Mitochondrial reactive oxygen species accelerate gastric cancer cell invasion

Mitochondria: a new intervention target for tumor invasion and metastasis

Mitochondria, responsible for cellular energy synthesis and signal transduction, intricately regulate diverse metabolic processes, mediating fundamental biological phenomena such as cell growth, aging, and apoptosis. Tumor invasion and metastasis, key characteristics of malignancies, significantly impact patient prognosis. Tumor cells frequently exhibit metabolic abnormalities in mitochondria, including alterations in metabolic dynamics and changes in the expression of relevant metabolic genes and associated signal transduction pathways. Recent investigations unveil further insights into mitochondrial metabolic abnormalities, revealing their active involvement in tumor cell proliferation, resistance to chemotherapy, and a crucial role in tumor cell invasion and metastasis. This paper comprehensively outlines the latest research advancements in mitochondrial structure and metabolic function. Emphasis is placed on summarizing the role of mitochondrial metabolic abnormalities in tumor invasion and metastasis, including alterations in the mitochondrial genome (mutations), activation of mitochondrial-to-nuclear signaling, and dynamics within the mitochondria, all intricately linked to the processes of tumor invasion and metastasis. In conclusion, the paper discusses unresolved scientific questions in this field, aiming to provide a theoretical foundation and novel perspectives for developing innovative strategies targeting tumor invasion and metastasis based on mitochondrial biology.

Reactive oxygen species induced by indomethacin enhance accumulation of heme carrier protein 1 and hematoporphyrin accumulation in vitro and in vivo in a brain tumor model

Photodynamic therapy (PDT) is useful for various cancers such as high-grade glioma and cancers of other organs. However, the mechanism of tumor-specific accumulation of porphyrin is not clear. The authors previously reported that heme carrier protein 1 (HCP1) contributes to the transport of porphyrins; specifically, we showed that the production of cancer-specific reactive oxygen species from mitochondria (mitROS) leads in turn to enhanced HCP1 expression. Indomethacin (IND), a non-steroidal anti-inflammatory drug, increases ROS production by affecting mitochondrial electron transfer system. In the present work, the authors investigated the effect of pretreatment with IND on cancer-specific porphyrin accumulation, using both a glioma cell line and a rat brain tumor model. This work demonstrated that exposure of a rat glioma cell to IND results in increased generation of cancer-specific mitROS and accumulation of HCP1 expression and porphyrin concentration. Additionally, systemic dosing of a brain tumor animal model with IND resulted in elevated cellular accumulation of porphyrin in tumor cell. This is an effect not seen with normal brain tissue. Thus, the administration of IND increases intracellular porphyrin concentrations in tumor cell without exerting harmful effects on normal brain tissue, and increased porphyrin concentration in tumor cell may lead to improved PDT effect.

Enhanced Inhibition of Cancer Cell Migration by a Planar Catechin Analog

Cancer cell migration is related to malignancy and patient prognosis. We previously reported that intracellular reactive oxygen species (ROS) promoted cancer cellular migration and invasion and that an antioxidant enzyme could help to attenuate the malignancy. Catechin is known as an antioxidant, and we have developed a catechin analog, planar catechin, which showed an antioxidant activity significantly stronger than that of the parent (+)-catechin. In this study, we examined the effects of the planar catechin on the migration of gastric normal and cancer cells. A scratched assay showed that the planar catechin suppressed the cellular migration rates in both normal and cancer cells, while the prevention levels in cancer cells were remarkable compared to the normal cells. These results suggest that the planar catechin with the enhanced antioxidant activity effectively scavenged the ROS overexpressed in the cancer cells and inhibited cancer cellular activities, including migration.

Depletion of Labile Iron Induces Replication Stress and Enhances Responses to Chemoradiation in Non-Small-Cell Lung Cancer

The intracellular redox-active labile iron pool (LIP) is weakly chelated and available for integration into the iron metalloproteins that are involved in diverse cellular processes, including cancer cell-specific metabolic oxidative stress. Abnormal iron metabolism and elevated LIP levels are linked to the poor survival of lung cancer patients, yet the underlying mechanisms remain unclear. Depletion of the LIP in non-small-cell lung cancer cell lines using the doxycycline-inducible overexpression of the ferritin heavy chain (Ft-H) (H1299 and H292), or treatment with deferoxamine (DFO) (H1299 and A549), inhibited cell growth and decreased clonogenic survival. The Ft-H overexpression-induced inhibition of H1299 and H292 cell growth was also accompanied by a significant delay in transit through the S-phase. In addition, both Ft-H overexpression and DFO in H1299 resulted in increased single- and double-strand DNA breaks, supporting the involvement of replication stress in the response to LIP depletion. The Ft-H and DFO treatment also sensitized H1299 to VE-821, an inhibitor of ataxia telangiectasis and Rad2-related (ATR) kinase, highlighting the potential of LIP depletion, combined with DNA damage response modifiers, to alter lung cancer cell responses. In contrast, only DFO treatment effectively reduced the LIP, clonogenic survival, cell growth, and sensitivity to VE-821 in A549 non-small-cell lung cancer cells. Importantly, the Ft-H and DFO sensitized both H1299 and A549 to chemoradiation in vitro, and Ft-H overexpression increased the efficacy of chemoradiation in vivo in H1299. These results support the hypothesis that the depletion of the LIP can induce genomic instability, cell death, and potentiate therapeutic responses to chemoradiation in NSCLC.

