Why some cancer treatments help some but not others

It's long been a mystery why some colorectal cancer patients respond well to chemotherapy or radiotherapy while others barely respond at all.

Now Dr Laurent Pangon and Dr Maija Kohonen-Corish from the Garvan Institute in Sydney have discovered that the gene MCC plays a role in how patients respond to cancer therapies.

MCC is known as a potential tumour suppressor gene, and is believed to be involved in responding to DNA damage within cells.

If an individual has low expression levels of MCC, their cells have a reduced ability to respond to DNA damage.

Ironically, having a defective MCC gene may make an individual more susceptible to cancer, as they lack one of the safeguards that can prevent DNA damage which can lead to tumours. However, they also respond better to some anti-cancer therapies which damage the DNA of tumour cells.

The researchers found that half their patients had colorectal cancers with a defective MCC gene, and that these patients were more responsive to radiotherapy or some types of chemotherapy.

The finding could lead to new diagnostics and enable more customised treatment for patients with colorectal cancer depending on whether they have a defective gene.

The group has already developed a test that can identify MCC defects in tissue.

Pangon says that the next step is to do a retrospective study of the patient cohort, checking therapy response against the presence of the biomarker in each patient.

“I think this study is important for colon cancer, but even more important for rectal cancer, because rectal cancer has a real disparity when it comes to radiotherapy, which is not well explained. Some patients do really well, and others don’t respond at all,” he said.

“Our study has the potential to provide a scientific explanation as to why some patients respond to treatment better than others and a practical test to identify those patients who are likely to respond.”

The study was published in Genes & Cancer.