Oncogenic Fusion Genes Research Articles

Exploring the driver events of eccrine poromas and porocarcinomas: A retrospective, cross-institutional study of 54 cases.

We have comprehensively characterised the mutational landscape of eccrine poroma (EP) and eccine porocarcinoma (EPC), uncovering novel events and delineating different pathways of tumorigenesis underlying these tumours. EPs are driven largely by oncogenic fusion genes, whereas EPCs are driven largely by somatic mutations affecting various pathways, with a subset driven by fusion genes as the first oncogenic driver, and somatic mutations representing secondary events contributing to progression of the tumour. Fusion genes in EP predominantly involve YAP1 whereas those in EPC preferentially involve PAK gene family members.

Rare Oncogenic Fusions in Pediatric Central Nervous System Tumors: A Case Series and Literature Review

Background and Objectives: Central Nervous System (CNS) pediatric tumors represent the most common solid tumors in children with a wide variability in terms of survival and therapeutic response. By contrast to their adult counterpart, the mutational landscape of pediatric CNS tumors is characterized by oncogenic fusions rather than multiple mutated genes. CNS pediatric tumors associated with oncogenic fusions represent a complex landscape of tumors with wide radiological, morphological and clinical heterogeneity. In the fifth CNS WHO classification, there are few pediatric CNS tumors for which diagnosis is based on a single oncogenic fusion. This work aims to provide an overview of the impact of rare oncogenic fusions (NTRK, ROS, ALK, MET, FGFR, RAF, MN1, BCOR and CIC genes) on pathogenesis, histological phenotype, diagnostics and theranostics in pediatric CNS tumors. We report four cases of pediatric CNS tumors associated with NTRK (n = 2), ROS (n = 1) and FGFR3 (n = 1) oncogenic fusion genes as a proof of concept. Cases presentation and literature review: The literature review and the cohort that we described here underline that most of these rare oncogenic fusions are not specific to a single morpho-molecular entity. Even within tumors harboring the same oncogenic fusions, a wide range of morphological, molecular and epigenetic entities can be observed. Conclusions: These findings highlight the need for caution when applying the fifth CNS WHO classification, as the vast majority of these fusions are not yet incorporated in the diagnosis, including grade evaluation and DNA methylation classification.

Immuno-targeting the ectopic phosphorylation sites of PDGFRA generated by MAN2A1-FER fusion in HCC.

HCC is one of the most lethal cancers for humans. Mannosidase alpha class 2A member 1 (MAN2A1)-FER is one of the most frequent oncogenic fusion genes in HCC. In this report, we showed that MAN2A1-FER ectopically phosphorylated the extracellular domains of PDGFRA, MET, AXL, and N-cadherin. The ectopic phosphorylation of these transmembrane proteins led to the activation of their kinase activities and initiated the activation cascades of their downstream signaling molecules. A panel of mouse monoclonal antibodies was developed to recognize the ectopic phosphorylation sites of PDGFRA. The analyses showed that these antibodies bound to the specific phosphotyrosine epitopes in the extracellular domain of PDGFRA with high affinity and specificity. The treatment of MAN2A1-FER-positive cancer HUH7 with one of the antibodies called 2-3B-G8 led to the deactivation of cell growth signaling pathways and cell growth arrest while having minimal impact on HUH7ko cells where MAN2A1-FER expression was disrupted. The treatment of 2-3B-G8 antibody also led to a large number of cell deaths of MAN2A1-FER-positive cancer cells such as HUH7, HEPG2, SNU449, etc., while the same treatment had no impact on HUH7ko cells. When severe combined immunodeficiency mice xenografted with HEPG2 or HUH7 were treated with monomethyl auristatin E-conjugated 2-3B-G8 antibody, it slowed the progression of tumor growth, eliminated the metastasis, and reduced the mortality, in comparison with the controls. Targeting the cancer-specific ectopic phosphorylation sites of PDGFRA induced by MAN2A1-FER may hold promise as an effective treatment for liver cancer.

The landscape of cancer-associated transcript fusions in adult brain tumors: a longitudinal assessment in 140 patients with cerebral gliomas and brain metastases.

