Tiffany Simms-Waldrip

FMS‐Like Tyrosine Kinase 3 in Normal Hematopoiesis and Acute Myeloid Leukemia

Ligand‐mediated activation of the FMS‐like tyrosine kinase 3 (FLT3) receptor is important for normal proliferation of primitive hematopoietic cells. However, activating mutations in FLT3 induce ligand‐independent downstream signaling that promotes oncogenesis through pathways involved in proliferation, differentiation, and survival. FLT3 mutations are identified as the most frequent genetic abnormality in acute myeloid leukemia and are also observed in other leukemias. Multiple small‐molecule inhibitors are under development to target aberrant FLT3 activity that confers a poor prognosis in patients.

Activation of HIF-1α and LL-37 by commensal bacteria inhibits Candida albicans colonization

Candida albicans colonization is required for invasive disease. Unlike humans, adult mice with mature intact gut microbiota are resistant to C. albicans gastrointestinal (GI) colonization, but the factors that promote C. albicans colonization resistance are unknown. Here we demonstrate that commensal anaerobic bacteria—specifically clostridial Firmicutes (clusters IV and XIVa) and Bacteroidetes—are critical for maintaining C. albicans colonization resistance in mice. Using Bacteroides thetaiotamicron as a model organism, we find that hypoxia-inducible factor-1α (HIF-1α), a transcription factor important for activating innate immune effectors, and the antimicrobial peptide LL-37 (CRAMP in mice) are key determinants of C. albicans colonization resistance. Although antibiotic treatment enables C. albicans colonization, pharmacologic activation of colonic Hif1a induces CRAMP expression and results in a significant reduction of C. albicans GI colonization and a 50% decrease in mortality from invasive disease. In the setting of antibiotics, Hif1a and Camp (which encodes CRAMP) are required for B. thetaiotamicron–induced protection against C. albicans colonization of the gut. Thus, modulating C. albicans GI colonization by activation of gut mucosal immune effectors may represent a novel therapeutic approach for preventing invasive fungal disease in humans.

The aggresome pathway as a target for therapy in hematologic malignancies

Misfolded or unfolded proteins are often refolded with the help of chaperones or degraded by the 26S proteasome. An alternative fate of these proteins is the aggresome pathway. The microtubule-organizing center (MTOC) transports unfolded proteins to lysosomes and are degraded through autophagy. Histone deacetylase 6 (HDAC6) deacetylates alpha-tubulin, which is thought to be a component of the MTOC. Recently, two small molecule inhibitors of the aggresome pathway and HDAC6 have been described. One inhibitor, tubacin, prevents deacetylation of alpha-tubulin and produces accumulation of polyubiquitinated proteins and apoptosis. Tubacin acts synergistically with the proteasome inhibitor, bortezomib, to induce cytotoxicity in one type of hematologic malignancy, multiple myeloma. The other, LBH589, is a pan HDAC inhibitor and hydroxamic acid derivative that induces apoptosis of multiple myeloma cells resistant to conventional therapies. In this review, we summarize recent reports on targeting the aggresome pathway and HDAC6 in hematologic malignancies.

Antibiotic-Induced Depletion of Anti-inflammatory Clostridia Is Associated with the Development of Graft-versus-Host Disease in Pediatric Stem Cell Transplantation Patients

Adult stem cell transplantation (SCT) patients with graft-versus-host-disease (GVHD) exhibit significant disruptions in gut microbial communities. These changes are associated with higher overall mortality and appear to be driven by specific antibiotic therapies. It is unclear whether pediatric SCT patients who develop GVHD exhibit similar antibiotic-induced gut microbiota community changes. Here, we show that pediatric SCT patients (from Childrens Medical Center Dallas, n = 8, and Cincinnati Childrens Hospital, n = 7) who developed GVHD showed a significant decline, up to 10-log fold, in gut anti-inflammatory Clostridia (AIC) compared with those without GVHD. In fact, the development of GVHD is significantly associated with this AIC decline and with cumulative antibiotic exposure, particularly antibiotics effective against anaerobic bacteria (P = .003, Firth logistic regression analysis). Using metagenomic shotgun sequencing analysis, we were able to identify specific commensal bacterial species, including AIC, that were significantly depleted in GVHD patients. We then used a preclinical GVHD model to verify our clinical observations. Clindamycin depleted AIC and exacerbated GVHD in mice, whereas oral AIC supplementation increased gut AIC levels and mitigated GVHD in mice. Together, these data suggest that an antibiotic-induced AIC depletion in the gut microbiota is associated with the development of GVHD in pediatric SCT patients.

