Treatment with the HIV protease inhibitor Nelfinavir triggers the unfolded protein response and may overcome proteasome inhibitor resistance of multiple myeloma in combination with bortezomib: a phase I trial (SAKK 65/08).

Downregulation of the unfolded protein response mediates proteasome inhibitor resistance in Multiple Myeloma.The Human Immunodeficieny Virus protease inhibitor nelfinavir activates the unfolded protein response in vitro. We determined dose limiting toxicity and recommended dose for phase II of nelfinavir in combination with the proteasome inhibitor bortezomib. 12 patients with advanced hematological malignancies were treated with nelfinavir (2500 - 5000 mg/d p.o., d 1-14, 3+3 dose escalation) and bortezomib (1.3 mg/m2, d 1, 4, 8, 11; 21 day cycles). A run in phase with nelfinavir monotherapy allowed pharmakokinetic/pharmakodynamic assessment of nelfinavir in the presence or absence of concomittant bortezomib. Endpoints included dose limiting toxicity, activation of the unfolded protein response, proteasome activity, toxicity and response to trial treatment. Nelfinavir 2 x 2500 mg was the recommended phase II dose identified. Nelfinavir alone significantly upregulated expression of proteins related to the unfolded protein response in peripheral blood mononuclear cells and inhibited proteasome activity. Of 10 evaluable patients in the dose escalation cohort, 3 achieved a partial response, 4 stable disease for ≥ 2 cycles, while 3 had progressive disease as best response. In an exploratory extension cohort with 6 relapsed, bortezomib-refractory, lenalidomide-resistant myeloma patients treated at the recommended phase II dose, 3 reached a partial response, 2 a minor response and one progressive disease. The combination of nelfinavir with bortezomib is safe and shows promising signals for activity in advanced, bortezomib-refractory MM. Induction of the unfolded protein response by nelfinavir may overcome the biological features of proteasome inhibitor resistance. (Trial registration NCT01164709).

Expression and biological activities of bovine interleukin 4: effects of recombinant bovine interleukin 4 on T cell proliferation and B cell differentiation and proliferation in vitro

Interleukin 4 (IL-4) is a pleotropic cytokine affecting a wide range of cell types in both the mouse and the human. These activities include regulation of the growth and differentiation of both T and B lymphocytes. The activities of IL-4 in nonprimate, nonmurine systems are not well established. Herein, we demonstrate in the bovine system that IL-4 upregulates production of IgM, IgG1, and IgE in the presence of a variety of costimulators including anti-IgM, Staphylococcus aureus cowan strain I, and pokeweed mitogen. IgE responses are potentiated by the addition of IL-2 to IL-4. Culture of bovine B lymphocytes with IL-4 in the absence of additional costimulators resulted in the increased surface expression of CD23 (low-affinity Fc epsilon RII), IgM, IL-2R, and MHC class II in a dose-dependent manner. IL-4 alone increased basal levels of proliferation of bulk peripheral blood mononuclear cells but in the presence of Con A inhibited proliferation. In contrast to the activities of IL-4 in the murine system, proliferation of TH1- and TH2-like clones was inhibited in a dose-dependent manner as assessed by antigen-or IL-2-driven in vitro proliferative responses. These observations are consistent with the role of IL-4 as a key player in regulation of both T and B cell responses.

Expression of interleukin 4, interleukin 4 splice variants and interferon gamma mRNA in calves experimentally infected with Fasciola hepatica