Oncogenic fusions of neurotrophic receptor tyrosine kinase NTRK1, NTRK2, or NTRK3 genes have been found in different types of solid tumors. The treatment of patients with TRK fusion cancer with a first-generation TRK inhibitor (such as larotrectinib or entrectinib) is associated with high response rates (>75%), regardless of tumor histology and presence of metastases. Due to the efficacy of TRK inhibitor therapy of larotrectinib and entrectinib, it is clinically important to identify patients accurately and efficiently with TRK fusion cancer. In this retrospective study, we provide unique data on the incidence of oncogenic NTRK gene fusions in patients with brain metastases (BM) and gliomas. 140 samples fixed and paraffin-embedded tissue (FFPE) of adult patients (59 of gliomas [17 of WHO grade II, 20 of WHO grade III and 22 glioblastomas] and 81 of brain metastasis (BM) of different primary tumors) are analyzed. Identification of NTRK gene fusions is performed using next-generation sequencing (NGS) technology using Focus RNA assay kit (Thermo Fisher Scientific). We identified an ETV6 (5)::NTRK3 (15) fusion event using targeted next-generation sequencing (NGS) in one of 59 glioma patient with oligodendroglioma-grade II, IDH-mutated and 1p19q co-deleted at incidence of 1.69%. Five additional patients harboring TMPRSS (2)::ERG (4) were identified in pancreatic carcinoma brain metastasis (BM), prostatic carcinoma BM, endometrium BM and oligodendroglioma (grade II), IDH-mutated and 1p19q co-deleted. A FGFR3 (17)::TACC3 (11) fusion was identified in one carcinoma breast BM. Aberrant splicing to produce EGFR exons 2-7 skipping mRNA, and MET exon 14 skipping mRNA were identified in glioblastoma and pancreas carcinoma BM, respectively. This study provides data on the incidence of NTRK gene fusions in brain tumors, which could strongly support the relevance of innovative clinical trials with specific targeted therapies (larotrectinib, entrectinib) in this population of patients. FGFR3 (17)::TACC3 (11) rearrangement was detected in breast carcinoma BM with the possibility of using some specific targeted therapies and TMPRSS (2)::ERG (4) rearrangements occur in a subset of patients with, prostatic carcinoma BM, endometrium BM, and oligodendroglioma (grade II), IDH-mutated and 1p19q co-deleted, where there are yet no approved ERG-directed therapies.

Gene expression landscape of cutaneous squamous cell carcinoma progression.

Cutaneous squamous cell carcinomas (cSCCs) are the second most common human cancer and have been characterized by RNA sequencing (RNA-Seq); however, the transferability of findings from individual studies may be limited by small sample sizes and diverse analysis protocols. To define the transcriptome landscape at different stages in the progression of normal skin to cSCC via a meta-analysis of publicly available RNA-Seq samples. Whole-transcriptome data from 73 clinically normal skin samples, 46 actinic keratoses (AK) samples, 16 in situ SCC samples, 13 keratoacanthoma (KA) samples and 147 cSCC samples [including 30 samples from immunocompromised patients and 8 from individuals with recessive dystrophic epidermolysis bullosa (RDEB)] were uniformly processed to harmonize gene expression. Differential expression, fusion detection and cell-type deconvolution analyses were performed. Individual RNA-Seq studies of cSCC demonstrated study-specific clustering and varied widely in their differential gene expression detection. Following batch correction, we defined a consensus set of differentially expressed genes (DEGs), including those altered in the preinvasive stages of cSCC development, and used single-cell RNA-Seq data to demonstrate that DEGs are often - but not always - expressed by tumour-specific keratinocytes (TSKs). Analysis of the cellular composition of cSCC, KA and RDEB-cSCC identified an increase in differentiated keratinocytes in KA, while RDEB-cSCC contained the most TSKs. Compared with cSCC arising in immunocompetent individuals, cSCC samples from immunosuppressed patients demonstrated fewer memory B cells and CD8+ T cells. A comprehensive and unbiased search for fusion transcripts in cSCC and intermediate disease stages identified few candidates that recurred in >1% of all specimens, suggesting that most cSCC are not driven by oncogenic gene fusions. Finally, using Genotype-Tissue Expression (GTEx) data, we distilled a novel 300-gene signature of chronic sun exposure that affirms greater cumulative ultraviolet (UV) exposure in later stages of cSCC development. Our results define the gene expression landscape of cSCC progression, characterize cell subpopulation heterogeneity in cSCC subtypes that contribute to their distinct clinical phenotypes, demonstrate that gene fusions are not a common cause of cSCC and identify UV-responsive genes associated with cSCC development.

Therapeutic strategy for targeting recurrent oncogenic kinase gene fusions in prostate cancer.

Therapeutic strategy for targeting recurrent oncogenic kinase gene fusions in prostate cancer.

Abstract 2853: Comparison of methods for detection of hemispheric gliomas of infancy and their characteristic oncogenic tyrosine kinase gene fusions

