Validation of a DKK1 RNAscope chromogenic in situ hybridization assay for gastric and gastroesophageal junction adenocarcinoma tumors.

Dickkopf-1 (DKK1) is a secreted modulator of Wnt signaling that is frequently overexpressed in tumors and associated with poor clinical outcomes. DKN-01 is a humanized monoclonal therapeutic antibody that binds DKK1 with high affinity and has demonstrated clinical activity in gastric/gastroesophageal junction (G/GEJ) patients with elevated tumoral expression of DKK1. Here we report on the validation of a DKK1 RNAscope chromogenic in situ hybridization assay to assess DKK1 expression in G/GEJ tumor tissue. To reduce pathologist time, potential pathologist variability from manual scoring and support pathologist decision making, a digital image analysis algorithm that identifies tumor cells and quantifies the DKK1 signal was developed. Following CLIA guidelines the DKK1 RNAscope chromogenic in situ hybridization assay and digital image analysis algorithm were successfully validated for sensitivity, specificity, accuracy, and precision. The DKK1 RNAscope assay in conjunction with the digital image analysis solution is acceptable for prospective screening of G/GEJ adenocarcinoma patients. The work described here will further advance the companion diagnostic development of our DKK1 RNAscope assay and could generally be used as a guide for the validation of RNAscope assays with digital image quantification.

mDKN-01, a Novel Anti-DKK1 mAb, Enhances Innate Immune Responses in the Tumor Microenvironment.

Dickkopf-1 (DKK1), a secreted modulator of Wnt signaling, is overexpressed in many cancers, is often associated with worse clinical outcomes, and has been shown to have immunosuppressive effects. DKN-01 is an IgG4 clinical stage antibody that potently and specifically neutralizes human and murine DKK1 and has recently completed a promising study in combination with pembrolizumab in patients with gastric/gastroesophageal junction cancer. The purpose of this study is to characterize a murine version of DKN-01 (mDKN-01) and to better understand its mechanism of action. We examined the efficacy of mDKN-01 in both melanoma and metastatic breast cancer models. Immune depletion experiments revealed a requirement for natural killer (NK) but not B and T cells for tumor growth inhibition. mDKN-01 treatment promotes the induction of the NK-activating cytokines IL15 and IL33 as well as an enhanced recruitment of CD45+ cells. Other treatment-related changes include a reduction of Gr-1+CD11b+ myeloid-derived suppressor cells (MDSC) in the tumor and spleen and the upregulation of PD-L1 on MDSCs. In addition, mDKN-01 has a marked effect at reducing pulmonary metastases in the mouse 4T1 breast cancer model. Finally, the mDKN-01/anti-PD-1 combination was more effective at inhibiting melanoma growth than mDKN-01 alone. Taken together, our data demonstrate that mDKN-01 has efficacy by blocking the immunosuppressive effects of DKK1 in the tumor microenvironment (TME) and provides insight into the clinical activity observed with DKN-01-based treatment. IMPLICATIONS: mDKN-01 reverses a DKK1-mediated innate immune suppression in the TME and has additive efficacy with a PD-1 inhibitor.

Natural IgM Blockade Limits Infarct Expansion and Left Ventricular Dysfunction in a Swine Myocardial Infarct Model.