Interleukin 4 (IL-4) is expected to play a dominant role in the development of T helper (Th) 2 cells. Th2 immune responses with expression of relatively large amounts of interleukin 4 (IL-4) but little interferon gamma (IFN-gamma) are characteristic for chronic helminth infections. But no information is available about IL4 expression during early Fasciola hepatica (F. hepatica) infections in cattle. Therefore, we investigated F. hepatica specific IL-4 and IFN-gamma mRNA expression in peripheral blood mononuclear cells (PBMCs) from calves experimentally infected with F. hepatica. Cells were collected prior to infection and on post-inoculation days (PIDs) 10, 28 and 70. Interestingly, PBMCs responded to stimulation with F. hepatica secretory-excretory products (FhSEP) already on PID 10 and expressed high amounts of IL-4 but not of IFN-gamma mRNA suggesting that F. hepatica induced a Th2 biased early immune response which was not restricted to the site of infection. Later in infection IL-4 mRNA expression decreased whereas IFN-gamma mRNA expression increased slightly. Isolated lymph node cells (LNCs) stimulated with FhSEP and, even more importantly, non-stimulated LN tissue samples indicated highly polarized Th2 type immune responses in the draining (hepatic) lymph node, but not in the retropharyngeal lymph node. During preliminary experiments, two splice variants of bovine IL-4 mRNA, boIL-4delta2 and boIL-4delta3, were detected. Since a human IL-4delta2 was assumed to act as competitive inhibitor of IL-4, it was important to know whether expression of these splice variants of bovine IL-4 have a regulatory function during an immune response to infection with F. hepatica. Indeed, IL-4 splice variants could be detected in a number of samples, but quantitative analysis did not yield any clue to their function. Therefore, the significance of bovine IL-4 splice variants remains to be determined.

IN VITRO INDUCTION OF XENOIMMUNE RESPONSES TO LIPOSOMES CONTAINING HUMAN COLON TUMOR ANTIGENS

Liposomes prepared with human LS174T colon tumor cell membranes induce specific primary and secondary xenogeneic immune responses in BALB/c splenocytes in vitro. The multilamellar vesicular liposomes were prepared by adding sonicated membrane fragments in 8 mM CaCl(,2) to a dried lipid film. Cytoxic splenocytes generated in vivo exhibited specificity for the LS174T cell; liposomes elicited higher levels of cytotoxicity than did membranes (P < 0.01). Secondary blastogenic responses elicited in in vivo-primed spleen cells by liposomes also produced a significantly greater (P < 0.005) response than membranes. Subsequently, in vitro induction of primary blastogenic and cytotoxic responses by liposomes were accomplished and revealed similar kinetics to that of whole LS174T cell immunogens. Specificity of the in vitro-primed spleen cells was clearly demonstrated (P < 0.01) on a variety of human tumor cells using both the primed lymphocyte and cell-mediated cytotoxicity assays. The results of competitive inhibition tests with autologous lymphoblasts demonstrated that 30% of the cytotoxic activity was directed against lymphocyte antigens.^ The adjuvant effect of liposomes was shown to be mediated primarily by tumor antigens exposed on the outer surface of liposomes. Trypsinization of the liposomes which eliminated 96% of the surface protein reduced the ability of liposomes to induce cytotoxic splenocytes. The generation of cytolytic activity with liposomes of increasing protein concentration showed that while 10 (mu)g protein was threshold, 100 (mu)g protein induced maximal responses. In addition, membrane fluidity studies revealed that rigid liposomes were significantly (P < 0.05) more efficacious than fluid liposomes in inducing cytotoxicity.^ The induction of the primary response required the presence of nonadherent splenocytes bearing the Thy-1, Lyt-1, and Lyt-2 surface markers. The role of a Lyt-123 subpopulation was suggested by the inability of both the Lyt-1 and Lyt-2 depleted populations to completely restore the cytolytic levels to normal. In addition, the interaction of I-A('+) spleen adherent cells with liposomes for at least 8 hours was required to generate maximal cytotoxic activity. The phenotype of the cytotoxic effector was Thy-1('+), Lyt-2('+), and I-A('d-).^ Incorporation of tumor antigens into liposomes has thus enabled primary immunization in vitro to human colon cancer antigens and may afford an adaptable means to evaluate and to select specific immune responses, as well as to identify colon tumor-specific determinants.^

