Scientists find answers why cancer cells resist chemotherapy

London: Scientists have made a breakthrough in understanding why some cancer cells become resistant to chemotherapy by identifying a modification to proteins that wrap around the DNA of cancer cells, a report today said.

Researchers at UK's University of Sheffield identified the specific modification to proteins that wrap around the DNA of cancer cells, protecting them from chemotherapy treatment.

Most types of chemotherapy and radiotherapy kill cancer cells by causing many breaks in the DNA ? the blueprint that carries the information needed to make proteins, and for cells to survive. Unfortunately, cancer cells fight back by trying to fix the breaks through a toolkit of specialised armies, giving cancer resistance to therapy.

However, a team from the Krebs Institute for Nucleic Acids at the university found that the key to preventing resistance to a common class of chemotherapy used to treat breast and colon cancer is to change the speed in which the cancer cells repair damage to their DNA that is introduced by chemotherapy.

Professor Sherif El-Khamisy, who led the research, said: "If we can find a way to hijack the cancer's fix and repair toolkit and make it less efficient, then we can tip the scale in favour of cancer cell death instead of survival and prevent resistance to chemotherapy.

"We have discovered that resistance to a common class of chemotherapy, used to treat colon and breast cancer, is caused by changes in the speed by which the tool kit components travel to, and stay at, the sites of DNA breaks.

"Our researchers were able to identify a change in a specific mark in the proteins that wrap the DNA ? called histones ? in such a way that makes repair much faster in cancer cells, increasing their resistance to therapy."

El-Khamisy, a Wellcome Trust Investigator and Director of Research and Innovation at the university's Department of Molecular Biology and Biotechnology, has been working on the research for four years.

"The change we identified is not genetic ? but epigenetic," said El-Khamisy.

"This means that the histone mark proteins are like the directors in a film. The script of the film stays the same but the director - the histone mark - can choose to eliminate, slow down or speed up certain scenes or dialogues, altering the film for better ? cancer cell death - or worse cancer cell survival."

He added: "The team were able to inhibit the activity of the enzyme that controls the 'scene' ensuring that the film always has a happy ending ? reversing the resistance of cancer cells.

"This means that patients who develop resistance to certain classes of chemotherapy can benefit from drugs that modulate histone marks such as histone deacetylase inhibitors, some of which are already approved by the Food and Drug Administration."

The findings were published in the journal Nucleic Acids Research.