Abstract Introduction High grade hemispheric gliomas in infancy (IHG) are characterized by a more favorable outcome compared to high grade gliomas in older children. We have shown in previous studies that these tumors are characterized by a stable genome. The occurrence of tyrosine kinase gene fusions in high-grade hemispheric gliomas of infancy may represent therapeutic targets. Methods: 33 high-grade hemispheric gliomas occurring in children younger than three years were retrieved from the archives of the Brain Tumor Reference Center, Institute of Neuropathology, University of Bonn. DNA and RNA were extracted from FFPE tumor samples. Methylation-based classification was done by hybridization to Illumina methylation arrays and subsequent use of the Heidelberg brain tumor classifier versions v11b4, v12.5 and v12.8. In addition UMAP plots were used to visualize similarities of methylation profiles. Gene fusions were identified on the DNA level by FISH using break-apart probes for ALK, NTRK1, -2, -3, ROS1 and MET and Molecular Inversion Probe (MIP) methodology. On the RNA level, fusion transcripts were detected by targeted RNA sequencing as well as Nanostring assay with fusion-specific probes. Results: 32 IHG occurred in the first year of life, one at the age of two years. 23/33 IHG were classified as such by methylation arrays; 6 further cases could be annotated to the IHG group by UMAP plots. 18/33 cases (54.5 %) showed fusions of ALK to different partners; all occurred in the first year of life. Fusions of ROS1 were found in 4, MET in 2, NTRK1 and -3 in 7 cases. 2 cases showed no fusions. The different methods for fusion detection led to comparable results. Only recurrent fusions with known fusion partners were detectable with Nanostring probes designed for the fusion sequence, and library construction for targeted RNA sequencing was not successful in a fraction of cases. Break-apart FISH led to reliable results on the next day, and MIP technology represented the most sensitive method for analysis of FFPE samples. Conclusions: Gene fusions involving the tyrosine kinase genes ALK, MET, ROS1 and NTRK1 and -3 occurred in 93 % of high grade hemispheric gliomas of infancy; the most frequent were ALK fusions occurring in children younger than 1 year. DNA-based MIP technology represented the most robust and sensitive assay. A combination of RNA- and DNA-based methods to detect these fusions with high reliability is recommended. Citation Format: Torsten Pietsch, Gerrit Gielen, Andreas Waha, Evelyn Dörner, Verena Dreschmann, Christof Kramm, Christian Vokuhl. Comparison of methods for detection of hemispheric gliomas of infancy and their characteristic oncogenic tyrosine kinase gene fusions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2853.

Abstract 2147: Genetic ancestry associations with prostate adenocarcinoma mutational profiles: New Insights from a diverse 5,959-patient real-world cohort

Abstract In prostate cancer, Black men face higher incidence rates, more advanced diagnoses and worse outcomes than White men. These disparities partially stem from environmental, socioeconomic, and healthcare access factors. Recent data highlight racial differences in prostate cancer molecular profiles, with tumors from Black men showing increased SPOP and decreased PIK3CA mutations and amplified androgen receptor signaling and inflammatory pathway activations. Thus, somatic mutation patterns may also contribute to these disparities. We sought to identify associations of mutational profiles in prostate adenocarcinoma (PRAD) with genetic ancestry instead of race and ethnicity categories, analyzing a de-identified cohort of 5,959 patients who underwent the Tempus xT 648-gene NGS tumor profiling test. We used 654 ancestry-informative markers to estimate genetic ancestry by calculating similarity to reference populations for five regions: Africa (AFR), Americas (AMR), East Asia (EAS), Europe (EUR), and South Asia (SAS). Associations between genetic ancestry proportions and somatic variants were assessed for 67 PRAD-related genes using logistic regression models. Analyses included copy number alterations (CNAs), oncogenic gene fusions, small splice and non-synonymous mutations (NS), OncoKB L1/2 & R1, and small missense driver somatic mutations predicted with boostDM. Likelihood ratio tests were employed to compare models with and without ancestry terms. The Benjamini-Hochberg method was utilized to adjust p-values and control the FDR at 5%. We confirmed reported associations in PRAD between AFR ancestry and SPOP NS mutations (OR=1.03 per doubling of AFR ancestry proportion, p=0.03) and decreased AFR with PIK3CA OncoKB and driver mutations (OR=0.94, p=0.02), PTEN CNAs (OR=0.95, p=0.0001), and TMPRSS2-ERG fusions (OR=0.95, p<0.0001). However, we also observed negative associations between AFR and AR CNAs (OR=0.95, p=0.004), EAS and PTEN CNAs (OR=0.96, p=0.01), and EAS and TMPRSS2-ERG fusions (OR=0.97, p=0.02). Additionally, a negative association was found between EAS and TP53 driver NS mutations (OR=0.96, p=0.04), while positive associations with driver mutations in FOXA1 (OR=1.06, p=0.03) and NS mutations in the PI3K/AKT/mTOR pathway genes (OR=1.04, p=0.01) were noted. Lastly, we identified novel positive associations between AMR and driver mutations in PIK3C3A (OR=1.12, p=0.0003) as well as small NS mutations or CNAs in the PI3K/AKT/mTOR pathway genes (OR=1.03, p=0.04). By analyzing a large, diverse real-world cohort and leveraging NGS-inferred genetic ancestry, our study confirms known associations between somatic alterations in PRAD cancer genes and race and ethnicity, while unveiling novel associations in understudied populations of potential significance for understanding disparities in disease outcomes. Citation Format: Brooke Rhead, Yannick Pouliot, Francisco M. De La Vega, David W. Craig, John Carpten. Genetic ancestry associations with prostate adenocarcinoma mutational profiles: New Insights from a diverse 5,959-patient real-world cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2147.

Abstract 1089: Endogenous HiBiT-tagging of PAX3-FOXO1 reveals downregulation of the fusion oncogene by CDK inhibitors and has synergy with vincristine

Abstract Background: Oncogenic fusion genes are attractive therapeutic targets due to their tumor-specific expression and driver roles in cancers. PAX3-FOXO1 (P3F) is the dominant oncogenic driver of fusion-positive rhabdomyosarcoma (FP-RMS) with no current targeted therapy. We developed methods to directly measure endogenous P3F protein levels amenable to high-throughput drug screens. Method: HiBiT tag, an 11 amino acid peptide of NanoLuc luciferase, was inserted into the endogenous P3F using CRISPR in FP-RMS cell lines RH4 and SCMC. Western blot was used for HiBiT tag validation. RNA-seq and ChIP-seq were used to assess transcriptomics and DNA binding of HiBiT-tagged P3F (P3F-HiBiT). High-throughput drug screen using Nano-Glo luciferase assay was performed using the Mechanism Interrogation PlatE (MIPE 5.0) drug library, a 2,480 drug library with known mechanisms of action. CellTiter-Glo was used to monitor cell viability. Mouse xenograft models of FP-RMS were used to investigate in vivo efficacy. Results: We validated HiBiT tagging of P3F by Western. Both P3F-HiBiT and unmodified P3F activated the same gene sets in fibroblasts by RNA-seq Gene Set Enrichment Analysis (GSEA). ChIP-seq using HiBiT antibody for P3F-HiBiT matched the genomic locations from ChIP-seq with P3F antibody in RH4 and SCMC. Using a cutoff value of > 90 (Area Under the Curve (AUC) of CellTiter-Glo minus AUC of Nano-Glo), in both RH4 and SCMC, we identified 182 compounds which downregulate P3F before cell death. Filtering for drugs with ≥ 3 hits for the same target identified 14 drug classes that suppressed P3F including HDAC inhibitors (3), BRD4 inhibitors (3), and CDK inhibitors (8). FP-RMS was sensitive to CDK1/2, CDK4/6, CDK9, and multi-CDK inhibitors. A multi-CDK inhibitor TG02, currently in human trials, downregulated P3F and RNA-seq GSEA showed marked suppression of P3F targets. TG02 also significantly delayed tumor progression in mouse xenograft model of FP-RMS without weight loss. Interestingly, the commonly used chemotherapeutic Vincristine (VCR) also downregulated P3F in vitro. TG02 with VCR showed synergy by Loewe analysis. In vivo, testing showed significant delay in tumor progression by the combination compared to TG02 or VCR alone. Of note, tumor RNA-seq GSEA following treatment with TG02, or VCR alone, and in combination significantly downregulated P3F targets. Conclusion And Future Directions: By HiBiT tagging the fusion oncogene P3F, we identified 182 drugs that suppress P3F levels of which TG02 was a top hit. TG02 showed in vivo efficacy indicating that FP-RMS is susceptible to CDK inhibition. We also found synergy between TG02 and VCR, resulting in a significant delay in FP-RMS tumor progression compared to single agents. Interestingly, we found that VCR alone can downregulate P3F and its targets. Combination therapy of TG02 with VCR shows promise for clinical translation in FP-RMS. Citation Format: Yong Yean Kim, Katrina Jia, Mehal Churiwal, Teresa Hawley, Silvia Pomella, Christine Evans, Raj Chari, David Milewski, Ranuka Sinniah, Young Song, Hsien-Chao Chou, Xinyu Wen, Craig Thomas, Michele Ceribelli, Jun Wei, Robert Hawley, Javed Khan. Endogenous HiBiT-tagging of PAX3-FOXO1 reveals downregulation of the fusion oncogene by CDK inhibitors and has synergy with vincristine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1089.

Abstract 562: Frequent copy number gain of MCL1 is a therapeutic target for osteosarcoma

