The human checkpoint genes PD-1 and PD-L1 have been the target of extensive research for the treatment of human malignancies. Checkpoint inhibitor therapy has shown great promise in the clinic. Animal models that can use the human clinical antibodies will be beneficial for evaluating new therapies. A novel transgenic mouse model was developed that expresses the human PD-1 and PD-L1 in place of the murine genes. Additionally, a murine MC38 colon tumor cell line was modified to express human PD-L1. We evaluated the efficacy of human check point antibodies nivolumab, pembrolizumab, and atezolizumab in the transgenic animal model with modified MC38 colon cancer cells. Five hundred thousand transgenic MC38 cells were implanted in the C57BL/6 PD-1/PD-L1 knock in mice and allowed to grow for three days. The tumor-implanted mice were treated with nivolumab and pembrolizumab at 100 μg per animal and atezolizumab at 1 mg per animal on Days 3, 7, 10, and 14. Treatment with nivolumab and pembrolizumab caused tumor regression by Day 17. Growth inhibition was 84%, 58%, and 94% on Day 17 for nivolumab, atezolizumab, and pembrolizumab, respectively, compared to the control animals. There was no significant body weight loss and no signs of toxicity in any of the treated animals. We have shown that both PD-1 and PD-L1 inhibitors are effective in treating genetically modified MC38 colon tumors in transgenic mice. Further research will involve combining each of the checkpoint antibodies with various chemotherapeutic agents. Citation Format: Murray Stackhouse, Ted Green, Jay Liu, Charlotte Hammond, LaJuana Durbin, Anna Chen, Mike Koratich. Efficacy of nivolumab, pembrolizumab, and atezolizumab against MC38 colon cancer expressing human PD-1 in transgenic C57BL/6 mice expressing human PD-1 and PD-L1 checkpoint genes [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B81.
Human checkpoint genes PD-1 and PD-L1 are the target of extensive research for treating human cancers. Checkpoint inhibitor therapy shows great promise in the clinic. Combining checkpoint inhibitors with standard chemotherapeutic agents is an important for these inhibitors. Animal models that use human clinical antibodies and chemotherapeutic agents will be beneficial for evaluating new therapies. A novel transgenic mouse model is described that expresses human PD-1 and PD-L1 in place of the murine genes. Additionally, a murine MC38 colon tumor cell line was modified to express human PD-L1. We initially evaluated early treatment efficacy of human check point antibodies nivolumab, pembrolizumab, and atezolizumab in the transgenic animal model with modified MC38 colon cancer cells. Five hundred thousand transgenic MC38 cells were implanted in the C57BL/6 PD-1/PD-L1 knock in mice and allowed to grow for three days. Tumor-implanted mice were treated with nivolumab and pembrolizumab at 100 µg per animal and atezolizumab at 1 mg per animal on Days 3, 7, 10, and 14. Treatment with nivolumab and pembrolizumab caused tumor regression by Day 17. Growth inhibition was 84%, 58%, and 94% on Day 17 for nivolumab, atezolizumab, and pembrolizumab, respectively, compared to the control animals. There was no significant body weight loss and no signs of toxicity in any of the treated animals. To extend the utility of the model we implanted mice and allowed the tumors to grow to 63 to 126 mg before treatment initiation (Day 10). Similar results were observed in established tumors as for early treatment with the PD-1 inhibitors nivolumab and pembrolizuman. In contrast there was little activity from the PD-L1 inhibitor atezolizumab in established tumors. To prepare for combination studies, we also tested cisplatin, irinotecan, gemcitabine, decitabine, rucaparib, and thiarabine near the MTD for each agent with various treatment schedules against the established tumors. The doses for cisplatin, irinotecan and decitabine resulted in excess animal deaths and require reduced doses for combination therapies. Gemcitabine, decitabine, and thiarabine (in house development drug) were too active with complete regressions observed; the doses for combination treatment will be reduced. Due to the effectiveness of the PD-1 checkpoint inhibitors the number of doses will be reduced from four to two treatments in combination studies; no change for atezolizumab. We have shown that PD-1 inhibitors are effective in treating genetically modified MC38 colon tumors in transgenic mice in early treatment and in established tumors while the PD-L1 inhibitor was only effective in early treatment. We also have identified doses and schedules of five chemotherapeutic agents to use in future combination studies in this model. Citation Format: Murray A. Stackhouse, Ted Green, Jay Liu, Charlotte Hammond, LaJuana Durbin, Ana Chen, Jerry Zhou, Mike Koratich. Efficacy of three checkpoint Inhibitors, five chemotherapeutic agents, and the experimental drug thiarabine against MC38 colon cancer expressing human PD-L1 in transgenic C57BL/6 mice expressing human PD-1 and PD-L1 checkpoint genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4087.
The human checkpoint targets PD-1 and PDL-1 continue to demonstrate great promise in the clinic. With much of the current focus turning toward combination regiments, an animal model using the human clinical antibodies will be beneficial for evaluating new combination strategies. Here we continue characterization of a C57BL/6 transgenic mouse model expressing both the human PD-1 and PD-L1 combined with a modified murine MC38 colon tumor cell line expressing human PD-L1. Both PD-1 and PD-L1 expression of the transgenic mice were verified in ex vivo stimulated splenocytes by flow cytometry analysis. Expression of PD-L1 on the genetically modified MC38 cells was also demonstrated by flow cytometry. For in vivo efficacy evaluation, tumor-implanted mice were treated with the clinical agents nivolumab and pembrolizumab at 100 µg and atezolizumab at 1 mg on Days 3, 7, 10, and 14 post implant. Treatment with nivolumab and pembrolizumab initiated tumor regression by Day 17. Complete tumor regressions were seen at Day 28 in nivolumab, 62.5% complete regression, and pembrolizumab, 71.4% complete regression. Growth inhibition was 83.9%, 69.7%, and 95.0% on Day 28 for nivolumab, atezolizumab, and pembrolizumab, respectively, compared to the control animals. There was no significant body weight loss and no signs of toxicity in any of the treated animals. To compare the human anti-PD-1 and PD-L1 clinical agent specificity, the non-transgenic parent C57BL/6 mouse strain was implanted with the unmodified MC38 colon tumor cells. Treatment with pembrolizumab and atezolizumab was conducted as with the transgenic animals. Through 28 days no growth inhibition, tumor size 105.9% of control, was seen in the pembrolizumab treated group, demonstrating lack of cross reactivity of the human therapeutic in the standard mouse model. Atezolizumab did demonstrate a 56.9% growth inhibition compared to controls and is consistent with the known cross reactivity of atezolizumab between human and mouse. We have shown a genetically modified MC38 colon tumor expressing human PD-L1 in transgenic mice expressing both human PD-1 and PD-L1 to be a suitable model for checkpoint inhibitor evaluation of the human form of the particular checkpoint therapeutic. Further research will involve combining each of the checkpoint antibodies with various chemotherapeutic agents. Citation Format: Michael Koratich, Ted Green, Jie Liu, Charlotte Hammond, LaJuana Durbin, Jerry Zhou, Anna Chen, Murray Stackhouse. Characterization of a MC38 mouse syngeneic tumor model expressing human PD-L1 in the transgenic C57BL/6 mouse system expressing human PD-1 and PD-L1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1504.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.