Cyanine Dye Conjugation Enhances Crizotinib Localization to Intracranial Tumors, Attenuating NF-κB-Inducing Kinase Activity and Glioma Progression.

Glioblastoma (GBM) is a highly aggressive form of brain cancer with a poor prognosis and limited treatment options. The ALK and c-MET inhibitor Crizotinib has demonstrated preclinical therapeutic potential for newly diagnosed GBM, although its efficacy is limited by poor penetration of the blood brain barrier. Here, we identify Crizotinib as a novel inhibitor of nuclear factor-κB (NF-κB)-inducing kinase, which is a key regulator of GBM growth and proliferation. We further show that the conjugation of Crizotinib to a heptamethine cyanine dye, or a near-infrared dye (IR-Crizotinib), attenuated glioma cell proliferation and survival in vitro to a greater extent than unconjugated Crizotinib. Moreover, we observed increased IR-Crizotinib localization to orthotopic mouse xenograft GBM tumors, which resulted in impaired tumor growth in vivo. Overall, IR-Crizotinib exhibited improved intracranial chemotherapeutic delivery and tumor localization with concurrent inhibition of NIK and noncanonical NF-κB signaling, thereby reducing glioma growth in vitro, as well as in vivo, and increasing survival in a preclinical rodent model.

Transcriptional induction of NF-κB-inducing kinase by E2F4/5 facilitates collective invasion of GBM cells.

The prognosis of high-grade gliomas, such as glioblastoma multiforme (GBM), is extremely poor due to the highly invasive nature of these aggressive cancers. Previous work has demonstrated that TNF-weak like factor (TWEAK) induction of the noncanonical NF-κB pathway promotes the invasiveness of GBM cells in an NF-κB-inducing kinase (NIK)-dependent manner. While NIK activity is predominantly regulated at the posttranslational level, we show here that NIK (MAP3K14) is upregulated at the transcriptional level in invading cell populations, with the highest NIK expression observed in the most invasive cells. GBM cells with high induction of NIK gene expression demonstrate characteristics of collective invasion, facilitating invasion of neighboring cells. Furthermore, we demonstrate that the E2F transcription factors E2F4 and E2F5 directly regulate NIK transcription and are required to promote GBM cell invasion in response to TWEAK. Overall, our findings demonstrate that transcriptional induction of NIK facilitates collective cell migration and invasion, thereby promoting GBM pathogenesis.

NF-κB-inducing kinase maintains mitochondrial efficiency and systemic metabolic homeostasis.

NF-κB-inducing kinase (NIK) is an essential upstream inducer of noncanonical NF-κB signaling and a critical regulator of immunity and inflammation. Our recent work has demonstrated that NIK regulates mitochondrial respiration and adaptive metabolic responses in cancer and innate immune cells. However, it is not clear whether NIK also has roles in regulating systemic metabolism. In this study, we demonstrate that NIK has local and systemic effects on developmental and metabolic processes. Our findings show that NIK-deficient mice exhibit reduced adiposity, as well as elevated energy expenditure both basally, and under the stress of a high-fat diet. Moreover, we identify NF-κB-independent and -dependent functions for NIK in white adipose tissue metabolism and development. Specifically, we found that in an NF-κB-independent manner NIK is required for maintaining mitochondrial fitness, as NIK-deficient adipocytes have impaired mitochondrial membrane potential and spare respiratory capacity. In addition to mitochondrial exhaustion, NIK-deficient adipocytes and ex vivo adipose tissue exhibit a compensatory upregulation of glycolysis to meet bioenergetic demands. Finally, while NIK regulation of mitochondrial metabolism in preadipocytes is NF-κB-independent, we demonstrate that NIK has a complementary role in adipocyte differentiation that requires activation of RelB and the noncanonical NF-κB pathway. Collectively, these data demonstrate that NIK has critical roles in local and systemic development and metabolism. Our findings establish NIK as an important regulator of organelle, cell, and systemic metabolic homeostasis, suggesting that metabolic dysfunction may be an important and unappreciated component of immune disorders and inflammatory diseases arising from NIK deficiency.

NIK promotes metabolic adaptation of glioblastoma cells to bioenergetic stress.

Cancers, including glioblastoma multiforme (GBM), undergo coordinated reprogramming of metabolic pathways that control glycolysis and oxidative phosphorylation (OXPHOS) to promote tumor growth in diverse tumor microenvironments. Adaptation to limited nutrient availability in the microenvironment is associated with remodeling of mitochondrial morphology and bioenergetic capacity. We recently demonstrated that NF-κB-inducing kinase (NIK) regulates mitochondrial morphology to promote GBM cell invasion. Here, we show that NIK is recruited to the outer membrane of dividing mitochondria with the master fission regulator, Dynamin-related protein1 (DRP1). Moreover, glucose deprivation-mediated metabolic shift to OXPHOS increases fission and mitochondrial localization of both NIK and DRP1. NIK deficiency results in decreased mitochondrial respiration, ATP production, and spare respiratory capacity (SRC), a critical measure of mitochondrial fitness. Although IκB kinase α and ß (IKKα/ß) and NIK are required for OXPHOS in high glucose media, only NIK is required to increase SRC under glucose deprivation. Consistent with an IKK-independent role for NIK in regulating metabolism, we show that NIK phosphorylates DRP1-S616 in vitro and in vivo. Notably, a constitutively active DRP1-S616E mutant rescues oxidative metabolism, invasiveness, and tumorigenic potential in NIK-/- cells without inducing IKK. Thus, we establish that NIK is critical for bioenergetic stress responses to promote GBM cell pathogenesis independently of IKK. Our data suggest that targeting NIK may be used to exploit metabolic vulnerabilities and improve therapeutic strategies for GBM.

Targeting NF-κB-Inducing Kinase (NIK) in Immunity, Inflammation, and Cancer.

NF-κB-inducing kinase (NIK), the essential upstream kinase, which regulates activation of the noncanonical NF-κB pathway, has important roles in regulating immunity and inflammation. In addition, NIK is vital for maintaining cellular health through its control of fundamental cellular processes, including differentiation, growth, and cell survival. As such aberrant expression or regulation of NIK is associated with several disease states. For example, loss of NIK leads to severe immune defects, while the overexpression of NIK is observed in inflammatory diseases, metabolic disorders, and the development and progression of cancer. This review discusses recent studies investigating the therapeutic potential of NIK inhibitors in various diseases.