PAX3-FOXO1 fusion

We additionally show that, in some FP-RMS, KDM3A also increases PAX3-FOXO1 levels. Together, our studies illuminate mechanisms of action of the KDM3A/ETS1 regulatory module, and reveal novel targetable mechanisms of PAX3-FOXO1 chromatin complex regulation, in FP-RMS.

However, oncogenic fusions involving transcription factors such as PAX3-FOXO1 in alveolar fusion gene-positive rhabdomyosarcoma (FP-RMS) have been difficult to inhibit due to the apparent lack of tractable drug-like binding sites comparable to that recognized by Gleevec (imatinib mesylate) on the BCR-ABL1 tyrosine kinase fusion protein...To facilitate single-cell clonal isolation of knock-ins, the homology-directed repair template encoding HiBiT was followed by a P2A self-cleaving peptide for coexpression of an mCherry fluorescent protein as a fluorescence-activated cell sorter (FACS)-selectable marker. HiBiT tagging thus allows highly sensitive luminescence detection of endogenous PAX3-FOXO1 levels permitting quantitative high-throughput screening of large compound libraries for the discovery of PAX3-FOXO1 inhibitors and degraders.

These tumours have significant local recurrence rates but lack metastatic potential. Here, we report a case of BSNS with PAX3/FOXO1 fusion and discuss its clinicopathological features and differential diagnosis.

Thus, we report KDM inhibitors P3FI-63 and P3FI-90 with the highest specificity for KDM3B. Their potent suppression of PAX3-FOXO1 activity indicates a possible therapeutic approach for FP-RMS and other transcriptionally addicted cancers.

In the absence of CBP/p300, Pol2 long range enhancer loops collapse, Pol2 accumulates in CpG islands and fails to exit the gene body. These results reveal a potential novel axis for therapeutic interference with P3F in aRMS and clarify the molecular relationship of P3F and CBP/p300 in sustaining active Pol2 clusters essential for oncogenic transcription.

We show that NF-Y occupies CCAAT motifs present upstream of PAX3 to function as a transcriptional activator of PAX3-FOXO1 expression in RMS. These findings reveal a critical upstream role of NF-Y in the oncogenic PAX3-FOXO1 pathway, highlighting how a broadly essential transcription factor can perform tumor-specific roles in governing cellular state.

MRI was performed at every stage of diagnosis and treatment as well as during follow-up. It allowed for staging, monitoring of chemotherapy, and guided surgery.

Moreover, we provide evidence that the combination of futibatinib with currently used chemotherapies such as irinotecan and vincristine has a synergistic effect against RMS in vitro. Moreover, limited efficacy is only observed in a PAX3-FOXO1 fusion-negative (FN) RMS cell line with mutationally activated FGFR4, whereas little or no efficacy is observed in PAX3-FOXO1 fusion-positive (FP) RMS cell lines with FGFR4 overexpression. Alternative treatment modalities such as combining futibatinib with other kinase inhibitors or targeting FGFR4 with CAR T cells or antibody-drug conjugate may be more effective than the approaches tested in this study.

Moreover, it is a great tool to identify novel fusion genes. Overall, it provides useful information for molecular pathological diagnosis and improves the diagnosis rate of STSs.

Objective: LX-101, a next-generation, targeted therapy directed to the insulin-like growth factor 1 receptor (IGF-1R), consists of a proprietary IGF-1 variant coupled to a cytotoxic methotrexate (MTX) payload. These results demonstrate that LX-101 has potent preclinical anti-tumor activity against pediatric sarcoma cell lines with well-established ties to the IGF-1R pathway, including with different oncogenic gene fusions. These data further support the clinical development of LX-101 in IGF-1R-related pediatric cancers. A clinical trial is planned.

She initiated chemotherapy with vincristine, actinomycin and cyclophosphamide with 4500 cGY radiation therapy per COG ARST0531 and was disease-free at therapy completion. This case suggests RMS may be a rare manifestation of Lynch syndrome and highlights the importance of long-term follow-up and germline assessment for predisposition syndromes in children with RMS. This abstract was supported by the Sohn Conference Foundation.

