Several components of the tumor microenvironment were approved to create various compounds to regulate and participate in the progression of bladder tumor16. A recent study has revealed the signature of immune and stromal infiltration of MIBC could impact the treatment response and correlated significantly with the survival outcomes 9. However, given that the majority of BC are diagnosed as non-muscle-invasive and the patterns of immune and stromal infiltrates are varied among tumors, the necessity to investigate the correlation of immune and stromal infiltration with both non-muscle invasive and muscle-invasive bladder cancer as a whole would be elevated. Therefore, we employed the ESTIMATE algorithm, a method which has been verified to accurately predict the level of infiltration of immune and stromal cells in the tumor microenvironment across eleven types of tumors 5 and applied to effectively explore prognostic biomarkers in glioblastoma 6 and gastric cancer 7, to characterize the immune / stromal infiltration signature and screen potential biomarker for bladder tumors with 393 and 93 patients respectively identified from TCGA and GSE31684.
It has been reported that higher infiltration of immune cell was associated with the response of immune checkpoint blockade in metastatic bladder cancer 17, 18 and improved disease-specific survival in muscle-invasive bladder cancer receiving trimodality therapy 9. Despite the underlying mechanism still remains unclear, the studies imposed that treatment such as radiation could enhance immune-mediated tumor cells killing through promoting additional antigen release or chemokine secretion in the favorable microenvironment abundant of immune cells prior to treatment 19, 20. Similarly, regardless of treatment options, our study found that higher immune infiltration was correlated with improved overall survival of BC. In terms of the stromal infiltration, evidence has shown that the components of the stroma could contribute to the direct exclusion or inactivation of chemotherapy 21 and higher stromal infiltration signature was associated with worse survival after radical cystectomy 9. In consistent, we found that higher stromal infiltration was associated worse overall survival of BC. Moreover, our outcomes also indicated that the infiltration of stromal cell was associated with bladder tumor stage, supporting the idea that stromal cells play critical roles in tumor progression 1, 22.
Through the signature of immune and stromal infiltration, we found that multiple DEGs were associated with the prognosis of bladder cancer but EFNB2 was the only core prognostic gene after external validation with GEO dataset. EFNB2 encodes the B class ephrin, a kind of membrane-bound ligands that binds to Eph receptors that comprises the largest protein-tyrosine kinase receptor family. Several studies have reported the association of ephrin with tumor progression, invasion and migration23-25. Particularly, FENB2 was reported as a poor prognostic indicator of ovarian and esophageal squamous cell carcinoma 26, 27. Recent studies have also demonstrated the role of EFNB2 in bladder cancer by showing that higher expression of EFNB2 was associated with poorer survival with samples from Johns Hopkins Hospital 28. Moreover, they also claimed that FENB2 significantly correlated with TP53 mutation 28, a well-known tumor suppressor gene, and we performed GO enrichment analysis to find P53 signaling pathway was significantly associated with the core module genes. Another study also showed that EFNB2 is a part of the PPI network centered by fibroblast growth factor receptor 3 which TP53 was involved with as a TF 29. Together with previous evidences, our study might promote the role of immune/stromal infiltration and EFNB2 as predictors or therapeutic targets for bladder cancer.
The hypoxia inducible factor 1 alpha (HIF-1A or HIF-1α) functions as an essential regulator of the transcription of many genes involving tumor angiogenesis. Multiple studies have demonstrated the correlation between HIF-1A with bladder cancer 30-32. Earlier studies have reported that HIF-1A is associated with unfavorable prognosis of bladder cancer 30, 31, while a more recent research claims that the higher expression of HIF-1A can improve the local relapse-free survival of MIBC after radiation therapy plus carbogen and nicotinamide 32. Another study also states that HIF-1A might play a critical role in gemcitabine resistance of bladder cancer 33, supported by the evidence that the HIF-1A/MDR1 pathway confers chemoresistance to cisplatin in bladder cancer 34. Similarly, we found that HIF-1A plus IFR1, RUNX3 and STATS were TFs regulating the core module of bladder cancer. We then screened six kinds of drugs that could potentially impact bladder cancer including Carvedilol, FG-2216, ENMD-1198, PX-478, 2-Methoxyestradiol and Emricasan. Carvedilol is a beta-adrenoceptor antagonist which has been reported to be associated with reversal of the abnormal regulation of HIF-1A and reverse of multidrug resistance to anticancer drugs(good job) 35, 36, while FG-2216, ENMD-1198, PX-478 and 2-Methoxyestradiol are all inhibitors of HIF-1A 37-41. Emricasan, a caspase inhibitor and investigational drug for non-alcoholic steatohepatitis, was previously proven to be able to augment killing acute myeloid leukemia tumor cells by birinapant42. Our findings enhanced the idea that HIF-1A could be a potential target for the management of bladder cancer and provided more thoughts of alternative drugs treating bladder cancer.
This was the first study applying ESTIMATE algorithm in describing the immune and stromal infiltration signature BC. However, limitations should be noted before interpreting our findings. The first limitation is the retrospective nature of our study. With two independent public datasets employed for analysis, multi-institution samples would improve the reliability. Furthermore, samples that were used in this study were from the core region of the tumor tissue. Those tissue samples might alienate themselves from the samples that extrapolated from different parts of the tumor in other analysis. Together, Those limitations should suggest the potential of uncharted territories for future studies.