Differential Pharmacological Activities of Oxygen Numbers on the Sulfoxide Moiety of Wasabi Compound 6-(Methylsulfinyl) Hexyl Isothiocyanate in Human Oral Cancer Cells

Advances in Small Molecular Agents against Oral Cancer

Oral cancer is a common malignancy with a high mortality rate. Although surgery is the best treatment option for patients with cancer, this approach is ineffective for advanced metastases. Molecular agents are irreplaceable in preventing and treating distant metastases. This review aims to summarise the molecular agents used for the treatment of oral cancer in the last decade and describe their sources and curative effects. These agents are classified into phenols, isothiocyanates, anthraquinones, statins, flavonoids, terpenoids, and steroids. The mechanisms of action of these agents include regulating the expression of cell signalling pathways and related proteases to affect the proliferation, autophagy, migration, apoptosis, and other biological aspects of oral cancer cells. This paper may serve as a reference for subsequent studies on the treatment of oral cancer.

Bioactive phytocompounds for oral cancer prevention and treatment: A comprehensive and critical evaluation

The high incidence of oral cancer combined with excessive treatment cost underscores the need for novel oral cancer preventive and therapeutic options. The value of natural agents, including plant secondary metabolites (phytochemicals), in preventing carcinogenesis and representing expansive source of anticancer drugs have been established. While fragmentary research data are available on antioral cancer effects of phytochemicals, a comprehensive and critical evaluation of the potential of these agents for the prevention and intervention of human oral malignancies has not been conducted according to our knowledge. This study presents a complete and critical analysis of current preclinical and clinical results on the prevention and treatment of oral cancer using phytochemicals. Our in-depth analysis highlights anticancer effects of various phytochemicals, such as phenolics, terpenoids, alkaloids, and sulfur-containing compounds, against numerous oral cancer cells and/or in vivo oral cancer models by antiproliferative, proapoptotic, cell cycle-regulatory, antiinvasive, antiangiogenic, and antimetastatic effects. Bioactive phytochemicals exert their antineoplastic effects by modulating various signaling pathways, specifically involving the epidermal growth factor receptor, cytokine receptors, toll-like receptors, and tumor necrosis factor receptor and consequently alter the expression of downstream genes and proteins. Interestingly, phytochemicals demonstrate encouraging effects in clinical trials, such as reduction of oral lesion size, cell growth, pain score, and development of new lesions. While most phytochemicals displayed minimal toxicity, concerns with bioavailability may limit their clinical application. Future directions for research include more in-depth mechanistic in vivo studies, administration of phytochemicals using novel formulations, investigation of phytocompounds as adjuvants to conventional treatment, and randomized clinical trials.

Anti-Cancer Effects of Oxygen-Atom-Modified Derivatives of Wasabi Components on Human Leukemia Cells

1-Isothiocyanato-6-(methylsulfinyl)-hexanate (6-MITC) is a natural compound found in Wasabia japonica. The synthetic derivatives 1-Isothiocyanato-6-(methylsulfenyl)-hexane (I7447) and 1-Isothiocyanato-6-(methylsulfonyl)-hexane (I7557) were obtained from 6-MITC by deleting and adding an oxygen atom to the sulfone group, respectively. We previously demonstrated that extensive mitotic arrest, spindle multipolarity, and cytoplasmic vacuole accumulation were induced by 6-MITC and inhibited the viability of human chronic myelogenous leukemia K562 cells. In this study, we examined the anti-cancer effects of 6-MITC derivatives on human chronic myelogenous leukemia (CML) cells. Autophagy was identified as the formation of autophagosomes with double-layered membranes using transmission electron microscopy. Cell cycle and differentiation were analyzed using flow cytometry. Apoptosis was detected by annexin V staining. After treatment with I7447 and I7557, the G2/M phase of cell cycle arrest was revealed. Cell death can be induced by a distinct mechanism (the simultaneous occurrence of autophagy and aberrant mitosis). The expression levels of acridine orange were significantly affected by lysosomal inhibitors. The natural wasabi component, 6-MITC, and its synthetic derivatives have similar effects on human chronic myelogenous leukemia cells and may be developed as novel therapeutic agents against leukemia.

Anti-tumor effect of Wasabi component, 6-(methylsulfinyl) hexyl isothiocyanate, against endometrial carcinoma cells

PURPOSE

Wasabi is a traditional plant seasoning with an anti-septic function. Recent studies revealed several functions of Wasabi, such as anti-inflammation; however, the anti-tumor effect against endometrial carcinoma (EMC) cells has not been examined. In the present study, we investigated the anti-tumor effect of 6-(methylsulfinyl) hexyl isothiocyanate (6-MITC), a major chemical compound of Wasabi, against various EMC cell lines in vitro and in vivo.

METHODS

The effect of 6-MITC on cell viability was measured by the WST-1 assay in EMC and HUVEC cells. The impact of 6-MITC oral administration in nude mice was measured to assess the growth of the EMC xenograft and natural killer (NK) cell activity in the spleen.

RESULTS

The addition of 6-MITC suppressed the proliferation of EMC cells (Ishikawa, HEC265, HEC108, KLE, and HEC1B) dose-dependently, but not HUVEC cells. 6-MITC (5 µM) enhanced the cisplatin sensitivity of EMC cells. 6-MITC induced apoptosis in a dose-dependent fashion in EMC cells other than HEC1B cells and was associated with increased expression of cleaved-caspase3 and decreased expression of BCL2. Oral administration of 6-MITC (2 and 4 µmol/kg) to Ishikawa and HEC1B xenografting mice resulted in a reduced tumor volume compared with the control (P < 0.05, 4 µmol/kg). Immunohistochemical staining of resected tumors revealed increased expression of Ki-67 and reduced cleaved-caspase3. Furthermore, 6-MITC treatment enhanced NK cell activity, especially when administered before tumor xenografting.

