PAX5 fusion

ELN-PAX5 interaction results in the decreased expression of LEF1, MB1, and BLNK, while PML-PAX5 is critical in the early stages of leukemia. PAX5 fusion genes prevent the transcription of the PAX5 gene, making it an essential target gene for the study of leukemia progression and the diagnosis of B-ALL.

Notably, ex vivo drug screening revealed sensitivity of IKZF1plus blasts for drugs active against Ph-like ALL such as Birinapant and histone deacetylase inhibitors. We provided data in a large setting of a rare condition (DS-ALL) supporting that these patients, not associated with other high-risk features, need tailored therapeutic strategies.

With novel gene fusions and uncovered associations between the dynamics of MRD decline, TP53 and RUNX1 high burden mutations in this real-world cohort, our dataset provides valuable, clinically relevant insights to the genomic and transcriptomic landscape of children diagnosed with ALL. Pediatric, ALL, Prognosis, Mutation analysis

PAX5 structural aberrations are common and important genetic events in B-ALL with various forms, including in- frame gene fusions, 3' deletion ( PAX5::ZCCHC7 ), and focal exon deletions. OGM combined with RNA-seq helps to decipher pathological PAX5 structural abnormalities. PAX5 structural abnormalities mostly occur in BCR::ABL1 - positive and BCR::ABL1 -like patients and are often associated with IK10.

PNMZL and PTFL are rare, indolent types of NHL in young adults; often resection alone is sufficient for long term cure. Recent case series support the occurrence of “overlapping” PNMZL and PTFL in some patients. MAP2K1 mutations have been found in significant numbers of both PNMZL and PTFL cases.

Moderate-intensity therapy, as used in the MLL-Baby protocol in infants with KMT2A-g BCP-ALL, yields results comparable to other infant studies. Patients with a slow multicolor flow cytometry (MFC)-MRD response should be subjected to advanced therapies, such as targeted or immunotherapies.

Performing an ex-vivo drug screening with 174 drugs in early to late clinical trials on blasts of 3 IKZF1plus DS-ALL patients and on 14 controls (5 B-cell lymphoblastoid cell lines, 3 PBMCs, 3 T-cells and 3 CD34+ cells, all derived from healthy donors) we observed the efficacy of drugs known to be effective in Ph-like patients such as Birinapant, a SMAC mimetic, and HDAC inhibitors...Ph-like signature and IKZF1 deletions were associated with poor outcome, with the risk of relapse further increased for IKZF1plus patients. These alterations characterize subgroups of DS-ALL patients who need tailored therapeutic strategies.

As previously showed by us, we demonstrated the efficacy of the LCK-inhibitor Nintedanib, as single agent or in combination with conventional chemotherapy, both ex-vivo and in a patient-derived xenograft model, showing a synergistic effect with dexamethasone...From the drug screening, we selected Dasatinib, Bosutinib and Foretinib, known to be among the top 10 most potent LCK ligands...This study provides new insights in the pathogenic mechanisms of poor risk Ph-like leukemia and identifies a potential novel therapy for targeting the PAX5t group. Moreover, in general this study opens the scenario to target LCK kinase activity in further BCP-ALL subgroups.

After 48h monotherapy treatment by CHZ868, we detected decreased cell viability (20-75% at IC50), which increased in the combination with dexamethasone...Importantly, combination of BIBF1120 and CHZ868 showed a synergistic effect (-45%, at IC50)...Indeed, active caspase 3 increased after ruxolitinib and chloroquine (autophagy inhibitor) combination (+20% vs ruxolitinib alone, p<0.01)...Instead, AT9283 (p<0.001 vs LCLs), Fedratinib (p<0.01 vs LCLs) and Gandotinib (p<0.05 vs LCLs) were found to be potent, specific, and non-toxic JAK2 inhibitors. Additionally, this extended screening led us to identify drugs, not belonging to JAK inhibitors, specific and non-toxic for rearranged JAK2 cohort, such as Birinapant (Smac mimetic), JQ1 (BRD4 inhibitor), Fludarabine (Chemotherapy) among the others. CHZ868 is a promising drug for the treatment of JAK2 fusions. Further studies will focus on effective and specific novel drugs found to be highly effective and specific on JAK2 rearrangements in BCP-ALL.

Clinical molecular testing in our cohort revealed these gene alterations mainly in pediatric patients and enabled diagnosis, prognosis, and risk stratification allowing the use of clinically actionable therapeutic targets in some cases. It also contributed toward a useful data set for further analysis and potential for novel drug development. Longer-term followup incorporating therapy and outcomes information would be valuable.

This study provides new insights in high-risk Ph-like leukaemia and identifies a potential therapy for targeting PAX5-fusion poor risk group.

In combination with dexamethasone, a further decrease of viability was observed...Importantly, combination of BIBF1120 and CHZ868 showed a synergistic effect (-45%, at IC50)...Indeed, active caspase 3 increased after ruxolitinib and chloroquine (autophagy inhibitor) combination(+20% vs ruxolitinib alone, p<0.01)...Conclusion CHZ868 is a promising drugfor the treatment of JAK2 fusionsBCP-ALL. Further studies will include combination with standard chemotherapy drugs, by reducing the intensity and toxicity of chemotherapy.

The identification of DUX4 -r, subgroup defining mutations and fusion partner genes demonstrates the value of NGS-based approaches. We have confirmed the good and poor prognostic associations of DUX4 -r and ABL-class fusions, respectively, and identified ETV6-RUNX1 -like subgroup to have a good prognosis.

While we could not find evidence for a nuclear role of Pax5-Jak2 as an epigenetic regulator, high levels of active phosphorylated STAT5 and increased expression of STAT5 target genes were seen in Pax5 B-ALL tumors, implying that nuclear Pax5-Jak2 phosphorylates STAT5. Together, these data reveal Pax5-Jak2 as an important nuclear driver of leukemogenesis by maintaining phosphorylated STAT5 levels in the nucleus.

In combination with dexamethasone, we assessed a further decrease of viability between 10 to 95%...Importantly, combination of BIBF1120 and CHZ868 showed a synergistic effect (-45%, at IC50)...Indeed, active caspase 3 increased when ruxolitinib was given in combination with chloroquine, an autophagy inhibitor (+20% vs ruxolitinib alone, p<0.01)...CHZ868 is a promising candidate for treatment of BCP-ALL carrying JAK2 fusions, showing high efficacy and specificity, both ex vivo and in vivo . Further studies will include combination with standard chemotherapy drugs with the aim to maintain its efficacy by reducing the intensity and toxicity of chemotherapy.

Importantly, the phosphorylation and pro-proliferative effect was blocked by the JAK1/2 inhibitor Ruxolitinib...To validate our result, we used 2-deoxy-D-glucose (2DG), a competitor of glucose which is a main substrate utilized in bioenergetics pathways of cancer cells...The oncogenic potential of cells harboring this fusion is likely driven by signaling pathway alterations and intensive metabolic changes with dependencies on sufficient energy substrate supply, a mechanism that could potentially be exploited in future therapeutical strategies. Support: AZV NV18–07-00129

These results reveal that PAX5-K220 certainly shares the character with other PAX5-related fusion proteins rather than other fusion proteins with tyrosine kinase activity identified in Ph-like ALL, and did not contribute to proliferation activity. Precise functional analysis of each differently partnered PAX5 fusion protein is warranted in the future for better understanding of PAX5-related translocations and their effects.

No abstract available