Hepatitis B infection is causally associated with extrahepatic cancers: A Mendelian randomization study

Clinical correlation and survival analysis of hepatitis B virus infection in oral squamous cell carcinoma: a retrospective study of 1373 patients

BACKGROUND

Chronic hepatitis B virus (HBV) infection poses a significant global public health challenge and is found closely related to extrahepatic cancers, including head and neck cancer. Oral squamous cell carcinoma (OSCC) is the major category of head and neck cancer. This retrospective study was conducted to explore the clinical correlation and survival analysis of OSCC patients with HBV.

METHODS

The study involved 1,373 patients with OSCC treated at the Hospital of Stomatology, Sun Yat-sen University from 2012 to 2022. Propensity score matching was used to analyze the clinical correlations and survival outcomes, specifically overall survival (OS) and disease-free survival (DFS), in patients with or without hepatitis B surface antigen (HBsAg) seropositivity. Subgroup analyses were conducted for both the early and advanced stages of OSCC. The benefits of neck dissection in OSCC patients with HBV infection were further investigated.

RESULTS

The prevalence of HBV infection in our cohort was 12.0%. The HBsAg (+) group had a higher percentage of individuals under 60 (73.3% versus 63.7%, p = 0.016). Post-matching for age, sex, pathological T category, pathological N category, and neck dissection, the OSCC patients with HBsAg (+) had lower 5-year OS and DFS rates rather than HBsAg (-) patients, especially those with advanced stage and cervical lymph node metastasis. HBsAg (-) was confirmed as an independent protective prognostic indicator for both OS (hazard ratio [HR] = 0.52; 95% confidence interval [CI] = 0.34-0.79; p = 0.002) and DFS (HR = 0.69, 95% CI = 0.50-0.96; p = 0.027). Notably, elective neck dissection was recognized as an independent protective factor influencing 5-year OS and DFS. While DOI and pathological N category were both confirmed as the risk factors for prognosis.

CONCLUSIONS

HBsAg is a potential prognostic marker for OSCC. It is essential to screen for HBV infection prior to initiating tumor treatment. Additionally, serological testing, antiviral prophylaxis and therapy play crucial roles in preventing HBV reactivation during the course of tumor treatment. In cases of early OSCC associated with HBV infection, elective neck dissection has been shown to reduce the rates of recurrence and metastasis significantly.

An Investigative Study of LGALSL and HLA-DRB1 as Prognostic Biomarkers and Therapeutic Targets in Chronic Hepatitis B Patients With Persistent HBV DNA Viremia Under Entecavir Treatment

Despite significant advances in chronic hepatitis B (CHB) treatment, some patients receiving entecavir (ETV) still experience poor clinical outcomes. Identifying host factors contributing to ETV anti-HBV failure in CHB patients with persistent HBV DNA positivity is crucial for developing targeted therapies. We conducted a comprehensive study using univariate and reverse Mendelian randomization (MR), incorporating sequencing data and publicly available genetic data, followed by gene set variation analysis (GSVA), gene set enrichment analysis (GSEA) and immune cell infiltration analysis to systematically explore causal associations between host factors and CHB. Univariate MR analyses revealed a significant inverse association between increased HLA-DRB1 levels and CHB risk (odds ratio [OR] 0.607, 95% confidence interval [CI] 0.478-0.771, p = 0.00004), while increased LGALSL levels were significantly associated with a heightened risk of poor CHB prognosis (OR 1.110, 95% CI: 1.017-1.212, p = 0.01885), as estimated using the inverse variance weighting (IVW) method. Analysis of immune cell infiltration showed significantly higher HLA and mast cell levels in the poor prognosis group. HLA-DRB1 showed a significant positive correlation with HLA, whereas LGALSL showed a significant negative correlation. Compared to patients with favorable prognoses, those with poor prognoses exhibited significantly higher serum LGALSL levels (ELISA), lower HLA-DRB1 expression in peripheral blood mononuclear cells (PBMCs) (qPCR), and significantly increased LGALSL expression in liver tissue (IHC). Therefore, LGALSL and HLA-DRB1 may serve as potential prognostic biomarkers for CHB patients receiving ETV, providing novel avenues for diagnosis and treatment.

