Siglec-6 as a therapeutic target for cell migration and adhesion in chronic lymphocytic leukemia.

Siglec-6 is a lectin receptor with restricted expression in the placenta, mast cells and memory B-cells. Although Siglec-6 is expressed in patients with chronic lymphocytic leukemia (CLL), its pathophysiological role has not been elucidated. We describe here a role for Siglec-6 in migration and adhesion of CLL B cells to CLL- bone marrow stromal cells (BMSCs) in vitro and compromised migration to bone marrow and spleen in vivo. Mass spectrometry analysis revealed interaction of Siglec-6 with DOCK8, a guanine nucleotide exchange factor. Stimulation of MEC1-002 CLL cells with a Siglec-6 ligand, sTn, results in Cdc42 activation, WASP protein recruitment and F-actin polymerization, which are all associated with cell migration. Therapeutically, a Siglec-6/CD3-bispecific T-cell-recruiting antibody (T-biAb) improves overall survival in an immunocompetent mouse model and eliminates CLL cells in a patient derived xenograft model. Our findings thus reveal a migratory role for Siglec-6 in CLL, which can be therapeutically targeted using a Siglec-6 specific T-biAb.

Repression of PRMT activities sensitize homologous recombination-proficient ovarian and breast cancer cells to PARP inhibitor treatment.

An "induced PARP inhibitor (PARPi) sensitivity by epigenetic modulation" strategy is being evaluated in the clinic to sensitize homologous recombination (HR)-proficient tumors to PARPi treatments. To expand its clinical applications and identify more efficient combinations, we performed a drug screen by combining PARPi with 74 well-characterized epigenetic modulators that target five major classes of epigenetic enzymes. Both type I PRMT inhibitor and PRMT5 inhibitor exhibit high combination and clinical priority scores in our screen. PRMT inhibition significantly enhances PARPi treatment-induced DNA damage in HR-proficient ovarian and breast cancer cells. Mechanistically, PRMTs maintain the expression of genes associated with DNA damage repair and BRCAness and regulate intrinsic innate immune pathways in cancer cells. Analyzing large-scale genomic and functional profiles from TCGA and DepMap further confirms that PRMT1, PRMT4, and PRMT5 are potential therapeutic targets in oncology. Finally, PRMT1 and PRMT5 inhibition act synergistically to enhance PARPi sensitivity. Our studies provide a strong rationale for the clinical application of a combination of PRMT and PARP inhibitors in patients with HR-proficient ovarian or breast cancer.

DLL3-guided therapies in small-cell lung cancer: from antibody-drug conjugate to precision immunotherapy and radioimmunotherapy.

DLL3 acts as an inhibitory ligand that downregulates Notch signaling and is upregulated by ASCL1, a transcription factor prevalent in the small-cell lung cancer (SCLC) subtype SCLC-A. Currently, the therapeutic strategies targeting DLL3 are varied, including antibody-drug conjugates (ADCs), bispecific T-cell engagers (BiTEs), and chimeric antigen receptor (CAR) T-cell therapies. Although rovalpituzumab tesirine (Rova-T) showed promise in a phase II study, it failed to produce favorable results in subsequent phase III trials, leading to the cessation of its development. Conversely, DLL3-targeted BiTEs have garnered significant clinical interest. Tarlatamab, for instance, demonstrated enhanced response rates and progression-free survival compared to the standard of care in a phase II trial; its biologics license application (BLA) is currently under US Food and Drug Administration (FDA) review. Numerous ongoing phase III studies aim to further evaluate tarlatamab's clinical efficacy, alongside the development of novel DLL3-targeted T-cell engagers, both bispecific and trispecific. CAR-T cell therapies targeting DLL3 have recently emerged and are undergoing various preclinical and early-phase clinical studies. Additionally, preclinical studies have shown promising efficacy for DLL3-targeted radiotherapy, which employs ß-particle-emitting therapeutic radioisotopes conjugated to DLL3-targeting antibodies. DLL3-targeted therapies hold substantial potential for SCLC management. Future clinical trials will be crucial for comparing treatment outcomes among various approaches and exploring combination therapies to improve patient survival outcomes.

