Infection and Colorectal Neoplasm

Colorectal cancer is a major cause of cancer-related morbidity and mortality. Colorectal cancer is the third most common Malignancy and the 4th most common cause of cancer mortality worldwide. A number of infectious agents are considered to be cancer risk factors due to the hypothesis-generating and supportive evidence accumulated to date. It has been estimated that one fifth of all cancer is caused by some infectious agent(s). Infections from certain bacteria, such as Helicobacter pylori (H. pylori), Streptococcus bovis (S. Bovis), viruses, such as human papillomavirus (HPV), human cytomegalovirus (HCMV), and parasites may increase the risk of colorectal cancer. More studies are needed to learn the association of infectious agents with the incidence of colorectal cancer.


INTRODUCTION
Colorectal cancer (CRC) is a major cause of cancerrelated morbidity and mortality. Colorectal cancer is the third most common malignancy and the 4 th most common cause of cancer mortality worldwide. e.g., Crohn's disease) or sporadic, which accounts for more than 80% of all CRC. 1 High-fat diet, living in Western Countries (which can be related to the diet of the Western Civilizations, diets higher in red meat and fats) and obesity are risk factors for CRC. On the other hand, vitamin D, high risk of CRC. The long list of cancer risk factors continues to evolve, and in the past few decades has expanded to include infectious agents. 1 A number of infectious agents are considered to be cancer risk factors due to the hypothesis-generating and supportive evidence accumulated to date. It has by some infectious agent(s). In the case of CRC, the most recent list of acknowledged risk factors still does not include infectious agents, despite the current trend in the literature that supports this association. As our understanding of the underlying molecular processes in colorectal-cancer develops, the concept of microbialepithelial interactions as an oncogenic trigger might provide a plausible hypothesis for the pathogenesis of colorectal cancer. 2 It is reported that viruses and bacteria can cause CRC through direct mutagenesis, secretion of mutagenic products and/or prolonged to increased epithelial cell proliferation. This increased cell proliferation, on the other hand, has the potential to preferentially select carcinogenic clones. Data available and well-designed clinical trials with large patient populations to provide adequate statistical power are needed in order to adequately evaluate this hypothesis. 1

Helicobacter pylori
Helicobacter pylori is classified as a class I carcinogen by the International Agency for Research in Cancer due to the strong correlation between H. pylori infection and gastric cancer. H. pylori, a gram negative rod, is well adapted for life within the human stomach. It invades through a pH neutral niche between the mucus layer of the stomach and the gastric epithelium; it further has a set of adaptations which allows it to survive and modify innate immune responses. Interestingly, H. pylori does not invade tissues. Also, it does not enter epithelial cells nor does it penetrate the basal membrane; however, H. pylori does cause prolonged inflammation which is one of its proposed mechanisms for the development of neoplastic changes. 3 Brim et al found that there is correlation between H. pylori and colorectal neoplasm. Prevalence of colorectal polyps and adenomas were 456 (36%) and 300 (24%) respectively. Colorectal polyps were more prevalent in gastric H. pylori infected than non-infected subjects [43% vs. 34%; (95% CI = 1.2-1.9; OR = 1.5; p = 0.001)]. Patients with H. pylori-associated chronic active gastritis were at high risk to have adenomas (95% CI = 1.0-1.8; unadjusted OR = 1.3; p = 0.04). Gastric H. pylori infection, age, and male gender were independent risk factors for colorectal polyps. Serological testing also revealed a higher prevalence of H. pylori and its toxin Cag-A in polyp patients vs. non polyp patients' 4 Recent studies based on large databases with careful control for confounding variables have clearly demonstrated an increased risk of colorectal neoplasm associated with H. pylori infection. H. pylori-related chronic active gastritis confers an increased risk of colorectal neoplasm, and more extensive atrophic gastritis will probably be associated with even higher risk of neoplasm. The activity of H. pylori-related chronic gastritis is correlated with colorectal neoplasm risk. H. pylori-related chronic gastritis could be involved in an increased risk of colorectal neoplasm that appears to be enhanced by the progression of gastric 5 Meta-analysis was obtained from 22 studies of 86,880 cases and 93,760 controls, of which 13,318 cases and 10738 controls were H. pylori positive. As shown in Figure 1, the overall OR was 1.49 (95% CI = 1.30-1.72), and the test for the overall effect Z value was 5.57 (p < 0.05). 6 Wu et al, also have reported the same result (95% CI = 1.18-1.64; OR = 1.39). 7 Shmuely et al reported 10-fold increase in colorectal cancer risk with CagA(+) strains compared to CagA(-) strains (95% CI = 2.7-41.3; OR = 10.5; p = 0.001). 8 seroprevalence of H. pylori and the risk of developing colorectal adenomas (CRA) but not CRC. 9 Helicobacter pylori and risk of colorectal neoplasm 5 Year of design Various mechanisms have been suggested to underlie the correlation between H. pylori infection and colorectal neoplasm. H. pylori infection increases gastrin secretion, which could contribute to colorectal carcinogenesis by inducing mucosal cell proliferation in the colon. An epidemiological study of patients with H. pylori infection showed that mild hypergastrinemia was associated with about a 4-fold increase in the risk of colorectal neoplasm. 5 Gastrin is a candidate trophic factor that can possibly mediate the effects of H. pylori on tumors. Patients with H. pylori infection have increased basal and postprandial serum levels of gastrin. Thus, a plausible hypothesis is that H. pylori infection promotes colonic neoplasia by inducing hypergastrinaemia. Then, gastrin increases the expression of cyclooxygenase 2, amounts of prostaglandin E2, leading to further mucosal proliferation, reduction of apoptosis, angiogenesis and tumor growth. 9 H. pylori infection might result in damage to the such as those mediated by interleukin (IL)-8, which is associated colorectal cancer. 5