Abstract Osteosarcoma (OS) is the most common primary malignant bone tumor that predominantly occurs in children, adolescents, and young adults. The treatment for OS that combines surgery with chemotherapy, which consists of a four-drug combination of adriamycin (DOX), cisplatin (CDDP), high-dose methotrexate (MTX), and ifosfamide, was established in 1970s, and it is still used as a standard therapy. Oncogenic driver mutations and fusion genes common to OS have not been identified, which is one of the reasons for the lack of success in drug development for OS. Herein, to explore the characteristic vulnerability in OS, molecular targeted drugs were screened against OS cell lines and patient-derived cells; obatoclax, a pan-BH3 mimetic, and a concomitant drug that enhances obatoclax-induced apoptosis, OSI906, a dual inhibitor of IGF1R and IR, were found. Fluorescence in situ hybridization (FISH) analysis revealed that copy number gains of MCL1, an antiapoptotic Bcl-2 family protein, were observed in 46.3% of formalin-fixed paraffin-embedded (FFPE) specimens from patients with OS (N = 41) and in 45.5% of OS cell lines (N = 11), thereby causing vulnerability to BH3 mimetics. IHC staining also revealed high expression of Mcl-1 protein in specimens with MCL1-amplification in FISH analysis. Pharmacological or genetic inhibition of Mcl-1 induced potent apoptosis in MCL1-amplified OS cells, which was enhanced by the co-inhibition with Bcl-xL. Moreover, chromosome 1q21.2-3, where MCL1 is located, contains several IGF1R/PI3K pathway-related genes, including PIP5K1A, TARS2, OUTD7B, and ENSA, whose copy numbers were also increased in MCL1-amplified OS cells, suggesting that 1q21.2-3-amplified OS cells readily activate downstream pathways via IGF1R. IGF signaling activation in 1q21.2-3-amplified OS cells negated the obatoclax-induced apoptosis, which was overcome by OSI906 treatment. Combined obatoclax and OSI906 administration remarkably suppressed MCL1-amplified OS tumor growth in the xenograft mouse model and resulted in tumor regression; however, none of the treatments reduced tumor growth of OS without MCL1 amplification. These results suggest that combining obatoclax with OSI906 could be a potential therapeutic intervention for 1q21.2-3-amplified OS, and that prior stratification of OS based on the 1q21.2-3 amplification status would be important for the success of this combination therapy. Thus, we elucidated the mechanism of action of drugs and their potential as a novel therapeutic strategy for approximately 50% of patients with OS. Moreover, a FISH analysis that can detect copy number gains of MCL1 in FFPE specimens from patients with OS was established to stratify patients eligible for this therapy. Citation Format: Satoshi Takagi, Ryohei Katayama. Frequent copy number gain of MCL1 is a therapeutic target for osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 562.

Abstract 5954: Big data-driven discovery of novel oncogenic fusion genes for anticancer therapy

Abstract The integration of big data analytics with cancer research is catalyzing a transformative approach in cancer treatment, primarily focusing on the discovery of novel and efficacious anticancer targets. Our study presents an advanced algorithm, specifically crafted to exploit the extensive data available in the field of oncology. We started with the genomic and clinical information of 8,864 patients with 33 different cancers (TCGA). Then we implemented the following algorithm to discover anti-cancer targets by analyzing the clinical significance (cBioPortal), drug development status (Cortellis), and oncogenicity (DepMap) of candidate genes: Candidate genes = {gene | gene ∈ Genes, [Frequency(gene) > 50, Drug(gene) ∈ {'biological testing', 'preclinical stage'}, Association(gene) ≥ 0.4, Publication(gene) ≤ 200] ∨ [Publication(gene) ≥ 200 ∧ Boolean(gene)]}. We employed this algorithm to analyze fusion genes, which represent promising anti-cancer targets known for their potential to elicit substantial clinical responses, but there is a high demand for new ones. We identified four druggable therapeutic targets out of a total of 15,291 fusion genes through the algorithm: frame-shifted FGFR3-TACC3, in-framed DLK1-RPS11, frame-shifted CHP1-RAD51B, and in-framed TBC1D22A-SMYD3. We conducted in vitro validation studies of these fusion genes in NIH3T3 cell lines, and it confirmed that all of the fusion genes not only produce mRNA and protein levels but also induce oncogenic effects on cellular behavior. In the case of FGFR3-TACC3, the introduced fusion gene induced mRNA (p < 0.05) and protein expression (p < 0.05) even when frame-shifted. In addition, the proliferation rate of transformed cells increased more than 4-fold on day 10 (p < 0.0001) and colony formation increased more than 5-fold on day 21 (p < 0.01) compared to wild-type cells. These results demonstrate the tumorigenicity of the fusion genes. Taken together, this study emphasizes the crucial role of big data in propelling oncology research forward. The algorithm we developed can offer a new pathway for creating innovative cancer treatment, marking a significant advancement in the realm of personalized cancer therapy. Citation Format: Dooho Kim, Jong Woo Park, Jung-Ae Kim, Jeong-Hoon Kim, Tae Sub Park, Joonghoon Park. Big data-driven discovery of novel oncogenic fusion genes for anticancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5954.

Transforming Growth Factor Beta and Alveolar Rhabdomyosarcoma: A Challenge of Tumor Differentiation and Chemotherapy Response.