A CD3 humanized mouse model unmasked unique features of T-cell responses to bispecific antibody treatment.

ABSTRACT: T-cell bispecific antibodies (T-BsAbs) such as blinatumomab hold great promise for cancer immunotherapy. A better understanding of the in vivo immune response induced by T-BsAbs is crucial to improving their efficacy and safety profile. However, such efforts are hindered by the limitations of current preclinical models. To address this, we developed a syngeneic murine model with humanized CD3 and target antigen (CD20). This model enables the development of disseminated leukemia with a high tumor burden, which mirrors clinical findings in human patients with relapsed/refractory acute lymphoblastic leukemia. Treatment of this model with T-BsAbs results in cytokine release syndrome, with cytokine profiles and levels reflecting observations made in human patients. This model also faithfully recapitulates the dynamics of T-cell activation seen in human patients, including the temporary disappearance of T cells from the bloodstream. During this phase, T cells are sequestered in secondary lymphoid organs and undergo activation. Clinical correlative studies that rely primarily on peripheral blood samples are likely to overlook this critical activation stage, leading to a substantial underestimation of the extent of T-cell activation. Furthermore, we demonstrate that surface expression of the T-BsAb target antigen by leukemia cells triggers a swift immune response, promoting their own rejection. Humanizing the target antigen in the recipient mice is crucial to facilitate tolerance induction and successful establishment of high tumor burden. Our findings underscore the importance of meticulously optimized syngeneic murine models for investigating T-BsAb-induced immune responses and for translational research aimed at improving efficacy and safety.

Factors Affecting the Cancer Immunotherapeutic Efficacy of T Cell Bispecific Antibodies and Strategies for Improvement.

T-cell bispecific antibodies (T-BsAbs) are a new class of cancer immunotherapy drugs that can simultaneously bind to tumor-associated antigens on target cells and to the CD3 subunit of the T-cell receptor (TCR) on T cells. In the last decade, numerous T-BsAbs have been developed for the treatment of both hematological malignancies and solid tumors. Among them, blinatumomab has been successfully used to treat CD19 positive malignancies and has been approved by the FDA as standard care for acute lymphoblastic leukemia (ALL). However, in many clinical scenarios, the efficacy of T-BsAbs remains unsatisfactory. To further improve T-BsAb therapy, it will be crucial to better understand the factors affecting treatment efficacy and the nature of the T-BsAb-induced immune response. Herein, we first review the studies on the potential mechanisms by which T-BsAbs activate T-cells and how they elicit efficient target killing despite suboptimal costimulatory support. We focus on analyzing reports from clinical trials and preclinical studies, and summarize the factors that have been identified to impact the efficacy of T-BsAbs. Lastly, we review current and propose new approaches to improve the clinical efficacy of T-BsAbs.

SUSD2 suppresses CD8+ T cell antitumor immunity by targeting IL-2 receptor signaling.

Dysfunctional CD8+ T cells, which have defective production of antitumor effectors, represent a major mediator of immunosuppression in the tumor microenvironment. Here, we show that SUSD2 is a negative regulator of CD8+ T cell antitumor function. Susd2-/- effector CD8+ T cells showed enhanced production of antitumor molecules, which consequently blunted tumor growth in multiple syngeneic mouse tumor models. Through a quantitative mass spectrometry assay, we found that SUSD2 interacted with interleukin (IL)-2 receptor α through sushi domain-dependent protein interactions and that this interaction suppressed the binding of IL-2, an essential cytokine for the effector functions of CD8+ T cells, to IL-2 receptor α. SUSD2 was not expressed on regulatory CD4+ T cells and did not affect the inhibitory function of these cells. Adoptive transfer of Susd2-/- chimeric antigen receptor T cells induced a robust antitumor response in mice, highlighting the potential of SUSD2 as an immunotherapy target for cancer.

Leukemia-initiating HSCs in chronic lymphocytic leukemia reveal clonal leukemogenesis and differential drug sensitivity.

