Microbiome and Anticancer Immunosurveillance. Cell. 2016;165:276-287. [PMID: 27058662 DOI: 10.1016/j.cell.2016.03.001]

Microbiota-driven mechanisms at different stages of cancer development

A myriad of microbes living together with the host constitutes the microbiota, and the microbiota exerts very diverse functions in the regulation of host physiology. Microbiota regulates cancer initiation, progression, metastasis, and responses to therapy. Here we review known pro-tumorigenic and anti-tumorigenic functions of microbiota, and mechanisms of how microbes can shape tumor microenvironment and affect cancer cells as well as activation and functionality of immune and stromal cells within the tumor. While some of these mechanisms are distal, often distinct members of microbiota travel with and establish colonization with the tumors in the distant organs. We further briefly describe recent findings regarding microbiota composition in metastasis and highlight important future directions and considerations for the manipulation of microbiota for cancer treatment.

Preexisting antibodies targeting SARS-CoV-2 S2 cross-react with commensal gut bacteria and impact COVID-19 vaccine induced immunity

The origins of preexisting SARS-CoV-2 cross-reactive antibodies and their potential impacts on vaccine efficacy have not been fully clarified. In this study, we demonstrated that S2 was the prevailing target of the preexisting S protein cross-reactive antibodies in both healthy human and SPF mice. A dominant antibody epitope was identified on the connector domain of S2 (1147-SFKEELDKYFKNHT-1160, P144), which could be recognized by preexisting antibodies in both human and mouse. Through metagenomic sequencing and fecal bacteria transplant, we demonstrated that the generation of S2 cross-reactive antibodies was associated with commensal gut bacteria. Furthermore, six P144 reactive monoclonal antibodies were isolated from naïve SPF mice and were proven to cross-react with commensal gut bacteria collected from both human and mouse. A variety of cross-reactive microbial proteins were identified using LC-MS, of which E. coli derived HSP60 and HSP70 proteins were confirmed to be able to bind to one of the isolated monoclonal antibodies. Mice with high levels of preexisting S2 cross-reactive antibodies mounted higher S protein specific binding antibodies, especially against S2, after being immunized with a SARS-CoV-2 S DNA vaccine. Similarly, we found that levels of preexisting S2 and P144-specific antibodies correlated positively with RBD binding antibody titers after two doses of inactivated SARS-CoV-2 vaccination in human. Collectively, our study revealed an alternative origin of preexisting S2-targeted antibodies and disclosed a previously neglected aspect of the impact of gut microbiota on host anti-SARS-CoV-2 immunity.

A Review of the Role of Oral Microbiome in the Development, Detection, and Management of Head and Neck Squamous Cell Cancers

The role of the microbiome in the development and propagation of head and neck squamous cell cancer (HNSCC) is largely unknown and the surrounding knowledge lags behind what has been discovered related to the microbiome and other malignancies. In this review, the authors performed a structured analysis of the available literature from several databases. The authors discuss the merits and detriments of several studies discussing the microbiome of the structures of the aerodigestive system throughout the development of HNSCC, the role of the microbiome in the development of malignancies (generally and in HNSCC) and clinical applications of the microbiome in HNSCC. Further studies will be needed to adequately describe the relationship between HNSCC and the microbiome, and to push this relationship into a space where it is clinically relevant outside of a research environment.

Microbiomes, Epigenomics, Immune Response, and Splicing Signatures Interplay: Potential Use of Combination of Regulatory Pathways as Targets for Malignant Mesothelioma

Malignant mesotheliomas (MM) are hard to treat malignancies with poor prognosis and high mortality rates. This cancer is highly misdiagnosed in Sub-Saharan African countries. According to literature, the incidence of MM is likely to increase particularly in low-middle-income countries (LMICs). The burden of asbestos-induced diseases was estimated to be about 231,000 per annum. Lack of awareness and implementation of regulatory frameworks to control exposure to asbestos fibers contributes to the expected increase. Exposure to asbestos fibers can lead to cancer initiation by several mechanisms. Asbestos-induced epigenetic modifications of gene expression machinery and non-coding RNAs promote cancer initiation and progression. Furthermore, microbiome-epigenetic interactions control the innate and adaptive immunity causing exacerbation of cancer progression and therapeutic resistance. This review discusses epigenetic mechanisms with more focus on miRNAs and their interaction with the microbiome. The potential use of epigenetic alterations and microbiota as specific biomarkers to aid in the early detection and/or development of therapeutic targets is explored. The advancement of combinatorial therapies to prolong overall patient survival or possible eradication of MM especially if it is detected early is discussed.

Local Breast Microbiota: A "New" Player on the Block

Simple Summary

Microbiota plays a fundamental role in the induction, training and function of the human immune system. The interactions between microbiota and immune cells have consequences in several settings, namely in carcinogenesis but also in anticancer activity. Immunotherapy, already widely used in the treatment of several solid cancers, modulates the action of the immune system, promoting antitumour effects. Recently, there has been a growing interest in studying the microbiota composition as a possible modulator of the tumour microenvironment and consequently of the response to certain therapies such as immunotherapy.

Abstract

The tumour microenvironment (TME) comprises a complex ecosystem of different cell types, including immune cells, cells of the vasculature and lymphatic system, cancer-associated fibroblasts, pericytes, and adipocytes. Cancer proliferation, invasion, metastasis, drug resistance and immune escape are all influenced by the dynamic interaction between cancer cells and TME. Microbes, such as bacteria, fungi, viruses, archaea and protists, found within tumour tissues, constitute the intratumour microbiota, which is tumour type-specific and distinct among patients with different clinical outcomes. Growing evidence reveals a significant relevance of local microbiota in the colon, liver, breast, lung, oral cavity and pancreas carcinogenesis. Moreover, there is a growing interest in the tumour immune microenvironment (TIME) pointed out in several cross-sectional studies on the correlation between microbiota and TME. It is now known that microorganisms have the capacity to change the density and function of anticancer and suppressive immune cells, enabling the promotion of an inflammatory environment. As immunotherapy (such as immune checkpoint inhibitors) is becoming a promising therapy using TIME as a therapeutic target, the analysis and comprehension of local microbiota and its modulating strategies can help improve cancer treatments.

Interaction between microbiota and immunity and its implication in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the world. Besides genetic causes, colonic inflammation is one of the major risk factors for CRC development, which is synergistically regulated by multiple components, including innate and adaptive immune cells, cytokine signaling, and microbiota. The complex interaction between CRC and the gut microbiome has emerged as an important area of current CRC research. Metagenomic profiling has identified a number of prominent CRC-associated bacteria that are enriched in CRC patients, linking the microbiota composition to colitis and cancer development. Some microbiota species have been reported to promote colitis and CRC development in preclinical models, while a few others are identified as immune modulators to induce potent protective immunity against colitis and CRC. Mechanistically, microbiota regulates the activation of different immune cell populations, inflammation, and CRC via crosstalk between innate and adaptive immune signaling pathways, including nuclear factor kappa B (NF-κB), type I interferon, and inflammasome. In this review, we provide an overview of the potential interactions between gut microbiota and host immunity and how their crosstalk could synergistically regulate inflammation and CRC, thus highlighting the potential roles and mechanisms of gut microbiota in the development of microbiota-based therapies to prevent or alleviate colitis and CRC.