ANTIBODY-DEPENDENT AND ANTIBODY-INDEPENDENT CELLULAR CYTOTOXICITY AGAINST SHIGELLA

Diarrhea is a major cause of morbidity and mortality worldwide. Shigella causes up to 20% of all diarrhea. Gut-level immunity and breast-feeding of infants are important factors in protection against shigellosis. The lumen of the gut is lined with lymphocytes which mediate natural killer cytotoxicity, NKC, and antibody-dependent cellular cytotoxicity, ADCC. NKC and ADCC are extracellular, nonphagocytic leukocyte killing mechanisms, which occur in the absence of complement, without prior antigen stimulation, and without regard to the major histocompatibility complex. In this study, virulent and avirulent shigellae were used as the target cells. Leukocytes from peripheral blood, breast milk, and guinea pig gut-associated tissues were used as effector cells. Adult human peripheral blood mononuclear cells and lymphocytes, but not macrophages or polymorphonuclear leukocytes, mediated NKC and ADCC at an optimal effector to target cell ratio of 100:1 in a 60 minute bactericidal assay. An antiserum dilution of 1:10 was optimal for ADCC. Whole, viable lymphocytes were necessary for cytotoxicity. Lymphocyte NKC, but not ADCC, was greatly enhanced by interferon. Lymphocyte NKC occurred against several virulent strains of S. sonnei and a virulent strain of S. flexneri. ADCC (using immune serum directed against S. sonnei) occurred against virulent S. sonnei, but not against avirulent S. sonnei or virulent S. flexneri. Lymphocyte ADCC was not inhibited by the presence of phenylbutazone or by pretreatment of lymphocytes with anti-HNK serum plus complement. Both adherent and non-adherent breast milk leukocytes mediated NKC and ADCC. Mononuclear cells from young children demonstrated normal ADCC, when compared to ADCC of adult cells. Neonatal cord blood and a CGD patient's peripheral blood mononuclear and ploymorphonuclear cells demonstrated high ADCC compared to adult cells. Intraepithelial lymphocytes, spleen cells, and peritoneal cells from normal guinea pigs demonstrated NKC and ADCC. Animals which had been starved and opiated were made susceptible to infection by Shigella. The susceptible animals demonstrated deficient NKC and ADCC with all three leukocyte populations. High NKC and ADCC activity of gut-associated leukocytes from human breast milk and guinea pig tissues may correlate with resistance to infection. ^

The role of MAPK during the activation of NK cells

Although many clinical trials investigated the use of IL-2, IL-12, and LAK in adoptive immunotherapy to treat cancer, only limited clinical success has been achieved. Better understanding of the intracellular processes that IL-2 and IL-12 utilize to generate LAK and other functions in NK cells is necessary to improve this mode of therapy. IL-2 and IL-12 stimulate extracellular signal-regulated protein kinase (ERK) and p38 MAPK in mitogen-activated T lymphocytes. The functional roles that these kinases play are still unclear. In this study, we examined whether MAPK Kinase (MKK)/ERK and/or p38 MAPK pathways are necessary for IL-2 or IL-12 to activate NK cells. We established that IL-2 activates MKK1/2/ERK pathway in freshly isolated human NK cells without any prior stimulation. Furthermore, we determined that an intact MKK/ERK pathway is necessary for IL-2 to activate NK cells to express at least four known biological responses: LAK activity, IFN-γ secretion, and CD25 and CD69 expression. Treatment of NK cells with a specific inhibitor of MKK1/2 PD98059, during the IL-2 stimulation blocked in a dose-dependent manner each of four activation parameters. Although activation of ERK was not detected in NK cells immediately after IL-12 stimulation, IL-12-induced functional activation was inhibited by the MKK1/2 inhibitor, as well. In contrast to what was observed by others in T lymphocytes, activation of p38 MAPK by IL-2 was not detected in NK cells. Additionally, a specific inhibitor of p38 MAPK (SB203850) did not inhibit IL-2-activated NK functions. These data reveal selective signaling differences between NK cells and T lymphocytes. Collectively, the data support that the MKK/ERK pathway plays a critical positive regulatory role in NK cells during activation by IL-2 and IL-12. ^

