Thursday, April 22, 2010

HAMLET (found in breast milk) may target molecules in specific membrane regions.....

We know that HAMLET (human α-lactalbumin made lethal to tumor cells) is a molecular complex of α-lactalbumin and oleic acid (see structure courtesy : Lunds Univ). It induces apoptosis in tumor cells, but normal differentiated cells are resistant to its effect . The activity of HAMLET was discovered by serendipity, while using human milk fractions to investigate bacteria adherence to lung carcinoma cell lines. In addition to blocking adherence, one milk fraction actually killed the cells by inducing apoptosis. Cell death was accompanied by changes in morphology, nuclear condensation, cytoplasmic blebbing, and formation of apoptotic bodies, similar to cells that undergo classical apoptosis.
Further studies showed that HAMLET comprises a protein and a fatty acid that are both found naturally in breast milk. So far, however, it has not been proven that the HAMLET complex is spontaneously formed in the milk. It is speculated, however, that HAMLET can form in the acidic environment of the babies´ stomachs. Laboratory experiments have shown that HAMLET kills 40 different types of cancer, and the researchers are studying  its effect on skin cancer, tumours in the mucous membranes and brain tumours. Importantly, HAMLET kills only cancer cells and does not affect healthy cells.
Although the substance was found several years ago, it is only now that it has been possible to test it on humans. Patients with cancer of the bladder who were treated with the substance excreted dead cancer cells in their urine after each treatment, which has given rise to hopes that it can be developed into medication for cancer care in the future.
Researchers at the University of Gothenburg are focussed on how HAMLET can be taken up into tumour cells. Researchers  lead by,  Roger Karlsson attempting to gain an in-depth understanding of how the substance interacts with cell membranes. 
In their study, researchers examined the interactions of HAMLET with in vitro generated membranes of known composition, and compared HAMLET to the native or partially unfolded, fatty acid free proteins. They also examined the effect of HAMLET on plasma membrane vesicles (PMVs) obtained from tumor cells. Researchers could show that HAMLET interacts with membranes and disturbs their integrity under physiological conditions. Binding to intact tumor cell membranes showed a patchy distribution, indicating that HAMLET may target molecules in specific membrane regions.
Researchers conclude that, HAMLET engages membranes by a mechanism requiring both the protein and the fatty acid. HAMLET binding alters the morphology of the membrane and compromises its integrity, suggesting that membrane perturbation could be an initial step in inducing cell death...

No comments: