Therapy model for advanced intracerebral B16 mouse melanoma using radiation therapy combined with immunotherapy

Abstract

A reproducible therapy model for advanced intracerebral B16 melanoma is reported. Implanted tumors (D0), suppressed by a single 15 Gy radiosurgical dose of 100 kVp X-rays (D8), were further suppressed by a single ip injection of a Treg-depleting mAb given 2 days prior to the initiation (D9) of four weekly then eight bi-monthly sc injections of GMCSF-transfected, mitotically disabled B16 cells. The trends of seven independent experiments were similar to the combined result: The median (days) [SD/total N] of survival went from 15[1.09/62] (no treatment control) to 35.8[8.8/58] (radiation therapy only) to 52.5[13.5/57] (radiation therapy plus immunotherapy). Within 2 weeks after immunization, tumors in mice receiving radiation therapy plus immunotherapy were significantly smaller than tumors in mice treated only with radiosurgery. Splenocytes and lymph node cells from immunized mice showed increased interferon γ production when cultured with syngeneic tumor cells. We suggest that our model will be useful for the development and testing of novel combination therapies for brain tumors.

Quality Assessment of Stereotactic Radiosurgery of a Melanoma Brain Metastases Model Using a Mouselike Phantom and the Small Animal Radiation Research Platform

“…[16,17] To establish the intracranial orthotopic brain metastases model for melanoma without the usage of pre-irradiated disabled cells, we initially used GFP labeled B16-F10 cells (B16-F10-GFP). B16-F10-GFP cells were injected into the brain and MRI T1-post contrast series were obtained to observe tumor growth.…”

“…Prior intracranial studies using B16 melanoma syngeneic models used melanoma cells mixed with pre-irradiated disabled cells for intracranial implantation. [16,17] In contrast, this current model does not require additional pre-irradiated cells for intracranial tumor formation. Initially, we used GFP tagged B16 cell lines to develop the model; however, with the goal of adaptation to immunotherapy based research applications, all subsequent studies used wildtype B16 cells to avoid antigenicity of GFP.…”

The Role of Lymphocytes in Radiotherapy-Induced Adverse Late Effects in the Lung

“…Still, further studies are needed to strengthen these results with respect to radiation-induced (pulmonary) fibrosis. The above findings of Xiong et al are of particular interest because several studies highlight the potential importance of T reg depletion in enhancing antitumor immunity during RT (241, 242). One major challenge in targeting T reg will be defining the optimal treatment schedule, since T reg might also be beneficial in counteracting exaggerated inflammation during the pneumonitic phase (142).…”

Regulatory T Cells in Autoimmunity and Cancer: A Duplicitous Lifestyle

“…Considering the above, recent therapeutic attempts have been focused on the manipulation of Treg cell-mediated immunosuppression in order to enhance anti-tumor immune responses and improve the clinical outcome of cancer patients. Several strategies for targeting tumor associated Treg cells may involve either direct or indirect approaches, that have been tested clinically or/and preclinically, such as: a. the CD25 targeting for Treg cell depletion with either blocking antibodies or a recombinant protein composed of IL-2 and the active domain of the diphtheria toxin (127,(182)(183)(184)(185)(186)(187), b. the targeting of Tregspecific co-inhibitory molecules (CTLA-4, PD-1, TIGIT, VISTA, TIM-3, LAG-3) (188)(189)(190)(191), with blocking antibodies to specifically deplete or diminish the suppressive function of Treg cells in the TME (143,(192)(193)(194)(195)(196), c. The usage of agonists against GITR (197)(198)(199), OX-40 (200,201) and ICOS (202) can drive the attenuation of Treg cell immunosuppressive activity (203), d. targeting of PI3K signaling (204) or molecules like CD39 and CD73-critical regulators of adenosine pathway (205)which are definitive of Treg cells behavior in the TME, e. inhibition of vascular endothelial growth factor (VEGF)-VEGF receptor 2 (VEGF-VEFGFR2) pathway, which is implicated in the accumulation of Treg cells, reduced their infiltration to the TME (206,207), f. inhibition of TGF-b pathway, a major mediator of Treg presence in the TME, can diminish the induction of Treg cells (208,209).…”