London: Scientists have discovered in cell cultures, animal models and human tumour tissue that a harmless plant extract can be applied to treat Cushing Disease caused by a tumour.
"Silibinin is the major active constituent of milk thistle seeds. It has an outstanding safety profile in humans and is already used for the treatment of liver disease and poisoning," informed lead researcher Marcelo Paez-Pereda from the Max Planck Institute of Psychiatry in Munich.
Cushing Disease is caused by a tumour in the pituitary gland in the brain.
The tumour secrets increased amounts of the stress hormone adrenocorticotropin (ACTH) followed by cortisol release from the adrenal glands leading to rapid weight gain, elevated blood pressure and muscular weakness.
Patients are prone to osteoporosis, infections and may show cognitive dysfunction or even depression.
After silibinin treatment, tumour cells resumed normal ACTH production, tumour growth slowed down and symptoms of Cushing Disease disappeared in mice.
"We knew that Cushing Disease is caused by the release of too much ACTH. So we asked ourselves what causes this over production and how to stop it," Paez-Pereda said.
In their first experiments the researchers found tremendously high amounts of the heat shock protein 90 (HSP90) in tumour tissue from patients with Cushing Disease.
In normal amounts HSP90 helps to correctly fold another protein, the glucocorticoid receptor which in turn inhibits the production of ACTH.
"With silibinin we might have discovered a non-invasive treatment strategy not only for the rare Cushing Disease but also for other conditions with the involvement of glucocorticoid receptors such as lung tumours, acute lymphoblastic leukaemia or multiple myeloma," Paez-Pereda concluded.
The study was published in Nature Medicine.