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Poly(I:C) enhances the susceptibility of leukemic cells to NK cell cytotoxicity and phagocytosis by DC.

Lion E, Anguille S, Berneman ZN, Smits EL, Van Tendeloo VF - PLoS ONE (2011)

Bottom Line: We previously reported that acute myeloid leukemic (AML) cells in response to electroporation with the synthetic dsRNA analogue poly(I:C) exert improved immunogenicity, demonstrated by enhanced DC-activating and NK cell interferon-γ-inducing capacities.Moreover, the enhanced killing and the improved uptake are strongly correlated.These data strongly support the use of poly(I:C) as a cancer vaccine component, providing a way to overcome immune evasion by leukemic cells.

View Article: PubMed Central - PubMed

Affiliation: Vaccine & Infectious Disease Institute (Vaxinfectio), Laboratory of Experimental Hematology, Faculty of Medicine, University of Antwerp, Antwerp, Belgium. eva.lion@ua.ac.be

ABSTRACT
α active specific immunotherapy aims at stimulating the host's immune system to recognize and eradicate malignant cells. The concomitant activation of dendritic cells (DC) and natural killer (NK) cells is an attractive modality for immune-based therapies. Inducing immunogenic cell death to facilitate tumor cell recognition and phagocytosis by neighbouring immune cells is of utmost importance for guiding the outcome of the immune response. We previously reported that acute myeloid leukemic (AML) cells in response to electroporation with the synthetic dsRNA analogue poly(I:C) exert improved immunogenicity, demonstrated by enhanced DC-activating and NK cell interferon-γ-inducing capacities. To further invigorate the potential of these immunogenic tumor cells, we explored their effect on the phagocytic and cytotoxic capacity of DC and NK cells, respectively. Using single-cell analysis, we assessed these functionalities in two- and three-party cocultures. Following poly(I:C) electroporation AML cells become highly susceptible to NK cell-mediated killing and phagocytosis by DC. Moreover, the enhanced killing and the improved uptake are strongly correlated. Interestingly, tumor cell killing, but not phagocytosis, is further enhanced in three-party cocultures provided that these tumor cells were upfront electroporated with poly(I:C). Altogether, poly(I:C)-electroporated AML cells potently activate DC and NK cell functions and stimulate NK-DC cross-talk in terms of tumor cell killing. These data strongly support the use of poly(I:C) as a cancer vaccine component, providing a way to overcome immune evasion by leukemic cells.

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Correlations of functional properties of NK cells and DC regarding poly(I:C) electroporation of the U-937 cell line.(A) Positive correlation between the effect of poly(I:C) electroporation of U-937 cells on the NK cell killing capacity and the DC phagocytic function, expressed as the difference (delta) in functions between mock- and poly(I:C)-electroporated U-937 cells. (B) The concentrations IFN-α and IFN-γ in supernatant of NK cell:U-937 poly(I:C)-electroporated cocultures are strongly correlated. The improved (C) phagocytosis by immature DC and (D) killing by NK cells are in positive relation with the concentration IFN-α secreted by poly(I:C)-electroporated U-937 cells. Spearman rank correlations were calculated for defined functions. Abbreviations: mock EP, electroporated without poly(I:C); pIC EP, electroporated with poly(I:C); Δ killing  =  % killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells; Δ phagocytosis  =  % phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells.
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pone-0020952-g006: Correlations of functional properties of NK cells and DC regarding poly(I:C) electroporation of the U-937 cell line.(A) Positive correlation between the effect of poly(I:C) electroporation of U-937 cells on the NK cell killing capacity and the DC phagocytic function, expressed as the difference (delta) in functions between mock- and poly(I:C)-electroporated U-937 cells. (B) The concentrations IFN-α and IFN-γ in supernatant of NK cell:U-937 poly(I:C)-electroporated cocultures are strongly correlated. The improved (C) phagocytosis by immature DC and (D) killing by NK cells are in positive relation with the concentration IFN-α secreted by poly(I:C)-electroporated U-937 cells. Spearman rank correlations were calculated for defined functions. Abbreviations: mock EP, electroporated without poly(I:C); pIC EP, electroporated with poly(I:C); Δ killing  =  % killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells; Δ phagocytosis  =  % phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells.

