Targeting the STAT Pathway in Head and Neck Cancer: Recent Advances and Future Prospects

Abstract

Head and neck cancer, the sixth most common type of cancer worldwide, is associated with a dismal prognosis that has minimally improved during the last few decades. Future advances in the treatment and prognosis of this fatal disease largely rely upon a better understanding of the molecular events that underlie tumor development and progression, allowing specific targeting of the involved molecules and pathways. In this context, recent efforts have revolved around a family of transcription factors known as STATs (signal transducers and activators of transcription). STAT proteins comprise a family of latent cytoplasmic transcription factors that become transiently activated in response to extracellular signals, leading to regulation of diverse physiological responses. There is compelling evidence that persistent activation of specific STAT molecules, especially Stat3 and Stat5, possesses oncogenic properties in a number of human cancers, including head and neck cancer. The presence of constitutively activated STAT molecules in cancer cells is mainly attributed to the dysregulation of upstream activating pathways and the aberration of negative regulatory mechanisms. The end result is induction of specific target genes that stimulate cell proliferation, prevent apoptosis, promote angiogenesis and facilitate tumor immune evasion. Therefore, targeting and disruption of oncogenic STAT signaling may theoretically be accomplished through various approaches, involving direct (e.g. interference with the various facets of STAT expression, activation or function) and indirect strategies (e.g. inhibition of upstream signaling events and enhancement or restoration of negative regulatory mechanisms). The availability of multiple potential targets for interruption of aberrant STAT signaling in cancer and the thus-far promising results have generated optimism for the clinical applicability of STAT targeting in head and neck cancer, which is the focus of this review.

Erk1/2 activation and modulation of STAT3 signaling in oral cancer

“…Aberrant STAT3 activation, manifested by increases in STAT3 tyrosine phosphorylation, is considered as a potent promoter of HNSCC initiation and progression, thereby inhibition of STAT3 has been identified as a potential therapeutic target for the treatment of HNSCC (16,18,62). STAT3 constitutive activation in HNSCC is driven by a number of upstream signal transduction pathways.…”

“…There is compelling evidence that STAT3 constitutive activation, mainly associated with aberrant TGF-α/EGFR signaling, is linked to HNSCC development and growth (2,(14)(15)(16)(17)(18). Previous findings suggested the existence of EGFRindependent STAT oncogenic properties in HNSCC, including autocrine/paracrine cytokine (IL-6, IL-10 or IL-22) stimulation or signaling through 7 nicotinic and erythropoietin receptor pathways (17,(19)(20)(21)(22)(23).…”

STAT1 activation in squamous cell cancer of the oral cavity

“…28 STAT3 activation has been shown to be crucial for tumor growth in animal models of SCCHN, and inhibition of STAT3 activity is an interesting therapeutic option. [32][33][34] However, there are no data that suggest usefulness of STAT3 as a marker to predict response to conventional chemotherapy in SCCHN patients.…”

Protein Kinase Cε Interacts with Signal Transducers and Activators of Transcription 3 (Stat3), Phosphorylates Stat3Ser727, and Regulates Its Constitutive Activation in Prostate Cancer

“…Stat activation is linked to cell proliferation, differentiation, apoptosis, embryogenesis, and immune responses (8)(9)(10)(11). Stats exhibit functional divergence in their roles in oncogenesis.…”