Additive interaction between hepatitis B virus infection and tobacco smoking on the risk of gastric cancer in a Chinese population

OBJECTIVE

Although hepatitis B virus (HBV) infection was regarded as a risk factor for liver cancer, the association of HBV infection with gastric cancer (GC) is unclear. In this study, we aim to assess the association of HBV infection with the risk of GC and explore the interaction between HBV infection and other risk factors.

METHODS

A case-control study was conducted and 409 GC cases and 1275 healthy controls were enrolled in Fujian province, China. Serum hepatitis B surface antigen (HBsAg) was measured and epidemiological data were collected. The association between HBV infection and GC risk was analyzed using logistic regression and meta-analysis method was employed to make estimates more conservative. Meanwhile, multiplicative and additive models were used to explore the interaction between HBV infection and other risk factors.

RESULTS

The prevalence of serum HBsAg positivity was 13.20% among GC cases and 6.20% among controls. Compared to HBsAg-negative subjects, the adjusted odds ratios (OR) for HBsAg positive were 3.30 [95% confidence interval (CI): (1.84-5.91)]. Compared to HBsAg-negative never smokers, the adjusted OR was 2.00 (95%CI: 1.19-3.34) for HBsAg-negative ever smokers,4.27 (95%CI: 1.97-9.26) for HBsAg-positive never smokers, and 4.73 (95%CI: 1.85-12.08) for HBsAg-positive ever smokers. These evidences indicated super-additive [API (95%CI): 0.78 (0.67-0.90), S (95%CI): 5.45 (3.26-9.08)] between HBV infection and tobacco smoking. No interaction between HBV infection and alcohol drinking was found on the risk of GC.

CONCLUSIONS

HBV infection increased the risk of GC, and tobacco smoking and HBV infection may positively interact in the development of GC.

The underlying mechanism and therapeutic potential of IFNs in viral-associated cancers

Interferons (IFNs) are a diverse family of cytokines secreted by various cells, including immune cells, fibroblasts, and certain viral-parasitic cells. They are classified into three types and encompass 21 subtypes based on their sources and properties. The regulatory functions of IFNs closely involve cell surface receptors and several signal transduction pathways. Initially investigated for their antiviral properties, IFNs have shown promise in combating cancer-associated viruses, making them a potent therapeutic approach. Most IFNs have been identified for their role in inhibiting cancer; however, they have also demonstrated cancer-promoting effects under specific conditions. These mechanisms primarily rely on immune regulation and cytotoxic effects, significantly impacting cancer progression. Despite widespread use of IFN-based therapies in viral-related cancers, ongoing research aims to develop more effective treatments. This review synthesizes the signal transduction pathways and regulatory capabilities of IFNs, highlighting their connections with viruses, cancers, and emerging clinical treatments.

Gut microbiota, metabolites, and cytokines in relation to the risk of prostate cancer in the Asian population

Purpose

Studies have shown that gut microbiota is involved in the tumorigenesis and development of prostate cancer. We aimed to perform a comprehensive analysis of causal associations of gut microbiota, metabolites, and cytokines with prostate cancer in the Asian population.

Patients and methods

Genome-wide association study (GWAS) summary datasets were collected from the public databases. There were 418 bacterial traits, 452 metabolites, 91 cytokines, 5408 cases of prostate cancer from East Asia, and 109,347 controls included. Mendelian randomization (MR) analyses were performed to investigate their causal relationships. Sensitivity analyses were conducted to test the reliability of MR results. Furthermore, the FinnGen database was used to assess the generalizability of our findings based on Asians.

Results

There were a total of 17 bacterial traits, 28 metabolites (including 2 microbiota-associated metabolites), and 9 cytokines to be significantly associated with prostate cancer in Asians (P < 0.05). Further MR analyses of these positive results indicated that G_Ruminococcaceae UCG014/TNFSF10 axis, G_Anaerofilum/TNFRSF14 axis, G_Erysipelotrichaceae UCG003/TNFSF10 axis, and P_Proteobacteria/cholesterol axis were key signaling pathways involved in the progression of prostate cancer. Notably, G_Ruminococcaceae UCG014/TNFSF10 axis and G_Anaerofilum/TNFRSF14 axis were found to act as protective factors, while the other two signaling axes played a crucial role in promoting the progression of prostate cancer. Sensitivity analyses further confirmed the reliability of our findings. Using the European population as outcome, we further assessed the generalizability of our conclusions and found limited applicability to Europeans.

