Six samples, including mono- and co-cultured organoids treated with control, 5-FU, or oxaliplatin

Colorectal cancer, the third most commonly occurring tumor worldwide, poses challenges owing to its high mortality rate and persistent drug resistance in metastatic cases. We investigated the tumor microenvironment, emphasizing the role of cancer-associated fibroblasts in the progres-sion and chemoresistance of colorectal cancer. We used an indirect co-culture system comprising colorectal cancer organoids and cancer-associated fibroblasts to simulate the tumor microenvironment. Immunofluorescence staining was used to validate the characteristics of both organoids and fibroblasts. Transcriptome profiling was conducted after treatment with anticancer drugs, such as 5-fluorouracil and oxaliplatin, to identify chemoresistance related genes. Changes in gene expression in the co-cultured colorectal cancer organoids following anticancer drug treatment compared to monocultured organoids, particularly in pathways related to interfer-on-alpha/beta signaling and major histocompatibility complex class II protein complex assembly, were identified. These two gene groups potentially mediate drug resistance associated with JAK/STAT signaling. The interaction between colorectal cancer organoids and fibroblasts crucially modulates the expression of genes related to drug resistance. Enhanced understanding of the interactions between cancer cells and their microenvironment can lead to advancements in personalized medical research.