The malaria protein VAR2CSA binds oncofetal chondroitin sulfate (ofCS), a unique chondroitin sulfate, expressed on almost all mammalian cancer cells. Previously, we produced a bispecific construct targeting ofCS and human T cells based on VAR2CSA and anti-CD3 (V-aCD3Hu). V-aCD3Hu showed efficacy against xenografted tumors in immunocompromised mice injected with human immune cells at the tumor site. However, the complex effects potentially exerted by the immune system as a result of the treatment cannot occur in mice without an immune system. Here we investigate the efficacy of V-aCD3Mu as a monotherapy and combined with immune checkpoint inhibitors in mice with a fully functional immune system.We produced a bispecific construct consisting of a recombinant version of VAR2CSA coupled to an anti-murine CD3 single-chain variable fragment. Flow cytometry and ELISA were used to check cell binding capabilities and the therapeutic effect was evaluated in vitro in a killing assay. The in vivo efficacy of V-aCD3Mu was then investigated in mice with a functional immune system and established or primary syngeneic tumors in the immunologically "cold" 4T1 mammary carcinoma, B16-F10 malignant melanoma, the pancreatic KPC mouse model, and in the immunologically "hot" CT26 colon carcinoma model.V-aCD3Mu had efficacy as a monotherapy, and the combined treatment of V-aCD3Mu and an immune checkpoint inhibitor showed enhanced effects resulting in the complete elimination of solid tumors in the 4T1, B16-F10, and CT26 models. This anti-tumor effect was abscopal and accompanied by a systemic increase in memory and activated cytotoxic and helper T cells. The combined treatment also led to a higher percentage of memory T cells in the tumor without an increase in regulatory T cells. In addition, we observed partial protection against re-challenge in a melanoma model and full protection in a breast cancer model.Our findings suggest that V-aCD3Mu combined with an immune checkpoint inhibitor renders immunologically "cold" tumors "hot" and results in tumor elimination. Taken together, these data provide proof of concept for the further clinical development of V-aCD3 as a broad cancer therapy in combination with an immune checkpoint inhibitor.
Broad-spectrum therapeutics in non-small cell lung cancer (NSCLC) are in demand. Most human solid tumors express proteoglycans modified with distinct oncofetal chondroitin sulfate (CS) chains that can be detected and targeted with recombinant VAR2CSA (rVAR2) proteins and rVAR2-derived therapeutics. Here, we investigated expression and targetability of oncofetal CS expression in human NSCLC. High oncofetal CS expression is associated with shorter disease-free survival and poor overall survival of clinically annotated stage I and II NSCLC patients (n = 493). Oncofetal CS qualifies as an independent prognosticator of NSCLC in males and smokers, and high oncofetal CS levels are more prevalent in EGFR/KRAS wild-type cases, as compared to mutation cases. NSCLC cell lines express oncofetal CS-modified proteoglycans that can be specifically detected and targeted by rVAR2 proteins in a CSA-dependent manner. Importantly, a novel VAR2-drug conjugate (VDC-MMAE) efficiently eliminates NSCLC cells in vitro and in vivo. In summary, oncofetal CS is a prognostic biomarker and an actionable glycosaminoglycan target in NSCLC.
Molecular similarities between embryonic and malignant cells can be exploited to target tumors through specific signatures absent in healthy adult tissues. One such embryonic signature tumors express is oncofetal chondroitin sulfate (ofCS), which supports disease progression and dissemination in cancer. Here, we report the identification and characterization of phage display-derived antibody fragments recognizing two distinct ofCS epitopes. These antibody fragments show binding affinity to ofCS in the low nanomolar range across a broad selection of solid tumor types in vitro and in vivo with minimal binding to normal, inflamed, or benign tumor tissues. Anti-ofCS antibody drug conjugates and bispecific immune cell engagers based on these targeting moieties disrupt tumor progression in animal models of human and murine cancers. Thus, anti-ofCS antibody fragments hold promise for the development of broadly effective therapeutic and diagnostic applications targeting human malignancies.