Conclusions

We found that there were causal associations of gut microbiota, metabolites, and cytokines with prostate cancer in Asians. The causal effects of gut microbiota on prostate cancer were partially mediated by metabolites and cytokines. These findings might contribute to the development of new therapeutic strategies for prostate cancer.

An atlas on risk factors for gastrointestinal cancers: A systematic review of Mendelian randomization studies

OBJECTIVE

Gastrointestinal cancers are one of the most frequent cancer types and seriously threaten human life and health. Recent studies attribute the occurrence of gastrointestinal cancers to both genetic and environmental factors, yet the intrinsic etiology remains unclear. Mendelian randomization is a powerful well-established statistical method that is based on genome-wide association study (GWAS) to evaluate the causal relationship between exposures and outcomes. In the present study, we aimed to conduct a systematic review of Mendelian randomization studies investigating any causal risk factors for gastrointestinal cancers.

METHODS

We systematically searched Mendelian randomization studies that addressed the associations of genetically predicted exposures with five main gastrointestinal cancers from September 2014 to March 2024, as well as testing the research quality and validity.

RESULTS

Our findings suggested robust and consistent causal effects of body mass index (BMI), basal metabolic rate, fatty acids, total cholesterol, total bilirubin, insulin like growth factor-1, eosinophil counts, interleukin 2, alcohol consumption, coffee consumption, apolipoprotein B on colorectal cancer risks, BMI, waist circumference, low-density lipoprotein (LDL), total testosterone, smoking on gastric cancer risks, BMI, fasting insulin, LDL, waist circumference, visceral adipose tissue (VAT), immune cells, type 2 diabetes mellitus (T2DM) on pancreatic cancer risks, waist circumference, smoking, T2DM on esophageal adenocarcinoma risks, and VAT, ferritin, transferrin, alcohol consumption, hepatitis B virus infection, rheumatoid arthritis on liver cancer risks, respectively.

CONCLUSION

Larger, well-designed Mendelian randomization studies are practical in determining the causal status of risk factors for diseases.

The role of 1400 plasma metabolites in gastric cancer: A bidirectional Mendelian randomization study and metabolic pathway analysis

While observational studies have illustrated correlations between plasma metabolites and gastric cancer (GC), the causal association between the 2 is still unclear. Our study aims to delineate the bidirectional relationship between plasma metabolites and GC and find potential metabolic pathways. We undertook a bidirectional 2-sample Mendelian randomization (MR) analysis to investigate the causal relationship, specificity, and direction of association between 1400 plasma metabolites and GC. The GWAS data for metabolites was obtained from a cohort of 8299 European individuals. And the GC's GWAS data was from FinnGen Consortium with 2384 European individuals, and the GWAS catalog with 1029 European ancestry cases for validation. Causal estimates were primarily calculated by the inverse-variance weighted (IVW) method. To ensure robustness, we performed comprehensive sensitivity analyses to assess heterogeneity and address concerns regarding horizontal pleiotropy. We validated the forward relationship between metabolites and GC from another database and implemented meta-analysis. Furthermore, we conducted metabolic enrichment and pathway analysis of these causal metabolites using MetaboAnalyst5.0/6.0 with the database of Kyoto Encyclopedia of Genes and Genomes. All statistical analysis was carried out using R software. Metabolites like 2s, 3R-dihydroxybutyrate, 4-acetamidobutanoate, ferulic acid 4-sulfate and methyl indole-3-acetate was proven positively linked with the development of GC. Asparagine, glucose to maltose ratio, glycohyocholate, Gulonate levels, linoleoyl ethanolamide and Spermidine to (N(1) + N(8))-acetylspermidine ratio was proven to be negatively associated with GC. Moreover, linoleic acid, histidine, glutamine, bilirubin, Succinate to proline ratio were found to be potentially linked to the development of GC. Furthermore, our analysis identified 18 significant metabolic pathways, including Arginine and proline metabolism (P < .009) and Valine, leucine, and isoleucine biosynthesis (P < .031). Our findings offer evidence supporting potential casual relations between multiple plasma metabolites and GC. These findings may offer great potential for future application of these biomarkers in GC screening and clinical prevention strategies.

Causal link between hypothyroidism and gastric cancer risk: insights gained through multivariable Mendelian randomization and mediation analysis

Background

Gastric cancer (GC) is the third leading cause of cancer death worldwide, and hypothyroidism has been identified as a potential influencing factor. Despite known associations between hypothyroidism and various cancers, the causal link between hypothyroidism and GC and potential mediators of this relationship remains unclear. This study aimed to clarify these relationships using Mendelian randomization (MR).

