Isobutyrylshikonin has a potentially stronger cytotoxic effect in oral cancer cells than its analogue shikonin in vitro.

OBJECTIVES: The aim of the present study was to identify the anticancer effects and the mechanisms of action of shikonin and its analogue isobutyrylshikonin in oral squamous carcinoma cells. DESIGNS: The cytotoxic effects of isobutyrylshikonin and shikonin in Ca9-22 and SCC-25 cells were analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry analysis of Annexin V/Propidium Iodide (PI) staining, western blot analysis and immunohistochemistry. RESULTS: Treatment with both isobutyrylshikonin and shikonin induced dose- and time-dependent apoptotic cell death in Ca9-22 cells, although the IC50 of isobutyrylshikonin was less than that of shikonin. The induction of apoptosis by both isobutyrylshikonin and shikonin was accompanied by activation of caspase-8, -9, -3, and PARP, loss of mitochondrial trans-membrane potential, and release of cytochrome c from the mitochondria. ROS mediated the apoptosis induced by isobutyrylshikonin and shikonin, indicating that ROS may play a critical role in the distinctive cytotoxic effects of isobutyrylshikonin and shikonin in Ca9-22. Isobutyrylshikonin showed a similar cytotoxic effect in SCC-25 cells at concentrations showing the effects in Ca9 cells, but not in human normal keratinocyte cells. Although there is no biological difference between isobutyrylshikonin and shikonin, isobutyrylshikonin exerts the same cytotoxic effect at a concentration 6 times lower than shikonin. CONCLUSIONS: The present study suggest that isobutyrylshikonin may be a more potent chemotherapeutic agent against oral cancer cells than shikonin. In addition, our data exhibit that both isobutyrylshikonin and shikonin induce caspase-dependent apoptosis via the mitochondrial pathway through accumulation of ROS in oral squamous carcinoma cells.

Quercetin Inhibits Cell Survival and Metastatic Ability via the EMT-mediated Pathway in Oral Squamous Cell Carcinoma.

This study aimed to investigate whether quercetin exerts anticancer effects on oral squamous cell carcinoma (OSCC) cell lines and to elucidate its mechanism of action. These anticancer effects in OSCC cells were assessed using an MTT assay, flow cytometry (to assess the cell cycle), wound-healing assay, invasion assay, Western blot analysis, gelatin zymography, and immunofluorescence. To investigate whether quercetin also inhibits transforming growth factor ß1 (TGF-ß1)-induced epithelial-mesenchymal transition (EMT) in human keratinocyte cells, HaCaT cells were treated with TGF-ß1. Overall, our results strongly suggest that quercetin suppressed the viability of OSCC cells by inducing cell cycle arrest at the G2/M phase. However, quercetin did not affect cell viability of human keratinocytes such as HaCaT (immortal keratinocyte) and nHOK (primary normal human oral keratinocyte) cells. Additionally, quercetin suppresses cell migration through EMT and matrix metalloproteinase (MMP) in OSCC cells and decreases TGF-ß1-induced EMT in HaCaT cells. In conclusion, this study is the first, to our knowledge, to demonstrate that quercetin can inhibit the survival and metastatic ability of OSCC cells via the EMT-mediated pathway, specifically Slug. Quercetin may thus provide a novel pharmacological approach for the treatment of OSCCs.

Identification of Matrix Metalloproteinase-1-Suppressive Peptides in Feather Keratin Hydrolysate.

Inhibition of matrix metalloproteinases (MMPs), which degrade collagen and elastin in the dermis of normal skin, is a key strategy for anti-skin aging. In this study, we identified five low-molecular-weight (LMW, <1 kDa) MMP-1-suppressive peptides in feather keratin hydrolysate (FKH) obtained by anaerobic digestion with an extremophilic bacterium. FKH was first subjected to ultrafiltration, followed by size-exclusion chromatography and liquid chromatography/electrospray ionization tandem mass spectrometry analysis. Chemically synthesized peptides identical to the sequences identified suppressed MMP expression in human dermal fibroblasts (HDFs). To investigate the impact of the MMP-1-suppressive peptides on the signaling pathway, we performed antibody array phosphorylation profiling of HDFs. The results suggested that the peptide GGFDL regulates ultraviolet-B-induced MMP-1 expression by inhibiting mitogen-activated protein kinases and nuclear factor κB signaling pathways as well as histone modification. Thus, LMW feather keratin peptides could serve as novel bioactive compounds to protect the skin against intrinsic and extrinsic factors.

Indole-3-Carbinol Promotes Goblet-Cell Differentiation Regulating Wnt and Notch Signaling Pathways AhR-Dependently.

