Colorectal cancer (CRC) is the second most common cause of cancer death in the western world. An effective screening program leading to early detection of disease would severely reduce the mortality of CRC. Alterations in the gut microbiota have been linked to CRC, but the potential of microbial markers for use in CRC screening has been largely unstudied. We used a nested case–control study of 238 study subjects to explore the use of microbial markers for clbA+ bacteria harboring the pks pathogenicity island, afa‐C+ diffusely adherent Escherichia coli harboring the afa‐1 operon, and Fusobacterium nucleatum in stool as potential screening markers for CRC. We found that individual markers for clbA+ bacteria and F. nucleatum were more abundant in stool of patients with CRC, and could predict cancer with a relatively high specificity (81.5% and 76.9%, respectively) and with a sensitivity of 56.4% and 69.2%, respectively. In a combined test of clbA+ bacteria and F. nucleatum, CRC was detected with a specificity of 63.1% and a sensitivity of 84.6%. Our findings support a potential value of microbial factors in stool as putative noninvasive biomarkers for CRC detection. We propose that microbial markers may represent an important future screening strategy for CRC, selecting patients with a “high‐risk” microbial pattern to other further diagnostic procedures such as colonoscopy.

The use of faecal microbial markers as non-invasive biomarkers for colorectal cancer (CRC) has been suggested, but not fully elucidated. Here, we have evaluated the importance of Parvimonas micra as a potential non-invasive faecal biomarker in CRC and its relation to other microbial biomarkers. The levels of P. micra, F. nucleatum and clbA + bacteria were quantified using qPCR in faecal samples from a population-based cohort of patients undergoing colonoscopy due to symptoms from the large bowel. The study included 38 CRC patients, 128 patients with dysplasia and 63 controls. The results were validated in a second consecutive CRC cohort including faecal samples from 238 CRC patients and 94 controls. We found significantly higher levels of P. micra in faecal samples from CRC patients compared to controls. A test for P. micra could detect CRC with a specificity of 87.3% and a sensitivity of 60.5%. In addition, we found that combining P. micra with other microbial markers, could further enhance test sensitivity. Our findings support the potential use of P. micra as a non-invasive biomarker for CRC. Together with other microbial faecal markers, P. micra may identify patients with “high risk” microbial patterns, indicating increased risk and incidence of cancer.

The anti-tumor immune response has been shown to be of great prognostic importance in colorectal cancer (CRC) and so has the tumors ability for immune evasion. Our aim of this study was to investigate tumor factors that influence immunity. We used a gene expression array to search for potential mechanisms of tumor immune escape. One candidate gene identified was , involved in antigen presentation by MHC class I. TAP1 protein expression was evaluated by immunohistochemistry in 436 CRC patients of the Colorectal Cancer in Umeå Study cohort. We found a significant association between a downregulated expression of TAP1 and low infiltration of various subtypes of lymphocytes as well as macrophages. A downregulated expression of TAP1 was further found to be independent of molecular characteristics, suggesting TAP1 down-regulation to reach beyond the well described highly immunogenic MSI CRCs. A low expression of TAP1 was also significantly associated with poor prognosis in patients with CRC, a result that stayed significant in tumor front of early stage tumors (stage I-II) through multivariable analyses. Furthermore, we found that TAP1 expression was inversely correlated with methylation at sites in close proximity to the promoter region. In summary, our results show down-regulation of TAP1 to be a general mechanism of tumor immune escape in CRC and a poor prognostic factor in stage I-II CRC patients. We also suggest that methylation of the gene may be a putative mechanism for TAP1 downregulation.

Dental caries is a chronic infectious disease that affects billions of people with large individual differences in activity. We investigated whether PRH1 and PRH2 polymorphisms in saliva acidic proline-rich protein (PRP) receptors for indigenous bacteria match and predict individual differences in the development of caries. PRH1 and PRH2 variation and adhesion of indigenous and cariogenic (Streptococcus mutans) model bacteria were measured in 452 12-year-old Swedish children along with traditional risk factors and related to caries at baseline and after 5-years. The children grouped into low-to-moderate and high susceptibility phenotypes for caries based on allelic PRH1, PRH2 variation. The low-to-moderate susceptibility children (P1 and P4a−) experienced caries from eating sugar or bad oral hygiene or infection by S. mutans. The high susceptibility P4a (Db, PIF, PRP12) children had more caries despite receiving extra prevention and irrespective of eating sugar or bad oral hygiene or S. mutans-infection. They instead developed 3.9-fold more caries than P1 children from plaque accumulation in general when treated with orthodontic multibrackets; and had basic PRP polymorphisms and low DMBT1-mediated S. mutans adhesion as additional susceptibility traits. The present findings thus suggest genetic autoimmune-like (P4a) and traditional life style (P1) caries, providing a rationale for individualized oral care.

The commensal pathogen Streptococcus mutans uses AgI/II adhesins to adhere to gp340 adsorbed on teeth. Here we analyzed isolates of S. mutans (n ‫؍‬ 70 isolates) from caries and caries-free human extremes (n ‫؍‬ 19 subjects) by multilocus sequence typing (MLST), AgI/II full-length gene sequencing, and adhesion to parotid saliva matched from the strain donors (nested from a case-control sample of defined gp340 and acidic proline-rich protein [PRP] profiles). The concatenated MLST as well as AgI/II gene sequences showed unique sequence types between, and identical types within, the subjects. The matched adhesion levels ranged widely (40% adhesion range), from low to moderate to high, between subjects but were similar within subjects (or sequence types). In contrast, the adhesion avidity of the strains was narrow, normally distributed for high, moderate, or low adhesion reference saliva or pure gp340 regardless of the sequence type. The adhesion of S. mutans Ingbritt and matched isolates and saliva samples correlated (r ‫؍‬ 0.929), suggesting that the host specify about four-fifths (r 2 ‫؍‬ 0.86) of the variation in matched adhesion. Half of the variation in S. mutans Ingbritt adhesion to saliva from the caries cases-controls (n ‫؍‬ 218) was explained by the primary gp340 receptor and PRP coreceptor composition. The isolates also varied, although less so, in adhesion to standardized saliva (18% adhesion range) and clustered into three major AgI/II groups (groups A, B 1 , and B 2 ) due to two variable V-region segments and diverse AgI/II sequence types due to a set of single-amino-acid substitutions. Isolates with AgI/II type A versus types B 1 and B 2 tended to differ in gp340 binding avidity and qualitative adhesion profiles for saliva gp340 phenotypes. In conclusion, the host saliva phenotype plays a more prominent role in S. mutans adhesion than anticipated previously.