Cellular transformation promotes the incorporation of docosahexaenoic acid into the endolysosome-specific lipid bis(monoacylglycerol)phosphate in breast cancer.

Bis(monoacylglycero)phosphates (BMPs), a class of lipids highly enriched within endolysosomal organelles, are key components of the lysosomal intraluminal vesicles responsible for activating sphingolipid catabolic enzymes. While BMPs are understudied relative to other phospholipids, recent reports associate BMP dysregulation with a variety of pathological states including neurodegenerative diseases and lysosomal storage disorders. Since the dramatic lysosomal remodeling characteristic of cellular transformation could impact BMP abundance and function, we employed untargeted lipidomics approaches to identify and quantify BMP species in several in vitro and in vivo models of breast cancer and comparative non-transformed cells and tissues. We observed lower BMP levels within transformed cells relative to normal cells, and consistent enrichment of docosahexaenoic acid (22:6) fatty acyl chain-containing BMP species in both human- and mouse-derived mammary tumorigenesis models. Our functional analysis points to a working model whereby 22:6 BMPs serve as reactive oxygen species scavengers in tumor cells, protecting lysosomes from oxidant-induced lysosomal membrane permeabilization. Our findings suggest that breast tumor cells might divert polyunsaturated fatty acids into BMP lipids as part of an adaptive response to protect their lysosomes from elevated reactive oxygen species levels, and raise the possibility that BMP-mediated lysosomal protection is a tumor-specific vulnerability that may be exploited therapeutically.

The Cationic Amphiphilic Drug Hexamethylene Amiloride Eradicates Bulk Breast Cancer Cells and Therapy-Resistant Subpopulations with Similar Efficiencies.

The resistance of cancer cell subpopulations, including cancer stem cell (CSC) populations, to apoptosis-inducing chemotherapeutic agents is a key barrier to improved outcomes for cancer patients. The cationic amphiphilic drug hexamethylene amiloride (HMA) has been previously demonstrated to efficiently kill bulk breast cancer cells independent of tumor subtype or species but acts poorly toward non-transformed cells derived from multiple tissues. Here, we demonstrate that HMA is similarly cytotoxic toward breast CSC-related subpopulations that are resistant to conventional chemotherapeutic agents, but poorly cytotoxic toward normal mammary stem cells. HMA inhibits the sphere-forming capacity of FACS-sorted human and mouse mammary CSC-related cells in vitro, specifically kills tumor but not normal mammary organoids ex vivo, and inhibits metastatic outgrowth in vivo, consistent with CSC suppression. Moreover, HMA inhibits viability and sphere formation by lung, colon, pancreatic, brain, liver, prostate, and bladder tumor cell lines, suggesting that its effects may be applicable to multiple malignancies. Our observations expose a key vulnerability intrinsic to cancer stem cells and point to novel strategies for the exploitation of cationic amphiphilic drugs in cancer treatment.

Apoptosis induced in HIV-1-exposed, resting CD4+ T cells subsequent to signaling through homing receptors is Fas/Fas ligand-mediated.

The hallmark of HIV-1 disease is the gradual disappearance of CD4+ T cells from the blood. The mechanism of this depletion, however, is still unclear. Evidence suggests that lymphocytes die in lymph nodes, not in blood, and that uninfected bystander cells are the predominant cells dying. Our and others' previous studies showed that the lymph node homing receptor, CD62 ligand (CD62L), and Fas are up-regulated on resting CD4+ T cells after HIV-1 binding and that these cells home to lymph nodes at an enhanced rate. During the homing process, signals are induced through various homing receptors, which in turn, induced many of the cells to undergo apoptosis after they entered the lymph nodes. The purpose of this study was to determine how the homing process induces apoptosis in HIV-1-exposed, resting CD4+ T cells. We found that signaling through CD62L up-regulated FasL. This resulted in apoptosis of only HIV-1-presignaled, resting CD4+ T cells, not normal CD4+ T cells. This homing receptor-induced apoptosis could be blocked by anti-FasL antibodies or soluble Fas, demonstrating that the Fas-FasL interaction caused the apoptotic event.

CD4 lymphocytes in the blood of HIV(+) individuals migrate rapidly to lymph nodes and bone marrow: support for homing theory of CD4 cell depletion.

The mechanism(s) by which human immunodeficiency virus (HIV) causes depletion of CD4 lymphocytes remains unknown. Evidence has been reported for a mechanism involving HIV binding to (and signaling) resting CD4 lymphocytes in lymphoid tissues, resulting in up-regulation of lymph node homing receptors and enhanced homing after these cells enter the blood, and induction of apoptosis in many of these cells during the homing process, caused by secondary signaling through homing receptors. Supportive evidence for this as a major pathogenic mechanism requires demonstration that CD4 lymphocytes in HIV(+) individuals do migrate to lymph nodes at enhanced rates. Studies herein show that freshly isolated CD4 lymphocytes labeled with (111)Indium and intravenously reinfused back into HIV(+) human donors do home to peripheral lymph nodes at rates two times faster than normal. They also home at enhanced rates to iliac and vertebral bone marrow. In contrast, two hepatitis B virus-infected subjects displayed less than normal rates of blood CD4 lymphocyte migration to peripheral lymph nodes and bone marrow. Furthermore, the increased CD4 lymphocyte homing rates in HIV(+) subjects returned to normal levels after effective, highly active antiretroviral therapy treatment, showing that the enhanced homing correlated with active HIV replication. This is the first direct demonstration of where and how fast CD4 lymphocytes in the blood traffic to tissues in normal and HIV-infected humans. The results support the theory that the disappearance of CD4 lymphocytes from the blood of HIV(+) patients is a result of their enhanced migration out of the blood (homing) and dying in extravascular tissues.

Detection of antibodies to human immunodeficiency virus (HIV) that recognize conformational epitopes of glycoproteins 160 and 41 often allows for early diagnosis of HIV infection.

On the basis of human immunodeficiency virus (HIV) needlestick studies, the time to seroconversion for anti-HIV antibodies is 1-9 months (mean, approximately 2-3 months). However, an earlier marker of an immune response to HIV often occurs-serum anti-HIV antibodies reactive with live HIV-infected cells, termed "early HIV antibodies." The specificities of these antibodies are characterized by the recognition of type-specific conformational epitopes of the HIV envelope glycoprotein (gp) 160 and gp41. By use of a third-generation native HIV(IIIB) gp160 enzyme immunoassay (EIA), detection of HIV antibodies occurred, on average, 33 days earlier than did detection by commercial EIA and 25 days earlier than did detection by the reference antigen and reverse-transcription polymerase chain reaction (RT-PCR) assays in 3 of 5 HIV seroconversion panels. A fourth panel possessed early HIV antibodies that reacted with HIV(213) but not with HIV(IIIB), allowing for detection of HIV antibodies approximately 3 weeks earlier than by RT-PCR or other current tests.