Proliferation of NSO cells in protein-free medium : The role of cell-derived proteins, known growth factors and cellular receptors

• NSO cells proliferate without external supply of growth factors in protein-free media. We hypothesize that the cells produce their own factors to Support proliferation. Understanding the mechanisms behind this autocrine regulation of proliferation may Open for the novel approaches to improve animal cell processes. The following proteins were identified in NSO conditioned medium (CM): cyclophilin A, cyclophilin B (CypB), cystatin C, D-dopachrome tautomerase, IL-25, isopentenyl-diphosphate delta-isomerase, macrophage migration inhibitory factor (MIF), beta(2)-microglobulin, Niemann pick type C2, secretory leukocyte protease inhibitor, thioredoxin-1, TNF-alpha, tumour protein translationally controlled 1 and ubiquitin. Further, cDNA microarray analysis indicated that the genes for IL-11, TNF receptor 6,TGF-beta receptor 1 and the IFN-gamma receptor were transcribed. CypB, IFN-alpha/beta/gamma, IL-11. IL-25, MIF, TGF-beta and TNF-beta as well as the known growth factors EGF, IGF-1/11, IL-6, leukaemia inhibitory factor and oncostatin M (OSM) were excluded as involved in autocrine regulation of NSO cell proliferation. The receptors for TGF-beta, IGF and OSM are however present in NSO cell membranes since TGF-beta(1) caused cell death, and IGF-1/11 and OSM improved cell growth. Even though no ligand was found, the receptor subunit gp 130, active in signal transduction of the IL-6 like proteins, was shown to be essential for NSO cells as demonstrated by siRNA gene silencing.

Nyckelord

NSO myeloma cells

Autocrine growth factors

Regulation of

proliferation

Conditioned medium

gp130

migration inhibitory factor

multiple-myeloma

conditioned medium

defined protein

plasmacytomas

survival

cultures

gp130

mice

interleukin-6

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