Streptococcus bovis
S. bovis, a non-enterococcal group D Streptococcus, of the human gastrointestinal (GI) tract in 5% to 16% of adults. In addition, S. bovis is commonly detected as a contaminant in packaged meat. If S. bovis enters the blood stream, it can cause bacteremia and endocarditis. S. bovis as Streptococcus gallolyticus, have an increased risk of prevalent colorectal neoplasia. Studies of S. bovis reveal that this bacterium releases proteins that S. bovis proteins were associated with an in vitro overexpression of cyclooxygenase-2, which is known to be frequently over expressed in human colorectal cancers and which can inhibit apoptosis and increase angiogenesis. 10 Sanchez et al reported one hundred nine cases of SGG (S. gallolyticus subsp. gallolyticus) bacteremia were detected (mean age, 66 years; 87% male). Colonoscopy was performed in 98 cases, diagnosing 69 cases of CRN: 57 adenomas (39 advanced adenomas) and 12 invasive carcinomas. Only 4 cases had suspected CRN before the blood culture. The

H. pylori infection and colorectal adenoma and adenocarcinoma 6
Infection and Colorectal Neoplasm prevalence of CRN was higher in patients with SGG bacteremia than in the 196 control patients (70% vs. 32%; 95% CI = 3.0-8.6; OR = 5.1; 95%). 11 Boleij et al reported among the S. bovis-infected patients who underwent colonic evaluation, the median percentage of patients who had concomitant adenomas/ carcinomas was 60% (interquartile range, 22%), which largely exceeds the disease rate reported in the general asymptomatic population. Meta-analysis showed that patients with S. bovis biotype I infection had a strongly increased risk of having CRC (95% CI = 3.94-13.36; pooled OR = 7.26) compared with S. bovis biotype II-infected patients. Notably, CRC occurred more often among patients with S. bovis IE than among patients with S. bovis infection at other sites (95% CI = 2.03-6.81; pooled OR = 3.72). 12

Klebsiella pneumoniae
Klebsiella pneumoniae is a gram-negative, nonmotile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal commonly associated with pneumonia and is a common cause of infections in the urinary tract, lower biliary tract, and surgical wound sites. Pyogenic liver abscess (PLA) is caused by bacteria and depending on the geographical data, most commonly isolated bacteria from pyogenic liver abscesses are E. coli for the Western Countries and K. pneumoniae for the eastern populations. 1 There are a number of case reports showing a positive correlation between PLA caused by K. pneumoniae and CRC. In one meta-analysis, 30 case case-controlled studies. Researchers found strong correlation between K. pneumonia-caused PLA and CRC and they reported isolation of these bacteria from 50% of this patient population. 13 A retrospective study was conducted on 2,294 patients of which 1,194 (52%) had K. pneumoniae infection. During a 10-year follow-up period, 54 (2.3%) patients were diagnosed with CRC, corresponding to an overall incidence rate of 669.1 (95% CI = 490.7-847.6) per 100,000 person-years. The adjusted hazard ratio of CRC was 2.68 times greater for patients with K. pneumonia PLA than for those with non-K. pneumonia PLA (95% CI = 1.40-5.11). There is very

