Washington (IANS): A single tumour-suppressing gene is a key to unravel how dormant ovarian cancer cells that persist after initial treatment, to reawaken years later, according to a new study.

The study found that expression of a gene called ARHI (aplasia Ras homolog member I) acts as a switch for autophagy, or self-cannibalisation, in ovarian cancer cells. Often a mechanism for cancer cell death, in this case "self-eating" acts as a survival mechanism for dormant cancer cells.

"Prolonged autophagy is lethal to cancer cells, but a little autophagy can help dormant cancer cells survive, possibly by avoiding starvation," said the study's co-author Robert Bast, vice-president for translational research at Texas University MD Anderson Cancer Centre.

"Dormant cells are a major problem in ovarian cancer, breast cancer and other malignancies," Bast said. "We often see ovarian cancer removed, leaving no remaining sign of disease. After two or three years, the cancer grows back. If any remaining cancer cells had continued to grow normally, the disease should have returned in weeks or months.

"So the assumption is that some cells remain dormant without dividing and without developing a blood supply, but the mechanism for this has not been well understood," Bast said.

Bast and colleagues focused on ARHI, a gene found in normal cells, but that is underexpressed in 60-70 per cent of ovarian cancers.

When normal levels of ARHI were restored to ovarian cancer cells in the laboratory, autophagy was induced and cancer cells died within a few days.

These findings were published in the Journal of Clinical Investigation.