The utility of N5 for gene therapy of human cancer

Cancer is a result of defects in the coordination of cell proliferation and programmed cell death. The extent of cell death is physiologically controlled by the activation of a programmed suicide pathway that results in a morphologically recognizable form of death termed apoptosis. Inducing apoptosis in tumor cells by gene therapy provides a potentially effective means to treat human cancers. The p84N5 is a novel nuclear death domain containing protein that has been shown to bind an amino terminal domain of retinoblastoma tumor suppressor gene product (pRb). Expression of N5 can induce apoptosis that is dependent upon its intact death domain and is inhibited by pRb. In many human cancer cells the functions of pRb are either lost through gene mutation or inactivated by different mechanisms. N5 based gene therapy may induce cell death preferentially in tumor cells relative to normal cells. We have demonstrated that N5 gene therapy is less toxic to normal cells than to tumor cells. To test the possibility that N5 could be used in gene therapy of cancer, we have generated a recombinant adenovirus engineered to express N5 and test the effects of viral infection on growth and tumorigenicity of human cancer cells. Adenovirus N5 infection significantly reduced the proliferation and tumorigenicity of breast, ovarian, and osteosarcoma tumor cell lines. Reduced proliferation and tumorigenicity were mediated by an induction of apoptosis as indicated by DNA fragmentation in infected cells. We also test the potential utility of N5 for gene therapy of pancreatic carcinoma that typically respond poorly to conventional treatment. Adenoviral mediated N5 gene transfer inhibits the growth of pancreatic cancer cell lines in vitro. N5 gene transfer also reduces the growth and metastasis of human pancreatic adenocarcinoma in subcutaneous and orthotopic mouse model. Interestingly, the pancreatic adenocarcinoma cells are more sensitive to N5 than they are to p53, suggesting that N5 gene therapy may be effective in tumors resistant to p53. We also test the possibilities of the use of N5 and p53 together on the inhibition of pancreatic cancer cell growth in vitro and vivo. Simultaneous use of N5 and RbΔCDK has been found to exert a greater extent on the inhibition of pancreatic cancer cell growth in vitro and in vivo. ^

Loss of activator protein-2alpha results in overexpression of the thrombin receptor and correlates with the malignant phenotype of human melanoma

Increasing evidence demonstrates that the thrombin receptor (protease activated receptor-1, PAR-1) plays a major role in tumor invasion and contributes to the metastatic phenotype of human melanoma. We demonstrate that the metastatic potential of human melanoma cells correlates with overexpression of PAR-1. The promoter of the PAR-1 gene contains multiple putative AP-2 and Sp1 consensus elements. We provide evidence that an inverse correlation exists between the expression of AP-2 and the expression of PAR-1 in human melanoma cells. Re-expression of AP-2 in WM266-4 melanoma cells (AP-2 negative) resulted in decreased mRNA and protein expression of PAR-1 and significantly reduced the tumor potential in nude mice. ChIP analysis of the PAR-1 promoter regions bp −365 to −329 (complex 1) and bp −206 to −180 (complex 2) demonstrates that in metastatic cells Sp1 is predominantly binding to the PAR-1 promoter, while in nonmetastatic cells AP-2 is bound. In vitro analysis of complex 1 demonstrates that AP-2 and Sp1 bind to this region in a mutually exclusive manner. Transfection experiments with full-length and progressive deletions of the PAR-1 promoter luciferase constructs demonstrated that metastatic cells had increased promoter activity compared to low and nonmetastatic melanoma cells. Our data shows that exogenous AP-2 expression decreased promoter activity, while transient expression of Sp1 further activated expression of the reporter gene. Mutational analysis of complex 1 within PAR-1 luciferase constructs further demonstrates that the regulation of PAR-1 is mediated through interactions with AP-2 and Sp1. Moreover, loss of AP-2 in metastatic cells alters the AP-2 to Sp1 ratio and DNA-binding activity resulting in overexpression of PAR-1. In addition, we evaluated the expression of AP-2 and PAR-1 utilizing a tissue microarray of 93 melanocytic lesions spanning from benign nevi to melanoma metastasis. We report loss of AP-2 expression in malignant tumors compared to benign tissue while PAR-1 was expressed more often in metastatic melanoma cells than in benign melanocytes. We propose that loss of AP-2 results in increased expression of PAR-1, which in turn results in upregulation of gene products that contribute to the metastatic phenotype of melanoma. ^

