A class of compounds extracted from the Australian shrub Acacia victoriae could be part of the next wave of cancer-preventing drugs. These chemicals, called avicins, reduced the appearance of benign tumors in mice exposed to carcinogens and interfered with a protein that plays a key role in inflammation, according to two reports published in todays Proceedings of the National Academy of Sciences.
Cancer develops in steps. In skin tumors the process can start with a change in a single gene, such as H-ras. Oxidizing chemicals such as hydrogen peroxide accumulate, causing more mutations and changes in chromosome number, while inflammation sets in. Eventually, apoptosisorderly cell suicidefails, and these altered cells cut loose. But if the brakes are put on this process early enough, cancer need never arise. Avicins have already been found to counteract a few of these precancerous changes, but now some real potential has begun to show through.
Researchers from several institutions, including the University of Texas M. D. Anderson Cancer Center and Arizona State University, applied a potent skin cancer-causing agent found in cigarette smoke to the skin of mice, some of which had been pretreated with avicins. The pretreated rodents were 60 and 40 percent less likely to develop benign papillomas (an early sign of progressing cancer), depending on how the cancer-causing agent was applied, and had far fewer tumors than their untreated counterparts. These animals showed a marked decrease in mutations of the H-ras gene, changes in chromosome number, DNA damage from oxidative chemicals and inflammation, as well.
Elucidating part of this response to the pretreatment, avicins were found to keep the nuclear transcription factor kB (NF-kB) protein out of the nucleus, where it stimulates the immune system and inflammation and can inhibit apoptosis if left turned on. The researchers conclude that avicins could someday play an important role in staving off skin cancer and other cancers that follow a similar path
