Differential effects of human blood monocytes on the growth of human tumour cell lines in vitro

Abstract

Monocytes and macrophages have been shown to be cytotoxic towards tumour cells in vitro. However, although tumour-associated monocytes and macrophages are now widely accepted to contribute a relatively high proportion of the cellular infiltrate of experimental and human solid carcinomas, a cytotoxic/cytostatic effector function for these cells in vitro or in vivo has yet to be conclusively demonstrated. In the present study, we show that non-activated peripheral blood monocytes co-cultured with tumour cells across a semi-permeable membrane release soluble factors that modulate the growth of tumour cells in contrasting ways. After Nycoprep 1.068 separation, non-activated peripheral blood monocytes enhanced the in vitro proliferation of HT29 colon adenocarcinoma cells but inhibited T47D breast carcinoma cell replication; peripheral blood lymphocytes were incapable of mediating these effects. In contrast, peripheral blood monocytes activated by interferon gamma caused a pronounced inhibition of both HT29 and T47D cell proliferation.

Tumour‐associated leucocytes: Friends or foes in breast carcinoma

“…Circulating monocytes have also been implicated in antitumour reactions inasmuch as soluble factors released by normal peripheral blood monocytes can induce cytostasis of breast carcinoma cell lines. 31 Despite promising effects in vitro, an antitumour effector function in vivo has not been convincingly demonstrated for macrophages infiltrating breast carcinoma. Cells with macrophage morphology containing mRNA for TNFa have been observed in close contact with malignant cells in areas of tumour necrosis.…”