The Effect of the Gut Microbiota on Systemic and Anti-Tumor Immunity and Response to Systemic Therapy against Cancer

Gut microbiota can have opposing functions from pro-tumorigenic to anti-tumorigenic effects. Increasing preclinical and clinical evidence suggests that the intestinal microbiota affects cancer patients’ response to immune checkpoint inhibitors (ICIs) immunotherapy, such as anti-programmed cell death protein 1 (PD-1) and its ligand (PD-L1) and anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Microbiota-induced inflammation possibly contributes to tumor growth and cancer development. Microbiota-derived metabolites can also be converted to carcinogenic agents related to genetic mutations and DNA damage in organs such as the colon. However, other attributes of microbiota, such as greater diversity and specific bacterial species and their metabolites, are linked to better clinical outcomes and potentially improved anti-tumor immunity. In addition, the intratumoral microbial composition strongly affects T-cell-mediated cytotoxicity and anti-tumor immune surveillance, adding more complexity to the cancer-microbiome-immune axis. Despite the emerging clinical evidence for the activity of the gut microbiota in immuno-oncology, the fundamental mechanisms of such activity are not well understood. This review provides an overview of underlying mechanisms by which the gut microbiota and its metabolites enhance or suppress anti-tumor immune responses. Understanding such mechanisms allows for better design of microbiome-specific treatment strategies to improve the clinical outcome in cancer patients undergoing systemic therapy.

Fecal Microbes Associated with the Outcomes After Esophagectomy in Patients with Esophageal Cancer

BACKGROUND

Although accumulating evidence suggests that an imbalanced gut microbiota leads to cancer progression, few studies demonstrated the implication in patients who underwent oncologic esophagectomy. This study aimed to elucidate the association between gut microbes and the outcomes after oncologic esophagectomy, as well as the host's inflammatory/nutritional status.

METHODS

Overall, 783 consecutive patients who underwent oncologic esophagectomy were eligible. We investigated the microbiota detected by fecal culture tests and then assessed the association between the gut microbiota and patient characteristics, short-term outcomes, and long-term survival.

RESULTS

Seventeen different species could be cultivated. We comprehensively examined the impact of each detected microbe on survival. The presence of Bacillus species (Bacillus sp.; 26.8%) was associated with favorable prognosis on overall and cancer-specific survival (p = 0.02 and 0.02, respectively). Conversely, the presence of Proteus mirabilis (P. mirabilis; 3.4%) was associated with unfavorable overall and recurrence-free survivals (p = 0.02 and < 0.01, respectively). Multivariate analysis showed that the presence of P. mirabilis was one of the independent prognostic factors for poor recurrence-free survival (p < 0.01). Patients with Bacillus sp. had lower modified Glasgow prognostic score and better response to preoperative treatment than those without (p = 0.01 and 0.03, respectively). Meanwhile, patients with P. mirabilis were significantly associated with higher systemic inflammation scores and increased postoperative pneumonia incidence than those without (p = 0.01 and 0.02, respectively).

CONCLUSIONS

Preoperative fecal microbiota was associated with the host's inflammatory and nutritional status and may influence the outcomes after oncologic esophagectomy.

Outer Membrane Vesicles From The Gut Microbiome Contribute to Tumor Immunity by Eliciting Cross-Reactive T Cells

A growing body of evidence supports the notion that the gut microbiome plays an important role in cancer immunity. However, the underpinning mechanisms remain to be fully elucidated. One attractive hypothesis envisages that among the T cells elicited by the plethora of microbiome proteins a few exist that incidentally recognize neo-epitopes arising from cancer mutations (“molecular mimicry (MM)” hypothesis). To support MM, the human probiotic Escherichia coli Nissle was engineered with the SIINFEKL epitope (OVA-E.coli Nissle) and orally administered to C57BL/6 mice. The treatment with OVA-E.coli Nissle, but not with wild type E. coli Nissle, induced OVA-specific CD8⁺ T cells and inhibited the growth of tumors in mice challenged with B16F10 melanoma cells expressing OVA. The microbiome shotgun sequencing and the sequencing of TCRs from T cells recovered from both lamina propria and tumors provide evidence that the main mechanism of tumor inhibition is mediated by the elicitation at the intestinal site of cross-reacting T cells, which subsequently reach the tumor environment. Importantly, the administration of Outer Membrane Vesicles (OMVs) from engineered E. coli Nissle, as well as from E. coli BL21(DE3)ΔompA, carrying cancer-specific T cell epitopes also elicited epitope-specific T cells in the intestine and inhibited tumor growth. Overall, our data strengthen the important role of MM in tumor immunity and assign a novel function of OMVs in host-pathogen interaction. Moreover, our results pave the way to the exploitation of probiotics and OMVs engineered with tumor specific-antigens as personalized mucosal cancer vaccines.

Current Status and Future Directions of Bacteria-Based Immunotherapy

With the in-depth understanding of the anti-cancer immunity, immunotherapy has become a promising cancer treatment after surgery, radiotherapy, and chemotherapy. As natural immunogenicity substances, some bacteria can preferentially colonize and proliferate inside tumor tissues to interact with the host and exert anti-tumor effect. However, further research is hampered by the infection-associated toxicity and their unpredictable behaviors in vivo. Due to modern advances in genetic engineering, synthetic biology, and material science, modifying bacteria to minimize the toxicity and constructing a bacteria-based immunotherapy platform has become a hotspot in recent research. This review will cover the inherent advantages of unedited bacteria, highlight how bacteria can be engineered to provide greater tumor-targeting properties, enhanced immune-modulation effect, and improved safety. Successful applications of engineered bacteria in cancer immunotherapy or as part of the combination therapy are discussed as well as the bacteria based immunotherapy in different cancer types. In the end, we highlight the future directions and potential opportunities of this emerging field.

BCG therapy downregulates HLA-I on malignant cells to subvert antitumor immune responses in bladder cancer

Patients with high-risk, nonmuscle-invasive bladder cancer (NMIBC) frequently relapse after standard intravesical bacillus Calmette-Guérin (BCG) therapy and may have a dismal outcome. The mechanisms of resistance to such immunotherapy remain poorly understood. Here, using cancer cell lines, freshly resected human bladder tumors, and samples from cohorts of patients with bladder cancer before and after BCG therapy, we demonstrate 2 distinct patterns of immune subversion upon BCG relapse. In the first pattern, intracellular BCG infection of cancer cells induced a posttranscriptional downregulation of HLA-I membrane expression via inhibition of autophagy flux. Patients with HLA-I-deficient cancer cells following BCG therapy had a myeloid immunosuppressive tumor microenvironment (TME) with epithelial-mesenchymal transition (EMT) characteristics and dismal outcomes. Conversely, patients with HLA-I-proficient cancer cells after BCG therapy presented with CD8+ T cell tumor infiltrates, upregulation of inflammatory cytokines, and immune checkpoint-inhibitory molecules. The latter patients had a very favorable outcome. We surmise that HLA-I expression in bladder cancers at relapse following BCG does not result from immunoediting but rather from an immune subversion process directly induced by BCG on cancer cells, which predicts a dismal prognosis. HLA-I scoring of cancer cells by IHC staining can be easily implemented by pathologists in routine practice to stratify future treatment strategies for patients with urothelial cancer.

