Published online Apr 28, 2020. doi: 10.3748/wjg.v26.i16.1912
Peer-review started: December 25, 2019
First decision: January 19, 2020
Revised: January 24, 2020
Accepted: April 4, 2020
Article in press: April 4, 2020
Published online: April 28, 2020
Since various molecular mechanisms and signaling pathways are common for the carcinogenic process and inflammatory bowel disease, including accumulation of immune cells and the release of several cytokines, chemokines, and growth factors, we were interested in the comparing of cytokine patterns and subtle changes in cytokine milieu in inflamed tissues of inflammatory bowel disease (IBD) patients, as well as in the cancer environment in colorectal cancer (CRC) patients. However, far too little attention has been paid to opportunities for early detection of subtle changes in cytokine milieu in inflamed tissues in IBD and CRC, especially in the clinical context. In line with this, we were searching for mRNA cytokine patterns of IBD patients in active disease compared to early and advanced CRC, to obtain data on in the similarities and differences in inflammation and cancer initiation and advances.
Dysregulation of the immune response in patients with IBD and CRC triggers infiltration and, which may further influence the inflammation and the carcinogenesis process. Since the recent developments for the role of cytokines in the intestinal inflammation are accumulating, there has been an increased interest in their role. Furthermore, the survival of CRC affected patients depends highly on early detection. Thus, establishing some of the parameters that can be detected and followed-up and used as prognostic factors or determining the treatment options can improve the survival rate and quality of life of CRC patients.
Our objectives were: (1) To assess the mRNA cytokine levels in inflamed tissues of IBD patients, as well as in the cancer environment in CRC patients (at early and advanced stages); and (2) To compare serum protein levels of the respective cytokines in both groups of patients. The objectives were chosen to compare cytokine patterns of active IBD patients with early and advanced CRC by selecting a panel of cytokines crucial for Th17/Treg differentiation and behavior (IL-6, TGFb, IL-17A, IL-23, IL-10), as well as the transcription factor FoxP3, in colon specimens, as mRNA biomarkers, and their serum protein levels. Future directions of this study could be the follow-up of IBD patients for developing dysplastic lesions or CRC, where the proposed biomarkers can be evaluated as a prognostic factor.
To address the aims of the study, we choose a panel of pro- and anti-inflammatory cytokines with a substantial role in Th17/Treg differentiation and behavior, in colon specimens of IBD and CRC patients, as mRNA biomarkers, and their protein levels in the peripheral blood. We used RNA extraction, reverse transcription, and quantitative polymerase chain reaction, as well as enzyme immunoassays to measure the protein levels of IL-17A, IL-6, IL-23, TGFb1, and IL-10 in patients’ sera.
We found a significant difference between higher gene expression of FoxP3, TGFb1, IL-10, and IL-23, and approximately equal level of IL-6 in CRC patients in comparison with IBD patients. After stratification of CRC patients, we found a significant difference in FoxP3, IL-10, IL-23, and IL-17A mRNA in early cases compared to IBD, and IL-23 alone in advanced CRC. The protein levels of the cytokines were significantly higher in CRC patients compared to IBD patients.
Our findings contribute to the research in the field by finding that IL-6 upregulation is essential for both IBD and CRC development until the upregulation of other Th17/Treg related genes (TGFb1, IL-10, IL-23, and transcription factor FoxP3) is a crucial primarily for CRC development. The significantly upregulated IL-6 could be a potential drug target for IBD and prevention of CRC development as well. However, more research are needed regarding the role and targeting of IL-6 in CRC patients.
With the chosen cytokine panel, we documented significant changes in genes related to Treg/Th17 development when comparing mRNA expression profiles of IBD and CRC (early and advanced) patients. Our findings showed that IL-6 upregulation is essential for both IBD and CRC, whereas the upregulation of genes related to Th17/Treg differentiation and behavior (TGFB1, IL-10, IL-23, and transcription factor FoxP3) is a crucial primarily for CRC development.
In our study, the only cytokine, which was approximately equally upregulated in both CRC and IBD, was IL-6. Previously, we found a higher expression of IL-6 in inflamed mucosa of IBD patients and tumor tissue and regional lymph nodes of CRC patients. Here, we observed that the differences between mRNA expression of IL-6 locally in IBD and CRC were not significant. We could suggest that this crucial cytokine is of equal importance for both inflammation and tumor development, i.e., we hypothesized that IL-6 is a critical tumor promoter during early CRC.
Thus, the significantly upregulated IL-6 could be a potential drug target for IBD and prevention of CRC development as well, with a significant potential for the clinical practice.
However, since we used a convenient sample of IBD patients with no immunosuppressive therapy to avoid bias, caution must be applied, and the hypothesis and findings should be tested with larger sample size. Secondly, although sporadic colon carcinogenesis and colitis-associated carcinogenesis share similar immune-related mechanisms, we cannot exclude differences in the critical molecular mechanisms underlying these two types of CRC.
The most important lesson learned from this study is the crucial role of IL-6 for both IBD and CRC. It is well-known that elevated IL-6 is linked to increased risk of development of colorectal adenomas and poor prognosis in CRC, but limited data is available regarding the role of IL-6 in IBD towards CRC. Besides, inadequate studies are existing that might be used to define cut off values for IL-6 as a diagnostic tool. In line with this, future directions should include studies exploring the diagnostic and therapeutic potential of IL-6.