Combining AFM13, a Bispecific CD30/CD16 Antibody, with Cytokine-Activated Blood and Cord Blood-Derived NK Cells Facilitates CAR-like Responses Against CD30+ Malignancies

PURPOSE

Natural killer (NK)-cell recognition and function against NK-resistant cancers remain substantial barriers to the broad application of NK-cell immunotherapy. Potential solutions include bispecific engagers that target NK-cell activity via an NK-activating receptor when simultaneously targeting a tumor-specific antigen, as well as enhancing functionality using IL12/15/18 cytokine pre-activation.

EXPERIMENTAL DESIGN

We assessed single-cell NK-cell responses stimulated by the tetravalent bispecific antibody AFM13 that binds CD30 on leukemia/lymphoma targets and CD16A on various types of NK cells using mass cytometry and cytotoxicity assays. The combination of AFM13 and IL12/15/18 pre-activation of blood and cord blood-derived NK cells was investigated in vitro and in vivo.

RESULTS

We found heterogeneity within AFM13-directed conventional blood NK cell (cNK) responses, as well as consistent AFM13-directed polyfunctional activation of mature NK cells across donors. NK-cell source also impacted the AFM13 response, with cNK cells from healthy donors exhibiting superior responses to those from patients with Hodgkin lymphoma. IL12/15/18-induced memory-like NK cells from peripheral blood exhibited enhanced killing of CD30+ lymphoma targets directed by AFM13, compared with cNK cells. Cord-blood NK cells preactivated with IL12/15/18 and ex vivo expanded with K562-based feeders also exhibited enhanced killing with AFM13 stimulation via upregulation of signaling pathways related to NK-cell effector function. AFM13-NK complex cells exhibited enhanced responses to CD30+ lymphomas in vitro and in vivo.

CONCLUSIONS

We identify AFM13 as a promising combination with cytokine-activated adult blood or cord-blood NK cells to treat CD30+ hematologic malignancies, warranting clinical trials with these novel combinations.

Emerging CAR landscape for cancer immunotherapy

In the last decade, there has been great advancement in manipulating the immune system or the cells of the immune system to bring about effective therapies. While harnessing the immune system against cancer is not a new concept, successful reprograming with T cells with chimeric antigen receptor (CAR) forming CAR-T cell therapy has revolutionized the treatment landscape for patients with refractory, high-grade B cell malignancies. The journey from proof-of-concept to FDA-approved commercial CAR-T products has taken almost 3 decades and untold amount of efforts, resources and manpower. With the success of CD19 CAR adoptive cellular immunotherapy leading the charge, CARs targeting various malignancies are in various stages of active development, racing towards regulatory approval, and raising hopes of further breakthroughs in cancer treatment options. In this review we will highlight recent clinical developments of the B cell maturation antigen (BCMA) CAR-T therapy for multiple myeloma (MM) to showcase how innovative CAR designs, coupled with careful selection of tumor-associated antigens, used in combination with other therapeutic agents, could help overcome some of the current limitations experienced in CAR-T immunotherapy. More patients could benefit from novel upfront cell therapy trials, that when combined with the current established induction regimens could have the potential to recondition and alter tumor environments, help restore somnolent anti-tumor immunity, and induce more effective and durable remissions.

Regulation of ferrochelatase gene expression by hypoxia

Ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, catalyzes the insertion of iron into protoporphyrin to form heme. This pathway provides heme for hemoglobin and other essential hemoproteins. The regulatory role of oxygen in the pathway has not been clearly established. In this study, we examined whether FECH gene expression is upregulated during hypoxia by a mechanism which involves the hypoxia-inducible factor 1 (HIF-1). Two HIF-1 binding motifs were identified within the -150 bp FECH minimal promoter sequence. Exposure of HEL, K562, and Hep-G2 cells to hypoxia for 18 hours resulted in a significant increase in FECH mRNA expression (p < 0.05). Hypoxia also transactivated the minimal promoter for the FECH gene in the cells. Transient co-expression of wild-type HIF-1alpha or a dominant negative HIF-1alpha with the FECH minimal promoter luciferase construct stimulated or blocked FECH promoter activity, respectively. Expression of the von Hippel-Lindau (VHL) tumor suppressor factor blocked the expression of both FECH mRNA and HIF-1alpha protein during normoxic culture of renal carcinoma cell line (RCC4). The results suggest that the FECH gene is a target for HIF-1 during hypoxia.