Aptamers as Smart Ligands for Targeted Drug Delivery in Cancer Therapy

Undesirable side effects and multidrug tolerance are the main holdbacks to the treatment of cancer in conventional chemotherapy. Fortunately, targeted drug delivery can improve the enrichment of drugs at the target site and reduce toxicity to normal tissues and cells. A targeted drug delivery system is usually composed of a nanocarrier and a targeting component. The targeting component is called a "ligand". Aptamers have high target affinity and specificity, which are identified as attractive and promising ligands. Therefore, aptamers have potential application in the development of smart targeting systems. For instance, aptamers are able to efficiently recognize tumor markers such as nucleolin, mucin, and epidermal growth factor receptor (EGFR). Besides, aptamers can also identify glycoproteins on the surface of tumor cells. Thus, the aptamer-mediated targeted drug delivery system has received extensive attention in the application of cancer therapy. This article reviews the application of aptamers as smart ligands for targeted drug delivery in cancer therapy. Special interest is focused on aptamers as smart ligands, aptamer-conjugated nanocarriers, aptamer targeting strategy for tumor microenvironment (TME), and aptamers that are specified to crucial cancer biomarkers for targeted drug delivery.

Acetic acid enhances the effect of photodynamic therapy in gastric cancer cells via the production of reactive oxygen species

Acetic acid is a major component of vinegar and is reported to have beneficial health effects. Notably, it causes oxidative stress and enhances the production of reactive oxygen species (ROS) in gastric cancer cells. ROS play important roles in cellular signal transduction, resulting in the regulation of protein expression and apoptosis. We previously reported that ROS upregulate heme carrier protein 1 (HCP1). Moreover, ROS increase the cellular uptake of porphyrins, which are precursors of heme and substrates for uptake by HCP1. Therefore, we hypothesized that photodynamic therapy (PDT) for cancer treatment using laser irradiation and photosensitizers, such as porphyrin, is enhanced via ROS produced by acetic acid. Herein, we used the rat gastric mucosal cells, RGM1, its cancer-like mutated cells, RGK1, and a manganese superoxide dismutase (MnSOD)-overexpressing RGK cell line, RGK-MnSOD. We confirmed that cancer-specific cellular uptake of porphyrin is increased upon acetic acid treatment and enhances the PDT cytotoxicity in RGK-1, not in RGM-1 and RGK-MnSOD. We believe that this occurs because of the overproduction of ROS and subsequent upregulation of HCP1 in cancerous cells. In conclusion, acetic acid can elevate the effect of PDT by inducing cancer-specific HCP1 expression via ROS production.

Near-Infrared Light Irradiation of Porphyrin-Modified Gold Nanoparticles Promotes Cancer-Cell-Specific Cytotoxicity

The use of nanoparticles has been investigated as a new cancer treatment. These can induce specific cytotoxicity in cancer cells. In particular, Au nanoparticles (AuNPs) have unique characteristics. The maximum absorption spectrum of AuNPs can be adjusted to modify their size or shape to absorb near-infrared light that can penetrate into tissue without photodamage. Thus, the combination of AuNPs and near-infrared light can be used to treat cancer in deep-seated organs. To obtain effective cancer-specific accumulation of AuNPs, we focused on porphyrin and synthesized a porphyrin-attached Au compound: Au-HpD. In this study, we investigated whether Au-HpD possesses cancer-specific accumulation and cytotoxicity. Intracellular Au-HpD accumulation was higher in cancer cells than in normal cells. In order to analyze the cytotoxicity induced by Au-HpD, cancer cells and normal cells were co-cultured in the presence of Au-HpD; then, they were subjected to 870 nm laser irradiation. We observed that, after laser irradiation, cancer cells showed significant morphological changes, such as chromatin condensation and nuclear fragmentation indicative of cell apoptosis. This strong effect was not observed when normal cells were irradiated. Moreover, cancer cells underwent cell apoptosis with combination therapy.

Targeting mitochondria as a therapeutic anti-gastric cancer approach

Gastric cancer is regarded as the fifth most common cancer globally but the third most common cancer death. Although systemic chemotherapy is the primary treatment for advanced gastric cancer patients, the outcome of chemotherapy is unsatisfactory. Novel therapeutic strategies and potential alternative treatments are therefore needed to overcome the impact of this disease. At a cellular level, mitochondria play an important role in cell survival and apoptosis. A growing body of studies have shown that mitochondria play a central role in the regulation of cellular function, metabolism, and cell death during carcinogenesis. Interestingly, the impact of mitochondrial dynamics, including fission/fusion and mitophagy, on carcinogenesis and cancer progression has also been reported, suggesting the potential targeting of mitochondrial dynamics for the treatment of cancer. This review not only comprehensively summarizes the homeostasis of gastric cancer cells, but the potential therapeutic interventions for the targeting of mitochondria for gastric cancer therapy are also highlighted and discussed.

