​New York, March 2 (IANS) Researchers have found a way to activate the immune system's natural cancer-killing T-cells and cause tumours to shrink in mice with colon cancer.

The intervention essentially trains the immune system to recognise and attack the tumour, and to protect against additional tumour formation - a significant issue in colon cancer, said corresponding author Ajay Maker, Associate Professor at University of Illinois College of Medicine in Chicago, US.

In the study, published in the journal Cancer Research, the researchers reported that increasing expression of a chemical cytokine called LIGHT in mice with colon cancer activated the immune system's natural cancer-killing T-cells and caused primary tumours in the liver to shrink.

LIGHT is an immune-stimulating chemical messenger previously found to have low levels of expression in patients with colon cancer metastases.

"For most patients with colon cancer that has spread to the liver, current treatments are palliative and not curative," Maker said.

"And while studies have suggested that immunotherapy may be a promising approach for advanced cancers, the use of such treatments for advanced gastrointestinal metastases have not yet been very successful," Maker said.

This study is exciting because it looks at an immunotherapy intervention for a previously unresponsive gastrointestinal cancer, Maker said.

For the study, the researchers established colon cancer tumors in a mouse model, in which the animals had an intact and unedited immune system. 

Once tumours were sizable, the mice were randomised into two groups - one group had the cytokine LIGHT turned on in the tumours, and the other served as a control group for comparison.

Tumours exposed to LIGHT showed an influx of T-cells that resulted in rapid and sustained diminishment in size, even after expression of the cytokine stopped. 

In cases where the tumour spread to liver, expression of LIGHT similarly provoked a potent immune response that resulted in a significant decrease in tumour burden.

"We demonstrated that delivery of a therapeutic immune-stimulating cytokine caused T-cells to traffic to tumours and to become activated tumor-killing cells," Maker said.