Introduction
As common precursors to colorectal cancer (CRC), polyps and adenomas in the large intestine may develop into malignancy over time through a cascade known as the "normal-polyp-adenoma-carcinoma" sequence. Colorectal cancer (CRC) is the third most common cancer and the leading cause of cancer-related death worldwide, with an estimated increase to 3.2 million new cases and 1.6 million deaths by 2040. The high mortality of CRC is largely due to the late diagnosis, uncomplete molecular understanding of pathological progression, and limited treatment options for patients with advanced disease stage. Therefore, the identification of novel biomarkers at early (pre-cancerous) phase, thorough elucidation of pathological mechanisms, and development of effective therapies is crucial for CRC diagnosis and treatment.
Aims & Methods
Here we have utilized 10× genomics scRNA-seq platform to perform a high-resolution transcriptomic analysis of three normal colorectal tissues, two samples with inflammatory polyps, two specimens with adenomatous polyps and three CRC samples.
Results
By analyzing the scRNA-seq data of the ten human colorectal samples, which represent the four phases of colorectal pathogenesis, in combination with validation by immunofluorescence staining using expanded clinical samples, and together with verification using large scale TCGA and Kaplan–Meier data, we revealed a dynamic molecular landscape and for the first time demonstrated the importance of ligand-receptor genes, transcription factors and genes encoding multiple immunoglobulins and heat shock proteins driving the colorectal carcinogenesis.
Besides the heterogeneity of (sub-) cell types and difference of the transcriptomic profiling across the four stages, one of the most interesting and novel findings of this study is that the expression of ligand-receptor genes can be used to determine the cell types and even cell sub-types, at least for the colorectal tissues collected in this study, not the expressions of other gene sets, such as cell surface receptor signaling pathways, cell-cell signaling, transcription factors, cytokines, cell activation factors, cell signaling factors, or extracellular matrisome, implying that ligand-receptor pairs are fundamentally important for the cell type determination and cell-cell communications in colorectal tissues.
We found that some genes encoding immunoglobulin members are highly expressed in the T cells (IGHA1, IGHA2, IGKC and IGLC2) and in the fibroblasts (IGHA1, IGHA2, IGLC1, IGLC2, IGKC and JCHAIN) from normal colorectal tissues, while some genes encoding heat shock proteins are highly expressed in T cells (HSP90AA1, HSP90AB1, HSPA1B, HSPD1, HSPE1 and HSPH1) and plasma cells (HSP90AA1, HSPA1A, HSPA1B, HSPA6, HSPB1 and HSPD1) from abnormal colorectal samples, especially in the ones with adenomatous polyps.
Furthermore, IgG plasma cells can be grouped into two sub-types, characteristic of high expression of immunoglobulin-encoding genes IGKC and IGLC1/IGLC2, respectively. In addition, the six clusters of IgA plasma cells can also be characterized based on the combinatory expression level of some immunoglobulin-encoding genes (IGHA1, IGHA2, IGKC, IGLC1, IGLC2 and IGLC3). In summary, our analyses suggested the potential distinct functional importance of immunoglobulins and heat shock proteins in immunity and microenvironment during the colorectal malignancy.
Conclusion
Our transcriptome data provides valuable insights and a useful resource for better understanding the molecular pathological landscape in CRC to achieve more effective diagnosis and treatments.
References
Siegel, R.L., Wagle, N.S., Cercek, A., Smith, R.A., and Jemal, A. (2023). Colorectal cancer statistics, 2023. CA Cancer J Clin 73, 233-254. 10.3322/caac.21772.
2. Morgan, E., Arnold, M., Gini, A., Lorenzoni, V., Cabasag, C.J., Laversanne, M., Vignat, J., Ferlay, J., Murphy, N., and Bray, F. (2023). Global burden of colorectal cancer in 2020 and 2040: incidence and mortality estimates from GLOBOCAN. Gut 72, 338-344. 10.1136/gutjnl-2022-327736.
3. Huck, M.B., and Bohl, J.L. (2016). Colonic Polyps: Diagnosis and Surveillance. Clin Colon Rectal Surg 29, 296-305. 10.1055/s-0036-1584091.
4. He, D.G., Chen, X.J., Huang, J.N., Chen, J.G., Lv, M.Y., Huang, T.Z., Lan, P., and He, X.S. (2022). Increased risk of colorectal neoplasia in inflammatory bowel disease patients with post-inflammatory polyps: A systematic review and meta-analysis. World J Gastrointest Oncol 14, 348-361. 10.4251/wjgo.v14.i1.348.
5. Rudy, D.R., and Zdon, M.J. (2000). Update on colorectal cancer. Am Fam Physician 61, 1759-1770, 1773-1754.
6. Heumos, L., Schaar, A.C., Lance, C., Litinetskaya, A., Drost, F., Zappia, L., Lucken, M.D., Strobl, D.C., Henao, J., Curion, F., et al. (2023). Best practices for single-cell analysis across modalities. Nat Rev Genet 24, 550-572. 10.1038/s41576-023-00586-w.