Scientists have identified a molecule that can help treat breast cancer, giving hope to millions of patients who have become resistant to traditional therapies.
According to researchers, the molecule is a first-in-class drug which shuts down oestrogen-sensitive breast cancer by a unique mechanism—a molecule that targets a protein on the oestrogen receptor of tumour cells. The new molecule, named ERX-11, mimics a peptide, or protein building block.
"This is a fundamentally different, new class of agents for oestrogen-receptor-positive breast cancer. Its unique mechanism of action overcomes the limitations of current therapies ," said Ganesh Raj, professor at the University of Texas Southwestern (UT Southwestern) Simmons Cancer Centre.
According to experts, all breast cancers are tested to determine if they require oestrogen to grow, and about 80 per cent are found to be oestrogen-sensitive. These cancers can often be effectively treated with hormone therapy—such as tamoxifen—but as many as a third of these cancers eventually become resistant. The new compound is a potential highly effective, next-line treatment for these patients.
Dilip Nikam, professor and head, Radiotherapy and Oncology Departments, Grant Medical College & J. J. Hospital, Mumbai, said the identification of this molecule is "revolutionary in the area of breast cancer treatment,” while insisting that it may just be a matter of months when it is introduced to the market for application. "Essentially, breast cancer develops mainly due to hormonal changes, that is, changes in the levels of oestrogen and progesterone. All breast cancer treatments are surgery, chemotherapy, radiotherapy and hormonal therapy. This molecule assists in the fourth way of treatment, that is, hormonal therapy,” said Nikam.
"If a certain patient is ER positive, that is, in response to estrogen or PR positive, that is, in response to progesterone, then we put them on hormonal treatment. This can go up to ten years, and the minimum is five years. This long timeline leads to drug resistance in the body, and to counter that resistance this drug is developed. Now 60-70 per cent population is positive for ER/TR and this is why it is a welcome step in the field of medicine," he said.
Traditional hormonal drugs like tamoxifen work by attaching to a molecule called the oestrogen receptor in cancer cells, preventing oestrogen from binding to the receptor—a necessary step for cancer cells to multiply. However, the oestrogen receptor can mutate and change its shape over time so that the treatment drug no longer fits neatly with the receptor. When this happens, the cancer cells start multiplying again.
"There has been intense interest in developing drugs that block the ability of the oestrogen receptor— the prime target in most breast cancers—from interacting with the co-regulator proteins that cause a tumor's growth, blocking such "protein-protein interactions," said David Mangelsdorf, professor at UT Southwestern. The drug works by blocking other molecules—proteins called co-factors—that also must attach to the oestrogen receptor for cancer cells to multiply.