The sensitizing effect of chromone-derived compounds on UVC-induced proliferation inhibition has not been comprehensively investigated so far. The subject of this study was to examine the proliferation change of oral cancer cells while using the combined treatment of UVC (254 nm) with our previously developed sulfonyl chromen-4-ones (CHW09), namely UVC/CHW09. Cell viability, apoptosis, oxidative stress, and DNA damage for the individual and combined treatments for UVC and/or CHW09 were examined in oral cancer Ca9-22 cells. In 24 h MTS assay, UVC (30 J/m2; UVC30), or CHW09 (25 and 50 µg/mL; namely, CHW09-25 and CHW09-50) show 54%, 59%, and 45% viability. The combined treatment (UVC30/CHW09-25 and UVC30/CHW09-50) show lower cell viability (45% and 35%). Mechanistically, UVC/CHW09 induced higher apoptosis than individual treatments and untreated control, which were supported by the evidence of flow cytometry for subG1, annexin V/7-aminoactinomycin D, pancaspase and caspases 3/7 activity, and western blotting for cleaved poly(ADP-ribose) polymerase. Moreover, this cleaved PARP expression was downregulated by pancaspase inhibitor Z-VAD-FMK. UVC/CHW09 showed higher oxidative stress than individual treatments and untreated control in terms of flow cytometry for reactive oxygen species, mitochondrial membrane potential, and mitochondrial mass. Furthermore, UVC/CHW09 showed higher DNA damage than individual treatments and untreated control in terms of flow cytometry for H2A histone family member X and 8-oxo-2’-deoxyguanosine. In conclusion, combined treatment UVC/CHW09 suppresses proliferation, and promotes apoptosis, oxidative stress, and DNA damage against oral cancer cells, providing a novel application of sulfonyl chromen-4-ones in order to sensitize UVC induced proliferation inhibition for oral cancer therapy.

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Nepenthes plants are regarded as a kind of Traditional Chinese Medicine for several diseases but its anticancer activity remain unclear. The subject of this study is to evaluate the antiproliferation effects on oral cancer cells by Nepenthes plants using ethyl acetate extract of Nepenthes adrianii x clipeata (EANA). Cell viability was detected using MTS assay. Its detailed mechanisms including cell cycle, apoptosis, oxidative stress, and DNA damage were explored by flow cytometry or western blotting. For 24 hours EANA treatment, five kinds of oral cancer cells (CAL 27, Ca9-22, OECM-1, HSC-3, and SCC9) show IC 50 values of cell viability ranging from 8 to 17 μg/mL but the viability of normal oral cells (HGF-1) remains over 80%. Subsequently, CAL 27 and Ca9-22 cells with high sensitivity to EANA were chosen to investigate the detailed mechanism. EANA displays the time course and concentration effects for inducing apoptosis based on flow cytometry (subG1 and annexin V analyses) and western blotting [cleaved poly (ADP-ribose) polymerase (c-PARP)]. Oxidative stress and DNA damage were induced by EANA treatments in oral cancer cells through reactive oxygen species (ROS),

Several functionalized chromones, the key components of naturally occurring oxygenated heterocycles, have anticancer effects but their sulfone compounds are rarely investigated. In this study, we installed a sulfonyl substituent to chromen-4-one skeleton and synthesized CHW09 to evaluate its antioral cancer effect in terms of cell viability, cell cycle, apoptosis, oxidative stress, and DNA damage. In cell viability assay, CHW09 preferentially kills two oral cancer cells (Ca9-22 and CAL 27), less affecting normal oral cells (HGF-1). Although CHW09 does not change the cell cycle distribution significantly, CHW09 induces apoptosis validated by flow cytometry for annexin V and by western blotting for cleaved poly(ADP-ribose) polymerase (PARP), and caspases 3/8/9. These apoptosis signaling expressions are partly decreased by apoptosis inhibitor (Z-VAD-FMK) or free radical scavenger (N-acetylcysteine). Furthermore, CHW09 induces oxidative stress validated by flow cytometry for the generations of reactive oxygen species (ROS) and mitochondrial superoxide (MitoSOX), and the suppression of mitochondrial membrane potential (MMP). CHW09 also induces DNA damage validated by flow cytometry for the increases of DNA double strand break marker γH2AX and oxidative DNA damage marker 8-oxo-2'-deoxyguanosine (8-oxodG). Therefore, our newly synthesized CHW09 induces apoptosis, oxidative stress, and DNA damage, which may lead to preferential killing of oral cancer cells compared with normal oral cells.

