Patients with different extent of resection shows no difference in prognosis, while inflammatory response in ACP is relevant to poor clinical outcome
In 61 cases, total resection was performed in 36 cases and subtotal resection was in 25 cases (residual part adhered to important structures, tumor or cystic part that is hard to separate) (Table. 1). By comparing the differences of different resection methods and surgical approaches, it was observed that there was no significant difference between postoperative complications and long-term no progress of children (Supplemental Table S1 and S2)
At the end of the follow-up, there were tumor recurrences in 18 patients among all the 59 survived, and the rest two died of electrocytes imbalance and hypothalamus reactions during admission. The relapse time was 6-70 (median 24) months, and the follow-up time was 1-120 (median 21) months. There was no significant difference in recurrence rate in the gender (P = 0.515), and in surgical approaches (P = 0.381). PFS calculated by Kaplan-Meier curve and log rank test revealed that there was no significant difference between the degree of tumor resection and PFS of patients with progression free survival (P = 0.693), that is, compared with the total resection group, the recurrence rate of patients with partial tumor resection was not increased (Fig. 1a).
Among 25 patients who were diagnosed as ACP by postoperative pathology, and accessible to surgical slices, there were 3 cases of low-grade inflammatory response, 12 cases of medium-grade and 10 cases of high-grade, Fisher Exact Test showed that there was no significant difference in the degree of surgical resection between different inflammatory grades (P = 0.276), but there was a high correlation between the degree of surgical resection and tumor progression (P < 0.001). Meanwhile, the survival analysis showed that the prognosis of high-grade group was significantly worse than that of low-grade group (P = 0.022) (Fig. 1b). HE and IHC results showed that more calcification and inflammatory cells were either in recurrent tumor or tumor with sub-resection (Fig. 1c). At the same time, in 6 cases of recurrent tumor tissue, 5 cases were high inflammatory infiltration state. Comparison between before and after the recurrence of the same case, showed more activated M2 (Arg-1+) and less M1 (CD86+) phenotype of macrophages/microglia, while it was interesting to find that proportion of Iba-1+ cells decreased in relapsed tumor (Fig. 1c, d). These results suggested the evidence that inflammatory response might influence the progress of ACP.
Serpins family are potential players in the inflammation response of ACP TME
The results above hinted that inflammation might influence the progress of tumor and ACP patients’ outcome. On the evidence that macrophages and microglia in brain are critical in TME re-building. With GSE94349, we used NetworkAnalyst and GSEA to screen potential functional molecules associated with TAMs and inflammation (Fig. 2a, c). Via GO/KEGG enrichment analysis on differently expressed genes (DEGs), it demonstrated that keratinization, skin and epidermis development are the main physiological activity (Fig. 2b). And it indicated that SERPINs family (SERPINB2, SERPINB5, SERPINE1, SERPING1) were respectively involved in various functional gene sets like macrophages, microglia, inflammatory response and classic inflammation pathway NF-κB (Fig. 2c). Apart from the four genes, we chose top 5 genes in each gene set to demonstrate their relationship. Correlation heatmap showed the potential relationship among those hub genes in different gene sets, and SERPINE1 had significant correlation with SERPINB2, SERPINB5. What’s more, SERPINE1 was also associated with either PRRG4, TNFSF10, DSC2 or SDC1, suggesting a close relationship of these five genes with tumor proliferation, invasion and metastasis (Fig. 2d). And it was worth noting that expression level of SERPING1 showed negative correlation with other genes, suggesting it might participate in different pathways from SERPINE1. IL15, known as functional immune inducing and activation molecules, also showed pertinent connection with SERPINE1, SERPINB2 and SERPING1.