Role of RUNX1 in adult hematopoiesis: analysis of RUNX1-IRES-GFP knock-in mice reveals differential lineage expression

The Runx1/core binding factor-beta (CBFbeta) transcriptional complex is required for the establishment of hematopoiesis during development. Despite its critical role during development, a detailed analysis of Runx1 expression within specific lineages and developmental stages of the adult hematopoietic system is lacking. To address this, we have developed a Runx1-green fluorescent protein (GFP) knock-in mouse. We show that Runx1 is expressed in several hematopoietic lineages, including myeloid, B-lymphoid, and T-lymphoid cells. By contrast, Runx1 is weakly expressed in early erythroid cells, and its expression is rapidly extinguished during later stages of erythropoiesis. Runx1 expression is induced during early B-cell development and is expressed at a uniform level during all subsequent stages of B-cell development. Within the thymus, Runx1 is expressed at the highest level in CD4-CD8- double-negative thymocytes. In peripheral T cells, Runx1 is differentially expressed, with CD4+ T cells expressing 2- to 3-fold higher levels of Runx1 than CD8+ cells. Taken together, these findings indicate that although widely expressed in the hematopoietic system, the expression of Runx1 is regulated in a cell type- and maturation stage-specific manner. In addition, the Runx1-IRES-GFP knock-in mouse strain should prove valuable for investigation of Runx1 function in adult hematopoiesis.

The worldwide distribution of the VHL 598C>T mutation indicates a single founding event

The first congenital defect of hypoxia-sensing homozygosity for VHL 598C>T mutation was recently identified in Chuvash polycythemia. Subsequently, we found this mutation in 11 unrelated individuals of diverse ethnic backgrounds. To address the question of whether the VHL 598C>T substitution occurred in a single founder or resulted from recurrent mutational events in human evolution, we performed haplotype analysis of 8 polymorphic markers covering 340 kb spanning the VHL gene on 101 subjects bearing the VHL 598C>T mutation, including 72 homozygotes (61 Chuvash and 11 non-Chuvash) and 29 heterozygotes (11 Chuvash and 18 non-Chuvash), and 447 healthy unrelated individuals from Chuvash and other ethnic groups. The differences in allele frequencies for each of the 8 markers between 447 healthy controls (598C) and 101 subjects bearing the 598T allele (P < 10(-7)) showed strong linkage disequilibrium. Haplotype analysis indicated a founder effect. We conclude that the VHL 598C>T mutation, the most common defect of congenital polycythemia yet found, was spread from a single founder 1,000 to 62,000 years ago.

Disruption of oxygen homeostasis underlies congenital Chuvash polycythemia

Chuvash polycythemia is an autosomal recessive disorder that is endemic to the mid-Volga River region. We previously mapped the locus associated with Chuvash polycythemia to chromosome 3p25. The gene associated with von Hippel-Lindau syndrome, VHL, maps to this region, and homozygosity with respect to a C-->T missense mutation in VHL, causing an arginine-to-tryptophan change at amino-acid residue 200 (Arg200Trp), was identified in all individuals affected with Chuvash polycythemia. The protein VHL modulates the ubiquitination and subsequent destruction of hypoxia-inducible factor 1, subunit alpha (HIF1alpha). Our data indicate that the Arg200Trp substitution impairs the interaction of VHL with HIF1alpha, reducing the rate of degradation of HIF1alpha and resulting in increased expression of downstream target genes including EPO (encoding erythropoietin), SLC2A1 (also known as GLUT1, encoding solute carrier family 2 (facilitated glucose transporter), member 1), TF (encoding transferrin), TFRC (encoding transferrin receptor (p90, CD71)) and VEGF (encoding vascular endothelial growth factor).

Endemic polycythemia in Russia: mutation in the VHL gene

Chuvash polycythemia (CP) is an autosomal recessive condition that is endemic in the Russian mid-Volga River region of Chuvashia. We previously found that CP patients may have increased serum erythropoietin (EPO) levels, ruled out linkage to both the EPO and EPO receptor (EPOR) gene loci, and hypothesized that the defect may lie in the oxygen homeostasis pathway. We now report a study of five multiplex Chuvash families which confirms that CP is associated with significant elevations of serum EPO levels and rules out a location for the CP gene on chromosome 11 as had been reported by other investigators or a mutation of the HIF-1 alpha gene. Using a genome-wide screen, we localized a region on chromosome 3 with a LOD score >2. After sequencing three candidate genes, we identified a C to T transition at nucleotide 598 (an R200W mutation) in the von Hippel-Lindau (VHL) gene. The VHL protein (pVHL) downregulates the alpha subunit of hypoxia-inducible factor 1 (HIF-1 alpha), the main regulator of hypoxia adaptation, by targeting the protein for degradation. In the simplest scenario, disruption of pVHL function causes a failure to degrade HIF-1 alpha resulting in accumulation of HIF-1 alpha, upregulation of downstream target genes such as EPO, and the clinical manifestation of polycythemia. These findings strongly suggest that CP is a congenital disorder of oxygen homeostasis.