Sridurga Mithraprabhu

Dual epigenetic targeting with panobinostat and azacitidine in acute myeloid leukemia and high-risk myelodysplastic syndrome.

Therapeutic options are limited for elderly patients with acute myeloid leukemia (AML). A phase Ib/II study was undertaken to evaluate the maximum-tolerated dose (MTD) and preliminary efficacy of the pan-histone deacetylase inhibitor panobinostat (LBH589) in combination with azacitidine in patients with AML or high-risk myelodysplastic syndrome (MDS) naïve to intensive chemotherapy. Thirty-nine patients (AML=29, MDS=10) received azacitidine 75 mg/m2 subcutaneously (days 1–5) and oral panobinostat (starting on day 5, thrice weekly for seven doses) in 28-day cycles until toxicity or disease progression. Dose-limiting toxicities during the phase Ib stage were observed in 0/4 patients receiving 10 mg panobinostat, in 1/7 patients (fatigue) receiving 20 mg, in 1/6 patients (fatigue) receiving 30 mg and in 4/5 patients (fatigue, syncope, hyponatremia and somnolence) receiving 40 mg. In phase II, an additional 17 patients received panobinostat at a MTD of 30 mg. The overall response rate (ORR=CR+CRi+PR) in patients with AML was 31% (9/29) and that in patients with MDS was 50% (5/10). After a median follow-up of 13 months, the median overall survival was 8 and 16 months in patients with AML and MDS, respectively. Increased histone H3 and H4 acetylation was a useful early biomarker of clinical response. Combining panobinostat with azacitidine was tolerable and clinically active in high-risk MDS/AML patients, warranting further exploration.

Activin Bioactivity Affects Germ Cell Differentiation in the Postnatal Mouse Testis In Vivo

The transforming growth factor beta superfamily ligand activin A controls juvenile testis growth by stimulating Sertoli cell proliferation. Testicular levels are highest in the first postnatal week, when Sertoli cells are proliferating and spermatogonial stem cells first form. Levels decrease sharply as Sertoli cell proliferation ceases and spermatogenic differentiation begins. We hypothesized that changing activin levels also affect germ cell maturation. We detected an acute and developmentally regulated impact of activin on Kit mRNA in cocultures of Sertoli cells and germ cells from Day 8, but not Day 4, mice. Both stereological and flow cytometry analyses identified an elevated spermatogonium:Sertoli cell ratio in Day 7 testes from InhbaBK/BK mice, which have decreased bioactive activin, and the germ cell markers Sycp3, Dazl, and Ccnd3 were significantly elevated in InhbaBK/BK mice. The flow cytometry measurements demonstrated that surface KIT protein is significantly higher in Day 7 InhbaBK/BK germ cells than in wild-type littermates. By Day 14, the germ cell:Sertoli cell ratio did not differ between genotypes, but the transition of type A spermatogonia into spermatocytes was altered in InhbaBK/BK testes. We conclude that regulated activin signaling not only controls Sertoli cell proliferation, as previously described, but also influences the in vivo progression of germ cell maturation in the juvenile testis at the onset of spermatogenesis.

Dysregulated Class I histone deacetylases are indicators of poor prognosis in multiple myeloma

Histone deacetylases (HDAC) control gene expression through their ability to acetylate proteins, thereby influencing a diverse range of cellular functions. Class I HDAC (HDAC1–3 and 8) and HDAC6 are predominantly upregulated in malignancies and their altered expression in some cancers has a significant prognostic implication. The expression and prognostic consequence of dysregulated Class I HDAC and HDAC6, key players in multiple myeloma (MM), are unknown. This study hypothesized that HDAC are dysregulated in MM and patients with high expression have significantly poorer prognostic outcomes. Quantitative PCR for 11 HDAC (Class I, II, and IV) was performed in genetically heterogeneous human myeloma cell lines (HMCL) and primary MM and compared to normal plasma cells (PC). In HMCL, HDAC1–3 and 8 (Class I), and HDAC5 and HDAC10 (Class II) were significantly upregulated compared to normal PC. In primary MM, the median expression level of all of the HDAC, except HDAC1 and HDAC11, were elevated when compared to normal PC. Patients with higher levels of HDAC1–3, HDAC4, HDAC6, and HDAC11 transcripts demonstrated a significantly shorter progression-free survival (PFS). Immunohistochemical staining for HDAC1 and HDAC6 on bone marrow trephines from a uniformly treated cohort of transplant eligible MM patients revealed that HDAC1 protein was detectable in most patients and that higher levels of MM cell HDAC1 protein expression (≥90 % versus ≤20 % MM cell positivity) correlated with both shorter PFS (P = 0 .07) and shorter overall survival (P = 0 .003). Conversely, while the majority of patients expressed HDAC6, there was no correlation between HDAC6 levels and patient outcome. Together, these results indicate that overexpression of Class I HDAC, particularly HDAC1, is associated with poor prognosis in MM.

