SPOCD1 serves as a prognostic marker in colon cancer and is associated with immune infiltration

Purpose Colon cancer is among the most common malignant tumors with poor prognosis in the world. SPOCD1 encodes transcription factor S-II family proteins whose aberrant expression is linked to tumor progression and immune regulation. However, it remains unclear whether SPOCD1 contributes to the progression and immunoregulation of colon cancer. Therefore, we sought to explore and confirm the expression of SPOCD1 in colon cancer and its association with immune regulation in this study. Methods Based on RNA-seq data from the TCGA colon cancer project, we explored the expression of SPOCD1 and its relationship with the OS, DSS, and PFI of patients with colon cancer. Moreover, the connection between SPOCD1 and the infiltration level of immune cells, immunomodulators and chemokines and receptors in colon cancer was comprehensively investigated utilizing the TIMER, GEPIA and TISIDB databases. Finally, we confirmed the expression of SPOCD1 in colon cancer and its correlation with immune cell infiltration by immunohistochemistry and multiplex immunohistochemistry. Results We found that SPOCD1 expression was increased in colon cancer and had tremendously diagnostic and prognostic value. The area under the curve (AUC) for SPOCD1 in COAD is 0.910 (95% CI 0.875–0.946) and high expression of SPOCD1 indicates a shorter OS, DSS and PFI in patients with colon cancer. Additionally, the increased expression of SPOCD1 in colon cancer is linked to the infiltration levels of immunomodulators, chemokines and receptors, neutrophils, macrophages and cancer-associated fibroblasts. We demonstrated that the expression of SPOCD1 was elevated in colon cancer tissues and expressed in both the nucleus and cytoplasm by immunohistochemistry. Through a multiplex immunohistochemistry experiment, we further confirmed the positive correlation between SPOCD1 expression and the expression of immune markers, including CD11b, CD163 and αSMA. Conclusion Taken together, our results suggest that SPOCD1 can be utilized as a promising indicator for diagnosis and prognosis evaluation and has tremendous potential to modulate the immune microenvironment in the progression of colon cancer.