PhD Scientific Days 2023

Translational Medicine III.

The microenvironmental influence on intratumoral cellular heterogeneity of colorectal cancer

Text of the abstract

Cancer is the second most frequent cause of death worldwide, and colorectal cancer (CRC) is commonly accountable, thus being a leading health problem. Recently, increasing attention is being brought to intratumoral heterogeneity with respect to survival and drug responses. To investigate intratumoral heterogeneity of CRC, patient-derived organoids are effective models. Based on gene expression profiles, the consensus molecular subtype system (CMS) emerged as a promising diagnostic and prognostic tool for CRC in 2015. According to this classification four subtypes are recognized of which the CMS2/3 subgroup is the “classic CRC” with KRas mutation and enhanced Wnt signaling. CMS4 has the worst prognosis, and is characterized by fibroblast accumulation, TGF-β signaling, epithelial-mesenchymal transition (EMT) and high expression of the HTR2B receptor.
I investigated the influence of tumor microenvironment on the intra-tumoral cellular heterogeneity of CRC in my experiments.
CRC patient-derived organoids were cultured with or without fibroblasts, in Matrigel or collagen, an extracellular matrix that is negatively correlated with patient survival and is enriched during tumor progression. The expression level of markers, such as HTR2B, was evaluated with RT-qPCR, immunohistochemistry, and flow cytometry.
Organoids showed a higher positivity for the EMT marker lumican in co-cultures. CRC cells displayed a higher positivity for HTR2B and the CMS2/3 marker CDX2 in co-culture with fibroblasts. Furthermore, the percentage of CRC cells with a mixed CDX2/HTR2B positive phenotype was higher in coculture. Mixed phenotype presentation was similarly elevated for CRC cells grown in amino acid or glucose deprived medium compared to standard growth medium. Additionally, HTR2B positivity was higher in collagen compared to Matrigel.
Culturing organoids in collagen or in fibroblast co-cultures led to partial EMT and a shift to CMS4, both indicating worse prognosis. Altering the tumor microenvironment significantly modifies intra-tumoral cellular heterogeneity, which in turn may affect the response and/or survival of patients for treatments.
This research was financed by OTKA-K 137554 and ÚNKP-22-2-III-SE-1. Ethical permission: TUKEB 2015, 51323-4/2015/EKU.