Effects of a novel proteasome inhibitor BU-32 on multiple myeloma cells

Diagnosis, treatment, and genetic characteristics of blastic plasmacytoid dendritic cell neoplasm: A review

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a highly aggressive and extremely rare hematologic disease with a poor prognosis, involving mainly the skin and bone marrow. The immunophenotype of these tumor cells is characterized by the expression of CD4, CD56, CD123, TCL-1, and CD303. To date, no consensus has been reached on the standard of care for BPDCN. Currently, clinical treatment is mainly based on high-dose chemotherapy combined with hematopoietic stem cell transplantation. However, this treatment method has limitations for elderly, frail, and relapsed/refractory patients. In recent years, breakthroughs in molecular biology and genetics have not only provided new ideas for the diagnosis of BPDCN but also helped develop targeted treatment strategies for this disease. The emergence of targeted drugs has filled the gap left by traditional therapies and shown great clinical promise. This article focuses on the latest advances in genetics and targeted therapies for BPDCN, especially the emerging therapies that may provide new ideas for the clinical treatment of BPDCN.

HCMV-Mediated Interference of Bortezomib-Induced Apoptosis in Colon Carcinoma Cell Line Caco-2

Human cytomegalovirus (HCMV) has been implicated in the development of human malignancies, for instance in colon cancer. Proteasome inhibitors were developed for cancer therapy and have also been shown to influence HCMV infection. The aim of this study was to investigate if proteasome inhibitors have therapeutic potential for colon carcinoma and how this is influenced by HCMV infection. We show by immunofluorescence and flow cytometry that the colon carcinoma cell line Caco-2 is susceptible to HCMV infection. Growth curve analysis as well as protein expression kinetics and quantitative genome analysis further confirm these results. HCMV has an anti-apoptotic effect on Caco-2 cells by inhibiting very early events of the apoptosis cascade. Further investigations showed that HCMV stabilizes the membrane potential of the mitochondria, which is typically lost very early during apoptosis. This stabilization is resistant to proteasome inhibitor Bortezomib treatment, allowing HCMV-infected cells to survive apoptotic signals. Our findings indicate a possible role of proteasome inhibitors in colon carcinoma therapy.

In vitro and in vivo efficacy of the novel oral proteasome inhibitor NNU546 in multiple myeloma

Proteasome inhibition demonstrates highly effective impact on multiple myeloma (MM) treatment. Here, we aimed to examine anti-tumor efficiency and underlying mechanisms of a novel well tolerated orally applicable proteasome inhibitor NNU546 and its hydrolyzed pharmacologically active form NNU219. NNU219 showed more selective inhibition to proteasome catalytic subunits and less off-target effect than bortezomib ex vivo. Moreover, intravenous and oral administration of either NNU219 or NNU546 led to more sustained pharmacodynamic inhibitions of proteasome activities compared with bortezomib. Importantly, NNU219 exhibited potential anti-MM activity in both MM cell lines and primary samples in vitro. The anti-MM activity of NNU219 was associated with induction of G2/M-phase arrest and apoptosis via activation of the caspase cascade and endoplasmic reticulum stress response. Significant growth-inhibitory effects of NNU219 and NNU546 were observed in 3 different human MM xenograft mouse models. Furthermore, such observation was even found in the presence of a bone marrow microenvironment. Taken together, these findings provided the basis for clinical trial of NNU546 to determine its potential as a candidate for MM treatment.

Anti-VEGF Drugs in the Treatment of Multiple Myeloma Patients

The interaction between the bone marrow microenvironment and plasma cells plays an essential role in multiple myeloma progression and drug resistance. The vascular endothelial growth factor (VEGF)/VEGF receptor (VEGFR) pathway in vascular endothelial cells activates and promotes angiogenesis. Moreover, VEGF activates and promotes vasculogenesis and vasculogenic mimicry when it interacts with VEGF receptors expressed in precursor cells and inflammatory cells, respectively. In myeloma bone marrow, VEGF and VEGF receptor expression are upregulated and hyperactive in the stromal and tumor cells. It has been demonstrated that several antiangiogenic agents can effectively target VEGF-related pathways in the preclinical phase. However, they are not successful in treating multiple myeloma, probably due to the vicarious action of other cytokines and signaling pathways. Thus, the simultaneous blocking of multiple cytokine pathways, including the VEGF/VEGFR pathway, may represent a valid strategy to treat multiple myeloma. This review aims to summarize recent advances in understanding the role of the VEGF/VEGFR pathway in multiple myeloma, and mainly focuses on the transcription pathway and on strategies that target this pathway.