The existence of "leukemia-initiating cells" (LICs) in chronic lymphocytic leukemia (CLL) remains controversial due to the difficulty in isolating and identifying the tumor-initiating cells. Here, we demonstrate a microchannel electroporation (MEP) microarray that injects RNA-detecting probes into single live cells, allowing the imaging and characterization of heterogeneous LICs by intracellular RNA expression. Using limited-cell FACS sequencing (LC-FACSeq), we can detect and monitor rare live LICs during leukemogenesis and characterize their differential drug sensitivity. Disease-associated mutation accumulation in developing B lymphoid but not myeloid lineage in CLL patient hematopoietic stem cells (CLL-HSCs), and development of independent clonal CLL-like cells in murine patient-derived xenograft models, suggests the existence of CLL LICs. Furthermore, we identify differential protein ubiquitination and unfolding response signatures in GATA2high CLL-HSCs that exhibit increased sensitivity to lenalidomide and resistance to fludarabine compared to GATA2lowCLL-HSCs. These results highlight the existence of therapeutically targetable disease precursors in CLL.

Systematic illumination of druggable genes in cancer genomes.

By combining 6 druggable genome resources, we identify 6,083 genes as potential druggable genes (PDGs). We characterize their expression, recurrent genomic alterations, cancer dependencies, and therapeutic potentials by integrating genome, functionome, and druggome profiles across cancers. 81.5% of PDGs are reliably expressed in major adult cancers, 46.9% show selective expression patterns, and 39.1% exhibit at least one recurrent genomic alteration. We annotate a total of 784 PDGs as dependent genes for cancer cell growth. We further quantify 16 cancer-related features and estimate a PDG cancer drug target score (PCDT score). PDGs with higher PCDT scores are significantly enriched for genes encoding kinases and histone modification enzymes. Importantly, we find that a considerable portion of high PCDT score PDGs are understudied genes, providing unexplored opportunities for drug development in oncology. By integrating the druggable genome and the cancer genome, our study thus generates a comprehensive blueprint of potential druggable genes across cancers.

Systematic Pan-Cancer Characterization of Nuclear Receptors Identifies Potential Cancer Biomarkers and Therapeutic Targets.

The nuclear receptor (NR) superfamily is one of the major druggable gene families, representing targets of approximately 13.5% of approved drugs. Certain NRs, such as estrogen receptor and androgen receptor, have been well demonstrated to be functionally involved in cancer and serve as informative biomarkers and therapeutic targets in oncology. However, the spectrum of NR dysregulation across cancers remains to be comprehensively characterized. Through computational integration of genetic, genomic, and pharmacologic profiles, we characterized the expression, recurrent genomic alterations, and cancer dependency of NRs at a large scale across primary tumor specimens and cancer cell lines. Expression levels of NRs were highly cancer-type specific and globally downregulated in tumors compared with corresponding normal tissue. Although the majority of NRs showed copy-number losses in cancer, both recurrent focal gains and losses were identified in select NRs. Recurrent mutations and transcript fusions of NRs were observed in a small portion of cancers, serving as actionable genomic alterations. Analysis of large-scale CRISPR and RNAi screening datasets identified 10 NRs as strongly selective essential genes for cancer cell growth. In a subpopulation of tumor cells, growth dependencies correlated significantly with expression or genomic alterations. Overall, our comprehensive characterization of NRs across cancers may facilitate the identification and prioritization of potential biomarkers and therapeutic targets, as well as the selection of patients for precision cancer treatment. SIGNIFICANCE: Computational analysis of nuclear receptors across multiple cancer types provides a series of biomarkers and therapeutic targets within this protein family.

The ROR1 antibody-drug conjugate huXBR1-402-G5-PNU effectively targets ROR1+ leukemia.

