No abstract

Classical anticancer therapies often are ineffective in patients with malignant glioma who have a survival of <1 year. Our previous studies showed a potent inhibitory effect of melatonin on glioma cell proliferation. This effect seems to be mediated by the well-known antioxidant properties of this molecule and the negative regulation of some intracellular effectors, such as the kinase Akt or the transcription factor nuclear factor (NF)-kappaB. Finally, protein kinase C (PKC) also seems to be implicated in this effect although the intracellular pathways involved have not been elucidated. In this study, we analyzed the role of PKC in the regulation by melatonin of intracellular effectors leading to inhibition of cell proliferation. Activation of PKC by incubation with triphorbol ester acetate (TPA) blocks the inhibitory effect of melatonin on Akt and NF-kappaB activity. Moreover, incubation with melatonin induces a decrease in p21 expression in these cells that is partially blocked by co-incubation with TPA. Taken together, these results suggest that melatonin's oncostatic effect on glioma cells is mediated, at least in part, by the inhibition of PKC activity which, in turn, results in Akt and NF-kappaB activity inhibition and modulation of cell cycle-related gene expression.

Studies on metastasic lesions from human carcinomas are scarce. Therefore there is a need for such studies to identify the expression of the biological factors that will help in the assessment of the natural history of breast cancer. Here an immunohistochemical study was performed using tissue arrays and specific antibodies against matrix metalloproteinases (MMPs)-1, 2, 7, 9, 11, 13, 14 and tissue inhibitors of metalloproteases (TIMPs)-1, 2 and 3 in 39 patients with breast cancer. Specimens from 39 patients with node-positive carcinomas were examined and the analysis was performed at the central core of the tumour, at the invasive front, and in the metastasic axillary lymph nodes (MALNs). Global expression of MMP-1, 7 and 14, TIMP-1, and 3, were significantly higher at the centre of the tumour compared with the invasive front or the MALNs. Significantly higher expression of MMP-7 and 14, and TIMP-3, by fibroblast-like cells and mononuclear inflammatory cells (MICs) was seen in MALNs. In addition, in the tumour centre, the expression of MMP-11 and TIMP-1 and 2 by MICs, as well as TIMP-2 expression by fibroblast-like cells, were associated significantly with the occurrence of distant metastasis. In contrast, TIMP-3 expression by tumour cells or by fibroblast-like cells in this same tumour locations, as well as TIMP-1 expression by fibroblast-like cells at the invasive front, were associated significantly with poor prognosis. However, the expression of all of these biological factors in MALNs was not associated with the development of distant metastasis. Our data suggest that there is prognostic relevance to the expression of MMPs and TIMPs in the stromal cells of primary tumours, rather than to the expression of these enzymes in MALNs.