Stimulation of the toll-like receptor 3 promotes metabolic reprogramming in head and neck carcinoma cells

Abstract

In this study, a possible link between the innate immune recognition receptor TLR3 and metabolic reprogramming in Head and Neck carcinoma (HNC) cells was investigated. The effects of TLR3 stimulation/knock-down were assessed under several culture conditions in 4 HNC cell-lines by cell growth assays, targeted metabolomics, and glycolysis assays based on time-resolved analysis of proton release (Seahorse analyzer). The stimulation of TLR3 by its synthetic agonist Poly(A:U) resulted in a faster growth of HNC cells under low foetal calf serum conditions. Targeted analysis of glucose metabolism pathways demonstrated a tendency towards a shift from tricarboxylic acid cycle (Krebs cycle) to glycolysis and anabolic reactions in cells treated with Poly(A:U). Glycolysis assays confirmed that TLR3 stimulation enhanced the capacity of malignant cells to switch from oxidative phosphorylation to extra-mitochondrial glycolysis. We found evidence that HIF-1α is involved in this process: addition of the TLR3 agonist resulted in a higher cell concentration of the HIF-1α protein, even in normoxia, whereas knocking-down TLR3 resulted in a lower concentration, even in hypoxia. Finally, we assessed TLR3 expression by immunohistochemistry in a series of 7 HNSCC specimens and found that TLR3 was detected at higher levels in tumors displaying a hypoxic staining pattern. Overall, our results demonstrate that TLR3 stimulation induces the Warburg effect in HNC cells in vitro, and suggest that TLR3 may play a role in tumor adaptation to hypoxia.

Clinical and Pre-Clinical Evidence of Carbonic Anhydrase IX in Pancreatic Cancer and Its High Expression in Pre-Cancerous Lesions

“…The expressions of some TLRs and HIF-1α correlate [104,119] and prominent expression of HIF-1α, TLRs, and CAIX can be found as early as in PanINs [104]. Conversely, TLR3 was shown to induce the Warburg effect and aid tumor cells in adapting to the hypoxic milieu [102], whereas HIF-1α and TLR4 may synergistically promote development of pancreatic cancer [119].…”

“…Damage-associated molecular patterns (DAMPs) are released upon stress, e.g., cellular injury, inflammation, or tissue damage [101] to stimulate toll-like receptors (TLRs), a subgroup of pattern recognition receptors (PRRs). TLRs enable cancer cells to undergo the switch from oxidative phosphorylation to glycolysis [102] and drive pancreatic stromal inflammation [103]. Toll-like receptor expression depends on PanIN grade [104], increases as cancer progresses [105], and is associated with metastases [106].…”

Genetic variant of IRAK2 in the toll‐like receptor signaling pathway and survival of non‐small cell lung cancer

“…reported that the TLR signaling pathway promoted cell proliferation of pancreatic cancer, emphasizing a particular role of TLR2, TLR‐4, and TLR‐9 in the process . Likewise, TLR3 was found to stimulate cancer cell survival, proliferation, and progression in cancers of the pharynx, breasts and head and neck . For lung cancer, the TLR pathway may play a key role in tumorigenesis and progression, especially for NSCLC .…”

“…14 Likewise, TLR3 was found to stimulate cancer cell survival, proliferation, and progression in cancers of the pharynx, 15 breasts 16 and head and neck. 17 For lung cancer, the TLR pathway may play a key role in tumorigenesis and progression, especially for NSCLC. [18][19][20] Therefore, some genetic variants in genes of this pathway may have a predictive value as a clinically potential biomarker for outcomes of NSCLC.…”

Trial Watch: Toll-like receptor agonists in cancer immunotherapy

“…59 As a family, TLRs are expressed by multiple immune cells, including macrophages, dendritic cells (DCs), B cells, and natural killer (NK) cells, as well as by non-immune cells including epithelial cells, fibroblasts and malignant cells. [60][61][62] Thus, besides controlling the activation, maturation and immunological functions of immune cells (notably cytokine secretion), [63][64][65][66][67][68][69] TLR signaling can influence tumor metabolism, proliferation and dissemination.- 60,62,[70][71][72][73][74][75] Several TLR ligands demonstrated potential therapeutic efficacy against malignant disorders. 70,76 Imiquimod, also called Aldara® (imiquimod 5% cream as commercialized by 3M Pharmaceuticals) or R-837, is a TLR7 agonist that is approved by the US Food and Drug Administration (FDA) for the treatment of actinic keratosis, external genital/perianal warts (condylomata acuminata), and superficial basal cell carcinoma.…”