The Malaysian Tualang honey (TH) is not only cytotoxic to human breast cancer cell lines but it has recently been reported to promote the anticancer activity induced by tamoxifen in MCF-7 and MDA-MB-231 cells suggesting its potential as an adjuvant for the chemotherapeutic agent. However, tamoxifen produces adverse effects that could be due to its ability to induce cellular DNA damage. Therefore, the study is undertaken to determine the possible modulation of the activity of 4-hydroxytamoxifen (OHT), an active metabolite of tamoxifen, by TH in non-cancerous epithelial cell line, MCF-10A, in comparison with MCF-7 cells.
Ganoderma neo-japonicum is an annual polypore that grows on decaying bamboo in the forests of Malaysia. The indigenous Temuan tribe uses this species as a medicinal mushroom to cure fever and epilepsy and to improve body strength. The potential use of G. neo-japonicum in genoprotection and DNA repair was established using a single-cell gel electrophoresis (comet) assay. The effects of the ethanol and hot aqueous extracts from wild and cultivated basidiocarps, solid substrate-fermented (SSF) wheat grains, and mycelia via submerged culture on H2O2-damaged murine RAW264.7 macrophages were investigated. An ethanol extract from wild basidiocarps showed the most significant protective effect on murine RAW264.7 macrophages, followed by ethanol and hot water extracts of cultivated basidiocarps, and this effect was dose dependent. However, only the ethanol extracts from SSF and submerged culture showed significant protective effects compared with the control. As for DNA repair ability, only the ethanol extract from wild and cultivated basidiocarps showed significant results when compared with the negative control. The findings suggest the potential therapeutic use of G. neo-japonicum in genome protection and as a DNA repair stimulator.
Our previous study reported that combined treatment of γ-tocotrienol with 6-gingerol showed promising anticancer effects by synergistically inhibiting proliferation of human colorectal cancer cell lines. This study aimed to identify and elucidate molecular mechanisms involved in the suppression of SW837 colorectal cancer cells modulated by combined treatment of γ-tocotrienol and 6-gingerol. Total RNA from both untreated and treated cells was prepared for transcriptome analysis using RNA sequencing techniques. We performed high-throughput sequencing at approximately 30-60 million coverage on both untreated and 6G + γT3-treated cells. The results showed that cancer-specific differential gene expression occurred and functional enrichment pathway analysis suggested that more than one pathway was modulated in 6G + γT3-treated cells. Combined treatment with 6G + γT3 augmented its chemotherapeutic effect by interfering with the cell cycle process, downregulating the Wnt signalling pathway and inducing apoptosis mainly through caspase-independent programmed cell death through mitochondrial dysfunction, activation of ER-UPR, disruption of DNA repair mechanisms and inactivation of the cell cycle process through the downregulation of main genes in proliferation such as FOXM1 and its downstream genes. The combined treatment exerted its cytotoxic effect through upregulation of genes in stress response activation and cytostatic effects demonstrated by downregulation of main regulator genes in the cell cycle. Selected genes involved in particular pathways including ATF6, DDIT3, GADD34, FOXM1, CDK1 and p21 displayed concordant patterns of gene expression between RNA sequencing and RT-qPCR. This study provides new insights into combined treatment with bioactive compounds not only in terms of its pleiotropic effects that enhance multiple pathways but also specific target genes that could be exploited for therapeutic purposes, especially in suppressing cancer cell growth.
Stilbenes are a group of chemicals characterized with the presence of 1,2-diphenylethylene. Previously, our group has demonstrated that synthesized (E)-N-(2-(3, 5-dimethoxystyryl) phenyl) furan-2-carboxamide (BK3C231) possesses potential chemopreventive activity specifically inducing NAD(P)H:quinone oxidoreductase 1 (NQO1) protein expression and activity. In this study, the cytoprotective effects of BK3C231 on cellular DNA and mitochondria were investigated in normal human colon fibroblast, CCD-18Co cells. The cells were pretreated with BK3C231 prior to exposure to the carcinogen 4-nitroquinoline 1-oxide (4NQO). BK3C231 was able to inhibit 4NQO-induced cytotoxicity. Cells treated with 4NQO alone caused high level of DNA and mitochondrial damages. However, pretreatment with BK3C231 protected against these damages by reducing DNA strand breaks and micronucleus formation as well as decreasing losses of mitochondrial membrane potential (ΔΨm) and cardiolipin. Interestingly, our study has demonstrated that nitrosative stress instead of oxidative stress was involved in 4NQO-induced DNA and mitochondrial damages. Inhibition of 4NQO-induced nitrosative stress by BK3C231 was observed through a decrease in nitric oxide (NO) level and an increase in glutathione (GSH) level. These new findings elucidate the cytoprotective potential of BK3C231 in human colon fibroblast CCD-18Co cell model which warrants further investigation into its chemopreventive role.
Molecular crosstalk between the cellular epigenome and genome converge as a synergistic driver of oncogenic transformations. Besides other pathways, epigenetic regulatory circuits exert their effect towards cancer progression through the induction of DNA repair deficiencies. We explored this mechanism using a camptothecin encapsulated in β-cyclodextrin-EDTA-Fe3O4 nanoparticles (CPT-CEF)-treated HT29 cells model. We previously demonstrated that CPT-CEF treatment of HT29 cells effectively induces apoptosis and cell cycle arrest, stalling cancer progression. A comparative transcriptome analysis of CPT-CEF-treated versus untreated HT29 cells indicated that genes controlling mismatch repair, base excision repair, and homologues recombination were downregulated in these cancer cells. Our study demonstrated that treatment with CPT-CEF alleviated this repression. We observed that CPT-CEF exerts its effect by possibly affecting the DNA repair mechanism through epigenetic modulation involving genes of HMGB1, APEX1, and POLE3. Hence, we propose that CPT-CEF could be a DNA repair modulator that harnesses the cell's epigenomic plasticity to amend DNA repair deficiencies in cancer cells.
Metformin, an AMPK activator, has been reported to improve pathological response to chemotherapy in diabetic breast cancer patients. To date, its mechanism of action in cancer, especially in cancer stem cells (CSCs) have not been fully elucidated. In this study, we demonstrated that metformin, but not other AMPK activators (e.g. AICAR and A-769662), synergizes 5-fluouracil, epirubicin, and cyclophosphamide (FEC) combination chemotherapy in non-stem breast cancer cells and breast cancer stem cells. We show that this occurs through an AMPK-dependent mechanism in parental breast cancer cell lines. In contrast, the synergistic effects of metformin and FEC occurred in an AMPK-independent mechanism in breast CSCs. Further analyses revealed that metformin accelerated glucose consumption and lactate production more severely in the breast CSCs but the production of intracellular ATP was severely hampered, leading to a severe energy crisis and impairs the ability of CSCs to repair FEC-induced DNA damage. Indeed, addition of extracellular ATP completely abrogated the synergistic effects of metformin on FEC sensitivity in breast CSCs. In conclusion, our results suggest that metformin synergizes FEC sensitivity through distinct mechanism in parental breast cancer cell lines and CSCs, thus providing further evidence for the clinical relevance of metformin for the treatment of cancers.
Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing.