Host‐pathogen interactions play an important role in defining the outcome of a disease. Recent studies have shown that the bacterial quorum sensing molecules (QSM) can interact with host cell membrane proteins, mainly G protein‐coupled receptors (GPCRs), and induce innate immune responses. However, few studies have examined QSM‐GPCR interactions and their influence on oral innate immune responses. In this study, we examined the role of bitter taste receptor T2R14 in sensing competence stimulating peptides (CSPs) secreted by cariogenic bacterium Streptococcus mutans and in mediating innate immune responses in gingival epithelial cells (GECs). Transcriptomic and western blot analyses identify T2R14 to be highly expressed in GECs. Our data show that only CSP‐1 from S. mutans induces robust intracellular calcium mobilization compared to CSP‐2 and CSP‐3. By using CRISPR‐Cas9, we demonstrate that CSP‐1 induced calcium signaling and secretion of cytokines CXCL‐8/IL‐8, TNF‐α, and IL‐6 is mediated through T2R14 in GECs. Interestingly, the NF‐kB signaling activated by CSP‐1 in GECs was independent of T2R14. CSP‐1‐primed GECs attracted differentiated HL‐60 immune cells (dHL‐60) and this effect was abolished in T2R14 knock down GECs and also in cells primed with T2R14 antagonist 6‐Methoxyflavone (6‐MF). Our findings identify S. mutans CSP‐1 as a peptide ligand for the T2R family. Our study establishes a novel host‐pathogen interaction between cariogenic S. mutans CSP‐1 and T2R14 in GECs leading to an innate immune response. Collectively, these findings suggest T2Rs as potential therapeutic targets to modulate innate immune responses upon oral bacterial infections.

Bitter-taste receptors (T2Rs) have emerged as key players in host–pathogen interactions and important modulators of oral innate immunity. Previously, we reported that T2R14 is expressed in gingival epithelial cells (GECs) and interacts with competence stimulating peptides (CSPs) secreted by the cariogenic Streptococcus mutans. The underlying mechanisms of the innate immune responses and physiological effects of T2R14 on Gram-positive bacteria are not well characterized. In this study, we examined the role of T2R14 in internalization and growth inhibitory effects on Gram-positive bacteria, namely Staphylococcus aureus and S. mutans. We utilized CRISPR-Cas9 T2R14 knockdown (KD) GECs as the study model to address these key physiological mechanisms. Our data reveal that the internalization of S. aureus is significantly decreased, while the internalization of S. mutans remains unaffected upon knockdown of T2R14 in GECs. Surprisingly, GECs primed with S. mutans CSP-1 resulted in an inhibition of growth for S. aureus, but not for S. mutans. The GECs infected with S. aureus induced T2R14-dependent human β-defensin-2 (hBD-2) secretion; however, S. mutans–infected GECs did not induce hBD-2 secretion, but induced T2R14 dependent IL-8 secretion. Interestingly, our results show that T2R14 KD affects the cytoskeletal reorganization in GECs, thereby inhibiting S. aureus internalization. Our study highlights the distinct mechanisms and a direct role of T2R14 in influencing physiological responses to Gram-positive bacteria in the oral cavity.

