Orthotopic Murine Cancer Model Research Articles

Abstract 2917: Tumor eradication with T-cells targeted with multivalent chemically self-assembled nanorings

Abstract Due to the heterogeneity of cellular dependences on signaling pathways and the potential development of drug resistance, there is an emerging recognition that future cancer therapy will require individualized drug combinations to produce long term remission. In addition, to truly address metastasis and relapse, methods of targeting quiescent tumor initiating cancer stem cells (CSC), which are resistant to chemotherapy and radiation, is of critical importance. Consequently, new methods that can target both primary tumor cells and CSC are needed. Previously, our group has shown that two dihydrofolate reductase molecules (DHFR2) fused to distinct targeting ligands can spontaneously self-assemble upon the addition of a chemical dimerizer (bis-methotrexate (BisMTX)) into highly stable, multivalent, chemically self-assembled nanorings (CSANs). When an anti-CD3 scFv is fused, the bispecific CSANs rapidly (min) and stably (days) bind to CD3 on T-cell membranes. Consequently, we refer to the modified T-cells as Prosthetic Antigen Receptor (PAR) T-cells. A unique feature of our approach is the ability to remove the CSANs from the T-cells by incubation with the FDA-approved antibiotic trimethoprim, allowing us to deactivate the modified cells pharmacologically. In addition, we have shown that the CSANs have negligible immunogenicity in mice and do not induce naïve human T-cell anergy (i.e, unresponsiveness).Recently, we have prepared anti-EpCAM/anti-CD3 CSANs, which target triple negative cancer (TNBC) primary tumor cells, and anti-CD133/anti-CD3-CSANs, which target TNBC cancer stem cells. The bispecific CSANs rapidly (min) and stably (days) bind to CD3 on T-cell membranes, thus either anti-EpCAM or anti-CD133 PAR T-cells. Upon incubation of CD133+ or EpCAM+ TNBC cells with the CSANs rapid and selective cell killing was observed. We have also demonstrated with an orthotopic murine cancer model that anti-EpCAM CSANs significantly reduce tumor size, while anti-CD133 CSANs block tumor proliferation. When dosed with a combination of anti-EpCAM CSANs and anti-CD133 CSANs tumor T-cell induced eradication of the tumors is observed. Further analysis revealed that initial tumor growth kinetics is dependent on the percentage of CD133+ tumor cells and that regardless of the starting point, the number of CD133+ tumor cells reaches a homeostatic percentage in the tumor. Whether CD133+ tumor cells arise from self-renewal or de-differentiation is yet to be determined. Regardless, dosing with either CSANs was found to be non-toxic. Taken together, our results demonstrate that CSAN modified T-cells targeting both primary tumor and CSC are necessary for TNBC tumor eradication and that CD133+ TNBC tumor cells maybe be necessary and sufficient for TNBC tumor initiation and proliferation. Citation Format: Carston R. Wagner. Tumor eradication with T-cells targeted with multivalent chemically self-assembled nanorings [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2917.

Synthesis of deoxyelephantopin analogues.

Deoxyelephantopin is a sesquiterpene lactone that was reported to be as effective in the treatment of mammary tumours and lung metastasis as taxol based on a murine orthotopic cancer model. Its germacrene skeleton harbours three Michael acceptors that can potentially engage a target covalently. Its strained 10-membered ring is densely functionalised and represents an important synthetic challenge. We herein describe our studies towards deoxyelephantopins using a ring-closing metathesis approach and report some unexpected observations.

Vaccinia Virus GLV-1h153 Is Effective in Treating and Preventing Metastatic Triple-Negative Breast Cancer

This study aimed to investigate the therapeutic impact of a new oncolytic vaccinia virus in a triple-negative breast cancer (TNBC) murine model and its potential for treating distant metastatic disease. TNBCs are aggressive tumors associated with a high metastatic rate. Their lack of targets for hormonal/biological therapy presents significant clinical challenges and a dire need for novel therapies. GLV-1h153, a replication-competent vaccinia virus, was tested against multiple cell lines. Cytotoxicity and viral replication were determined. Intratumoral (IT) or intravenous (IV) injection of GLV-1h153 (1 × 10(7) plaque-forming units) or phosphate buffered saline was tested in an orthotopic murine model, which reliably produces systemic metastasis. Tumors, lymph nodes, and metastatic organs (lung, liver, and brain) were harvested 5 and 8 weeks after treatment and prepared for histopathological review. Demonstration of metastasis was performed using immunofluorescence and hematoxylin and eosin (H&E) staining. GLV-1h153 infected, replicated in, and killed all TNBC cell lines in vitro. In vivo, mean tumor volume 2 weeks after treatment was 22 (IT), 29 (IV) versus 245 mm(3) (control; P < 0.002). Five weeks after treatment, all harvested lymph nodes and organs showed no evidence of metastatic cells. All harvested tumors showed complete response to treatment, with only necrosis and fibrosis on H&E staining 8 weeks after treatment. This is the first study to demonstrate that TNBCs are killed by a novel vaccinia virus both in vitro and in vivo. Our results suggest that GLV-1h153 is a promising therapeutic agent for preventing and treating metastatic TNBC and warrants further clinical testing in patients.

Heme oxygenase-1 and its metabolites affect pancreatic tumor growth in vivo

BackgroundPancreatic cancer (PaCa) is a fatal human cancer due to its exceptional resistance to all current anticancer therapies. The cytoprotective enzyme heme oxygenase-1 (HO-1) is significantly overexpressed in PaCa and seems to play an important role in cancer resistance to anticancer treatment. The inhibition of HO-1 sensitized PaCa cells to chemo- and radiotherapy in vitro.Therefore, we investigated the effects of HO-1 and its metabolites biliverdin, carbon monoxide and iron on PaCa cells.PaCa cell lines with divergent HO-1 expression patterns were used in a murine orthotopic cancer model. HO-1 expression and activity was regulated by zinc (inhibition) and cobalt (induction) protoporphyrin. Furthermore, the influence of cellular HO-1 levels and its metabolites on effects of standard chemotherapy with gemcitabine was tested in vivo and in vitro.ResultsHigh HO-1 expression in PaCa cell lines was associated with increased chemoresistance in vitro. Chemoresistance to gemcitabine was increased during HO-1 induction in PaCa cells expressing low levels of HO-1. The inhibition of HO-1 activity in pancreatic tumors with high HO-1 boosted chemotherapeutic effects in vivo significantly. Furthermore, biliverdin and iron promoted PaCa resistance to chemotherapy. Consequently, specific iron chelation by desferrioxamine revealed profound anticancerous effects.ConclusionIn summary, the inhibition of HO-1 and the chelation of iron in PaCa cells were associated with increased sensitivity and susceptibility of pancreatic tumors to chemotherapy in vivo. The metabolites biliverdin and iron seem to be involved in HO-1-mediated resistance to anticancer treatment. Therefore, HO-1 inhibition or direct interference with its metabolites may evolve new PaCa treatment strategies.