Skip to main content
  • AACR Publications
    • Blood Cancer Discovery
    • Cancer Discovery
    • Cancer Epidemiology, Biomarkers & Prevention
    • Cancer Immunology Research
    • Cancer Prevention Research
    • Cancer Research
    • Clinical Cancer Research
    • Molecular Cancer Research
    • Molecular Cancer Therapeutics

AACR logo

  • Register
  • Log in
  • My Cart
Advertisement

Main menu

  • Home
  • About
    • The Journal
    • AACR Journals
    • Journal Sections
    • Subscriptions
    • Permissions and Reprints
  • Articles
    • OnlineFirst
    • Current Issue
    • Past Issues
    • Collections
      • COVID-19 & Cancer Resource Center
      • Clinical Trials
      • Immuno-oncology
      • Editors' Picks
      • "Best of" Collection
  • For Authors
    • Information for Authors
    • Author Services
    • Best of: Author Profiles
    • Submit
  • Alerts
    • Table of Contents
    • Editors' Picks
    • OnlineFirst
    • Citation
    • Author/Keyword
    • RSS Feeds
    • My Alert Summary & Preferences
  • News
    • Cancer Discovery News
    • Journal Press Releases
  • COVID-19
  • Webinars
  • 10th Anniversary
  • Search More

    Advanced Search

  • AACR Publications
    • Blood Cancer Discovery
    • Cancer Discovery
    • Cancer Epidemiology, Biomarkers & Prevention
    • Cancer Immunology Research
    • Cancer Prevention Research
    • Cancer Research
    • Clinical Cancer Research
    • Molecular Cancer Research
    • Molecular Cancer Therapeutics

User menu

  • Register
  • Log in
  • My Cart

Search

  • Advanced search
Cancer Discovery
Cancer Discovery
  • Home
  • About
    • The Journal
    • AACR Journals
    • Journal Sections
    • Subscriptions
    • Permissions and Reprints
  • Articles
    • OnlineFirst
    • Current Issue
    • Past Issues
    • Collections
      • COVID-19 & Cancer Resource Center
      • Clinical Trials
      • Immuno-oncology
      • Editors' Picks
      • "Best of" Collection
  • For Authors
    • Information for Authors
    • Author Services
    • Best of: Author Profiles
    • Submit
  • Alerts
    • Table of Contents
    • Editors' Picks
    • OnlineFirst
    • Citation
    • Author/Keyword
    • RSS Feeds
    • My Alert Summary & Preferences
  • News
    • Cancer Discovery News
    • Journal Press Releases
  • COVID-19
  • Webinars
  • 10th Anniversary
  • Search More

    Advanced Search

In the Spotlight

NF-κB in Cancer: A Matter of Life and Death

Bharat B. Aggarwal and Bokyung Sung
Bharat B. Aggarwal
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Bokyung Sung
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
DOI: 10.1158/2159-8290.CD-11-0260 Published November 2011
  • Article
  • Figures & Data
  • Info & Metrics
  • PDF
Loading

Abstract

Activation of NF-κB has been linked to various cellular processes in cancer, including inflammation, transformation, proliferation, angiogenesis, invasion, metastasis, chemoresistance, and radioresistance. Although acute inflammation mediates innate and humoral immunity, chronic inflammation has been linked to tumorigenesis. Thus, inhibition of NF-κB has therapeutic potential in sensitization of tumors to chemotherapeutic agents; however, generalized suppression of NF-κB can result in serious host toxicity with minimum effect on the tumor. Cancer Discovery; 1(6); 469–71. ©2011 AACR.

Commentary on Enzler et al., p. 496.

Introduction

Among all the transcription factors, no transcription factor has been examined more extensively than NF-κB. NF-κB controls the expression of more than 500 different gene products that have been closely linked to inflammation, cellular transformation, tumor cell survival, proliferation, invasion, angiogenesis, and metastasis (1). In addition, this transcription factor is activated in response to a wide variety of stimuli that are shown to be lifestyle risk factors, such as stress (physical, psychological, mechanical, or chemical), tobacco, radiation, asbestos, dietary agents, environmental pollutants, obesity, and various infectious agents closely linked to cancer.