Pharmacological Effects of Grifolin: Focusing on Anticancer Mechanisms

Grifolin is a volatile compound contained in essential oils of several medicinal plants. Several studies show that this substance has been the subject of numerous pharmacological investigations, which have yielded interesting results. Grifolin demonstrated beneficial effects for health via its multiple pharmacological activities. It has anti-microbial properties against bacteria, fungi, and parasites. In addition, grifolin exhibited remarkable anti-cancer effects on different human cancer cells. The anticancer action of this molecule is related to its ability to act at cellular and molecular levels on different checkpoints controlling the signaling pathways of human cancer cell lines. Grifolin can induce apoptosis, cell cycle arrest, autophagy, and senescence in these cells. Despite its major pharmacological properties, grifolin has only been investigated in vitro and in vivo. Therefore, further investigations concerning pharmacodynamic and pharmacokinetic tests are required for any possible pharmaceutical application of this substance. Moreover, toxicological tests and other investigations involving humans as a study model are required to validate the safety and clinical applications of grifolin.

Reactive oxygen species: Role in carcinogenesis, cancer cell signaling and tumor progression

Cancer is one of the major causes of death in the world and its global burden is expected to continue increasing. In several types of cancers, reactive oxygen species (ROS) have been extensively linked to carcinogenesis and cancer progression. However, studies have reported conflicting evidence regarding the role of ROS in cancer, mostly dependent on the cancer type or the step of the tumorigenic process. We review recent studies describing diverse aspects of the interplay of ROS with cancer in the different stages of cancer progression, with a special focus on their role in carcinogenesis, their importance for cancer cell signaling and their relationship to the most prevalent cancer risk factors.

Porphylipoprotein Accumulation and Porphylipoprotein Photodynamic Therapy Effects Involving Cancer Cell-Specific Cytotoxicity

In photodynamic therapy (PDT) for neoplasms, photosensitizers selectively accumulate in cancer tissue. Upon excitation with light of an optimal wavelength, the photosensitizer and surrounding molecules generate reactive oxygen species, resulting in cancer cell-specific cytotoxicity. Porphylipoprotein (PLP) has a porphyrin-based nanostructure. The porphyrin moiety of PLP is quenched because of its structure. When PLP is disrupted, the stacked porphyrins are separated into single molecules and act as photosensitizers. Unless PLP is disrupted, there is no photosensitive disorder in normal tissues. PLP can attenuate the photosensitive disorder compared with other photosensitizers and is ideal for use as a photosensitizer. However, the efficacy of PLP has not yet been evaluated. In this study, the mechanism of cancer cell-specific accumulation of PLP and its cytotoxic effect on cholangiocarcinoma cells were evaluated. The effects were investigated on normal and cancer-like mutant cells. The cytotoxicity effect of PLP PDT in cancer cells was significantly stronger than in normal cells. In addition, reactive oxygen species regulated intracellular PLP accumulation. The cytotoxic effects were also investigated using a cholangiocarcinoma cell line. The cytotoxicity of PLP PDT was significantly higher than that of laserphyrin-based PDT, a conventional type of PDT. PLP PDT could also inhibit tumor growth in vivo.

Elevated Production of Mitochondrial Reactive Oxygen Species via Hyperthermia Enhanced Cytotoxic Effect of Doxorubicin in Human Breast Cancer Cell Lines MDA-MB-453 and MCF-7

Hyperthermia (HT) treatment is a noninvasive cancer therapy, often used with radiation therapy and chemotherapy. Compared with 37 °C, 42 °C is mild heat stress for cells and produces reactive oxygen species (ROS) from mitochondria. To involve subsequent intracellular accumulation of DOX, we have previously reported that the expression of ATP-binding cassette sub-family G member 2 (ABCG2), an exporter of doxorubicin (DOX), was suppressed by a larger amount of intracellular mitochondrial ROS. We then hypothesized that the additive effect of HT and chemotherapy would be induced by the downregulation of ABCG2 expression via intracellular ROS increase. We used human breast cancer cell lines, MCF-7 and MDA-MB-453, incubated at 37 °C or 42 °C for 1 h to clarify this hypothesis. Intracellular ROS production after HT was detected via electron spin resonance (ESR), and DOX cytotoxicity was calculated. Additionally, ABCG2 expression in whole cells was analyzed using Western blotting. We confirmed that the ESR signal peak with HT became higher than that without HT, indicating that the intracellular ROS level was increased by HT. ABCG2 expression was downregulated by HT, and cells were injured after DOX treatment. DOX cytotoxicity enhancement with HT was considered a result of ABCG2 expression downregulation via the increase of ROS production. HT increased intracellular ROS production and downregulated ABCG2 protein expression, leading to cell damage enhancement via DOX.

