Cloning efficiency of cultured human tumor cell lines measured with the use of a coulter particle counter

A technique is described by which colony formation in agarose may be rapidly and reproducibly determined with the use of a modified Coulter particle counter (CPC). The cloning efficiency of RD human rhabdomyosarcoma cells after exposure to vincristine sulfate or cisplatin has been compared with the CPC method or by conventional visual counting. These techniques give very similar results. In combination with a Coulter Channelyzer, the CPC technique can be used to evaluate drug effects in colony sizes from a median of 20 to greater than 290 cells. The integrity of colonies formed by 3 colon carcinoma cell lines was examined to determine if this method could be applied to other systems.