4-hydroxynonenal, a lipid peroxidation product of dietary polyunsaturated fatty acids, has anticarcinogenic properties in colon carcinoma cell lines through the inhibition of telomerase activity

The MAPK pathway signals telomerase modulation in response to isothiocyanate-induced DNA damage of human liver cancer cells

4-methylthiobutyl isothiocyanate (MTBITC), an aliphatic, sulphuric compound from Brassica vegetables, possesses in vitro and in vivo antitumor activity. Recently we demonstrated the potent growth inhibitory potential of the DNA damaging agent MTBITC in human liver cancer cells. Here we now show that MTBITC down regulates telomerase which sensitizes cells to apoptosis induction. This is mediated by MAPK activation but independent from production of reactive oxygen species (ROS). Within one hour, MTBITC induced DNA damage in cancer cells correlating to a transient increase in hTERT mRNA expression which then turned into telomerase suppression, evident at mRNA as well as enzyme activity level. To clarify the role of MAPK for telomerase regulation, liver cancer cells were pre-treated with MAPK-specific inhibitors prior to MTBITC exposure. This clearly showed that transient elevation of hTERT mRNA expression was predominantly mediated by the MAPK family member JNK. In contrast, activated ERK1/2 and P38, but not JNK, signalled to telomerase abrogation and consequent apoptosis induction. DNA damage by MTBITC was also strongly abolished by MAPK inhibition. Oxidative stress, as analysed by DCF fluorescence assay, electron spin resonance spectroscopy and formation of 4-hydroxynonenal was found as not relevant for this process. Furthermore, N-acetylcysteine pre-treatment did not impact MTBITC-induced telomerase suppression or depolarization of the mitochondrial membrane potential as marker for apoptosis. Our data therefore imply that upon DNA damage by MTBITC, MAPK are essential for telomerase regulation and consequent growth impairment in liver tumor cells and this detail probably plays an important role in understanding the potential chemotherapeutic efficacy of ITC.

Role of 4-hydroxynonenal in chemopreventive activities of sulforaphane

Chemoprevention of cancer via herbal and dietary supplements is a logical approach to combating cancer and currently it is an attractive area of research investigation. Over the years, isothiocyanates, such as sulforaphane (SFN) found in cruciferous vegetables, have been advocated as chemopreventive agents, and their efficacy has been demonstrated in cell lines and animal models. In vivo studies with SFN suggest that in addition to protecting normal healthy cells from environmental carcinogens, it also exhibits cytotoxicity and apoptotic effects against various cancer cell types. Among several mechanisms for the chemopreventive activity of SFN against chemical carcinogenesis, its effect on drug-metabolizing enzymes that cause activation/neutralization of carcinogenic metabolites is well established. Recent studies suggest that SFN exerts its selective cytotoxicity to cancer cells via reactive oxygen species-mediated generation of lipid peroxidation products, particularly 4-hydroxynonenal (HNE). Against the background of the known biochemical effects of SFN on normal and cancer cells, in this article we review the underlying molecular mechanisms responsible for the overall chemopreventive effects of SFN, focusing on the role of HNE in these mechanisms, which may also contribute to its selective cytotoxicity to cancer cells.

Role of polyunsaturated fatty acids and lipid peroxidation on colorectal cancer risk and treatments

PURPOSE OF REVIEW

The review aims at elucidating the role of lipid peroxidation of polyunsaturated fatty acids (PUFAs) in colorectal cancer (CRC) risk and treatment.

RECENT FINDINGS

CRC is one of the most overriding threats to public health. Despite a broad range of treatments, up to 50% of patients will inevitably develop incurable metastatic disease. Peroxidation of PUFAs contributes to augmentation of oxidative stress and causes in consequence inflammation, which is one of the possible carcinogenic factors of CRC. End products of PUFAs might be used as biomarkers for CRC detection and surveillance for treatment. They also have cytotoxic effect in CRC cells. Experimental results suggest that ω-3 PUFAs could increase the efficacy of radiotherapy and chemotherapy of CRC.

SUMMARY

Lipid peroxidation, one factor of oxidative stress, might play a paramount role not only in carcinogenesis but also in potential therapeutic strategy on CRC. End products of lipid peroxidation, such as malondialdehyde, 4-hydroxy-2-nonenal, and isoprostanes, could be used as biomarkers for cancer detection, surveillance of treatment outcome and prognostic index for CRC patients. Furthermore, malondialdehyde and 4-hydroxy-2-nonenal have cytotoxic effect not only in normal cells but also in CRC cancer cells, which implies the potential role of PUFAs in CRC treatment.

Damage of DNA and proteins by major lipid peroxidation products in genome stability

Oxidative stress and lipid peroxidation (LPO) accompanying infections and chronic inflammation may induce several human cancers. LPO products are characterized by carbohydrate chains of different length, reactive aldehyde groups and double bonds, which make these molecules reactive to nucleic acids, proteins and cellular thiols. LPO-derived adducts to DNA bases form etheno-type and propano-type exocyclic rings, which have profound mutagenic potential, and are elevated in several cancer-prone diseases. Adducts of long chain LPO products to DNA bases inhibit transcription. Elimination from DNA of LPO-induced lesions is executed by several repair systems: base excision repair (BER), direct reversal by AlkB family proteins, nucleotide excision repair (NER) and recombination. Modifications of proteins with LPO products may regulate cellular processes like apoptosis, cell signalling and senescence. This review summarizes consequences of LPO products' presence in cell, particularly 4-hydroxy-2-nonenal, in terms of genomic stability.