Mitochondrial reactive oxygen species and heme, non-heme iron metabolism

Mitochondria are one of the most important organelles for eukaryotes, including humans, to produce energy. In the energy-producing process, mitochondria constantly generate reactive oxygen species as a by-product of electrons leaking out from the electron transport chain react with oxygen. The active oxygen, in turn, plays pivotal roles in mediating several signalings, including those that are implicated in the development of some diseases such as neurodegenerative disease, cardiovascular disease, and carcinogenesis. This signaling, derived from mitochondrial reactive oxygen species, also affects intracellular iron homeostasis by regulating the expression of transporters. Heme iron is incorporated into cells through HCP1, and non-heme iron is transported by DMT1 in absorptive cells. Intracellular iron is exported by ferroportin and bound with transferrin. In most types of cell including erythrocyte, transferrin-bound iron is incorporated through transferrin-transferrin receptor system. We previously reported that the expression of HCP1 and DMT1 was upregulated in cancer cells and that overexpression of manganese superoxide dismutase, which is a mitochondrial-specific superoxide dismutase, downregulated the expression. These findings indicate that mitochondrial reactive oxygen species is associated with iron-related oxidative reactions. Recently, a mitochondria-specific iron transporter, mitoferrin, was identified, and the relationships among mitochondria, iron transportation, and diseases have been increasingly clarified.

Enhancement of PDT-cytotoxicity via ROS induced by indomethacin in metastatic breast cancer

Breast cancer is one of the most common types of cancers prevalent in women. Several types of breast cancers can easily metastasize to bone and cause disease complications such as hypercalcemia and pathologic fracture, thus compromising the quality of life of people affected by it. Bisphosphonate drugs are often used for the treatment of bone metastasis to suppress osteoclastic bone resorption. However, bisphosphonate has adverse effects on the gastrointestinal tract and kidneys and also induces osteonecrosis of the jaw. Photodynamic therapy (PDT) is an alternative cancer treatment approach with minimal invasiveness. It is a combination treatment that uses photosensitizers, which accumulate in tumor cells, followed by laser irradiation. We previously reported that the cellular incorporation of 5-aminolevulinic acid (5-ALA), which was a precursor of protoporphyrin IX (PpIX), was regulated by reactive oxygen species derived from mitochondria (mitROS). In this study, we investigated the incorporation of 5-ALA, accumulation of PpIX, and subsequent effects on cell viability after laser irradiation of two different breast cancer cell lines with different metastaticites. The highly metastatic breast cancer cell line 4T1E/M3 showed a significant increase in ROS production after treatment with indomethacin (IND). In addition, IND treatment enhanced the cellular uptake of 5-ALA via PEPT1 upregulation in 4T1E/M3, but not in the non-metastatic cell line. Overall, metastatic breast cancer is likely to be sensitive to ROS and activate signaling pathways associated with 5-ALA transportation, suggesting that ALA-PDT could be an effective treatment with low invasiveness for metastatic breast cancer.

5-Aminolevulinic acid induced apoptosis via oxidative stress in normal gastric epithelial cells

5-Aminolevulinic acid, a precursor of heme, is utilized in a variety of applications including cancer treatment, surgery, and plant nutrition. However, 5-aminolevulinic acid itself induces oxidative stress and subsequent lipid peroxidation. Reactive oxygen species are factors in oxidative stress, not only causing cellular injury but also inducing several signal transduction pathways. Especially in cancer cells, a significant amount of signalling activation and subsequent activation of protein is caused by the enhancement of reactive oxygen species production. Reactive oxygen species levels in normal cells are low and an oxidative condition is harmful; hence, administration of 5-aminolevulinic acid to normal cells may induce oxidative stress, resulting in cell death. In this study, we investigated the effect of 5-aminolevulinic acid on normal and cancer cells with regard to oxidative stress. We used the rat normal gastric cell line RGM and its cancer-like mutant cell line RGK. 5-Aminolevulinic acid treatment of RGM cells enhanced reactive oxygen species generation and induced apoptosis associated with p53, whereas RGK cells were unaffected. In addition, RGM cell viability was recovered by application of N-acetyl-l-cysteine or p53 inhibitor. These results suggest that 5-aminolevulinic acid causes oxidative stress in normal gastric cells and induces apoptosis via the p53-dependent pathway.

Breast Cancer Subtypes Present a Differential Production of Reactive Oxygen Species (ROS) and Susceptibility to Antioxidant Treatment

Due to their crucial role in cell metabolism and homeostasis, alterations in mitochondrial biology and function have been related to the progression of diverse diseases including cancer. One of the consequences associated to mitochondrial dysfunction is the production of reactive oxygen species (ROS). ROS are known to have a controversial role during cancer initiation and progression and although several studies have tried to manipulate intracellular ROS levels using antioxidants or pro-oxidation conditions, it is not yet clear how to target oxidation for cancer therapy. In this study, we found differences in mitochondrial morphology in breast cancer cells when compared to a non-tumorigenic cell line and differences in mitochondrial function among breast cancer subtypes when exploring gene-expression data from the TCGA tumor dataset. Interestingly, we found increased ROS levels in triple negative breast cancer (TNBC) cell lines and a dependency on ROS for survival since antioxidant treatment induced cell death in TNBC cells but not in an estrogen receptor positive (ER+) cell line. Moreover, we identified the mitochondria as the main source of ROS in TNBC cell lines. Our results indicate a potential use for ROS as a target for therapy in the TNBC subtype which currently has the worst prognosis among all breast cancers and remains as the only breast cancer subtype which lacks a targeted therapy.