Methods

Utilizing genetic variant information from the FinnGen and MRC Integrative Epidemiology Unit open genome-wide association studies (GWAS) databases, we conducted univariable and multivariable MR analyses to explore the causal relationship between hypothyroidism and GC risk. The analysis was adjusted for confounders such as BMI, smoking status, and alcohol intake, and included mediator MR analysis to examine the role of high cholesterol.

Results

We identified a significant inverse association between hypothyroidism and GC risk (OR = 0.93, 95% CI= 0.89-0.98, P = 0.003), with no evidence of reverse causation or pleiotropy. Adjustments for Helicobacter pylori infection weakened this association. Mediator analysis highlighted high cholesterol levels, chronic hepatitis B infection, and diabetes/endocrine disease status as significant mediators of the protective effect of hypothyroidism on GC risk.

Conclusion

Our findings suggest that hypothyroidism may confer a protective effect against GC, mediated in part by high cholesterol and other factors. These results underscore the importance of thyroid function and metabolic health in GC risk, offering new insights for preventive strategies and highlighting the need for further research into these complex associations.

The association of HBV infection and head and neck cancer: a systematic review and meta-analysis

BACKGROUND

Hepatitis B virus (HBV) infections is an important public health problem worldwide and closely affect extrahepatic cancer. Several recent studies have investigated the relationship between HBV infection and head and neck cancer (HNC), but their findings were inconsistent.In order to address the limitations of small sample sizes, we conducted a meta-analysis to assess the association between HBV and HNC.

METHODS

We systematically searched PubMed, Web of Science, Embase, Scopus, Cochrane Library, and China National Knowledge Infrastructure from inception to August 2023. Original articles published as a case-control or cohort study were included. HBV infection was identified by HBsAg, HBV DNA or ICD codes. Review articles, meeting abstracts, case reports, communications, editorials and letters were excluded, as were studies in a language other than English or Chinese. According to the MOOSE guidelines, frequencies reported for all dichotomous variables were extracted by two reviewers independently. Similarly, the outcomes of OR, RR or HR, and 95% CIs after adjusting for age and gender were collected.

RESULTS

Thirteen relevant studies and 58,006 patients with HNC were included. Our analysis revealed a positive correlation between HBV and HNC (OR = 1.50; 95% CI: 1.28-1.77). After adjusting for age and gender, the similar result (OR = 1.30; 95% CI: 1.10-1.54) was obtained. Subgroup analysis further demonstrated a significant association between HBV infection and oral cancer (OR = 1.24; 95% CI: 1.05-1.47), as well as nasopharyngeal carcinoma (OR = 1.41; 95% CI: 1.26-1.58). However, due to the limited number of studies included, the statistical significance was not reached for cancer of the oropharynx (OR = 1.82; 95% CI: 0.66-5.05), hypopharynx (OR = 1.33; 95% CI: 0.88-2.00), and larynx (OR = 1.25; 95% CI: 0.69-2.24) after adjusting for age and gender. When excluding the interference of HIV/HCV, smoking and alcohol use, the final outcome (OR = 1.17; 95% CI: 1.01-1.35) got the same conclusion.

CONCLUSIONS

Our study confirmed a positive relationship between HNC, specifically oral cancer and nasopharyngeal carcinoma, and HBV infection. However, further investigation is required at the molecular level to gather additional evidence in HNC.

Association of ATG16L1 and ATG5 gene polymorphisms with susceptibility to hepatitis B virus infection and progression to HCC in central China

Hepatitis B virus (HBV) infection is a severe public health problem worldwide. The relationship between polymorphisms of autophagy-related 16-like 1 gene (ATG16L1) and autophagy-related gene 5 (ATG5) with susceptibility to the stage of HBV infection has been reported in different populations. Nevertheless, this association is not seen in the population of central China. This study recruited 452 participants, including 246 HBV-infected patients (139 chronically infected HBV without hepatocellular carcinoma [HCC] and 107 HBV-related HCC patients) and 206 healthy controls. Genotyping of ATG16L1 rs2241880 and ATG5 rs688810 were performed using Sanger sequencing and polymerase chain reaction-restriction fragment length polymorphism, respectively. Our results indicated that the G allele of ATG16L1 rs2241880 was more frequent in healthy controls than in patients with chronicHBV infection. After adjusting for age and sex, an association between the ATG16L1 rs2241880 polymorphism and HBV infection was significant under the dominant and allele models (p = 0.009 and 0.003, respectively). However, no association between the ATG5 polymorphisms and HBV infection was observed. We also did not find a significant association between ATG16L1 and ATG5 polymorphisms and the progression of HBV-related HCC. Therefore, the genetic polymorphism of ATG16L1 rs2241880 may be associated with susceptibility to HBV infection in the population of central China.

