(Cd11b/CD18) Enhances Tumor Response to Radiation by Reducing Myeloid Cell Recruitment
Total Page:16
File Type:pdf, Size:1020Kb
Inhibition of Mac-1 (CD11b/CD18) enhances tumor response to radiation by reducing myeloid cell recruitment G-One Ahna, Diane Tsenga,b, Cho-Hwa Liaoa, Mary Jo Doriea, Agnieszka Czechowiczb, and J. Martin Browna,1 aDivision of Radiation and Cancer Biology, Department of Radiation Oncology, and bInstitute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305 Edited by Napoleone Ferrara, Genentech, Inc., South San Francisco, CA, and approved March 26, 2010 (received for review October 2, 2009) Despite recent advances in radiotherapy, loco-regional failures are tions of myeloid cells, including adhesion, migration, chemotaxis, still the leading cause of death in many cancer patients. We have phagocytosis, and respiratory burst activity (7). Studies have previously reported that bone marrow-derived CD11b+ myeloid cells reported that antibodies to CD11b or CD18 inhibit these functions are recruited to tumors grown in irradiated tissues, thereby restoring (8) and in vivo administration of the antibodies reduce leukocyte the vasculature and tumor growth. In this study, we examined recruitment into various sites of inflammation (9). Given the whether neutralizing CD11b monoclonal antibodies could inhibit promising preclinical activities of CD11b/CD18 antibodies in the recruitment of myeloid cells into irradiated tumors and inhibit inhibiting myeloid cell adhesion onto endothelium, humanized their regrowth. We observed a significant enhancement of antitu- antibodies [LeukArrest; 23F2G (10)] have been developed and mor response to radiation in squamous cell carcinoma xenografts tested in patients with stroke, multiple sclerosis, or myocardial in mice when CD11b antibodies are administered systemically. His- infarction (11). However, although the antibodies showed excellent tological examination of tumors revealed that CD11b antibodies re- safety profiles, they lacked therapeutic efficacy (10, 11). duced infiltration of myeloid cells expressing S100A8 and matrix In this study, we used CD11b-neutralizing monoclonal anti- metalloproteinase-9. CD11b antibodies further inhibited bone bodies as a means to inhibit the recruitment of myeloid cells to marrow-derived cell adhesion and transmigration to C166 endothe- irradiated tumors. With systemic administration of these CD11b lial cell monolayers and chemotactic stimuli, respectively, to levels antibodies following local tumor irradiation, we observed a signif- comparable to those from CD11b knockout or CD18 hypomorphic icant enhancement of tumor response to radiation accompanied mice. Given the clinical availability of humanized CD18 antibodies, by a reduced infiltration of myeloid cells expressing MMP-9 and we tested two murine tumor models in CD18 hypomorphic or CD11b S100A8 into the tumors. We also observed that CD18 hypo- knockout mice and found that tumors were more sensitive to irradi- morphism, which had lowered CD11b surface expression myeloid ation when grown in CD18 hypomorphic mice but not in CD11b cells, significantly associated with the sensitivity of tumors to ra- knockout mice. When CD18 hypomorphism was partially rescued diation. Together, these results suggest that clinically available by reconstitution with the wild-type bone marrow, the resistance humanized antibodies against CD11b/CD18 could be useful as an of the tumors to irradiation was restored. Our study thus supports adjuvant therapy to radiotherapy. MEDICAL SCIENCES the rationale of using clinically available Mac-1 (CD11b/CD18) anti- bodies as an adjuvant therapy to radiotherapy. Results Radiation Inhibits Local Angiogenesis but the Vasculature Is Restored S100A8 | vasculogenesis | radiosensitivity in Recurrent Tumors Accompanied by Infiltrating Myeloid Cells. To determine the effects of local irradiation on angiogenesis, we adiotherapy plays a crucial role in cancer treatment, espe- first examined the histology of FaDu human head and neck Rcially for inoperable tumors. Recent advances, including squamous cell carcinoma xenografts grown in immune-deficient image-guided and intensity-modulated radiotherapy, leading to mice that were either unirradiated (control, 0 Gy), harvested higher and more precise dose delivery, has achieved superior shortly after 20 Gy of irradiation (IR 20 Gy), or had recurred treatment outcomes (1). However, despite these advances, re- after irradiation with 20 Gy, which took ≈2 months following currence of the primary tumors still remains the leading cause of irradiation [recurrent (2 mo)] (Fig. 1A). Tumor volumes were death of patients treated with radiotherapy (2). This finding ≈25 and 50% of the unirradiated control for irradiated tumors highlights the fact that we