The reduced extracellular calcium requirement for proliferation by neoplastic hepatocytes.

Cells from neonatal rat livers were unable to maintain DNA-synthetic activity in calcium-deficient medium, but neoplastic hepatocytes from Morris hepatomas 5123 tc and 7795 synthesized DNA and proliferated indefinitely in this calcium-deficient medium. The calcium content of fresh hepatoma tissue from which these cultures were derived was as much as 10 times greater than that of normal liver; but this difference could not account for the insensitivity of neoplastic cells to extracellular calcium because it disappeared during subsequent cultivation in vitro.