Background: Expression of the small calcium-binding protein S100A4 is associated with poor prognosis in patients with thyroid cancer (TC). The authors have previously shown that S100A4 is a target for relaxin and insulin-like peptide 3 signaling in TC cells and that S100A4 is secreted from human TC cells. Although the pro-migratory role of intracellular S100A4 in binding to non-muscle myosin is well known, this study investigated here whether extracellular S100A4 contributes to TC migration. Methods: Human cell lines of follicular, papillary, and undifferentiated thyroid cancer, primary patient TC cells, and TC tissues were utilized to discover the presence of the receptor of advanced glycation end products (RAGE) in TC cells and TC tissues. Fluorescence imaging, protein pull-down assays, Western blot, siRNA protein silencing, small GTPase inhibitors, cell proliferation, and cell migration assays were used to investigate the interaction of extracellular S100A4 with RAGE in promoting a TC migratory response. Results: It was demonstrated that RAGE served as receptor for extracellular S100A4 mediating cell migration in TC cells. The RAGE-mediated increase in cell migration was dependent on the intracellular RAGE signaling partner diaphanous-1 (Dia-1) and involved the activation of the small GTPases Cdc42 and RhoA. Although extracellular S100A4 consistently activated ERK signaling in TC cells, it was shown that ERK signaling was not mediated by RAGE and not essential for the migratory response in TC cells. Conclusion: The data have identified the RAGE/Dia-1 signaling system as a mediator for the pro-migratory response of extracellular S100A4 in human TC. Thus, therapeutic targeting of the RAGE/Dia-1/small GTPases signaling may successfully reduce local invasion and metastasis in TC.

Tissue invasion, metastasis and therapeutic resistance to anti-cancer treatments are common and main causes of death in cancer patients. Tumor cells mount complex and still poorly understood molecular defense mechanisms to counteract and evade oxygen deprivation, nutritional restrictions as well as radio- and chemotherapeutic treatment regimens aimed at destabilizing their genomes and important cellular processes. In thyroid cancer, as in other tumors, such defense strategies include the reactivation in cancer cells of early developmental programs normally active exclusively in stem cells, the stimulation of cancer stem-like cells resident within the tumor tissue and the recruitment of bone marrow-derived progenitors into the tumor (Thomas et al., 2008;Klonisch et al., 2009;Derwahl, 2011). Metastasis and therapeutic resistance in cancer (stem) cells involves the epithelial-to-mesenchymal transition- (EMT-) mediated enhancement in cellular plasticity, which includes coordinated dynamic biochemical and nuclear changes (Ahmed et al., 2010). The purpose of the present review is to provide an overview of the role of DNA repair mechanisms contributing to therapeutic resistance in thyroid cancer and highlight the emerging roles of autophagy and damage associated molecular pattern (DAMP) responses in EMT and chemoresistance in tumor cells. Finally, we use the stem cell factor and nucleoprotein High Mobility Group A2 (HMGA2) as an example to demonstrate how factors intended to protect stem cells are wielded by cancer (stem) cells to gain increased transformative cell plasticity which enhances metastasis, therapeutic resistance and cell survival. Wherever possible, we have included information on these cellular processes and associated factors as they relate to thyroid cancer cells.

Poly(ADP‐ribose) polymerase 1 inhibitors alone or in combination with DNA damaging agents are promising clinical drugs in the treatment of cancer. However, there is a need to understand the molecular mechanisms of resistance to PARP1 inhibitors. Expression of HMGA2 in cancer is associated with poor prognosis for patients. Here, we investigated the novel relationship between HMGA2 and PARP1 in DNA damage‐induced PARP1 activity. We used human triple‐negative breast cancer and fibrosarcoma cell lines to demonstrate that HMGA2 colocalizes and interacts with PARP1. High cellular HMGA2 levels correlated with increased DNA damage‐induced PARP1 activity, which was dependent on functional DNA‐binding AT‐hook domains of HMGA2. HMGA2 inhibited PARP1 trapping to DNA and counteracted the cytotoxic effect of PARP inhibitors. Consequently, HMGA2 decreased caspase 3/7 induction and increased cell survival upon treatment with the alkylating methyl methanesulfonate alone or in combination with the PARP inhibitor AZD2281 (olaparib). HMGA2 increased mitochondrial oxygen consumption rate and spare respiratory capacity and increased NAMPT levels, suggesting metabolic support for enhanced PARP1 activity upon DNA damage. Our data showed that expression of HMGA2 in cancer cells reduces sensitivity to PARP inhibitors and suggests that targeting HMGA2 in combination with PARP inhibition may be a promising new therapeutic approach.