CONCLUSION

These results indicate that 6-MITC has a marked anti-tumor effect against EMC cells and a novel effect to enhance NK cell activity. These effects suggest the therapeutic potential of 6-MITC.

6-(Methylsulfonyl) Hexyl Isothiocyanate: A Chemopreventive Agent Inducing Autophagy in Leukemia Cell Lines

Autophagy is a fundamental catabolic process of cellular survival. The role of autophagy in cancer is highly complex: in the early stages of neoplastic transformation, it can act as a tumor suppressor avoiding the accumulation of proteins, damaged organelles, and reactive oxygen species (ROS), while during the advanced stages of cancer, autophagy is exploited by cancer cells to survive under starvation. 6-(Methylsulfonyl) hexyl isothiocyanate (6-MITC) is the most interesting compound in the Wasabia Japonica rizhome. Recently, we proved its ability to induce cytotoxic, cytostatic, and cell differentiation effects on leukemic cell lines and its antimutagenic activity on TK6 cells. In the current study, to further define its chemopreventive profile, Jurkat and HL-60 cells were treated with 6-MITC for 24 h. The modulation of the autophagic process and the involvement of ROS levels as a possible trigger mechanisms were analyzed by flow cytometry. We found that 6-MITC induced autophagy in Jurkat and HL-60 cells at the highest concentration tested and increased ROS intracellular levels in a dose-dependent manner. Our results implement available data to support 6-MITC as an attractive potential chemopreventive agent.

Wasabi Component 6-(Methylsulfinyl)hexly Isothiocyanate and Derivatives Improve the Survival of Skin Allografts

We tested the effect of 6-(Methylsulfinyl)hexyl Isothiocyanate (6-MITC) and derivatives (I7447 and I7557) on the differentiation and maturation of human myeloid dendritic cells (DCs) in vitro, and skin transplantation in vivo. Triggering of CD14⁺ myeloid monocyte development toward myeloid DCs with and without 6-MITC and derivatives to examine the morphology, viability, surface marker expression, and cytokine production. Stimulatory activity on allogeneic naive T cells was measured by proliferation and interferon-γ production. The skin allograft survival area model was used to translate the 6-MITC and derivatives’ antirejection effect. All of the compounds had no significant effects on DC viability and reduced the formation of dendrites at concentrations higher than 10 μM. At this concentration, 6-MITC and I7557, but not I7447, inhibited the expression of CD1a and CD83. Both 6-MITC and I7557 exhibited T-cells and interferon-γ augmentation at lower concentrations and suppression at higher concentration. The 6-MITC and I7557 prolonged skin graft survival. Both the 6-MITC and I7557 treatment resulted in the accumulation of regulatory T cells in recipient rat spleens. No toxicity was evident in 6-MITC and I7557 treatment. The 6-MITC and I7557 induced human DC differentiation toward a tolerogenic phenotype and prolonged rat skin allograft survival. These compounds may be effective as immunosuppressants against transplant rejection.

Anticancer and Anti-Neuroinflammatory Constituents Isolated from the Roots of Wasabia japonica

Wasabi (Wasabia japonica (Miq.) Matsum.) is a pungent spice commonly consumed with sushi and sashimi. From the roots of this plant, a new 2-butenolide derivative (1) and 17 previously reported compounds (2–18) were isolated and structurally characterized. Their chemical structures were characterized based on the conventional NMR (¹H and ¹³C, COSY, HSQC, and HMBC) and HRESIMS data analysis. All of these phytochemicals (1–18) were evaluated for their antiproliferative effects on the four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and MKN-1), for their inhibitory activity on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 microglia cells, and for their nerve growth factor (NGF)-releasing effect from C6 glioma cells. Among the isolated compounds, compound 15 showed powerful antiproliferative activities against A549 and SK-MEL-2 cell lines with IC₅₀ values of 2.10 and 9.08 μM, respectively. Moreover, the new compound 1 exhibited moderate NO inhibition activity with IC₅₀ value of 45.3 μM.

Wasabi Compound 6-(Methylsulfinyl) Hexyl Isothiocyanate Induces Cell Death with Coexisting Mitotic Arrest and Autophagy in Human Chronic Myelogenous Leukemia K562 Cells

A natural compound from Wasabia japonica, 6-(methylsulfinyl) hexyl isothiocyanate (6-MITC) was investigated for its anti-leukemia activity and mechanism of action. It was found that 6-MITC inhibited the viability of human chronic myelogenous leukemia K562 cells along with extensive mitotic arrest, spindle multipolarity, and cytoplasmic vacuole accumulation. The evidence of autophagy included the validation of autophagosomes with double-layered membranes under transmission electron microscopy, LC3I/II conversion, and the induction of G2/M phase arrest observed with acridine orange staining of treated cells, as well as the elevation of phosphorylated-histone H3 expression at the M phase. With regard to the expression of proteins related to mitosis, the down regulation of p-CHK1, p-CHK2, p-cdc25c, and p-cdc2, as well as the upregulation of cyclin B1, p-cdc20, cdc23, BubR1, Mad2, and p-plk-1 was observed. The knockdown of cdc20 was unable to block the effect of 6-MITC. The differentiation of k562 cells into monocytes, granulocytes, and megakaryocytes was not affected by 6-MITC. The 6-MITC-induced unique mode of cell death through the concurrent induction of mitosis and autophagy may have therapeutic potential. Further studies are required to elucidate the pathways associated with the counteracting occurrence of mitosis and autophagy.