Immune responses of patients without cancer recurrence after a cancer vaccine over a long term

The present study aimed to clarify the humoral and cellular immune responses of patients with cancer who experienced no recurrence over a long term after receiving a cancer vaccine. The immune kinetics were investigated in response to a personalized peptide vaccination (PPV) among 44 Japanese patients without an active tumor at entry to the vaccination: Lung adenocarcinoma (n=11); colon (n=18); and breast cancer (n=15) (9, 10, 12, 8 and 5 patients with stage I, II, III and IV recurrences, respectively). The patients' immunoglobulin G (IgG) and cytotoxic T lymphocyte (CTL) activities were measured using a multiplexed Luminex assay and an interferon-γ release assay, respectively. There were no severe adverse events related to the PPV other than a grade III injection site reaction. A potent boost in IgG or CTL at the end of the 1st vaccination cycle was observed in 77% of the patients (n=84). The IgG levels were sustained throughout the follow-up period, whereas the CTL levels declined and were transient. A total of 37 of the 44 patients (84%) had no recurrence, with a median follow-up of 67.6 months (interquartile range, 45.6-82.8 months). Overall, the PPV induced long-term humoral immunity with transient cellular immunity in the majority of patients with cancer without an active tumor at their entry to the PPV.

Characterization of the fecal microbiota in gastrointestinal cancer patients and healthy people

BACKGROUND

The incidence and mortality of gastrointestinal (GI) tumors are high in China. Some studies suggest that the gut microbiota is related to the occurrence and development of tumors. At present, there are no prospective studies based on the correlation between gastrointestinal tumors and gut microbiota in the Chinese population. The objective of this report is to characterize the fecal microbiota in healthy control participants and patients with esophageal cancer, gastric cancer, and colorectal cancer.

METHODS

Patients with locally advanced or metastatic esophageal, gastric, and colorectal cancer were enrolled, and healthy people were included as controls. 16S rRNA sequencing was used to analyze the characteristics of fecal microbiota. PICRUSt software was used for functional prediction.

RESULTS

Significant differences in the composition and abundance of fecal microbiota were identified between gastrointestinal cancer patients (n = 130) and healthy controls (n = 147). The abundance of Faecalibacterium prausnitzii, Clostridium clostridioforme and Bifidobacterium adolescent in tumor groups were all significantly lower than in the control group (P < 0.05). The levels of Blautia producta and R. faecis in the gastric (n = 46) and colorectal cancer (n = 44) groups were significantly lower than those in the control group (P < 0.05). The level of Butyricicoccus pullicaecorum in the esophageal cancer (n = 40) and gastric cancer groups was significantly lower than that in the control group (P < 0.05). B. fragilis, Akkermansia muciniphila, Clostridium hathewayi and Alistipes finegoldii were overabundant in the different tumor groups compared with the control (P < 0.05). We observed significant differences in functional metabolism and cell biological function between the tumor and control groups (P < 0.05). Optimal microbial markers were identified on a random forest model and achieved an area under the curve of 85.59% between 130 GI cancer samples and 147 control samples. The respective AUC values were 86.89%, 97.11%, and 79.1% in detecting esophageal cancer, gastric cancer, and colorectal cancer.

CONCLUSIONS

Patients with esophageal or gastric cancers had similar features of fecal bacteria as those with colorectal cancer. The metabolic function of fecal bacteria in the gastrointestinal cancer patients and the healthy controls were different. The microbial signatures may potentially be applied to distinguish GI cancer patients from healthy people as a non-invasive diagnostic biomarker.

Interaction of Gut Microbiota with Endocrine Homeostasis and Thyroid Cancer

The gut microbiota plays a crucial role in healthy individuals as well as in patients with thyroid diseases, including thyroid cancer. Although the prognosis of differentiated thyroid cancer is predictable, that of some poorly differentiated, medullary, and anaplastic thyroid cancers remains unpromising. As the interaction between the gut microbiota and thyroid cancer has been gradually revealed in recent years, the thyroid gland, a crucial endocrine organ, is shown to have a complex connection with the body's metabolism and is involved in inflammation, autoimmunity, or cancer progression. Dysbiosis of the gut microbiota and its metabolites can influence changes in hormone levels and susceptibility to thyroid cancer through multiple pathways. In this review, we focus on the interactions of the gut microbiota with thyroid function diseases and thyroid cancer. In addition, we also discuss some potential new strategies for the prevention and treatment of thyroid disease and thyroid cancer. Our aim is to provide some possible clinical applications of gut microbiota markers for early diagnosis, treatment, and postoperative management of thyroid cancer. These findings were used to establish a better multi-disciplinary treatment and prevention management strategy and to individualize the treatment of patients in relation to their gut microbiota composition and pathological characteristics.

Multi-Omics Approaches for the Prediction of Clinical Endpoints after Immunotherapy in Non-Small Cell Lung Cancer: A Comprehensive Review

Immune checkpoint inhibitors (ICI) have revolutionized the management of locally advanced and advanced non-small lung cancer (NSCLC). With an improvement in the overall survival (OS) as both first- and second-line treatments, ICIs, and especially programmed-death 1 (PD-1) and programmed-death ligands 1 (PD-L1), changed the landscape of thoracic oncology. The PD-L1 level of expression is commonly accepted as the most used biomarker, with both prognostic and predictive values. However, even in a low expression level of PD-L1, response rates remain significant while a significant number of patients will experience hyperprogression or adverse events. The dentification of such subtypes is thus of paramount importance. While several studies focused mainly on the prediction of the PD-L1 expression status, others aimed directly at the development of prediction/prognostic models. The response to ICIs depends on a complex physiopathological cascade, intricating multiple mechanisms from the molecular to the macroscopic level. With the high-throughput extraction of features, omics approaches aim for the most comprehensive assessment of each patient. In this article, we will review the place of the different biomarkers (clinical, biological, genomics, transcriptomics, proteomics and radiomics), their clinical implementation and discuss the most recent trends projecting on the future steps in prediction modeling in NSCLC patients treated with ICI.

From Tumor Cells to Endothelium and Gut Microbiome: A Complex Interaction Favoring the Metastasis Cascade

Metastasis is a complicated process through which tumor cells disseminate to distant organs and adapt to novel tumor microenvironments. This multi-step cascade relies on the accumulation of genetic and epigenetic alterations within the tumor cells as well as the surrounding non-tumor stromal cells. Endothelial cells constitute a major player in promoting metastasis formation either by inducing the growth of tumor cells or by directing them towards dissemination in the blood or lymph. In fact, the direct and indirect interactions between tumor and endothelial cells were shown to activate several mechanisms allowing cancer cells’ invasion and extravasation. On the other side, gastrointestinal cancer development was shown to be associated with the disruption of the gut microbiome. While several proposed mechanisms have been investigated in this regard, gut and tumor-associated microbiota were shown to impact the gut endothelial barrier, increasing the dissemination of bacteria through the systemic circulation. This bacterial dislocation allows the formation of an inflammatory premetastatic niche in the distant organs promoting the metastatic cascade of primary tumors. In this review, we discuss the role of the endothelial cells in the metastatic cascade of tumors. We will focus on the role of the gut vascular barrier in the regulation metastasis. We will also discuss the interaction between this vascular barrier and the gut microbiota enhancing the process of metastasis. In addition, we will try to elucidate the different mechanisms through which this bacterial dislocation prepares the favorable metastatic niche at distant organs allowing the dissemination and successful deposition of tumor cells in the new microenvironments. Finally, and given the promising results of the studies combining immune checkpoint inhibitors with either microbiota alterations or anti-angiogenic therapy in many types of cancer, we will elaborate in this review the complex interaction between these 3 factors and their possible therapeutic combination to optimize response to treatment.