Novel aspect of chemophototherapy in treatment of cancer

The present review deals with the genetic implications of reactive oxygen species (ROS) to enhance horizons of chemophototherapy toward novel approaches for the treatment of various cancers. ROS are species of oxygen which are in a more reactive state than molecular oxygen. ROS play essential roles in vivo such as redox regulation, gene expression, immune response and many other cellular events. ROS generated by anticancer drugs during chemophototherapy may be associated with the activation of signal molecules like PKC, transcription factor NF-kappaB as well as destabilization of mitochondrial membrane inducing the release of apoptosis inducing agents like cytochrome c, resulting in toxicity to cancer cells. Thus, we suggest that anticancer drugs on exposure to light may generate oxidative stress following Fenton-like reaction generating hydroxyl radical. This may get on specific cell cycle receptors which may lead to cell cycle arrest and subsequently cytotoxic death of cancer cells.

Induction of cell cycle arrest and DNA damage by the HDAC inhibitor panobinostat (LBH589) and the lipid peroxidation end product 4-hydroxynonenal in prostate cancer cells

Histone deacetylase inhibitors (HDACIs) are promising antineoplastic agents for the treatment of cancer. Here we report that the lipid peroxidation end product 4-hydroxynonenal (HNE) significantly potentiates the anti-tumor effects of the HDAC inhibitor panobinostat (LBH589) in the PC3 prostate cancer cell model. Panobinostat and HNE inhibited proliferation of PC3 cells and the combination of the two agents resulted in a significant combined effect. Cell cycle analysis revealed that both single agents and, to a greater extent, their combined treatment induced G2/M arrest, but cell death occurred in the combined treatment only. Furthermore, HNE and, to a greater extent, the combined treatment induced dephosphorylation of Cdc2 leading to progression into mitosis as confirmed by α-tubulin/DAPI staining and phospho-histone H3 (Ser10) analysis. To evaluate possible induction of DNA damage we utilized the marker phosphorylated histone H2A.X. Results showed that the combination of panobinostat and HNE induced significant DNA damage concomitant with the mitotic arrest. Then, by using androgen receptor (AR)-expressing PC3 cells we observed that the responsiveness to HNE and panobinostat was independent of the expression of functional AR. Taken together, our data suggest that HNE potentiates the antitumoral effect of the HDACI panobinostat in prostate cancer cells.

Hepatotoxicity and nephrotoxicity produced by 4-hydroxy-2-nonenal (4-HNE) following 4-week oral administration to Sprague-Dawley rats

4-Hydroxy-2-nonenal (4-HNE) is a major end product of lipid peroxidation of membrane n-6 polyunsaturated fatty acids, which are found in food products. In order to examine the toxicity attributed to 4-HNE, a subacute toxicity study was conducted in Sprague-Dawley (SD) rats. For this study, 4 groups of 10 male and 10 female rats were administered by gavage either 0 (control), 0.5, 2.5, or 12.5 mg 4-HNE/kg body weight/d for 28 d, and then sacrificed for blood and tissue sampling. No significant changes in body weight or clinical signs were observed, but biochemical analysis showed significant alterations in hepatotoxicity biomarkers, such as levels of serum albumin and total bilirubin, and aspartate aminotransferase (AST) activity, and in nephrotoxicity biomarkers, such as levels of blood urea nitrogen (BUN) and creatinine and activity of alkaline phosphatase (ALP), and urinary creatinine and protein levels at 0.5 mg/kg/d. In addition, significant increases in kidney and brain weights and a significant decrease in small intestine weight were noted at 12.5 mg/kg/d. Histologic examinations of kidneys showed hyaline droplets or accumulation of hyaline bodies in renal tubules and degeneration of tubular epithelium cells. These results demonstrate that oral daily exposure to 4-HNE for 28 d produced hepatotoxicity and nephrotoxicity. The no-observed-adverse-effect level (NOAEL) for 4-HNE was calculated to be <0.5 mg 4-HNE/kg/d.

The "two-faced" effects of reactive oxygen species and the lipid peroxidation product 4-hydroxynonenal in the hallmarks of cancer

Reacytive Oxygen Species (ROS) have long been considered to be involved in the initiation, progression and metastasis of cancer. However, accumulating evidence points to the benefical role of ROS. Moreover, ROS production, leading to apoptosis, is the mechanism by which many chemotherapeutic agents can act. Beside direct actions, ROS elicit lipid peroxidation, leading to the production of 4-hydroxynoneal (HNE). Interestingly, HNE also seems to have a dual behaviour with respect to cancer. In this review we present recent literature data which outline the "two-faced" character of oxidative stress and lipid peroxidation in carcinogenesis and in the hallmarks of cancer.