Evaluation of membrane receptor stability in response to cytokine and growth factor stimulation: implications for DNA damage in colorectal cancer.

In recent years, there have been several attempts to classify colorectal cancer (CRC) into well-defined molecular subgroups that reflect the inherent heterogeneity between patients. Consensus molecular subtypes (CMS) classification successfully achieves this purpose and provides an important tool for personalized medicine. We previously identified an inverse association between high levels of anaplastic lymphoma kinase (ALK) expression and relapse-free survival, only in the CMS1 subtype, confirmed by a wide array of in vitro and in vivo assays. To support the hypothesis of ALK having a strong implication in CRC patients, we overexpressed the ALK receptor in a normal human colon epithelial cell line (NCM460). ALK overexpression was confirmed both in 2D and in 3D spheroid models. The role of ALK pathway was then investigated by examining its effects on proliferation, survival, migration, and invasion through various 2D and 3D in vitro assays. Immunohistochemistry analysis revealed an increase in the proliferation marker Ki67, and a decrease in the E-cadherin (E-CAD) and a deacrease in the vimentin (VIM) expression in ALK-overexpressing spheroids compared to the control ones, suggesting a correlation with tumor metastasis, progression, and invasion. Moreover, we identified a strong correlation between a high level of expression of ALK and the downregulation of MSH2, PMS2, and MLH1, the main components of the DNA Mismatch Repair (MMR) system whose downregulation is associated with microsatellite instability, typically found in CMS1 patients. Overall, these results suggest that ALK overexpression itself is sufficient to induce aggressive features in normal colonocytes, further supporting the hypothesis that ALK may be an attractive target for CMS1 colorectal cancer therapy.