CRC is a global public health challenge with high morbidity and mortality. Recently, it has been reported that CSCs play an important role in therapeutic resistance, tumor progression and disease recurrence (13). CSCs achieve immune escape and drug resistance by enhancing DNA damage repair, activating mitotic/anti-apoptotic pathways, and removing therapeutic agents by drug efflux pumps (14). There have been attempts to target tumors with specific CSC markers (15). Recently, it has been reported that there is a general association between cancer stem anticancer immunity and cancer stemness (16). Therefore, bioinformatics analysis of the immune microenvironment and cancer cell stemness in CRC is essential for future research.
PFS and OS were recommended as the endpoints for COAD and READ cohort (17). The Kaplan Meier curve showed a significant difference in Progression-free survival (PFS) between the high and low mRNAsi score groups in this study. First, WGCNA identified the modules and genes associated with CSC characteristics. We screened 210 hub genes that were most significantly related to mRNAsi and performed GO and KEGG analysis with them. In addition to GO terms such as "extracellular matrix organization" and "extracellular structure organization", we also obtained the results consisting of the cGMP-PKG signaling pathway, focal adhesion, and calcium signaling pathway. Next, ten key prognostic genes (VCAN, SPARC, COL12A1, THBS2, COL1A2, COL5A1, TAGLN, DCN, MYH11, CDH11) were screened by PPI network and LASSO Cox regression. In addition, we investigated the association between risk score and immune cells. We use these results to further understand the relationship between CRC progression and CSC characteristics.
Functional annotations showed that the 210 hub genes we obtained with WGCNA were significantly enriched in several pathways associated with CRC progression. For example, one of the key factors regulating the progression of CRC liver metastasis is the extracellular matrix organization (18). The growth and invasion of colorectal cancer cells can be regulated by focal adhesion pathways (19). In addition, we have identified several pathways that may be potential regulatory mechanisms in the development of CRC such as cGMP − PKG signaling pathway and Calcium signaling pathway.
Many of the ten key mRNAsi-related genes we screened have been reported in CRC, and some of them have also received attention in the CSCs field. For instance, CRC patients with high VCAN expression have a poor prognosis (20), which is consistent with the results of our study. Recent reports have shown that the proliferation, invasion, and migration of colon cancer cells are promoted by inhibinting subunit beta A through up-regulation of VCAN (21). SPARC can not only promote the invasion of tumor cells but also promote cell apoptosis as a sensitizer of conventional chemotherapy (22). Additionally, it has been shown that SPARC is overexpressed in endometrial CSCs, which may be related to stromal formation and cell migration (23). TAGLN is involved in epithelial-mesenchymal transformation in the progression of CRC and plays an important role in promoting malignant progression (24). A single-cell multiomics sequencing has been used to identify TAGLN as a fibroblast-specific biomarker that predicts poor prognosis in CRC (25). Decorin, which is encoded by DCN, is an important regulatory factor in the occurrence and development of various cancers and can inhibit the growth of various tumor cell lines. There have been attempts to treat CRC with oncolytic adenovirus that encodes decorin and has been successed in animal experiments (26). Studies have shown that in triple negative breast cancer, CDH11 regulates CSC activity and inhibits tumor growth through the WNT signaling pathway (27). In addition, COL12A1, COL1A2, and COL5A1 all belong to the collagen family and are potential prognostic factors for CRC (28).
We found significant differences in the proportions of some immune cells between high-risk and low-risk score groups, suggesting that there may be some connection between CSCs and the immune microenvironment. Previous studies have shown that CSCs interact with immune cells in a variety of cancers. For example, in lung adenocarcinoma, CD44, a marker of CSCs, is positively associated with immune cell infiltration (29). M1 macrophages have been reported to play a key role in the development of prostate cancer and the low immune microenvironment is one of the factors leading to the stemness of prostate cancer cells (30). Tumor heterogeneity is one of the main causes of treatment failure. The ecosystem composed of CSCs and tumor microenvironment has been proposed to drive tumor heterogeneity, and its mechanism needs to be further investigated (31). In addition, targeted elimination of CSCs is an important strategy of tumor immunotherapy. Drugs that target the elimination of colorectal cancer stem cells have been developed to significantly increase the cytotoxicity of NK cells, enhance antibody production, and reduce Treg subsets (32).