbiosis of gut microbiota has been observed in patients with CRC, with a decrease in commensal bacterial species (butyrate-producing bacteria) and an enrichment of detrimental bacterial populations (pro-inflammatory opportunistic pathogens). CRC is characterized by altered production of bacterial metabolites directly involved in cancer metabolism including short-chain fatty acids and polyamines. Emerging evidence suggests that diet has an important impact on the risk of CRC development. The intake of high-fiber diets and the supplementation of diet with polyunsaturated fatty acids, polyphenols and probiotics, which are known to regulate gut microbiota, could be not only a potential mechanism for the reduction of CRC risk in a primary prevention setting, but may also be important to enhance the response to cancer therapy when used as adjuvant to conventional treatment for CRC. Therefore, a personalized modulation of the pattern of gut microbiome by diet may be a promising approach to prevent the development and progression of CRC and to improve the efficacy of antitumoral therapy.

Emerging evidence has suggested that dysbiosis of the gut microbiota may influence the drug efficacy of colorectal cancer (CRC) patients during cancer treatment by modulating drug metabolism and the host immune response. Moreover, gut microbiota can produce metabolites that may influence tumor proliferation and therapy responsiveness. In this study we have investigated the potential contribution of the gut microbiota and microbial-derived metabolites such as short chain fatty acids and polyamines to neoadjuvant radiochemotherapy (RCT) outcome in CRC patients. First, we established a profile for healthy gut microbiota by comparing the microbial diversity and composition between CRC patients and healthy controls. Second, our metagenomic analysis revealed that the gut microbiota composition of CRC patients was relatively stable over treatment time with neoadjuvant RCT. Nevertheless, treated patients who achieved clinical benefits from RTC (responders, R) had significantly higher microbial diversity and richness compared to non-responder patients (NR). Importantly, the fecal microbiota of the R was enriched in butyrate-producing bacteria and had significantly higher levels of acetic, butyric, isobutyric, and hexanoic acids than NR. In addition, NR patients exhibited higher serum levels of spermine and acetyl polyamines (oncometabolites related to CRC) as well as zonulin (gut permeability marker), and their gut microbiota was abundant in pro-inflammatory species. Finally, we identified a baseline consortium of five bacterial species that could potentially predict CRC treatment outcome. Overall, our results suggest that the gut microbiota may have an important role in the response to cancer therapies in CRC patients.

Endometrial cancer is one of the most common gynaecological malignancies worldwide. Histologically, two types of endometrial cancer with morphological and molecular differences and also therapeutic implications have been identified. Type I endometrial cancer has an endometrioid morphology and is estrogen-dependent, while Type II appears with non-endometrioid differentiation and follows an estrogen-unrelated pathway. Understanding the molecular biology and genetics of endometrial cancer is crucial for its prognosis and the development of novel therapies for its treatment. However, until now, scant attention has been paid to environmental components like the microbiome. Recently, due to emerging evidence that the uterus is not a sterile cavity, some studies have begun to investigate the composition of the endometrial microbiome and its role in endometrial cancer. In this review, we summarize the current state of this line of investigation, focusing on the relationship between gut and endometrial microbiome and inflammation, estrogen metabolism, and different endometrial cancer therapies.

Simple Summary The relationship between melatonin and breast cancer has been widely described. On the other hand, in recent years, an imbalance in the composition of the intestinal bacterial population has been linked as another possible trigger for this disease. Given that changes in the gut microbiota have been observed to stimulate the kinurenine pathway, reducing circulating melatonin levels, in this review, we summarize the relationship between circadian disruption and breast cancer, as well as the connection with dysbiosis as possible causing this pathology due to a series of changes that lead to an increase in circulating estrogen levels. Abstract In this review we summarize a possible connection between gut microbiota, melatonin production, and breast cancer. An imbalance in gut bacterial population composition (dysbiosis), or changes in the production of melatonin (circadian disruption) alters estrogen levels. On the one hand, this may be due to the bacterial composition of estrobolome, since bacteria with β-glucuronidase activity favour estrogens in a deconjugated state, which may ultimately lead to pathologies, including breast cancer. On the other hand, it has been shown that these changes in intestinal microbiota stimulate the kynurenine pathway, moving tryptophan away from the melatonergic pathway, thereby reducing circulating melatonin levels. Due to the fact that melatonin has antiestrogenic properties, it affects active and inactive estrogen levels. These changes increase the risk of developing breast cancer. Additionally, melatonin stimulates the differentiation of preadipocytes into adipocytes, which have low estrogen levels due to the fact that adipocytes do not express aromatase. Consequently, melatonin also reduces the risk of breast cancer. However, more studies are needed to determine the relationship between microbiota, melatonin, and breast cancer, in addition to clinical trials to confirm the sensitizing effects of melatonin to chemotherapy and radiotherapy, and its ability to ameliorate or prevent the side effects of these therapies.