BACKGROUND: Acute coronary syndrome is the leading cause of mortality worldwide. However, treatment of acute coronary occlusion inevitably results in ischemia-reperfusion injury. Circulating natural IgM has been shown to play a significant role in mouse models of ischemia-reperfusion injury. A highly conserved self-antigen, nonmuscle myosin heavy chain II, has been identified as a target of pathogenic IgM. We hypothesized that a monoclonal antibody (m21G6) directed against nonmuscle myosin heavy chain II may inhibit IgM binding and reduce injury in a preclinical model of myocardial infarction. Thus, our objective was to evaluate the efficacy of intravenous m21G6 treatment in limiting infarct expansion, troponin release, and left ventricular dysfunction in a swine myocardial infarction model. METHODS AND RESULTS: Massachusetts General Hospital miniature swine underwent occlusion of the midleft anterior descending coronary artery for 60 minutes, followed by 1 hour, 5-day, or 21-day reperfusion. Specificity and localization of m21G6 to injured myocardium were confirmed using fluorescently labeled m21G6. Treatment with m21G6 before reperfusion resulted in a 49% reduction in infarct size (P<0.005) and a 61% reduction in troponin-T levels (P<0.05) in comparison with saline controls at 5-day reperfusion. Furthermore, m21G6-treated animals recovered 85.4% of their baseline left ventricular function as measured by 2-dimensional transthoracic echocardiography in contrast to 67.1% in controls at 21-day reperfusion (P<0.05). CONCLUSIONS: Treatment with m21G6 significantly reduced infarct size and troponin-T release, and led to marked preservation of cardiac function in our study. Overall, these findings suggest that pathogenic IgM blockade represents a valid therapeutic strategy in mitigating myocardial ischemia-reperfusion injury.

Protective anti-inflammatory effect of ADAMTS13 on myocardial ischemia/reperfusion injury in mice.

Coronary heart disease is a major cause of death in the western world. Although essential for successful recovery, reperfusion of ischemic myocardium is inevitably associated with reperfusion injury. To investigate a potential protective role of ADAMTS13, a protease cleaving von Willebrand factor multimers, during myocardial ischemia/reperfusion, we used a mouse model of acute myocardial infarction. We found that Adamts13(-/-) mice developed larger myocardial infarctions than wild-type control mice, whereas treatment of wild-type mice with recombinant human ADAMTS13 (rhADAMTS13) led to smaller infarctions. The protective effect of ADAMTS13 was further confirmed by a significant reduction of cardiac troponin-I release and less myocardial apoptosis in mice that received rhADAMTS13 compared with controls. Platelets adherent to the blood vessel wall were observed in few areas in the heart samples from mice treated with vehicle and were not detected in samples from mice treated with rhADAMTS13. However, we observed a 9-fold reduction in number of neutrophils infiltrating ischemic myocardium in mice that were treated with rhADAMTS13, suggesting a potent anti-inflammatory effect of ADAMTS13 during heart injury. Our data show that ADAMTS13 reduces myocardial ischemia/reperfusion injury in mice and indicate that rhADAMTS13 could be of therapeutic value to limit myocardial ischemia/reperfusion injury.

Blockade of self-reactive IgM significantly reduces injury in a murine model of acute myocardial infarction.

AIMS: Coronary artery occlusion resulting in ischaemia/reperfusion (I/R) injury is a major cause of mortality in the western world. Circulating natural IgM has been shown to play a significant role in reperfusion injury, leading to the notion of a pathogenic response against self by the innate immune system. A specific self-antigen (non-muscle myosin heavy chain II) was recently identified as the major target of pathogenic natural IgM. Therefore, we hypothesized that a synthetic peptide mimetope (N2) or monoclonal antibodies directed against the self-antigen would prevent specific IgM binding to the self-antigen and reduce reperfusion injury in the heart. METHODS AND RESULTS: We find that treatment with N2 peptide reduces infarct size by 47% and serum cardiac troponin-I levels by 69% following 1 h ischaemia and 24 h reperfusion. N2 peptide or an anti-N2 F(ab')(2) (21G6) is also effective at preventing IgM and complement deposition. Additionally, N2 peptide treatment significantly reduces monocyte and neutrophil infiltration at 24 h and collagen deposition at 5 days. Finally, we show that human IgM (hIgM) also includes specificity for the highly conserved self-antigen and that myocardial injury in antibody-deficient mice reconstituted with hIgM is blocked by treatment with N2 peptide or 21G6 F(ab')(2). CONCLUSION: The findings in this study identify potential therapeutics [i.e. N2 peptide or 21G6 F(ab')(2)] that prevent specific IgM binding to ischaemic antigens in the heart, resulting in a significant reduction in cardiac I/R injury.