Summary

Purpose/Objectives: Although treatment of high-dose (HD) radiation (XRT) and NBTXR3 (R3) on primary tumors in combination with systemic anti-PD1 was able to significantly improve abscopal effect in 344SQR murine metastatic lung cancer, most of the mice eventually expired due to the growth of metastatic tumors. Therefore, we studied the effects of R3 injection into primary tumors plus high-dose radiation on primary tumor and low-dose raditionon metastatic tumor plus dual-agent immunotherapy (IT) of anti-PD1 and anti-CTLA-4 to achive complete control of tumor growth at both the primary and the metastatic tumors in mice.

Materials/Methods: Five groups of 8 mice each were inoculated subcutaneously with 5×104 anti-PD1-resistant 344SQR murine lung cancer cells in each hind leg, 3 days apart, to establish ‘primary’ (right) and ‘metastatic’ (left) tumors. All mice in treatment groups received intraperitoneal anti-PD1 and anti-CTLA-4 on days 4, 7, 10, and 13, and contining anti-PD1 treatment on days 20, 27, 34, 41, and 49 and 12-Gy high-dose (HD) XRT to the primary tumors on days 7, 8 and 9. Primary tumors in groups 3 and 5 also received intratumoral R3 on day 6. Metastatic tumors in groups 4 and 5 were also irradiated with 1-Gy low-dose (LD) XRT on days 12 and 13 (Radscopal™ approach). Experimetal groups were designated as 1=Control, 2=HD+IT, 3=R3+HD+IT, 4=HD+LD+IT, and 5=R3+HD+LD+IT. On day 178, the right flank of the survived mice in group 5 was rechallenged with 5×104 344SQR cells and the tumor growth was monitored.

Results: All the mice in groups 1, 2, 3, 4 expired due to the growth of either the primary tumor or the metastatic tumor by day 36. Both the primary and the metastatic tumors in 4 mice of group 5 were completely eliminated. No tumor growth was observed in the 4 survived mice which was rechallenged with 344SQR cells. It was also found that the mice in group 5 had significantly fewer spontaneous lung metastases than the mice in any other groups. Nanostring data for the metastatic tumor collected on day 19 demonstrated that all the treatments group had significant upregulation of major anti-tumor immune pathways than the control. In addition, R3 nanoparticle exhibited stronger immune activation in mice than the ones without it. The flow cytometry data for the metastatic tumors collected on day 16 demonstrated that only the mice in group 3 and 5 showed significantly more CD8+ T cell infiltration in the metastatic tumor than the control group. Both flow cytometry and Nanostring data showed that only the mice received R3+HD+LD+IT treatment had significantly higher CD8+ Tcell/Treg cell ratio than the control group.

Conclusions: The combination of R3+HD+LD+IT could effectively eliminate the growth of both the primary and the metastasized tumors, significantly extend the survival of the treated mice, and create long-term immune memory against tumor cells. The combination therapy was able to contribute the immune-mediated control of the metastasized tumor at both genetic and cellular levels.

Summary

Immunotherapy Workshop: Bethesda, MD, June 15-16, 2017

Radiotherapy (RT) has proven its ability to function like an in-situ vaccine, showing potential for successful combination with immunotherapeutic agents. Hafnium oxide nanoparticle (HfO2-NP), undergoing clinical trials for enhancing RT, was designed as high electron density material at the nanoscale. HfO2-NPs are taken up by cancer cells and, when exposed to RT, locally increase the radiation dose deposit, triggering more cancer cells death when compared to RT. We hypothesized that HfO2-NP+RT could trigger an enhanced immune response when compared to RT, both in preclinical and clinical settings.

Summary

Combination of NBTXR3 and cisplatin has been evaluated in vitro and in vivo. No specific toxicity was observed for the cells exposed only to NBTXR3. For the combined treatment, a marked and enhanced cell destruction when compared to the single agent. In vivo, NBTXR3 combined with low dose of cisplatin delayed tumor growth when compared to single agent cisplatin in combination with radiotherapy.

Summary

Radio-enhancers, metal-based nanosized agents, could play a key role in oncology. They may unlock the potential of radiotherapy by enhancing the radiation dose deposit within tumors when the ionizing radiation source is ‘on’, while exhibiting chemically inert behavior in cellular and subcellular systems when the radiation beam is ‘off’. Important decision points support the development of these new type of therapeutic agents originated from nanotechnology. Here, we discuss from an industry perspective, the interest of developing radio-enhancer agents to improve tumor control, the relevance of nanotechnology to achieve adequate therapeutic attributes, and present some considerations for their development in oncology.

Summary

Background: Hafnium oxide, NBTXR3 nanoparticles were designed for high dose energy deposition within cancer cells when exposed to ionizing radiation. The purpose of this study was to assess the possibility of predicting the in vitro the biological effect of NBTXR3 nanoparticles when exposed to ionizing radiation.

Methods: Cellular uptake of NBTXR3 nanoparticles was assessed in a panel of human cancer cell lines (radioresistant and radiosensitive) by transmission electron microscopy. The radioenhancement of NBTXR3 nanoparticles was measured by the clonogenic survival assay.

Results: NBTXR3 nanoparticles were taken up by cells in a concentration dependent manner, forming clusters in the cytoplasm. Differential nanoparticle uptake was observed between epithelial and mesenchymal or glioblastoma cell lines. The dose enhancement factor increased with increase NBTXR3 nanoparticle concentration and radiation dose. Beyond a minimum number of clusters per cell, the radioenhancement of NBTXR3 nanoparticles could be estimated from the radiation dose delivered and the radiosensitivity of the cancer cell lines.

Conclusions: Our preliminary results suggest a predictable in vitro biological effect of NBTXR3 nanoparticles exposed to ionizing radiation.