The aims of this study were to explore intestinal microbial composition and functionality in primary Sj&ouml, gren&rsquo, s syndrome (pSS) and to relate these findings to inflammation, permeability and the transcription factor Forkhead box protein P3 (FOXP3) gene expression in peripheral blood. The study included 19 pSS patients and 19 healthy controls matched for age, sex, and body mass index. Fecal bacterial DNA was extracted and analyzed by 16S rRNA sequencing using an Ion S5 platform followed by a bioinformatics analysis using Quantitative Insights into Microbial Ecology (QIIME II) and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Our data suggest that the gut microbiota of pSS patients differs at both the taxonomic and functional levels with respect to healthy controls. The gut microbiota profile of our pSS patients was characterized by a lower diversity and richness and with Bacteroidetes dominating at the phylum level. The pSS patients had less beneficial or commensal butyrate-producing bacteria and a higher proportion of opportunistic pathogens with proinflammatory activity, which may impair intestinal barrier function and therefore contribute to inflammatory processes associated with pSS by increasing the production of proinflammatory cytokines and decreasing the release of the anti-inflammatory cytokine IL-10 and the peripheral FOXP3 mRNA expression, implicated in the development and function of regulatory T cells (Treg) cells. Further studies are needed to better understand the real impact of dysbiosis on the course of pSS and to conceive preventive or therapeutic strategies to counteract microbiome-driven inflammation.

Melanoma comprises a variety of malignant cell types from the skin, the mucous membranes, and the pigmented cells of the eye. Its incidence and mortality rates continue to rise worldwide, mainly driven by increased ultraviolet light exposure. Although screening improvements have led to a better diagnosis in the early stages, the outcome for patients with Metastatic Melanoma (MM) remains poor and the survival rate is considerably low. Recently, Immune Checkpoint Inhibitors (ICB) have revolutionized the treatment of MM, although only 30% of patients enjoy clinical benefit and a plethora of different molecular mechanisms is postulated to cause resistance. Several biomarkers are currently on the spotlight as putative predictors of response; however, they are not sufficiently informative and robust. Circular RNAs (circRNAs) are a class of single-stranded stable RNAs produced by 5′-to-3′ transcription of coding gene exons or long non-coding RNAs that act as translation templates, RNA-binding protein regulators, or miRNA-binding sponges. Here, we present an exploratory study to evaluate the potential use of circRNA as ICB response predictors. We recruited 23 MM patients treated with Nivolumab and categorized them as good responders (10 patients) and bad responders (11 patients). All RNA-seq with ribosomal depletion was performed on RNA isolated from pre-treatment FFPE tumor biopsies. Two bioinformatic tools that use de novo assembly for the identification of circRNAs (Starchip and Ciri) were employed independently to characterize the MM circRNAs profile and to identify a specific pattern for responders. Overall, a total of 731 circRNAs were detected. Interestingly, the number of circRNAs were comparatively higher in bad responders (11.917 reads, 321 circRNAs) versus good responders (7368 reads, 176 circRNAs), with 234 common circRNAs. Additionally, we also explored the biological function of the identified circRNAs in MM, by interrogating KEGG, GO and Reactome databases to delineate the gene regulatory networks specifically associated with the response-related phenotypes. The circRNAs exclusively expressed in patients presenting resistance to Nivolumab were associated with Transcriptional Misregulation in Cancer and Viral Infections processes. In contrast, circRNAs expressed uniquely in good responders were enriched in Generic Transcription pathways. Importantly, amongst the identified circRNAs, CDR1-AS was differentially downregulated in good responders (536 vs 1580 reads, p-value 0.002). Remarkably, CDR1-AS acts as miRNA-binding sponge of miRNA-7 in the context of invasion and migration in melanoma. In conclusion, our exploratory study paves the way to the utilization of novel biomarkers associated to immunotherapy failure in MM patients. Moreover, our results suggest that CDR1-AS is a novel putative predictor of ICB response. Citation Format: Juan Luis Onieva, Javier Oliver, Aurora Laborda-Illanes, Maria Rosario Chica-Parrado, Alicia Garrido-Aranda, Cynthia Robles-Podadera, Daniel Prieto, Elena Gallego, Alfonso Sanchez, Iñaki Comino, Vanessa De Luque, Martina Alvarez, Maria Jose Lozano, Pedro Jimenez, Miguel Angel Berciano-Guerrero, Emilio Alba, Manuel Cobo, Isabel Barragan. Evaluation of circular RNA profiling in metastatic melanoma patients treated with immune checkpoint blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 281.

