Apoptosis regulating proteins as targets of therapy for haematological malignancies

Pre-Ischemic Hypothermic Oxygenated Perfusion Alleviates Protective Molecular Markers of Ischemia-Reperfusion Injury in Rat Liver

To expand the pool of organs, hypothermic oxygenated perfusion (HOPE), one of the most promising perfusion protocols, is currently performed after cold storage (CS) at transplant centers (HOPE-END). We investigated a new timing for HOPE, hypothesizing that performing HOPE before CS (HOPE-PRE) could boost mitochondrial protection allowing the graft to better cope with the accumulation of oxidative stress during CS. We analyzed liver injuries at 3 different levels. Histologic analysis demonstrated that, compared to classical CS (CTRL), the HOPE-PRE group showed significantly less ischemic necrosis compared to CTRL vs HOPE-END. From a biochemical standpoint, transaminases were lower after 2 hours of reperfusion in the CTRL vs HOPE-PRE group, which marked decreased liver injury. qPCR analysis on 37 genes involved in ischemia-reperfusion injury revealed protection in HOPE-PRE and HOPE-END compared to CTRL mediated through similar pathways. However, the CTRL vs HOPE-PRE group demonstrated an increased transcriptional level for protective genes compared to the CTRL vs HOPE-END group. This study provides insights on novel biomarkers that could be used in the clinic to better characterize graft quality improving transplantation outcomes.

Differential mRNA expression of the main apoptotic proteins in normal and malignant cells and its relation to in vitro resistance

Background

Apoptosis plays an important role in the development and homeostasis of multicellular organisms and its deregulation may result in many serious diseases, including cancer. Now it is clear that some oncogenic mutations disrupt apoptosis, leading to tumour initiation, progression or metastasis. Here, expression of apoptotic genes in context of drug resistance was investigated.

Methods

We examined total of 102 samples from leukemic patients (n = 60) and patients with solid tumours (n = 42). We used RT-PCR to determine the levels of mRNA expression and the in vitro chemoresistance of leukemic cells was evaluated using the MTT assay.

Results

We found statistically significant increase in mRNA expression of all investigated proteins (p53, BAX, Bcl-2 and Bcl-XL) between the leukemia samples and leukocytes from healthy volunteers. We did not find any significant difference in mRNA levels among the solid tumour samples. Notably, we showed a significant positive correlation in both leukemic and solid tumour patient groups between p53 and BAX mRNA. We found that the highest values for the Bcl-2/BAX ratio were in solid tumours in comparison to leukemic cells or normal leukocytes. Moreover, we assessed the impact of p53 and BAX mRNA levels on the sensitivity of the leukemic cells to selected cytostatics.

Conclusions

Elevated levels of p53 and BAX mRNA may indicate cellular response to possible changes in genomic DNA integrity associated with malignant transformation. We suggest that the BAX gene is regulated by the p53 protein but the initiation of apoptosis through the transcription activation of BAX is blocked by the high levels of Bcl-2. Given that the apoptosis resistance mechanisms are different among oncological patients as well as stages of identical malignancy cases, personalized and specific combination therapy is proposed to be more effective in clinical application.

Rituximab combined with a small dose of melphalan for a refractory follicular lymphoma patient

A 48-year-old male patient with follicular lymphoma, grade II, stage IV, was treated with CHOP, ESHAP and MACOP-B, resulting in partial remission. After 9 months, the disease progressed and several chemotherapy agents, including three courses of rituximab combined with etoposide, sobuzoxane or methotrexate, only resulted in a stable disease response. However, the fourth course of rituximab combined with a small dose of melphalan produced excellent results and the complete response continued for more than 15 months. It is possible that these two drugs may act synergistically.

The synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid induces caspase-dependent and -independent apoptosis in acute myelogenous leukemia

In acute myeloid leukemia (AML), resistance to chemotherapy is associated with defects in both the extrinsic and intrinsic pathways of apoptosis. Novel agents that activate endogenous apoptosis-inducing mechanisms directly may be potentially useful to overcome chemoresistance in AML. We examined the mechanisms of apoptosis induction by the novel synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) in AML cells. CDDO-induced apoptosis was associated with the loss of mitochondrial inner transmembrane potential, caspases activation, the translocation of apoptosis-inducing factor to the nucleus, and DNA fragmentation in AML cells. Apoptosis was equally evident in cells deficient in caspase-9 or caspase-8 after exposure to CDDO, suggesting caspase-independent cell death. The use of small interfering RNA to reduce the expression of apoptosis-inducing factor partially inhibited CDDO-induced apoptosis in AML cells. Cells overexpressing Bcl-2 were markedly resistant to CDDO-induced apoptosis. Moreover, CDDO promoted the release of cytochrome c from isolated mitochondria, suggesting that CDDO targets the mitochondria directly to trigger the intrinsic pathway of cell death in intact cells. Together, these results suggest that CDDO functions by activating the intrinsic pathway of apoptosis and initiates caspase-dependent and independent cell death. The direct modulation of mitochondrial-mediated, caspase-independent apoptosis by CDDO may be advantageous for overcoming chemoresistance in AML.