Abstract Proteoglycans are proteins that are modified with glycosaminoglycan chains. Chondroitin sulfate proteoglycans (CSPGs) are currently being exploited as targets for drug-delivery in various cancer indications, however basic knowledge on how CSPGs are internalized in tumor cells is lacking. In this study we took advantage of a recombinant CSPG-binding lectin VAR2CSA (rVAR2) to track internalization and cell fate of CSPGs in tumor cells. We found that rVAR2 is internalized into cancer cells via multiple internalization mechanisms after initial docking on cell surface CSPGs. Regardless of the internalization pathway used, CSPG-bound rVAR2 was trafficked to the early endosomes in an energy-dependent manner but not further transported to the lysosomal compartment. Instead, internalized CSPG-bound rVAR2 proteins were secreted with exosomes to the extracellular environment in a strictly chondroitin sulfate-dependent manner. In summary, our work describes the cell fate of rVAR2 proteins in tumor cells after initial binding to CSPGs, which can be further used to inform development of rVAR2-drug conjugates and other therapeutics targeting CSPGs.
We have recently identified lens epithelium-derived growth factor (LEDGF/p75, also known as PSIP1) as a component of the homologous recombination DNA repair machinery. Through its Pro-Trp-Trp-Pro (PWWP) domain, LEDGF/p75 binds to histone marks associated with active transcription and promotes DNA end resection by recruiting DNA endonuclease retinoblastoma-binding protein 8 (RBBP8/CtIP) to broken DNA ends. Here we show that the structurally related PWWP domain-containing protein, hepatoma-derived growth factor-related protein 2 (HDGFRP2), serves a similar function in homologous recombination repair. Its depletion compromises the survival of human U2OS osteosarcoma and HeLa cervix carcinoma cells and impairs the DNA damage-induced phosphorylation of replication protein A2 (RPA2) and the recruitment of DNA endonuclease RBBP8/CtIP to DNA double strand breaks. In contrast to LEDGF/p75, HDGFRP2 binds preferentially to histone marks characteristic for transcriptionally silent chromatin. Accordingly, HDGFRP2 is found in complex with the heterochromatin-binding chromobox homologue 1 (CBX1) and Pogo transposable element with ZNF domain (POGZ). Supporting the functionality of this complex, POGZ-depleted cells show a similar defect in DNA damage-induced RPA2 phosphorylation as HDGFRP2-depleted cells. These data suggest that HDGFRP2, possibly in complex with POGZ, recruits homologous recombination repair machinery to damaged silent genes or to active genes silenced upon DNA damage.
Abstract Infantile neuronal ceroid lipofuscinosis (CLN1 Batten Disease) is a devastating pediatric lysosomal storage disease caused by pathogenic variants in the CLN1 gene, which encodes the depalmitoylation enzyme, palmitoyl-protein thioesterase 1 (PPT1). CLN1 patients present with visual deterioration, psychomotor dysfunction, and recurrent seizures until neurodegeneration results in death, typically before fifteen years of age. Histopathological features of CLN1 include aggregation of lysosomal autofluorescent storage material (AFSM), as well as profound gliosis. The current management of CLN1 is relegated to palliative care. Here, we examine the therapeutic potential of a small molecule PPT1 mimetic, N-tert-butyl hydroxylamine (NtBuHA), in a Cln1 −/− mouse model. Treatment with NtBuHA reduced AFSM accumulation both in vitro and in vivo. Importantly, NtBuHA treatment in Cln1 −/− mice reduced neuroinflammation, mitigated epileptic episodes, and normalized motor function. Live cell imaging of Cln1 −/− primary cortical neurons treated with NtBuHA partially rescued aberrant synaptic calcium dynamics, suggesting a potential mechanism contributing to the therapeutic effects of NtBuHA in vivo. Taken together, our findings provide supporting evidence for NtBuHA as a potential treatment for CLN1 Batten Disease.