Proteostasis In The Endoplasmic Reticulum: Road to Cure

The endoplasmic reticulum (ER) is an interconnected organelle that is responsible for the biosynthesis, folding, maturation, stabilization, and trafficking of transmembrane and secretory proteins. Therefore, cells evolve protein quality-control equipment of the ER to ensure protein homeostasis, also termed proteostasis. However, disruption in the folding capacity of the ER caused by a large variety of pathophysiological insults leads to the accumulation of unfolded or misfolded proteins in this organelle, known as ER stress. Upon ER stress, unfolded protein response (UPR) of the ER is activated, integrates ER stress signals, and transduces the integrated signals to relive ER stress, thereby leading to the re-establishment of proteostasis. Intriguingly, severe and persistent ER stress and the subsequently sustained unfolded protein response (UPR) are closely associated with tumor development, angiogenesis, aggressiveness, immunosuppression, and therapeutic response of cancer. Additionally, the UPR interconnects various processes in and around the tumor microenvironment. Therefore, it has begun to be delineated that pharmacologically and genetically manipulating strategies directed to target the UPR of the ER might exhibit positive clinical outcome in cancer. In the present review, we summarize recent advances in our understanding of the UPR of the ER and the UPR of the ER-mitochondria interconnection. We also highlight new insights into how the UPR of the ER in response to pathophysiological perturbations is implicated in the pathogenesis of cancer. We provide the concept to target the UPR of the ER, eventually discussing the potential of therapeutic interventions for targeting the UPR of the ER for cancer treatment.

The evaluation of the anti-cancer activity of ixazomib on Caco2 colon solid tumor cells, comparison with bortezomib

Proteasome inhibition has recently emerged as a clinically effective anticancer therapeutic approach. The first proteasome inhibitor, bortezomib (Velcade, PS-341), and new proteasome inhibitors including ixazomib have become more important in the development of targeted cancer therapies. Under physiological conditions, MLN9708 (ixazomib citrate), the stable citrate ester drug substance, hydrolyzes rapidly to MLN2238 (ixazomib), the biologically active boronic acid. It is a second-generation proteasome inhibitor, similar to the well-known proteasome inhibitor bortezomib, which is currently being investigated in phase 3 trials as a treatment for multiple Myeloma. Despite the proven efficacy of these drugs in hematologic malignancies, clinical activity is limited to solid tumors such as colon adenocarcinoma. This study is the first to investigate and compare the antiproliferative and apoptotic effects of MLN2238 and bortezomib on human colon adenocarcinoma Caco2 cells. The antiproliferative effects of MLN2238 and bortezomib were determined using WST-1; apoptotic effects of this drug were determined by caspase-3 and a mitochondrial membrane potential (JC-1) activity assay. Expression levels associated with proteasome inhibition and apoptosis of NF-κB and c-myc mRNA were evaluated by RT-PCR. At 24 and 48 h, MLN2238 showed significant time- and concentration-dependent antiproliferative and apoptotic effects on Caco2 cells. Depending on increasing mitochondrial depolarization and caspase-3 activation, MLN2238 induced apoptosis at level similar to that of bortezomib. In addition, MLN2238 downregulated NF-κB and c-myc mRNA expression levels. For the first time, MLN2238 was shown to induce antiproliferative and apoptotic effects on human colon adenocarcinoma cells that are comparable with those of bortezomib; these in vitro data in Caco2 cells support the development of MLN2238 for colon cancer.

Bortezomib as a new therapeutic approach for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm is an aggressive hematologic malignancy with a poor prognosis. No consensus regarding optimal treatment modalities is currently available. Targeting the nuclear factor-kappa B pathway is considered a promising approach since blastic plasmacytoid dendritic cell neoplasm has been reported to exhibit constitutive activation of this pathway. Moreover, nuclear factor-kappa B inhibition in blastic plasmacytoid dendritic cell neoplasm cell lines, achieved using either an experimental specific inhibitor JSH23 or the clinical drug bortezomib, interferes in vitro with leukemic cell proliferation and survival. Here we extended these data by showing that primary blastic plasmacytoid dendritic cell neoplasm cells from seven patients were sensitive to bortezomib-induced cell death. We confirmed that bortezomib efficiently inhibits the phosphorylation of the RelA nuclear factor-kappa B subunit in blastic plasmacytoid dendritic cell neoplasm cell lines and primary cells from patients in vitro and in vivo in a mouse model. We then demonstrated that bortezomib can be associated with other drugs used in different chemotherapy regimens to improve its impact on leukemic cell death. Indeed, when primary blastic plasmacytoid dendritic cell neoplasm cells from a patient were grafted into mice, bortezomib treatment significantly increased the animals’ survival, and was associated with a significant decrease of circulating leukemic cells and RelA nuclear factor-kappa B subunit expression. Overall, our results provide a rationale for the use of bortezomib in combination with other chemotherapy for the treatment of patients with blastic plasmacytoid dendritic cell neoplasm. Based on our data, a prospective clinical trial combining proteasome inhibitor with classical drugs could be envisaged.