Technical Problems with Soft Agar Colony Formation Assays for In Vitro Chemotherapy Sensitivity Testing of Human Solid Tumors: Mayo Clinic Experience

Abstract

Since publication of the revolutionary papers by Salmon and colleagues from Tucson which about 5 years ago suggested that primary human tumor cells could be cloned in soft agar culture and in vitro chemotherapy sensitivity testing reliably performed (Hamburger and Salmon 1977; Salmon et al 1978; Salmon 1980), scores of cancer research groups around the world have looked into this testing technique. The number of papers already published (Johnson and Rossof 1983) and the breadth and intensity of the studies presented in this volume bear witness to the profound interest in soft agar colony formation assays for primary human tumors which the work of Salmon and his colleagues has generated. My own laboratory at the Mayo Clinic began performing the “human tumor stem cell assay” of Hamburger and Salmon for human solid tumor samples in 1979. In recent years we have endeavored to study by this technique all the suitable human solid tumor samples removed from the operating rooms at Rochester Methodist Hospital and St. Marys Hospital in Rochester, Minnesota, the two large general hospitals associated with the Mayo Clinic. To date, we have studied over 4,500 separate primary human tumor samples for in vitro chemotherapy sensitivity testing using soft agar colony formation assays similar to that described by Hamburger, Salmon, and colleagues. Our laboratory at the Mayo Clinic also has been one of four laboratories selected by the United States National Cancer Institute to perform soft agar colony formation assays with primary human tumor samples in a drug-screening mode, looking for new anticancer agents. This somewhat extensive practical experience in performing soft agar colony formation assays for in vitro anticancer drug sensitivity testing of primary human tumor cells generated the opportunities during which my colleagues and I observed a variety of technical problems.