Search

This in vitro study aimed at investigating whether full remineralization would occur in white spot lesions when the surface porosity was increased by acid-etching. The effect of fluoride was also investigated. Enamel blocks with in vitro produced white spot lesions were used. Group A was exposed to a remineralizing solution only. In group B, the lesions were etched with 35% phosphoric acid for 30 s, then treated as in group A. Group C was treated as group A + daily treatment with a fluoride toothpaste slurry (1,000 ppm) for 5 min. Group D was treated as group B + the daily fluoride treatment of group C. The remineralization was measured weekly with Quantitative Light-induced Fluorescence during the experimental period. After 10 weeks of remineralization, mineral profiles were assessed with transverse microradiography. The enamel fluorescence was partly regained. There were significant differences in the lesion depth, mineral content at the surface layer, and integrated mineral loss between the groups. Addition of fluoride accelerated the remineralization only in the beginning; in later stages the process leveled out and even reached a plateau in all the groups. It was concluded that full remineralization was not achieved by etching, by the addition of fluoride, nor by the combination of both treatments in this in vitro study. [ABSTRACT FROM AUTHOR]

Despite recent advances, treatment of leukemia is often not curative. New insights indicate that this may be attributable to a small population of therapy-resistant malignant cells with self-renewal capacity and the ability to generate large numbers of more differentiated leukemia cells. These leukemia-initiating cells are commonly referred to as Leukemia Stem Cells (LSCs). LSCs are regarded as the root of leukemia origin and leukemia recurrence after seemingly successful therapy. Not surprisingly therefore, contemporary leukemia research has focused on ways to specifically eliminate LSCs, leading to the identification of several promising anti-LSC strategies. Firstly, LSCs may be eliminated by antibody- or ligand-based cell surface delivery of therapeutics such as naked antibodies, immunotoxins, and immunocytokines. This approach exploits LSC-associated surface antigens, such as CD33, CD44, CD96, CD123 and CLL-1 for LSC-selective therapy and aims to spare normal hematopoietic stem cells. A second strategy aims to disrupt the interactions between LSCs and their highly specialized niche. These interactions appear to be pivotal for maintenance of the stem cell-like characteristics of LSCs. A third strategy centers on the selective modulation of aberrantly activated signaling pathways central to LSC biology. A fourth strategy, dubbed 'epigenetic reprogramming', aims to selectively reverse epigenetic alterations that are implicated in ontogeny and maintenance of LSCs. In this review, we will discuss the rationale for these LSCs-targeted strategies and highlight recent advances that may ultimately help pave the way towards selective LSCs-elimination.

Previously, we have shown that epidermal growth factor receptor (EGFR)-selective delivery of soluble tumor necrosis factor-related apoptosis-inducing ligand (sTRAIL), by genetic fusion to antibody fragment scFv425, enhances the tumor-selective pro-apoptotic activity of sTRAIL. Insight into the respective contribution of the agonistic receptors TRAIL-R1 and TRAIL-R2 to TRAIL-induced apoptosis may provide a rational approach to further optimize TRAIL-based therapy. Recently, this issue has been investigated using sTRAIL mutants designed to selectively bind to either receptor. However, the relative contribution of the respective TRAIL receptors, in particular TRAIL-R1, in TRAIL signaling is still unresolved. Here, we fused scFv425 to designed sTRAIL mutant sTRAILmR1-5, reported to selectively activate TRAIL-R1, and investigated the therapeutic apoptotic activity of this novel fusion protein. EGFR-specific binding of scFv425:sTRAILmR1-5 potently induced apoptosis, which was superior to the apoptotic activity of scFv425:sTRAIL-wt and a nontargeted MOCK-scFv:sTRAILmR1-5. During cotreatment with cisplatin or the histone deacetylase inhibitor valproic acid, scFv425:sTRAILmR1-5 retained its superior pro-apoptotic activity compared to scFv425:sTRAIL-wt. However, in catching-type Enzyme-Linked ImmunoSorbent Assays with TRAIL-R1:Fc and TRAIL-R2:Fc, scFv425:sTRAILmR1-5 was found to not only bind to TRAIL-R1 but also to TRAIL-R2. Binding to TRAIL-R2 also had functional consequences because the apoptotic activity of scFv425:sTRAILmR1-5 was strongly inhibited by a TRAIL-R2 blocking monoclonal antibody. Moreover, scFv425:sTRAILmR1-5 retained apoptotic activity upon selective knockdown of TRAIL-R1 using small inhibitory RNA. Collectively, these data indicate that both agonistic TRAIL receptors are functionally involved in TRAIL signaling by scFv425:sTRAILmR1-5 in solid tumor cells. Moreover, the superior target cell-restricted apoptotic activity of scFv425:sTRAILmR1-5 indicates its therapeutic potential for EGFR-positive solid tumors.