Hyperthermia enhances photodynamic therapy by regulation of HCP1 and ABCG2 expressions via high level ROS generation

Photodynamic therapy (PDT) is a cancer treatment that make use of the cancer-specific accumulation of porphyrins. We have reported that mitochondrial reactive oxygen species (mitROS) upregulate uptake transporter of porphyrins, heme carrier protein-1 (HCP-1). The accumulation of cancer-specific porphyrins was increased by mitROS production, thereby the cancer-specific PDT cytotoxicity was enhanced. Thus we investigated whether mitROS production by hyperthermia can enhanced the cytotoxicity of PDT or not. In this study, 1 h of hyperthermia at 42 °C increased the mitROS production, and both the accumulation of cancer-specific porphyrins and the PDT cytotoxicity increased. Moreover, the authors treated cells with N-acetyl-L-cysteine (NAC) to examine the effect of mitROS. NAC inhibited the increasing ROS production after hyperthermia to restrain the post-treatment increase of cancer-specific porphyrins accumulation. Moreover, the increase of ROS production in cancer cells after hyperthermia upregulated HCP-1 expression and downregulated ABCG2 expression. These regulation were inhibited by NAC. These results suggest that hyperthermia treatment increased mitROS production, which involved HpD accumulation and enhanced PDT effects in cancer cells. The mechanism of this phenomenon was most likely to be due to both the upregulation of HCP-1 and the downregulation of ABCG2 by mitROS.

Acetic acid is an oxidative stressor in gastric cancer cells

Acetic acid can cause cellular injury. We previously reported that acetic acid induces cancer cell-selective death in rat gastric cells. However, the mechanism is unclear. Generally, cancer cells are more sensitive to reactive oxygen species than normal cells. Accordingly, in this study, we investigated the involvement of oxidative stress in cancer cell-selective death by acetic acid using normal gastric mucosal cells and cancerous gastric mucosal cells. The cancer cell-selective death was induced at the concentration of 2-5 µM acetic acid. Cancerous gastric mucosal cells had increased expression of monocarboxylic transporter 1 and high uptake of acetic acid, compared to normal gastric mucosal cells. The exposure of cancerous gastric mucosal cells to acetic acid enhanced production of reactive oxygen species and expression of monocarboxylic transporter 1, and induced apoptosis. In contrast, acetic acid showed minor effects in normal gastric mucosal cells. These results indicate that acetic acid induced cancer cell-selective death in gastric cells through a mechanism involving oxidative stress.

Monascus purpureus induced apoptosis on gastric cancer cell by scavenging mitochondrial reactive oxygen species

Monascus purpureus is a red dye derived from yeast rice and has been used as color additives for food in East Asia. Monascus purpureus consists of several bioactive components. Some of these components work as a radical scavenger, thus monascus purpureus would also eliminate reactive oxygen species. Cancer cells maintain the high level of reactive oxygen species than normal cell and are death by imbalance in pro-oxidant/antioxidant homeostasis. In this study, we investigated whether monascus purpureus induced cancer specific cell death by scavenging reactive oxygen species. Compared to normal cell, monascus purpureus had cancer specific cytotoxicity. Monascus purpureus and lovastatin, its component, scavenged free radicals caused by a xanthine/xanthine oxidase system, thus Monascus purpureus is likely to scavenge reactive oxygen species by a synergistic effect between lovastatin and other components. Monascus purpureus also decreased reactive oxygen species derived from mitochondria in cancer cells, and cellular apoptosis was induced via activation of caspase-9. Induction of apoptosis by reduction of reactive oxygen species generation decreased acid ceramidase, and this mechanism could be involved with increasing ceramide accumulation in cells.

Cancer cell-specific mitochondrial reactive oxygen species promote non-heme iron uptake and enhance the proliferation of gastric epithelial cancer cell

Iron is an essential nutrient for life and is involved in many important processes such as oxygen transport and DNA synthesis. However, excess amounts of iron can cause carcinogenesis by producing reactive oxygen species. Thus, the cellular transport of iron must be tightly regulated. In the human body, iron may be present as heme or non-heme iron. The mechanisms governing the cellular transport of these forms have not been clearly elucidated. We previously reported that the expression of an important heme transporter, heme carrier protein 1 was regulated by cancer-specific reactive oxygen species derived from mitochondria. In this study, we have asked if mitochondrial reactive oxygen species may also be related with non-heme iron transport. In order to address this question, we have investigated the relationship between mitochondrial reactive oxygen species and accumulation of cellular non-heme iron in a rat gastric normal, cancer and manganese superoxide dismutase-overexpressing cancer cell line, in which reactive oxygen species from mitochondria are specifically scavenged. We have also analyzed the expression of divalent metal transporter 1 and ferroprotin, involved in the incorporation and excretion of non-heme iron, respectively, as well as a hypoxia-related transcription factor HIF-1α, to elucidate the molecular mechanism of non-heme iron accumulation.

