Prediction and validation of circulating G-quadruplexes as a novel biomarker in colorectal cancer.

BACKGROUND: There are some problems in the clinical diagnosis of colorectal cancer (CRC), such as the difficulty in saving samples, so it is the most popular research work to develop a diagnostic index and method that is easy to obtain, convenient to save and stable. G-quadruplex (G4) is a unique structure found in DNA and it plays a crucial biological role in tumor formation. G4 is derived from DNA with good stability, and the DNA of serum samples is easy to obtain. Therefore, G4 has the potential as an ideal marker for CRC diagnosis. However, it has not received more attention.

METHODS: Through bioinformatics-based G4 mutation prediction in the genome, we discovered that the G4 quantity in SW480 cells was lower than that of the reference gene. However, it was unclear how the G4 quantity changed in the actual samples. We detected the G4 content by fluorescence in cells and human serum samples.

RESULTS: G4 content was significantly higher than that in NCM480 (P<0.001). To further explore the relationship between tumorigenesis and G4, we knocked out the TP53 gene in SW480 cells and found that the G4 content decreased significantly (64%) (P<0.001). The difference in G4 content is a key factor in distinguishing between normal and tumor cells. Furthermore, we detected G4 in serum samples from 27 healthy individuals and 27 patients with CRC and found that G4 was significantly increased in those with CRC (P<0.001) by 1.94 fold. We also evaluated the G4 model using receiver operating characteristic (ROC), with an area under the curve of 0.91, and found it to have excellent specificity and sensitivity.

CONCLUSIONS: The increased G4 is an important characteristic in patients with CRC and has clinical application value as a novel biomarker. The relationship between G4 and TP53 regulation may be a potential target for future cancer studies, and as attention to this area of research increases, the underlying mechanisms may be better understood, potentially benefiting clinical cancer treatment.