Microbiome in cancer: Role in carcinogenesis and impact in therapeutic strategies

Cancer is the world's second-leading cause of death, and the involvement of microbes in a range of diseases, including cancer, is well established. The gut microbiota is known to play an important role in the host's health and physiology. The gut microbiota and its metabolites may activate immunological and cellular pathways that kill invading pathogens and initiate a cancer-fighting immune response. Cancer is a multiplex illness, characterized by the persistence of several genetic and physiological anomalies in malignant tissue, complicating disease therapy and control. Humans have coevolved with a complex bacterial, fungal, and viral microbiome over millions of years. Specific long-known epidemiological links between certain bacteria and cancer have recently been grasped at the molecular level. Similarly, advances in next-generation sequencing technology have enabled detailed research of microbiomes, such as the human gut microbiome, allowing for the finding of taxonomic and metabolomic linkages between the microbiome and cancer. These investigations have found causative pathways for both microorganisms within tumors and bacteria in various host habitats far from tumors using direct and immunological procedures. Anticancer diagnostic and therapeutic solutions could be developed using this review to tackle the threat of anti-cancer medication resistance as well through the wide-ranging involvement of the microbiota in regulating host metabolic and immunological homeostasis. We reviewed the significance of gut microbiota in cancer initiation as well as cancer prevention. We look at certain microorganisms that may play a role in the development of cancer. Several bacteria with probiotic qualities may be employed as bio-therapeutic agents to re-establish the microbial population and trigger a strong immune response to remove malignancies, and further study into this should be conducted.

Systemic Evaluation of the Effect of Diabetes Mellitus on Breast Cancer in a Mouse Model

Breast cancer complicated with diabetes mellitus (DM) is a common disease. To evaluate the effect of preexisting DM on breast cancer progression without drug interference, we used a streptozotocin (STZ)-induced type 2 diabetes mellitus BALB/c mouse model. We found that 4T1 breast cancer complicated with DM decreased the mouse survival time compared with 4T1-bearing mice. The diversity of gut microbiome was affected by DM. The infiltration of mucosal-associated invariant T cell (MAIT), CD8+ T cell, and CD4+ T cell in the tumor was significantly decreased in the DM-4T1 group compared with the 4T1 group. The transcriptome data of tumor tissues indicated that the expressions of inflammatory C–C chemokine- and metabolism-related genes were greatly changed. The abnormal expression of these genes may be related with the decreased T-cell infiltration in DM-4T1. In conclusion, the gut microbiome and tumor microenvironment of diabetic breast cancer patients have unique features. The effect of diabetes on breast cancer should be considered in the treatment for diabetic breast cancer patients.

Gut microbiota influence immunotherapy responses: mechanisms and therapeutic strategies

The gut microbiota have long been recognized to play a key role in human health and disease. Currently, several lines of evidence from preclinical to clinical research have gradually established that the gut microbiota can modulate antitumor immunity and affect the efficacy of cancer immunotherapies, especially immune checkpoint inhibitors (ICIs). Deciphering the underlying mechanisms reveals that the gut microbiota reprogram the immunity of the tumor microenvironment (TME) by engaging innate and/or adaptive immune cells. Notably, one of the primary modes by which the gut microbiota modulate antitumor immunity is by means of metabolites, which are small molecules that could spread from their initial location of the gut and impact local and systemic antitumor immune response to promote ICI efficiency. Mechanistic exploration provides novel insights for developing rational microbiota-based therapeutic strategies by manipulating gut microbiota, such as fecal microbiota transplantation (FMT), probiotics, engineered microbiomes, and specific microbial metabolites, to augment the efficacy of ICI and advance the age utilization of microbiota precision medicine.

Engineered cellular immunotherapies in cancer and beyond

This year marks the tenth anniversary of cell therapy with chimeric antigen receptor (CAR)-modified T cells for refractory leukemia. The widespread commercial approval of genetically engineered T cells for a variety of blood cancers offers hope for patients with other types of cancer, and the convergence of human genome engineering and cell therapy technology holds great potential for generation of a new class of cellular therapeutics. In this Review, we discuss the goals of cellular immunotherapy in cancer, key challenges facing the field and exciting strategies that are emerging to overcome these obstacles. Finally, we outline how developments in the cancer field are paving the way for cellular immunotherapeutics in other diseases.

Effects of combined OncoTherad immunotherapy and probiotic supplementation on modulating the chronic inflammatory process in colorectal carcinogenesis

This study evaluated the effects of combined OncoTherad immunotherapy and probiotic supplementation on colorectal carcinogenesis chemically induced with 1,2-dimethylhydrazine (DMH) in mice. The animals were randomly allocated in five groups: Control, DMH: did not receive any treatment; DMH + OncoTherad: received weekly I.P. (intraperitoneal) dose of OncoTherad; DMH + Probiotic: received daily administrations via gavage of the functional food (Lactobacillus: acidophilus and paracasei, Bifidobacterium: lactis and bifidum) and DMH + Probiotic + OncoTherad: received the same treatment than the previous groups. After ten weeks of treatment, the large intestine was collected for immunohistochemical analysis of TLR4, MyD88, NF-κB, IL-6, TLR2, TRIF, IRF-3, IFN-γ, Ki-67, KRAS, IL-10, and TGF-β. For the statistical analysis, the variance tests (ANOVA) and Kruskal-Wallis were used and significance set at p < 0.05. Probiotic supplementation associated with the OncoTherad were able to modulate weight loss, stimulate the canonical signaling pathway TLR2/TLR4 (MyD88-dependent), reduce the non-canonical signaling pathway (TRIF-dependent), attenuate the proliferative pathway mediated by Ki-67 and KRAS oncogene, and stimulate the production of IL-10 and TGF-β cytokines. Thus, the association of OncoTherad and probiotic supplementation has shown important immudomulatory effects and could be considered a potential new therapeutic approach for colorectal cancer after further investigations.

Diverse prebiotic effects of isomaltodextrins with different glycosidic linkages and molecular weights on human gut bacteria in vitro

Isomaltodextrin (IMD) is a novel dietary fiber enzymatically produced by reconstructing the molecular chain structure of starch using glycosyltransferases. In this study, the specific prebiotic effects of α-1,6 linear and α-1,2 or α-1,3 branched IMDs with different molecular weights (Mw) on human intestinal bacteria were investigated by pure culture of single strains and mixed fermentation of human fecal microflora in vitro. The results showed that α-1,6 linear IMDs markedly promoted beneficial Bifidobacterium and Lactobacillus in both pure culture and mixed fermentation. α-1,3 branching exhibited similar selectivity with α-1,6 linkage but yielded more butyrate in pure cultures. In contrast, IMDs containing α-1,2 branches were utilized efficiently only during mixed fermentation, which was speculated to result from metabolic cross-feeding. Regarding Mw, IMDs with lower Mw showed better prebiotic effects in pure cultures but no differences in mixed culture. These findings provide a theoretical basis for their application as functional foods.

Crosstalk between the gut microbiome and clinical response in locally advanced thoracic esophageal squamous cell carcinoma during neoadjuvant camrelizumab and chemotherapy

Background

The gut microbiome is associated with the response to immunotherapy in a variety of advanced cancers. However, the influence of the gut microbiome on locally advanced esophageal squamous cell carcinoma (ESCC) during programmed cell death protein 1 (PD-1) antibody immunotherapy plus chemotherapy is not clearly demonstrated. To explore the crosstalk between the gut microbiome and clinical response in locally advanced thoracic ESCC during neoadjuvant camrelizumab and chemotherapy

Methods

Patients who were diagnosed with locally advanced thoracic ESCC and had not received treatment were enrolled. The treatment regimen was two cycles of camrelizumab combined with carboplatin and albumin paclitaxel before surgery. The research endpoints were pathological complete response (pCR) and major pathological response (MPR). Fecal samples were collected at three time points: before neoadjuvant therapy, after two cycles of neoadjuvant therapy, and after surgery. We performed 16S ribosomal ribonucleic acid (rRNA) V3–V4 sequencing of the gene amplicons of fecal samples, as well as bacterial diversity and differential abundance analyses.

