In vitro effects of bone- and platelet-derived transforming growth factor-? on the growth of Walker 256 carcinosarcoma cells

Abstract

Conditioned media from fetal rat calvarial cultures has previously been shown to stimulate the growth of the bone-metastasizing Walker 256 carcinosarcoma cell line. In the current investigation we looked at the possibility that transforming growth factor-beta (TGF-beta), present in conditioned media, and positively correlated with resorption in vitro, may be responsible for the enhanced proliferation of Walker cells cultured in these conditioned media. Purified platelet-derived TGF-beta produced a dose-dependent growth response in Walker cells with an ED50 equal to 0.05 ng/ml. Bone-derived TGF-beta activity in conditioned media, measured by NRK fibroblast colony formation, correlated well with percentage resorption in bone cultures, and growth activity in Walker cell culture. In addition to this, the growth response normally seen with conditioned media cultures of Walker cells was significantly inhibited by the addition of anti-TGF-beta 1 neutralizing antibody. We conclude that TGF-beta is an important growth stimulatory component from fetal rat calvaria.

A quantitative model for spontaneous bone metastasis: evidence for a mitogenic effect of bone on Walker 256 cancer cells

“…An alternative possibility is that trabecular bone stimulates growth of the W256 cells in contact with them. This explanation would be consistent with reports that the products of resorbing bone can stimulate the chemotaxis [5,6,[11][12][13] and the growth [6,11,14] of W256 cells. Recently, factors released from bone fibroblasts have been implicated in the accelerated growth rate of human prostate cancer cells in nude mice [31].…”

“…Similar effects were also identified in conditioned culture media obtained from resorbing fetal rat calvaria. The ability of bone-derived conditioned media to stimulate growth and chemotaxis correlated directly with the extent of bone resorption [6,7,[11][12][13][14]. The responses of the W256 cells to conditioned media could be largely inhibited by the addition of anti-TGF-fl antibody [6,7].…”

Stimulation of bone resorption results in a selective increase in the growth rate of spontaneously metastatic Walker 256 cancer cells in bone

“…It has been previously demonstrated in vitro that Walker 256 carcinosarcoma cells exhibit chemotactic and mitogenic responses to the products of bone resorption, and that the magnitude of these responses correlate highly with the extent of resorption which had occurred in calvarial bone cultures [13,14]. We thus examined the possibility that the stimulation of bone resorption in vivo might result in the stimulation of growth of spontaneously metastatic W256 cells in bone.…”

“…This evidence includes the observation that the products of resorbing bone are mitogenic to W256 cells. It has also been shown in vitro that purified transforming growth factor-fl (TGF-fl), a polypeptide found in the greatest quantity in the skeleton, stimulates the growth of W256 cells in a dosedependent manner [13]. TGF-fl is a component of organic bone matrix [30], and is synthesized and secreted by osteoblasts [31].…”

“…The W256 rat tumor is of monocytoid origin [10], metastasizes aggressively to bone, and causes extensive osteolysis [11, 12, 12a]. The ability of conditioned media from bone organ cultures to stimulate the growth and chemotaxis of W256 cells correlated directly with the extent to which bones had undergone resorption [13,14]. In vivo, we have demonstrated that within the rat skeleton, spontaneously metastatic W256 cells located adjacent to trabecular bone had significantly greater uptake of [3H]thymidine, an index of growth rate, than did W256 cells located >50/zm from bone [12a].…”