Heat shock protein 70 – the next chaperone to target in the treatment of human acute myelogenous leukemia?

Therapeutic potency of heat-shock protein-70 in the pathogenesis of colorectal cancer: current status and perspectives

Heat-shock protein-70 (HSP70) is critical to the folding, stability, and activity of several client proteins including many responsible for cancer cell proliferation, apoptosis, drug toxicity, and metastasis. Up-regulation of HSP70 is positively associated with increased tumorigenicity as well as poor survival in colon cancer patients, supporting the diagnostic, prognostic, and therapeutic potencies of HSP70 in colorectal cancer. The administration of specific pharmacological inhibitors or gene knock-down for HSP70 suppresses tumor progression and enhances tumor cell chemosensitivity. This review summarizes the different tumorigenic properties of HSP70 and the potential therapeutic potency of HSP70 inhibitors in terms of a novel strategy for colorectal cancer therapy, for a better understanding, and hence better management of this disease.

Control of RUNX-induced repression of Notch signaling by MLF and its partner DnaJ-1 during Drosophila hematopoiesis

A tight regulation of transcription factor activity is critical for proper development. For instance, modifications of RUNX transcription factors dosage are associated with several diseases, including hematopoietic malignancies. In Drosophila, Myeloid Leukemia Factor (MLF) has been shown to control blood cell development by stabilizing the RUNX transcription factor Lozenge (Lz). However, the mechanism of action of this conserved family of proteins involved in leukemia remains largely unknown. Here we further characterized MLF's mode of action in Drosophila blood cells using proteomic, transcriptomic and genetic approaches. Our results show that MLF and the Hsp40 co-chaperone family member DnaJ-1 interact through conserved domains and we demonstrate that both proteins bind and stabilize Lz in cell culture, suggesting that MLF and DnaJ-1 form a chaperone complex that directly regulates Lz activity. Importantly, dnaj-1 loss causes an increase in Lz+ blood cell number and size similarly as in mlf mutant larvae. Moreover we find that dnaj-1 genetically interacts with mlf to control Lz level and Lz+ blood cell development in vivo. In addition, we show that mlf and dnaj-1 loss alters Lz+ cell differentiation and that the increase in Lz+ blood cell number and size observed in these mutants is caused by an overactivation of the Notch signaling pathway. Finally, using different conditions to manipulate Lz activity, we show that high levels of Lz are required to repress Notch transcription and signaling. All together, our data indicate that the MLF/DnaJ-1-dependent increase in Lz level allows the repression of Notch expression and signaling to prevent aberrant blood cell development. Thus our findings establish a functional link between MLF and the co-chaperone DnaJ-1 to control RUNX transcription factor activity and Notch signaling during blood cell development in vivo.

Panobinostat for the treatment of acute myelogenous leukemia

INTRODUCTION

Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi).

AREAS COVERED

The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML.

EXPERT OPINION

Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.

Emerging therapeutic targets for the treatment of human acute myeloid leukemia (part 1) - gene transcription, cell cycle regulation, metabolism and intercellular communication

Human acute myeloid leukemia is a heterogeneous disease and the effect of therapeutic targeting of specific molecular mechanisms will probably vary between patient subsets. Cell cycle regulators are among the emerging targets (e.g., aurora and polo-like kinases, cyclin-dependent kinases). Inhibition of communication between acute myeloid leukemia and stromal cells is also considered; among the most promising of these strategies are inhibition of hedgehog-initiated, CXCR4-CXCL12 and Axl-Gas6 signaling. Finally, targeting of energy and protein metabolism is considered, the most promising strategy being inhibition of isocitrate dehydrogenase in patients with IDH mutations. Thus, several strategies are now considered, and a major common challenge for all of them is to clarify how they should be combined with each other or with conventional chemotherapy, and whether their use should be limited to certain subsets of patients.