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MUC16 provides immune protection by inhibiting synapse formation between NK and ovarian tumor cells.

Gubbels JA, Felder M, Horibata S, Belisle JA, Kapur A, Holden H, Petrie S, Migneault M, Rancourt C, Connor JP, Patankar MS - Mol. Cancer (2010)

Bottom Line: Our results indicate that MUC16-mediated inhibition of immune synapse formation is an effective mechanism employed by ovarian tumors to evade immune recognition.The NK cell leukemia cell line (NKL), which does not express KIRs but are positive for DNAM-1 and NKG2D, also conjugated and lysed MUC16-knockdown cells more efficiently than MUC16 expressing controls.The higher csMUC16 levels on the NKL resistant tumor cells correlated with more protection from lysis as compared to target cells that were never exposed to the effectors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, USA.

ABSTRACT

Background: Cancer cells utilize a variety of mechanisms to evade immune detection and attack. Effective immune detection largely relies on the formation of an immune synapse which requires close contact between immune cells and their targets. Here, we show that MUC16, a heavily glycosylated 3-5 million Da mucin expressed on the surface of ovarian tumor cells, inhibits the formation of immune synapses between NK cells and ovarian tumor targets. Our results indicate that MUC16-mediated inhibition of immune synapse formation is an effective mechanism employed by ovarian tumors to evade immune recognition.

Results: Expression of low levels of MUC16 strongly correlated with an increased number of conjugates and activating immune synapses between ovarian tumor cells and primary naïve NK cells. MUC16-knockdown ovarian tumor cells were more susceptible to lysis by primary NK cells than MUC16 expressing controls. This increased lysis was not due to differences in the expression levels of the ligands for the activating receptors DNAM-1 and NKG2D. The NK cell leukemia cell line (NKL), which does not express KIRs but are positive for DNAM-1 and NKG2D, also conjugated and lysed MUC16-knockdown cells more efficiently than MUC16 expressing controls. Tumor cells that survived the NKL challenge expressed higher levels of MUC16 indicating selective lysis of MUC16(low) targets. The higher csMUC16 levels on the NKL resistant tumor cells correlated with more protection from lysis as compared to target cells that were never exposed to the effectors.

Conclusion: MUC16, a carrier of the tumor marker CA125, has previously been shown to facilitate ovarian tumor metastasis and inhibits NK cell mediated lysis of tumor targets. Our data now demonstrates that MUC16 expressing ovarian cancer cells are protected from recognition by NK cells. The immune protection provided by MUC16 may lead to selective survival of ovarian cancer cells that are more efficient in metastasizing within the peritoneal cavity and also at overcoming anti-tumor innate immune responses.

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csMUC16 inhibits NK activating synapse formation. A. NK cells from healthy donors were mixed with csMUC16neg-OVC and csMUC16pos-OVC cells and confocal microscopy was conducted using 10× magnification. White arrows indicate NK cells bound to tumor cells and some forming activating immune synapses. B. Immune synapses between the NK cells and csMUC16neg-OVC at 40× magnification are shown. NK cells are present in the vicinity of csMUC16pos-OVC cells but form significantly less conjugates and immune synapses. C. Immune synapses between NK cells from three healthy donors and the csMUC16neg-OVC or the csMUC16pos-OVC cells were quantified by counting conjugates that showed polarization of LFA-1 and CD2 divided by the total number of conjugates (defined as two cells in contact).
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Figure 7: csMUC16 inhibits NK activating synapse formation. A. NK cells from healthy donors were mixed with csMUC16neg-OVC and csMUC16pos-OVC cells and confocal microscopy was conducted using 10× magnification. White arrows indicate NK cells bound to tumor cells and some forming activating immune synapses. B. Immune synapses between the NK cells and csMUC16neg-OVC at 40× magnification are shown. NK cells are present in the vicinity of csMUC16pos-OVC cells but form significantly less conjugates and immune synapses. C. Immune synapses between NK cells from three healthy donors and the csMUC16neg-OVC or the csMUC16pos-OVC cells were quantified by counting conjugates that showed polarization of LFA-1 and CD2 divided by the total number of conjugates (defined as two cells in contact).

Mentions: Conjugation between NK cells and targets results in formation of immune synapses. NK cells form activating immune synapses in order to lyse target cells. We therefore determined if the increased conjugation between csMUC16neg-OVC and NK cells resulted in the formation of activating immune synapses. Activating immune synapses between NK cells and csMUC16pos-OVC and csMUC16neg-OVC were quantified by determining the polarization of LFA-1 or CD2 and F-actin at the interface between the effector and target cells. csMUC16neg-OVC cells formed twice as many activating immune synapses with NK cells compared to csMUC16pos-OVC (Figure 7). In some cases, multiple NK cells were also found to form simultaneous activating immune synapses with the csMUC16neg-OVC cells (Figure 7B). Although NK cells were found in the vicinity of csMUC16pos-OVC, activating immune synapses were not formed (Figure 7B).


