No abstract

Compact, glycan-restricted envelope (Env) glycoproteins are selected during heterosexual transmission of subtype C HIV-1. Donor and recipient glycoproteins (Envs) from six transmission pairs were evaluated for entry into HeLa cells expressing different levels of CD4 and CCR5. Donor and recipient Envs demonstrated efficient entry into cells expressing high levels of CD4 and CCR5, and entry declined as CCR5 levels decreased. Infectivity for all Envs was severely impaired in cells expressing low levels of CD4, even at the highest CCR5 levels. In 5/6 pairs, there was no significant difference in efficiency of receptor utilization between the donor and recipient Envs in these HeLa-derived cell lines. Thus, HIV-1 transmission does not appear to select for viruses that can preferentially utilize low levels of entry receptors.

The Nef protein of the human immunodeficiency virus type 1 (HIV-1) has been shown to enhance the infectivity of virus particles, downmodulate cell surface proteins, and associate with many intracellular proteins that are thought to facilitate HIV infection. One of the challenges in defining the molecular events regulated by Nef has been obtaining good expression of Nef protein in T cells. This has been attributed to effects of Nef on cell proliferation and apoptosis. We have designed a Nef protein that is readily expressed in T-cell lines and whose function is inducibly activated. It is composed of a fusion between full-length Nef and the estrogen receptor hormone-binding domain (Nef-ER). The Nef-ER is kept in an inactive state due to steric hindrance, and addition of the membrane-permeable drug 4-hydroxytamoxifen (4-HT), which binds to the ER domain, leads to inducible activation of Nef-ER within cells. We demonstrate that Nef-ER inducibly associates with the 62-kDa Ser/Thr kinase and is localized to specific membrane microdomains (lipid rafts) only after activation. Using this inducible Nef, we also compared the specific requirements for CD4 and HLA-A2 downmodulation in a SupT1 T-cell line. Half-maximal downmodulation of cell surface CD4 required very little active Nef-ER and occurred as early as 4 h after addition of 4-HT. In contrast, 50% downmodulation of HLA-A2 by Nef required 16 to 24 h and about 50-to 100-fold-greater concentrations of 4-HT. These data suggest that HLA-A2 downmodulation may require certain threshold levels of active Nef. The differential timing of CD4 and HLA-A2 downmodulation may have implications for HIV pathogenesis and immune evasion.

Introduction Inflammatory breast cancer (IBC) is an aggressive and rare cancer with a poor prognosis and a need for novel targeted therapeutic strategies. Preclinical IBC data demonstrates strong activation of the PI3K/mTOR and JAK/STAT pathways, expression of inflammatory cytokines and tumor associated macrophages (TAMs). Methods Archival tumor tissue from three disease types (IBC treated with neoadjuvant chemotherapy (NAC) (n=45); invasive ductal carcinoma (IDC) treated with NAC (n=24; ‘treated IDC’); and untreated IDC (n=27; ‘untreated IDC’)) was analyzed for the expression of biomarkers pS6 (mTOR), pJAK2, pSTAT3, IL6, CD68 (monocytes, macrophages) and CD163 (TAMs). Surrounding non-tumor tissue was also analyzed. Results Biomarker levels and surrogate activity by site-specific phosphorylation were demonstrated in the tumor tissue of all three disease types but were highest in IBC and treated IDC and lowest in untreated IDC for pS6, pJAK2, pSTAT3 and IL6. Of 37 IBC patients with complete biomarker data available, 100% were pS6 positive and 95% were pJAK2 positive. In non-tumor tissue, biomarker levels were observed in all groups but were generally highest in untreated IDC and lowest in IBC, except for JAK2. Conclusions IBC and treated IDC display similar levels of mTOR and JAK2 biomarker activation, suggesting a potential mechanism of resistance after NAC. Biomarker levels in surrounding non-tumor tissue suggest that the stroma may be activated by chemotherapy and resembles the oncogenic tumor-promoting environment. Activation of both pS6 and pJAK2 in IBC may support dual targeting of mTOR and JAK/STAT pathways, and the need for prospective studies to investigate combinatorial targeted therapies in IBC.