The 5q- Syndrome: Biology and Treatment

Molecular etiology of defective nuclear and mitochondrial ribosome biogenesis: Clinical phenotypes and therapy

Ribosomopathies are rare congenital disorders associated with defective ribosome biogenesis due to pathogenic variations in genes that encode proteins related to ribosome function and biogenesis. Defects in ribosome biogenesis result in a nucleolar stress response involving the TP53 tumor suppressor protein and impaired protein synthesis leading to a deregulated translational output. Despite the accepted notion that ribosomes are omnipresent and essential for all cells, most ribosomopathies show tissue-specific phenotypes affecting blood cells, hair, spleen, or skin. On the other hand, defects in mitochondrial ribosome biogenesis are associated with a range of clinical manifestations affecting more than one organ. Intriguingly, the deregulated ribosomal function is also a feature in several human malignancies with a selective upregulation or downregulation of specific ribosome components. Here, we highlight the clinical conditions associated with defective ribosome biogenesis in the nucleus and mitochondria with a description of the affected genes and the implicated pathways, along with a note on the treatment strategies currently available for these disorders.

Fungal Ribotoxins: A Review of Potential Biotechnological Applications

Fungi establish a complex network of biological interactions with other organisms in nature. In many cases, these involve the production of toxins for survival or colonization purposes. Among these toxins, ribotoxins stand out as promising candidates for their use in biotechnological applications. They constitute a group of highly specific extracellular ribonucleases that target a universally conserved sequence of RNA in the ribosome, the sarcin-ricin loop. The detailed molecular study of this family of toxic proteins over the past decades has highlighted their potential in applied research. Remarkable examples would be the recent studies in the field of cancer research with promising results involving ribotoxin-based immunotoxins. On the other hand, some ribotoxin-producer fungi have already been studied in the control of insect pests. The recent role of ribotoxins as insecticides could allow their employment in formulas and even as baculovirus-based biopesticides. Moreover, considering the important role of their target in the ribosome, they can be used as tools to study how ribosome biogenesis is regulated and, eventually, may contribute to a better understanding of some ribosomopathies.

Standardizing the initial evaluation for myelodysplastic syndromes

The myelodysplastic syndromes (MDS) pose a unique diagnostic challenge for clinicians and pathologists due to the clinicopathologic heterogeneity of the disease and overlapping features with other benign and malignant disorders. Currently, the initial evaluation of a patient with suspected MDS centers around a detailed medical history, review of the peripheral blood and bone marrow by an expert hematopathologist and risk stratification using laboratory results, morphology and cytogenetics. More sophisticated technologies, including multi-color flow cytometry, fluorescence in-situ hybridization (FISH), next-generation sequencing, and others are emerging and promise to offer significant refinements in diagnostic, prognostic and, hopefully, therapeutic information. With the incidence and prevalence of MDS increasing worldwide, it is critical for clinicians to optimize the initial evaluation of a patient with suspected disease, using a standard schema, to facilitate accurate diagnosis, risk stratification and treatment.

Myelodysplastic syndromes with 5q deletion: pathophysiology and role of lenalidomide

Myelodysplastic syndrome (MDS) is a hematopoietic stem cell disorder primarily affecting CD34+ cells, characterized by ineffective hematopoiesis, often transforming into acute myelogenous leukemia (AML). A subset of patients has 5q deletion (del(5q)) as the culprit pathogenetic trigger. Del(5q) affects critical regions 5q31 and 5q33, leading to gene haplodeficiency with subsequent RPS14 haplodeficiency and P53 activation. Subsequent to P53 activation, erythroid cell apoptosis and ineffective erythropoiesis occur. Other pathogenetic elements include protein phosphatase 2a and CDC25C haplodeficiency and decreased miR-145 and miR-146a expression. Lenalidomide is an immunomodulatory agent that selectively suppresses the del(5q) clone. While the mechanism is not fully understood, it is associated with diverse molecular changes including stabilization of MDM2 with subsequent enhanced P53 degradation. Lenalidomide showed success in low- and intermediate-1-risk MDS as reported in the 002, 003, and 004 trials. However, in higher-risk MDS, the results of lenalidomide monotherapy were modest, mandating the use of combination therapy. The role and priority of lenalidomide varies between different guidelines, and accordingly, future efforts are necessary to reach a unified therapeutic algorithm. TP53 mutations are important predictors of AML progression and possible resistance to lenalidomide. It is recommended to identify TP53 mutation early in the disease since it may change the decision regarding choice of therapy. Challenges with lenalidomide therapy remain the long-term effects and timing of its discontinuation.