Activation of dendritic cells from patients with epithelial ovarian cancer

Dendritic cells (DCs) are the most potent antigen-presenting cells for inducing immune responses to tumor cells. Lin−HLA-DR + DC populations in peripheral blood mononuclear cells (PBMCs) and in ascites mononuclear leukocytes (MNLs) of patients with epithelial ovarian cancer (EOC) are phenotypically immature. Lin−HLA-DR + DCs from PBMCs of normal subjects and EOC patients and MNLs from ascites cells of patients were examined for specific cell surface markers or indicators of differentiation or activation. Separating Lin− HLA-DR+ DCs into subsets based on their HLA-DR intensity provided an additional method for identifying the two major lineages of DCs, myeloid and plasmacytoid. The activation potential of these DCs following exposure to the maturation agents CD40 ligand (CD40L) and lipopolysaccharide (LPS) was examined by measurement of IL-12 and IL-10 concentrations in DC culture supernatants in addition to their ability to stimulate allogeneic T cells. DCs from PBMCs of normal subjects and EOC patients and DCs isolated from ascites MNLs of EOC patients were separated into subsets based on CD11c and CD123 cell surface marker expression identifying the major DC types. These subsets were then compared with cells sorted on the basis of HLA-DR intensity. The in vivo behavior of DCs and DC subsets in peripheral blood and ascites following treatment of peritoneal carcinoma patients with the growth factor fins-like tyrosine kinase 3 ligand (Flt3L) was also examined. Increases in proportions and total numbers of DCs from peripheral blood and ascites were associated with increased secretion of IL-12 and IL-10 following in vitro activation of cultured DCs. There were differences between DCs from PBMCs and ascites and between DC subsets in expression of cell surface markers, cytokine profile, and the ability of Lin−HLA-DR + cells to stimulate proliferation of allogeneic T cells from EOC patients. These Lin−HLA-DR+ cells have certain functional properties that suggest that they could have the potential to facilitate an adaptive anti-tumor immune response. ^

Proteomic identification and functional characterization of prohibitin 1 and 2 in T cell activation, expansion, survival and disease

Several immune pathologies are the result of aberrant regulation of T lymphocytes. Pronounced T cell proliferation can result in autoimmunity or hematologic malignancy, whereas loss of T cell activity can manifest as immunodeficiency. Thus, there is a critical need to characterize the signal transduction pathways that mediate T cell activation so that novel and rational strategies to detect and effectively control T cell mediated disease can be achieved. ^ The first objective of this dissertation was to identify and characterize novel T cell regulatory proteins that are differentially expressed upon antigen induced activation. Using a functional proteomics approach, two members of the prohibitin (Phb) family of proteins, Phb1 and Phb2, were determined to be upregulated upon activation of primary human T cells. Furthermore, their regulated expression was dependent upon CD3 and CD28 signaling pathways which synergistically increased their expression. In contrast to previous reports of Phb nuclear localization, both proteins were determined to localize to the mitochondrial inner membrane of human T cells. Additionally, novel Phb phosphorylation sites were identified and characterized using mass spectrometry, phosphospecific antibodies and site directed mutagenesis. ^ Prohibitins have been proposed to play important roles in cancer development however the mechanism of action has not been elucidated. The second objective of this dissertation was to define the functional role of Phbs in T cell activity, survival and disease. Compared to levels in normal human T cells, Phb expression was higher in the human tumor T cell line Kit225 and subcellularly localized to the mitochondrion. Ablation of Phb expression by siRNA treatment of Kit225 cells resulted in disruption of mitochondrial membrane potential and significantly enhanced their sensitivity to cell death, suggesting they serve a protective function in T cells. Furthermore, Q-RT-PCR analysis of human oncology cDNA expression libraries indicated the Phbs may represent hematological cancer biomarkers. Indeed, Phb1 and Phb2 protein levels were 6-10 fold higher in peripheral blood mononuclear cells isolated from malignant lymphoma and multiple myeloma patients compared to healthy individuals. ^ Taken together, Phb1 and Phb2 are novel phosphoproteins upregulated during T cell activation and transformation to function in the maintenance of mitochondrial integrity and perhaps energy metabolism, thus representing previously unrecognized intracellular biomarkers and therapeutic targets for regulating T cell activation and hematologic malignancies. ^

