Scientists testing the effects of microbeams, streams of helium ions a thousandth of a millimeter wide, have discovered that targeting just a few cancer cells with the beams can cause massive destruction to other diseased cells. Scientists at the United Kingdom's Cancer Research U.K. group have dubbed it the "bystander effect" because the cancer cells zapped by the microbeams not only die but also send out suicide signals to other abnormal cells, telling them to self-destruct. "We used to assume that the only way to kill cancer cells with radiotherapy was to hit every one of the cells in the tumor with a fatal dose of radiation," said researcher Kevin Prise. "Now we're finding that it's possible to hit just a handful of cells with much lower doses and let the cells' natural suicide machinery do the rest." The scientists said the bystander effect is linked to a molecule called nitric oxide that plays a role in cell suicide. Nitric oxide seems to be important in sending out suicide signals in cells when they are hit by radiation.
Prise and his colleagues, who reported their findings in the journal Cancer Research, tested microbeams in the laboratory on brain cancer cells that were highly resistant to conventional radiotherapy. Although they targeted the beam at a single cell, it had an impact and triggered a significant proportion of other cells to commit suicide in a process known as apoptosis. Cancer develops when abnormal cells do not self-destruct but continue dividing and form tumors. "If we could enhance the bystander effect within tumors, we could develop much more effective systems of radiotherapy, perhaps using lower doses to reduce side effects," Prise said. An estimated 50% of patients diagnosed with cancer would benefit from radiotherapy, which kills cancerous cells with tight beams of radiation aimed at specific areas of the body. Radiation is commonly used to treat breast cancer, for which lesbians have been shown to be at a higher risk.