Breast cancer is the second leading cause of cancer deaths in women today and also the most common cancer among women. Ironically, a new study reveals that the male hormone stimulates growth of breast tumours in women leading to breast cancer. Hauwa Mahmud Kolo writes.
?
According to an American cancer society, about 1.3million women will be diagnosed with breast cancer annually worldwide and about 465, 000 will die from the disease.
However, while this may sound like a case of gender confusion on a molecular scale, the male hormone androgen spurs the growth of some breast tumours in women.
In a new study, scientists at Dana-Farber Cancer Institute provide the first details of the cancer cell machinery that carries out the hormone’s relentless growth orders.
The study, which was published in the journal Cancer Cell, provides scientists with several inviting targets, revealing that cell proteins that snap into action in response to androgen for future therapies and drugs that block those proteins could slow or stifle tumour growth in many breast cancer patients who are not helped by standard hormone-blocking agents, such as tamoxifen.
According to senior author Myles Brown, “We identified a novel subtype of breast tumour, which grows in response to androgen but not oestrogen, and have uncovered the signalling pathways involved in its growth.
And we have demonstrated that drugs capable of blocking these pathways, including the receptor for androgen itself, can inhibit tumour growth. This opens new avenues to the treatment of some women with breast cancer that doesn’t respond to standard endocrine therapies.
“About 70-75 per cent of breast tumours are fuelled by the female hormone oestrogen.
Their cells are loaded with oestrogen receptors (ER), trap-like structures specially shaped to ensnare oestrogen molecules.
When oestrogen becomes lodged in an oestrogen receptor, it sets off a chain of events that prompts the cell to grow and proliferate.
Drugs such as tamoxifen block oestrogen from entering the receptor, thereby thwarting the growth process.
“The remaining 25-30 per cent of breast cancers, dubbed ER-negative tumours, lack oestrogen receptors and thus does not respond to tamoxifen and similar agents.
“Scientists know that the majority of breast tumours, even those with oestrogen receptors, have receptors for androgen, but the reasons for these receptors’ presence, and how they might influence tumour growth, have been unknown.
It might seem odd that some women’s breast cancers carry receptors for a hormone associated with males, but androgen is also involved in the normal development of secondary sexual characteristics in females,” Brown remarks.
Scientists have theorised that androgen propels the growth of breast cancer cells that have receptors for androgen but not for oestrogen.
Using published data on the genomic make-up of breast tumour cells, Brown and his colleagues found a distinctive group accounting for five to 10 per cent of all breast cancer patients that had large numbers of androgen receptors, no ERs, and an oversupply of a protein called HER2.
Cells of this type proliferated rapidly when exposed to androgen.
To understand the mechanism behind this growth, investigators did a mass screening of these tumour cells’ genetic material to see which sections of DNA bind to the androgen receptor, an indication of which genes the receptor directly switches on and off.
By combining these findings with a survey of all the genes active within these cells, the researchers found that the androgen receptor governs two pathways for growth signals.
The pathways, named for important proteins within them (WNT and HER2), play central roles in cell division and proliferation.
When researchers used drugs to handcuff the androgen receptor or the WNT or HER2 proteins in ER-negative breast cancer cells, tumour growth slowed both in laboratory cell cultures and in mice grafted with the cells.
“These findings are strong evidence that therapies that shut down proteins in the WNT or HER2 pathways, or block the androgen receptor itself, can be effective anti-tumour agents for women with this variety of breast cancer.
Combination therapies that target proteins at different points in the pathways are likely to have the greatest success,” Brown says.
According to Dr. Victor Bada, the cause of breast cancer is still yet to be known.? “Breast cancer does not have a definite cause as it is perceived to be hereditary. It is mostly attributed to factors like genetics, family history and it occurs mostly in women within reproductive age.
“However, androgen is a steroid used by some women, especially athletes to make them strong like men.
Recent researches have shown that when the androgen level is too high in a woman, it could stimulate breast cancer, although this is not yet definite, as it is still being researched.
For now, the major sign one should look out for is the presence of any painless lump in the breast.
“Young ladies and women within reproductive age should ensure they have frequent breast examinations. Once any painless lump is noticed, a mammogram should be sought for immediately, so as to detect whether it is cancerous or not,” he says.
?