Human immunodeficiency virus-induced apoptosis of human breast cancer cells via CXCR4 is mediated by the viral envelope protein but does not require CD4.
ABSTRACT HIV-1 infection results in an increased risk of malignancy as well as immune suppression. However, analyses of cancer incidence in chronically immunosuppressed transplant recipients and HIV-infected person have demonstrated an unexpected low incidence of certain types of cancer, such as breast cancers, and the mechanism behind this remains unclarified. In this study, we show that most breast cancer cell lines express CXCR4 but are not susceptible to HIV-1 infection. The apoptosis of breast cancer cells is induced by HIV-1 in a viral-dose- and time-dependent manner without productive infection. The apoptosis is induced by R5X4 and X4 HIV-1 but not by R5 HIV-1, and is inhibited by an anti-CXCR4 antibody, an anti-gp120 antibody, AMD3100, or pertussis toxin. The apoptosis is mediated via CXCR4 in breast cancer cells that exhibit conformational heterogeneity in comparison with CXCR4 in T-cells. Furthermore, the gp120 mutant (E370R) with a low CD4 binding ability can specifically induce apoptosis in breast cancer cells but not in T-cells. Taken together, these results indicate that HIV-1 and gp120 can induce breast cancer cell apoptosis through gp120-CXCR4 interaction without a CD4-induced conformational change of gp120, and may lead to a novel HIV-1-based therapy for breast cancer.
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ABSTRACT: During the first two decades of the U.S. AIDS epidemic, and unlike some malignancies, breast cancer risk was significantly lower for women with human immunodeficiency virus (HIV) infection compared to the general population. This deficit in HIV-associated breast cancer could not be attributed to differences in survival, immune deficiency, childbearing or other breast cancer risk factors. HIV infects mononuclear immune cells by binding to the CD4 molecule and to CCR5 or CXCR4 chemokine coreceptors. Neoplastic breast cells commonly express CXCR4 but not CCR5. In vitro, binding HIV envelope protein to CXCR4 has been shown to induce apoptosis of neoplastic breast cells. Based on these observations, we hypothesized that breast cancer risk would be lower among women with CXCR4-tropic HIV infection. We conducted a breast cancer nested case-control study among women who participated in the WIHS and HERS HIV cohort studies with longitudinally collected risk factor data and plasma. Cases were HIV-infected women (mean age 46 years) who had stored plasma collected within 24 months of breast cancer diagnosis and an HIV viral load≥500 copies/mL. Three HIV-infected control women, without breast cancer, were matched to each case based on age and plasma collection date. CXCR4-tropism was determined by a phenotypic tropism assay. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer were estimated by exact conditional logistic regression. Two (9%) of 23 breast cancer cases had CXCR4-tropic HIV, compared to 19 (28%) of 69 matched controls. Breast cancer risk was significantly and independently reduced with CXCR4 tropism (adjusted odds ratio, 0.10, 95% CI 0.002-0.84) and with menopause (adjusted odds ratio, 0.08, 95% CI 0.001-0.83). Adjustment for CD4+ cell count, HIV viral load, and use of antiretroviral therapy did not attenuate the association between infection with CXCR4-tropic HIV and breast cancer. Low breast cancer risk with HIV is specifically linked to CXCR4-using variants of HIV. These variants are thought to exclusively bind to and signal through a receptor that is commonly expressed on hyperplastic and neoplastic breast duct cells. Additional studies are needed to confirm these observations and to understand how CXCR4 might reduce breast cancer risk.PLoS ONE 01/2010; 5(12):e14349. · 4.09 Impact Factor