Using an in vitro model of intestinal organoids derived from intestinal crypts, we examined effects of indole-3-carbinol (I3C), a phytochemical that has anticancer and aryl hydrocarbon receptor (AhR)-activating abilities and thus is sold as a dietary supplement, on the development of intestinal organoids and investigated the underlying mechanisms. I3C inhibited the in vitro development of mouse intestinal organoids. Addition of α-naphthoflavone, an AhR antagonist or AhR siRNA transfection, suppressed I3C function, suggesting that I3C-mediated interference with organoid development is AhR-dependent. I3C increased the expression of Muc2 and lysozyme, lineage-specific genes for goblet cells and Paneth cells, respectively, but inhibits the expression of IAP, a marker gene for enterocytes. In the intestines of mice treated with I3C, the number of goblet cells was reduced, but the number of Paneth cells and the depth and length of crypts and villi were not changed. I3C increased the level of active nonphosphorylated ß-catenin, but suppressed the Notch signal. As a result, expression of Hes1, a Notch target gene and a transcriptional repressor that plays a key role in enterocyte differentiation, was reduced, whereas expression of Math1, involved in the differentiation of secretory lineages, was increased. These results provide direct evidence for the role of AhR in the regulation of the development of intestinal stem cells and indicate that such regulation is likely mediated by regulation of Wnt and Notch signals.

Kynurenine promotes the goblet cell differentiation of HT-29 colon carcinoma cells by modulating Wnt, Notch and AhR signals.

Various amino acids regulate cell growth and differentiation. In the present study, we examined the ability of HT-29 cells to differentiate into goblet cells in RPMI and DMEM which are largely different in the amounts of numerous amino acids. Most of the HT-29 cells differentiated into goblet cells downregulating the stem cell marker Lgr5 when cultured in DMEM, but remained undifferentiated in RPMI. The goblet cell differentiation in DMEM was inhibited by 1-methyl-tryptophan (1-MT), an inhibitor of indoleamine 2,3 dioxygenase-1 which is the initial enzyme in tryptophan metabolism along the kynurenine (KN) pathway, whereas tryptophan and KN induced goblet cell differentiation in RPMI. The levels of Notch1 and its activation product Notch intracytoplasmic domain in HT-29 cells were lower in DMEM than those in RPMI and were increased by 1-MT in both media. HT-29 cells grown in both media expressed ß-catenin at the same level on day 2 when goblet cell differentiation was not observed. ß-catenin expression, which was increased by 1-MT in both media, was decreased by KN. DMEM reduced Hes1 expression while enhancing Hath1 expression. Finally, aryl hydrocarbon receptor (AhR) activation moderately induced goblet cell differentiation. Our results suggest that KN promotes goblet cell differentiation by regulating Wnt, Notch, and AhR signals and expression of Hes1 and Hath1.

Acetylshikonin suppresses invasion of Porphyromonas gingivalis­infected YD10B oral cancer cells by modulating the interleukin-8/matrix metalloproteinase axis.

The development of pharmaceutical agents possessing anti­invasive and anti­metastatic abilities, as well as apoptotic activity, is important in decreasing the incidence and recurrence of oral cancer. Cancer cells are known to acquire invasiveness not only through epigenetic changes, but also from inflammatory stimuli within the tumor microenvironment. Accordingly, the identification of agents that can suppress the inflammation­promoted invasiveness of cancer cells may be important in treating cancer and improving the prognosis of patients with cancer. Acetylshikonin, a flavonoid with anti­inflammatory activity, inhibits proliferation and induces apoptosis of oral cancer cells. In the present study, the anti­invasive effect of acetylshikonin on YD10B oral cancer cells infected with Porphyromonas gingivalis, a major pathogen of chronic periodontitis, and the mechanisms involved were investigated. Firstly, we examined whether P. gingivalis infection increased the invasiveness of YD10B cells. Results suggested that YD10B oral cancer cells become more aggressive when they are infected with P. gingivalis. Secondly, acetylshikonin significantly inhibited the invasion of P. gingivalis­infected YD10B cells by suppressing IL­8 release and IL­8­dependent MMP release. These data suggest that acetylshikonin may be a useful preventive and therapeutic candidate for oral cancer that is chronically infected with periodontal pathogens.

Oral cancer cells sustainedly infected with Porphyromonas gingivalis exhibit resistance to Taxol and have higher metastatic potential.

Major obstacles to improving the prognosis of patients with oral squamous cell carcinoma (OSCC) are the acquisition of resistance to chemotherapeutic agents and development of metastases. Recently, inflammatory signals are suggested to be one of the most important factors in modulating chemoresistance and establishing metastatic lesions. In addition, epidemiological studies have demonstrated that periodontitis, the most common chronic inflammatory condition of the oral cavity, is closely associated with oral cancer. However, a correlation between chronic periodontitis and chemoresistance/metastasis has not been well established. Herein, we will present our study on whether sustained infection with Porphyromonas gingivalis, a major pathogen of chronic periodontitis, could modify the response of OSCC cells to chemotherapeutic agents and their metastatic capability in vivo. Tumor xenografts composed of P. gingivalis-infected OSCC cells demonstrated a higher resistance to Taxol through Notch1 activation, as compared with uninfected cells. Furthermore, P. gingivalis-infected OSCC cells formed more metastatic foci in the lung than uninfected cells.

Porphyromonas gingivalis increases the invasiveness of oral cancer cells by upregulating IL-8 and MMPs.

