Laboratory engineered "designer" proteins may offer a way to prevent treatable prostate cancer advancing to a deadly stage.
In tests, the molecules overcame two mechanisms by which prostate cancer develops resistance to conventional hormone therapies.
Scientists hope the early research will ultimately lead to treatments that stop tumours progressing to the "castrate resistant" stage after which little can be done for patients.
The proteins, made from amino acids, block the cancer-fuelling effect of male androgen hormones, such as testosterone, while stopping resistance setting in.
Lead researcher Dr Charlotte Bevan, from the Department of Surgery and Cancer at Imperial College London, said: "Eleven thousand men die from prostate cancer each year in the UK. Existing treatments are good at first, but frequently fail after a couple of years. Once the cancer moves to the more aggressive stage, there are few therapies available."
"Our team is seeking to design a new therapy that will help patients once the other ones have failed. There is a lot of research supporting the idea that the androgen receptor continues to drive prostate cancer growth, so we have been investigating novel methods to block this pathway."
Androgens help prostate cancer to grow by latching onto a specific receptor molecule on tumour cells.
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Hormone therapies either block the receptor, or cut off the supply of testosterone by a form of chemical castration.
But after an average of two years of hormone treatment, the receptor adjusts itself to by-pass the effects of the drugs.
One resistance mechanism is a "co-regulator" pathway that sensitises the tumour even to very weak androgenic signals.
Another involves mutations that allow the cancer to be driven by other triggers, including oestrogen and even some hormone treatments.
In the tests, the experimental proteins counteracted both these effects so that cancers continued to respond to treatment.
The new research is published in the journal Oncotarget.
The team is designing a novel therapy combing two separate proteins, one of which binds to the tumour receptor while the other blocks its activity.
Co-author Dr Greg Brooke, from the University of Essex, said: "So far, the research has only been carried out in prostate cancer cells in the laboratory.
"These proof of principle experiments are really promising, but more work is needed before these therapies are ready for clinical trials.
"The next step is to continue research in cell models to refine the therapy into something that is specific, potent and easy to deliver."
Each year, around 37,000 men in the UK develop prostate cancer.