Multiple growth factors linked to proliferation of tumors also activate NF-κB. Among all growth factors, TNF-α is one of the most potent activators of NF-κB. In addition, epidermal growth factor receptor, which is linked to the growth of almost one third of all cancers, also acts in part through NF-κB activation (Fig. 1). The NF-κB activation pathway typically involves activation of NF-κB inhibitor α (IκBα) kinase kinase (known as IKKK), leading to activation of IκBα kinase, phosphorylation, ubiquitination, and degradation of IκBα, nuclear translocation of the p50 and p65 subunits of NF-κB, and consensus DNA binding culminating in NF-κB target gene transcription. Although canonical NF-κB activation is mediated through the activation of IκBα kinase β, noncanonical activation involves IκBα kinase α.

Figure 1.
  • Download figure
  • Open in new tab
  • Download powerpoint
Figure 1.

Pathways leading to NF-κB activation in tumor cells and consequent roles of NF-κB activation in tumorigenesis. ATM, ataxia-telangiectasia mutated; EGF, epidermal growth factor; EGFR, epidermal growth factor receptor; HER2-L, HER2 ligand.

Although NF-κB is a major mediator of both innate and humoral immunity, its activation in organs other than the immune system can cause havoc. In most normal cells, NF-κB exists in its inactive form, but constitutive activation of NF-κB has been noted in almost all cancers. Why NF-κB is constitutively active in most tumor cells is not fully understood. Mechanisms that lead to constitutive activation of NF-κB differ from those of inducible NF-κB activation and may vary from one tumor type to another. Some of the potential mechanisms of constitutive NF-κB activation in different tumor cells have been reviewed recently (2). Cross-talk between NF-κB and various other transcription factors has also been well documented. Most tumor cells are highly “addicted” to the activated form of NF-κB because its inactivation usually leads to the inhibition of tumor cell growth, mostly through the suppression of antiapoptotic and proliferative gene products.

Different types of cancer exploit inflammatory components to improve their lifespan in organs. An array of growth factors and cytokines (e.g., interleukin-1 [IL-1], TNF-α, IL-6, VEGF) supports malignant cell progression and contributes to suppress the body's immune defense. Strategies to modulate the host microenvironment offer new approaches for anticancer therapies. In light of the crucial link between inflammation and cancer, molecules with antitumor and anti-inflammatory features are being looked at with fresh eyes.

The activation of NF-κB in various immune cells, including T cells, B cells, macrophages, dendritic cells, and neutrophils, leads to expression of proinflammatory cytokines required for proliferation. However, NF-κB–mediated activation in the immune system has the potential to suppress tumor growth, in part through the production of growth inhibitory cytokines. An acute proinflammatory microenvironment, as defined by the arrival of neutrophils, blood monocytes, and dendritic cells, plays a critical role in tumor regression. It is chronic inflammation, however, that is known to mediate tumorigenesis. Although M1-type macrophages, activated by IFN-γ, promote the adaptive immune response through the secretion of proinflammatory cytokines, M2-type macrophages activated by IL-4 and IL-13 have been linked to anti-inflammatory signaling and wound healing. NF-κB thus plays an important role in the immune response regardless of the specific macrophage type. Care must therefore be taken with NF-κB inhibition because tumor-associated macrophages are a major component of inflammatory infiltrates in intratumoral or peritumoral tissue of most solid tumors. Yet, although acute activation of NF-κB has therapeutic potential, chronic activation can lead to tumorigenesis (3). How to selectively block NF-κB activation in the tumor remains unclear.

Paradoxically, in addition to lifestyle factors, NF-κB is also activated by most chemotherapeutic agents and radiation used for the treatment of cancer, which then leads to chemoresistance and radioresistance and possibly progression and metastasis of the tumor. Thus, agents that can down-regulate NF-κB are expected to sensitize the tumors to chemotherapy and radiation and prevent metastasis (4). Patients with constitutively active NF-κB normally respond poorly to treatment; therefore, NF-κB status is thus a predictor of overall survival.

