Mutational and transcriptional landscape of pediatric B-cell precursor lymphoblastic lymphoma.

ABSTRACT: Pediatric B-cell precursor (BCP) lymphoblastic malignancies are neoplasms with manifestation either in the bone marrow or blood (BCP acute lymphoblastic leukemia [BCP-ALL]) or are less common in extramedullary tissue (BCP lymphoblastic lymphoma [BCP-LBL]). Although both presentations are similar in morphology and immunophenotype, molecular studies have been virtually restricted to BCP-ALL so far. The lack of molecular studies on BCP-LBL is due to its rarity and restriction on small, mostly formalin-fixed paraffin-embedded (FFPE) tissues. Here, to our knowledge, we present the first comprehensive mutational and transcriptional analysis of what we consider the largest BCP-LBL cohort described to date (n = 97). Whole-exome sequencing indicated a mutational spectrum of BCP-LBL, strikingly similar to that found in BCP-ALL. However, epigenetic modifiers were more frequently mutated in BCP-LBL, whereas BCP-ALL was more frequently affected by mutation in genes involved in B-cell development. Integrating copy number alterations, somatic mutations, and gene expression by RNA sequencing revealed that virtually all molecular subtypes originally defined in BCP-ALL are present in BCP-LBL, with only 7% of lymphomas that were not assigned to a subtype. Similar to BCP-ALL, the most frequent subtypes of BCP-LBL were high hyperdiploidy and ETV6::RUNX1. Tyrosine kinase/cytokine receptor rearrangements were detected in 7% of BCP-LBL. These results indicate that genetic subtypes can be identified in BCP-LBL using next-generation sequencing, even in FFPE tissue, and may be relevant to guide treatment.

Genetic mechanisms underlying increased microalgal thermotolerance, maximal growth rate, and yield on light following adaptive laboratory evolution.

BACKGROUND: Adaptive laboratory evolution (ALE) is a powerful method for strain optimization towards abiotic stress factors and for identifying adaptation mechanisms. In this study, the green microalga Picochlorum sp. BPE23 was cultured under supra-optimal temperature to force genetic adaptation. The robustness and adaptive capacity of Picochlorum strains turned them into an emerging model for evolutionary studies on abiotic stressors such as temperature, salinity, and light. RESULTS: Mutant strains showed an expanded maximal growth temperature of 44.6 °C, whereas the maximal growth temperature of the wild-type strain was 42 °C. Moreover, at the optimal growth temperature of 38 °C, the biomass yield on light was 22.3% higher, and the maximal growth rate was 70.5% higher than the wild type. Genome sequencing and transcriptome analysis were performed to elucidate the mechanisms behind the improved phenotype. A de novo assembled phased reference genome allowed the identification of 21 genic mutations involved in various processes. Moreover, approximately half of the genome contigs were found to be duplicated or even triplicated in all mutants, suggesting a causal role in adaptation. CONCLUSIONS: The developed tools and mutant strains provide a strong framework from whereupon Picochlorum sp. BPE23 can be further developed. Moreover, the extensive strain characterization provides evidence of how microalgae evolve to supra-optimal temperature and to photobioreactor growth conditions. With this study, microalgal evolutionary mechanisms were identified by combining ALE with genome sequencing.

NOTCH1 fusions in pediatric T-cell lymphoblastic lymphoma: A high-risk subgroup with CCL17 (TARC) levels as diagnostic biomarker.

Twenty percent of children with T-cell lymphoblastic lymphoma (T-LBL) will relapse and have an extremely poor outcome. Currently, we can identify a genetically low-risk subgroup in pediatric T-LBL, yet these high-risk patients who need intensified or alternative treatment options remain undetected. Therefore, there is an urgent need to recognize these high-risk T-LBL patients through identification of molecular characteristics and biomarkers. By using RNA sequencing which was performed in 29/49 T-LBL patients who were diagnosed in the Princess Maxima Center for Pediatric Oncology between 2018 and 2023, we discovered a previously unknown high-risk biological subgroup of children with T-LBL. This subgroup is characterized by NOTCH1 gene fusions, found in 21% of our T-LBL cohort (6/29). All patients presented with a large mediastinal mass, pleural/pericardial effusions, and absence of blasts in the bone marrow, blood, and central nervous system. Blood CCL17 (C-C Motif Chemokine Ligand 17, TARC) levels were measured at diagnosis in 26/29 patients, and all six patients with NOTCH1 gene fusions patients exclusively expressed highly elevated blood CCL17 levels, defining a novel and previously not known clinically relevant biomarker for T-cell lymphoblastic lymphoma. Four out of these six patients relapsed during therapy, a fifth developed a therapy-related acute myeloid leukemia during maintenance therapy. These data indicate that T-LBL patients with a NOTCH1 fusion have a high risk of relapse which can be easily identified using a blood CCL17 screening at diagnosis. Further molecular characterization through NOTCH1 gene fusion analysis offers these patients the opportunity for treatment intensification or new treatment strategies.

Short-term physiologic response of the green microalga Picochlorum sp. (BPE23) to supra-optimal temperature.

Photobioreactors heat up significantly during the day due to irradiation by sunlight. High temperatures affect cell physiology negatively, causing reduced growth and productivity. To elucidate the microalgal response to stressful supra-optimal temperature, we studied the physiology of Picochlorum sp. (BPE23) after increasing the growth temperature from 30 °C to 42 °C, whereas 38 °C is its optimal growth temperature. Cell growth, cell composition and mRNA expression patterns were regularly analyzed for 120 h after increasing the temperature. The supra-optimal temperature caused cell cycle arrest for 8 h, with concomitant changes in metabolic activity. Accumulation of fatty acids was observed during this period to store unspent energy which was otherwise used for growth. In addition, the microalgae changed their pigment and fatty acid composition. For example, palmitic acid (C16:0) content in the polar fatty acid fraction increased by 30%, hypothetically to reduce membrane fluidity to counteract the effect of increased temperature. After the relief of cell cycle arrest, the metabolic activity of Picochlorum sp. (BPE23) reduced significantly over time. A strong response in gene expression was observed directly after the increase in temperature, which was dampened in the remainder of the experiment. mRNA expression levels associated with pathways associated with genes acting in photosynthesis, carbon fixation, ribosome, citrate cycle, and biosynthesis of metabolites and amino acids were downregulated, whereas the proteasome, autophagy and endocytosis were upregulated.