Chemist finds compound that works against certain cancer cells
Grace Chua, Straits Times 15 Nov 08;
BLUE-GREEN algae is commonly considered a toxic nuisance, but to Dr Tan Lik Tong, it is a treasure trove of undiscovered medicine.
Dr Tan, a chemist specialising in marine natural products at the National Institute of Education, believes the blue- green algae could be key to the next blockbuster cancer drug.
He has found a compound from it that has toxic properties against breast and leukaemia cancer cells, and is working on accumulating a sufficient quantity for further testing.
Blue-green algae or cyanobacteria is a type of bacteria that produces energy from photosynthesis. The species he studies, Lyngbya majuscula, is common worldwide and can be found at Pulau Hantu.
Often known as fireweed, it can form poisonous algal blooms that smother coral habitats and give fishermen painful welts when they come in contact with them.
The algal blooms are caused by an excess of nutrients from sewage and litter. To prevent their growth, the National Environment Agency monitors cyanobacteria in our reservoirs and beaches. One difference in the cyanobacteria in Singapore is that it does not produce irritant toxins.
No one knows why, or what triggers cyanobacteria to produce toxins, but scientists believe the toxins to be a defence mechanism.
Dr Tan, 40, who obtained his PhD in medicinal and natural products chemistry from Oregon State University, is struck by cyanobacteria's range and variety of compounds. He says: 'It's a treasure trove of compounds.'
He has found at least a dozen chemicals - including six previously unknown to science - from Lyngbya majuscula here, and suspects there are at least 20 to 30 more to be discovered.
Lyngbya majuscula is plentiful in Pulau Hantu's lagoons and tidepools, Dr Tan says. On his annual collecting trips, he just wades into the lagoon at low tide, draws out clumps of the fibrous strands and fills his Nalgene bottles. He can collect up to six full bottles each time.
In his laboratory, individual chemicals are isolated from the algae and tests done to check for possible medical properties.
For instance, Dr Tan's lab found one compound - a cyclic peptide that he calls hantupeptin A, after its source - to be effective against breast cancer and leukaemia cells.
Worldwide, up to seven cyanobacterial compounds are currently undergoing anti-cancer clinical trials. For example, dolastatins are in Phase I and II clinical trials against lung and prostate cancer.
And these are just anti-cancer compounds. Dr Tan also hopes to test the compounds for anti-malarial activity.
Ultimately, he would like to study the effect of hantupeptin A and other compounds on cancer cells.
National University of Singapore marine biologist Chou Loke Ming says Dr Tan's work highlights the local potential for marine drugs, thanks to the region's high marine biodiversity.
'Dr Tan's work emphasises that we don't have to go to exotic places to look for new species to work on,' he says.
'Cyanobacteria occurs in our waters... and it is significant that such a largely-ignored species harbours natural products that have biomedical applications.'