Although the treatment outcome of lymphoid malignancies has improved in recent years by the introduction of transplantation and antibody-based therapeutics, relapse remains a major problem. Therefore, new therapeutic options are urgently needed. One promising approach is the selective activation of apoptosis in tumor cells by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). This study investigated the pro-apoptotic potential of a novel TRAIL fusion protein designated scFvCD19:sTRAIL, consisting of a CD19-specific single-chain Fv antibody fragment (scFv) fused to the soluble extracellular domain of TRAIL (sTRAIL). Potent apoptosis was induced by scFvCD19:sTRAIL in several CD19-positive tumor cell lines, whereas normal blood cells remained unaffected. In mixed culture experiments, selective binding of scFvCD19:sTRAIL to CD19-positive cells resulted in strong induction of apoptosis in CD19-negative bystander tumor cells. Simultaneous treatment of CD19-positive cell lines with scFvCD19:sTRAIL and valproic acid (VPA) or Cyclosporin A induced strongly synergistic apoptosis. Treatment of patient-derived acute B-lymphoblastic leukemia (B-ALL) and chronic B-lymphocytic leukemia (B-CLL) cells resulted in strong tumoricidal activity that was further enhanced by combination with VPA. In addition, scFvCD19:sTRAIL prevented engraftment of human Nalm-6 cells in xenotransplanted NOD/Scid mice. The pre-clinical data presented here warrant further investigation of scFvCD19:sTRAIL as a potential new therapeutic agent for CD19-positive B-lineage malignancies.

The clinical efficacy of the CD20-specific chimeric monoclonal antibody rituximab is significantly hampered by intrinsic or acquired resistance to therapy. Rituximab activates antibody-dependent cellular cytotoxicity/complement-dependent cytotoxicity-dependent lysis but also induces apoptosis by cross-linking of its target antigen CD20. Recent reports indicate that this apoptotic activity of rituximab can be synergized by cotreatment with Fas agonists. Here, we report on a strategy designed to exploit and optimize the synergy between rituximab and Fas signaling by genetically fusing a rituximab-derived antibody fragment to soluble Fas ligand (sFasL). The resultant fusion protein, designated scFvRit:sFasL, potently induced CD20-restricted apoptosis in a panel of malignant B-cell lines (10 of 11) and primary patient-derived malignant B cells (two of two non-Hodgkin lymphoma and five of six B cell chronic lymphocytic leukemia). ScFvRit:sFasL efficiently activated CD20 and Fas apoptotic signaling, resulting in a far superior proapoptotic activity compared with cotreatment with rituximab and Fas agonists. ScFvRit:sFasL lacked activity toward normal human B cells and also lacked systemic toxicity in nude mice with no elevation of aspartate aminotransferase and alanine aminotransferase levels or liver caspase-3 activity. In conclusion, scFvRit:sFasL efficiently activates CD20 and Fas-apoptotic signaling and may be useful for the elimination of malignant B cells.

Ab binding to CD20 has been shown to induce apoptosis in B cells. In this study, we demonstrate that rituximab sensitizes lymphoma B cells to Fas-induced apoptosis in a caspase-8-dependent manner. To elucidate the mechanism by which Rituximab affects Fas-mediated cell death, we investigated rituximab-induced signaling and apoptosis pathways. Rituximab-induced apoptosis involved the death receptor pathway and proceeded in a caspase-8-dependent manner. Ectopic overexpression of FLIP (the physiological inhibitor of the death receptor pathway) or application of zIETD-fmk (specific inhibitor of caspase-8, the initiator-caspase of the death receptor pathway) both specifically reduced rituximab-induced apoptosis in Ramos B cells. Blocking the death receptor ligands Fas ligand or TRAIL, using neutralizing Abs, did not inhibit apoptosis, implying that a direct death receptor/ligand interaction is not involved in CD20-mediated cell death. Instead, we hypothesized that rituximab-induced apoptosis involves membrane clustering of Fas molecules that leads to formation of the death-inducing signaling complex (DISC) and downstream activation of the death receptor pathway. Indeed, Fas coimmune precipitation experiments showed that, upon CD20-cross-linking, Fas-associated death domain protein (FADD) and caspase-8 were recruited into the DISC. Additionally, rituximab induced CD20 and Fas translocation to raft-like domains on the cell surface. Further analysis revealed that, upon stimulation with rituximab, Fas, caspase-8, and FADD were found in sucrose-gradient raft fractions together with CD20. In conclusion, in this study, we present evidence for the involvement of the death receptor pathway in rituximab-induced apoptosis of Ramos B cells with concomitant sensitization of these cells to Fas-mediated apoptosis via Fas multimerization and recruitment of caspase-8 and FADD to the DISC.