Additional file 1: Sup. Fig. 1. (A) ELISA showing binding of V-aCD3Mu (Coupled)(Kd = 38.8, Bmax = 3.31), rVAR2 (Kd and Bmax not determined), and V-aCD3Mu (Fused)(Kd = 14.2, Bmax = 3.36) to CSPG on a decorin backbone. Data is representative of a minimum of two separate experiments. (B) Solid 4T1 tumors 50-100 mm3 in size were treated with either PBS (n=5), V-aCD3Mu (Coupled) + CpG (n=8), or V-aCD3Mu (Fused) + CpG (n=8) on day 10, 12, 14, and 17 after tumor injection. Numbers in parentheses indicate the number of animals with complete tumor regression out of all mice in the group. Sup. Fig. 2. (A) Gating strategy on splenocytes and PBMCs in flow cytometry used to determine binding of rVAR2, aCD3Mu, V-aCD3Mu, aCD3Hu, and anti-V5 antibodies to T cells and non-T cell splenocytes/PBMCs. The gating is single cells lymphocytes live cells CD4+ and/or CD8+ cells as T cells and CD4-CD8- cells as non-T cells. The geometric MFI of the anti-penta-HIS antibodies conjugated to Alexa Flour 488 was then used to evaluate the binding of the HIS-tagged proteins. (B) Binding of aCD3Mu (Kd = 4.96, Bmax = 1.05), rVAR2 (Kd = NR, Bmax = 0.46), and V-aCD3Mu (Kd = 1.24, Bmax = 3.38) to murine recombinant CD3 in ELISA with aCD4Mu as a negative control (left). Means and standard deviations are shown. Right pane shows CSA inhibition of binding at 120 nM (right). Each dot represents one data point. Sup. Fig. 3. Cytokines measured from 4T1 and splenocyte co-culture supernatants using ELISA. Mouse splenocytes were incubated with 4T1 cancer cells together with 200 nM of the indicated protein. Sup. Fig. 4. (A) Survival curves for mice with indicated tumors treated as described in Fig. 4. The cut-off for all Kaplan-Meier plots is a tumor volume of $$\ge$$ ≥ 400 mm3. Mice were censored if they had to be excluded from the study prematurely due to reasons other than tumor size. Log-rank test was used for statistical analysis. *p < 0.05. (B) Bioluminescence in vivo imaging of C57BL/6 mice following orthotopic implantation of 5x104 Luciferase+ primary pancreatic cancer cells (CHX2000) derived from KPC mice (LSL-KrasG12D/+; p53f/f; Pdx1-Cre). Sup. Fig. 5. (A-C) Survival curves for mice treated as described in Fig. 5. The cut-off for all Kaplan-Meier plots is a tumor volume of $$\ge$$ ≥ 400 mm3. Mice were censored if they had to be excluded from the study prematurely due to reasons other than tumor size. Log-rank test was used for statistical analysis. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Sup. Fig. 6. (A) Treatment schedule until day 14 when spleens and tumors were harvested for flow cytometry and the subsequent gating strategy on splenocytes to evaluate different cell types in C-D. (B) Percentage of live cells relative to the PBS group in the spleen. Both CD8+ and CD4+ T cells that are CD69+, CD44hi, CD8+CD25+, or Tregs are shown. (C) UMAPs of splenocytes from all four treatment groups with clustering performed in ClusterExplorer. Cell types in clusters are explained below. Statistics were performed using one-way ANOVA with Dunnett’s post hoc test for comparison of all treatment groups to the PBS group. P values are indicated if significant or important for reading the figure. (D) Correlations between the tumor size and �8+CD69+ (p=0.67) and �4+CD69+ (p=0.14) of all live single cells in the tumor evaluated by simple linear regression. Sup. Fig. 7. Binding of mouse antibodies to 4T1 cells and B16-F10 cells in flow cytometry. Serum from C57BL/6 mice treated as described in materials and methods was diluted as illustrated on the figure and incubated with 200.000 4T1 or B16-F10 cells. Soluble CSA was added if indicated for 1 hour before detection with an anti-mouse IgG antibody conjugated to FITC.
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