GMZ27 is a new organic arsenic derivative with anti-leukemic activity, via the induction of reactive oxygen species through NADPH oxidase and mitochondrial pathway that lead to leukemia cell apoptosis

Arsenic trioxide (ATO) is an inorganic arsenic derivative that is very effective against relapsed acute promyelocytic leukemia. It is being investigated as therapy for other cancers, but the risk/benefit ratio is questionable due to significant side effects. In contrast, organic arsenic derivatives (OAD) are known to be much less toxic than ATO. Based on high activity, we selected GMZ27 (dipropil-s-glycerol arsenic) for further study and have confirmed its potent activity against human acute leukemia cell lines. This anti-leukemic activity is significantly higher than that of ATO. Both in vivo and in vitro tests have shown that GMZ27 is significantly less toxic to normal bone marrow mononuclear cells and normal mice. Therefore, further study of the biological activity of GMZ27 was undertaken. ^ GMZ27, in contrast to ATO, can only marginally induce maturation of leukemic cells. GMZ27 has no effect on cell cycle. The anti-leukemic activity of GMZ27 against acute myeolocytic leukemia cells is not dependent upon degradation of PML-RARα fusion protein. GMZ27 causes dissipation of mitochondrial transmembrane potential, cleavage of caspase 9, caspase 3 activation. Further studies indicated that GMZ27 induces intracellular reactive oxygen species (ROS) production, and modification of intracellular ROS levels had profound effect on its potential to inhibit proliferation of leukemic cells. Therefore ROS production plays a major role in the anti-leukemic activity of GMZ27. ^ To identify how GMZ27 induces ROS, our studies focused on mitochondria and NADPH oxidase. The results indicated that the source of ROS generation induced by GMZ27 is dose dependent. At the low dose (0.3 uM) GMZ27 induces NADPH oxidase activity that leads to late ROS production, while at the high dose (2.0 uM) mitochondria function is disrupted and early ROS production is induced leading to dramatic cell apoptosis. Therefore, late, ROS production can be detected in mitochondria are depleted Rho-0 cells. Our work not only delineates a major biologic pathway for the anti-leukemic activity of GMZ27, but also discusses possible ways of enhancing the effect by the co-application of NADPH oxidase activator. Further study of this interaction may lead to achieving better therapeutic index.^

Application of the general linear model to assess the effect of missing data on bone marrow mononuclear cell therapy with infusion timing and follow-up MRI

With most clinical trials, missing data presents a statistical problem in evaluating a treatment's efficacy. There are many methods commonly used to assess missing data; however, these methods leave room for bias to enter the study. This thesis was a secondary analysis on data taken from TIME, a phase 2 randomized clinical trial conducted to evaluate the safety and effect of the administration timing of bone marrow mononuclear cells (BMMNC) for subjects with acute myocardial infarction (AMI).^ We evaluated the effect of missing data by comparing the variance inflation factor (VIF) of the effect of therapy between all subjects and only subjects with complete data. Through the general linear model, an unbiased solution was made for the VIF of the treatment's efficacy using the weighted least squares method to incorporate missing data. Two groups were identified from the TIME data: 1) all subjects and 2) subjects with complete data (baseline and follow-up measurements). After the general solution was found for the VIF, it was migrated Excel 2010 to evaluate data from TIME. The resulting numerical value from the two groups was compared to assess the effect of missing data.^ The VIF values from the TIME study were considerably less in the group with missing data. By design, we varied the correlation factor in order to evaluate the VIFs of both groups. As the correlation factor increased, the VIF values increased at a faster rate in the group with only complete data. Furthermore, while varying the correlation factor, the number of subjects with missing data was also varied to see how missing data affects the VIF. When subjects with only baseline data was increased, we saw a significant rate increase in VIF values in the group with only complete data while the group with missing data saw a steady and consistent increase in the VIF. The same was seen when we varied the group with follow-up only data. This essentially showed that the VIFs steadily increased when missing data is not ignored. When missing data is ignored as with our comparison group, the VIF values sharply increase as correlation increases.^

