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A Novel Link between Inflammation and Cancer
Cancer Cell
Previews A Novel Link between Inflammation and Cancer Yenkel Grinberg-Bleyer1 and Sankar Ghosh1,* 1Department of Microbiology & Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA *Correspondence: [email protected] http://dx.doi.org/10.1016/j.ccell.2016.11.013
Immune checkpoint-blockade treatments targeting PD-1/PD-L1 have revolutionized cancer therapy. Hence, understanding the regulation of PD-L1 expression has major clinical relevance. In this issue of Cancer Cell, Lim et al. report that inflammation-induced and NF-kB-driven expression of deubiquitinating enzyme CSN5 leads to PD-L1 stabilization and immune suppression in tumors. The role of innate immunity-mediated inflammation in cancer biology is still debated. However, in most instances, inflammatory cytokines such as tumor necrosis factor (TNF) or IL-6 have been shown to enhance tumor survival, proliferation, or angiogenesis (Grivennikov et al., 2010). Moreover, through the expression of certain cytokines, metabolites, and membrane receptors, macrophages and myeloid-derived suppressor cells (MDSCs) can inhibit adaptive anti-tumor responses. Suppression of effector immune responses in the tumor microenvironment is a central mechanism of tumor escape. In the past decade, the concept of immune checkpoint has emerged through the identification of several molecular pathways that skew effector immunity toward tolerance. Among these, inhibition of CD4 and CD8 T cells by the B7/CTLA-4 and PD-L1/ PD-1 pathways has led to novel therapeutic approaches for treatment of cancer— namely, immune checkpoint blockade. Antibodies targeting both pathways have demonstrated promising clinical outcomes in melanoma and lung cancer. Programmed death ligand 1 (PD-L1, also named B7-H1 or CD274) is a transmembrane protein of the B7 family that is expressed by a variety of cancer cells and by tumor-infiltrating immune cells, including dendritic cells and macrophages (Zou et al., 2016). PD-L1 binds to its receptor PD-1 on the surface of T cells and inhibits proliferation, survival, and the secretion of effector cytokines such as interferon-gamma (IFN-g) or interleukin-2 (IL-2). This eventually results in T cell exhaustion. Besides this direct effect on T cells, it has been proposed that PD-L1 signaling in tumor cells may promote their proliferation and survival by maintaining an optimal metabolic profile (Chang et al., 2015).
High expression of surface PD-L1 by solid tumors and tumor-infiltrating myeloid cells appears to be globally associated with poor prognosis, even though observations can be variable (Wu et al., 2015). Also, the correlation between PD-L1 expression status and clinical response to PD-1 blockade is under scrutiny. Thus, understanding how PDL1 expression is regulated has important clinical applications. Expression of the PD-L1 (Cd274) gene can be induced by Toll-like receptor (TLR) or IFN-g-driven nuclear factor-kappa B (NF-kB), signal transducer and activator of transcription 1 and 3 (STAT1/3), and interferon regulatory factor 1 (IRF1) activity, as well as by hypoxia-inducible factor 1 (HIF-1a) (Ritprajak and Azuma, 2015). After transcription, PD-L1 mRNA can be targeted for degradation by the microRNAs 513 and 570. However, how PD-L1 is regulated at the protein level is poorly understood. A recent paper from the Hung lab showed that mature PD-L1 was glycosylated at four independent residues upon epidermal growth factor receptor (EGFR) stimulation of mouse and human breast cancer cells, leading to its stabilization (Li et al., 2016). In the absence of glycosylation, PD-L1 was phosphorylated by glycogen synthase kinase 3-beta (GSK3b), which induced its K48-ubiquitination and subsequent degradation. In the current issue of Cancer Cell, the same group now shows that PD-L1 stability is also maintained by the active deubiquitination of PD-L1 by the fifth element of the COP9 signalosome (CSN5) protein (also named Jab1, and encoded by COPS5) (Lim et al., 2016). The CSN complex has previously been shown to act as a modulator of intracellular signaling though its deneddylation activity. Specifically, the tumor suppressors p27, p53, and Smad4