MUC16 provides immune protection by inhibiting synapse formation between NK and ovarian tumor cells.

Gubbels JA, Felder M, Horibata S, Belisle JA, Kapur A, Holden H, Petrie S, Migneault M, Rancourt C, Connor JP, Patankar MS - Mol. Cancer (2010)

csMUC16 inhibits NK activating synapse formation. A. NK cells from healthy donors were mixed with csMUC16neg-OVC and csMUC16pos-OVC cells and confocal microscopy was conducted using 10× magnification. White arrows indicate NK cells bound to tumor cells and some forming activating immune synapses. B. Immune synapses between the NK cells and csMUC16neg-OVC at 40× magnification are shown. NK cells are present in the vicinity of csMUC16pos-OVC cells but form significantly less conjugates and immune synapses. C. Immune synapses between NK cells from three healthy donors and the csMUC16neg-OVC or the csMUC16pos-OVC cells were quantified by counting conjugates that showed polarization of LFA-1 and CD2 divided by the total number of conjugates (defined as two cells in contact).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2818693&req=5

Figure 7: csMUC16 inhibits NK activating synapse formation. A. NK cells from healthy donors were mixed with csMUC16neg-OVC and csMUC16pos-OVC cells and confocal microscopy was conducted using 10× magnification. White arrows indicate NK cells bound to tumor cells and some forming activating immune synapses. B. Immune synapses between the NK cells and csMUC16neg-OVC at 40× magnification are shown. NK cells are present in the vicinity of csMUC16pos-OVC cells but form significantly less conjugates and immune synapses. C. Immune synapses between NK cells from three healthy donors and the csMUC16neg-OVC or the csMUC16pos-OVC cells were quantified by counting conjugates that showed polarization of LFA-1 and CD2 divided by the total number of conjugates (defined as two cells in contact).
Mentions: Conjugation between NK cells and targets results in formation of immune synapses. NK cells form activating immune synapses in order to lyse target cells. We therefore determined if the increased conjugation between csMUC16neg-OVC and NK cells resulted in the formation of activating immune synapses. Activating immune synapses between NK cells and csMUC16pos-OVC and csMUC16neg-OVC were quantified by determining the polarization of LFA-1 or CD2 and F-actin at the interface between the effector and target cells. csMUC16neg-OVC cells formed twice as many activating immune synapses with NK cells compared to csMUC16pos-OVC (Figure 7). In some cases, multiple NK cells were also found to form simultaneous activating immune synapses with the csMUC16neg-OVC cells (Figure 7B). Although NK cells were found in the vicinity of csMUC16pos-OVC, activating immune synapses were not formed (Figure 7B).

Bottom Line: Our results indicate that MUC16-mediated inhibition of immune synapse formation is an effective mechanism employed by ovarian tumors to evade immune recognition.The NK cell leukemia cell line (NKL), which does not express KIRs but are positive for DNAM-1 and NKG2D, also conjugated and lysed MUC16-knockdown cells more efficiently than MUC16 expressing controls.The higher csMUC16 levels on the NKL resistant tumor cells correlated with more protection from lysis as compared to target cells that were never exposed to the effectors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, WI, USA.

ABSTRACT

Background: Cancer cells utilize a variety of mechanisms to evade immune detection and attack. Effective immune detection largely relies on the formation of an immune synapse which requires close contact between immune cells and their targets. Here, we show that MUC16, a heavily glycosylated 3-5 million Da mucin expressed on the surface of ovarian tumor cells, inhibits the formation of immune synapses between NK cells and ovarian tumor targets. Our results indicate that MUC16-mediated inhibition of immune synapse formation is an effective mechanism employed by ovarian tumors to evade immune recognition.

Results: Expression of low levels of MUC16 strongly correlated with an increased number of conjugates and activating immune synapses between ovarian tumor cells and primary naïve NK cells. MUC16-knockdown ovarian tumor cells were more susceptible to lysis by primary NK cells than MUC16 expressing controls. This increased lysis was not due to differences in the expression levels of the ligands for the activating receptors DNAM-1 and NKG2D. The NK cell leukemia cell line (NKL), which does not express KIRs but are positive for DNAM-1 and NKG2D, also conjugated and lysed MUC16-knockdown cells more efficiently than MUC16 expressing controls. Tumor cells that survived the NKL challenge expressed higher levels of MUC16 indicating selective lysis of MUC16(low) targets. The higher csMUC16 levels on the NKL resistant tumor cells correlated with more protection from lysis as compared to target cells that were never exposed to the effectors.

Conclusion: MUC16, a carrier of the tumor marker CA125, has previously been shown to facilitate ovarian tumor metastasis and inhibits NK cell mediated lysis of tumor targets. Our data now demonstrates that MUC16 expressing ovarian cancer cells are protected from recognition by NK cells. The immune protection provided by MUC16 may lead to selective survival of ovarian cancer cells that are more efficient in metastasizing within the peritoneal cavity and also at overcoming anti-tumor innate immune responses.

Show MeSH
Related in: MedlinePlus