Antibody-drug conjugates directed against tumor-specific targets have allowed targeted delivery of highly potent chemotherapy to malignant cells while sparing normal cells. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein with limited expression on normal adult tissues and is overexpressed on the surface of malignant cells in mantle cell lymphoma, acute lymphocytic leukemia with t(1;19)(q23;p13) translocation, and chronic lymphocytic leukemia. This differential expression makes ROR1 an attractive target for antibody-drug conjugate therapy, especially in malignancies such as mantle cell lymphoma and acute lymphocytic leukemia, in which systemic chemotherapy remains the gold standard. Several preclinical and phase 1 clinical studies have established the safety and effectiveness of anti-ROR1 monoclonal antibody-based therapies. Herein we describe a humanized, first-in-class anti-ROR1 antibody-drug conjugate, huXBR1-402-G5-PNU, which links a novel anti-ROR1 antibody (huXBR1-402) to a highly potent anthracycline derivative (PNU). We found that huXBR1-402-G5-PNU is cytotoxic to proliferating ROR1+ malignant cells in vitro and suppressed leukemia proliferation and extended survival in multiple models of mice engrafted with human ROR1+ leukemia. Lastly, we show that the B-cell lymphoma 2 (BCL2)-dependent cytotoxicity of huXBR1-402-G5-PNU can be leveraged by combined treatment strategies with the BCL2 inhibitor venetoclax. Together, our data present compelling preclinical evidence for the efficacy of huXBR1-402-G5-PNU in treating ROR1+ hematologic malignancies.

Prognostic significance of translocations in the presence of mutated IGHV and of cytogenetic complexity at diagnosis of chronic lymphocytic leukemia.

Mutations of the IGH variable region in patients with chronic lymphocytic leukemia (CLL) are associated with a favorable prognosis. Cytogenetic complexity (>3 unrelated aberrations) and translocations have been associated with an unfavorable prognosis. While mutational status of IGHV is stable, cytogenetic aberrations frequently evolve. However, the relationships of these features as prognosticators at diagnosis are unknown. We examined the CpG-stimulated metaphase cytogenetic features detected within one year of diagnosis of CLL and correlated these features with outcome and other clinical features including IGHV. Of 329 untreated patients, 53 (16.1%) had a complex karyotype (16.1%), and 85 (25.8%) had a translocation. Median time to first treatment (TFT) was 47 months. In univariable analyses, significant risk factors for shorter TFT (p3.5, log-transformed WBC, unmutated IGHV, complex karyotype, translocation, and FISH for trisomy 8, del(11q) and del(17p). In multivariable analysis, there was significant effect modification of IGHV status on the relationship between translocation and TFT (p=0.002). In IGHV mutated patients, those with a translocation had over 3.5 times higher risk of starting treatment than those without a translocation (p.

CD33-Targeted Therapies: Beating the Disease or Beaten to Death?

CD33 is a transmembrane protein that is found on cells of myeloid lineage. It is also intensely expressed on acute myeloid leukemia (AML) progenitor cells but not on normal stem cells. It internalizes on binding and dimerization, making it a specific and ideal target for AML therapeutics and drug delivery. Several targeted therapies have been tested and many are still currently in development. Gemtuzumab ozogamicin was the first and only CD33-directed antibody-drug conjugate to be US Food and Drug Administration approved for AML. Other targeted agents have not achieved such success. Promising new strategies include cellular therapy mechanisms and linker molecules. This is an exciting target that requires a considerable amount of precision to yield clinical benefit.

The Cancer Surfaceome Atlas integrates genomic, functional and drug response data to identify actionable targets.

Cell-surface proteins (SPs) are a rich source of immune and targeted therapies. By systematically integrating single-cell and bulk genomics, functional studies and target actionability, in the present study we comprehensively identify and annotate genes encoding SPs (GESPs) pan-cancer. We characterize GESP expression patterns, recurrent genomic alterations, essentiality, receptor-ligand interactions and therapeutic potential. We also find that mRNA expression of GESPs is cancer-type specific and positively correlates with protein expression, and that certain GESP subgroups function as common or specific essential genes for tumor cell growth. We also predict receptor-ligand interactions substantially deregulated in cancer and, using systems biology approaches, we identify cancer-specific GESPs with therapeutic potential. We have made this resource available through the Cancer Surfaceome Atlas ( http://fcgportal.org/TCSA ) within the Functional Cancer Genome data portal.

Incidence of venous thrombosis after peg-asparaginase in adolescent and young adults with acute lymphoblastic leukemia.