can be targeted by CSN5, thereby conferring a pro-tumoral function to CSN5. CSN5 was also shown to serve as a deubiquitinase in breast cancer and 293 kidney epithelial cells, through its JAMM domain. Additionally, high expression of CSN5 is often correlated with poor outcome in patients with ovarian cancer, nasopharyngeal carcinoma, or lymphoma (Pan et al., 2016). Lim et al. now make the observation that macrophage-derived TNF enhances immunosuppression and tumor growth by increasing PD-L1 protein expression without changing mRNA levels. Using elegant mass spectrometry experiments, they identified CSN5 as a TNF-induced PD-L1-bound protein. Upon binding to PD-L1 through its C-terminal domain, CSN5 removes K48-linked ubiquitin on PD-L1, hence increasing PD-L1 protein stability. Expression of CSN5 mRNA was induced by TNF simulation and was dependent on the NF-kB subunit RelA/ p65, which directly regulated CSN5 expression by binding to its promoter. This involvement of NF-kB complements previous observations describing a function for STAT-3 in the spontaneous CSN5 overexpression in nasopharyngeal cancer cells (Figure 1). Interestingly, CSN5 knockdown in breast cancer cells led to impaired growth in vivo. In agreement with these findings, the authors also observed that in vivo administration of the NF-kB inhibitor, curcumin, synergized with anti-CTLA-4 checkpoint-blockade therapy to reduce the growth of breast cancer, colon carcinoma, and melanoma cell lines. Curcumin has long been described as an anti-cancer compound affecting NF-kB-mediated survival and proliferation. In this study, its therapeutic effect in this new set of data seems to rely on inhibition of CSN5,
Cancer Cell 30, December 12, 2016 ª 2016 Elsevier Inc. 829
Cancer Cell
Previews
effective. The safety of such approaches is of the highest importance; here the authors show that certain natural molecules known to have low toxicity, such as curcumin, through its effects on NF-kB and CSN5, could be efficient cancer therapies with limited adverse effects. The study also reveals a novel connection between inflammation and tumor immune evasion and, as such, has identified a new means of enhancing checkpoint blockade. REFERENCES Baud, V., and Karin, M. (2009). Nat. Rev. Drug Discov. 8, 33–40. Chang, C.H., Qiu, J., O’Sullivan, D., Buck, M.D., Noguchi, T., Curtis, J.D., Chen, Q., Gindin, M., Gubin, M.M., van der Windt, G.J., et al. (2015). Cell 162, 1229–1241. Grivennikov, S.I., Greten, F.R., and Karin, M. (2010). Cell 140, 883–899. Hayden, M.S., and Ghosh, S. (2008). Cell 132, 344–362.
Figure 1. Regulation and Role of PD-L1 Expression in Cancer Cells The proinflammatory tumor microenvironment promotes transcriptional and post-translational upregulation of PD-L1, maintaining checkpoint blockade. Activation of NF-kB, IRF, and STAT family transcription factors increases transcription of the Cd274 gene encoding PD-L1. NF-kB activation, for example downstream of TNF binding to TNFR1, directly induces expression of the COPS5 gene encoding CSN5, which deubiquitinates and stabilizes PD-L1 protein.
suggesting that NF-kB inhibition may have dual effects: targeting tumor cell proliferation and survival, as well as the tumor immune checkpoint. The NF-kB family of transcription factors has been extensively described as a central regulator of both inflammation and tumor-proliferative and cell-survival pathways (Hayden and Ghosh, 2008). Therefore, significant effort has been in-
830 Cancer Cell 30, December 12, 2016
vested to identify NF-kB pathway inhibitors for treatment of cancer. However, adverse side-effects resulting from systemic NF-kB blockade have discouraged their clinical development (Baud and Karin, 2009). The present study reaffirms the therapeutic potential of some potent NFkB inhibitors and suggests that co-administration of such inhibitors with checkpointblockade therapies may be especially
Li, C.W., Lim, S.O., Xia, W., Lee, H.H., Chan, L.C., Kuo, C.W., Khoo, K.H., Chang, S.S., Cha, J.H., Kim, T., et al. (2016). Nat. Commun. 7, 12632. Lim, S.-O., Li, C.-W., Xia, W., Cha, J.-H., Chan, L.-C., Wu, Y., Chang, S.-S., Lin, W.-C., Hsu, J.-M., Hsu, Y.-H., et al. (2016). Cancer Cell 30, this issue, 925–939. Pan, Y., Wang, S., Su, B., Zhou, F., Zhang, R., Xu, T., Zhang, R., Leventaki, V., Drakos, E., Liu, W., and Claret, F.X. (2016). Oncogene. Published online August 15, 2016. http://dx.doi.org/10.1038/ onc.2016.271. Ritprajak, P., and Azuma, M. (2015). Oral Oncol. 51, 221–228. Wu, P., Wu, D., Li, L., Chai, Y., and Huang, J. (2015). PLoS One 10, e0131403. Zou, W., Wolchok, J.D., and Chen, L. (2016). Sci. Transl. Med. 8, 328rv4.
