The CM cell line derived from liver metastasis of malignant human insulinoma is not a valid beta cell model for in vitro studies

The CM cell line is derived from the ascitic fluid of a patient with liver metastasis of a malignant insulinoma. Insulin levels potentially derived from the insulinoma were detected only once in vivo in the subject with the malignant pancreatic tumor and hypoglycemia. After multiple unsuccessful attempts to detect insulin in the culture medium, insulin levels were again detected only once in vitro. In our repeated experiments, we extensively exposed early-passages of the CM cell line to 0.91 mM glucose and acutely to increasingly higher glucose concentrations (2.75, 5.5, 1 1, and 22 mM) and did not detect any insulin secretion as well as any significant insulin cell content. The electronic microscopic examinations of several vials containing early-passages of the CM cell lines showed a polyclonal nature of the cells mostly resembling fibroblasts. The karyotype detected severe and consistent chromosomal aberrations of the CM cell line, including the chromosome 11 tetraploidy and the genetic material translocation in three out of four chromosomes 11 at the insulin gene locus 11p15.1. These data, unfortunately, exclude the possibility of considering the CM cell line as a valid beta cell model in vitro.