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We have previously shown that the persistent activation of p42/p44MAPK is required to pass the G 1 restriction point in fibroblasts (Pagè s, G., Lenormand, P., L'Allemain, G., Chambard, J. C., Meloche, S., and Pouyssé gur, J. Mammalian cells express multiple mitogen-activated protein (MAP) 1 kinases that mediate the effects of extracellular signals on a wide array of biological processes. In eukaryotic cells, three distinct MAPK cascades have been described, which appear to be linked to separate signal transduction pathways resulting in the final activation of either p42/p44 MAPK

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Stimulation of fibroblasts with serum or purified growth factors leads to a dramatic induction of expression of both c-fos mRNA and protein within a few minutes, followed by activation of c-myc. This suggests that c-fos induction is a primary event and the earliest known effect on gene expression by growth factors.

The S/G2‐specific transcription of the human cdc25C gene is due to the periodic occupation of a repressor element (‘cell cycle‐dependent element’; CDE) located in the region of the basal promoter. Protein binding to the major groove of the CDE in G0 and G1 results in a phase‐specific repression of activated transcription. We now show that CDE‐mediated repression is also the major principle underlying the periodic transcription of the human cyclin A and cdc2 genes. A single point mutation within the CDE results in a 10‐ to 20‐fold deregulation in G0 and an almost complete loss of cell cycle regulation of all three genes. In addition, the cdc25C, cyclin A and cdc2 genes share an identical 5 bp region (‘cell cycle genes homology region’; CHR) starting at an identical position, six nucleotides 3′ to the CDE. Strikingly, mutation of the CHR region in each of the three promoters produces the same phenotype as the mutation of the CDE, i.e. a dramatic deregulation in G0. In agreement with these results, in vivo DMS footprinting showed the periodic occupation of the cyclin A CDE in the major groove, and of the CHR in the minor groove. Finally, all three genes bear conspicuous similarities in their upstream activating sequences (UAS). This applies in particular to the presence of NF‐Y and Sp1 binding sites which, in the cdc25C gene, have been shown to be the targets of repression through the CDE.(ABSTRACT TRUNCATED AT 250 WORDS)

We have identified a gene, fos B, encoding a nuclear protein of 338 amino acids presenting a 70% homology with c‐fos, whose expression is activated during G0/G1 transition. Growth factor stimulation of quiescent cells leads to a rapid and transient accumulation of fos B mRNA, with kinetics similar to those of c‐fos. The induction of fos B mRNA levels is in part due to a dramatic increase in the transcription of the gene. The half‐life of fos B mRNA is in the order of 10‐15 min. Both transcriptional activation and mRNA stability are substantially increased in the presence of protein synthesis inhibitors. Immunoprecipitation studies showed that fos B as c‐fos protein, forms a complex in vitro with c‐jun and jun B proteins in the absence of a target binding sequence. Gel retardation assays demonstrated that fos B protein positively influences the binding of c‐jun and jun B proteins to an AP‐1 binding consensus sequence, suggesting that fos B protein plays a role in control of gene expression.

Ovarian cancer is typically accompanied by the occurrence of malignant ascites containing large number of macrophages. It has been suggested that these tumor-associated macrophages (TAMs) are skewed to alternative polarization (M2) and thereby play an essential role in therapy resistance and metastatic spread. In our study, we have investigated the nature, regulation and clinical correlations of TAM polarization in serous ovarian cancer. Macrophage polarization markers on TAMs and ascites cytokine levels were analyzed for 30 patients and associated with relapse-free survival (RFS) in a prospective study with 20 evaluable patients. Surface expression of the M2 marker CD163 on TAMs was inversely associated with RFS (p < 0.01). However, global gene expression profiles determined for 17 of these patients revealed a mixed-polarization phenotype unrelated to the M1/M2 classification. CD163 surface expression also correlated with the ascites levels of IL-6 and IL-10 (p < 0.05), both cytokines induced CD163 expression, and their ascites levels showed a clear inverse association with RFS (p < 0.01). These findings define a subgroup of patients with high CD163 expression, high IL-6 and/or IL-10 levels and poor clinical outcome.

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