Demonstration of inflammation-induced cancer and cancer immunoediting during primary tumorigenesis

Abstract

Here we report the effects of loss of the Toll-like receptor-associated signaling adaptor myeloid-differentiation factor 88 (MyD88) on tumor induction in two distinct mouse models of carcinogenesis. The 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol 13-acetate (TPA)-induced skin papilloma model depends on proinflammatory processes, whereas the 3'-methylcholanthrene (MCA) induction of fibrosarcoma has been used by tumor immunologists to illustrate innate and adaptive immune surveillance of cancer. When exposed to a combination of DMBA/TPA, mice lacking MyD88 formed fewer skin papillomas than genetically matched WT controls treated in a similar manner. Unexpectedly, however, fewer MyD88-/- mice formed sarcomas than WT controls when exposed to MCA. In contrast, MyD88-deficient mice did not show a defective ability to reject highly immunogenic transplanted tumors, including MCA sarcomas. Despite the reported role of TNF in chronic inflammation, TNF-deficient mice were significantly more susceptible to MCA-induced sarcoma than WT mice. Overall, these data not only confirm the key role that MyD88 plays in promoting tumor development but also demonstrate that inflammation-induced carcinogenesis and cancer immunoediting can indeed occur in the same mouse tumor model.

Fig. 1.

MyD88 promotes the formation of DMBA/TPA-induced skin papillomas. WT and MyD88^−/− mice were injected with 25 μg of DMBA and 1 week later twice weekly with 4 μg of TPA for 20 weeks as described in Materials and Methods. Mice were subsequently monitored for skin papilloma development for 25 weeks (n = 11–15 mice per group). (A) Proportion of mice in the group with papillomas over time. (B) Mean lesion number per mouse over time. Significant differences in mean lesion number per mouse were observed by the unpaired Mann–Whitney U test (*, P < 0.05). Significant differences in proportion with papilloma at any one time point were determined by Fisher's exact test (*, P < 0.05). Differences were observed at all points between the asterisks (weeks 17–25).

Fig. 2.

MyD88 promotes the formation of MCA-induced fibrosarcomas. WT and MyD88^−/− mice were injected with 400 μg (A), 100 μg (B), 25 μg (C), or 5 μg (D) of MCA as described in Materials and Methods and subsequently monitored for tumor development over 200 days (n = 12–15 mice per group). Results are shown as the percentage of mice with sarcoma at each time point after MCA inoculation. Significant differences in tumor incidence were determined by Fisher's exact test (*, P < 0.05).

Fig. 3.

TNFα functions to protect the host against MCA sarcoma induction. WT and various gene-targeted mice as indicated were injected with either 100 μg (filled bars) or 25 μg (open bars) of MCA as described in Materials and Methods and subsequently monitored for tumor development over 200 days (number of mice in each group shown in parentheses). Some WT mice were depleted of NK1.1⁺ cells weekly from the time of MCA inoculation to day 56. Results are shown as the percentage of mice with sarcoma in each group after MCA inoculation. Results are a collective of 3–12 experiments for each genotype/treatment performed over a 9-year period (all shown in SI Fig. 7), compared with WT controls within each experiment.

Fig. 4.

MyD88 is not required for T cell-mediated rejection of a transplanted immunogenic tumor. Groups of 10 WT and MyD88^−/− mice were challenged s.c. with either 3 × 10⁶ (A and B) or 1 × 10⁶ (C and D) EG7 tumor cells as indicated and subsequently monitored for tumor growth. Solid lines indicate tumor growth of individual mice; the dotted lines indicate the mean tumor size of the group.

Fig. 5.

MyD88 is not required for the rejection of transplanted immunogenic tumors or the growth of transplanted nonimmunogenic tumors. (A–C) WT, MyD88^−/−, and Rag2^−/− mice were challenged with 1 × 10⁶ cells from MCA-induced immunogenic fibrosarcoma cell lines 7835 (A), 1972 (B), and 1973 (C). (D) The nonimmunogenic WT progressor tumor, 9614, was injected into MyD88 and WT mice at the indicated doses. Tumor cells were injected s.c. in the right flank of each mouse.

Fig. 6.

MyD88 does not control MCA-induced sarcomas that emerge from MyD88-deficient mice. Groups of five WT (filled symbols) and MyD88^−/− (open symbols) mice were challenged s.c. with increasing tumor cell numbers (circles, 10⁴; triangles, 10⁵; squares, 10⁶) of M88–1 sarcoma (A) or M88–2 sarcoma (B), both derived from MyD88^−/− mice. Mice were subsequently monitored for tumor growth, and data are presented as the mean tumor area ± SEM (n = 5 mice per group).