In their article in this issue of Cancer Discovery, Enzler et al. (5) demonstrate that the NF-κB signaling pathway is linked to both induction of chemoresistance and host toxicity mediated through two distinct cell type–specific mechanisms. These studies were performed in a melanoma chemotherapy model chosen because the role of NF-κB in the growth and chemoresistance of melanoma is well established (6). The authors performed three distinct sets of experiments. First, they showed in a human melanoma xenograft model that doxorubicin cannot inhibit the growth of the tumor. Furthermore, they found that an IκBα kinase inhibitor (BMS-345541) sensitized the tumor to the chemotherapeutic agent but was highly toxic to the host, in part because of generalized suppression of NF-κB. Second, they showed that after tumor-specific suppression of NF-κB with a repressor of IκBα kinase, doxorubicin induced tumor regression with little damage to the host. Third, when NF-κB was specifically down-regulated in host myeloid cells, doxorubicin caused necrotic tumor lesions through the recruitment of IL-1β–producing neutrophils into the tumor, resulting in increased host mortality with minimum tumor regression. They found that polymorphonuclear leukocytes from these animals produced IL-1β, which caused necrotic lesions in the tumor. The inhibition of NF-κB in the melanoma cells was responsible for the antitumor effects, whereas myeloid-specific inhibition of NF-κB was responsible for the toxicity. Thus, the authors concluded that although tumor-specific suppression of NF-κB is beneficial, generalized suppression of NF-κB is harmful.

These studies are very well done and once again demonstrate the importance of NF-κB in tumor suppression. The studies clearly indicate that NF-κB activation is a “double-edged sword.” Although this transcription factor has therapeutic effects when inhibited in a tumor-specific manner, it could have devastating effects if it is inhibited nonspecifically in the host. As is the case for most cancers, constitutive NF-κB plays a critical role in melanoma [e.g., Schon et al. (7)]. Similar to studies by Enzler et al. (5), Schon et al. (7) also reported that an IκBα kinase β inhibitor (KINK-1) could potentiate the effect of doxorubicin against human melanoma in a xenograft model. When they used campto-thecin instead of doxorubicin, sensitization of the tumor was similar. Pulmonary metastasis was also suppressed by down-regulation of NF-κB. The authors noted minimum host toxicity, perhaps because they used a very low dose (3 mg/kg) of the IκBα kinase inhibitor. Although they used different IκBα kinase inhibitors, Enzler et al. (5) showed that an IκBα kinase inhibitor alone (125 mg/kg) was highly effective in suppressing tumor growth, whereas Amschler et al. (8) showed that IκBα kinase inhibitor alone (3 mg/kg) had no effect on tumor growth, thus suggesting a dose-dependent effect. It is thus possible that the host toxicity observed by Enzler et al. (5) was in part attributable to the high dose used. Amschler et al. (8) reported chemosensitization of melanoma (B16F10) to camptothecin in mice (C57BL/6) when they administered a proteasome inhibitor (bortezomib) that also inhibits NF-κB activation and has been approved by the Food and Drug Administration for use in patients with multiple myeloma. These studies demonstrate that inhibition of NF-κB in the melanoma cells can sensitize the tumors to chemotherapeutic agents. Inhibition of NF-κB in the immune system such as macrophages, however, may exhibit toxicity to the host.

These studies have enormous clinical implications because the NF-κB activation pathway is correlated with response to doxorubicin in patients with breast cancer (9). Similarly, NF-κB activation has also been associated with resistance to chemoradiation and poor outcome in patients with esophageal carcinoma (10). Furthermore, NF-κB activation has also been shown to predict the response and survival of patients with irinotecan-refractory metastatic colorectal cancer treated with cetuximab (an antibody against epidermal growth factor receptor) and irinotecan (11). Collectively, these studies suggest the critical role that NF-κB plays in patients treated with various chemotherapeutic agents, emphasizing again that selective inhibition of NF-κB is critical.

Although suppression of NF-κB in the host system may exhibit harmful effects, suppression of NF-κB in the tumor is beneficial. It is possible that the answer lies in dialing down versus completely suppressing NF-κB. Like most other molecular targets, it is the dysregulation of NF-κB that mediates tumorigenesis and chemoresistance. Thus, low doses of chemical inhibitors may be sufficient for sensitization of tumors to chemotherapeutic agents, as shown by Schon et al. (7). Furthermore, other agents, for example, natural products such as curcumin (the yellow pigment in turmeric) that are known to suppress NF-κB activation both in vitro and in vivo, are pharmacologically safe, highly affordable, and can chemosensitize a variety of tumors (12–14); these alternatives to the dilemma should be considered.

