The results were stunning. The mice given daily injections of CLT had, on average, fewer than eight metastases in the lungs. Although exciting, the results were also puzzling. In a series of experiments, the HMS researchers subsequently found that CLT also depletes the cell's storage of calcium. Normally, calcium levels are under tight control in the cell.
Most calcium is stored away in a cell compartment known as the endoplasmic reticulum.
When the cell is exposed to a growth factor, these stores of calcium are released into the cytoplasm. The calcium is then either quickly pumped out of the cell through the cell membrane, or returned to the reservoirs in the endoplasmic reticulum. The system is very tightly regulated, Halperin says. If the calcium stored in the reservoirs does not return to its normal levels, channels in the cell membrane open and let in more calcium. CLT interferes with this storage system, the HMS researchers discovered.