Immune response to RB1-regulated senescence limits radiation-induced osteosarcoma formation
Maya Kansara, … , Mark J. Smyth, David M. Thomas
Maya Kansara, … , Mark J. Smyth, David M. Thomas
Published November 15, 2013
Citation Information: J Clin Invest. 2013;123(12):5351-5360. https://doi.org/10.1172/JCI70559.
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Research Article Oncology

Immune response to RB1-regulated senescence limits radiation-induced osteosarcoma formation

Abstract

Ionizing radiation (IR) and germline mutations in the retinoblastoma tumor suppressor gene (RB1) are the strongest risk factors for developing osteosarcoma. Recapitulating the human predisposition, we found that Rb1+/– mice exhibited accelerated development of IR-induced osteosarcoma, with a latency of 39 weeks. Initial exposure of osteoblasts to carcinogenic doses of IR in vitro and in vivo induced RB1-dependent senescence and the expression of a panel of proteins known as senescence-associated secretory phenotype (SASP), dominated by IL-6. RB1 expression closely correlated with that of the SASP cassette in human osteosarcomas, and low expression of both RB1 and the SASP genes was associated with poor prognosis. In vivo, IL-6 was required for IR-induced senescence, which elicited NKT cell infiltration and a host inflammatory response. Mice lacking IL-6 or NKT cells had accelerated development of IR-induced osteosarcomas. These data elucidate an important link between senescence, which is a cell-autonomous tumor suppressor response, and the activation of host-dependent cancer immunosurveillance. Our findings indicate that overcoming the immune response to senescence is a rate-limiting step in the formation of IR-induced osteosarcoma.

Authors

Maya Kansara, Huei San Leong, Dan Mei Lin, Sophie Popkiss, Puiyi Pang, Dale W. Garsed, Carl R. Walkley, Carleen Cullinane, Jason Ellul, Nicole M. Haynes, Rod Hicks, Marieke L. Kuijjer, Anne-Marie Cleton-Jansen, Philip W. Hinds, Mark J. Smyth, David M. Thomas

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Figure 5

Cd1d1–/– mice are predisposed to the development of 45Ca-induced osteosarcomas compared to control mice.

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Cd1d1–/– mice are predisposed to the development of 45Ca-induced osteos...
(A) Rag1–/– mouse background is permissive for growth of Il6–/– osteosarcoma cells. The Il6–/–#12 cell line was implanted subcutaneously into the flanks of Il6–/–, Rag1–/–, and WT mice (6 per cohort), and tumor volume was measured for 30 days. (B and C) NKT cell infiltration is decreased in (B) Rb1fl/fl spines following exposure to 45Ca (mean ± SEM; n = 6–7 per cohort; *P = 0.04 compared to wild-type spines) and (C) Il6–/– spines 2 weeks following exposure to IR (n = 6 per cohort; *P = 0.01 compared to WT spines). (D) NKT cell infiltration into Il6–/– cell lines transplanted into WT mice correlates with growth suppression (n = 4 per cohort; *P = 0.04 compared to WT/WT). (B–D) *P < 0.05, 2-tailed Student’s t test. (E) Initial growth of Il6–/– cell line in Cd1d1–/– mice. Large graphs show immediate effect, whereas inset graphs show long-term growth. The Il6–/– #18 cell line was implanted subcutaneously into Il6–/–, Cd1d1–/–, Jα18–/–, and WT mice, and tumor volume was measured. (F) Cohorts of C57/BL6 wild-type (n = 14) and Cd1d1–/– (n = 20) mice were injected with 4 μCi/g 45Ca. Kaplan-Meier plots of osteosarcoma onset. P = 0.008, log-rank (Mantel-Cox) test. (G) SA-β-Gal staining in Cd1d1–/– and control mice. Mice were injected with 4 μCi 45Ca and sacrificed 2 weeks later. Sections of spine were stained for SA-β-Gal (15 images per cohort). Box-and-whisker plot shows the mean percentage blue pixels in the whole image and SEM (P = 0.4).