GROWTH STIMULATION OF ROUS-SARCOMA VIRUS-TRANSFORMED BABY HAMSTER KIDNEY FIBROBLASTS IN A SERUM-FREE MEDIUM BY BIOTIN
Abstract
The role of biotin in growth stimulation of Rous-sarcoma virus-transformed BHK cells (RST) in a serum-free medium was studied. The cells could be maintained in continuous culture in a medium containing Eagle's Minimal Essential Medium, iron, non-essential and amino-acids and biotin (BMB). This medium is the simplest chemically defined medium to maintain a mammalian cell line in continuous culture. With biotin deleted from the medium (BM) the cells were arrested in G1. The addition of a serum lipid extract to BM (BM(.)L) also stimulated proliferation of cells arrested in G1 in BM, but the cells could not be maintained in continuous culture in BM(.)L. Avidin inhibited growth stimulation when added to BMB but did not inhibit growth when added to BM(.)L. Biotin stimulated rapid incorporation of ('14)C-acetate into total cellular lipids with the largest amounts of incorporation into phophatidylserine and cholesterol. The addition of serum lipids to BMB markedly enhanced multiplication. Biotin stimulated ('3)H-leucine incorporation into total proteins and the culture medium of RST cells apparently contained non-dialyzable components which enchanced growth stimulation of RST cells in serum-free media. The growth-stimulating components produced and released into the culture medium by RST cells could also induce colony formation of untransformed rat kidney fibroblasts in a semi-solid medium. These studies indicate that a RNA virus-transformed cell line can be maintained in continuous culture in a serum-free medium containing biotin and the cells are blocked in G1 when biotin is deleted from the medium. Biotin stimulates lipid synthesis and the production of growth-stimulating components which are involved in growth stimulation of these cells. The growth-stimulating components produced by the transformed cells can also induce the expression of the transformed phenotype by the untransformed cells.
Degree
Ph.D.
Subject Area
Biology
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