Currently over 50% of men and women are directed to unnecessary treatment or surgery. A new approach may help. Professor Alan Doucette of Dalhousie University and his colleagues have published a study funded by the Breast Cancer Society of Canada in which they capture particles released by rapidly growing cells called exosomes. Like parcels containing tools and instructions, exosomes contain an “inventory of intent.” Meaning, the cells that have released them contain genetic material proteins and metabolites that promote invasion of normal cells and commandeer their resources.
If absent, the condition may not be referred to cancer at all, but rather labeled as “idle”. In such instances the patient may be monitored rather than immediately directed to therapy to be on the safe side. If therapy was needed, the same information may be used to determine which therapies would be effective rather than a “try and see” approach.
To date, intercepting relevant parcels from suspicious sources has been a challenge: all cells release exosomes for normal bodily functions and they are difficult to sort. However, exosomes released by rapidly growing cells, including all forms of cancer from benign to malignant, are distinctive by being wrapped in protein “ribbons” called chaperones. These ribbons may vary in size and shape on the surface of exosomes from different sources of rapidly growing cells– but they are always present.
Moncton’s Dr. Steve Griffiths with Michelle Cormier (Atlantic Cancer Research Institute, now RCMP Ottawa) developed a type of molecular double-sided sticky tape they call Venceremin peptides that cross-link chaperones and cause the medically important exosomes to settle out from the sea of other similar particles, a process given some help by a quick spin in a laboratory centrifuge. Free of background, the exosomes can be examined more closely, free of dilution and interference.
Dr Aled Clayton, an internationally renowned expert on exosomes at Cardiff Medical School in the U.K., confirmed that Dr. Griffiths idea worked on both laboratory and clinical samples quickly and easily. The captured exosomes are so tightly held in a net-like postage bag formed by peptide cross linkage, that it is possible to rinse the deposits to further wash away interfering materials that interfere with standard laboratory tests. It is simple and only takes an hour.
The approach may provide a substantial boost to existing medical tests troubled by background and poor sensitivity and further empower the age of precision medicine.