We next used CIBERSORT to verify the immune environment of kinds of brain tumor (ACP, pilocytic astrocytoma, glioblastoma, ependymoma and medulloblastoma) and normal brain tissues, and the results showed high correlation and percentage of M0 macrophage, M2 macrophage, CD4+ T memory cells, which accounted for more than 60%, indicating involvement of macrophages in tumor environment (Fig. 2e). To evaluate the TME difference between ACP and other brain tumors, comparisons between various immune cells fraction of ACP (n=24), pilocytic astrocytoma (n=10), medulloblastoma (n=15), glioblastoma(n=10), ependymoma (n=34) and normal brain (n=27) tissues were performed. The results revealed that T cells CD8+ and T cells CD4+ activated were lower in all kinds of tumor, and correspondingly, the proportion of T cells CD4+ resting increased, indicating the condition of immune inhibition. More interestingly, the fraction of macrophages M0 significantly boosted exclusively in ACP, and meanwhile the expression of macrophages M2 and plasma cells in ACP were more similar with other aggressive tumors, which described a TME with more inflammatory cells infiltration but weakened immune activity (Fig. 3).
Predicted functions of the SERPINs and its expression may correlated with macrophages
Based on the results that TME of ACP is probably similar with brain invasive tumor (low grade glioma),(10) and on the existed evidence that ACP is capable to malignantly transform into squamous cancer, we compared the transcriptional levels of SERPINs family in tumors with normal tissue in Oncomine database (Supplemental Fig. S1b). It showed SERPINE1 was significantly upregulated in Brain, HNSC and Esophageal Cancer. SERPINB2 and SERPINB5 were more tendinous increasing in Lung Cancer and Gastrointestinal Cancer. The expression level of SERPING1 was higher in Brain, Esophageal Cancer and Lymphoma. The mRNA expression levels of SERPINE1 were significantly in patients of glioma and squamous cancer (Supplemental Table S3).
In addition, pan-cancer analysis in TIMER also showed that the family increased in various cancer like COAD, HNSC, LUSC (P<0.001) (Supplemental Fig. S1a). We then tried to find if there existed similar expression patterns of SERPINs in other relevant cancer type. In GEPIA we chose GBM, LGG and HNSC to explore transcriptional level of SERPINs between tumor and normal tissue. It was found that SERPINE1 and SERPING1 were significantly upregulated in all three cancers. In HNSC, SERPINB5 was higher in tumor tissues while SERPINB2 was lower than normal tissue (Supplemental Fig. S1c).
Correlation between SERPINs expression level and tumor grades (stage) revealed that SERPINs had significant relevance with grades of GBM, while it seemed to have no influence in HNSC (Supplemental Fig. S2a). Kaplan–Meier curves demonstrated SERPINE1, SERPINB2 and SERPING1 were associated with RFS but not OS in GBM patients (P<0.05) (Supplemental Fig. S2b). And all SERPINs had no statistical difference both in OS and RFS in HNSC patients (Supplemental Fig. S3).
PPI network among SERPINs had been established to explore the relationship between upstream and downstream connection and GO/KEGG enrichment was used to explore probable pathway involved with tumor metastasis, invasion and activation of macrophages (Fig. 4a, b). Enrichment pathways consisted of various tumor inflammation pathway, such as matrix constructure, angiogenesis and so on. In TIMER, via kinds of immune infiltration algorithm, there revealed a positive correlation between SERPINs levels and the infiltration levels of macrophages (Fig. 4c).
Using TISCH, we sourced single-cell datasets GSE141982 and GSE131928 to reach a comprehensive exploration of SERPINs and TME. Cell cluster profiles showed that SERPINE1 evidently collocate in macrophages and mononucytes clusters, with slight enrichment in malignant cells and less in other cell types (Fig. 5a). At the same time, SERPING1 had a minor expression level. SERPINB2 and SERPINB5 were both expressed with basic levels in all kinds of cells (Fig. 5b). Gene-gene correlation showed SERPINE1 had a certain relation with SERPINB2 and SERPING1. Besides other SERPINs, SERPINE1 also indicated significant correlation with CD68, CD86, CD163 and CD206 (Supplemental Fig. S4).
At last, we conducted FISH to validate whether there exists colocation between SERPINs and macrophages in ACP, and the result showed there existed evident accumulation of SERPINE1 in macrophages. It was noticeable that SERPINE1+ macrophages were more likely located surrounding solid tumor while SERPING1+ in cystic part (Fig. 5c).