Alveolar rhabdomyosarcoma (ARMS), an invasive subtype of rhabdomyosarcoma (RMS), is associated with chromosomal translocation events resulting in one of two oncogenic fusion genes, PAX3-FOXO1 or PAX7-FOXO1. ARMS patients exhibit an overexpression of the pleiotropic cytokine transforming growth factor beta (TGF-β). This overexpression of TGF-β1 causes an increased expression of a downstream transcription factor called SNAIL, which promotes epithelial to mesenchymal transition (EMT). Overexpression of TGF-β also inhibits myogenic differentiation, making ARMS patients highly resistant to chemotherapy. In this review, we first describe different types of RMS and then focus on ARMS and the impact of TGF-β in this tumor type. We next highlight current chemotherapy strategies, including a combination of the FDA-approved drugs vincristine, actinomycin D, and cyclophosphamide (VAC); cabozantinib; bortezomib; vinorelbine; AZD 1775; and cisplatin. Lastly, we discuss chemotherapy agents that target the differentiation of tumor cells in ARMS, which include all-trans retinoic acid (ATRA) and 5-Azacytidine. Improving our understanding of the role of signaling pathways, such as TGF-β1, in the development of ARMS tumor cells differentiation will help inform more tailored drug administration in the future.

Transcriptome analysis of primary adult B-cell lineage acute lymphoblastic leukemia identifies pathogenic variants and gene fusions, and predicts subtypes for in depth molecular diagnosis.

B-cell acute lymphoblastic leukemia (B-ALL) is classified into subgroups based on known driver oncogenes and molecular lesions, including translocations and recurrent mutations. However, the current diagnostic tests do not identify subtypes or oncogenic lesions for all B-ALL samples, creating a heterogeneous B-ALL group of unknown subtypes. We sorted primary adult B-ALL cells and performed transcriptome analysis by bulk RNA sequencing (RNA-seq). Transcriptomic analysis of an adult B-ALL cohort allowed the classification of four patient samples with subtypes that were not previously revealed by standard gene panels. The leukemia of two patients were of the DUX4 subtype and two were CRLF2+ Ph-like B-ALL. Furthermore, single nucleotide variant analysis detected the oncogenic NRAS-G12D, KRAS-G12D, and KRAS-G13D mutations in three of the patient samples, presenting targetable mutations. Additional oncogenic variants and gene fusions were uncovered, as well as multiple variants in the PDE4DIP gene across five of the patient samples. We demonstrate that RNA-seq is an effective tool for precision medicine in B-ALL by providing comprehensive molecular profiling of leukemia cells, identifying subtype and oncogenic lesions, and stratifying patients for appropriate therapy.

CRISPR-Cas9-Mediated Bioluminescent Tagging of Endogenous Proteins by Fluorescent Protein-Assisted Cell Sorting.

Oncogenic fusion genes are attractive therapeutic targets because of their tumor-specific expression and central "driver" roles in various human cancers. 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. Toward the identification of novel small molecules that selectively target PAX3-FOXO1, we used CRISPR-Cas9-mediated knock-in to append the pro-luminescent HiBiT tag onto the carboxy terminus of the endogenous PAX3-FOXO1 fusion protein in two human FP-RMS cell lines (RH4 and SCMC). HiBiT is an 11-amino acid peptide derived from the NanoLuc luciferase that produces a luminescence signal which is ~100-fold brighter than firefly or Renilla luciferases through high-affinity binding to a complementary NanoLuc peptide fragment called LgBiT. 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.

Deciphering Acute Myeloid Leukemia Associated Transcription Factors in Human Primary CD34+ Hematopoietic Stem/Progenitor Cells.

Hemato-oncological diseases account for nearly 10% of all malignancies and can be classified into leukemia, lymphoma, myeloproliferative diseases, and myelodysplastic syndromes. The causes and prognosis of these disease entities are highly variable. Most entities are not permanently controllable and ultimately lead to the patient's death. At the molecular level, recurrent mutations including chromosomal translocations initiate the transformation from normal stem-/progenitor cells into malignant blasts finally floating the patient's bone marrow and blood system. In acute myeloid leukemia (AML), the so-called master transcription factors such as RUNX1, KMT2A, and HOX are frequently disrupted by chromosomal translocations, resulting in neomorphic oncogenic fusion genes. Triggering ex vivo expansion of primary human CD34+ stem/progenitor cells represents a distinct characteristic of such chimeric AML transcription factors. Regarding oncogenic mechanisms of AML, most studies focus on murine models. However, due to biological differences between mice and humans, findings are only partly transferable. This review focuses on the genetic manipulation of human CD34+ primary hematopoietic stem/progenitor cells derived from healthy donors to model acute myeloid leukemia cell growth. Analysis of defined single- or multi-hit human cellular AML models will elucidate molecular mechanisms of the development, maintenance, and potential molecular intervention strategies to counteract malignant human AML blast cell growth.

