Potential ‘Universal’ Blood Test for Cancer
Investigators measure effects of UV light on leukocyte DNA
Scientists at the University of Bradford in the U.K. have devised a simple blood test that can be used to diagnose whether people have cancer.
According to an online article in the FASEB Journal, the Lymphocyte Genome Sensitivity (LGS) test will allow doctors to rule out cancer in patients presenting with certain symptoms, saving time and eliminating the need for costly invasive procedures, such as colonoscopies and biopsies. The method could also be used to evaluate patients who are suspected of having cancer that is difficult to diagnose.Early results have shown that the LGS test has a high degree of accuracy when diagnosing cancer and pre-cancerous conditions from the blood of patients with melanoma, colon cancer, or lung cancer. The test looks at leukocytes and measures the damage that is caused to their DNA when they are exposed to different intensities of ultraviolet A (UVA) light, which is known to harm DNA. The new study showed a clear distinction between the damage to leukocytes from patients with cancer, from patients with pre-cancerous conditions, and from healthy subjects. Lead investigator Professor Diana Anderson said: “White blood cells are part of the body’s natural defense system. We know that they are under stress when they are fighting cancer or other diseases, so I wondered whether anything measureable could be seen if we put them under further stress with UVA light. We found that people with cancer have DNA which is more easily damaged by ultraviolet light than other people, so the test shows the sensitivity to damage of all of the DNA — the genome — in a cell.” A total of 208 subjects provided blood samples, which were exposed to UVA light through five different depths of agar. The UVA damage was observed in the form of pieces of DNA being pulled in an electric field towards the positive end of the field, causing a comet-like tail. In the LGS test, the longer the tail is, the greater the DNA damage. The measurements correlated to the patients who were ultimately diagnosed with cancer (n = 58), to those with pre-cancerous conditions (n = 56), and to those who were healthy (n = 94). “Whilst the numbers of people we tested are, in epidemiological terms, quite small, in molecular epidemiological terms, the results are powerful,” Anderson said. “We’ve identified significant differences between healthy volunteers, suspected cancer patients, and confirmed cancer patients of mixed ages at a statistically significant level of P less than 0.001. This means that the possibility of these results happening by chance is 1 in 1,000. We believe that this confirms the test’s potential as a diagnostic tool.” A clinical trial is under way to determine the accuracy of the LGS test in predicting which patients referred by their general practitioners with suspected colorectal cancer would benefit from a colonoscopy — currently the preferred investigation method for this disease. Source: University of Bradford; July 28, 2014.