Grifolin inhibits tumor cells adhesion and migration via suppressing interplay between PGC1α and Fra-1 / LSF- MMP2 / CD44 axes

Grifolin, a farnesyl phenolic compound isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, exhibits effective antitumor bioactivity in previous study of our group and other lab. In this study, we observed that grifolin inhibited tumor cells adhesion and migration. Moreover, grifolin reduced reactive oxygen species (ROS) production and caused cellular ATP depletion in high-metastatic tumor cells. PGC1α (Peroxisome proliferator-activated receptor γ, coactivator 1α) encodes a transcriptional co-activator involved in mitochondrial biogenesis and respiration and play a critical role in the maintenance of energy homeostasis. Interestingly, grifolin suppressed the mRNA as well as protein level of PGC1α. We further identified that MMP2 and CD44 expressions were PGC1α inducible. PGC1α can bind with metastatic-associated transcription factors: Fra-1 and LSF and the protein-protein interaction was attenuated by grifolin treatment. Overall, these findings suggest that grifolin decreased ROS generation and intracellular ATP to suppress tumor cell adhesion/migration via impeding the interplay between PGC1α and Fra-1 /LSF-MMP2/CD44 axes. Grifolin may develop as a promising lead compound for antitumor therapies by targeting energy metabolism regulator PGC1α signaling.

Expression of Autophagy and Reactive Oxygen Species-Related Proteins in Lacrimal Gland Adenoid Cystic Carcinoma

PURPOSE

To investigate the difference of expression of autophagy and reactive oxygen species (ROS) related proteins in adenoid cystic carcinoma (ACC) of lacrimal gland in comparison with ACC of salivary gland.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded tissue samples from patients pathologically diagnosed as lacrimal gland ACC (n=11) and salivary gland ACC (n=64) were used. Immunochemistry was used to measure expression of autophagy related proteins [beclin-1, light chain (LC) 3A, LC3B, p62, and BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3)] and ROS related proteins [catalase, thioredoxinreductase, glutathione S-transferasepi (GSTpi), thioredoxin interacting protein, and manganese superoxide dismutase (MnSOD)]. The prognostic factors related to disease-free and overall survival (OS) in lacrimal gland ACC by log-rank tests, were determined.

RESULTS

GSTpi in stromal cells was more highly expressed in lacrimal gland ACC (p=0.006), however, MnSOD in epithelial cells was expressed more in salivary gland ACC (p=0.046). LC3B positivity and BNIP3 positivity in epithelial component were associated with shorter disease-free survival (both p=0.002), and LC3A positivity in stromal component was the factor related to shorter OS (p=0.005).

CONCLUSION

This is the first study to demonstrate the expression of autophagy and ROS related proteins in lacrimal gland ACC in comparison with the salivary gland ACC, which would provide a basis for further study of autophagy and ROS mechanism as novel therapeutic targets in lacrimal gland ACC.

Reactive oxygen species induced by non-steroidal anti-inflammatory drugs enhance the effects of photodynamic therapy in gastric cancer cells

Photodynamic therapy is useful for the treatment of cancer because it is minimally invasive for patients. Certain porphyrin compounds and their derivatives have been used as the photosensitizer because they accumulate specifically in cancerous tissues. However, the detailed mechanism of this phenomenon has not been clarified. We previously reported that a proton-coupled folate transporter, HCP1, transported porphyrins and that regulation of the protein was associated with cancer-specific reactive oxygen species from mitochondria (mitROS). Therefore, over-generation of mitROS could increase HCP1 expression and the effect of photodynamic therapy. We investigated whether pretreatment with indomethacin influenced photodynamic therapy by using a rat normal gastric mucosal cell line, RGM1, its cancer-like mutated cell line, RGK1, and a manganese superoxide dismutase (MnSOD)-overexpressing RGK cell line, RGK-MnSOD. Indomethacin promotes the generation of cellular mitROS by inhibiting the electron transport chain, and MnSOD scavenges the mitROS. We elucidated that indomethacin enhanced cancer-specific mitROS generation and increased HCP1 expression. Furthermore, RGK1 cells showed higher cellular incorporation of hematoporphyrin and better therapeutic effect with indomethacin treatment whereas RGK-MnSOD cells did not show a difference. Thus, we concluded that indomethacin improved the effect of photodynamic therapy by inducing increased mitROS generation in cancer cells.

Mitochondrial Reactive Oxygen Species and Photodynamic Therapy

Worldwide, the number of cancer cases is increasing. Typically, they are treated by either surgery or chemotherapy. However, these treatments may be undesirable in elderly patients or those who are under medication with antiplatelet drugs. Photodynamic therapy (PDT) represents a potentially attractive treatment option for these types of patients, since it does not involve surgery and has considerably reduced side effects compared to chemotherapy. Porphyrin, one of the most commonly used photosensitizers, has the convenient property of cancer-specific accumulation and therefore, is commonly used in PDT. However, the mechanism by which this cancer-specific accumulation occurs remains unclear. We previously reported that a heme-transport protein, HCP1, was capable of transporting porphyrin compounds. HCP1 expression is associated with increased hypoxia, although the detailed mechanism by which this regulation occurs is also unknown. Here, we review available data on the mechanism of regulation of HCP1 expression through mitochondrial reactive oxygen species (mitROS). Specifically, cancer cells show increased expression of HCP1 compared to normal cells and this over-expression is reduced in cancer cells over-expressing the mitROS scavenging enzyme manganese superoxide dismutase (MnSOD). Thus we conclude that mitROS is involved in regulating HCP1 expression.