P1/2, N=23, Active, not recruiting, National Cancer Institute (NCI) | Suspended --> Active, not recruiting

The IC50 of futibatinib was ~500 nM for RMS559 and ~10 μM for RH4. Western blot showed that futibatinib inhibited FGFR4 phosphorylation in a dose dependent manner. The kinome activity assay found that futibatinib treatment resulted in SFK, AKT, and IGF1R activation.

To complement our zebrafish model, we are developing a double-inducible cell line model consisting of a tetracycline-inducible HES3 and a cumate-inducible PAX3-FOXO1 to further investigate the hypothesized cooperation between her3/HES3 and PAX3-FOXO1 in fusion-positive rhabdomyosarcoma. These two systems will allow us to elucidate conserved mechanisms of cooperation between HES3 and PAX3-FOXO1, and identify new therapeutic opportunities for children with fusion-driven rhabdomyosarcoma.

SynergyFinder found synergistic effects of enitociclib with irinotecan, carfilzomib, etoposide, bortezomib, selinexor or topotecan tested at clinically relevant concentrations in the aRMS cell line Rh41. Our results suggest that CDK9 inhibition is potentially clinically relevant for MYCN-amplified solid tumors such as aRMS and NBL due to its significant antitumor activity and pharmacologic targetability. The data provide essential information on the distinct targets, biomarkers of activity and clinically feasible drug combinations for the development of enitociclib in clinical trials addressing an unmet need in pediatric oncology.

P1/2, N=23, Suspended, National Cancer Institute (NCI) | Recruiting --> Suspended

At the population level, PAX3-FOXO1 was associated with a significant higher risk of death compared to PAX7-FOXO1-positive and PAX-FOXO1-negative tumors, and could explain poorer 5-year OS observed in adolescence population diagnosed with ARMS. A continuous risk score derived from the combination of clinical parameters with PAX3-FOXO1 fusion status represents a robust approach to improving current risk-adapted therapy for ARMS.

Thus, our results unveil a role for SMOX as inhibitor of tumorigenicity of FN-RMS cells in vitro. In conclusion, our in vitro results suggest that SMOX induction could be a potential combinatorial approach to sensitize FN-RMS to ionizing radiation and deserve further in-depth studies.

Lastly, a genome-wide CRISPR activation screen (CRISPRa) in combination with transcriptional analyses of ATR inhibitor resistant ARMS cells identifies the RAS-MAPK pathway and its targets, the FOS gene family, as inducers of resistance to ATR inhibition. Our findings provide a rationale for upcoming biomarker-driven clinical trials of ATR inhibitors in patients suffering from ARMS.

Combining KDM4 inhibition with cytotoxic chemotherapy led to tumor regression in preclinical PAX3-FOXO1 RMS subcutaneous xenograft models. In summary, we identified a targetable mechanism required for maintenance of the PAX3-FOXO1-related transcription factor network, which may translate to a therapeutic approach for fusion-positive RMS.

P1/2, N=23, Recruiting, National Cancer Institute (NCI) | Not yet recruiting --> Recruiting

Furthermore, knockdown of PAX3-FOXO1 or B7-H3 induced myogenin expression in all cell lines, although myosin heavy chain induction varied depending on the cellular context. Our results indicate that PAX3-FOXO1 regulates B7-H3 expression and that PAX3-FOXO1 and B7-H3 are commonly associated with multiple pathways related to an aggressive phenotype in ARMS, such as cell migration and myogenic differentiation block.

Cell-based screening of FGFR inhibitors with potential for clinical repurposing (NVP-BGJ398, nintedanib, dovitinib and ponatinib) revealed greater sensitivity of fusion-gene-positive versus -negative rhabdomyosarcoma cell lines and was shown to be correlated with high expression of FGFR2 and its specific ligand, FGF7. FGFR inhibition with NVP-BGJ398 reduced viability and was synergistic with SN-38, the active metabolite of irinotecan. In vivo, NVP-BGJ398 abrogated xenograft growth and warrants further investigation in combination with irinotecan as a therapeutic strategy for fusion-gene-positive rhabdomyosarcomas.

P1/2, N=23, Not yet recruiting, National Cancer Institute (NCI)