Control of KIT signalling in male germ cells: what can we learn from other systems?

The KIT ligand (KITL)/KIT-signalling system is among several pathways known to be essential for fertility. In the postnatal testis, the KIT/KITL interaction is crucial for spermatogonial proliferation, differentiation, survival and subsequent entry into meiosis. Hence, identification of endogenous factors that regulate KIT synthesis is important for understanding the triggers driving germ cell maturation. Although limited information is available regarding local factors in the testicular microenvironment that modulate KIT synthesis at the onset of spermatogenesis, knowledge from other systems could be used as a basis for identifying how KIT function is regulated in germ cells. This review describes the known regulators of KIT, including transcription factors implicated in KIT promoter regulation. In addition, specific downstream outcomes in biological processes that KIT orchestrates are addressed. These are discussed in relationship to current knowledge of mammalian germ cell development.

Circulating tumour DNA analysis demonstrates spatial mutational heterogeneity that coincides with disease relapse in myeloma

Mutational characterisation in multiple myeloma (MM) currently relies on bone marrow (BM) biopsy, which fails to capture the putative spatial and genetic heterogeneity of this multifocal disease. Analysis of plasma (PL)-derived circulating free tumour DNA (ctDNA) as an adjunct to BM biopsy, for mutational characterisation and tracking disease progression, was evaluated. Paired BM MM cell DNA and ctDNA from 33 relapsed/refractory (RR) and 15 newly diagnosed (ND) patients were analysed for KRAS, NRAS, BRAF and TP53 mutations using the OnTarget Mutation Detection (OMD) platform. OMD detected 128 mutations (PL=31, BM=59, both=38) indicating the presence of PL mutations (54%). A higher frequency of PL-only mutations was detected in RR patients than ND (27.2% vs 6.6%, respectively), authenticating the existence of spatial and genetic heterogeneity in advanced disease. Activating RAS mutations were more highly prevalent than previously described with 69% harboring at least one RAS mutation. Sequential ctDNA quantitation with droplet digital PCR through longitudinal PL tracking of specific clones in seven patients demonstrated changes in fractional abundance of certain clones reflective of the disease status. We conclude that ctDNA analysis as an adjunct to BM biopsy represents a noninvasive and holistic strategy for improved mutational characterisation and therapeutic monitoring of MM.

Histone deacetylase (HDAC) inhibitors as single agents induce multiple myeloma cell death principally through the inhibition of class I HDAC

ence of ADAMTS13 inhibitors, in terms of pathophysiology, illustrated by deposition of terminal complement components in the patient’s skin (see Chapin et al, 2012) and his response to anti-C5 but not plasma therapy, our patient has a coexistent disease process involving both TTP and aHUS. We propose that similar disease processes may also explain the poor response of at least a subset of TTP patients to plasma exchange therapy.

