Toronto, Sep 28 (IANS): Canadian researchers have discovered how cancer cells become invisible to the body's immune system which may help in developing immune biomarkers that can potentially stop the disease in its tracks.

This 'invisibility' phase is a crucial step that allows tumours to spread throughout the body -- when the spread cannot be traced.

The new mechanism explains how metastatic tumours -- that spread to other parts from its primary site -- can outsmart the immune system.

Reversing this process may help expose these tumours once again to the immune system, the study said.

"The immune system is efficient at identifying and halting the emergence and spread of primary tumours but when metastatic tumours appear, the immune system fails to recognise the cancer cells and stop them," said Professor Wilfred Jefferies from the University of British Columbia, in Canada.

Cancer cells genetically change and evolve over time. The findings showed that as they evolve, they may lose the ability to create a protein known as interleukein-33, or IL-33.

When this IL-33 disappears in the tumour, the body's immune system has no way of recognising the cancer cells and they can begin to spread, or metastasise.

The loss of IL-33 occurs in epithelial carcinomas, meaning cancers that begin in tissues that line the surfaces of organs, including prostate, kidney, breast, lung, uterine, cervical, pancreatic, skin and many others.

The patients with prostate or renal (kidney) cancers whose tumours have lost IL-33, had more rapid recurrence of their cancer over a five-year period.

However, putting IL-33 back into metastatic cancers can help revive the immune system's ability to recognise tumours, the researchers said.

"IL-33 could be among the first immune biomarkers for prostate cancer and, in the near future, we are planning to examine this in a larger sample size of patients," added Iryna Saranchova, a PhD student in the department of microbiology and immunology and first author on the study.

Further research will examine whether this could be an effective cancer treatment in humans, the researchers concluded in the study published in the journal Scientific Reports.