Results

A total of 46 patients were recruited, and 44, 42, and 35 fecal samples were collected at the three time points, respectively. Statistically significant differences were observed in the amplicon sequence variant (ASV)-level alpha diversity indices, including Chao1, Shannon, and Good’s coverage, between the three time points. The non-pCR-enriched gut microbiota included Proteobacteria, Dialister, Aeromonadales, Pseudomonadales, Thermi, Deinococci, Moraxellaceae, Rhodocyclales, Rhodocyclaceae, and Acinetobacter. The non-MPR-enriched gut microbiota included Pseudomonadales and the mitochondria family. The MPR-enriched gut microbiota included the Barnesiellaceae, Pyramidobacter, Dethiosulfovibrionaceae, Odoribacteraceae, Butyricimonas, Prevotella, Barnesiella, and Odoribacter. Patients with ≥3 grade adverse events (AEs) exhibited enrichment in the Succiniclasticum, Nakamurella, Rhizobium, Granulicella, Phyllobacteriaceae, Pelagibacteraceae, Actinosynnemataceae, Aquirestis, Flavisolibacter, Chelativorans, Coxiellaceae Acidicapsa, Acidobacteriaceae, Lentzea, Staphylococcus, Plesiomonas, Dysgonomonas, Pseudonocardia, and Ellin6075.

Conclusions

We found that the diversity of the gut microbiome declined after neoadjuvant PD-1 antibody immunotherapy plus chemotherapy and surgery. Patients with pCR had different types and proportions of gut microbiota before treatment compared to those without pCR. We also observed the difference between patients with or without ≥ grade 3 AEs. The taxonomic features of the gut microbiome are potential biomarkers that could predict the pathological response and AEs.

Novel directions of precision oncology: circulating microbial DNA emerging in cancer-microbiome areas

Microbiome research has extended into the cancer area in the past decades. Microbes can affect oncogenesis, progression, and treatment response through various mechanisms, including direct regulation and indirect impacts. Microbiota-associated detection methods and agents have been developed to facilitate cancer diagnosis and therapy. Additionally, the cancer microbiome has recently been redefined. The identification of intra-tumoral microbes and cancer-related circulating microbial DNA (cmDNA) has promoted novel research in the cancer-microbiome area. In this review, we define the human system of commensal microbes and the cancer microbiome from a brand-new perspective and emphasize the potential value of cmDNA as a promising biomarker in cancer liquid biopsy. We outline all existing studies on the relationship between cmDNA and cancer and the outlook for potential preclinical and clinical applications of cmDNA in cancer precision medicine, as well as critical problems to be overcome in this burgeoning field.

Gut microbiota and immunity relevance in eubiosis and dysbiosis

Human gut is colonized by numerous microorganisms, in which bacteria present the highest proportion of this colonization that live in a symbiotic relationship with the host. This microbial collection is commonly known as the microbiota. The gut microbiota can mediate gut epithelial and immune cells interaction through vitamins synthesis or metabolic products. The microbiota plays a vital role in growth and development of the main components of human’s adaptive and innate immune system, while the immune system regulates host-microbe symbiosis. On the other hand, negative alteration in gut microbiota composition or gut dysbiosis, can disturb immune responses. This review highlights the gut microbiota-immune system cross-talk in both eubiosis and dysbiosis.

Biomarkers of response to PD-1 pathway blockade

The binding of T cell immune checkpoint proteins programmed death 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) to their ligands allows immune evasion by tumours. The development of therapeutic antibodies, termed checkpoint inhibitors, that bind these molecules or their ligands, has provided a means to release this brake on the host anti-tumour immune response. However, these drugs are costly, are associated with potentially severe side effects, and only benefit a small subset of patients. It is therefore important to identify biomarkers that discriminate between responders and non-responders. This review discusses the determinants for a successful response to antibodies that bind PD-1 or its ligand PD-L1, dividing them into markers found in the tumour biopsy and those in non-tumour samples. It provides an update on the established predictive biomarkers (tumour PD-L1 expression, tumour mismatch repair deficiency and tumour mutational burden) and assesses the evidence for new potential biomarkers.

The role of microbiota and immune system crosstalk in cancer development and therapy

Cancer is a multifactorial disease that is the second leading cause of death after cardiovascular disease in the world. In recent years, microbiota's role in the regulation and homeostasis of the immune system has been considered. Moreover, the immune system can affect the microbiota content. These interactions are critical to the functioning of the immune system. Numerous studies in animal and human models have shown the association of changes in microbiota components with the formation of an inhibitory microenvironment in the tumor and its escape from the immune system. Microbiota also plays a crucial role in the success of various anti-tumor treatments, and its modification leads to success in cancer treatment. The success of anti-tumor therapies that directly target the immune system, such as immune checkpoint blockade and T cell therapy, is also affected by the patient's microbiota composition. It seems that in addition to examining the patient's genetics, precision medicine should pay attention to the patient's microbiota in choosing the appropriate treatment method, and together with usual anti-tumor therapies, microbiota may be modified. This review discusses various aspects of the relationship between microbiota and anti-tumor immunity and its successful treatment.

The promise of the gut microbiome as part of individualized treatment strategies

Variability in disease presentation, progression and treatment response has been a central challenge in medicine. Although variability in host factors and genetics are important, it has become evident that the gut microbiome, with its vast genetic and metabolic diversity, must be considered in moving towards individualized treatment. In this Review, we discuss six broad disease groups: infectious disease, cancer, metabolic disease, cardiovascular disease, autoimmune or inflammatory disease, and allergic and atopic diseases. We highlight current knowledge on the gut microbiome in disease pathogenesis and prognosis, efficacy, and treatment-related adverse events and its promise for stratifying existing treatments and as a source of novel therapies. The Review is not meant to be comprehensive for each disease state but rather highlights the potential implications of the microbiome as a tool to individualize treatment strategies in clinical practice. Although early, the outlook is optimistic but challenges need to be overcome before clinical implementation, including improved understanding of underlying mechanisms, longitudinal studies with multiple data layers reflecting gut microbiome and host response, standardized approaches to testing and reporting, and validation in larger cohorts. Given progress in the microbiome field with concurrent basic and clinical studies, the microbiome will likely become an integral part of clinical care within the next decade.

Relationship of the lung microbiome with PD-L1 expression and immunotherapy response in lung cancer

Background

Lung cancer is the primary cause of cancer-related deaths worldwide. The human lung serves as a niche to a unique and dynamic bacterial community that is related to the development of multiple diseases. Here, we investigated the differences in the lung microbiomes of patients with lung cancer.

Methods

16S rRNA sequencing was performed to evaluate the respiratory tract microbiome present in the bronchoalveolar lavage fluid. Patients were stratified based on programmed death-ligand 1 (PD-L1) expression levels and immunotherapy responses.

Results

In total, 84 patients were prospectively analyzed, of which 59 showed low (< 10%), and 25 showed high (≥ 10%) PD-L1 expression levels. The alpha and beta diversities did not significantly differ between the two groups. Veillonella dispar was dominant in the high-PD-L1 group; the population of Neisseria was significantly higher in the low-PD-L1 group than in the high-PD-L1 group. In the immunotherapy responder group, V. dispar was dominant, while Haemophilus influenzae and Neisseria perflava were dominant in the non-responder group.

