Serum withdrawal induces a redistribution of intracellular gelsolin towards F-actin in NIH 3T3 fibroblasts preceding apoptotic cell death

The intracellular distribution of gelsolin in NIH 3T3 cells was examined by immunostaining using affinity-purified polyclonal gelsolin antibodies before and after induction of apoptosis by serum withdrawal. Serum deprivation induced detachment of an increasing number of NIH 3T3 cells, but also apoptosis in attached cells as verified morphologically by chromatin condensation, nuclear fragmentation and labelling of their periphery by FITC-annexin V. Ongoing apoptosis was also demonstrated by activation of caspase-3 activity and chromatin cleavage into high-molecular-mass fragments, although no internucleosomal chromatin degradation (DNA-ladder formation) was detected. When cells were maintained in the presence of 10% foetal calf serum, gelsolin immunoreactivity was evenly distributed in the cytoplasm. No obvious co-localisation of gelsolin and the actin-containing stress fibres was detected under these conditions. At day one after serum withdrawal, a redistribution of gelsolin to actin filaments was detected within a few attached cells by double fluorescence staining. The number of cells exhibiting this redistribution increased at days two to four. In addition, the stress fibres increased in thickness and their length was continuously reduced. At day four, many cells contained shortened stress fibres, which had lost their longitudinal orientation. Additionally, the cytoplasm of a number of attached cells was highly condensed around their nuclei and a homogenous distribution of both gelsolin and actin was detected in the remaining cytoplasmic rim. Up to day two, these effects were reversible after re-addition of serum to attached cells. A similar redistribution of gelsolin immunore-activity was observed after induction of apoptosis by cycloheximide, but not after initiation of necrosis by hydrogen peroxide. In NIH 3T3 cells no alteration in the expression of gelsolin at the level of protein (Western blot) or specific mRNA (Northern blot) was observed after serum withdrawal. Using Western blotting, no proteolysis of gelsolin was detected up to day 4, although caspase-3 activity was found to have increased fivefold after serum withdrawal. These results suggested that in these cells F-actin severing might occur in the absence or advance of gelsolin cleavage by caspases. Intact gelsolin on its own may be sufficient for the dissolution of the microfilaments, since micro-injection of gelsolin into primary bovine lens cells led to a transient disappearance of the stress fibres and to a reduction of their attachment area to the substratum. In NIH 3T3 cells similar effects of micro-injected gelsolin were only observed at day one after serum withdrawal.

Molecular cloning of IGFBP-5 from SCLC cell lines and expression of IGFBP-4, IGFBP-5 and IGFBP-6 in lung cancer cell lines and primary tumours

We showed recently that insulin-like growth factor binding protein (IGFBP)-1, -2 and -3 are differentially expressed in lung cancer and permanent lung cancer cell lines. Elevated levels of IGF binding capacity in serum of lung cancer patients were also reported. The function and tissue specificity of IGFBP are still obscure but they are probably local regulators of IGF action. Here we show the expression of IGFBP-4 transcripts in 11/11 small cell lung cancer (SCLC) cell lines, in nine out of 11 non-small cell lung cancer (NSCLC) cell lines, in 11/11 lung tumour specimens (10 derived from patients with NSCLC and one from SCLC origin) and in normal lung. In addition we isolated IGFBP-5 cDNA from lambda gt10 libraries of SCLC cell lines. With this IGFBP-5 cDNA we detected transcripts of different lengths in seven out of 11 SCLC cell lines, in 11/11 lung cancer specimens but only in one out of 11 NSCLC cell lines and in normal lung. IGFBP-6 was not detected in northern analysis of any tested SCLC cell line but it was expressed in nine out of 11 NSCLC cell lines and in nine out of 11 human lung cancer specimens and in normal lung.

Differential expression of insulin-like growth factor binding proteins in human non-small cell lung cancer cell lines

The possible expression and secretion of insulin-like growth factor binding proteins (IGFBPs) by non-small cell lung cancer (NSCLC) cell lines was investigated and compared with possible IGFBP expression by primary NSCLC tumours. Cells growing under serum-free conditions released binding proteins with apparent molecular masses of 26-43 kD when analysed by a ligand blotting method under non-reducing conditions. Additionally, northern blot analysis of total RNA from NSCLC cell lines and tumours was performed using cDNAs coding for each of IGFBP-1, IGFBP-2, and IGFBP-3. This analysis revealed expression of all three mRNAs to varying degrees by all cell lines. In contrast all primary tumours analysed expressed predominantly IGFBP-2 and IGFBP-3 and none showed any evident expression of IGFBP-1. Both NSCLC cell lines and tumours synthesise IGFBPs but the pattern of expression differs significantly between cell lines and primary tumours.

Growth regulation by insulin-like growth factors in lung cancer

Lung cancer is a major health problem, with over 38,000 new cases expected every year in West Germany. A more complete understanding of the biology of lung cancer will hopefully lead to therapeutic modalities. The possible autocrine growth regulation in small-cell lung cancer and non-small-cell lung cancer has been demonstrated for bombesin/GRP, vasopressin, neurotensin, EGF/TGF alpha, transferrin-related peptides and insulin-like growth factors. This contribution concentrates on recent data concerning binding sites, growth promoting effects and secretion of IGFs in lung cancer cell lines. The production of IGF-binding proteins which were also produced by lung cancer cell lines modifies the autocrine/paracrine model for IGFs since then proteins can either enhance or inhibit the effect of IGFs on tumor growth.