We explored the role of SERPINA1 in clinical outcome prediction from the TCGA, GETx, and TARGET databases. As previously reported, SERPINA1 expression plays a dual role in different cancers. Specifically, when SERPINA1 was overexpressed, the prognosis of GBM is good in OS, DSS, and PFI. KIPAN had a good prognosis for OS and PFI. Although SERPINA1 mRNA was upregulated in BRCA, SERPINA1 protein expression was downregulated, possibly for the reason of DNA methylation and protein modification in BRCA. However, when SERPINA1 expression was downregulated in BRCA, OS, DSS, DFI, and PFI prognostic outcomes were favorable and protective (Supplementary Fig. 10). The histochemical data from the HPA database demonstrated a significant correlation between protein expression and prognosis in breast cancer, kidney cancer, and glioma (Supplementary Fig. 11), these results confirm that SERPINA1 may be a potential biomarker in GBMLGG, KIPAN, and BRCA.
There is growing evidence that younger cancer patients have tumors that are molecularly different from those of children and older cancer patients[46], and those young people are inherently not being a high-incidence group for cancer[47–49] which makes them focus less on the diagnosis and treatment. Therefore, we also analyzed the relationship between gender and age in different tumors. SERPINA1 expression was not associated with gender in various cancers, however, we observed a significant correlation between patient age and three tumors, with a significant positive correlation in KICH and a negative correlation in COAD and COADREAD, suggesting that increased SERPINA1 expression may also be associated with increased prevalence in younger colorectal cancer patients.
Many cancers are associated with promoter-specific hypermethylation[50]. It has been reported that DNA methylation levels can be used as tumor biomarkers for early detection, diagnosis, and prognosis[51]. We investigated for the first time the relationship between methylation levels of SERPINA1 and different tumors and the impact on clinical outcomes. which seems to be a promising direction.
With the development of oncology, immunology, cell biology, molecular biology, and other related disciplines in recent years[52], tumor immunotherapy has received increasing attention[53]. However, due to the complex process of tumor immunity, the combined effect of multiple mechanisms affects the efficacy of immune checkpoint inhibitors (ICIs)[54]. Thus, the reconstruction of immune moralization may be a promising field of tumor immunotherapy in the future. SERPINA1 has little research on tumor immunity. Here we have conducted a comprehensive analysis of the correlation between SERPINA1 expression and immune regulation. We analyzed the effect of SERPINA1 expression on immune cell infiltration with several algorithms, demonstrating a significant correlation between SERPINA1 expression and monocytes/macrophages in almost all tumors. Especially in GBM, SERPINA1 protein expression was shown to be positively associated with the number of M1 and M2, but negatively correlated with the ratio of M1/M2. SERPINA1 may influence tumor immune infiltration to affect patient prognosis and is closely related to tumorigenesis. Although a causal relationship could not be established in the current study, these findings suggest that SERPINA1 has a strong effect on the regulation of immune infiltrating macrophages. In recent years, after many disappointing results, tumor immunotherapy focusing on the inhibition of the immune checkpoint pathway has emerged as a clinical treatment for many cancers. The correlation analysis among the expression of SERPINA1 and immune regulatory genes, immune checkpoint inhibitor genes, and immune cell infiltration showed that: in renal cancer, SERPINA1 expression was significantly and positively correlated with immune regulatory genes, chemokines, MHC, immunosuppressant and immunostimulatory factor genes. Immune cell infiltration analysis also exhibited that SERPINA1 showed a significant positive correlation with immune scores in the glioma microenvironment and may play a role as a new immune checkpoint in the treatment of glioma.
We also analyzed the tumor genomic heterogeneity of SERPINA1 mutations in pan-cancer[39], and a growing number of studies have found that other tumor heterogeneity analyses are also emerging clinical biomarkers in immunotherapy, clinical outcomes, and chemotherapy[55, 56]. In addition, tumor heterogeneity based on SERPINA1 mutations in pan-cancer was also observed. Our analysis was based on the stemness characteristic of DNA methylation, and it was important to distinguish between the inherent stemness in CSCs (Cancer stem cells) and tumor microenvironment-induced dedifferentiation[57]. GBMLGG and LGG had a high mRNAi stemness index which showed a high degree of heterogeneity within the tumor. Due to the negative correlation between tumor stemness and immune checkpoint inhibitor prognosis, the large heterogeneity of gliomas suggests that the intratumoral environment, including infiltration of stromal cells, hypoxia, and immune cells, may play a role in the tumor. Immune cells may shape the CSC niche, the formation of which is a key link in the metastatic colonization of distant organs by tumor cells and affects the developmental plasticity of cancer cells. Further analysis of cancer cells associated with the stemness phenotype will provide new insights into the biology of primary tumors.
