Alterations in growth requirements of kidney epithelial cells in defined medium associated with malignant transformation

The possibility has been investigated that 1) the supplements required for the growth of the Madin Darby Canine Kidney (MDCK) cell line in serum-free Medium K-1 are indeed requirements for the growth of normal kiney cells in vitro, and 2) that alterations in these growth requirements are associated with malignant transformation. Consistent with the hypothesis that MDCK cells resemble normal kiney cells in culture, primary cultures of baby mouse kidney epithelial cells grow in Medium K-1 and respond to the 5 components in the medium. The growth properties of Moloney sarcoma virus (MSV)-transformed MDCK cells in defined media hve been examined. Unlike MDCK cells, MSV transformed MDCK cells form tumors in adult nude mice. Although they still respond to the 5 factors in Medium K-1, the optimal dosage for insulin is lower for the MSV transformants than for MDCK cells. The MSV transformants also have an additional requirement for growth in Medium K-1 - fibronectin. Variants of MDCK cells have been isolated that have lost the PGE₁ requirement for growth in defined medium. These variant cells have acquired 1) the ability to form tumors in adult nude mice and 2) an alteration affecting cAMP metabolism, in addition to PGE₁ independence.