Phenethyl isothiocyanate enhances TRAIL-induced apoptosis in oral cancer cells and xenografts

Cancer-preventive effect of phenethyl isothiocyanate through tumor microenvironment regulation in a colorectal cancer stem cell xenograft model

BACKGROUND

Phenethyl isothiocyanate (PEITC) is a glucosinolate derived from cruciferous vegetables and is a cancer-chemopreventive reagent. Cancer stem cells (CSCs) have roles in cancer chemoresistance, invasion, metastasis, and recurrence. Here, we investigated whether PEITC can suppress the properties of CSCs using NCCIT cells and HCT116-derived cancer stem-like cells. Furthermore, we established a CSC xenograft prevention model using nude mice.

PURPOSE

The purpose of this study was to examine the actual cancer-preventive effects of PEITC in vitro and in a xenograft prevention model.

STUDY DESIGN

We assessed the cancer-preventive effects of PEITC on CSCs using a novel xenograft prevention model.

METHODS

NCCIT cells were treated with PEITC, and the expression of pluripotent markers was confirmed by reporter assays, western blotting, and qRT-PCR. In addition, to evaluate the effects of PEITC on CSC properties, sphere cells, which exhibit CSC properties, were established from the HCT116 cells. Furthermore, to examine the inhibitory effects and the underlying mechanism following daily intake of PEITC on CSCs, we performed an animal study in a mouse xenograft model and RNA-sequencing analysis.

RESULTS

PEITC significantly reduced the CSC properties, including clonogenicity and the expression of pluripotent factors. Prior to CSC inoculation in vivo, the PEITC pre-treatment group showed a more effective reduction in the tumor growth rate and expression of CSC markers compared to the post-treatment groups. Furthermore, RNA-sequencing results showed that PEITC pre-treatment remarkably suppressed genes related to inflammatory and immune responses and chemokine-related signaling.

CONCLUSION

PEITC might contribute to the prevention or delay of colorectal cancer growth by inhibiting CSCs via the regulation of inflammatory chemokines, which can affect the tumor microenvironment. Thus, our study suggests that the daily intake of phytochemicals derived from vegetables or dietary supplements could have cancer-preventive effects through regulation of the host-tumor microenvironment.

Dietary isothiocyanates inhibit cancer progression by modulation of epigenome

Cell cycle, growth, survival and metabolism are tightly regulated together and failure in cellular regulation leads to carcinogenesis. Several signaling pathways like the PI3K, WNT, MAPK and NFKb pathway exhibit aberrations in cancer and help achieve hallmark capabilities. Clinical research and in vitro studies have highlighted the role of epigenetic alterations in cancer onset and development. Altered gene expression patterns enabled by changes in DNA methylation, histone modifications and RNA processing have proven roles in cancer hallmark acquisition. The reversible nature of epigenetic processes offers robust therapeutic targets. Dietary bioactive compounds offer a vast compendium of effective therapeutic moieties. Isothiocyanates (ITCs) sourced from cruciferous vegetables demonstrate anti-proliferative, pro-apoptotic, anti-inflammatory, anti-migratory and anti-angiogenic effect against several cancers. ITCs also modulate the redox environment, modulate signaling pathways including PI3K, MAPK, WNT, and NFkB. They also modulate the epigenetic machinery by regulating the expression and activity of DNA methyltransferases, histone modifiers and miRNA. This further enhances their transcriptional modulation of key cellular regulators. In this review, we comprehensively assess the impact of ITCs such as sulforaphane, phenethyl isothiocyanate, benzyl isothiocyanate and allyl isothiocyanate on cancer and document their effect on various molecular targets. Overall, this will facilitate consolidation of the current understanding of the anti-cancer and epigenetic modulatory potential of these compounds and recognize the gaps in literature. Further, we discuss avenues of future research to develop these compounds as potential therapeutic entities.

Sensory acceptable equivalent doses of β-phenylethyl isothiocyanate (PEITC) induce cell cycle arrest and retard the growth of p53 mutated oral cancer in vitro and in vivo

High doses of β-phenylethyl isothiocyanate (PEITC), a phytochemical in cruciferous vegetables, are not feasible for consumption due to a strong mouth-tingling effect. This study investigated the anti-cancer effect of PEITC at sensory acceptable doses. In vitro, PEITC was selectively toxic to oral cancer cells (CAL-27, FaDu, SCC4, SCC 9, SCC15, SCC25 and TU138), compared to oral keratinocytes (OKF6/TERT2 and NOK/Si). In vivo, 5 and 10 mg kg-1 PEITC, equivalent to human organoleptically acceptable doses, retarded tumor growth and prolonged the survival of mice bearing p53-mutated oral cancer cells - TU138 xenograft. Mechanistically, PEITC induced ROS accumulation, nuclear translocation of p53 and p21 and G1/S cell cycle arrest in vitro; increased p53 and 8-oxo-dG levels; and decreased Ki-67 intense/mild staining ratios without TUNEL changes in vivo. These findings suggested that the sensory acceptable doses of PEITC selectively induced ROS-mediated cell cycle arrest leading to delayed tumor progression and extended survival. PEITC could be a functional ingredient for oral cancer prevention.

Resveratrol-induced autophagy and apoptosis in cisplatin-resistant human oral cancer CAR cells: A key role of AMPK and Akt/mTOR signaling

Resveratrol is known to be an effective chemo-preventive phytochemical against multiple tumor cells. However, the increasing drug resistance avoids the cancer treatment in oral cavity cancer. In this study, we investigated the oral antitumor activity of resveratrol and its mechanism in cisplatin-resistant human oral cancer CAR cells. Our results demonstrated that resveratrol had an extremely low toxicity in normal oral cells and provoked autophagic cell death to form acidic vesicular organelles (AVOs) and autophagic vacuoles in CAR cells by acridine orange (AO) and monodansylcadaverine (MDC) staining. Either DNA fragmentation or DNA condensation occurred in resveratrol-triggered CAR cell apoptosis. These inhibitors of PI3K class III (3-MA) and AMP-activated protein kinase (AMPK) (compound c) suppressed the autophagic vesicle formation, LC3-II protein levels and autophagy induced by resveratrol. The pan-caspase inhibitor Z-VAD-FMK attenuated resveratrol-triggered cleaved caspase-9, cleaved caspase-3 and cell apoptosis. Resveratrol also enhanced phosphorylation of AMPK and regulated autophagy- and pro-apoptosis-related signals in resveratrol-treated CAR cells. Importantly, resveratrol also stimulated the autophagic mRNA gene expression, including Atg5, Atg12, Beclin-1 and LC3-II in CAR cells. Overall, our findings indicate that resveratrol is likely to induce autophagic and apoptotic death in drug-resistant oral cancer cells and might become a new approach for oral cancer treatment in the near future.