University of Queensland researcher Professor Jeremy Jass has identified a third type of colon cancer.
In the process, he has devised a classification system for pathologists dealing with the disease.
Previously, scientists had differentiated between two main types of colon cancer - those with chromosomal instability and those with DNA instability.
In research recently published in GUT - the Journal of the British Society of Gastroenterology - Professor Jass outlined a third type of colon cancer displaying both chromosomal instability and DNA instability.
He said this cancer was likely to be more aggressive than the other two, spreading to other parts of the body such as the liver more readily.
Cancers in the chromosomal instability class are initiated by the mutation of a gene known as the APC gene and are associated with the loss of normal genes. This type of cancer is usually a chance event but the mutation can also be inherited. Eighty percent of colon cancers fall into this group.
DNA instability cancers are caused by the defective function of genes (for example, hMSH2 and hMLH1) responsible for correcting errors when DNA replicates itself. In other words, the genes responsible for protecting DNA are themselves mutated.
This results in a growth explosion of cells containing mutations, increasing the likelihood from five to 100 percent that an early growth in the bowel will become cancerous. This type of cancer can also be inherited and affected subjects develop the disease at a young age.
Characterising around 10 percent of colon cancer cases, the types of genes involved in this form of the disease are completely different from those associated with chromosomal instability-caused cancer.
Professor Jass' detailed description of the different behaviours of the three types of colon cancer has generated a classification based upon the underlying mechanisms. However, it is still possible for pathologists to distinguish these types by traditional microscopic examination.
Using a system known as a decision tree, pathologists can decipher the type of cancer present based on particular factors. For example, if lymphocytes have infiltrated the epithelial cells, the type of cancer present falls into the DNA instability class.
Professor Jass said the classification system allowed treatment methods to be tailored to the particular form of colon cancer. For example, the DNA instability form, while less aggressive, may also be less responsive to chemotherapy, he said.
"By knowing exactly what we're dealing with we can perhaps catch the cancer in family members earlier. For example, if we identify the DNA instability cancer, which sometimes arises because of an inherited mutation, we can screen close relatives of the patient for the same cancer," he said.
The research was funded by the Queensland Cancer Fund, the National Health and Medical Research Council and the National Institutes of Health (USA). It was undertaken collaboratively with the Conjoint Gastroenterology Laboratory at the Royal Brisbane Hospital. Based in the Bancroft Centre, the Laboratory is headed by the Medicine Department's Dr Barbara Leggett.
Professor Jass, head of the University's Pathology Department, has been involved in research pinpointing the genetic basis for colon cancer for many years. In 1987, while working at the Imperial Cancer Research Foundation in London, he helped identify the APC gene. Six years later, he was part of a research team which identified the DNA replication error repair gene or MSH2 during genetic linkage studies on cancer-prone, large families in both New Zealand and Canada.
Along with Dr Leggett and Dr Mike Gattas from the Queensland Clinical Genetics Service, Professor Jass is a director of the Queensland Bowel Cancer Family Registry (QBCFR) which aims to foster education, cancer surveillance for prevention and early detection, genetic screening and clinical and basic research.
A joint initiative of the University and the Queensland Cancer Fund, the QBCFR currently has 200 families registered.
For more information, contact Professor Jass (telephone 07 3365 5340).