Evaluation of memory B cells among perinatally HIV infected children from Houston Texas

Background: HIV associated B cell exhaustion is a notable characteristic of HIV viremic adults. However, it is not known if such alterations are present in perinatal HIV infected children, whose viral dynamics differs from those seen in adults. In the present study we perform an analysis of B cells subsets and measure antigen-specific memory B cells (MBC) in a pediatric HIV infected cohort. ^ Methods: Peripheral mononuclear cells (PBMC) of perinatal HIV infected individuals are characterized into naïve (CD21hi/CD27−), classic (CD27+), tissue like (CD21lo/CD27 −) and activated MBC (CD27+CD21− ) by FACS. A memory ELISPOT assay is used to detect antibody secreting cells. We measure total IgG and antibodies specific for influenza, HBV, mumps, measles, rubella and VZV. Memory was expressed as spot forming cells (SPC) /million of PBMC. Wilcoxon rank-sum was used to compare unpaired groups and linear regression analysis was used to determine predictors of B cell dysfunction ^ Results: 41 HIV perinatal infected children are included (51.2% females and 65.9% Black). Age at study is median (range) 8.78 years (4.39-11.57). At the time of testing they have a CD4% of 30.9 (23.2-39.4), a viral load (VL) of 1.95 log10 copies/ml (1.68-3.29) and a cumulative VL of 3.4 log10 copy × days (2.7-4.0). Ninety two percent of the children are on cARV for > 6 months. Overall, HIV+ children compared with controls have a significant lower number of IgG and antigen specific SFC. In addition, they have a lower proportion of classical MBC 12.9 (8.09-19.85) vs 29.4 (18.7-39.05); 0.01, but a significant higher proportion of tissue like memory MBC 6.01 (2.79-12.7) vs 0.99 (0.87-1.38); 0.003, compared with controls. Patients are parsed on VL (<400 and ≥ 400 copies/ml) with the objective to evaluate the effect of VL on B cell status. Patients with a VL ≥ 400 copies/ml have a significantly lower IgG, HBV, measles, rubella and VZV SPC compared with those with a VL < 400 copies/ml. There are no significant differences in B cell subpopulations between the groups. A moderate negative correlation was observed between the time of cARV initiation and the frequency of IgG memory B cells, suggesting that early initiation of cARV appears to lead to a better functionality of the IgG memory B cells (P=0.05). A statistically significant positive correlation was observed between the total number of IgG memory cells and the number of antigen-specific memory B cells/SPCs. Suggesting that the progressive recovery of the IgG memory B cell pull goes along with a progressive increase in the number of antigen-specific SPCs. ^ Conclusion: A pediatric cohort in overall good status with respect to HIV infection and on ART has defects in B cell function and numbers (reduced total and antigen specific MBC and increased tissue like and reduced classical MBC).^

Apoptosis and the molecular complementation of bcl-2, myc and p53 in multistep lymphomagenesis

Follicular lymphoma is the most common lymphoid malignancy in humans. The bcl-2 transgenic mice, which mimic the human follicular lymphoma, initially exhibit a polyclonal hyperplasia due to the overriding of apoptosis by deregulated bcl-2. After a latency period of 15 month 20% of the animals developed clonal lymphomas. Approximately, 50% of these high grade lymphomas presented chromosomal translocations involving c-myc, suggesting that deregulation of this gene is important in the complementation with bcl-2. E$\mu$-myc x bcl-2 double transgenic mice were generated to assess the ability of this two genes to complement in an in vivo system. The double transgenic mice presented a shortened latency (3-4 weeks) and higher incidence of tumor development. Quantification of the extent of programmed cell death indicated that bcl-2 can abrogate the high rate of apoptotic cell death that results from myc deregulation. Bcl-2-Ig, E$\mu$-myc, and bcl-2/E$\mu$-myc lymphomas were examined using PCR-SSCP to detect the presence of p53 mutations in exons 5-9. A high incidence of p53 mutations in E$\mu$-myc lymphomas suggested that inactivating lesions of p53 may represent an important step in the genetic complementation of c-myc in lymphomagenesis. Surprisingly, p53 mutations were quite uncommon in bcl-2 lymphomas suggesting that inactivating mutations of p53 and overexpression of bcl-2 may not cooperate in lymphoma progression. To assess this question, we generated mice that contained a deregulated bcl-2 gene and were nullizygous for p53 (p53KO). No reduction in the tumor latency was observed in the p53KO/bcl-2-Ig hybrid mice when compared with p53 KO mice. Using splenic mononuclear cells isolated from p53KO mice and bcl-2 transgenic mice we demonstrated that bcl-2 suppresses p53 mediated apoptosis in response to DNA damage initiated by $\gamma$-radiation even though p53 protein is induced normally in the bcl-2 overexpressing cells. Western analysis of the expression of p53 target proteins after $\gamma$-radiation showed a correlation between the p53-dependent induction of bax protein after radiation and the ability of p53 to mediate apoptosis. ^

