Solid
tumors, particularly those involving the colon, breast, and lung, are the most common
tumors in humans. However, many technical difficulties exist in obtaining analyzable chromosomes from these
tumors, including the inability to stimulate cell division.
Phorbol-12,13-dibutyrate (PDBu) is a
tumor promoter that activates a variety of cellular responses, including proliferation. Using flow cytometry, we have demonstrated that PDBu acts as a
mitogen in primary cultures of colon
tumor cells. Based on these results, we developed a short-term culture technique that greatly improves the yield of analyzable metaphases from colon
tumors. Stimulated cultures consistently contained at least ten times more metaphases than unstimulated cultures, and chromosome morphology was improved. By modifying this technique with the addition of the
calcium ionophore A23187, we have successfully obtained analyzable chromosomes from the peripheral blood of normal individuals,
chronic lymphocytic leukemia patients, and a nodular
small cell lymphoma patient. These results demonstrate that mitogenic stimulation by PDBu is a valuable technique in the cytogenetic analysis of colon
tumors. By using PDBu alone or in combination with other agents, this technique may also be applicable to many other
tumors that are difficult to karyotype because of an inability to obtain mitoses.