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Grant Support

This work was supported by a core grant from the NIH (CA-16-672) and a program project grant from the NIH (CA-124787-01A2).

Acknowledgments

We thank Walter Pagel for carefully editing the manuscript and providing valuable comments. B.B. Aggarwal is the Ransom Horne, Jr., Professor of Cancer Research.

  • Received October 6, 2011.
  • Accepted October 6, 2011.
  • ©2011 American Association for Cancer Research.

References

  1. 1.↵
    1. Aggarwal BB
    . Nuclear factor-kappaB: the enemy within. Cancer Cell 2004;6:203–8.
    OpenUrlCrossRefPubMed
  2. 2.↵
    1. Chaturvedi MM,
    2. Sung B,
    3. Yadav VR,
    4. Kannappan R,
    5. Aggarwal BB
    . NF-kappaB addiction and its role in cancer: ‘one size does not fit all.’ Oncogene 2011;30:1615–30.
    OpenUrlCrossRefPubMed
  3. 3.↵
    1. Aggarwal BB,
    2. Vijayalekshmi RV,
    3. Sung B
    . Targeting inflammatory pathways for prevention and therapy of cancer: short-term friend, long-term foe. Clin Cancer Res 2009;15:425–30.
    OpenUrlAbstract/FREE Full Text
  4. 4.↵
    1. Nakanishi C,
    2. Toi M
    . Nuclear factor-kappaB inhibitors as sensitizers to anticancer drugs. Nat Rev Cancer 2005;5:297–309.
    OpenUrlCrossRefPubMed
  5. 5.↵
    1. Enzler T,
    2. Sano Y,
    3. Choo M,
    4. Cottam H,
    5. Karin M,
    6. Tsao H,
    7. et al
    . Cell-selective inhibition of NF-κB signaling improves therapeutic index in a melanoma chemotherapy model. Cancer Discovery 2011;1:496–507.
    OpenUrlAbstract/FREE Full Text
  6. 6.↵
    1. Yang J,
    2. Richmond A
    . Constitutive IkappaB kinase activity correlates with nuclear factor-κB activation in human melanoma cells. Cancer Res 2001;61:4901–9.
    OpenUrlAbstract/FREE Full Text
  7. 7.↵
    1. Schon M,
    2. Wienrich BG,
    3. Kneitz S,
    4. Sennefelder H,
    5. Amschler K,
    6. Vohringer V,
    7. et al
    . KINK-1, a novel small-molecule inhibitor of IKKbeta, and the susceptibility of melanoma cells to antitumoral treatment. J Natl Cancer Inst 2008;100:862–75.
    OpenUrlAbstract/FREE Full Text
  8. 8.↵
    1. Amschler K,
    2. Schon MP,
    3. Pletz N,
    4. Wallbrecht K,
    5. Erpenbeck L,
    6. Schon M
    . NF-kappaB inhibition through proteasome inhibition or IKKbeta blockade increases the susceptibility of melanoma cells to cytostatic treatment through distinct pathways. J Invest Dermatol 2010;130:1073–86.
    OpenUrlCrossRefPubMed
  9. 9.↵
    1. Buchholz TA,
    2. Garg AK,
    3. Chakravarti N,
    4. Aggarwal BB,
    5. Esteva FJ,
    6. Kuerer HM,
    7. et al
    . The nuclear transcription factor kappaB/bcl-2 pathway correlates with pathologic complete response to doxorubicin-based neoadjuvant chemotherapy in human breast cancer. Clin Cancer Res 2005;11:8398–402.
    OpenUrlAbstract/FREE Full Text
  10. 10.↵
    1. Izzo JG,
    2. Malhotra U,
    3. Wu TT,
    4. Ensor J,
    5. Luthra R,
    6. Lee JH,
    7. et al
    . Association of activated transcription factor nuclear factor kappab with chemoradiation resistance and poor outcome in esophageal carcinoma. J Clin Oncol 2006;24:748–54.
    OpenUrlAbstract/FREE Full Text
  11. 11.↵
    1. Scartozzi M,
    2. Bearzi I,
    3. Pierantoni C,
    4. Mandolesi A,
    5. Loupakis F,
    6. Zaniboni A,
    7. et al
    . Nuclear factor-kB tumor expression predicts response and survival in irinotecan-refractory metastatic colorectal cancer treated with cetuximab-irinotecan therapy. J Clin Oncol 2007;25:3930–5.
    OpenUrlAbstract/FREE Full Text
  12. 12.↵
    1. Aggarwal BB,
    2. Sung B
    . Pharmacological basis for the role of curcumin in chronic diseases: an age-old spice with modern targets. Trends Pharmacol Sci 2009;30:85–94.
    OpenUrlCrossRefPubMed
  13. 13.
    1. Gupta SC,
    2. Sundaram C,
    3. Reuter S,
    4. Aggarwal BB
    . Inhibiting NF-kappaB activation by small molecules as a therapeutic strategy. Biochim Biophys Acta 2010;1799:775–87.
    OpenUrlCrossRefPubMed
  14. 14.↵
    1. Prasad S,
    2. Phromnoi K,
    3. Yadav VR,
    4. Chaturvedi MM,
    5. Aggarwal BB
    . Targeting inflammatory pathways by flavonoids for prevention and treatment of cancer. Planta Med 2010;76:1044–63.
    OpenUrlCrossRefPubMed
PreviousNext
Back to top
Cancer Discovery: 1 (6)
November 2011
Volume 1, Issue 6
  • Table of Contents
  • Table of Contents (PDF)
  • About the Cover

