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Relationship between amine-carboxyboranes and TNF alpha for the regulation of cell growth in different tumor cell
M C Miller1, C M Woods, M E Murphy
1Division of Medicinal Chemistry and Natural Products, School of Pharmacy, University of North Carolina, Chapel Hill 27599-7360, USA.
Abstract:
The amine-carboxyboranes were shown to be synergistic with tumor necrosis factor alpha (TNF alpha) in cytotoxicity and inhibition of DNA synthesis in select types of cancer cells depending on the presence of a TNF alpha high affinity receptor on the membrane of the cell. Initially both TNF alpha and the amine-carboxyboranes reduce the influx of calcium but later cause a significant increase intracellularly. This influx is not linked with the amine-carboxyborane activating the calcitonin receptor in the tumor cells. Neither the agents nor TNF alpha directly inhibits DNA topoisomerase II activity but both did cause decreased phosphorylation of the enzyme by protein kinase C (PKC). The two agents caused synergistic inhibition. This event correlated with increased DNA protein linked breaks, DNA fragmentation and cell death. These protein linked breaks are additive with etoposide's effects but the latter agent's mechanism is different than phosphorylation of topoisomerase II. There was no evidence that the DNA fragmentation was caused by a calcium induced endonuclease enzyme in these cancer cells. The low-molecular weight amine-carboxyboranes appear to play an identical function as TNF alpha in its role to cause DNA breaks and fragmentation to cause apoptosis.
Insights
Amine-carboxyboranes and tumor necrosis factor alpha (TNF alpha) synergistically induce cancer cell death by promoting DNA breaks and fragmentation. This occurs through decreased enzyme phosphorylation, not direct enzyme inhibition.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- Tumor necrosis factor alpha (TNF alpha) is a cytokine involved in inflammation and apoptosis.
- Amine-carboxyboranes are a class of compounds with potential therapeutic applications.
- The interplay between TNF alpha and other agents in cancer cell death pathways is an area of active investigation.
Purpose of the Study:
- To investigate the synergistic effects of amine-carboxyboranes and TNF alpha on cancer cell cytotoxicity and DNA synthesis.
- To elucidate the molecular mechanisms underlying the observed synergy, focusing on calcium influx, enzyme activity, and DNA damage.
- To determine the role of amine-carboxyboranes in cancer cell apoptosis.
Main Methods:
- Cytotoxicity assays were performed on cancer cells with varying TNF alpha receptor expression.
- Intracellular calcium levels were measured following treatment with TNF alpha and amine-carboxyboranes.
- DNA topoisomerase II activity and protein kinase C (PKC)-mediated phosphorylation were assessed.
- DNA damage (protein-linked breaks, fragmentation) and cell death were quantified.
Main Results:
- Amine-carboxyboranes exhibited synergy with TNF alpha in killing cancer cells expressing high-affinity TNF alpha receptors.
- Both agents initially decreased, then significantly increased intracellular calcium, independent of calcitonin receptor activation.
- Synergistic inhibition of DNA synthesis was observed, correlated with decreased topoisomerase II phosphorylation by PKC, increased DNA protein-linked breaks, fragmentation, and cell death.
Conclusions:
- Amine-carboxyboranes and TNF alpha act synergistically to induce apoptosis in susceptible cancer cells.
- The mechanism involves modulation of calcium signaling and decreased phosphorylation of DNA topoisomerase II by PKC, leading to DNA breaks and fragmentation.
- Low-molecular-weight amine-carboxyboranes appear to mimic TNF alpha's role in inducing DNA damage for apoptosis.