need an improved understanding of and recurrent tumors, respectively (Fig. 1A). By staining for the reasons for treatment failure. endothelial cells and pericytes with CD31 and α-smooth muscle We have previously shown that irradiated tumors, or tumors actin (α-SMA) antibodies, respectively, we found that the irra- grown in previously irradiated tissues (thereby mimicking re- diated tumors had significantly fewer endothelial cells and per- current primary tumors), recruit large numbers of bone marrow- icytes compared with the control tumors (Fig. 1 A and B). + derived CD11b myeloid cells expressing matrix metal- However, when the tumors had recurred after irradiation, the loproteinase-9 (MMP-9) (3). We further demonstrated that these number of endothelial cells had returned to control levels, al- MMP-9-expressing myeloid cells restored tumor vasculature and though the pericyte coverage was partially restored (Fig. 1 A and allowed tumor growth in the irradiated tissues of MMP-9 knockout B). To determine the myeloid cell contribution to the changes in (KO) mice, suggesting that these cells could be an important target in radiotherapy (3). There is strong evidence to suggest that tumor- fi + in ltrating CD11b myeloid cells promote angiogenesis, and do Author contributions: G-O.A., D.T., C.-H.L., M.J.D., A.C., and J.M.B. designed research; G-O.A., so by expressing various proangiogenic and chemoattractant D.T., C.-H.L., M.J.D., and A.C. performed research; G-O.A., D.T., C.-H.L., M.J.D., and A.C. ana- molecules, including VEGF (4), Bv8 (5), and S100A8 (6). How- lyzed data; and G-O.A. and J.M.B. wrote the paper. + ever, despite their tumor-promoting roles, targeting CD11b The authors declare no conflict of interest. myeloid cells as a cancer therapy has proven difficult. This article is a PNAS Direct Submission. CD11b (Mac-1, αMβ2) is the α-subunit of the predominant β2 1To whom correspondence should be addressed. E-mail: [email protected]. (CD18) integrin expressed on monocytes/macrophages and gran- This article contains supporting information online at www.pnas.org/cgi/content/full/ ulocytes (7). This subunit has been shown to mediate many func- 0911378107/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.0911378107 PNAS | May 4, 2010 | vol. 107 | no. 18 | 8363–8368 Downloaded by guest on September 25, 2021 + Control (0 Gy) IR 20 Gy (d14) Recurrent (2 mo) filtration of CD11b myeloid cells, we determined whether anti- ADAPIDAPI Tumor volume bodies to CD11b could reduce the myeloid cell recruitment and *** ) 3 -SMA 250 *** *** m m sensitize the tumors to irradiation. We harvested CD11b mono- ( 200 α e clonal antibodies (IgG2b isotype) from M1/70 hybridoma and first C D 3 1 m 150 ul o 100 determined the dose and timing of the antibodies for in vivo ad- T u m o r v 50 DAPI DAPI ministration. We similarly studied Gr-1 antibodies (IgG2b isotype) 0 lort u r r e n t R 2 0 G y harvested from RB6-8C5 hybridoma. We first observed that Gr-1 o n C D 1 1 b fi + + c C I antibodies ef ciently depleted granulocytes (CD11b Gr-1 cells) R e at 24 h after a single i.p. administration; CD11b antibodies did not affect the leukocyte composition (Fig. S1A and Table S1). CD11b B CD31 α-SMA CD11b CD45 antibodies exhibited a complete epitope blockage with 100 μgat 6 20 4 10 n s i t y ( % ) ** ** *** *** *** *** *** ** 24 h (Fig. S1 C and D), which was partially reversed at 72 h after 4 * administration (Fig. S1E). Therefore, to maintain constant epitope e 10 2 5 e a d 2 blocking of myeloid cells, we treated the mice with CD11b anti- r A bodies at 100 μg per mouse every 2 days. Gr-1 antibodies were 0 0 0 0 C o n t r o l C o n t r o l l lo e n t R e c u r r e n t R e c u r r e n t R e c u r r e n t y y I R 2 0 G y I R 2 0 G y o R 2 0 G G C o n t r rt r administered to a separate group of animals in a similar manner. I R 2 0 o n r uc C I e To monitor epitope blockage by CD11b antibodies or granulo- R cyte depletion by Gr-1 antibodies, we sampled peripheral blood C Control (0 Gy) IR 20 Gy (d14) D CD31 α-SMA from the treated animals once every four days for FACS analysis (%) 4 2 10 *** H D -SMA (Figs. S1 and S2 ). t 3 3 3 4 y A r e a d e n s i t fi α When FaDu tumor-bearing immunode cient mice were treated s 5 c h C D 3 1 2 e with CD11b antibodies following either 12 or 20 Gy of a single dose H o 0 0 fi lo lort of irradiation given locally to the tumors, we observed a signi cant I I R 2 0 G y I R 2 0 G y r C o n t A o n enhancement of tumor response to radiation (Fig. 2 ). Macro- C scopically, the CD11b antibody-treated tumors shrank dramati- Fig. 1. Local irradiation inhibits angiogenesis. (A) Staining of FaDu tumors cally, leading to nearly nonpalpable tumors by the end of the study grown in immunodeficient mice that were not irradiated (control, 0 Gy), (Fig.