Sarcoma is a rare tumor with local invasion and distant metastasis. The prognosis is poor. Histological biopsy is the most authoritative standard for the diagnosis of Sarcoma[34, 35]. The main therapeutic methods are radiation therapy and surgery , and there are still no proven target drugs for sarcomas. Up to now, the mechanism of sarcomas is still poorly understood, which is the main obstacle to the development of specific targeted drugs.
Pyroptosis, a newly-discovered mode of programmed cell death, plays double roles in tumor occurrence and therapeutic mechanisms. Normal cells are activated by many inflammatory molecules secreted during pyrophosis, causing their transformation into tumor cells . In addition, pyroptosis of tumor cells may be a new treatment target .
In Sarcomas, the problem of how pyroptosis-associated genes relate with each other, and if they are correlated to patients' survival outcomes, remains unclear. Our study generated a profile characterized by seven scorose-related genes (IGHG2, PODXL2, LRRC17, GABRA3, SCUBE3, HLF, and RFLNB) and found that these genes can predict OS in patients. IGHG2 (Immunoglobulin Heavy Constant Gamma 2), a Protein Coding gene, is associated with some kinds of diseases, for example, Immunoglobulin Kappa Light Chain Deficiency. And the related pathways of it are Creation of C4 and C2 activators and Innate Immune System. PODXL2 is a member of the CD34 protein family, whcih is found in endothelial cells and is a ligand for angioselectin, mediating the interaction of white blood cells with the surface of blood vessels. LRRC17 (Leucine-rich repeat containing 17), a gene that mainly regulate the osteoblastogenesis process, is primarily expressed in osteoblasts under physiological conditions. Alpha3, GABRA3 -γ -aminobutyric acid type A receptor subunit is a protein-coding gene, which is related with diseases including periodic thyrotoxic paralysis and reflex sympathetic dystrophy. The related pathways include ligand-gated ion channel transport and trans-chemical synaptic transport . SCUBE3 (Signal Peptide, CUB Domain and EGF Like Domain Containing3) is a Protein Coding gene. Diseases related with SCUBE3 include Facial Dysmorphism, Short Stature and Skeletal Anomalies With Or Without Cardiac Anomalies 2 and Bone Disease.The gene encodes signal peptides, complement subcomponent C1r/C1s, Uegf, bone morphogenetic protein-1 as well as epidermal growth factor-like domains. Both full-length protein as well as the C-terminal fragment bind transforming growth factor TYPE II receptors to enhance epithelial-mesenchymal transformation and angiogenesis in tumors . HLF (Hepatic leukemia factor), a transcriptional factor, plays an significant regulatory function in various tumors, particularly leukemia and participates in therapy-mediated immunogenic cell death. RFLNB, a member of the Refilin family, is a novel Actin regulatory protein that functions as molecular switches for interconverting the Actin meshwork into bundles.
One major trait of this regulatory protein is its short half-life, unique among Actin regulatory proteins. So far, no studies have shown that these seven genes (IGHG2, PODXL2, LRRC17, GABRA3, SCUBE3, HLF, RFLNB) are directly related to pyroptosis in tumor cells. We first proposed these seven genes and analyzed their function and significance in sarcoma.
We investigated the expressions of 33 known pyroptosis-associated genes in Sarcomas, analyzed the relationship between each two genes, and investigated their correlation with clinicopathological features. To assess the association between expressions of 33 pyroptosis-related genes and Sarcoma subtypes, the NMF algorithm was used to cluster 262 Sarcoma samples in the TCGA dataset. Although the two clusters generated by DEGs-based consensus clustering analysis did not reveal marked variations in clinical features, the overall survival rate in the two clusters has obvious differences, patients with the pyroptosis-related genes exhibited a significantly poor overall survival rate, relative to those without pyroptosis-associated genes. In the current study, the IC50 of the 65 drugs in the high-risk group were markedly low, compared to low-risk group, indicating that these drugs may be suitable for high-risk patients.
To determine the underlying mechanisms of different sensitivities of drugs to the high- and low-risk groups, we applied GSEA to our model. Functional analyses revealed that DEGs between low- and high-risk groups was associated with immune and musculoskeletal pathways. We compared the pathways related to infiltration and activation of immune cells in low- and high-risk patient groups, and found that the number of infiltrating immune cells as well as activation levels of immune-associated pathways were generally low in high-risk group, relative to the low-risk patient group. Moreover, we also compared the top 30 mutated genes in low- and high-risk patient groups. Among them, mutations of TP53, RB1 as well as MUC16 markedly differed between the groups.
Until now, few studies have clearly shown the significance of pyroptosis, particularly its functional mechanisms in sarcomas. We identified seven genes that may have a critical impact on pyroptosis in sarcomas and may serve as regulatory factors. We evaluated the prognostic significance of these pyroptosis-related genes and gave a theoretical basis for subsequent studies. Taken together, our study suggests that pyropwe were unable to confirm whether those previously reported regulatory factors also have similar fuction in the pyroptosis pathway of Sarcoma for lack of data, which deserves further study and experimental verification.
Taken together, our research suggests that pyroptosis is closely associated with Sarcoma, which is evidenced by the results that genes associated with or unrelated to pyroptosis are expressed differently in Sarcoma tissues. In addition, our score based on risk signature generation of seven pyroptosis-associated genes is an independent risk factor for OS prediction in TCGA cohort. DEGs between low-risk and high-risk patient groups are correlated with tumor immunity and mutations, as well as skeletal muscle pathways. Our study gives a new genetic feature for prognostic prediction of Sarcoma patients, and forms a theoretical basis for the studies on of pyroptosis-associated genes in Sarcoma patients in the future.