Investigating the impact of SMAD2 and SMAD4 downregulation in colorectal cancer and their correlation with immune markers, prognosis, and drug resistance and sensitivity.

Abstract

While many genes linked to colorectal cancer (CRC) contribute to cancer development, a thorough investigation is needed to explore crucial hub genes yet to be fully studied. A pivotal pathway in CRC is transforming growth factor-beta (TGF-β). This study aimed to assess SMAD2 and SMAD4 gene expression from this pathway. Counted data from the Cancer Genome Atlas (TCGA) were examined, comparing 483 tumor and 41 normal samples. Using clinical data, genes impacting overall survival (OS) were evaluated. GSE39582 was employed to confirmed the levels of genes in CRC compared to the normal samples. Additionally, employing unhealthy samples and the RT-qPCR means our outcomes was validated. Finally, PharmacoGx information were utilized to connect the levels of potential genes to drug tolerance and susceptibility. Our findings showed SMAD2 and SMAD4 levels in TGF-β signaling were more significant than other pathway genes. Our findings indicated that the protein levels of these genes were lower in malignant tissues than in healthy tissues. Results revealed a significant correlation between low levels of SMAD2 and unfavorable OS in CRC individuals. RT-qPCR results demonstrated decreased expressions of both SMAD2 and SMAD4 in cancer tissues compared to elevated levels in adjacent normal samples. Our results showed significant association between selected genes and immune cell infiltration markers such as CD8+, and B-cells. Our results indicated a potential association among the levels of SMAD2 and SMAD4 genes and tolerance and susceptibility to Nilotinib and Panobinostat drugs. Reduced expression of SMAD2 and SMAD4 may be pivotal in CRC progression, impacting downstream genes unrelated to patient OS. These findings suggest a potential role for SMAD2 and SMAD4 as predictive markers for drug response in CRC patients.