Conclusion

The abundances of Neisseria and V. dispar differed significantly in relation to PD-L1 expression levels and immunotherapy responses.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01919-1.

Novel emerging biomarkers to immunotherapy in kidney cancer

The treatment of metastatic renal cell carcinoma has significantly evolved in recent years, particularly with the advent of novel immune checkpoint inhibitors (ICI). Despite the striking benefits observed on a population level, outcomes vary and some patients do not respond to ICI-based regimens, ultimately require salvage therapies. An ever deeper understanding of the disease biology mediated by the development of multiple high-throughput molecular omics has led to significant progress in biomarkers discovery. But despite growing insights into the molecular underpinnings of the tumor microenvironment, biomarkers have not been integrated successfully into clinical practice. In this review, we discuss some of the novel emerging predictive biomarkers to ICIs in metastatic renal cell carcinoma.

Cell/Bacteria-Based Bioactive Materials for Cancer Immune Modulation and Precision Therapy

Numerous clinical trials for cancer precision medicine research are limited due to the drug resistance, side effects, and low efficacy. Unsatisfactory outcomes are often caused by complex physiologic barriers and abnormal immune events in tumors, such as tumor target alterations and immunosuppression. Cell/bacteria-derived materials with unique bioactive properties have emerged as attractive tools for personalized therapy in cancer. Naturally derived bioactive materials, such as cell and bacterial therapeutic agents with native tropism or good biocompatibility, can precisely target tumors and effectively modulate immune microenvironments to inhibit tumors. Here, the recent advances in the development of cell/bacteria-based bioactive materials for immune modulation and precision therapy in cancer are summarized. Cell/bacterial constituents, including cell membranes, bacterial vesicles, and other active substances have inherited their unique targeting properties and antitumor capabilities. Strategies for engineering living cell/bacteria to overcome complex biological barriers and immunosuppression to promote antitumor efficacy are also summarized. Moreover, past and ongoing trials involving personalized bioactive materials and promising agents such as cell/bacteria-based micro/nano-biorobotics are further discussed, which may become another powerful tool for treatment in the near future.

Laboratory biomarkers of an effective antitumor immune response. Clinical significance

The modern checkpoint inhibitors block the programmed death-1 receptor and its ligand, cytotoxic T-lymphocyte-associated antigen 4 on tumor cells and lymphocytes, that induces cytotoxic reactions. Nowadays, there are no approved clinical and laboratory predictor markers of immune therapy efficacy, which would allow a more personalized approach to patient selection and treatment. The aim of this review is to analyze possible biomarkers of efficacy for treatment with checkpoint inhibitors according to the pathogenic mechanisms of drug action. The review revealed possible predictive biomarkers, that could be classified to 3 groups: biomarkers of high mutagenic potential of the tumor, biomarkers of high activity of adaptive immunity, biomarkers of low activity of the tumor microenvironment. The determination of the described markers before the start of therapy can be used to formulate a treatment regimen, in which the use of various immunomodulatory drugs, inhibitors of proinflammatory cytokines, angiogenic molecules, and probiotics can be considered.

Commensal Bifidobacterium Strains Enhance the Efficacy of Neo-Epitope Based Cancer Vaccines

A large body of data both in animals and humans demonstrates that the gut microbiome plays a fundamental role in cancer immunity and in determining the efficacy of cancer immunotherapy. In this work, we have investigated whether and to what extent the gut microbiome can influence the antitumor activity of neo-epitope-based cancer vaccines in a BALB/c-CT26 cancer mouse model. Similarly to that observed in the C57BL/6-B16 model, Bifidobacterium administration per se has a beneficial effect on CT26 tumor inhibition. Furthermore, the combination of Bifidobacterium administration and vaccination resulted in a protection which was superior to vaccination alone and to Bifidobacterium administration alone, and correlated with an increase in the frequency of vaccine-specific T cells. The gut microbiome analysis by 16S rRNA gene sequencing and shotgun metagenomics showed that tumor challenge rapidly altered the microbiome population, with Muribaculaceae being enriched and Lachnospiraceae being reduced. Over time, the population of Muribaculaceae progressively reduced while the Lachnospiraceae population increased—a trend that appeared to be retarded by the oral administration of Bifidobacterium. Interestingly, in some Bacteroidales, Prevotella and Muribaculacee species we identified sequences highly homologous to immunogenic neo-epitopes of CT26 cells, supporting the possible role of “molecular mimicry” in anticancer immunity. Our data strengthen the importance of the microbiome in cancer immunity and suggests a microbiome-based strategy to potentiate neo-epitope-based cancer vaccines.

Microbiota, Bacterial Carbonic Anhydrases, and Modulators of Their Activity: Links to Human Diseases?

The involvement of the human microbiome is crucial for different host functions such as protection, metabolism, reproduction, and especially immunity. However, both endogenous and exogenous factors can affect the balance of the microbiota, creating a state of dysbiosis, which can start various gastrointestinal or systemic diseases. The challenge of future medicine is to remodel the intestinal microbiota to bring it back to healthy equilibrium (eubiosis) and, thus, counteract its negative role in the diseases' onset. The shaping of the microbiota is currently practiced in different ways ranging from diet (or use of prebiotics, probiotics, and synbiotics) to phage therapy and antibiotics, including microbiota fecal transplantation. Furthermore, because microbiota modulation is a capillary process, and because many microbiota bacteria (both beneficial and pathogenic) have carbonic anhydrases (specifically the four classes α, β, γ, and ι), we believe that the use of CA inhibitors and activators can open up new therapeutic strategies for many diseases associated with microbial dysbiosis, such as the various gastrointestinal disorders and the same colorectal cancer.

Spot-light on microbiota in obesity and cancer

Over the last few years, the complexity and diversity of gut microbiota within and across individuals has been detailed in relation to human health. Further, understanding of the bidirectional association between gut microbiota and metabolic disorders has highlighted a complimentary, yet crucial role for microbiota in the onset and progression of obesity-related cancers. While strategies for cancer prevention and cure are known to work efficiently when supported by healthy diet and lifestyle choices and physical activity, emerging evidence suggests that the complex interplay relating microbiota both to neoplastic and metabolic diseases could aid strategies for cancer treatment and outcomes. This review will explore the experimental and clinical grounds supporting the functional role of gut microbiota in the pathophysiology and progression of cancers in relation to obesity and its metabolic correlates. Therapeutic approaches aiding microbiota restoration in connection with cancer treatments will be discussed.

Fusobacterium nucleatum predicts a high risk of metastasis for esophageal squamous cell carcinoma

Background

Esophageal squamous cell carcinoma (ESCC) is the major type of esophageal cancer in China. The role of the bacteria present in ESCC tissue in neoplastic progression has not been fully elucidated. This study aimed to uncover different bacterial communities in ESCC tissues and examine the correlation between the abundance of the esophageal flora and clinicopathologic characteristics of ESCC.

Results

Microorganisms in tumors and normal tissues showed obvious clustering characteristics. The abundance of Fusobacterium (P = 0.0052) was increased in tumor tissues. The high level of Fusobacterium nucleatum was significantly associated with pT stage (P = 0.039) and clinical stage (P = 0.0039). The WES data showed that COL22A1, TRBV10–1, CSMD3, SCN7A and PSG11 were present in only the F. nucleatum-positive ESCC samples. GO and protein domain enrichment results suggested that epidermal growth factor might be involved in the regulation of cell apoptosis in F. nucleatum-positive ESCC. Both a higher mutational burden and F. nucleatum-positive was observed in tumors with metastasis than in tumors without metastasis.

