Publications

Introduction Immunotherapy targeting PD-1/PD-L1 immune checkpoint inhibition (ICI) is efficacious in various solid and hematologic malignancies. However, the response rate to PD-1/PD-L1 therapy is only 15–35%. To obtain optimal clinical response to ICI therapies, a reliable assessment of tumor PD-L1 expression is needed to select appropriate patients, and a non-invasive imaging-based assessment of PD-L1 expression is critically needed. Although radiolabeled PET probes based on PD-L1 targeted therapeutic antibodies (e.g. atezolizumab) have shown encouraging results, there is concern that residual therapeutic antibody may compete for binding with the radiotracer thereby compromising imaging studies that follow treatment. Methods and results In this study, we used novel anti-PD-L1-B11 clone antibody known to bind to a different epitope of PD-L1 than the therapeutic antibodies to avoid potential saturation effects. The anti-PD-L1-B11 clone was radiolabeled with zirconium-89 and evaluated to detect PD-L1 expression in various in vitro and in vivo cancer model systems in comparison with [89Zr]Zr-DFO-NCS-atezolizumab. In vitro binding parameters of anti-PD-L1-B11 were like those of atezolizumab. [89Zr]Zr-DFO-NCS-anti-PD-L1-B11 clone showed favorable properties to [89Zr]Zr-DFO-NCS-atezolizumab in an in vivo breast cancer tumor model system with higher uptake in PD-L1 expressing tumors. Conclusion Our data demonstrates that [89Zr]Zr-DFO-NCS-anti-PD-L1-B11 exhibits excellent imaging properties for the assessment PD-L1 expression. The independent binding site of anti-PD-L1-B11 relative to therapeutic anti-PD-L1 antibodies may be advantageous for anti-PD-L1 therapy monitoring.

Consumption of Eurasian bovine meat and milk has been associated with cancer development, in particular with colorectal cancer (CRC). In addition, zoonotic infectious agents from bovine products were proposed to cause colon cancer (zur Hausen et al., 2009). Bovine meat and milk factors (BMMF) are small episomal DNA molecules frequently isolated from bovine sera and milk products, and recently, also from colon cancer (de Villiers et al., 2019). BMMF are bioactive in human cells and were proposed to induce chronic inflammation in precancerous tissue leading to increased radical formation: for example, reactive oxygen and reactive nitrogen species and elevated levels of DNA mutations in replicating cells, such as cancer progenitor cells (zur Hausen et al., 2018). Mouse monoclonal antibodies against the replication (Rep) protein of H1MSB.1 (BMMF1) were used to analyze BMMF presence in different cohorts of CRC peritumor and tumor tissues and cancer-free individuals by immunohistochemistry and Western blot. BMMF DNA was isolated by laser microdissection from immunohistochemistry-positive tissue regions. We found BMMF Rep protein present specifically in close vicinity of CD68+ macrophages in the interstitial lamina propria adjacent to CRC tissues, suggesting the presence of local chronic inflammation. BMMF1 (modified H1MSB.1) DNA was isolated from the same tissue regions. Rep and CD68+ detection increased significantly in peritumor cancer tissues when compared to tissues of cancer-free individuals. This strengthens previous postulations that BMMF function as indirect carcinogens by inducing chronic inflammation and DNA damage in replicating cells, which represent progress to progenitor cells for adenoma (polyps) formation and cancer.

Background There are few therapeutic options available for patients with B-cell acute lymphoblastic leukemia (B-ALL) relapsing as CD19– either after chemotherapy or CD19-targeted immunotherapies. CD22-chimeric antigen receptor (CAR) T cells represent an attractive addition to CD19-CAR T cell therapy because they will target both CD22+CD19– B-ALL relapses and CD19– preleukemic cells. However, the immune escape mechanisms from CD22-CAR T cells, and the potential contribution of the epitope binding of the anti-CD22 single-chain variable fragment (scFv) remain understudied. Methods Here, we have developed and comprehensively characterized a novel CD22-CAR (clone hCD22.7) targeting a membrane-distal CD22 epitope and tested its cytotoxic effects against B-ALL cells both in in vitro and in vivo assays. Results Conformational epitope mapping, cross-blocking, and molecular docking assays revealed that the hCD22.7 scFv is a high-affinity binding antibody which specifically binds to the ESTKDGKVP sequence, located in the Ig-like V-type domain, the most distal domain of CD22. We observed efficient killing of B-ALL cells in vitro, although the kinetics were dependent on the level of CD22 expression. Importantly, we show an efficient in vivo control of patients with B-ALL derived xenografts with diverse aggressiveness, coupled to long-term hCD22.7-CAR T cell persistence. Remaining leukemic cells at sacrifice maintained full expression of CD22, ruling out CAR pressure-mediated antigen loss. Finally, the immunogenicity capacity of this hCD22.7-scFv was very similar to that of other CD22 scFv previously used in adoptive T cell therapy. Conclusions We report a novel, high-affinity hCD22.7 scFv which targets a membrane-distal epitope of CD22. 4-1BB-based hCD22.7-CAR T cells efficiently eliminate clinically relevant B- CD22high and CD22low ALL primary samples in vitro and in vivo. Our study supports the clinical translation of this hCD22.7-CAR as either single or tandem CD22–CD19-CAR for both naive and anti-CD19-resistant patients with B-ALL.

It has been suggested that B-cell receptor (BCRs) stimulation by specific antigens plays a pathogenic role in diffuse large B-cell lymphoma (DLBCL). Here, it was the aim to screen for specific reactivities of DLBCL-BCRs in the spectrum of autoantigens and antigens of infectious origin. Arsenite resistance protein 2 (Ars2) was identified as the BCR target of 3/5 ABC-type DLBCL cell lines and 2/11 primary DLBCL cases. Compared to controls, Ars2 was hypo-phosphorylated exclusively in cases and cell lines with Ars2-specific BCRs. In a validation cohort, hypo-phosphorylated Ars2 was found in 8/31 ABC-type, but only 1/20 germinal center B cell (GBC)-like type DLBCL. Incubation with Ars2 induced BCR-pathway activation and increased proliferation, while an Ars2/ETA-toxin conjugate induced killing of cell lines with Ars2-reactive BCRs. Ars2 appears to play a role in a subgroup of ABC-type DLBCLs. Moreover, transformed DLBCL lines with Ars2-reactive BCRs still show growth advantage after incubation with Ars2. These results provide knowledge about the pathogenic role of a specific antigen stimulating the BCR pathway in DLCBL.