TCam-2 seminoma cell line exhibits characteristic foetal germ cell responses to TGF-beta ligands and retinoic acid

Germ cell testicular cancer is understood to arise during embryogenesis, based on the persistence of embryonic germ cell markers in carcinoma in situ and seminoma. In this study, we examine the potential of the seminoma-derived TCam-2 cell line to be used as representative in functional analyses of seminoma. We demonstrate expression of several early germ cell markers, including BLIMP1, OCT3/4, AP2γ, NANOG and KIT. Many TGF-beta superfamily receptors and downstream transcription factors are also present in these cells including the normally foetal ACTRIIA receptor, indicating potential responsiveness to TGF-beta superfamily ligands. Treatment with BMP4 or RA induces a significant increase in ACTRIA, ACTRIIA and ACTRIIB transcripts, whereas activin A decreases ACTRIB. BMP4 and RA each support TCam-2 survival and/or proliferation. In addition, despite increased KIT mRNA levels induced by BMP4, RA and activin A, activin A does not improve survival or proliferation. The capacity for BMP4 and retinoic acid to enhance foetal germ cell survival and proliferation/self-renewal has been demonstrated in mice, but not previously tested in humans. This study is the first to demonstrate a functional response in seminoma cells, using a well-characterized cell line, consistent with their foetal germ cell-like identity.

Deactylase inhibition in myeloproliferative neoplasms.

SummaryMyeloproliferative neoplasms (MPN) are clonal haemopoietic progenitor cell disorders characterized by the proliferation of one or more of the haemopoietic lineages (myeloid, erythroid and/or megakaryocytic). The MPNs include eight haematological disorders: chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), systemic mastocytosis (SM), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), chronic neutrophilic leukemia (CNL), and unclassifiable MPN (MPN, U). Therapeutic interventions for MPNs include the use of tyrosine kinase inhibitors (TKIs) for BCR-ABL1+ CML and JAK2 inhibitors for PV, ET and PMF. Histone deacetylase inhibitors (HDACi) are a novel class of drugs capable of altering the acetylation status of both histone and non-histone proteins, thereby affecting a repertoire of cellular functions in neoplastic cells including proliferation, differentiation, immune responses, angiogenesis and survival. Preliminary studies indicate that HDACi when used in combination with tyrosine kinase or JAK2 inhibitors may overcome resistance to the latter agents and enhance the pro-apoptotic effects on MPN cells. This review provides a review of pre-clinical and clinical studies that have explored the use of HDACi as potential therapeutics for MPNs.

Liquid biopsies for liquid tumors: emerging potential of circulating free nucleic acid evaluation for the management of hematologic malignancies

Circulating free nucleic acids; cell free DNA and circulating micro-RNA, are found in the plasma of patients with hematologic and solid malignancies at levels higher than that of healthy individuals. In patients with hematologic malignancy cell free DNA reflects the underlying tumor mutational profile, whilst micro-RNAs reflect genetic interference mechanisms within a tumor and potentially the surrounding microenvironment and immune effector cells. These circulating nucleic acids offer a potentially simple, non-invasive, repeatable analysis that can aid in diagnosis, prognosis and therapeutic decisions in cancer treatment.

Overcoming inherent resistance to histone deacetylase inhibitors in multiple myeloma cells by targeting pathways integral to the actin cytoskeleton

Histone deacetylase inhibitors (HDACi) are novel chemotherapeutics undergoing evaluation in clinical trials for the potential treatment of patients with multiple myeloma (MM). Although HDACi have demonstrable synergy when combined with proteasome inhibitors (PIs), recent evidence indicates that combination of HDACi and PI is beneficial only in a subset of patients with advanced MM, clearly indicating that other rational combinations should be explored. In this context we hypothesized that understanding the molecular signature associated with inherent resistance to HDACi would provide a basis for the identification of therapeutic combinations with improved clinical efficacy. Using human myeloma cell lines (HMCL) categorized as sensitive, intermediate or resistant to HDACi, gene expression profiling (GEP) and gene ontology enrichment analyses were performed to determine if a genetic signature associated with inherent resistance to HDACi-resistance could be identified. Correlation of GEP to increasing or decreasing sensitivity to HDACi indicated a unique 35-gene signature that was significantly enriched for two pathways – regulation of actin cytoskeleton and protein processing in endoplasmic reticulum. When HMCL and primary MM samples were treated with a combination of HDACi and agents targeting the signaling pathways integral to the actin cytoskeleton, synergistic cell death was observed in all instances, thus providing a rationale for combining these agents with HDACi for the treatment of MM to overcome resistance. This report validates a molecular approach for the identification of HDACi partner drugs and provides an experimental framework for the identification of novel therapeutic combinations for anti-MM treatment.