Study on the mechanism of haptoglobin targeting the SP1/HIF-1α/SHP2/SIRPα pathway to promote the progression of colorectal cancer

Objective The aim of this study was to investigate the specific mechanism by which Haptoglobin promotes colorectal cancer progression by up-regulating the SP1/HIF-1α/SHP2/SIRPα signaling pathway in tumor-associated macrophages, mediating M2 polarization and inhibiting phagocytosis.Methods Colorectal cancer-related genes were screened from the GEO database by bioinformatics analysis, and differential analysis and pathway enrichment analysis were performed using R language. A total of 78 patients with colorectal tumors removed in Department of General Surgery of the First Affiliated Hospital of Hebei North University from 2015 to 2019 were selected. Immunohistochemical tests were used to detect the expression of Hp in cancerous tissues and adjacent normal tissues, and to analyze the relationship between the expression level of Hp and the pathological features and prognosis of colorectal cancer. The co-culture model of SW480 colorectal cancer cells and THP-1 cells was used in the experiments, and Western blot, Q-PCR and fluorescent microsphere phagocytosis experiments were performed to analyze the expression levels of each group of proteins and genes. Tumorigenic experiments in nude mice further verified the mechanism of action of Haptoglobin.Results Bioassay analysis showed that the SP1/HIF-1α pathway was significantly upregulated in colorectal cancer cells. Immunohistochemical results showed that the positive expression rate of Hp in colorectal cancer tissues was significantly higher than that in adjacent normal tissues, and there was significant statistical difference, P<0.001. The expression level of Hp was closely correlated with TNM stage, invasion depth, lymph node metastasis, distant metastasis, sCEA and sCA199 (P<0.05), while there was no correlation with sex, age, tumor size and differentiation degree (P>0.05). In addition, the 5-year survival rate of patients with high Hp expression was significantly lower than that with low HP expression, and there was significant statistical difference, P<0.05. Western blot and Q-PCR experiments showed that Haptoglobin significantly increased the expression of M2 polarization markers (Arginase 1, CD206) in tumor-associated macrophages through upregulation of the SP1/HIF-1α/SHP2/SIRPα signaling pathway. The results of phagocytosis assay showed that Haptoglobin significantly inhibited the phagocytosis of macrophages. Experiments in nude mice showed that Haptoglobin promoted tumor growth and decreased tumor volume after SP1 inhibitor intervention, an effect that was reversed by overexpression of HIF-1α.Conclusion Haptoglobin promotes the progression of colorectal cancer by targeting the SP1/HIF-1α/SHP2/SIRPα signaling pathway to promote M2 polarization of tumor-associated macrophages and inhibit phagocytosis.