Stimulation of TNF-alpha production by 2-(1-adamantylamino)-6-methylpyridine (AdAMP) - a novel immunomodulator with potential application in tumour immunotherapy.

The immunomodulatory effects of a recently synthesized adamantane derivative of aminopyridine - 2-(1-adamantylamino)-6-methylpyridine (AdAMP) - were tested on normal and neoplastic cells in vitro. When incubated with TNF-alpha gene-transduced mouse melanoma cells (B78/TNF), AdAMP significantly enhanced basal production of TNF-alpha by these cells, both by "high" and "moderate" TNF-alpha-producer cells. A similar TNF-alpha production-enhancing effect was observed in cultures of human ovarian carcinoma cells (CAOV1) which spontaneously produce TNF-alpha but not in cultures of tumour cells incapable of TNF-alpha secretion. RT-PCR analysis showed that the enhancement of TNF-alpha production by AdAMP was associated with an increase in TNF-alpha mRNA expression in the treated cells. The results of an electrophoretic mobility shift assay (EMSA) showed that AdAMP significantly activated nuclear factor kappaB (NF-kappaB) in both CAOV1 and B78/TNF cells. The role of NF-kappaB in enhancement of TNF-alpha production was confirmed in experiments in which MG132, an inhibitor of NF-kappaB activation, reversed the effect of AdAMP. Unexpectedly, dexamethasone, a potent antiinflammatory agent and a strong inhibitor of TNF-alpha production in vivo, increased both spontaneous and AdAMP-augmented production of TNF-alpha in in vitro cultures of ovarian carcinoma cells and B78/TNF cells. AdAMP also enhanced TNF-alpha secretion by LPS-induced monocytes. AdAMP-induced augmentation of TNF-alpha production by B78/TNF cells was accompanied by morphological changes in the treated cells and a decrease in their adherence to fibrinogen and collagen IV. In view of these properties, AdAMP seems to be a therapeutically promising compound with potential application as an adjuvant augmenting the efficacy of cancer vaccine-based therapies or in the local treatment of certain tumours.