JAK/STAT, Raf/MEK/ERK, PI3K/Akt and BCR-ABL in cell cycle progression and leukemogenesis

The roles of the JAK/STAT, Raf/MEK/ERK and PI3K/Akt signal transduction pathways and the BCR-ABL oncoprotein in leukemogenesis and their importance in the regulation of cell cycle progression and apoptosis are discussed in this review. These pathways have evolved regulatory proteins, which serve to limit their proliferative and antiapoptotic effects. Small molecular weight cell membrane-permeable drugs that target these pathways have been developed for leukemia therapy. One such example is imatinib mesylate, which targets the BCR-ABL kinase as well as a few structurally related kinases. This drug has proven to be effective in the treatment of CML patients. However, leukemic cells have evolved mechanisms to become resistant to this drug. A means to combat drug resistance is to target other prominent signaling components involved in the pathway or to inhibit BCR-ABL by other mechanisms. Treatment of imatinib-resistant leukemia cells with drugs that target Ras (farnysyl transferase inhibitors) or with the protein destabilizer geldanamycin has proven to be a means to inhibit the growth of resistant cells. This review will tie together three important signal transduction pathways involved in the regulation of hematopoietic cell growth and indicate how their expression is dysregulated by the BCR-ABL oncoprotein.

Anticancer therapy targeting the apoptotic pathway

Apoptosis, or programmed cell death, has an essential role in controlling cell number in many developmental and physiological settings and in chemotherapy-induced tumour-cell killing. It is a genetically regulated biological process, guided by the ratio of proapoptotic and antiapoptotic proteins. Recently, inducers of apoptosis have been used in cancer therapy. Several studies have attempted to induce apoptosis by triggering the tumour-necrosis-factor-related apoptosis-inducing ligand receptor and the BCL2 family of proteins, and others have targeted the caspases, and proteins that inhibit apoptosis. Most of these therapies are still in preclinical development because of their low efficacy and susceptibility to drug resistance, but some of them have shown promising results. In this article, we review the development and clinical efficacy of proapoptotic drugs that have shown promise.

Signal transduction mediated by the Ras/Raf/MEK/ERK pathway from cytokine receptors to transcription factors: potential targeting for therapeutic intervention

The Ras/Raf/Mitogen-activated protein kinase/ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) cascade couples signals from cell surface receptors to transcription factors, which regulate gene expression. Depending upon the stimulus and cell type, this pathway can transmit signals, which result in the prevention or induction of apoptosis or cell cycle progression. Thus, it is an appropriate pathway to target for therapeutic intervention. This pathway becomes more complex daily, as there are multiple members of the kinase and transcription factor families, which can be activated or inactivated by protein phosphorylation. The diversity of signals transduced by this pathway is increased, as different family members heterodimerize to transmit different signals. Furthermore, additional signal transduction pathways interact with the Raf/MEK/ERK pathway to regulate positively or negatively its activity, or to alter the phosphorylation status of downstream targets. Abnormal activation of this pathway occurs in leukemia because of mutations at Ras as well as genes in other pathways (eg PI3K, PTEN, Akt), which serve to regulate its activity. Dysregulation of this pathway can result in autocrine transformation of hematopoietic cells since cytokine genes such as interleukin-3 and granulocyte/macrophage colony-stimulating factor contain the transacting binding sites for the transcription factors regulated by this pathway. Inhibitors of Ras, Raf, MEK and some downstream targets have been developed and many are currently in clinical trials. This review will summarize our current understanding of the Ras/Raf/MEK/ERK signal transduction pathway and the downstream transcription factors. The prospects of targeting this pathway for therapeutic intervention in leukemia and other cancers will be evaluated.

Biology and management of AIDS-associated non-Hodgkin's lymphoma

The treatment of HIV-related lymphomas is evolving in the era of HAART. Standard-dose chemotherapy and dose-intensive therapies appear to be feasible. Whether outcomes are improved with combination chemotherapy and HAART remains unclear. Efforts aimed at developing pathogenic-based therapies will continue as the mechanisms of HIV lymphomagenesis are elucidated.

Novel triterpenoid CDDO-Me is a potent inducer of apoptosis and differentiation in acute myelogenous leukemia

It has been shown that the novel synthetic triterpenoid CDDO inhibits proliferation and induces differentiation and apoptosis in myeloid leukemia cells. In the current study the effects of the C-28 methyl ester of CDDO, CDDO-Me, were analyzed on cell growth and apoptosis of leukemic cell lines and primary acute myelogenous leukemia (AML). CDDO-Me decreased the viability of leukemic cell lines, including multidrug resistant (MDR)-1-overexpressing, p53(null) HL-60-Dox and of primary AML cells, and it was 3- to 5-fold more active than CDDO. CDDO-Me induced a loss of mitochondrial membrane potential, induction of caspase-3 cleavage, increase in annexin V binding and DNA fragmentation, suggesting the induction of apoptosis. CDDO-Me induced pro-apoptotic Bax protein that preceded caspase activation. Furthermore, CDDO-Me inhibited the activation of ERK1/2, as determined by the inhibition of mitochondrial ERK1/2 phosphorylation, and it blocked Bcl-2 phosphorylation, rendering Bcl-2 less anti-apoptotic. CDDO-Me induced granulo-monocytic differentiation in HL-60 cells and monocytic differentiation in primary cells. Of significance, colony formation of AML progenitors was significantly inhibited in a dose-dependent fashion, whereas normal CD34(+) progenitor cells were less affected. Combinations with ATRA or the RXR-specific ligand LG100268 enhanced the effects of CDDO-Me on cell viability and terminal differentiation of myeloid leukemic cell lines. In conclusion, CDDO-Me is an MDR-1- and a p53-independent compound that exerts strong antiproliferative, apoptotic, and differentiating effects in myeloid leukemic cell lines and in primary AML samples when given in submicromolar concentrations. Differential effects of CDDO-Me on leukemic and normal progenitor cells suggest that CDDO-Me has potential as a novel compound in the treatment of hematologic malignancies.