Study Finds That A Certain Type Of HIV Reduces Breast Cancer Risk Among HIV-Infected Women

By Meerat Oza and Courtney McQueen
Published: Jan 4, 2011 5:03 pm

Results of a recently published study have shown that women infected with a certain type of HIV may have a significantly lower risk of breast cancer compared to women with other strains of HIV, possibly because this type of HIV effectively targets and kills breast cancer cells.

The study authors stated that the results need to be confirmed by additional studies, but may explain results showing women with HIV are at lower risk for breast cancer than women without HIV.

HIV is often associated with increased rates of several types of malignant cancers, such as Kaposi’s sarcoma, non-Hodgkin’s lymphoma, Hodgkin’s lymphoma, cervical cancer, and anal cancer.

However, studies have shown that women with HIV may be at decreased risk of breast cancer. Between 1980 and 2002, the risk of breast cancer was found to be 31 percent lower in HIV-infected women as compared to uninfected women.

Researchers have speculated that this may be because a type of cell protein that HIV sometimes uses to infect immune system cells is also found on the surface of breast cancer cells.

In order to infect healthy white blood cells, HIV binds to certain proteins on their surface, called CCR5 or CXCR4. Most HIV, especially early in infection, uses CCR5 for infection. However, later in infection HIV will sometimes switch to using CXCR4 or a combination of the two proteins.

One hypothesis for why HIV-positive women may be at reduced risk for breast cancer is that the CXCR4 protein is also found on the surface of breast cancer cells. This protein is not found on normal breast cells and may be used by the cancer cells to grow and spread. Scientists have shown that in the laboratory, HIV that binds to breast cancer cells kills them.

If this hypothesis is correct, then women with HIV that uses the protein CXCR4 for infection should be at lower risk of developing breast cancer.

To test their hypothesis, the researchers in this study identified 23 HIV-infected women who had breast cancer and compared them to 69 HIV-positive women without breast cancer who were of similar age.

Results showed that only 9 percent of the women with breast cancer had CXCR4-dependent HIV, compared to 28 percent of the women without breast cancer.

Further analysis revealed that women with CXCR4-dependent HIV were only 10 percent as likely to have breast cancer as women infected with CCR5-dependent HIV.

Menopause was the only other factor that affected the risk of developing breast cancer. CD4 (white blood cell) count, viral load (amount of HIV in the blood), antiretroviral therapy regimen, ethnicity, and other lifestyle factors such as use of alcohol or contraceptives did not correlate with risk.

The researchers concluded that CXCR4-dependent HIV has a protective effect against breast cancer in women, and they speculated that CXCR4-dependent HIV may account for the lower risk of breast cancer in women with HIV.

They suggested that their findings could lead to new methods for trying to combat breast cancer.

Since the study was small, the researchers noted that their results will need to be confirmed by further studies with larger groups of women.

Also, while they presume the lower risk of breast cancer arises from CXCR4-dependent HIV infecting and killing breast cancer cells, they suggested further study on the exact mechanism by which CXCR4-dependent HIV protects against breast cancer.

For more information, please see the study in PLoS One.

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