A nude mouse with tumours (left); locations of the two China cancers
The trail to discovering
genes involved in two forms of cancer prevalent in Hong Kong and China
is being blazed at The Hong Kong University of Science and Technology
(HKUST). Researchers are using techniques in molecular genetics to search
for the genes that normally suppress tumour activity.
have already found at least two in chromosome 3 that are definitely involved
and another 17 that are suspect because of their mapping positions,
said Principal Investigator Professor Maria Li Lung.
method used involves transferring normal human chromosomes, which comprise
many genes, into human cancer cells. The subsequent hybrid cells are tested
to see whether they induce cancer in a mouse. Cancer development is halted
if tumour suppression genes from the normal transferred chromosome complement
defective genes in the original cancer cells.
said: The suppression genes are very important; not only should
they be present and active in preventing tumours, they control cell cycles,
telling the cell whether to keep dividing or to die. If the tumour suppression
genes are knocked out or lost, then the cell goes awry.
The two cancer
forms of particular interest to Prof Lung are nasopharyngeal carcinoma
(NPC), sometimes referred to as the Guangdong Cancer, and oesophageal
carcinoma (ESC) which has the highest incidence in the world in Chinas
Hebei province. The cancers also have a high mortality rate in Hong Kong.
NPC attacks the nasal-pharynx area. ESC, which has a lower incidence rate
but is more deadly than NPC, occurs in the oesophagus.
As with other
cancers, both are caused by defective genes which may have been inherited
or damaged by factors such as a diet high in carcinogens, pollution, or
even medication. Prof Lungs molecular research is the first of its
kind for NPC and, of the bodys 23 pairs of chromosomes, she and
her researchers have homed in on four: chromosomes 3, 9, 11 and 14.
genes have been implicated for chromosomes 3, 11 and 14. For chromosome
9, a known tumour suppressor gene, p16, is involved. Another important
find has been that chromosome 17 is not involved in NPC although within
it resides one of the most common tumour suppressing genes.
research method is to inject established cancer cells prepared from an
NPC patient under the skin of a nude mouse which has no thymus
and is therefore immune deficient. Without intervention, tumours begin
to grow within a couple of weeks. If a normal human chromosome with intact
tumour suppression genes is fused with the cancer cell, tumour development
if the tumour suppression genes are defective, tumours will continue to
Prof Maria Li Lung: email@example.com