Abstract
Methylated septin 9 (SEPT9) has been approved for non-invasive screening of colorectal cancer (CRC), but data on monitoring of CRC is sparse. Droplet digital polymerase chain reaction (ddPCR), with higher detection precision and simpler quantification than conventional PCR, has not been applied in SEPT9 detection. We explored the role of SEPT9 ddPCR for CRC detection and to measure serial SEPT9 levels in blood samples of CRC patients before and 3-month after surgery. SEPT9 methylated ratio, methylated abundance, and CEA levels were all higher in CRC patients than normal controls (all P < 0.05). The area under the curve (AUC) for methylated ratio and abundance to detect CRC was 0.707 and 0.710, respectively. There was an increasing trend for SEPT9 methylated abundance from proximal to distal cancers (P = 0.017). At 3-month after surgery, both methylated abundance and ratio decreased (P = 0.005 and 0.053, respectively), especially methylated abundance in stage III and distal cancer (both P < 0.01). We have developed a ddPCR platform for the quantitative detection of plasma SEPT9 in CRC patients. SEPT9 methylated abundance had an early post-operative decline, which may be useful in monitoring of treatment response.
Highlights
Methylated septin 9 (SEPT9) has been approved for non-invasive screening of colorectal cancer (CRC), but data on monitoring of CRC is sparse
The SEPT9 methylation in CRC cell lines and cancer-adjacent normal tissues through Droplet digital polymerase chain reaction (ddPCR) was shown in Fig. S2, including the tenfold serial dulition assay for HCT116 cell line
SEPT9 has been used in the screening and diagnosis of CRC, this is the first study to evaluate the application of quantitative ddPCR for SEPT9 detection in CRC patients
Summary
Methylated septin 9 (SEPT9) has been approved for non-invasive screening of colorectal cancer (CRC), but data on monitoring of CRC is sparse. We explored the role of SEPT9 ddPCR for CRC detection and to measure serial SEPT9 levels in blood samples of CRC patients before and 3-month after surgery. SEPT9 methylated ratio, methylated abundance, and CEA levels were all higher in CRC patients than normal controls (all P < 0.05). Among various DNA methylated biomarkers, methylated SEPT9 in blood is the only one approved by the Food and Drug Administration (FDA) of the United States as a non-invasive method for CRC screening and has been evaluated in several studies on CRC diagnosis[16,17,18,19,20]. The currently available test is qualitative and its role in quantitative monitoring of CRC is less useful
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