In functional enrichment analysis of SERPINA1, we speculated that SERPINA1 expression affects patient prognosis by activating oncogenic signaling pathways, such as the NOTCH pathway and DNA damage, further influencing the invasive metastasis of various cancers. For example, SERPINA1 mutations in breast cancer are associated with histidine acetylation, which can inhibit tumor cell proliferation and migration, thereby affecting prognosis. SERPINA1 as an autophagy-related gene, can initiate the recycling mechanism of internal cells, and enables the cells to survive in a starvation environment. Highly aggressive cancer cells can overcome drug stress through autophagy. In KIPAN, the level of SERPINA1 in lymphatic metastasis can be used as an indicator of resistance, and high SERPINA1 expression means that tumors will be resistant to chemotherapy. Therefore, compounds that specifically inhibit are expected to become more effective anticancer drugs to help people treat chemotherapy-resistant KIPAN. In glioma, SERPINA1 is related to the NABA molecular pathway, neutrophil degranulation, and KEGG cytokine receptor interaction, suggesting that SERPINA1 has a significant relationship with the biological mechanism of glioma, and is also related to immunity. However, the specific mechanism of SERPINA1 in tumor growth and metastasis remains unclear. Our study explored most of the pathways involved in the expression of SERPINA1-related genes in pan-cancer, which may help to define the exact function of SERPINA1 and the downstream signaling pathways involved.
It is reported that the combination of autophagy-regulating molecules and other anti-tumor drugs can be a promising anti-tumor treatment strategy. It is expected to regulate tumor EMT-mediated tumor invasion and metastasis by regulating autophagy. We have predicted a series of promising small molecule drugs that directly or indirectly target SERPINA1, such as Trametinib, and Crizotinib, whose drug sensitivity is strongly correlated with protein kinase inhibitory activity. FK866, GSK690693, and TW37 were the top three drugs predicted to be positively correlated with SERPINA1 expression according to the CTRP database. FK866 inhibits NAMPT activity, reduces NAD in the mucosa, and decreases the abundance and activity of NAD-dependent enzymes such as PARP1, Sirt6, and CD38, the treatment inhibits NF-κb activation, macrophage infiltration, and T-cell activation. GSK690693 is an AKT inhibitor. AKT is at the core of PI3K/AKT/mTOR signaling in the cell survival pathway, which is very common in tumor cells and has a significant relationship with tumor occurrence, growth, and metastasis. In macrophages, PI3K/AKT may regulate TLR4 and the downstream molecules to regulate proinflammatory cytokines and inflammation[58]. TW37 is an inhibitor of Bcl-2. The Bcl-2 protein family is involved in the dominant regulatory mechanisms of apoptosis, which can receive and transmit internal intracellular signals or external environmental stress signals, such as nutritional, hypoxic stress, DNA damage, excessive activation of oncogenes, endoplasmic reticulum stress, mainly playing a leading role in the intrinsic pathway of apoptosis. Bcl-2 protein is also closely related to the autophagic process and interacts with multiple molecules in the autophagy signaling pathway to play an anti-autophagic role[59, 60]. Macrophage proliferation and migration are significantly reduced by these potent MEK kinase inhibitors[61, 62]. There is significant evidence that these drugs affect SERPINA1, and thus play an important role in tumor chemotherapy, which is beneficial for improving tumor treatment.
According to the analysis of single-cell sequencing, SERPINA1 expression in breast cancer was shown to be significantly and positively correlated with DNA damage and inflammation, which exhibited consistency with the above analysis of SERPINA1 mutation, DNA methylation, and protein acetylation. In glioma, SERPINA1 expression was significantly correlated with EMT and invasion, which was consistent with tumor stemness analysis and immune infiltration analysis of the tumor microenvironment. In renal carcinoma, SERPINA1 was significantly and positively correlated with EMT and metastasis, which proved to be consistent with clinical staging analysis and immunological analysis. SERPINA1 was confirmed to be associated with macrophages in all three cancers via single-cell clustering analysis. This suggests that in addition to drug therapy, immunotherapy can also be carried out through macrophage phenotypic polarization. At the same time, our study has some limitations, such as the lack of relevant research data between the above three tumor subtypes, and the lack of experimental verification of our samples.