Conclusion

F. nucleatum is closely related to the pT stage and clinical stage of ESCC. The abundance of F. nucleatum and tumor mutation burden may be used in combination as a potential method to predict metastasis in ESCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02352-6.

Influence of gut and intratumoral microbiota on the immune microenvironment and anti-cancer therapy

Microbiota has been implicated in the regulation of tumor progression and therapeutic efficacy. However, the effect of microbiota on disease progression is context dependent, differing according to tumor types, therapeutic regimens, and composition of the microbiota, calling for a deeper understanding of host-microbiome interactions. Previous studies have demonstrated that gut microbiota influences disease progression by regulating local and systemic immunity. Notably, with the advent of next-generation sequencing technology, intratumoral microbiota has also been found and constitutes an important component of the tumor microenvironment. In this review, we summarize recent knowledge about the identification of intra-tumor microbiota and discuss the role of gut and intratumoral microbiota in solid tumors in the angle of immune microenvironment interaction. Furthermore, we discuss how these findings may benefit current anti-cancer approaches. Key problems to be solved in ongoing and future research are highlighted.

Microbial community alteration in tongue squamous cell carcinoma

Tongue squamous cell carcinoma (TSCC) is the most common oral cavity malignancy. The role of the microbial community in TSCC development and progression is unclear. In the present study, 23 patients with TSCC were recruited. Tissue DNA was extracted from cancer and paracancerous normal tissues from all participants. Next-generation 16S rDNA amplicon sequencing and functional prediction were applied for taxonomic analysis. Alpha diversity measurements using the Shannon and Simpson diversity indexes indicated a significant increase in the microbiotic diversity of cancer samples (Shannon index: P = 0.001, Simpson index: P = 0.015); otherwise, no differences were found when using observed operational taxonomic units (OTUs) and Chao1 index (observed OTUs: P = 0.261, Chao1 index: P = 0.054). The dominant phyla of the microbiota included Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria, and Fusobacteria. Multivariate analysis of variance (Adonis) and nonparametric analysis of similarities (ANOSIM) based on unweighted unifrac distances demonstrated differences in the bacterial community structure between the two groups (P = 0.001 for Adonis, P = 0.001 for ANOSIM). Compared with the normal samples, Neisseria, Streptococcus, and Actinomyces levels decreased significantly in cancer samples. Co-occurrence network analysis implied that the bacterial community in cancer was more conserved than that in normal tissue. Matched-pair analysis of cancer and control samples revealed a significant alteration in the relative abundance of specific taxa. These findings will enrich our knowledge of the association between the oral microbial community and TSCC. Further experiments should investigate the potential carcinogenic mechanism of microbial community alterations in TSCC. KEY POINTS: • Microbial community role in tongue squamous cell carcinoma. • Significant alteration of microbiome found between cancer and normal tissues. • Microbial community alteration and potential carcinogenic mechanism.

The role of the tumor microbe microenvironment in the tumor immune microenvironment: bystander, activator, or inhibitor?

The efficacy of cancer immunotherapy largely depends on the tumor microenvironment, especially the tumor immune microenvironment. Emerging studies have claimed that microbes reside within tumor cells and immune cells, suggesting that these microbes can impact the state of the tumor immune microenvironment. For the first time, this review delineates the landscape of intra-tumoral microbes and their products, herein defined as the tumor microbe microenvironment. The role of the tumor microbe microenvironment in the tumor immune microenvironment is multifaceted: either as an immune activator, inhibitor, or bystander. The underlying mechanisms include: (I) the presentation of microbial antigens by cancer cells and immune cells, (II) microbial antigens mimicry shared with tumor antigens, (III) microbe-induced immunogenic cell death, (IV) microbial adjuvanticity mediated by pattern recognition receptors, (V) microbe-derived metabolites, and (VI) microbial stimulation of inhibitory checkpoints. The review further suggests the use of potential modulation strategies of the tumor microbe microenvironment to enhance the efficacy and reduce the adverse effects of checkpoint inhibitors. Lastly, the review highlights some critical questions awaiting to be answered in this field and provides possible solutions. Overall, the tumor microbe microenvironment modulates the tumor immune microenvironment, making it a potential target for improving immunotherapy. It is a novel field facing major challenges and deserves further exploration.

Microbiome and cancer

The human microbiome constitutes a complex multikingdom community that symbiotically interacts with the host across multiple body sites. Host-microbiome interactions impact multiple physiological processes and a variety of multifactorial disease conditions. In the past decade, microbiome communities have been suggested to influence the development, progression, metastasis formation, and treatment response of multiple cancer types. While causal evidence of microbial impacts on cancer biology is only beginning to be unraveled, enhanced molecular understanding of such cancer-modulating interactions and impacts on cancer treatment are considered of major scientific importance and clinical relevance. In this review, we describe the molecular pathogenic mechanisms shared throughout microbial niches that contribute to the initiation and progression of cancer. We highlight advances, limitations, challenges, and prospects in understanding how the microbiome may causally impact cancer and its treatment responsiveness, and how microorganisms or their secreted bioactive metabolites may be potentially harnessed and targeted as precision cancer therapeutics.

Role of UPR Sensor Activation in Cell Death-Survival Decision of Colon Cancer Cells Stressed by DPE Treatment

Polyphenols have been shown to possess several beneficial properties, including properties involved in the prevention or treatment of cancer. Among these polyphenols, a leading role is played by dihydroxyphenylethanol (DPE), the most powerful antioxidant compound contained in the olive oil. DPE has been previously reported to induce endoplasmic reticulum (ER) stress and to reduce cell survival in colon cancer, one of the most common and aggressive cancers in developed countries. In this study, we further investigated the activation of UPR by DPE and explored the roles of the three UPR sensors, inositol-requiring enzyme (IRE) 1 alpha, protein kinase RNA-like endoplasmic reticulum kinase (PERK), and activating transcription factor (ATF6), in the cell death-survival decision of wt and mutp53 colon cancer cells and the underlying mechanisms involved. We also unveiled a new interplay between ATF6 and wt, as well as mutp53, which may have important implications in cancer therapy.

Resistance to immunotherapy in human malignancies: Mechanisms, research progresses, challenges, and opportunities

Despite remarkable advances in different types of cancer therapies, an effective therapeutic strategy is still a major and significant challenge. One of the most promising approaches in this regard is immunotherapy, which takes advantage of the patients' immune system; however, the many mechanisms that cancerous cells harbor to extend their survival make it impossible to gain perfect eradication of tumors. The response rate to cancer immunotherapies, especially checkpoint inhibitors and adoptive T cell therapy, substantially differs in various cancer types with the highest rates in advanced melanoma and non-small cell lung cancer. Indeed, the lack of response in many tumors indicates primary resistance that can originate from either tumor cells (intrinsic) or tumor microenvironment (extrinsic). On the other hand, some tumors show an initial response to immunotherapy followed by relapse in few months (acquired resistance). Understanding the underlying molecular mechanisms of immunotherapy resistance makes it possible to develop effective strategies to overcome this hurdle and boost therapy outcomes. In this review, we take a look at immunotherapy strategies and go through a number of primary and acquired resistance mechanisms. Also, we present various ongoing methods to overcoming resistance and introduce some promising fields to improve the outcome of immunotherapy in patients affected with cancer.

