Illustration of cancerous cells entering the circulatory system

CSUN biologist develops new method to detect cancer in its earliest stages

Knowing specific cancer-causing mutations offers the possibility to nip cancer in the bud — detecting and treating it before a tumor can proliferate and threaten healthy tissues. At the earliest stages, however, cells carrying cancer-causing mutations are very rare, so detecting them is effectively searching for a cancerous needle in a haystack of healthy cells. A new assay developed by CSUN Assistant Professor of Biology Christian Ruiz Rueda and collaborators at Weill Cornell Medicine offers to make that search a lot easier.

In a paper published recently in the journal Human Mutation, Ruiz Rueda and his collaborators report a new PCR-LDR-qPCR assay capable of detecting point mutations at a single-molecule resolution in the presence of an excess of wild-type DNA. The assay employs a specialized polymerase chain reaction method to target and amplify mutant DNA through multiple nested primer-binding regions. They also employ oligonucleotides designed to block wild-type, non-cancer-causing DNA sequences, include measures to prevent carryover contamination, and use spatial dilution of samples. The resulting assay can detect multiple mutations in the same position in the genome.

The authors report their method was capable of detecting several common cancer somatic mutations at a single molecule level — that is, finding just a single copy of a cancer-causing mutation in a sample containing many more copies of the non-cancer-causing version of the same gene. The assay is highly sensitive, specific, and robust, and they suggest that it could be potentially useful in liquid biopsies.

Image: Growing cancer cells (in purple) are surrounded by healthy cells (in pink), illustrating a primary tumor spreading to other parts of the body through the circulatory system. (Darryl Leja, National Human Genome Research Institute, NIH, via Flickr.)