Medulloblastoma rendered susceptible to NK-cell attack by TGFβ neutralization

Abstract

Background Medulloblastoma (MB), the most common pediatric brain cancer, presents with a poor prognosis in a subset of patients with high risk disease, or at recurrence, where current therapies are ineffective. Cord blood (CB) natural killer (NK) cells may be promising off-the-shelf effector cells for immunotherapy due to their recognition of malignant cells without the need for a known target, ready availability from multiple banks, and their potential to expand exponentially. However, they are currently limited by immune suppressive cytokines secreted in the MB tumor microenvironment including Transforming Growth Factor β (TGF-β). Here, we address this challenge in in vitro models of MB. Methods CB-derived NK cells were modified to express a dominant negative TGF-β receptor II (DNRII) using retroviral transduction. The ability of transduced CB cells to maintain function in the presence of medulloblastoma-conditioned media was then assessed. Results We observed that the cytotoxic ability of nontransduced CB-NK cells was reduced in the presence of TGF-β-rich, medulloblastoma-conditioned media (21.21 ± 1.19% killing at E:T 5:1 in the absence vs. 14.98 ± 2.11% in the presence of medulloblastoma-conditioned media, n = 8, p = 0.02), but was unaffected in CB-derived DNRII-transduced NK cells (21.11 ± 1.84% killing at E:T 5:1 in the absence vs. 21.81 ± 3.37 in the presence of medulloblastoma-conditioned media, n = 8, p = 0.85. We also observed decreased expression of CCR2 in untransduced NK cells (mean CCR2 MFI 826 ± 117 in untransduced NK + MB supernatant from mean CCR2 MFI 1639.29 ± 215 in no MB supernatant, n = 7, p = 0.0156), but not in the transduced cells. Finally, we observed that CB-derived DNRII-transduced NK cells may protect surrounding immune cells by providing a cytokine sink for TGF-β (decreased TGF-β levels of 610 ± 265 pg/mL in CB-derived DNRII-transduced NK cells vs. 1817 ± 342 pg/mL in untransduced cells; p = 0.008). Conclusions CB NK cells expressing a TGF-β DNRII may have a functional advantage over unmodified NK cells in the presence of TGF-β-rich MB, warranting further investigation on its potential applications for patients with medulloblastoma.

Immune cell infiltration and cytokine secretion analysis reveal a non-inflammatory microenvironment of medulloblastoma

“…Although the overall expression of cytokines is very low, exogenous administration of cytokines or inhibitors may be a useful target for immunotherapy. For example, TGF-β neutralization facilitated NK-cell induces MB suppression ( 38 ).…”

Innovative and Promising Strategies to Enhance Effectiveness of Immunotherapy for CNS Tumors: Where Are We?

“…GBM cells do express several activator ligand for NK receptors, as for example MHC class I polypeptide-related sequence A (MICA) (29) ligand for NKG2D + present on NK cells, as well as CD155 and CD112 recognized by TIGIT and CD96 receptors (30). Indeed, it has been proved that NK cells exert lytic activity toward Medulloblastoma (MB) and GBM cell lines, both in in vitro (31)(32)(33) and in vivo models (31,34,35). Nevertheless, NK cell activity needs to be optimized in order to overcome inhibition exerted by tumor intrinsic and TME-associated factors.…”

Genome engineering of induced pluripotent stem cells to manufacture natural killer cell therapies

“…Even if NK cells penetrate the tumor, they encounter an array of immune suppressive factors, such as tumor secreted transforming growth factor-beta (TGF-β), that may downregulate NK activity regardless of genetic modifications [147][148][149]. It has been suggested that a dominant negative TGF-β receptor that inhibits TGF-β signaling or a chimeric receptor that converts TGF-β to an activation signal may provide potential strategies to overcome NK cell exhaustion [150,151].…”