Association between glycemic traits and melanoma: a mendelian randomization analysis

Background: The causation of Glycemic Traits and risks of Melanoma remains unknown. We used Mendelian Randomization (MR) to assess the links between Glycemic Traits and Melanoma. Method: Pooled data from Genome-Wide Association Studies (GWAS) were utilized to examine the relationships that exist between Fasting Insulin (n = 26), 2-h Glucose (n = 10), Fasting Glucose (n = 47), HbA1c (n = 68), and Type-2 Diabetes (n = 105) and Melanoma. We evaluated the correlation of these variations with melanoma risk using Two-Samples MR. Result: In the IVW model, Fasting Glucose (OR = 0.99, 95%CI = 0.993-0.998, p < 0.05, IVW), Type-2 Diabetes (OR = 0.998, 95%CI = 0.998-0.999, p < 0.01, IVW) and HbA1c (OR = 0.19, 95%CI = 0.0415-0.8788, p < 0.05, IVW) was causally associated with a lower risk of Melanoma. In all models analyzed, there was no apparent causal relationship between Fasting Insulin and Melanoma risk. There was no obvious causal difference in the IVW analysis of 2-h Glucose and Melanoma, but its p < 0.05 in MR Egger (OR = 0.99, 95%CI = 0.9883-0.9984, p < 0.05, MR Egger), and the direction was consistent in other MR analyses, suggesting that there may be a causal relationship. Conclusion: The results of this study suggest that a higher risk of Fasting Glucose, Type-2 Diabetes, 2-h Glucose, and HbA1c may be associated with a lower risk of Melanoma. However, no causal relationship between fasting insulin and melanoma was found. These results suggest that pharmacological or lifestyle interventions that regulate plasma glucose levels in the body may be beneficial in the prevention of melanoma.

Systemic lupus erythematosus is associated with lower risk of hepatitis B virus infection: A multivariable Mendelian randomization study in East Asian population

The relationship between systemic lupus erythematosus (SLE) and hepatitis B virus (HBV) infection is still unclear. We conducted a two-sample Mendelian randomization (MR) analysis using summary statistics from genome-wide association studies for SLE and HBV infection in individuals of East Asian ancestry. The inverse-variance weighted (IVW) method, weighted median (WM) method, and MR-Egger method were used to estimate the causal effect of SLE on HBV infection. Additionally, we performed a multivariable MR analysis adjusting for the effects of body mass index and rheumatoid arthritis. This MR study included a total of 225 106 individuals of East Asian ancestry, comprising 5616 cases and 219 490 controls. The IVW method (OR: 0.79, p = 3.34E-08) and the WM method (OR: 0.79, p = 9.09E-06) revealed a causal relationship between genetically predicted SLE and a low risk of HBV infection. The multivariable MR analysis still suggested a low risk of HBV infection associated with SLE (OR: 0.83, p = 2.89E-06). Our MR analysis supports a causal relationship between SLE and a low risk of HBV infection in individuals of East Asian ancestry.

Causal Associations between Gut Microbiota and Different Types of Dyslipidemia: A Two-Sample Mendelian Randomization Study

The determination of a causal association between gut microbiota and a range of dyslipidemia remains uncertain. To clarify these associations, we employed a two-sample Mendelian randomization (MR) analysis utilizing the inverse-variance weighted (IVW) method. This comprehensive analysis investigated the genetic variants that exhibited a significant association (p < 5 × 10-8) with 129 distinct gut microbiota genera and their potential link to different types of dyslipidemia. The results indicated a potential causal association between 22 gut microbiota genera and dyslipidemia in humans. Furthermore, these findings suggested that the impact of gut microbiota on dyslipidemia regulation is dependent on the specific phylum, family, and genus. Bacillota phylum demonstrated the greatest diversity, with 15 distinct genera distributed among eight families. Notably, gut microbiota-derived from the Lachnospiraceae and Lactobacillaceae families exhibit statistically significant associations with lipid levels that contribute to overall health (p < 0.05). The sensitivity analysis indicated that our findings possess robustness (p > 0.05). The findings of our investigation provide compelling evidence that substantiates a causal association between the gut microbiota and dyslipidemia in the human body. It is noteworthy to highlight the significant influence of the Bacillota phylum as a crucial regulator of lipid levels, and the families Lachnospiraceae and Lactobacillaceae should be recognized as probiotics that significantly contribute to this metabolic process.

