DNA in Blood Tracks Cancer Development and Response

They performed whole-exome followed by deep amplicon sequencing to validate and quantify several hundred somatic mutations.

Exome sequencing of tumor samples and additional sequencing of germline DNA (N1) was performed using commercially available kits. Genomic libraries were quantified using quantitative polymerase chain reaction (qPCR) and pooled for exome enrichment by hybridization using the TruSeq Exome Enrichment Kit and enriched libraries were quantified using qPCR and pooled for sequencing on the HiSeq 2500 (Illumina; San Diego, CA, USA). Targeted sequencing libraries were prepared using droplet-based PCR amplification for ThunderBolts Cancer Panel with specific modifications (RainDance Technologies; Billerica, MA, USA).

The team carefully studied small fragments of DNA from dying tumor cells that are shed into the blood, comparing them with DNA from the biopsy that was taken at the same point in time. The results show that the DNA in the blood samples matched up with that from the biopsies, reflecting the same pattern and timing of genetic changes appearing as the cancer developed and responded to treatment. The results provide the first proof-of-principle that analyzing tumor DNA in the blood can accurately monitor cancer within the body.

Carlos Caldas, MD, a professor of oncology and senior author of the study, said, “This definitively shows that we can use blood-based DNA tests to track the progress of cancer in real time. The findings could change the way we monitor patients, and may be especially important for people with cancers that are difficult to reach, as taking a biopsy can sometimes be quite an invasive procedure. We were able to use the blood tests to map out the disease as it progressed. We now need to see if this works in more patients and other cancer types, but this is an exciting first step.” The study was published on November 4, 2015, in the journal Nature Communications.

Related Links:
Cancer Research UK Cambridge Institute 
Illumina 
RainDance Technologies