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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 protects ovarian cancer cells from lysis by NK cells. NK cells from four healthy donors were isolated and 51Cr release lysis assays at 10:1, 5:1, and 1:1 effector:target ratios were conducted using csMUC16neg-OVC and csMUC16pos-OVC cells. Chromium release from the targets was determined after 4 h incubation under standard tissue culture conditions. Percent lysis was calculated by determining the spontaneous and maximum release of radioactivity from each cell line.
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Figure 4: csMUC16 protects ovarian cancer cells from lysis by NK cells. NK cells from four healthy donors were isolated and 51Cr release lysis assays at 10:1, 5:1, and 1:1 effector:target ratios were conducted using csMUC16neg-OVC and csMUC16pos-OVC cells. Chromium release from the targets was determined after 4 h incubation under standard tissue culture conditions. Percent lysis was calculated by determining the spontaneous and maximum release of radioactivity from each cell line.

Mentions: HLA class I antigens serve as strong inhibitory ligands of the Killer Immunoglobulin-like Receptors (KIR) of NK cells. Therefore, HLA class I expression protects tumor cells from NK cell attack. However, although comparable levels of HLA class I were expressed on the csMUC16pos-OVC and csMUC16neg-OVC the sublines exhibited differential susceptibility to NK cell mediated lysis. Higher protection of the csMUC16pos-OVC from NK cell mediated cytolysis as compared to the csMUC16neg-OVC was consistently observed (Figure 4). NK cells used in these assays were obtained from the peripheral blood of four healthy donors. Cytotoxicity assays at 10:1, 5:1 and 1:1 effector cell:target cell ratios showed that the csMUC16neg-OVC were lysed at a significantly higher level than the csMUC16pos-OVC (Figure 4).


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 protects ovarian cancer cells from lysis by NK cells. NK cells from four healthy donors were isolated and 51Cr release lysis assays at 10:1, 5:1, and 1:1 effector:target ratios were conducted using csMUC16neg-OVC and csMUC16pos-OVC cells. Chromium release from the targets was determined after 4 h incubation under standard tissue culture conditions. Percent lysis was calculated by determining the spontaneous and maximum release of radioactivity from each cell line.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: csMUC16 protects ovarian cancer cells from lysis by NK cells. NK cells from four healthy donors were isolated and 51Cr release lysis assays at 10:1, 5:1, and 1:1 effector:target ratios were conducted using csMUC16neg-OVC and csMUC16pos-OVC cells. Chromium release from the targets was determined after 4 h incubation under standard tissue culture conditions. Percent lysis was calculated by determining the spontaneous and maximum release of radioactivity from each cell line.
Mentions: HLA class I antigens serve as strong inhibitory ligands of the Killer Immunoglobulin-like Receptors (KIR) of NK cells. Therefore, HLA class I expression protects tumor cells from NK cell attack. However, although comparable levels of HLA class I were expressed on the csMUC16pos-OVC and csMUC16neg-OVC the sublines exhibited differential susceptibility to NK cell mediated lysis. Higher protection of the csMUC16pos-OVC from NK cell mediated cytolysis as compared to the csMUC16neg-OVC was consistently observed (Figure 4). NK cells used in these assays were obtained from the peripheral blood of four healthy donors. Cytotoxicity assays at 10:1, 5:1 and 1:1 effector cell:target cell ratios showed that the csMUC16neg-OVC were lysed at a significantly higher level than the csMUC16pos-OVC (Figure 4).

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