Mentions: Both killing by NK cells and phagocytosis by DC are significantly improved when AML cells are electroporated with poly(I:C). Focusing on the effect of poly(I:C) electroporation, we looked at the difference of killing and phagocytosis between mock- and poly(I:C)-electroporated tumor cells, depicted as Δ killing (% killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells) and Δ phagocytosis (% phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells). Comparing the killing capacity in NK:tumor cell cocultures with the phagocytic capacity in DC:tumor cell cocultures, we observed a significant positive correlation for the U-937 cell line (r = 0.89, p = 0.03; figure 6A), but not for K562 cells (r = −0.67, p = 0.23). Interestingly, we also demonstrate correlations with reference to the effect of poly(I:C) electroporation of the U-937 cell line and the cytokines IFN-α and IFN-γ. A positive correlation was found between the poly(I:C)-induced enhanced killing of U-937 cells by NK cells and the concentration of IFN-α secreted by U-937 cells (r = 0.71, p = 0.14; figure 6D). The IFN-α concentration was also found to be positively correlated with the improved uptake of U-937 cells by DC upon poly(I:C) electroporation (r = 0.89, p = 0.03; figure 6C). With regard to the IFN-γ concentration, detected in cocultures with NK cells and poly(I:C)-electroporated U-937 cells, we demonstrate a positive relationship with the improved killing in NK cell:tumor cell cocultures (r = 0.60, p = 0.24) and with the improved uptake of U-937 cells in NK cell:DC:tumor cell cocultures (r = 0.77, p = 0.10; data not shown). Finally, the concentrations IFN-α and IFN-γ found in cocultures of NK cells and poly(I:C)-electroporated U-937 cells are strongly correlated (r = 0.93, p = 0.007; figure 6B).


Poly(I:C) enhances the susceptibility of leukemic cells to NK cell cytotoxicity and phagocytosis by DC.

Lion E, Anguille S, Berneman ZN, Smits EL, Van Tendeloo VF - PLoS ONE (2011)

Correlations of functional properties of NK cells and DC regarding poly(I:C) electroporation of the U-937 cell line.(A) Positive correlation between the effect of poly(I:C) electroporation of U-937 cells on the NK cell killing capacity and the DC phagocytic function, expressed as the difference (delta) in functions between mock- and poly(I:C)-electroporated U-937 cells. (B) The concentrations IFN-α and IFN-γ in supernatant of NK cell:U-937 poly(I:C)-electroporated cocultures are strongly correlated. The improved (C) phagocytosis by immature DC and (D) killing by NK cells are in positive relation with the concentration IFN-α secreted by poly(I:C)-electroporated U-937 cells. Spearman rank correlations were calculated for defined functions. Abbreviations: mock EP, electroporated without poly(I:C); pIC EP, electroporated with poly(I:C); Δ killing  =  % killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells; Δ phagocytosis  =  % phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3117863&req=5

