The Function and Molecular Mechanism of Commensal Microbiome in Promoting Malignant Progression of Lung Cancer

Lung commensal bacteria promote lung cancer progression through NK cell-mediated immunosuppressive microenvironment

Symbiotic microbiota pervades the majority of the human body's organs and tissues, functioning as crucial regulators of both health maintenance and disease progression. Pertinently, lung adenocarcinoma has been indisputably linked to chronic inflammation. However, the precipitators that instigate such inflammation, along with the particular immune mediators involved, remain enigmatic and warrant extensive exploration. This research revealed a significant variance exists in the commensal bacteria between lung cancer tissues and their normal counterparts. This holds true for both clinical patients and mice, where both the diversity and abundance of bacteria in tumor tissues significantly surpass those in normal tissues. It has been demonstrated that disturbances in pulmonary commensal bacteria can stimulate the proliferation of tumor cells. Mechanistically, we suggest that lung bacteria may promote the expression of the NK cell immunosuppressive molecule TIGIT along with the secretion of IL-2 and IFN-γ. This consequently mediates alterations in the immunosuppressive microenvironment, thereby fostering tumor proliferation.

A Perspective on Lung Cancer and Lung Microbiome: Insight on Immunity

BACKGROUND

Although the carcinogenic potential of microbes has long been recognized, their significance may have been underestimated. Currently, the connection between microbiota and cancer is under extensive research. The lung microbiota may serve as a proxy for the state of lung health based on its crucial role in preserving lung hemostasis.

OBJECTIVES

This review tried to outline the state of our understanding of the contribution of lung microbiome and lung cancer.

METHODS

A literature search was performed using PubMed, Google Scholar, and Scopus databases for recent research focusing on the development and possible pathogenesis of lung microbiome and lung cancer.

RESULTS

Early research on lung cancer indicated that dysbiosis significantly impacted the development and spread of the tumor. As a result of these findings, the study of the lung microbiota as a possible therapeutic target and diagnostic marker has accelerated. Early-stage disease diagnostic biomarkers could be represented as microbiota profiles. Additionally, the microbiome is involved in anticancer therapy. There are limited studies on lung microbiota, and most microbiome studies commonly concentrate on the gut microbiota. A proper understanding of lung microbiota can have several potential therapeutic approaches. Therefore, more studies in this field may initiate remarkable advancements in microbiome-dependent treatment.

CONCLUSION

Convincing data from studies on both humans and animals indicates that the microbiota might play a role in cancer initiation, influenced by internal and environmental factors of the host. Notably, the lung harbors its microbiome, as do lung cancers. In general view, it seems microbiome diversity in lung cancer patients is reduced. Meanwhile, some genera were increased in lung cancer patients in comparison with a noncancerous population (such as Streptococcus genus), and some of them were decreased (Granulicatella adiacens, G. adiacens). Furthermore, research on the microbiome-carcinogenesis relationship is still in its infancy, and much remains to be fully understood.

Metagenomic next-generation sequencing for lung cancer low respiratory tract infections diagnosis and characterizing microbiome features

Background

The capability of mNGS in diagnosing suspected LRTIs and characterizing the respiratory microbiome in lung cancer patients requires further evaluation.

Methods

This study evaluated mNGS diagnostic performance and utilized background microbial sequences to characterize LRT microbiome in these patients. GSVA was used to analyze the potential functions of identified genera.

Results

Bacteria were the most common pathogens (n=74) in LRTIs of lung cancer patients, and polymicrobial infections predominated compared to monomicrobial infections (p<0.001). In diagnosing LRTIs in lung cancer patients, the pathogen detection rate of mNGS (83.3%, 70/84) was significantly higher than that of sputum culture (34.5%, 29/84) (p<0.001). This result was consistent with that of non-lung cancer patients (p<0.001). Furthermore, in the specific detection of bacteria (95.7% vs. 22.6%) and fungi (96.0% vs. 22.2%), the detection rate of mNGS was also significantly higher than that of CMTs mainly based on culture (p<0.001, p<0.001). However, in the detection of CMV/EBV viruses, there was no significant difference between the detection rate of mNGS and that of viral DNA quantification (p = 1.000 and 0.152). mNGS analysis revealed Prevotella, Streptococcus, Veillonella, Rothia, and Capnocytophaga as the most prevalent genera in the LRT of lung cancer patients. GSVA revealed significant correlations between these genera and tumor metabolic pathways as well as various signaling pathways including PI3K, Hippo, and p53.

Conclusion

mNGS showed a higher pathogen detection rate than culture-based CMTs in lung cancer patients with LRTIs, and also characterizing LRT microbiome composition and revealing potential microbial functions linked to lung carcinogenesis.

Restoring the epigenetic landscape of lung microbiome: potential therapeutic approach for chronic respiratory diseases

BACKGROUND

Chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and bronchiectasis, present significant threats to global health. Recent studies have revealed the crucial role of the lung microbiome in the development of these diseases. Pathogens have evolved complex strategies to evade the immune response, with the manipulation of host cellular epigenetic mechanisms playing a pivotal role. There is existing evidence regarding the effects of Pseudomonas on epigenetic modifications and their association with pulmonary diseases. Therefore, this study aims to directly assess the connection between Pseudomonas abundance and chronic respiratory diseases. We hope that our findings will shed light on the molecular mechanisms behind lung pathogen infections.

METHODS

We analyzed data from 366 participants, including individuals with COPD, acute exacerbations of COPD (AECOPD), bronchiectasis, and healthy individuals. Previous studies have given limited attention to the impact of Pseudomonas on these groups and their comparison with healthy individuals. Two independent datasets from different ethnic backgrounds were used for external validation. Each dataset separately analyzed bacteria at the genus level.

RESULTS

The study reveals that Pseudomonas, a bacterium, was consistently found in high concentrations in all chronic lung disease datasets but it was present in very low abundance in the healthy datasets. This suggests that Pseudomonas may influence cellular mechanisms through epigenetics, contributing to the development and progression of chronic respiratory diseases.

CONCLUSIONS

This study emphasizes the importance of understanding the relationship between the lung microbiome, epigenetics, and the onset of chronic pulmonary disease. Enhanced recognition of molecular mechanisms and the impact of the microbiome on cellular functions, along with a better understanding of these concepts, can lead to improved diagnosis and treatment.

Gut microbiome in cancer immunotherapy: Current trends, translational challenges and future possibilities

Gut microbiota is regarded as a crucial regulator of the immune system. Healthy gut microbiota plays a specialized role in host xenobiotics, nutrition, drug metabolism, regulation of the structural integrity of the gut mucosal barrier, defense against infections, and immunomodulation. It is now understood that any imbalance in gut microbiota composition from that present in a healthy state is linked to genetic susceptibility to a number of metabolic disorders, including diabetes, autoimmunity, and cancer. Recent research has suggested that immunotherapy can treat many different cancer types with fewer side effects and better ability to eradicate tumors than conventional chemotherapy or radiotherapy. However, a significant number of patients eventually develop immunotherapy resistance. A strong correlation was observed between the composition of the gut microbiome and the effectiveness of treatment by examining the variations between populations that responded to immunotherapy and those that did not. Therefore, we suggest that modulating the microbiome could be a potential adjuvant therapy for cancer immunotherapy and that the architecture of the gut microbiota may be helpful in explaining the variation in treatment response. Herein, we focus on recent research on the interactions among the gut microbiome, host immunity, and cancer immunotherapy. In addition, we highlighted the clinical manifestations, future opportunities, and limitations of microbiome manipulation in cancer immunotherapy.