Lenalidomide for myelodysplastic syndromes with del(5q): how long should it last?

Lenalidomide induces in patients with myelodysplastic syndrome (MDS) and del(5q) erythroid and cytogenetic response rates as high as 75% and 50%, respectively. It is still unclear, however, how long lenalidomide treatment should be continued and whether or not the drug could be interrupted. To assess the feasibility of lenalidomide discontinuation, we revised a cohort of 16 low-risk MDS patients with del(5q) treated at our institute in a phase II multicentric Italian study. Among the 12 responding patients, four discontinued lenalidomide while in complete response. All four patients needed during treatment a permanent lenalidomide reduction from 10 to 5 mg/day because of haematological toxicity (three patients) or grade 3 muscular and bone pain (one patient). At lenalidomide discontinuation after 16, 20, 27 and 20 months from the start, respectively, all four patients were in complete hematologic response and three forth in complete cytogenetic response. Three patients are still in response after 36, 30 and 20 months from lenalidomide discontinuation, respectively: The remaining patient relapsed after 20 months, and she is now receiving a new course of lenalidomide. In conclusion, long-lasting remissions are achievable in MDS patients with del(5q) in complete response after lenalidomide discontinuation.

Myelodysplastic syndromes: toward a risk-adapted treatment approach

Several classification and scoring systems have been developed in myelodysplastic syndromes (MDS to predict the risk of progression to acute myeloid leukemia and survival. These prognostication models have been also used to inform therapeutic decision-making in a risk-adapted fashion. Patient-related factors such as age, comorbidities, and functional status have to be considered as well. Here we review a risk-guided therapeutic approach for the management of MDS patients. It is anticipated that the improved understanding of the complex pathogenesis of MDS and the recent discovery of important molecular lesions will be translated into novel therapeutic approaches. Additionally, some prognostic aberrations are expected to be incorporated into the prognostic tools with the goal of improving their prognostic precision and therefore allow for a more informed therapeutic decision-making based on the individual's risk profile.

Current therapy of myelodysplastic syndromes

After being a neglected and poorly-understood disorder for many years, there has been a recent explosion of data regarding the complex pathogenesis of myelodysplastic syndromes (MDS). On the therapeutic front, the approval of azacitidine, decitabine, and lenalidomide in the last decade was a major breakthrough. Nonetheless, the responses to these agents are limited and most patients progress within 2 years. Allogeneic stem cell transplantation remains the only potentially curative therapy, but it is associated with significant toxicity and limited efficacy. Lack or loss of response after standard therapies is associated with dismal outcomes. Many unanswered questions remain regarding the optimal use of current therapies including patient selection, response prediction, therapy sequencing and combinations, and management of resistance. It is hoped that the improved understanding of the underpinnings of the complex mechanisms of pathogenesis will be translated into novel therapeutic approaches and better prognostic/predictive tools that would facilitate accurate risk-adaptive therapy.

Biological activity of lenalidomide in myelodysplastic syndromes with del5q: results of gene expression profiling from a multicenter phase II study

In vitro studies suggest that haploinsufficiency is involved in the pathogenesis of myelodysplastic syndromes (MDS). In patients with del5q cytogenetic abnormality, RPS-14 and microRNAs (miRNAs) play a major role. In a multicenter phase II single-arm trial with lenalidomide in anemic primary del5q MDS patients with low- or int-1 risk IPSS, biological changes from baseline were investigated. Gene expression profiling of selected genes was performed (TaqMan® Low Density Array Fluidic card, Applied Biosystems PRISM® 7900HT) and normalized against the expression of the 18S housekeeping gene from a pool of healthy subjects. Thirty-two patients were evaluated at baseline and after 3 and 6 months of treatment. RPS-14, miR-145, and miR-146 were downregulated at baseline and significantly increased during treatment. Nuclear factor kappa B, IL-6, interferon regulatory factor-1, IFNγ-R2, IL-2, and many genes in the apoptotic pathways (TNF, IL-1B, and IL-10) were upregulated at baseline and significantly downregulated during lenalidomide treatment, while forkhead box P3, FAS, IFNγ, IL-12A, and IL-12B were downregulated at baseline and progressively upregulated during treatment. The crucial role of aberrant immunological pathways and haploinsufficiency in the pathogenesis of del5q MDS is confirmed in the present patient setting. Our results indicate that lenalidomide may act through defined immunological pathways in this condition.