pone-0020952-g006: Correlations of functional properties of NK cells and DC regarding poly(I:C) electroporation of the U-937 cell line.(A) Positive correlation between the effect of poly(I:C) electroporation of U-937 cells on the NK cell killing capacity and the DC phagocytic function, expressed as the difference (delta) in functions between mock- and poly(I:C)-electroporated U-937 cells. (B) The concentrations IFN-α and IFN-γ in supernatant of NK cell:U-937 poly(I:C)-electroporated cocultures are strongly correlated. The improved (C) phagocytosis by immature DC and (D) killing by NK cells are in positive relation with the concentration IFN-α secreted by poly(I:C)-electroporated U-937 cells. Spearman rank correlations were calculated for defined functions. Abbreviations: mock EP, electroporated without poly(I:C); pIC EP, electroporated with poly(I:C); Δ killing  =  % killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells; Δ phagocytosis  =  % phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells.
Mentions: Both killing by NK cells and phagocytosis by DC are significantly improved when AML cells are electroporated with poly(I:C). Focusing on the effect of poly(I:C) electroporation, we looked at the difference of killing and phagocytosis between mock- and poly(I:C)-electroporated tumor cells, depicted as Δ killing (% killing of poly(I:C)-electroporated tumor cells - % killing of mock-electroporated tumor cells) and Δ phagocytosis (% phagocytosis of poly(I:C)-electroporated tumor cells - % phagocytosis of mock-electroporated tumor cells). Comparing the killing capacity in NK:tumor cell cocultures with the phagocytic capacity in DC:tumor cell cocultures, we observed a significant positive correlation for the U-937 cell line (r = 0.89, p = 0.03; figure 6A), but not for K562 cells (r = −0.67, p = 0.23). Interestingly, we also demonstrate correlations with reference to the effect of poly(I:C) electroporation of the U-937 cell line and the cytokines IFN-α and IFN-γ. A positive correlation was found between the poly(I:C)-induced enhanced killing of U-937 cells by NK cells and the concentration of IFN-α secreted by U-937 cells (r = 0.71, p = 0.14; figure 6D). The IFN-α concentration was also found to be positively correlated with the improved uptake of U-937 cells by DC upon poly(I:C) electroporation (r = 0.89, p = 0.03; figure 6C). With regard to the IFN-γ concentration, detected in cocultures with NK cells and poly(I:C)-electroporated U-937 cells, we demonstrate a positive relationship with the improved killing in NK cell:tumor cell cocultures (r = 0.60, p = 0.24) and with the improved uptake of U-937 cells in NK cell:DC:tumor cell cocultures (r = 0.77, p = 0.10; data not shown). Finally, the concentrations IFN-α and IFN-γ found in cocultures of NK cells and poly(I:C)-electroporated U-937 cells are strongly correlated (r = 0.93, p = 0.007; figure 6B).

Bottom Line: We previously reported that acute myeloid leukemic (AML) cells in response to electroporation with the synthetic dsRNA analogue poly(I:C) exert improved immunogenicity, demonstrated by enhanced DC-activating and NK cell interferon-γ-inducing capacities.Moreover, the enhanced killing and the improved uptake are strongly correlated.These data strongly support the use of poly(I:C) as a cancer vaccine component, providing a way to overcome immune evasion by leukemic cells.

View Article: PubMed Central - PubMed

Affiliation: Vaccine & Infectious Disease Institute (Vaxinfectio), Laboratory of Experimental Hematology, Faculty of Medicine, University of Antwerp, Antwerp, Belgium. eva.lion@ua.ac.be

ABSTRACT
α active specific immunotherapy aims at stimulating the host's immune system to recognize and eradicate malignant cells. The concomitant activation of dendritic cells (DC) and natural killer (NK) cells is an attractive modality for immune-based therapies. Inducing immunogenic cell death to facilitate tumor cell recognition and phagocytosis by neighbouring immune cells is of utmost importance for guiding the outcome of the immune response. We previously reported that acute myeloid leukemic (AML) cells in response to electroporation with the synthetic dsRNA analogue poly(I:C) exert improved immunogenicity, demonstrated by enhanced DC-activating and NK cell interferon-γ-inducing capacities. To further invigorate the potential of these immunogenic tumor cells, we explored their effect on the phagocytic and cytotoxic capacity of DC and NK cells, respectively. Using single-cell analysis, we assessed these functionalities in two- and three-party cocultures. Following poly(I:C) electroporation AML cells become highly susceptible to NK cell-mediated killing and phagocytosis by DC. Moreover, the enhanced killing and the improved uptake are strongly correlated. Interestingly, tumor cell killing, but not phagocytosis, is further enhanced in three-party cocultures provided that these tumor cells were upfront electroporated with poly(I:C). Altogether, poly(I:C)-electroporated AML cells potently activate DC and NK cell functions and stimulate NK-DC cross-talk in terms of tumor cell killing. These data strongly support the use of poly(I:C) as a cancer vaccine component, providing a way to overcome immune evasion by leukemic cells.

Show MeSH
Related in: MedlinePlus