e21603 Background: Despite the efforts, there is still no biomarker that is able to predict the response and / or that can be used in the monitoring of patients treated with check-points inhibitors (ICI). Methods: Prospective study of a panel of blood biomarkers that help predict the response to ICI treatments. Since June 2019, a total of 60 patients with non-small cell lung cancer (NSCLC) or melanoma have been included. Prior to the start of treatment (T1 moment), after the first cycle of ICI (T2), and to progression (Tp) or 6 months after the start, blood sample has been drawn to the patients and the analysis has been carried out by flow cytometry of the percentage of lymphocytes CD8, CD3, Treg, Myeloids, NK and B lymphocytes. The one.way statistical test has been carried out that allows us to see the effect of the response on the variable at each time. Results: Of the 60 patients included, we have radiological assessment in 38. 80% are patients with NSCLC. In the evaluation at 8-10 weeks we found stable disease / partial response in 25 patients (66%), 8 progressions (21%) and 2 unknown reevaluations (13%). A significant increase in CD3, CD8, CD4, and B lymphocytes was observed in responders (p < 0.005); however, an increase in NK was observed in patients in progression (p < 0.02). No significant differences in Treg have been described and the result related to myeloid cells is pending analysis. Conclusions: Our results open a door to peripheral blood monitoring as a new tool for the management of ICI. However, our data are preliminary, having not yet reached the expected sample size and with aspects that we must clarify as the increase in NK in progressors. In addition, the final objective of this study is to generate a score combining several biomarkers of blood and tissue to be used as a predictor of response to ICI (data pending analysis).

Endometrial cancer is one of the most common gynaecological malignancies worldwide. Histologically, two types of endometrial cancer with morphological and molecular differences and also therapeutic implications have been identified. Type I endometrial cancer has an endometrioid morphology and is estrogen-dependent, while Type II appears with non-endometrioid differentiation and follows an estrogen-unrelated pathway. Understanding the molecular biology and genetics of endometrial cancer is crucial for its prognosis and the development of novel therapies for its treatment. However, until now, scant attention has been paid to environmental components like the microbiome. Recently, due to emerging evidence that the uterus is not a sterile cavity, some studies have begun to investigate the composition of the endometrial microbiome and its role in endometrial cancer. In this review, we summarize the current state of this line of investigation, focusing on the relationship between gut and endometrial microbiome and inflammation, estrogen metabolism, and different endometrial cancer therapies. Yes

In breast cancer (BC) the employment of sequencing technologies for metagenomic analyses has allowed not only the description of the overall metagenomic landscape but also the specific microbial changes and their functional implications. Most of the available data suggest that BC is related to bacterial dysbiosis in both the gut microenvironment and breast tissue. It is hypothesized that changes in the composition and functions of several breast and gut bacterial taxa may contribute to BC development and progression through several pathways. One of the most prominent roles of gut microbiota is the regulation of steroid-hormone metabolism, such as estrogens, a component playing an important role as risk factor in BC development, especially in postmenopausal women. On the other hand, breast and gut resident microbiota are the link in the reciprocal interactions between cancer cells and their local environment, since microbiota are capable of modulating mucosal and systemic immune responses. Several in vivo and in vitro studies show remarkable evidence that diet, probiotics and prebiotics could exert important anticarcinogenic effects in BC. Moreover, gut microbiota have an important role in the metabolism of chemotherapeutic drugs and in the activity of immunogenic chemotherapies since they are a potential dominant mediator in the response to cancer therapy. Then, the microbiome impact in BC is multi-factorial, and the gut and breast tissue bacteria population could be important in regulating the local immune system, in tumor formation and progression and in therapy response and/or resistance. Yes

Colorectal cancer (CRC) is the third most common cancer worldwide and the leading cause of cancer-related deaths. Recently, several studies have demonstrated that gut microbiota can alter CRC susceptibility and progression by modulating mechanisms such as inflammation and DNA damage, and by producing metabolites involved in tumor progression or suppression. Dysbiosis of gut microbiota has been observed in patients with CRC, with a decrease in commensal bacterial species (butyrate-producing bacteria) and an enrichment of detrimental bacterial populations (pro-inflammatory opportunistic pathogens). CRC is characterized by altered production of bacterial metabolites directly involved in cancer metabolism including short-chain fatty acids and polyamines. Emerging evidence suggests that diet has an important impact on the risk of CRC development. The intake of high-fiber diets and the supplementation of diet with polyunsaturated fatty acids, polyphenols and probiotics, which are known to regulate gut microbiota, could be not only a potential mechanism for the reduction of CRC risk in a primary prevention setting, but may also be important to enhance the response to cancer therapy when used as adjuvant to conventional treatment for CRC. Therefore, a personalized modulation of the pattern of gut microbiome by diet may be a promising approach to prevent the development and progression of CRC and to improve the efficacy of antitumoral therapy. Yes