Background: To determine KRAS gene in circulating tumor DNA in comparison with histological grading through liquid biopsy in colorectal cancer patients.
Methods: This dual-centered cross-sectional study included 73 diagnosed patients of colorectal cancer at different grading levels [Grade I, well differentiated (n = 7, 9.5%); Grade II, moderately differentiated (n = 14,18.9%); and Grade III, poorly differentiated (n = 52, 70%)]. Blood was collected, and plasma was separated. ctDNA was extracted, using magnetic bead-based technique (MagMAX Cell-Free DNA kit). KRAS gene was quantified through qPCR. STRING database was used to find KRAS interactomes.
Results: Mean threshold cycle (CT value) of KRAS gene in Grade III samples showed significantly higher (P = 0.001) levels of ctDNA (2.7 ± 1.14) compared with Grade II and Grade I (3.1 ± 0.68, 2.3 ± 0.60), respectively. Grading characterization showed that rectal cancer (n = 22, 42.3%) with Grade III (68.8%) was more prevalent than colon and sigmoid cancer (n = 19, 36.5%, n = 11, 21%, respectively). STRING database showed 10 functional genes interacting with KRAS expressed as gene/proteins.
Conclusion: Liquid biopsy can be used to detect ctDNA in plasma of CRC patients and enabled to detect the KRAS gene by qPCR. The technique being less invasive and cost-effective is convenient for multiple biopsies in different cancers.
Keywords: Circulating tumor DNA; KRAS; colorectal cancer; liquid biopsy; qPCR.