CD200 Expression on Tumor Cells Suppresses Antitumor Immunity: New Approaches to Cancer Immunotherapy

Anke Kretz-Rommel,Naveen Dakappagari,John Mcwhirter,Martha A Wild,Daniela Oltean,Shana Frederickson,Fenghua Qin,Jeremy Springhorn,E Prenn Ravey,Katherine S Bowdish,Toshiaki Maruyama,Dayang Wu,Mary-Jean Nolan

doi:10.4049/jimmunol.178.9.5595

Anke Kretz-Rommel, Naveen Dakappagari + Show 11 more

Open Access

https://doi.org/10.4049/jimmunol.178.9.5595

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Abstract

Although the immune system is capable of mounting a response against many cancers, that response is insufficient for tumor eradication in most patients due to factors in the tumor microenvironment that defeat tumor immunity. We previously identified the immune-suppressive molecule CD200 as up-regulated on primary B cell chronic lymphocytic leukemia (B-CLL) cells and demonstrated negative immune regulation by B-CLL and other tumor cells overexpressing CD200 in vitro. In this study we developed a novel animal model that incorporates human immune cells and human tumor cells to address the effects of CD200 overexpression on tumor cells in vivo and to assess the effect of targeting Abs in the presence of human immune cells. Although human mononuclear cells prevented tumor growth when tumor cells did not express CD200, tumor-expressed CD200 inhibited the ability of lymphocytes to eradicate tumor cells. Anti-CD200 Ab administration to mice bearing CD200-expressing tumors resulted in nearly complete tumor growth inhibition even in the context of established receptor-ligand interactions. Evaluation of an anti-CD200 Ab with abrogated effector function provided evidence that blocking of the receptor-ligand interaction was sufficient for control of CD200-mediated immune modulation and tumor growth inhibition in this model. Our data indicate that CD200 expression by tumor cells suppresses antitumor responses and suggest that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing cancers.

Highlights

To evaluate in vivo whether CD200 expression on human tumor cells such as B cell chronic lymphocytic leukemia (B-CLL) cells suppresses the human immune system, we established a model demonstrating that hPBMCs can reject tumor cells lacking CD200 expression
A number of different negative immune regulators expressed on the surface of tumor cells have been identified, such as B7-H1 [23, 24] and B7-H4 [25,26,27]
Because CD200R is expressed on macrophages and dendritic cells as well as on certain T cells such as follicular Th cells [17], tumor-expressed CD200 can negatively influence the immune system through multiple pathways

Summary

Materials and Methods

Four- to six-week-old NOD.CB17-Prkdcscid/J (NOD/SCID) mice were obtained from The Jackson Laboratory. Other primers were used with the chimeric Fab C2aB7 as the template to generate the murine H chain variable region These fragments were used in overlap PCR, the resulting fragment was digested with XhoI and AgeI, and a 458-bp fragment was used to replace the corresponding XhoI/AgeI fragment in clone 21 to generate chB7-G2G4. After 30 min of incubation on ice, cells were washed and placed at room temperature and the presence of an anti-CD200 Ab on the cell surface was determined at various time points using a FACSCalibur flow cytometer. In some studies one-tenth of the dose of Ab indicated was mixed with 4 ϫ 106 tumor cells and 5–10 ϫ 106 hPBMCs in a total volume of 200 ␮l and administered s.c. Animals subsequently received six doses of Ab as indicated, administered i.v. two times a week for 3 wk.

Results

Discussion

Disclosures