Sign up for alerts

View this article with LENS

Open full page PDF
Article Alerts
Sign In to Email Alerts with your Email Address
Email Article

Thank you for sharing this Cancer Discovery article.

NOTE: We request your email address only to inform the recipient that it was you who recommended this article, and that it is not junk mail. We do not retain these email addresses.

Enter multiple addresses on separate lines or separate them with commas.
NF-κB in Cancer: A Matter of Life and Death
(Your Name) has forwarded a page to you from Cancer Discovery
(Your Name) thought you would be interested in this article in Cancer Discovery.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Citation Tools
NF-κB in Cancer: A Matter of Life and Death
Bharat B. Aggarwal and Bokyung Sung
Cancer Discov November 1 2011 (1) (6) 469-471; DOI: 10.1158/2159-8290.CD-11-0260

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Share
NF-κB in Cancer: A Matter of Life and Death
Bharat B. Aggarwal and Bokyung Sung
Cancer Discov November 1 2011 (1) (6) 469-471; DOI: 10.1158/2159-8290.CD-11-0260
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
  • Tweet Widget
  • Facebook Like
  • Google Plus One

Jump to section

  • Article
    • Abstract
    • Introduction
    • Disclosure of Potential Conflicts of Interest
    • Grant Support
    • Acknowledgments
    • References
  • Figures & Data
  • Info & Metrics
  • PDF
Advertisement

Related Articles

Cited By...

More in this TOC Section

  • At the Heart of Immune Checkpoint Inhibitor–Induced Immune Toxicity
  • Genetic Ancestry Correlations with Driver Mutations Suggest Complex Interactions between Somatic and Germline Variation in Cancer
  • Poorer Clinical Outcomes for Black Patients with AML: A Wake-Up Call for Better Data and Greater Understanding of Cancer Outcomes in All Ethnic Groups
Show more In the Spotlight
  • Home
  • Alerts
  • Feedback
  • Privacy Policy
Facebook   Twitter   LinkedIn   YouTube   RSS

Articles

  • OnlineFirst
  • Current Issue
  • Past Issues

Info For

  • Authors
  • Subscribers
  • Advertisers
  • Librarians

About Cancer Discovery

  • About the Journal
  • Editors
  • Journal Sections
  • Permissions
  • Submit a Manuscript
AACR logo

Copyright © 2021 by the American Association for Cancer Research.

Cancer Discovery
eISSN: 2159-8290
ISSN: 2159-8274

Advertisement