Date of Graduation
Doctor of Philosophy (PhD)
Dr. Eugenie Kleinerman
Dr. Nancy Gordon
Dr. Zahid Siddik
Dr. Michael Curran
Dr. Gheath Al-Atrash
Dr. Sonal Gupta
Osteosarcoma (OS) manifests itself as pulmonary metastasis, which is a major cause of death in OS patients. Novel treatments like immunotherapy hold promise for the treatment of OS pulmonary metastasis. However, immunosuppressive mechanisms such as binding of immune inhibitory receptor, PD-1 with PDL-1, which is upregulated in cancer cells, may cause disease relapse.
The effect of PD-1 blockade on NK cells and macrophages has not been investigated till date. The aim of this study was to determine if PD-1 blockade leads to of OS lung metastasis regression and study the role of NK cells and/or macrophages in the anti-PD-1 responses. We demonstrated that PDL-1 is expressed in human OS cell lines and in lung metastases from OS patients, implying that its importance as a potential therapeutic target in OS. Further, in vivo anti-murine-PD-1 administration led to a significant decrease in the number of OS lung metastases using a human LM7 OS mouse model. Also, there was a significant increase in tumor cell apoptosis and decrease in tumor cell proliferation after in vivo anti-PD-1 treatment. In addition, anti-PD-1 led to blockade of p-STAT3/p-Erk1/2 and PDL-1 signaling in OS lung tumors.
We discovered that PD-1 was expressed on NK cells and macrophages in OS lung tumors. Increased infiltration of NK cells and macrophages was observed within OS lung metastatic tumors after anti-PD-1 treatment. Particularly, anti-PD-1 caused an increase in the anti-tumor M1 macrophages and decrease in numbers of pro-inflammatory M2 macrophages in OS lung metastases. We further investigated the implication of NK cells and macrophages in the therapeutic efficacy of anti-PD-1 against OS lung metastases. NK cell depletion using anti-asialo-GM1 did not affect the efficacy of anti-PD-1. Hence, NK cells were not the crucial immune cells involved in anti-tumor responses of anti-PD-1. However, macrophage depletion using Clodrosome prior to anti-PD-1 treatment significantly compromised the regression of OS lung metastasis. Our results implied that macrophages are the crucial mediators of the anti-tumor responses of anti-PD-1 against OS lung metastasis. Overall, our data suggests that PD-1 blockade with anti-PD-1 leads to regression of OS lung metastases, primarily through activation of macrophages.
Programmed death ligand 1 (PDL-1), osteosarcoma, lung metastasis, immunotherapy, macrophages