Fusobacterium
Fusobacterium is the genus of anaerobic, gramnegative bacteria rod-shaped bacilli with pointed ends. Strains of Fusobacterium contribute to several human diseases, including periodontal diseases, Lemierre's syndrome, and topical skin ulcers. In 2011, researchers cells, and is often also associated with ulcerative colitis. 1 tumor tissue than in matched normal colorectal epithelium tissue, in all CRC cohorts (Czech p = 0.0016; Germany p = 0.0001; Ireland p = 0.0063).
in tumor tissue and tissue of less advanced forms of adenoma (CRC vs. TA p = 0.0287; CRC vs. TVA p = 0.0013). As in CRC, high grade dysplasia shows elevated Fusobacterium nucleatum disease tissue compared to matched normal colorectal epithelium tissue (p = 0.0148). 15 Fusobacterium contributes to CRC development through several mechanisms: invade colonic mucosa (highly invasive), induce local inflammation, and increase the expression of cytokines. 15 Human infection with the polyomavirus, JCV, is extremely common, affecting up to 80% of the population. Although the route of transmission for JCV is unknown, primary infection generally occurs in early childhood. The vast majority of those infected with JCV have no symptoms, and the virus travels to the kidneys, where it remains latent. However, severe immunosuppression, as seen in transplant patients and those with advanced HIV disease, can trigger reactivation of the virus causing a serious demyelinating disease known as progressive multifocal leukoencephalopathy. The oncogenic properties of JCV are well described in the literature and attributed to the viral protein, large T-antigen. Laboratory studies of this viral protein have shown that the large T-antigen has the ability to immortalize cells in culture. The mechanism for this cellular transformation has been studied: the large T-antigen binds p53 and members of the pRb family of proteins, thereby blocking tumor suppression and inducing unchecked cellular replication. This is hypothesized to result in chromosomal instability, which is common in colon carcinogenesis. 10 Casini et al reported that 16 out of 18 patients (88.9%) have been positive for the presence of viral DNA, assessed with three techniques, PCR, Northern blot and in situ hybridization, within the primary tumor mass and peri-tumoral tissue. 16 Theodoropulos et al reported that 61% of 80 patients with carcinomas, 60% of 25 patients with adenomas, and 30% of controls were PCR positive for JC virus. Statistically higher number of JCV copies in adenoma and adenocarcinoma than normal tissues with a much higher relative number of copies/μg of DNA (9-20x10 3 17 HPV is a double-stranded DNA virus that infects basal layer epithelial cells through microscopic abrasions or tears. There are more than 100 types of HPV, and about 40 of these types are known to infect genital epithelial cells. Not all types of HPV are associated with cancer. Currently, types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68, 73, and 82 these, types 16 and 18 are the most common types found in cervical cancer tumors, with one review HPV-18, or both. HPV infection is a necessary cause of cervical cancer and is associated with other epithelial malignancies, such as oropharyngeal, penile, vaginal, vulvar, and anal cancers. 10 Oncogenic HPV allows for the growth of cancerous cells through the expression of viral proteins E6 and E7. These interfere with tumor suppressor proteins, p53 and pRb, and induce telomerase, thereby immortalizing cells. Thus, HPV-related tumors infrequently contain p53 mutations. In a meta-analysis of nine case controlledstudies OR associated with HPV in CRC ranged from 2.7 to 9.1 (95% CI = 1.1-6.2 and 95% CI = 3.7-22.3). 10 Damin et al reported HPV DNA was detected in colorectal specimens of 60 patients with cancer (83.3%), but in none of the tissues from the control group (p < 0.001). HPV16 was the viral type most frequently detected, being present in 41 out of 60 positive cases (68.3%). 18 Bodaghi et al found that colorectal tissues from 28 of 55 (51%) patients with colorectal cancer were positive for HPV DNA. Colorectal tissues from all 10 control individuals were negative for HPV DNA (P = 0.0034). HPV 16 being the most prevalent type. The HPV infection may play a role in colorectal carcinogenesis. 19 HCMV can induce genes that are contributing to cancer progression (Bcl-2 and COX2). A larger study of 163 CRC tissues and non-neoplastic adjacent tissues as controls were tested for the presence of HCMV. The results showed HCMV DNA (PCR), was detected in 42.3% (69/163) of the tumor specimens, while only 5.6% (14/163) of samples of adjacent non-neoplastic tissue were positive for HCMV (p < 0.0001). Quantitative realviral copies in the tumor specimens than the adjacent non-neoplastic tissue specimens (p < 0.001). 20

Parasites
A link between S. japonicum and colorectal reports on this topic began to appear in the English literature in the late 1950's. Since this time, there have been a large number of patients reported individually or in groups with both colorectal carcinoma and evidence of infection by S. japonicum. S. japonicum associated colorectal cancers. It appears that the chronic ova plays an etiologic role. No evidence was found to suggest that ova release a mutagenic factor. 21 Qiu et al reported 142 colon cancer patients were compared to 285 matched control patients in Sichuan, China. Out of 142 colon cancer patients, 42 (30%) gave a history of previous S. japonicum infection, as compared to 14% of control patients. From this association between S. japonicum infection and colon cancer (OR = 3.3, p < 0.01). 22

CONCLUSION
Infections from certain bacteria (H. Pylori, S. Bovis, etc) viruses (HPV, HCMV, etc) and parasites may increase the risk of CRC. More research is needed to learn the pathogenesis of infectious agents with the incidence of CRC.