Previews A Novel Link between Inflammation and Cancer Yenkel Grinberg-Bleyer1 and Sankar Ghosh1,* 1Department of Microbiology & Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA *Correspondence: [email protected] http://dx.doi.org/10.1016/j.ccell.2016.11.013
Immune checkpoint-blockade treatments targeting PD-1/PD-L1 have revolutionized cancer therapy. Hence, understanding the regulation of PD-L1 expression has major clinical relevance. In this issue of Cancer Cell, Lim et al. report that inflammation-induced and NF-kB-driven expression of deubiquitinating enzyme CSN5 leads to PD-L1 stabilization and immune suppression in tumors. The role of innate immunity-mediated inflammation in cancer biology is still debated. However, in most instances, inflammatory cytokines such as tumor necrosis factor (TNF) or IL-6 have been shown to enhance tumor survival, proliferation, or angiogenesis (Grivennikov et al., 2010). Moreover, through the expression of certain cytokines, metabolites, and membrane receptors, macrophages and myeloid-derived suppressor cells (MDSCs) can inhibit adaptive anti-tumor responses. Suppression of effector immune responses in the tumor microenvironment is a central mechanism of tumor escape. In the past decade, the concept of immune checkpoint has emerged through the identification of several molecular pathways that skew effector immunity toward tolerance. Among these, inhibition of CD4 and CD8 T cells by the B7/CTLA-4 and PD-L1/ PD-1 pathways has led to novel therapeutic approaches for treatment of cancer— namely, immune checkpoint blockade. Antibodies targeting both pathways have demonstrated promising clinical outcomes in melanoma and lung cancer. Programmed death ligand 1 (PD-L1, also named B7-H1 or CD274) is a transmembrane protein of the B7 family that is expressed by a variety of cancer cells and by tumor-infiltrating immune cells, including dendritic cells and macrophages (Zou et al., 2016). PD-L1 binds to its receptor PD-1 on the surface of T cells and inhibits proliferation, survival, and the secretion of effector cytokines such as interferon-gamma (IFN-g) or interleukin-2 (IL-2). This eventually results in T cell exhaustion. Besides this direct effect on T cells, it has been proposed that PD-L1 signaling in tumor cells may promote their proliferation and survival by maintaining an optimal metabolic profile (Chang et al., 2015).
High expression of surface PD-L1 by solid tumors and tumor-infiltrating myeloid cells appears to be globally associated with poor prognosis, even though observations can be variable (Wu et al., 2015). Also, the correlation between PD-L1 expression status and clinical response to PD-1 blockade is under scrutiny. Thus, understanding how PDL1 expression is regulated has important clinical applications. Expression of the PD-L1 (Cd274) gene can be induced by Toll-like receptor (TLR) or IFN-g-driven nuclear factor-kappa B (NF-kB), signal transducer and activator of transcription 1 and 3 (STAT1/3), and interferon regulatory factor 1 (IRF1) activity, as well as by hypoxia-inducible factor 1 (HIF-1a) (Ritprajak and Azuma, 2015). After transcription, PD-L1 mRNA can be targeted for degradation by the microRNAs 513 and 570. However, how PD-L1 is regulated at the protein level is poorly understood. A recent paper from the Hung lab showed that mature PD-L1 was glycosylated at four independent residues upon epidermal growth factor receptor (EGFR) stimulation of mouse and human breast cancer cells, leading to its stabilization (Li et al., 2016). In the absence of glycosylation, PD-L1 was phosphorylated by glycogen synthase kinase 3-beta (GSK3b), which induced its K48-ubiquitination and subsequent degradation. In the current issue of Cancer Cell, the same group now shows that PD-L1 stability is also maintained by the active deubiquitination of PD-L1 by the fifth element of the COP9 signalosome (CSN5) protein (also named Jab1, and encoded by COPS5) (Lim et al., 2016). The CSN complex has previously been shown to act as a modulator of intracellular signaling though its deneddylation activity. Specifically, the tumor suppressors p27, p53, and Smad4