Manganese superoxide dismutase promotes interaction of actin, S100A4 and Talin, and enhances rat gastric tumor cell invasion

It has been demonstrated that cancer cells are under high levels of oxidative stress and express high levels of Manganese superoxide dismutase (MnSOD) to protect themselves and support the anabolic metabolism needed for growth and cell motility. The aim of this study was to identify proteins that may have a correlation with invasion and redox regulation by mitochondrial reactive oxygen species (ROS). MnSOD scavenges superoxide anions generated from mitochondria and is an important regulator of cellular redox status. Oxidative posttranslational modification of cysteine residues is a key mechanism that regulates protein structure and function. We hypothesized that MnSOD regulates intracellular reduced thiol status and promotes cancer invasion. A proteomic thiol-labeling approach with 5-iodoacetamidofluorescein was used to identify changes in intracellular reduced thiol-containing proteins. Our results demonstrate that overexpression of MnSOD maintained the major structural protein, actin, in a reduced state, and enhanced the invasion ability in gastric mucosal cancer cells, RGK1. We also found that the expression of Talin and S100A4 were increased in MnSOD-overexpressed RGK1 cells. Moreover, Talin bound not only with actin but also with S100A4, suggesting that the interaction of these proteins may, in part, contribute to the invasive ability of rat gastric cancer.

Hitting the Bull's-Eye in Metastatic Cancers-NSAIDs Elevate ROS in Mitochondria, Inducing Malignant Cell Death

Tumor metastases that impede the function of vital organs are a major cause of cancer related mortality. Mitochondrial oxidative stress induced by hypoxia, low nutrient levels, or other stresses, such as genotoxic events, act as key drivers of the malignant changes in primary tumors to enhance their progression to metastasis. Emerging evidence now indicates that mitochondrial modifications and mutations resulting from oxidative stress, and leading to OxPhos stimulation and/or enhanced reactive oxygen species (ROS) production, are essential for promoting and sustaining the highly metastatic phenotype. Moreover, the modified mitochondria in emerging or existing metastatic cancer cells, by their irreversible differences, provide opportunities for selectively targeting their mitochondrial functions with a one-two punch. The first blow would block their anti-oxidative defense, followed by the knockout blow—promoting production of excess ROS, capitulating the terminal stage—activation of the mitochondrial permeability transition pore (mPTP), specifically killing metastatic cancer cells or their precursors. This review links a wide area of research relevant to cellular mechanisms that affect mitochondria activity as a major source of ROS production driving the pro-oxidative state in metastatic cancer cells. Each of the important aspects affecting mitochondrial function are discussed including: hypoxia, HIFs and PGC1 induced metabolic changes, increased ROS production to induce a more pro-oxidative state with reduced antioxidant defenses. It then focuses on how the mitochondria, as a major source of ROS in metastatic cancer cells driving the pro-oxidative state of malignancy enables targeting drugs affecting many of these altered processes and why the NSAIDs are an excellent example of mitochondria-targeted agents that provide a one-two knockout activating the mPTP and their efficacy as selective anticancer metastasis drugs.

Fluorescence-based co-culture of normal and cancerous cells as an indicator of therapeutic effects in cancer

Comprehensive evaluation of the effects of cancer therapies in vitro is difficult because of the need to distinguish the main effects from the side effects within the data. This problem cannot be overcome by methods involving monoculture, because the effects of anti-cancer drugs in a monoculture can only be measured on either normal or cancerous cells in isolation. In order to promote therapeutic development, therefore, we need a novel drug evaluation method which can simultaneously determine both therapeutic activity and toxicity under a co-culture of normal and cancerous cells. Co-culture creates a more biomimetic condition in comparison to monoculture. The novel method proposed in this study uses an easy experiment for estimating the effects of treatments with various kinds of drugs as a solution to the abovementioned problems. We have previously established two cell lines: a rat gastric mucosal cell line (RGM) and its corresponding cancerous mutant cell line (RGK). In this study, we have developed a new evaluation procedure using a co-culture of green fluorescent protein-expressing RGM cells (RGM-GFP) and kusabira orange-expressing RGK cells (RGK-KO). These cell lines emit green and red fluorescence, respectively. We demonstrated the capability of the method in evaluations of the cancer-selective effects of anti-cancer drugs and X-ray treatment. These results clearly distinguished the cancer-selective toxicity of the applied therapies.

Mitochondrial reactive oxygen species accelerate the expression of heme carrier protein 1 and enhance photodynamic cancer therapy effect

Photodynamic therapy using hematoporphyrin and its derivatives is clinically useful for cancer treatments. It has been reported that cancer cells incorporate hematoporphyrin and its derivatives via heme carrier protein 1, which is a proton-coupled folate transporter. However, the mechanism of this protein expression has not been elucidated. In general, the concentration of reactive oxygen species in cancer cells is higher than that in normal cells. We previously reported that reactive oxygen species from mitochondria involved in the expression of peptide transporter 1 and accelerate the uptake of 5-aminolevulinic acid, which is a precursor of protoporphyrin IX. We suggested mitochondrial reactive oxygen species also regulated the expression of heme carrier protein 1. In this study, we used a rat gastric mucosal cell line RGM1 and its cancer-like mutated cell line RGK1. We clarified the expression of heme carrier protein 1 increased in cancer cells and it decreased in manganese superoxide dismutase expressed cancer cells. In addition, the uptake level of hematoporphyrin and photodynamic therapeutic effect were also decreased in manganese superoxide dismutase expressed cancer cells in comparison with cancer cells. Thus, we concluded that mitochondrial reactive oxygen species regulated heme carrier protein 1 expression and photodynamic therapeutic effect.

