A report in Washington on Feb 23 announced that U.S. researchers have developed a new blood test that has the capability to detect the earliest stages of cancer.
At the early stage of clinical development, researchers from Stanford University dispensed a drug called DNA minicircles to mice. The mice with tumors reacted by producing a substance while the tumor-free mice did not.
It was also easily detected, only taking 48 hours to manifest later in the blood.
The search for an effective and accurate cancer “biomarkers” in the blood or substances that show a foreseeable tumor has long been sought after. Yet, several tumor types naturally release characteristic substances which demand their own separate test, said Prof. Sanjiv Gambhir, the study’s senior author and chair of radiology and director of the Canary Center at Stanford for Cancer Early Detection.
Making it more confusing is its complexity since the substances are also often made in healthy tissues, so a positive test result doesn’t mean a person has cancer. Furthermore, a tumor, especially when it is a small one may, not produce enough of the said substance to be detected.
“This biomarker is a protein called secreted embryonic alkaline phosphatase (SEAP),” they said in a statement. “SEAP is naturally produced in human embryos as they form and develop, but it’s not present in adults.”
To deceive the mice’s cells into producing SEAP and ejecting it into the bloodstream, Gambhir and his colleagues used a DNA minicircle ; a tiny , synthetic, single-stranded DNA ring at 4.000 nucleotides in circumference, or about a millionth as long as the DNA strand that would make an outcome from stretching all 23 chromosomes of the human genome throughout .
They manipulated the DNA minicircle so that it would be triggered by a certain promoter, a short DNA sequence that only takes effect in cancer cells. When initiated, a reporter gene on the minicircle will produce the protein called SEAP, which can then be identified.
Researchers then injected the minicircles intravenously into two groups of mice. One had had human melanoma metastases and the other was tumor-free. They then measured SEAP levels in the animals’ blood in a sequence of days. After two days, SEAP was detected in the blood of mice with tumors but not with the tumor-free mice. In as early as 72 hours of post-injection, the indication began to decrease in strength, gradually disappearing into almost nothing within the next two weeks or more.