Identification and validation of core genes in tumor-educated platelets for human gastrointestinal tumor diagnosis using network-based transcriptomic analysis

Gastrointestinal (GI) tumors have increasing incidence worldwide with their underlying mechanisms still not being fully understood. The use of tumor-educated platelets (TEPs) in liquid biopsy is a newly-emerged blood-based cancer diagnostic method. Herein, we aimed to investigate the genomic changes of TEPs in GI tumor development and their potential functions using network-based meta-analysis combined with bioinformatic methods. We used a total of three eligible RNA-seq datasets, which were integrated using multiple meta-analysis methods on the NetworkAnalyst website, and identified 775 DEGs (differentially expressed genes; 51 up-regulated and 724 down-regulated genes) in GI tumor relative to healthy control (HC) samples. These TEP DEGs were mostly enriched in bone marrow-derived cell types and associated with gene ontology (GO) of "carcinoma" and could affect pathways of "Integrated Cancer Pathway" and "Generic transcription pathway" respectively for highly and lowly expressed DEGs. Combined network-based meta-analysis and protein-protein interaction (PPI) analysis identified cyclin dependent kinase 1 (CDK1) and heat shock protein family A (Hsp70) member 5 (HSPA5) to be the hub genes with the highest degree centrality (DC), being up-regulated and down-regulated in TEPs, respectively. GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that the hub genes were primarily related to cell cycle and division, nucleobase-containing compound and carbohydrate transport, and endoplasmic reticulum unfolded protein response. Additionally, the nomogram model suggested that the two-gene signature owns extraordinary predictive power for GI tumor diagnosis. Further, the two-gene signature was demonstrated to have potential value for metastatic GI tumor diagnosis. The expression levels of CDK1 and HSPA5 in clinical platelet samples were verified to be consistent with the results from bioinformatic analysis. This study identified a two-gene signature encompassing CDK1 and HSPA5 that can be used as a biomarker for GI tumor diagnosis and maybe even cancer-associated thrombosis (CAT)-related prognosis.What is the context? Gastrointestinal (GI) tumors are now responsible for the majority of cancer-related mortalities worldwide.In the majority of cases of cancer, curative treatments are not recommended at the time of diagnosis. In this case, early screening and diagnosis is very important for overall tumor prognosis. Liquid biopsy emerged as a newly introduced minimally invasive approach for cancer diagnosis by detecting blood analytes as tumor-educated platelets (TEPs). Compared to tissue-based biopsies, liquid biopsies are less invasive, easy to access, convenient for serial tracking and better in eliminating intratumoral spatial heterogeneity. In recent years, specific gene signatures have been identified for cancer diagnosis, prognosis and prediction based on gene profiling data of TEPs. However, most of these studies were performed on the independent platelet profile datasets published on the Gene Expression Omnibus (GEO) database, which may harbor enormous heterogeneity. Additionally, few study revealed TEP mRNA functions and roles in GI tumors. Therefore, there’s the need of using an integrated method to re-analyze these data, so we can gain new insights for GI tumor diagnosis.What is new? Herein, through network-based RNA-seq meta-analysis, we identified the CDK1-HSPA5 signature in TEPs that has the potential as a biomarker for diagnosing GI tumors. This is the first time, to our knowledge, that a shared transcriptional signature of tumor-educated platelets has been identified in human GI tumor patients based on meta-analysis. Additionally, we found the two-gene signature has potential value for metastatic GI tumor diagnosis. We also demonstrated that HSPA5 may have different roles in blood and tumor cells, so its expression deregulation in distinct types of tissue may have opposing diagnostic and prognostic values.What is the impact? Our work provides a novel biomarker for platelet-based GI tumor prediction and diagnosis, which may also be used as novel targets for thrombosis prevention during cancer development in the future.