can be targeted by CSN5, thereby conferring a pro-tumoral function to CSN5. CSN5 was also shown to serve as a deubiquitinase in breast cancer and 293 kidney epithelial cells, through its JAMM domain. Additionally, high expression of CSN5 is often correlated with poor outcome in patients with ovarian cancer, nasopharyngeal carcinoma, or lymphoma (Pan et al., 2016). Lim et al. now make the observation that macrophage-derived TNF enhances immunosuppression and tumor growth by increasing PD-L1 protein expression without changing mRNA levels. Using elegant mass spectrometry experiments, they identified CSN5 as a TNF-induced PD-L1-bound protein. Upon binding to PD-L1 through its C-terminal domain, CSN5 removes K48-linked ubiquitin on PD-L1, hence increasing PD-L1 protein stability. Expression of CSN5 mRNA was induced by TNF simulation and was dependent on the NF-kB subunit RelA/ p65, which directly regulated CSN5 expression by binding to its promoter. This involvement of NF-kB complements previous observations describing a function for STAT-3 in the spontaneous CSN5 overexpression in nasopharyngeal cancer cells (Figure 1). Interestingly, CSN5 knockdown in breast cancer cells led to impaired growth in vivo. In agreement with these findings, the authors also observed that in vivo administration of the NF-kB inhibitor, curcumin, synergized with anti-CTLA-4 checkpoint-blockade therapy to reduce the growth of breast cancer, colon carcinoma, and melanoma cell lines. Curcumin has long been described as an anti-cancer compound affecting NF-kB-mediated survival and proliferation. In this study, its therapeutic effect in this new set of data seems to rely on inhibition of CSN5,
Cancer Cell 30, December 12, 2016 ª 2016 Elsevier Inc. 829
Cancer Cell
Previews
effective. The safety of such approaches is of the highest importance; here the authors show that certain natural molecules known to have low toxicity, such as curcumin, through its effects on NF-kB and CSN5, could be efficient cancer therapies with limited adverse effects. The study also reveals a novel connection between inflammation and tumor immune evasion and, as such, has identified a new means of enhancing checkpoint blockade. REFERENCES Baud, V., and Karin, M. (2009). Nat. Rev. Drug Discov. 8, 33–40. Chang, C.H., Qiu, J., O’Sullivan, D., Buck, M.D., Noguchi, T., Curtis, J.D., Chen, Q., Gindin, M., Gubin, M.M., van der Windt, G.J., et al. (2015). Cell 162, 1229–1241. Grivennikov, S.I., Greten, F.R., and Karin, M. (2010). Cell 140, 883–899. Hayden, M.S., and Ghosh, S. (2008). Cell 132, 344–362.
Figure 1. Regulation and Role of PD-L1 Expression in Cancer Cells The proinflammatory tumor microenvironment promotes transcriptional and post-translational upregulation of PD-L1, maintaining checkpoint blockade. Activation of NF-kB, IRF, and STAT family transcription factors increases transcription of the Cd274 gene encoding PD-L1. NF-kB activation, for example downstream of TNF binding to TNFR1, directly induces expression of the COPS5 gene encoding CSN5, which deubiquitinates and stabilizes PD-L1 protein.
suggesting that NF-kB inhibition may have dual effects: targeting tumor cell proliferation and survival, as well as the tumor immune checkpoint. The NF-kB family of transcription factors has been extensively described as a central regulator of both inflammation and tumor-proliferative and cell-survival pathways (Hayden and Ghosh, 2008). Therefore, significant effort has been in-
830 Cancer Cell 30, December 12, 2016
vested to identify NF-kB pathway inhibitors for treatment of cancer. However, adverse side-effects resulting from systemic NF-kB blockade have discouraged their clinical development (Baud and Karin, 2009). The present study reaffirms the therapeutic potential of some potent NFkB inhibitors and suggests that co-administration of such inhibitors with checkpointblockade therapies may be especially
Li, C.W., Lim, S.O., Xia, W., Lee, H.H., Chan, L.C., Kuo, C.W., Khoo, K.H., Chang, S.S., Cha, J.H., Kim, T., et al. (2016). Nat. Commun. 7, 12632. Lim, S.-O., Li, C.-W., Xia, W., Cha, J.-H., Chan, L.-C., Wu, Y., Chang, S.-S., Lin, W.-C., Hsu, J.-M., Hsu, Y.-H., et al. (2016). Cancer Cell 30, this issue, 925–939. Pan, Y., Wang, S., Su, B., Zhou, F., Zhang, R., Xu, T., Zhang, R., Leventaki, V., Drakos, E., Liu, W., and Claret, F.X. (2016). Oncogene. Published online August 15, 2016. http://dx.doi.org/10.1038/ onc.2016.271. Ritprajak, P., and Azuma, M. (2015). Oral Oncol. 51, 221–228. Wu, P., Wu, D., Li, L., Chai, Y., and Huang, J. (2015). PLoS One 10, e0131403. Zou, W., Wolchok, J.D., and Chen, L. (2016). Sci. Transl. Med. 8, 328rv4.