Role and regulation of c-KIT gene expression in tumor growth and metastasis of human melanoma

The purpose of this study was to investigate the role of the c-KIT receptor in the progression of human melanoma and the mechanism(s) for the regulation of c-KIT gene expression in human melanoma.^ The molecular changes associated with the transition of melanoma cells from radial growth phase (RGP) to vertical growth phase (VGP) (metastatic phenotype) are not well-defined. Expression of the tyrosine-kinase receptor c-KIT progressively decreases during local tumor growth and invasion of human melanomas. To provide direct evidence that the metastasis of human melanoma is associated with the loss of c-KIT expression, highly metastatic A375SM cells, which express very low or undetectable levels of c-KIT, were tranduced with the human c-KIT gene. We demonstrated that enforced c-KIT expression in highly metastatic human melanoma cells significantly suppressed their tumorigenicity and metastatic propensity in nude mice. In addition, we showed that the ligand for c-KIT, SCF, induces apoptosis in human melanoma cells expressing c-KIT under both in vitro and in vivo conditions. These results suggest that loss of c-KIT receptor may allow malignant melanoma cells to escape SCF/c-KIT-mediated apoptosis, thus contributing to tumor growth and eventually metastasis.^ Furthermore, we investigated the possible mechanism(s) for the down-regulation of c-KIT gene expression in malignant melanoma. Sequence analysis of the c-KIT promoter indicated that this promoter contains several consensus binding-site sequences including three putative AP2 and two Myb sites. Although Myb was shown to be associated with c-KIT expression in human hemotopoietic cells, we found no correlation between c-KIT expression and Myb expression in human melanoma cell lines. In contrast, we showed that c-KIT expression directly correlates with expression of AP2 in human melanoma cells. We found that highly metastatic cells do not express the transcription factor AP2. Expression of AP2 in A375SM cells (c-KIT-negative and AP2-negative) was enough to restore luciferase activity driven by the c-KIT promoter in a dose-dependent manner. On the other hand, co-expression of the dominant-negative form of AP2 (AP2B) in Mel-501 cells (c-KIT-positive and AP2-positive) resulted in two-fold reduction in luciferase activity. Electrophoretic mobility shift assays revealed that the c-KIT promoter contains functional AP2 binding sites which could associate with AP2 protein. Endogenous c-KIT gene expression levels were elevated in AP2 stably-transfected human melanoma A375SM cells. Expression of exogenous AP2 in A375SM cells inhibited their tumorigenicity and metastatic potential in nude mice. The c-KIT ligand, SCF, also induced apoptosis in the AP2 stably-transfected A375SM cells. The identification of AP2 as an important regulator for c-KIT expression suggests that AP2 may have tumor growth and metastasis inhibitory properties, possibly mediated through c-KIT/SCF effects on apoptosis of human melanoma cells. Since AP2 binding sites were found in the promoters of other genes involved in the progression of human melanoma, such as MMP2 (72 kDa collagenase), MCAM/MUC18 and P21/WAF-1, our findings suggest that loss of AP2 expression might be a crucial event in the development of malignant melanoma. ^