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When two normally occurring hormones are brew together, the effects on women could turn dangerous, scientists have discovered.
When the hormones insulin and estrogen interact, the result is the growth and proliferation of breast cancer cells. Women with diabetes are more likely to get breast cancer, and women with breast cancer are more likely to get diabetes.
What Dr. Victoria Knutson found in her initial lab experiments is that "when breast cancer cells are bathed in estrogen, as occurs in pre-menopausal women, the cells are more sensitive to insulin, which stimulates growth."
Knutson is associate professor in the Department of Integrative Biology and Pharmacology at The University of Texas Medical School at Houston.
"We now know that there is interaction between estrogen and insulin signaling," she says. From her research, the insulin is not causing breast cancer, but it encourages growth in already existing cancer cells.
In the lab, Knutson says, breast cancer cells treated with insulin alone have no impact on the growth of the cells. When breast cancer cells are treated with estrogen, it induces growth. "However, if we add both together, there is a synergy, and we have amplified growth. That amplification increases with higher concentrations of insulin. More insulin is worse," she says and adds, "the impact then for a diabetic woman is horrible."
In a woman who does not have diabetes, the insulin level rises each time she eats and within two hours goes back down. If there is a snack, it shoots up and down quickly. But, with the diabetic, that insulin level goes up and stays there.
If the woman is pre-menopausal, estrogen is also present. Consequently, estrogen in the presence of steadily elevated insulin has an impact on breast cancer growth.
In the 1970s Knutson says, there were studies that demonstrated that diabetic women had a two-to three-fold higher risk for getting breast cancer. "Finding one factor with such a risk is significant."
Breast cancer growth is a complicated puzzle. Knutson is studying one of the pieces, a molecule called LAR, which deactivates the insulin receptor.
LAR has been implicated in diabetes because it helps to turn off the insulin signal. "Although we don't know why, LAR also has been linked to breast cancer that has metastasized or spread to distant sites in the body," she explains.
"We were looking at breast cancer in diabetics, and there was LAR again. It is important because breast cancer cells treated with estrogen decreased the expression of the LAR molecule. This means that the insulin receptor is super active and helps promote the growth of the cancer, even in the absence of insulin. So just by treating the cells with estrogen, we turned on the insulin pathway."
One big question Knutson has is LAR's function in metastasis—the spread of cancer to other parts of the body. Knutson plans to work with the UT M. D. Anderson Cancer Center to study tissue taken from women with breast cancer, both pre-metastatic and metastatic (both localized and spreading breast cancer) tissue.
"There are tests to identify a person in a pre-diabetic state. We already know that a woman with gestational (while pregnant) diabetes is at risk for developing the disease when she is older. Both African-Americans and Hispanics have a predisposition for diabetes," Knutson says. "Except for family history, there is no good predictor for breast cancer. So, if a woman has a family history of both diabetes and breast cancer, that should put her on notice."
By looking at the level and location of LAR she hopes to understand the role of the molecule and if it could be used as a predictor or risk factor for metastatic breast cancer, especially in women who are at risk for diabetes.
Knutson fervently believes that a diabetic woman should be vigilant about being tested for breast cancer or at least have the recommended mammograms for her particular age.
UPDATED: 1-11-2005
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Dr. Victoria Knutson is an associate professor in the Department of Integrative Biology and Pharmacology at the UT Medical School.
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Tetanus booster for adults
Tetanus does not result from the rusty nail or whatever created the wound. The danger lies in the bacteria Clostridium tetani that lives in the soil or manure on that nail or gardening tool. When these spores get into a wound—deep or shallow—they can produce a potent toxin. Also called lockjaw, tetanus seriously affects the central nervous system and can be fatal.
Onset of symptoms can occur anytime from three days to three weeks. Call your health care provider if you have an open wound, particularly if:
Adults should have a tetanus booster shot every 10 years, known as the Td vaccine. It is a "2-in-1" vaccine that protects against tetanus and diphtheria. It contains a slightly different dose of diphtheria vaccine than what you received as a child. It can be given to anyone older than 7 years and is injected, usually into the arm.
Instead of the standard Td booster every 10 years, adults between the ages of 19 and 65 should receive Tdap one time in their adulthood to boost the immune system for pertussis, as well as tetanus and diphtheria.
Diphtheria, a contagious bacterial infection created that causes severe inflammation of the throat and larynx and can also affect the whole body. Pertussis or “whooping cough” is a serious bacterial infection that afflicted children and infants before vaccines were available. Adults may be infected later in life as their immunities wane. Neither of these infections are related to tetanus, but both vaccines are compatible and convenient to use with the tetanus booster.
