Purging of small cell lung cancer cells from bone marrow using immunomagnetic beads and a flow-through device

Immunomagnetic beads can be used to remove subpopulations of cells from a mixed cell suspension in a flow-through system. One application of this process is the removal of tumor cells from bone marrow prior to its use in autologous bone marrow transplantation (ABMT). Based on preliminary data showing that three monoclonal antibodies (MoAb) (SCCL 175, HNK-1, and TFS-4) gave optimal separation in small-scale experiments, we have designed a large-scale separator suitable for clinical use. In our separator, the cell suspension flows through a 150 ml baffled transfer pack which is held over an array of permanent magnets. Direct (one MoAb only) and indirect (MoAb and anti-mouse antibody) methods of binding beads to cells were investigated as were the effects of temperature, bead to cell ratio, and medium additives on tumor cell removal and normal cell recovery. We determined the optimal separation conditions to be the indirect method of binding at 22 degrees C using a bead to tumor cell ratio of 25:1. Testing of the device on DMS-273 small cell lung cancer (SCCL) cells mixed with normal human bone marrow mononuclear cells resulted in a mean tumor cell removal of 3.64 logs (99.977%) with a concomitant mean normal granulocyte-monocyte colony forming unit (CFU-GM) recovery of 61.3%. These experiments form the basis to use the immunomagnetic beads to purify bone marrow from patients with SCCL for use in ABMT.