Promoter swapping of truncated PDGFRB drives Ph-like acute lymphoblastic leukemia

Philadelphia chromosome (Ph)-like acute lymphoblastic leukemia (ALL) is a subset of ALL that demonstrated a high treatment failure rate. One of the hallmarks of Ph-like ALL is PDGFRB gene fusion, with fusion partner proteins often harboring dimerization domains and enhancing the kinase activity of PDGFRB. We determined a novel oncogenic PDGFRB fusion gene, NRIP1::PDGFRB, from a pediatric patient with ALL, encoding a protein with the carboxy-terminal kinase domain of PDGFRB, without the partner peptide. We confirmed the oncogenic potential of NRIP1::PDGFRB in vitro and the efficacy of all ABL1-specific inhibitor generations, including imatinib, dasatinib, nilotinib, and ponatinib, in suppressing this potential. PDGFRB activation mechanism may include juxtamembrane domain truncation in the predicted peptide. In conclusion, we determined a novel fusion gene pattern in Ph-like ALL.

Detection of Novel Tyrosine Kinase Fusion Genes as Potential Therapeutic Targets in Bone and Soft Tissue Sarcomas Using DNA/RNA-based Clinical Sequencing.

Approximately 1% of clinically treatable tyrosine kinase fusions, including anaplastic lymphoma kinase, neurotrophic tyrosine receptor kinase, RET proto-oncogene, and ROS proto-oncogene 1, have been identified in soft tissue sarcomas via comprehensive genome profiling based on DNA sequencing. Histologic tumor-specific fusion genes have been reported in approximately 20% of soft tissue sarcomas; however, unlike tyrosine kinase fusion genes, these fusions cannot be directly targeted in therapy. Approximately 80% of tumor-specific fusion-negative sarcomas, including myxofibrosarcoma and leiomyosarcoma, that are defined in complex karyotype sarcomas remain genetically uncharacterized; this mutually exclusive pattern of mutations suggests that other mutually exclusive driver oncogenes are yet to be discovered. Tumor-specific, fusion-negative sarcomas may be associated with unique translocations, and oncogenic fusion genes, including tyrosine kinase fusions, may have been overlooked in these sarcomas. (1) Can DNA- or RNA-based analysis reveal any characteristic gene alterations in bone and soft tissue sarcomas? (2) Can useful and potential tyrosine kinase fusions in tumors from tumor-specific, fusion-negative sarcomas be detected using an RNA-based screening system? (3) Do the identified potential fusion tumors, especially in neurotrophic tyrosine receptor kinase gene fusions in bone sarcoma, transform cells and respond to targeted drug treatment in in vitro assays? (4) Can the identified tyrosine kinase fusion genes in sarcomas be useful therapeutic targets? Between 2017 and 2020, we treated 100 patients for bone and soft tissue sarcomas at five institutions. Any biopsy or surgery from which a specimen could be obtained was included as potentially eligible. Ninety percent (90 patients) of patients were eligible; a further 8% (8 patients) were excluded because they were either lost to follow-up or their diagnosis was changed, leaving 82% (82 patients) for analysis here. To answer our first and second questions regarding gene alterations and potential tyrosine kinase fusions in eight bone and 74 soft tissue sarcomas, we used the TruSight Tumor 170 assay to detect mutations, copy number variations, and gene fusions in the samples. To answer our third question, we performed functional analyses involving in vitro assays to determine whether the identified tyrosine kinase fusions were associated with oncogenic abilities and drug responses. Finally, to determine usefulness as therapeutic targets, two pediatric patients harboring an NTRK fusion and an ALK fusion were treated with tyrosine kinase inhibitors in clinical trials. DNA/RNA-based analysis demonstrated characteristic alterations in bone and soft tissue sarcomas; DNA-based analyses detected TP53 and copy number alterations of MDM2 and CDK4 . These single-nucleotide variants and copy number variations were enriched in specific fusion-negative sarcomas. RNA-based screening detected fusion genes in 24% (20 of 82) of patients. Useful potential fusions were detected in 19% (11 of 58) of tumor-specific fusion-negative sarcomas, with nine of these patients harboring tyrosine kinase fusion genes; five of these patients had in-frame tyrosine kinase fusion genes ( STRN3-NTRK3, VWC2-EGFR, ICK-KDR, FOXP2-MET , and CEP290-MET ) with unknown pathologic significance. The functional analysis revealed that STRN3-NTRK3 rearrangement that was identified in bone had a strong transforming potential in 3T3 cells, and that STRN3-NTRK3 -positive cells were sensitive to larotrectinib in vitro. To confirm the usefulness of identified tyrosine kinase fusion genes as therapeutic targets, patients with well-characterized LMNA-NTRK1 and CLTC-ALK fusions were treated with tyrosine kinase inhibitors in clinical trials, and a complete response was achieved. We identified useful potential therapeutic targets for tyrosine kinase fusions in bone and soft tissue sarcomas using RNA-based analysis. We successfully identified STRN3-NTRK3 fusion in a patient with leiomyosarcoma of bone and determined the malignant potential of this fusion gene via functional analyses and drug effects. In light of these discoveries, comprehensive genome profiling should be considered even if the sarcoma is a bone sarcoma. There seem to be some limitations regarding current DNA-based comprehensive genome profiling tests, and it is important to use RNA testing for proper diagnosis and accurate identification of fusion genes. Studies on more patients, validation of results, and further functional analysis of unknown tyrosine kinase fusion genes are required to establish future treatments. DNA- and RNA-based screening systems may be useful for detecting tyrosine kinase fusion genes in specific fusion-negative sarcomas and identifying key therapeutic targets, leading to possible breakthroughs in the treatment of bone and soft tissue sarcomas. Given that current DNA sequencing misses fusion genes, RNA-based screening systems should be widely considered as a worldwide test for sarcoma. If standard treatments such as chemotherapy are not effective, or even if the sarcoma is of bone, RNA sequencing should be considered to identify as many therapeutic targets as possible.