Clinpro Cario L-Pop (CCLP) is a semiquantitive test claimed to determine the general potential for caries development and to monitor the individual caries risk. This test translates the capacity of the tongue microflora to produce lactic acid into a score of 1-9, indicating a low, medium or high risk for caries development. The aim of this randomized crossover, clinical trial was to evaluate the CCLP on its variation over time and its capacity to monitor the effect of three different oral hygiene procedures. The CCLP readings were compared with measurements of lactic acid in tongue biofilm and plaque samples by capillary ion electrophoresis (CIA). After four washout periods, the distribution of scores in the low-, medium-, and high-risk categories was 10%, 16%, and 74%, respectively. Out of 30 subjects, 11 scored consistently in the same category. The coefficients of variance of lactic acid concentrations were 31% for tongue samples and 25% for plaque samples. After using antimicrobial toothpaste and mouthwash, the number of high-risk scores was reduced to 33%; reduced acidogenicity was also found in tongue and plaque samples. We conclude that CCLP can be used to monitor and stimulate compliance to an antimicrobial oral hygiene protocol.

Agonistic anti-Fas antibodies and multimeric recombinant Fas ligand (FasL) preparations show high tumoricidal activity against leukemic cells, but are unsuitable for clinical application due to unacceptable systemic toxicity. Consequently, new antileukemia strategies based on Fas activation have to meet the criterion of strictly localized action at the tumor-cell surface. Recent insight into the FasL/Fas system has revealed that soluble homotrimeric FasL (sFasL) is in fact nontoxic to normal cells, but also lacks tumoricidal activity. We report on a novel fusion protein, designated scFvCD7:sFasL, that is designed to have leukemia-restricted activity. ScFvCD7:sFasL consists of sFasL genetically linked to a high-affinity single-chain fragment of variable regions (scFv) antibody fragment specific for the T-cell leukemia-associated antigen CD7. Soluble homotrimeric scFvCD7:sFasL is inactive and acquires tumoricidal activity only after specific binding to tumor cell-surface-expressed CD7. Treatment of T-cell acute lymphoblastic leukemia (T-ALL) cell lines and patient-derived T-ALL, peripheral T-cell lymphoma (PTCL), and CD7-positive acute myeloid leukemia (AML) cells with homotrimeric scFvCD7:sFasL revealed potent CD7-restricted induction of apoptosis that was augmented by conventional drugs, farnesyl transferase inhibitor L-744832, and the proteasome inhibitor bortezomib (Velcade; Millenium, Cambridge, MA). Importantly, identical treatment did not affect normal human peripheral-blood lymphocytes (PBLs) and endothelial cells, with only moderate apoptosis in interleukin-2 (IL-2)/CD3-activated T cells. CD7-restricted activation of Fas in T-cell leukemic cells by scFvCD7:sFasL revitalizes interest in the applicability of Fas signaling in leukemia therapy.

The aim of the study was to explore multivariately the relationship between subjective symptoms allegedly due to amalgam and mercury measurements before and after administration of a chelator. Of 120 participants, the mercury concentrations in urine (U-Hg) and plasma (P-Hg) before and after a chelating agent or placebo were determined as were the numbers of fillings and symptoms allegedly due to subjective symptoms. The dental status was charted. Blood was analysed on 13 parameters. The analysis revealed neither the parameters in blood nor the subjective symptoms to be associated with a dimension dominated by 'mercury indicators'. The final analysis was therefore performed with 'number of subjective symptoms' and enabled to distinguish two subsamples. One subsample was characterised by > 2 subjective "symptoms", highest scores for U-Hg, P-Hg and filled surfaces, and chewing gum for > 1 h a day. The other subsample comprised the subjects with few filled surfaces and low U-Hg and P-Hg, but was not characterised by "no subjective symptoms". The chelator was considered neither to invalidate nor to improve these findings and was concluded not to be helpful in diagnosing "symptoms". The chelator caused side effects in 42% of the subjects and the placebo in 27%. A relationship between amalgam fillings and subjective symptoms could not be shown. Therefore, the mere fact of knowing to have amalgam fillings was assumed to be the reason why subjective symptoms were attributed to amalgam and side effects were ascribed to the treatment.