TY  - JOUR
TI  - Endoscopic Collection and Analysis of Gastric Fluid DNA: A Liquid Biopsy Methodology for Tumor Biomarker Discovery
AU  - Cadoná, Francine Carla
AU  - Pelosof, Adriane G.
AU  - Bartelli, Thais F.
AU  - In, Haejin 
AU  - Wu, Lianlian 
AU  - da Silva, Israel Tojal
AU  - Pasqualini, Renata 
AU  - Arap, Wadih 
AU  - Nunes, Diana Noronha
AU  - Dias-Neto, Emmanuel 
VL  - 16
IS  - 17
PY  - 2026
DA  - 2026/09/05
SP  - e5809
C1  - Bio-protocol 2026;16:e5809
DO  - 10.21769/BioProtoc.5809
UR  - https://doi.org/10.21769/BioProtoc.5809
AB  - Gastric cancer remains a major global health challenge, and reliable prognostic biomarkers are urgently needed to guide treatment decisions. Here, we present a simple and efficient protocol for a novel liquid biopsy approach based on quantifying gastric fluid DNA (gfDNA) collected during routine esophagogastroduodenoscopy (EGD). We have previously shown that gfDNA carries gastric cancer–derived mutations; moreover, its concentration increases with tumor progression and varies according to cancer prognosis. This empirically observed increase in gfDNA may mechanistically stem from enhanced cellular turnover, tissue disorganization, dysbiosis of the local microbiota, and/or fluctuations in immune cell infiltrates. Surprisingly, however, in patients diagnosed with gastric cancer, elevated gfDNA levels were also associated with improved survival. This paradoxical finding may be reconciled by an increased anti-tumor immune cell response in treatment-responsive gastric cancers, as well as by the contribution of non-tumoral DNA from inflammatory processes within the microenvironment of the stomach. Here, we detail a standardized protocol for gastric fluid collection and processing, designed to support downstream gfDNA quantification among other potential molecular applications.
KW  - Gastric cancer
KW  - Gastric fluid DNA
KW  - gfDNA quantification
KW  - Liquid biopsy
KW  - Progression-free cancer survival
KW  - Tumor biomarker
KW  - Upper digestive tract cancer
JF  - Bio-protocol
SN  - 2331-8325
PB  - Bio-protocol LLC.
BIO101  - False