NASHVILLE--An experimental high-speed clinical cell selection device has been shown to be capable of isolating a pure population of hematopoietic stem cells (HSCs), essentially free from cancer cells, and the machine's developer (SyStemix, Inc., Palo Alto, Calif) has received FDA allowance for an active IND (investigational new drug) for clinical testing of HSCs purified by cell selection in cancer patients who are undergoing transplantation.
Speaking at a scientific session of the American Society of Hematology (ASH) meeting, Chris Reading, PhD, said that the high-speed fluorescence-activated cell sorting (HS-FACS) process can isolate HSCs at speeds of 15,000 to 30,000 cells per second, five to 10 times faster than conventional sorters. The isolated HSCs retain the ability to self-renew and propagate, he noted.
The sorter can select HSCs, and thus deplete tumor cells simultaneously, and can process stem cells in large enough numbers to be of therapeutic value, Dr. Reading said. Although the mobilization of stem cells into the peripheral blood varies widely among patients, SyStemix expects to be able to sort the required number of cells for transplantation in a few hours.
Dr. Reading, director of cell procesing at Systemix, reported that in mobilized peripheral blood samples from multiple myeloma patients,processing with the high-speed sorter created a 90% pure population of HSCs.
In five such samples,flow cytometric analysis showed a tumor burden in the starting material of 100,000,000,000 cells (range,100,000,000 to 4,000,000,000). In ten such samples, after high speed cell sorting , myeloma cells were reduced to below the level of quantitation (1 in 1,000,000 or 0.001%).
The isolated HSCs are defined by the presence of cell-surface markers CD34 and Thy-1 (which are lost as a cell develops into a mature blood cell) and the absence of other surface markers found on lineage-committed or mature cells (lineage negative or Lin-).
In contrast to CD34+Thy+Lin- populations isolated in the SyStemix process, CD34+ populations, targeted in other cell selection devices, can be described as mixed populations that contain progenitor cells, a varying number of stem cells, and possibly cancer cells. It is the CD34+Thy+Lin- cell that is the self-renewing and pluripotent stem cell, he said.