AIM: There are limited data describing incidence of symptomatic venous thromboembolism (VTE) in adolescent and young adult (AYA) acute lymphoblastic leukemia (ALL) patients receiving peg-asparaginase. MATERIALS & METHODS: Single-institution retrospective analysis of 44 AYA ALL patients treated with peg-asparaginase. Rates of VTE and proposed risk factors were assessed. RESULTS: 18 patients (41%) had a symptomatic VTE following peg-asparaginase. The cumulative incidence rate was 25% (95% CI: 13-38%) within 30 days of the initial dose. Personal history of thrombosis was statistically significantly associated with an increased risk of VTE with HR of 2.73 (95% CI: 1.40-5.33, p = 0.003) after adjusting for gender. CONCLUSION: These data indicate a high rate of VTE in the AYA ALL population following treatment with peg-asparaginase.

Systematic Characterization of Recurrent Genomic Alterations in Cyclin-Dependent Kinases Reveals Potential Therapeutic Strategies for Cancer Treatment.

Recurrent copy-number alterations, mutations, and transcript fusions of the genes encoding CDKs/cyclins are characterized in >10,000 tumors. Genomic alterations of CDKs/cyclins are dominantly driven by copy number aberrations. In contrast to cell-cycle-related CDKs/cyclins, which are globally amplified, transcriptional CDKs/cyclins recurrently lose copy numbers across cancers. Although mutations and transcript fusions are relatively rare events, CDK12 exhibits recurrent mutations in multiple cancers. Among the transcriptional CDKs, CDK7 and CDK12 show the most significant copy number loss and mutation, respectively. Their genomic alterations are correlated with increased sensitivities to DNA-damaging drugs. Inhibition of CDK7 preferentially represses the expression of genes in the DNA-damage-repair pathways and impairs the activity of homologous recombination. Low-dose CDK7 inhibitor treatment sensitizes cancer cells to PARP inhibitor-induced DNA damage and cell death. Our analysis provides genomic information for identification and prioritization of drug targets for CDKs and reveals rationales for treatment strategies.

Integrative comparison of the genomic and transcriptomic landscape between prostate cancer patients of predominantly African or European genetic ancestry.

Men of predominantly African Ancestry (AA) have higher prostate cancer (CaP) incidence and worse survival than men of predominantly European Ancestry (EA). While socioeconomic factors drive this disparity, genomic factors may also contribute to differences in the incidence and mortality rates. To compare the prevalence of prostate tumor genomic alterations and transcriptomic profiles by patient genetic ancestry, we evaluated genomic profiles from The Cancer Genome Atlas (TCGA) CaP cohort (n = 498). Patient global and local genetic ancestry were estimated by computational algorithms using genotyping data; 414 (83.1%) were EA, 61 (12.2%) were AA, 11 (2.2%) were East Asian Ancestry (EAA), 10 (2.0%) were Native American (NA), and 2 (0.4%) were other ancestry. Genetic ancestry was highly concordant with self-identified race/ethnicity. Subsequent analyses were limited to 61 AA and 414 EA cases. Significant differences were observed by ancestry in the frequency of SPOP mutations (20.3% AA vs. 10.0% EA; p = 5.6×10-03), TMPRSS2-ERG fusions (29.3% AA vs. 39.6% EA; p = 4.4×10-02), and PTEN deletions/losses (11.5% AA vs. 30.2% EA; p = 3.5×10-03). Differentially expressed genes (DEGs) between AAs and EAs showed significant enrichment for prostate eQTL target genes (p = 8.09×10-48). Enrichment of highly expressed DEGs for immune-related pathways was observed in AAs, and for PTEN/PI3K signaling in EAs. Nearly one-third of DEGs (31.3%) were long non-coding RNAs (DE-lncRNAs). The proportion of DE-lncRNAs with higher expression in AAs greatly exceeded that with lower expression in AAs (p = 1.2×10-125). Both ChIP-seq and RNA-seq data suggested a stronger regulatory role for AR signaling pathways in DE-lncRNAs vs. non-DE-lncRNAs. CaP-related oncogenic lncRNAs, such as PVT1, PCAT1 and PCAT10/CTBP1-AS, were found to be more highly expressed in AAs. We report substantial heterogeneity in the prostate tumor genome and transcriptome between EA and AA. These differences may be biological contributors to racial disparities in CaP incidence and outcomes.