Targeting inflammatory pathways for tumor radiosensitization.
Although radiation therapy (RT) is an integral component of treatment of patients with many types of cancer, inherent and/or acquired resistance to the cytotoxic effects of RT is increasingly recognized as a significant impediment to effective cancer treatment. Inherent resistance is mediated by constitutively activated oncogenic, proliferative and anti-apoptotic proteins/pathways whereas acquired resistance refers to transient induction of proteins/pathways following radiation exposure. To realize the full potential of RT, it is essential to understand the signaling pathways that mediate inducible radiation resistance, a poorly characterized phenomenon, and identify druggable targets for radiosensitization. Ionizing radiation induces a multilayered signaling response in mammalian cells by activating many pro-survival pathways that converge to transiently activate a few important transcription factors (TFs), including nuclear factor kappa B (NF-κB) and signal transducers and activators of transcription (STATs), the central mediators of inflammatory and carcinogenic signaling. Together, these TFs activate a wide spectrum of pro-survival genes regulating inflammation, anti-apoptosis, invasion and angiogenesis pathways, which confer tumor cell radioresistance. Equally, radiation-induced activation of pro-inflammatory cytokine network (including interleukin (IL)-1β, IL-6 and tumor necrosis factor-α) has been shown to mediate symptom burden (pain, fatigue, local inflammation) in cancer patients. Thus, targeting radiation-induced inflammatory pathways may exert a dual effect of accentuating the tumor radioresponse and reducing normal tissue side-effects, thereby increasing the therapeutic window of cancer treatment. We review recent data demonstrating the pivotal role played by inflammatory pathways in cancer progression and modulation of radiation response.
Deorukhkar
Amit
A
Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Krishnan
Sunil
S
D000818:Animals; D051546:Cyclooxygenase 2 / Q000502:physiology; D016207:Cytokines / Q000378:metabolism; D018450:Disease Progression; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000517:prevention & control; D058990:Molecular Targeted Therapy; D016328:NF-kappa B / Q000502:physiology; D009369:Neoplasms / Q000276:immunology / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011836:Radiation Tolerance / Q000187:drug effects; D050791:STAT Transcription Factors / Q000502:physiology
D016207:Cytokines; D016328:NF-kappa B; D050791:STAT Transcription Factors; D051546:Cyclooxygenase 2