Alteration by malignant transformation of the calcium requirements for cell proliferation in vitro.

Cells from the thigh muscles of normal fetal rats proliferated rapidly and indefinitely in a medium containing adult rat "plasma" and a normal free-calcium concentration, but they could not proliferate in calcium-deficient plasma medium. As the animals grew older, the cells became increasingly less able to proliferate even in normal (high-calcium) plasma medium, though they retained the potential to proliferate in a more conventional medium containing fetal bovine serum. By contrast, neoplastic adult cells from malignant rhabdomyosarcomas (induced by Ni3S2) proliferated rapidly and indefinitely in both normal and low-calcium plasma medium