The causal associations between growth factors and constipation: a two-sample Mendelian randomization study

Introduction: Certain growth factors (GFs) are associated with constipation, but few studies has analyzed the causal associations between the two. Therefore, this study used two-sample Mendelian randomization (MR) to systematically analyze the causal associations between GF levels and constipation based on data from genome-wide association studies (GWAS). Methods: Both GF and constipation data were obtained from European populations. GFs, as an exposure variable, were obtained from a genetic map of the human plasma proteome containing 3,301 samples, another GWAS dataset on 90 circulating proteins containing 30,931 samples, and a GWAS dataset containing 3,788 samples. Constipation, as an outcome variable, was obtained from the FinnGen project containing 26,919 cases and 282,235 controls and another UK Biobank dataset containing 3,328 cases and 459,682 controls. Single-nucleotide polymorphisms strongly associated with GFs were regarded as instrumental variables. Inverse-variance weighting, MR-Egger regression, weight median, simple mode, and weight mode methods were used to determine genetic associations. Cochran's Q test, Egger intercept, and Mendelian Randomization Pleiotropy RESidual Sum and Outlier tests were used to analyze sensitivity. Results: The IVW analysis based on FinnGen showed that NGFI-A-binding protein 2 and vascular endothelial growth factor receptor 2 were inversely associated with constipation, and that fibroblast growth factor 7 and transforming growth factor beta receptor II levels were positively associated with constipation. The IVW analysis based on UK Biobank showed that proheparin-binding epidermal growth factor, platelet-derived growth factor AA, and vascular endothelial growth factor₁₂₁ were inversely associated with constipation. Conclusion: This study showed that some GFs are genetically associated with the risk of constipation.

Hepatitis B virus infection: An insight into the clinical connection and molecular interaction between hepatitis B virus and host extrahepatic cancer risk

The evidence for chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) occurrence is well established. The hepatocyte epithelium carcinogenesis caused by HBV has been investigated and reviewed in depth. Nevertheless, recent findings from preclinical and observational studies suggested that chronic HBV infection is equally important in extrahepatic cancer occurrence and survival, specifically gastrointestinal system-derived cancers. Immune microenvironment changes (immune-suppressive cytokine infiltration), epigenetic modification (N6-methyladenosine), molecular signaling pathways (PI3K-Akt and Wnt), and serum biomarkers such as hepatitis B virus X (HBx) protein are potential underlying mechanisms in chronic HBV infection-induced extrahepatic cancers. This narrative review aimed to comprehensively summarize the most recent advances in evaluating the association between chronic HBV infection and extrahepatic cancer risk and explore the potential underlying molecular mechanisms in the carcinogenesis induction of extrahepatic cancers in chronic HBV conditions.

Bacterial DNA involvement in carcinogenesis

The incidence of cancer is high worldwide, and biological factors such as viruses and bacteria play an important role in the occurrence of cancer. Helicobacter pylori, human papillomavirus, hepatitis B viruses and other organisms have been identified as carcinogens. Cancer is a disease driven by the accumulation of genome changes. Viruses can directly cause cancer by changing the genetic composition of the human body, such as cervical cancer caused by human papillomavirus DNA integration and liver cancer caused by hepatitis B virus DNA integration. Recently, bacterial DNA has been found around cancers such as pancreatic cancer, breast cancer and colorectal cancer, and the idea that bacterial genes can also be integrated into the human genome has become a hot topic. In the present paper, we reviewed the latest phenomenon and specific integration mechanism of bacterial DNA into the human genome. Based on these findings, we also suggest three sources of bacterial DNA in cancers: bacterial DNA around human tissues, free bacterial DNA in bacteremia or sepsis, and endogenous bacterial DNA in the human genome. Clarifying the theory that bacterial DNA integrates into the human genome can provide a new perspective for cancer prevention and treatment.