Recent studies indicate that chronic inflammation promotes the aggressiveness of cancers. However, the direct molecular mechanisms underlying a functional link between chronic periodontitis, the most common form of oral inflammatory diseases, and the malignancy of oral cancer remain unknown. To elucidate the role of chronic periodontitis in progression of oral cancer, we examined the effect of Porphyromonas gingivalis (P. gingivalis), a major pathogen that causes chronic periodontitis, on the invasiveness of oral squamous cell carcinoma (OSCC) cells, including SCC-25, OSC-20 and SAS cells. Exposures to P. gingivalis promoted the invasive ability of OSC-20 and SAS cells via the upregulation of matrix metalloproteinases (MMPs), specifically MMP-1 and MMP-2. However, P. gingivalis-infected SCC-25 cells did not exhibit changes in their invasive properties or the low expression levels of MMPs. In an effort to delineate the molecular players that control the invasiveness, we first assessed the level of interleukin-8 (IL-8), a well-known inflammatory cytokine, in P. gingivalis-infected OSCC cells. IL-8 secretion was substantially increased in the OSC-20 and SAS cells, but not in the SCC-25 cells, following P. gingivalis infection. When IL-8 was directly applied to SCC-25 cells, their invasive ability and MMP level were significantly increased. Furthermore, the downregulation of IL-8 in P. gingivalis-infected OSC-20 and SAS cells attenuated their invasive potentials and MMP levels. Taken together, our findings strongly suggest that P. gingivalis infection plays an important role in the promotion of the invasive potential of OSCC cells via the upregulation of IL-8 and MMPs.

Acetylshikonin inhibits growth of oral squamous cell carcinoma by inducing apoptosis.

OBJECTIVES: Recently, shikonin derivatives from Lithospermum erythrorhizon have been suggested as potential chemotherapeutic agents against numerous types of cancers in addition to their traditional uses, e.g., as anti-inflammatory agents. Acetylshikonin, one of shikonin derivatives, has also been reported to possess anticancer activity. However, few studies of the effectiveness of acetylshikonin against cancer cells have been conducted, and there are no studies of oral cancers. In this study, we investigated the usefulness of acetylshikonin as a treatment regimen for oral cancers by observing the growth inhibitory function of acetylshikonin and the involved mechanisms. DESIGNS: The viability, cell cycle, and ratio of apoptotic cells of oral squamous cell carcinoma (OSCC) cells were observed after treatment with acetylshikonin using MTT assay, flow cytometric analysis, and Annexin V/PI staining, respectively. In addition, molecular changes of apoptosis-related pathways and the role of reactive oxygen species (ROS) were analyzed in acetylshikonin-treated cells. RESULTS: We observed that acetylshikonin significantly suppressed the growth of OSCC cells by inducing apoptotic cell death, and acetylshikonin affected the viability of a normal keratinocyte cell line HaCaT to a lesser degree, suggesting that acetylshikonin may be a good chemotherapeutic reagent with less toxicity to normal tissues. In addition, we found that acetylshikonin-induced apoptosis of OSCC cells is mediated by ROS as well as G2 cell cycle arrest. ROS production in response to acetylshikonin treatment enhanced the phosphorylation of JNK and p38 MAPK, which are in the major pathways of apoptotic cell death mechanisms. CONCLUSIONS: In summary, our data suggest that acetylshikonin is a strong candidate for use as a selective chemotherapeutic agent for the treatment of OSCC.

Prolonged and repetitive exposure to Porphyromonas gingivalis increases aggressiveness of oral cancer cells by promoting acquisition of cancer stem cell properties.

Periodontitis is the most common chronic inflammatory condition occurring in the human oral cavity, but our knowledge on its contribution to oral cancer is rather limited. To define crosstalk between chronic periodontitis and oral cancer, we investigated whether Porphyromonas gingivalis, a major pathogen of chronic periodontitis, plays a role in oral cancer progression. To mimic chronic irritation by P. gingivalis in the oral cavity, oral squamous cell carcinoma (OSCC) cells were infected with P. gingivalis twice a week for 5 weeks. Repeated infection of oral cancer cells by P. gingivalis resulted in morphological changes of host cancer cells into an elongated shape, along with the decreased expression of epithelial cell markers, suggesting acquisition of an epithelial-to-mesenchymal transition (EMT) phenotype. The prolonged exposure to P. gingivalis also promoted migratory and invasive properties of OSCC cells and provided resistance against a chemotherapeutic agent, all of which are described as cellular characteristics undergoing EMT. Importantly, long-term infection by P. gingivalis induced an increase in the expression level of CD44 and CD133, well-known cancer stem cell markers, and promoted the tumorigenic properties of infected cancer cells compared to non-infected controls. Furthermore, increased invasiveness of P. gingivalis-infected OSCC cells was correlated with enhanced production of matrix metalloproteinase (MMP)-1 and MMP-10 that was stimulated by interleukin-8 (IL-8) release. This is the first report demonstrating that P. gingivalis can increase the aggressiveness of oral cancer cells via epithelial-mesenchymal transition-like changes and the acquisition of stemness, implicating P. gingivalis as a potential bacterial risk modifier.