Autophagy and oxidative stress modulation mediate Bortezomib resistance in prostate cancer.

Proteasome inhibitors such as Bortezomib represent an established type of targeted treatment for several types of hematological malignancies, including multiple myeloma, Waldenstrom's macroglobulinemia, and mantle cell lymphoma, based on the cancer cell's susceptibility to impairment of the proteasome-ubiquitin system. However, a major problem limiting their efficacy is the emergence of resistance. Their application to solid tumors is currently being studied, while simultaneously, a wide spectrum of hematological cancers, such as Myelodysplastic Syndromes show minimal or no response to Bortezomib treatment. In this study, we utilize the prostate cancer cell line DU-145 to establish a model of Bortezomib resistance, studying the underlying mechanisms. Evaluating the resulting resistant cell line, we observed restoration of proteasome chymotrypsin-like activity, regardless of drug presence, an induction of pro-survival pathways, and the substitution of the Ubiquitin-Proteasome System role in proteostasis by induction of autophagy. Finally, an estimation of the oxidative condition of the cells indicated that the resistant clones reduce the generation of reactive oxygen species induced by Bortezomib to levels even lower than those induced in non-resistant cells. Our findings highlight the role of autophagy and oxidative stress regulation in Bortezomib resistance and elucidate key proteins of signaling pathways as potential pharmaceutical targets, which could increase the efficiency of proteasome-targeting therapies, thus expanding the group of molecular targets for neoplastic disorders.

Poly-Unsaturated Fatty Acids (PUFAs) from Cunninghamella elegans Grown on Glycerol Induce Cell Death and Increase Intracellular Reactive Oxygen Species.

Cunninghamella elegans NRRL-1393 is an oleaginous fungus able to synthesize and accumulate unsaturated fatty acids, amongst which the bioactive gamma-linolenic acid (GLA) has potential anti-cancer activities. C. elegans was cultured in shake-flask nitrogen-limited media with either glycerol or glucose (both at ≈60 g/L) employed as the sole substrate. The assimilation rate of both substrates was similar, as the total biomass production reached 13.0-13.5 g/L, c. 350 h after inoculation (for both instances, c. 27-29 g/L of substrate were consumed). Lipid production was slightly higher on glycerol-based media, compared to the growth on glucose (≈8.4 g/L vs. ≈7.0 g/L). Lipids from C. elegans grown on glycerol, containing c. 9.5% w/w of GLA, were transformed into fatty acid lithium salts (FALS), and their effects were assessed on both human normal and cancerous cell lines. The FALS exhibited cytotoxic effects within a 48 h interval with an IC50 of about 60 µg/mL. Additionally, a suppression of migration was shown, as a significant elevation of oxidative stress levels, and the induction of cell death. Elementary differences between normal and cancer cells were not shown, indicating a generic mode of action; however, oxidative stress level augmentation may increase susceptibility to anticancer drugs, improving chemotherapy effectiveness.

Lower-Risk Myelodysplastic Syndrome (MDS) Patients Exhibit Diminished Proteasome Proteolytic Activity and High Intracellular Reactive Oxygen Species (ROS) Levels.

Myelodysplastic syndromes (MDS) constitute a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis and an elevated risk of transformation to acute myeloid leukemia (AML). Available disease-modifying treatment approaches are limited. The ineffectiveness of proteasome inhibitors (PIs) in MDS patients is currently investigated, although it is unclear whether they rapidly develop resistance to PIs or whether proteasome proteolytic activity (PPA) is constitutively lower in the hematopoietic cells of these patients, thus limiting treatment effectiveness. We investigated 20 patients with MDS, categorized according to the International Prognostic Scoring System (IPSS) into a lower- or a higher-risk group. Peripheral blood mononuclear cells, bone marrow mononuclear cells, and cluster of differentiation 34-positive (CD34+) cells were isolated and assessed for the chymotrypsin-like activity of the proteasome and ß5 subunit accumulation. Additionally, intracellular reactive oxygen species (ROS) generation was screened. The lower-risk patient group (n=10) exhibited significantly lower proteasome activity (p<0.001) compared to both the higher-risk group (n=10) and healthy subjects (n=10). Furthermore, the lower-risk group had elevated oxidative stress levels (p<0.0001) and reduced ß5 subunit expression (p=0.0286). Both parameters were shown to be associated with transfusion dependency, since transfusion-dependent patients (n=5 in each subgroup) had decreased proteasome activity and simultaneously exhibited higher ROS levels. Our results indicate that reduced ß5 expression might potentially explain PIs' ineffectiveness in lower-risk MDS, elucidating the importance of the risk group in the selection of the proper treatment algorithm.

High Frequency of Post-Transfusion Microchimerism Among Multi-Transfused Beta-Thalassemic Patients.

BACKGROUND: Transfusion-associated microchimerism implies the presence of allogeneic hematopoietic cells in an individual, following the transfusion of a blood product. It is a transfusion-related adverse effect/long-term consequence, which has not been well-investigated among regularly transfused patients with thalassemia. PATIENTS AND METHODS: We investigated 64 regularly transfused, homozygous ß-thalassemic patients and 21 never-transfused healthy volunteer blood donors (controls) for the presence of microchimerism in their sera, using real-time PCR targeting circulating allogeneic, both, Human Leukocyte Antigen-DR isotype (HLA-DR) and non-HLA alleles. The investigation was longitudinally repeated in patient subsets for more than 2 years. Results were correlated with clinical and laboratory parameters, peripheral blood lymphocyte immunophenotype, blood storage time, and donor's gender to identify potential contributing factors for microchimerism generation. RESULTS: Overall, microchimerism was detected in 52 of the 64 patients (81.2%) and in 6 of the 21 controls (28.5%, p = 0.0001). Forty-four patients (68.7%) exhibited long-term microchimerism (persisted for more than 6 months), confirmed at all time-points investigated. Microchimerism was more frequent among elderly, women, splenectomized and more heavily transfused patients, and among those who exhibit higher serum ferritin levels. In these patients, a distinct descending pattern of CD16dim+CD56dim+ natural killer (NK)-cells (p < 0.001) and an ascending pattern of CD4+CD25brightCD127- regulatory T-cells (p = 0.022) for increasing allelic burden were noticed, suggesting the establishment of recipient immune tolerance against the donor-derived chimeric alleles. Both splenectomized and non-splenectomized thalassemic patients exhibited the same trend. The storage time of transfused blood products and donor/gender mismatch had no impact on the development of microchimerism. DISCUSSION-CONCLUSIVE REMARKS: Transfusion-associated microchimerism appears to be a very common complication among multi-transfused thalassemic patients. The potential clinical consequences of this phenomenon remain as yet unclear. Immune tolerance attributed to disease itself and to repeated transfusions might at least in part explain its appearance.