Discovery and Synthesis of a Naturally Derived Protein Kinase Inhibitor that Selectively Inhibits Distinct Classes of Serine/Threonine Kinases.

The DNAJB1-PRKACA oncogenic gene fusion results in an active kinase enzyme, J-PKAcα, that has been identified as an attractive antitumor target for fibrolamellar hepatocellular carcinoma (FLHCC). A high-throughput assay was used to identify inhibitors of J-PKAcα catalytic activity by screening the NCI Program for Natural Product Discovery (NPNPD) prefractionated natural product library. Purification of the active agent from a single fraction of an Aplidium sp. marine tunicate led to the discovery of two unprecedented alkaloids, aplithianines A (1) and B (2). Aplithianine A (1) showed potent inhibition against J-PKAcα with an IC50 of ∼1 μM in the primary screening assay. In kinome screening, 1 inhibited wild-type PKA with an IC50 of 84 nM. Further mechanistic studies including cocrystallization and X-ray diffraction experiments revealed that 1 inhibited PKAcα catalytic activity by competitively binding to the ATP pocket. Human kinome profiling of 1 against a panel of 370 kinases revealed potent inhibition of select serine/threonine kinases in the CLK and PKG families with IC50 values in the range ∼11-90 nM. An efficient, four-step total synthesis of 1 has been accomplished, enabling further evaluation of aplithianines as biologically relevant kinase inhibitors.

MIG6 Mediates Adaptive and Acquired Resistance to ALK/ROS1 Fusion Kinase Inhibition through EGFR Bypass Signaling.

Despite the initial benefit from tyrosine kinase inhibitors (TKI) targeting oncogenic ALK and ROS1 gene fusions in non-small cell lung cancer, complete responses are rare and resistance ultimately emerges from residual tumor cells. Although several acquired resistance mechanisms have been reported at the time of disease progression, adaptative resistance mechanisms that contribute to residual diseases before the outgrowth of tumor cells with acquired resistance are less clear. For the patients who have progressed after TKI treatments, but do not demonstrate ALK/ROS1 kinase mutations, there is a lack of biomarkers to guide effective treatments. Herein, we found that phosphorylation of MIG6, encoded by the ERRFI1 gene, was downregulated by ALK/ROS1 inhibitors as were mRNA levels, thus potentiating EGFR activity to support cell survival as an adaptive resistance mechanism. MIG6 downregulation was sustained following chronic exposure to ALK/ROS1 inhibitors to support the establishment of acquired resistance. A higher ratio of EGFR to MIG6 expression was found in ALK TKI-treated and ALK TKI-resistant tumors and correlated with the poor responsiveness to ALK/ROS1 inhibition in patient-derived cell lines. Furthermore, we identified and validated a MIG6 EGFR-binding domain truncation mutation in mediating resistance to ROS1 inhibitors but sensitivity to EGFR inhibitors. A MIG6 deletion was also found in a patient after progressing to ROS1 inhibition. Collectively, this study identifies MIG6 as a novel regulator for EGFR-mediated adaptive and acquired resistance to ALK/ROS1 inhibitors and suggests EGFR to MIG6 ratios and MIG6-damaging alterations as biomarkers to predict responsiveness to ALK/ROS1 and EGFR inhibitors.

Clinical Implementation of MetaFusion for Accurate Cancer-Driving Fusion Detection from RNA Sequencing

Oncogenic fusion genes may be identified from next-generation sequencing data, typically RNA-sequencing. However, in a clinical setting, identifying these alterations is challenging against a background of nonrelevant fusion calls that reduce workflow precision and specificity. Furthermore, although numerous algorithms have been developed to detect fusions in RNA-sequencing, there are variations in their individual sensitivities. Here this problem was addressed by introducing MetaFusion into clinical use. Its utility was illustrated when applied to both whole-transcriptome and targeted sequencing data sets. MetaFusion combines ensemble fusion calls from eight individual fusion-calling algorithms with practice-informed identification of gene fusions that are known to be clinically relevant. In doing so, it allows oncogenic fusions to be identified with near-perfect sensitivity and high precision and specificity, significantly outperforming the individual fusion callers it uses as well as existing clinical-grade software. MetaFusion enhances clinical yield over existing methods and is able to identify fusions that have patient relevance for the purposes of diagnosis, prognosis, and treatment.