Cancer: Scientists reveal how to boost radiotherapy

In In The News by Barbara Jacoby


Scientists have recently identified a molecular pathway that links the movement of energy-producing centers, or mitochondria, in cancer cells to resistance to radiotherapy. This, they say, could lead to improved cancer treatments.

Although previous studies had already revealed that the pathway — called Arf6-AMP1-PRKD2 — plays a key role in cancer invasiveness, its relation to treatment resistance remained unclear.

By studying aggressive breast cancer cells, scientists at Hokkaido University in Japan found that Arf6-AMP1-PRKD2 controls the movement of mitochondria inside the cells.

A recent paper that features in the journal Nature Communications describes their work.

The pathway enables the mitochondria to “disperse” and to move toward the perimeter of the cells, which increases the cancer’s invasiveness.

The team noticed that blocking the pathway caused the energy-generating structures to gather in the center of the cells instead. There, the mitochondria started to produce and release excessive amounts of unstable oxygen-rich molecules known as reactive oxygen species (ROS).

ROS molecules are a double-edged sword in cancer; up to a certain level, they promote cancer invasiveness, but when quantities are excessive, they kill cancer cells.

ROS, mitochondria motion, and integrin

One reason that radiotherapy — which uses ionizing radiation — can shrink or eliminate tumors is because it increases production of ROS inside cancer cells.

Some cancers, however, become resistant to radiotherapy and other treatments that work by increasing ROS in cancer cells because the cells develop a tolerance to the molecules.

The study is not the first to notice that mitochondria move around inside cells. It is known that this motion occurs under various circumstances. When white blood cells, for instance, move toward a target — such as a pathogen or potentially harmful agent — their mitochondria will collect in their rear ends.

In invasive cancer cells, on the other hand, the “powerhouses” congregate in the leading rim of the cell.

A protein called integrin also seems to be involved in cancer invasiveness. The protein normally sits in the cell membrane and helps attach the cell to the matrix of substances that surrounds cells and holds tissues together.

The new study took a deeper look at how ROS, mitochondrial dynamics in cells, and integrin might be connected in invasive cancer.