Bystin, as a cytoplasmic protein encoded by BYSL, binds directly to trophinin and tastin [1], that has been defined as a sensitive marker for astrocyte proliferation during brain damage and inflammation. BYSL has been reported to mediates homogenous adhesion between trophoblast and endometrial epithelial cells [11, 12], and participates in a series of biological processes such as embryo implantation [13], cell population proliferation [3, 4, and 14], ribosomal biogenesis [13], and ribosomal biogenesis [13]. Studies have continuously reported the functional relationship between BYSL and tumors [3, 14, and 15]. However, no literature on the pan-cancer analysis of BYSL from the perspective of the whole tumor has been retrieved. Therefore, we conducted the analyzation of BYSL gene in 33 tumors based on TCGA, CPTAC, GEO database, with a series of bioinformatics tools. These comprehensive tests include gene expression, survival prognosis, genetic changes, protein phosphorylation, DNA methylation, immune infiltration, and associated cellular pathways.
Many studies have shown that BYSL upregulates in a series of tumors. Ayala et al. found that Bystin overexpressed in human prostate cancer cells with perineural infiltration, and showed a gradient increase [16]. The expression levels of BYSL mRNA significantly increased in human hepatocellular carcinoma (HCC) specimens. BYSL siRNA in HCC in vitro and vivo showed cell growth stagnation and inhibition of tumor formation, and suggesting that the up-regulation of BYSL expression may lead to the occurrence of HCC [17]. BYSL expression is also enhanced in glioma tissues. siBYSL could inhibit the proliferation of glioma cells, and the progress of the cell cycle, and induce apoptosis. Furthermore, studies showed that a signaling pathway connected to GSK-3β/β-catenin was necessary for BYSL to promote GBM cell migration, invasion, and EMT [4]. Consistent with our results, BYSL expression was higher in most tumor tissues except for the LAML.
High BYSL level has been found to shorten the progression-free survival in cancer patients [18]. By exploring the TCGA database, we also found that high expression of BYSL corresponds to the poor prognosis of ACC and LICH. Previous studies have demonstrated that high trophinin expression in COAD patients is associated with poor prognosis [19], and BYSL plays an important role in directly binding trophinin and tastin [15], so maybe high BYSL expression is related to TNM staging. BYSL over-expressed in STAD. The overexpression of BYSL is associated with an improved prognosis in STAD, but additional molecular experimental evidence is needed to confirm that it plays a critical role in STAD development. BYSL may be a potential biomarker for predicting prognosis for cancer patient in clinic. To verify the clinical value of BYSL in tumor diagnosis, we further performed a ROC curve analysis. The results also showed that BYSL had a significantly higher AUC value in a variety of tumors. Therefore, we conclude that BYSL can be a potential diagnostic biomarker to distinguish tumors from corresponding normal tissues.
The types of genetic variation include mutation, structural variation, amplification, deep deletion, and multiple changes. We found that "amplification" is the dominant form of BYSL variation in all tumors. "Amplified" is the characteristic variant form of all ESCA, DLBC, CHOL, UVM, PAAD, KIRP, UCS, MESO, ACC, LGG, TGCT, GBM, and KIRC.
Phosphorylation is essential for protein regulation [20], which usually occurs at residues of serine (S), threonine (T), and tyrosine (T) substrates, and induces conformational changes in many proteins, leading to activation or inhibition of proteins, resulting in different biological functions [21]. CPTAC dataset analysis revealed the molecular mechanisms of bystin in tumors from the perspective of protein phosphorylation. Additionally, the phosphorylated level at the S98 locus was higher in most primary tumors than normal issues. Those results indicate that BYSL total protein phosphorylation is closely related to tumorigenesis and development. However, the potential role of specific site phosphorylation in tumorigenesis needs further experimental investigation.
In TCGA patients, we observed a negative correlation between BYSL DNA methylation in the non-promoter region and the high expression of BYSL in most tumors. Hypermethylation of BYSL at the CG01526854 3 'UTR site was significantly associated with poor prognosis in COAD patients. BYSL methylation significantly correlated with TILs in human tumors. Therefore, BYSL DNA methylation may play a specific role in the immune invasion of various human tumors, and the potential role of BYSL DNA methylation in tumorigenesis deserves further study.
CD8 + T cells (TC or CTL cells) is a sub clones of T lymphocyte cells, which has been found can kill target cells expressing the antigen and play a crucial role in immune defense against intracellular pathogens such as bacteria, viruses, and tumors [22]. Loss of CD8 + T cells disrupts antitumor immunity and increases sensitivity to tumor growth [23]. Early studies have shown that effector CD8 + T cells in the TME can generate IL-2, IL-12, and IFN-γ, which enhance the cytotoxicity of CD8 + T cells and lead to targeted tumor cell killing [24, 25]. Elevated levels of cytotoxic CD8 + T cells in the TME are associated with antitumor effects and improved prognosis of numerous cancers [26, 27]. Currently, no studies have been conducted on BYSL and TME. For the first time, our results show a negative correlation between BYSL expression and CD8 + T cells in HNSC-HPV, SKCM and SKCM-metastasis, and high BYSL expression is associated with low CD8 + T cell levels. It is likely that this will result in a reduced anti-tumor immunity and weakened ability to target and kill tumors, which is consistent with the above analysis results showing that high BYSL expression correlates with poor prognosis of cancer patients.
BYSL plays an important role in ribosome production and cell growth. BYSL can interact with mTORC2 and increase the synthesis of ribosomal proteins (such as S6) through the Akt-MTORC1-P70S6K pathway, mediate the survival and proliferation of glioma cells [14]. BYSL is present at multiple stages of nucleogenesis, including nucleolus-derived foci (NDF), perichromosomal regions, and the prenucleolar body (PNB) during mitosis [1, 28]. BYSL consumption significantly inhibits the formation of NDF and PNB, and destroys nucleolar assembly after mitosis, leading to increased apoptosis [3]. GBM tissues expressed highly WNT and β-catenin [29], and which is involved in glioma cell invasion and EMT [30, 31]. As a result of its overexpression, BYSL increases the phosphorylation level of GSK-3β and the nuclear distribution of β-catenin in GBM cells, and promotes the expression of EMT markers and cell migration or invasion of these cells [4]. BYSL, in combination with these previous studies and the findings of our analysis, may prove to be a promising biomarker for diagnosing most tumors, distinguishing them from healthy tissue, and serving as an effective target for the development of anti-tumor drugs. Novel small molecules or anti-body drug can be designed and synthesized by its high selectivity and better binding properties that target the pathway's upstream driver, such as BYSL. It may mechanically regulate the cell cycle and result in tumor cell death through AKT-mTOR, GSK-3β/β-catenin, and other molecular mechanisms. Furthermore, biomedical treatments may reduce toxicity resulting from molecular combinations, cancer patients may be treated in a more precise manner.