PD-1/PD-L1 inhibitors-based treatment for advanced renal cell carcinoma: Mechanisms affecting efficacy and combination therapies

With the widespread use of PD-1/PD-L1 monoclonal antibodies (mAbs) in the treatment of multiple malignant tumors, they were also gradually applied to advanced renal cell carcinoma (aRCC). Nowadays, multiple PD-1/PD-L1 mAbs, such as nivolumab, avelumab, and pembrolizumab, have achieved considerable efficacy in clinical trials. However, due to the primary, adaptive, and acquired resistance to these mAbs, the efficacy of this immunotherapy is not satisfactory. Theories also vary as to why the difference in efficacy occurs. The alterations of PD-L1 expression and the interference of cellular immunity may affect the efficacy. These mechanisms demand to be revealed to achieve a sustained and complete objective response in patients with aRCC. Tyrosine kinase inhibitors have been proven to have synergistic mechanisms with PD-1/PD-L1 mAb in the treatment of aRCC, and CTLA-4 mAb has been shown to have a non-redundant effect with PD-1/PD-L1 mAb to enhance efficacy. Although combinations with targeted agents or other checkpoint mAbs have yielded enhanced clinical outcomes in multiple clinical trials nowadays, the potential of PD-1/PD-L1 mAbs still has a large development space. More potential mechanisms that affect the efficacy demand to be developed and transformed into the clinical treatment of aRCC to search for possible combination regimens. We elucidate these mechanisms in RCC and present existing combination therapies applied in clinical trials. This may help physicians' select treatment options for patients with refractory kidney cancer.

Microbiota-Centered Interventions: The Next Breakthrough in Immuno-Oncology?

The cancer-immune dialogue subject to immuno-oncological intervention is profoundly influenced by microenvironmental factors. Indeed, the mucosal microbiota-and more specifically, the intestinal ecosystem-influences the tone of anticancer immune responses and the clinical benefit of immunotherapy. Antibiotics blunt the efficacy of immune checkpoint inhibitors (ICI), and fecal microbial transplantation may restore responsiveness of ICI-resistant melanoma. Here, we review the yin and yang of intestinal bacteria at the crossroads between the intestinal barrier, metabolism, and local or systemic immune responses during anticancer therapies. We discuss diagnostic tools to identify gut dysbiosis and the future prospects of microbiota-based therapeutic interventions. SIGNIFICANCE: Given the recent proof of concept of the potential efficacy of fecal microbial transplantation in patients with melanoma primarily resistant to PD-1 blockade, it is timely to discuss how and why antibiotics compromise the efficacy of cancer immunotherapy, describe the balance between beneficial and harmful microbial species in play during therapies, and introduce the potential for microbiota-centered interventions for the future of immuno-oncology.

The Role of Gut Microbiota in Overcoming Resistance to Checkpoint Inhibitors in Cancer Patients: Mechanisms and Challenges

The introduction of immune checkpoint inhibitors has constituted a major revolution in the treatment of patients with cancer. In contrast with the traditional cytotoxic therapies that directly kill tumor cells, this treatment modality enhances the ability of the host’s immune system to recognize and target cancerous cells. While immune checkpoint inhibitors have been effective across multiple cancer types, overcoming resistance remains a key area of ongoing research. The gut microbiota and its role in cancer immunosurveillance have recently become a major field of study. Gut microbiota has been shown to have direct and systemic effects on cancer pathogenesis and hosts anti-tumor immune response. Many studies have also shown that the host microbiota profile plays an essential role in the response to immunotherapy, especially immune checkpoint inhibitors. As such, modulating this microbial environment has offered a potential path to overcome the resistance to immune checkpoint inhibitors. In this review, we will talk about the role of microbiota in cancer pathogenesis and immune-system activity. We will also discuss preclinical and clinical studies that have increased our understanding about the roles and the mechanisms through which microbiota influences the response to treatment with immune checkpoint inhibitors.

Microbes in gynecologic cancers: Causes or consequences and therapeutic potential

Gynecologic cancers, starting in the reproductive organs of females, include cancer of cervix, endometrium, ovary commonly and vagina and vulva rarely. The changes in the composition of microbiome in gut and vagina affect immune and metabolic signaling of the host cells resulting in chronic inflammation, angiogenesis, cellular proliferation, genome instability, epithelial barrier breach and metabolic dysregulation that may lead to the onset or aggravated progression of gynecologic cancers. While microbiome in gynecologic cancers is just at horizon, certain significant microbiome signature associations have been found. Cervical cancer is accompanied with high loads of human papillomavirus, Fusobacteria and Sneathia species; endometrial cancer is reported to have presence of Atopobium vaginae and Porphyromonas species and significantly elevated levels of Proteobacteria and Firmicutes phylum bacteria, with Chlamydia trachomatis, Lactobacillus and Mycobacterium reported in ovarian cancer. Balancing microbiome composition in gynecologic cancers has the potential to be used as a therapeutic target. For example, the Lactobacillus species may play an important role in blocking adhesions of incursive pathogens to vaginal epithelium by lowering the pH, producing bacteriocins and employing competitive exclusions. The optimum or personalized balance of the microbiota can be maintained using pre- and probiotics, and fecal microbiota transplantations loaded with specific bacteria. Current evidence strongly suggest that a healthy microbiome can train and trigger the body's immune response to attack various gynecologic cancers. Furthermore, microbiome modulations can potentially contribute to improvements in immuno-oncology therapies.

Cancer Immunotherapies: From Efficacy to Resistance Mechanisms - Not Only Checkpoint Matters

The immunotherapeutic treatment of various cancers with an increasing number of immune checkpoint inhibitors (ICIs) has profoundly improved the clinical management of advanced diseases. However, just a fraction of patients clinically responds to and benefits from the mentioned therapies; a large proportion of patients do not respond or quickly become resistant, and hyper- and pseudoprogression occur in certain patient populations. Furthermore, no effective predictive factors have been clearly screened or defined. In this review, we discuss factors underlying the elucidation of potential immunotherapeutic resistance mechanisms and the identification of predictive factors for immunotherapeutic responses. Considering the heterogeneity of tumours and the complex immune microenvironment (composition of various immune cell subtypes, disease processes, and lines of treatment), checkpoint expression levels may not be the only factors underlying immunotherapy difficulty and resistance. Researchers should consider the tumour microenvironment (TME) landscape in greater depth from the aspect of not only immune cells but also the tumour histology, molecular subtype, clonal heterogeneity and evolution as well as micro-changes in the fine structural features of the tumour area, such as myeloid cell polarization, fibroblast clusters and tertiary lymphoid structure formation. A comprehensive analysis of the immune and molecular profiles of tumour lesions is needed to determine the potential predictive value of the immune landscape on immunotherapeutic responses, and precision medicine has become more important.

Regulation and Functions of Protumoral Unconventional T Cells in Solid Tumors

The vast majority of studies on T cell biology in tumor immunity have focused on peptide-reactive conventional T cells that are restricted to polymorphic major histocompatibility complex molecules. However, emerging evidence indicated that unconventional T cells, including γδ T cells, natural killer T (NKT) cells and mucosal-associated invariant T (MAIT) cells are also involved in tumor immunity. Unconventional T cells span the innate-adaptive continuum and possess the unique ability to rapidly react to nonpeptide antigens via their conserved T cell receptors (TCRs) and/or to activating cytokines to orchestrate many aspects of the immune response. Since unconventional T cell lineages comprise discrete functional subsets, they can mediate both anti- and protumoral activities. Here, we review the current understanding of the functions and regulatory mechanisms of protumoral unconventional T cell subsets in the tumor environment. We also discuss the therapeutic potential of these deleterious subsets in solid cancers and why further feasibility studies are warranted.