Induction of anti-leukemic responses by stimulation of leukemic CD3+ cells with allogeneic stimulator cells

Murine Leukemia-Derived Extracellular Vesicles Elicit Antitumor Immune Response

Background

Extracellular vesicles (EVs) are heterogeneous lipid bilayer particles secreted by cells. EVs contain proteins, RNA, DNA and other cargo that can have immunomodulatory effects. Cancer-derived EVs have been described as having immunomodulating effects in vivo with immunosuppressive and pro-tumor growth capabilities. However, cancer-derived EVs have also been harnessed and utilized for anti-cancer potential.

Methods

To assess the immunomodulatory effect of EVs produced by acute myeloid leukemia (AML) cells, we isolated vesicles secreted by the murine AML cell line, C1498, and investigated their effect on in vitro and in vivo immune responses.

Results

These leukemia-derived EVs were found to induce increased proliferation of CD3+ cells and enhanced cytolytic activity of CD3+ cells directed toward leukemic cells in vitro. Injection of leukemia-derived EVs into syngeneic naïve mice induced T cell responses in vivo and resulted in enhanced immune responses upon T cell re-stimulation in vitro.

Conclusion

These findings indicate that C1498-derived EVs have immunomodulatory effects on cell-mediated immune responses that could potentially be utilized to facilitate anti-leukemia immune responses.

Current state of nonengrafting donor leukocyte infusion (focus on microtransplantation for acute myeloid leukemia)

PURPOSE OF REVIEW

Microtransplantation (or micro-stem cell transplantation, MST) is one permutation of alloreactive immunotherapy increasingly studied in clinical trials. It is most commonly applied to patients with myeloid malignancies who are not suitable candidates for allogeneic hematopoietic cell transplantation. This review highlights the past 2 years of work on stem/progenitor cell products in the field of nonengrafting donor leukocyte infusion (NE-DLI), with a focus on applications of MST in acute myeloid leukemia (AML).

RECENT FINDINGS

Assessing the utility of MST is hampered by lack of randomized controlled trials and by variability in donor selection algorithms, treatment timing, and unknown factors. The inherent complexity of the bidirectional alloreactive reactions, implicating many cell types, makes it challenging to move beyond correlative, population-level biology toward mechanistic explanations for MST's actions in any given patient-donor pair. Yet there are indicators that by stimulating a recipient-vs.-tumor effect, MST might substantially improve complete remission rates in AML and that it might find a role in postremission therapy.

SUMMARY

The mechanistic underpinnings of MST are gradually being disentangled and its clinical development remains in early stages.