Association of Epithelial Mesenchymal Transition, Stemness and Inflammation in Colorectal Carcinoma. Summary of the Doctoral Thesis

Abstract

Colorectal cancer (CRC) and its treatment is one of the hot topics in medicine, as there is a still a high number of patients with CRC and deaths from CRC. In the era of personalized medicine, a huge field of research is devoted to inflammation, a process that plays an important dual role in carcinogenesis. Survival studies have highlighted the prognostic significance of peritumoural inflammation in CRC. The current theoretical background allows us to link inflammation, the epithelial-mesenchymal transition (EMT), and the closely associated stem cell differentiation in CRC. However, there is scarce direct morphological evidence. The aim of this work was to investigate the role of inflammation in cancer growth and invasion by analyzing the association between inflammation and known morphological prognostic features of CRC, EMT, and mismatch repair (MMR) protein expression. Materials and methods: This retrospective, morphological, and immunohistochemical investigation involved 553 consecutive cases of surgically treated CRC. Besides histopathological CRC assessment, peritumoural inflammation, EMT-characterizing molecular parameters, and MMR protein immunohistochemical detection within CRC tissue was performed. Descriptive statistical analysis was done. The research was carried out in accordance with the Declaration of Helsinki and received approval from the Committee of Ethics of Riga Stradins University [No E-9 (2), 04.09.2014].Results: The tumours of the 553 CRC cases were predominantly located in the left part of the bowel (70.9 %), and were significantly associated with an annular appearance and smaller size (p < 0.05). Mucinous and signet ring cell carcinomas detected within this study were associated with a larger tumour size and significant local structure involvement. Locally advanced tumours predominated within this study: pT3 comprised 49.6 % of cases, pT4 comprised 35.6 % of cases, and pN + comprised 40.5 % of cases. The extent of necrosis was significantly higher in tumours with higher pT, grade, and pN+. There were significant associations between high-grade inflammation and lower pT (p = 0.002), the absence of lymph node metastases (p< 0.001), and less frequent local structure involvement (p< 0.05). Expression of EMT markers and MMR proteins yielded no significant associations with peritumoural inflammation based on the Klintrup-Mäkinen score or the density of lymphoid follicles. Nevertheless, E-cadherin expression was significantly associated with the eosinophil density (p = 0.007), and lower N-cadherin expression was significantly associated with the presence of synchronous CRC. Lower MMR protein expression was associated with changes in E-cadherin and CD44 expression (p< 0.05). Lower MLH1 expression was associated with a lower neutrophil density within the CRC (p = 0.02).Conclusion: High-grade peritumoural inflammation is associated with beneficial morphologic CRC features, including less frequent invasion, and is not secondary to tissue damage and necrosis. Crohn’s disease-like lymphoid reaction (CLR) is not associated with cancer spread by pTN; this finding indirectly suggests an independent role of CLR in carcinogenesis. Further, inflammation based on the Klintrup-Mäkinen score and CLR are not dependent on EMT and stem cell differentiation. MMR protein expression is a marker for EMT within CRC, indicating the need to perform these tests on routine examination to detect patients who might need more advance treatment. MLH1 expression within CRC affects the density of neutrophils within peritumoural inflammation, showing a potential role for the MMR status in anti-tumour immunity. This research highlights the complex associations between inflammation, tumour morphology, EMT, and MMR protein expression in human CRC tissues.