Acetaldehyde is an oxidative stressor for gastric epithelial cells

Alcohol drinking and smoking contain the risk of a carcinogenesis. Acetaldehyde is content in cigarette smoke and an ethanol metabolite. However the clear evidence for reactive oxygen species (ROS) generation by acetaldehyde in gastric cells in vitro is none. In this study, we elucidated acetaldehyde is an oxidative stress inducer on rat gastric epithelial cells by electron paramagnetic resonance measurement in living cells. We also confirmed whether acetaldehyde-induced cellular ROS was derived from mitochondria or not. The results of cellular ROS determination showed that an increment of cellular ROS was shown for 15 min in living cells from exposing 0.1% (v/v) acetaldehyde. Lipid peroxidation in cellular membrane also induced by 0.1% ethanol and the tendency is same in the results of cellular ROS determination. JC-1 stained showed the decrement of mitochondrial membrane potential. These results indicated that acetaldehyde is not merely a necrotizing factor for gastric epithelial cells, but also an oxidative stress inducer via injured mitochondria.

Optical cell separation from three-dimensional environment in photodegradable hydrogels for pure culture techniques

Cell sorting is an essential and efficient experimental tool for the isolation and characterization of target cells. A three-dimensional environment is crucial in determining cell behavior and cell fate in biological analysis. Herein, we have applied photodegradable hydrogels to optical cell separation from a 3D environment using a computer-controlled light irradiation system. The hydrogel is composed of photocleavable tetra-arm polyethylene glycol and gelatin, which optimized cytocompatibility to adjust a composition of crosslinker and gelatin. Local light irradiation could degrade the hydrogel corresponding to the micropattern image designed on a laptop; minimum resolution of photodegradation was estimated at 20 µm. Light irradiation separated an encapsulated fluorescent microbead without any contamination of neighbor beads, even at multiple targets. Upon selective separation of target cells in the hydrogels, the separated cells have grown on another dish, resulting in pure culture. Cell encapsulation, light irradiation and degradation products exhibited negligible cytotoxicity in overall process.

Reactive oxygen species involved cancer cellular specific 5-aminolevulinic acid uptake in gastric epithelial cells

Photodynamic therapy and photodynamic diagnosis using 5-aminolevulinic acid (ALA) are clinically useful for cancer treatments. Cancer cells have been reported that 5-aminolevulinic acid is incorporated via peptide transporter 1, which is one of the membrane transport proteins, and has been reported to be significantly expressed in various gastrointestinal cancer cells such as Caco-2. However, the mechanism of this protein expression has not been elucidated. Concentration of reactive oxygen species (ROS) is higher in cancer cells in comparison with that of normal cells. We have previously reported that ROS derived from mitochondria is likely related to invasions and proliferations of cancer cells. Since 5-aminolevulinic acid is the most important precursor of heme which is necessary protein for cellular proliferations, mitochondrial ROS (mitROS) may be also related to peptide transporter 1 expressions. In this study, we used a rat gastric mucosal cell line RGM1 and its cancer-like mutated cell line RGK1, and we clarified the ALA uptake mechanism and its relations between mitROS and peptide transporter 1 expression in RGK1. We also used our self-established stable clone of cell which over-expresses manganese superoxide dismutase, a mitROS scavenger. We studied differences of the photodynamic therapy effects in these cells after ALA administrations to clear the influence of mitROS.

Selective accumulation of hematoporphyrin derivative in glioma through proton-coupled folate transporter SLC46A1

The mechanism of tumor-specific porphyrin accumulation is not clear. We investigated the expression of proton-coupled folate transporter SLC46A1 in glioma and aimed to clarify the relationship between tumor fluorescence and SLC46A1 expression.We confirmed the expression of SLC46A1 in surgical specimens from 24 glioma patients by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). We also investigated SLC46A1 expression in glioma cell lines by RT-PCR. The cellular uptake of hematoporphyrin derivative in vitro was measured with a microplate reader and fluorescence microscope. In these experiments, we used three human malignant glioma cell lines: U87, U251 and T98G. Immunohistochemistry showed SLC46A1 positivity in the malignant tumor lesion of each specimen. Strong positive SLC46A1 expression was observed in 33% of grade IV, 22% of grade III and 17% of grade II gliomas. All four randomly obtained malignant glioma frozen sections expressed SLC46A1 mRNA by RT-PCR. In vitro, U87 showed the least SLC46A1 expression, U251 was intermediate, and T98G showed the most expression. The amount of hematoporphyrin derivative (HpD) cellular uptake correlated with SLC46A1 expression. These results suggest that the accumulation of HpD in glioma cells is related to SLC46A1 function and SLC46A1 is involved in the mechanism of glioma fluorescence.