Invasive fungal infections in pediatric hematopoietic stem cell transplant patients

Abstract Background: Pediatric hematopoietic stem cell transplant (HSCT) recipients are at high risk of invasive fungal infections (IFIs). Methods: To characterize IFIs and changes in fungal organisms over time in pediatric HSCT patients, we performed a retrospective cohort study of all HSCTs performed in pediatric patients at UCLA between 1991 and 2006. Results: In all, 318 patients underwent 324 HSCT transplants over the 15-year period and 69 unique fungal infections were identified in 47 transplant patients. The overall incidence of fungal infections in HSCT recipients was 14.5%, with predominant organisms including Candida species (51%) and Aspergillus species (26%), with Candida albicans accounting for 18.8% of all fungal species. The distribution of organisms over time demonstrated a strong trend towards an increase in rare molds in more recent years. The respiratory tract was the main site of infection (52.6%), with urine and blood also noted as significant sites. Of all deaths in the patients with IFIs, fungal-related mortality accounted for 67.6% of deaths. Conclusions: HSCT patients have a much higher risk of fungal infections with rarer organisms becoming more prevalent, a finding likely linked to evolving antifungal practices over time. This emphasizes the need for the development and implementation of improved diagnostic, prophylactic, and therapeutic strategies to improve patient survival.

Dramatic response to rituximab in a child with severe cold autoimmune hemolytic anemia arising after allogeneic hematopoietic SCT.

Dramatic response to rituximab in a child with severe cold autoimmune hemolytic anemia arising after allogeneic hematopoietic SCT

145 TARGETING BCL-2 IN ACUTE MYELOID LEUKEMIA CELLS.

Purpose of Study Proteins of the Bcl-2 family members are critical regulators of programmed cell death, and members that inhibit apoptosis, including Bcl-2 and Bcl-XL, are overexpressed in many cancers and contribute to tumor initiation, progression, and resistance to therapy. ABT-737 is a small molecule inhibitor of Bcl-2, Bcl-XL, and Bcl-w that was identified using nuclear magnetic resonance-based screen, parallel synthesis, and structure-based design. Previous studies revealed that this inhibitor does not initiate apoptosis but enhances the effects of death signals and acts synergistically with chemotherapy and radiation to induce cytotoxicity. ABT-737 as a single agent kills cells from lymphoma and small cell lung carcinoma lines in vitro and in vivo. In this study, we investigated the effects of ABT-737 on three different human acute myeloid leukemia (AML) cell lines. Methods Two human AML cell lines, KG-1 and MV-411, were treated with varying concentrations of ABT-737 ranging from 1 pM to 10 μM in complete media containing 10% fetal calf serum (FCS). Another human AML cell line, Molm-13, was treated with ABT-737 at concentrations ranging from 1 nM to 10 μM in media containing either 10% FCS or 1% FCS. Percent viability was determined using trypan blue exclusion at 24, 48, 72 hours following treatment with ABT-737. Results ABT-737 was found to inhibit KG-1 cell proliferation at an IC50 of 100 nM following treatment with ABT-737 for 96 hours. The IC50 of the MV-411 cell line was 10 nM after 24 hours of treatment. Molm-13 cells cultured in media containing 10% FCS showed an IC50 of 1 μM at 24 hours following treatment and 100 nM after 48 and 72 hours. Molm-13 cells grown in media containing 1% FCS demonstrated a decrease in percent viability with an IC50 of 100 nM after 24 hours of treatment, 10 nM after 48 hours, and 1 nM after 72 hours following treatment with ABT-737. Conclusions The AML cell lines KG-1, MV-411, and Molm-13 were susceptible to the pro-apoptotic effects of ABT-737 in vitro. Thus, further investigation into the effects of ABT-737 on additional AML cell lines in vitro and in vivo is warranted. We conclude that ABT-737 either alone or in combination with chemotherapy may provide an alternative mode of therapy for patients with AML.