Marine natural products are abundant resources for antioxidants, but the antioxidant property of the soft corals-derived sinularin and dihydrosinularin were unknown. This study aimed to assess antioxidant potential and antiproliferation effects of above compounds on cancer cells, and to investigate the possible relationships between them. Results show that sinularin and dihydrosinularin promptly reacted with 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl (•OH), demonstrating a general radical scavenger activity. Sinularin and dihydrosinularin also show an induction for Fe+3-reduction and Fe+2-chelating capacity which both strengthen their antioxidant activities. Importantly, sinularin shows higher antioxidant properties than dihydrosinularin. Moreover, 24 h ATP assays show that sinularin leads to higher antiproliferation of breast, lung, and liver cancer cells than dihydrosinularin. Therefore, the differential antioxidant properties of sinularin and dihydrosinularin may contribute to their differential anti-proliferation of different cancer cells.

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Several kinds of solvents have been applied to Nepenthes extractions exhibiting antioxidant and anticancer effects. However, they were rarely investigated for Nepenthes ethyl acetate extract (EANT), especially leukemia cells. The purpose of the present study was to evaluate the antioxidant properties and explore the antiproliferation impact and mechanism of EANT in leukemia cells. Five standard assays demonstrated that EANT exhibits antioxidant capability. In the cell line model, EANT dose-responsively inhibited cell viabilities of three leukemia cell lines (HL-60, K-562, and MOLT-4) based on 24 h MTS assays, which were reverted by pretreating oxidative stress and apoptosis inhibitors (N-acetylcysteine and Z-VAD-FMK). Due to similar sensitivities among the three cell lines, leukemia HL-60 cells were chosen for exploring antiproliferation mechanisms. EANT caused subG1 and G1 cumulations, triggered annexin V-detected apoptosis, activated apoptotic caspase 3/7 activity, and induced poly ADP-ribose polymerase expression. Moreover, reactive oxygen species, mitochondrial superoxide, and mitochondrial membrane depolarization were generated by EANT, which was reverted by N-acetylcysteine. The antioxidant response to oxidative stress showed that EANT upregulated mRNA expressions for nuclear factor erythroid 2-like 2 (NFE2L2), catalase (CAT), thioredoxin (TXN), heme oxygenase 1 (HMOX1), and NAD(P)H quinone dehydrogenase 1 (NQO1) genes. Moreover, these oxidative stresses led to DNA damage (γH2AX and 8-hydroxy-2-deoxyguanosine) and were alleviated by N-acetylcysteine. Taken together, EANT demonstrated oxidative stress-dependent anti-leukemia ability to HL-60 cells associated with apoptosis and DNA damage.

Dihydrosinularin (DHS) is an analog of soft coral-derived sinularin; however, the anticancer effects and mechanisms of DHS have seldom been reported. This investigation examined the antiproliferation ability and mechanisms of DHS on oral cancer cells. In a cell viability assay, DHS showed growth inhibition against several types of oral cancer cell lines (Ca9-22, SCC-9, OECM-1, CAL 27, OC-2, and HSC-3) with no cytotoxic side effects on non-malignant oral cells (HGF-1). Ca9-22 and SCC-9 cell lines showing high susceptibility to DHS were selected to explore the antiproliferation mechanisms of DHS. DHS also causes apoptosis as detected by annexin V, pancaspase, and caspase 3 activation. DHS induces oxidative stress, leading to the generation of reactive oxygen species (ROS)/mitochondrial superoxide (MitoSOX) and mitochondrial membrane potential (MitoMP) depletion. DHS also induced DNA damage by probing γH2AX phosphorylation. Pretreatment with the ROS scavenger N-acetylcysteine (NAC) can partly counter these DHS-induced changes. We report that the marine natural product DHS can inhibit the cell growth of oral cancer cells. Exploring the mechanisms of this cancer cell growth inhibition, we demonstrate the prominent role DHS plays in oxidative stress.