New clues have surfaced on how leptin, a hormone found in fat cells, may play a major role in the development and progression of breast cancer.

Italian researchers have identified a new mechanism that helps explain how obesity boosts risk of breast cancer, a discovery that may lead to new drugs to specifically combat the problem.

Research team leader Dr. Sebastiano Ando notes that obesity increases the risk of breast cancer in postmenopausal women, shortens the time between cancer recurrence, and lowers overall survival rates. His team finds that leptin increases the amount of estradiol (a type of estrogen) in breast tissue.

Hormone Feeds Tumors

Ando's research team finds that combined exposure to leptin and estradiol increases the size of breast cancer tumors in both mice and in tissue cultures. This growth in tumor size was accompanied by an increase in E-cadherin, an intracellular adhesion molecule generally regarded as a tumor suppressor.

But the new twist is that E-cadherin may act as a tumor enhancer when it's exposed to leptin and estradiol. In that case, E-cadherin's ability to draw cells together enhances the transformation of normal cells to cancerous cells, thus stimulating tumor growth.

Ando and his colleagues say that this increased cell growth can be halted when an Ecadherin antibody or a calcium-chelating agent is used to block E-cadherin function in the presence of estradiol.

It's the first step in what may lead to new drugs.

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