Apoptosis induced by etoposide in small-cell lung cancer cell lines

ZMYM3 May Promote Cell Proliferation in Small Cell Lung Carcinoma

Zinc finger, myeloproliferative, and mental retardation-type containing 3 (ZMYM3) is a highly conserved protein among vertebrates. Although it promotes DNA repair and moderate histone acetylation, the other functions of ZMYM3 remain unclear. We herein examined the physiological functions of ZMYM3 in human lung cancer using a ZMYM3-knockdown small cell lung cancer (SCLC) cell line. ZMYM3-knockdown SCLC cells grew slowly and the Ki-67 labeling index was lower in ZMYM3-knockdown cells than in mock cells. The subcutaneous tumors that formed after xenotransplantation into immunodeficient mice were slightly smaller in the ZMYM3-knockdown group than in the mock group. Furthermore, public RNA-sequencing data analyses showed similar RNA profiles between ZMYM3 and some cell proliferation markers. These results indicate that ZMYM3 promotes cell proliferation in human lung carcinomas, particularly SCLC.

Effects of PI3K inhibitor NVP-BKM120 on overcoming drug resistance and eliminating cancer stem cells in human breast cancer cells

The multidrug resistance (MDR) phenotype often accompanies activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, which renders a survival signal to withstand cytotoxic anticancer drugs and enhances cancer stem cell (CSC) characteristics. As a result, PI3K/AKT-blocking approaches have been proposed as antineoplastic strategies, and inhibitors of PI3K/AKT are currently being trailed clinically in breast cancer patients. However, the effects of PI3K inhibitors on MDR breast cancers have not yet been elucidated. In the present study, the tumorigenic properties of three MDR breast cancer cell lines to a selective inhibitor of PI3K, NVP-BKM120 (BKM120), were assessed. We found that BKM120 showed a significant cytotoxic activity on MDR breast cancer cells both in vitro and in vivo. When doxorubicin (DOX) was combined with BKM120, strong synergistic antiproliferative effect was observed. BKM120 activity induced the blockage of PI3K/AKT signaling and NF-κB expression, which in turn led to activate caspase-3/7 and caspase-9 and changed the expression of several apoptosis-related gene expression. Furthermore, BKM120 effectively eliminated CSC subpopulation and reduced sphere formation of these drug-resistant cells. Our findings indicate that BKM120 partially overcomes the MDR phenotype in chemoresistant breast cancer through cell apoptosis induction and CSC abolishing, which appears to be mediated by the inhibition of the PI3K/AKT/NF-κB axis. This offers a strong rationale to explore the therapeutic strategy of using BKM120 alone or in combination for chemotherapy-nonresponsive breast cancer patients.

Genome-wide transcriptional analysis of apoptosis-related genes and pathways regulated by H2AX in lung cancer A549 cells

Histone H2AX is a novel tumor suppressor protein and plays an important role in apoptosis of cancer cells. However, the role of H2AX in lung cancer cells is unclear. The detailed mechanism and epigenetic regulation by H2AX remain elusive in cancer cells. We showed that H2AX was involved in apoptosis of lung cancer A549 cells as in other tumor cells. Knockdown of H2AX strongly suppressed apoptosis of A549 cells. We clarified the molecular mechanisms of apoptosis regulated by H2AX based on genome-wide transcriptional analysis. Microarray data analysis demonstrated that H2AX knockdown in A549 cells affected expression of 3,461 genes, including upregulation of 1,435 and downregulation of 2,026. These differentially expressed genes were subjected to bioinformatic analysis for exploring biological processes regulated by H2AX in lung cancer cells. Gene ontology analysis showed that H2AX affected expression of many genes, through which, many important functions including response to stimuli, gene expression, and apoptosis were involved in apoptotic regulation of lung cancer cells. Pathway analysis identified the mitogen-activated protein kinase signaling pathway and apoptosis as the most important pathways targeted by H2AX. Signal transduction pathway networks analysis and chromatin immunoprecipitation assay showed that two core genes, NFKB1 and JUN, were involved in apoptosis regulated by H2AX in lung cancer cells. Taken together, these data provide compelling clues for further exploration of H2AX function in cancer cells.

Identification of biomarkers for apoptosis in cancer cell lines using metabolomics: tools for individualized medicine

BACKGROUND

Metabolomics is a versatile unbiased method to search for biomarkers of human disease. In particular, one approach in cancer therapy is to promote apoptosis in tumour cells; this could be improved with specific biomarkers of apoptosis for monitoring treatment. We recently observed specific metabolic patterns in apoptotic cell lines; however, in that study, apoptosis was only induced with one pro-apoptotic agent, staurosporine.

OBJECTIVE

The aim of this study was to find novel biomarkers of apoptosis by verifying our previous findings using two further pro-apoptotic agents, 5-fluorouracil and etoposide, that are commonly used in anticancer treatment.

METHODS

Metabolic parameters were assessed in HepG2 and HEK293 cells using the newborn screening assay adapted for cell culture approaches, quantifying the levels of amino acids and acylcarnitines with mass spectrometry.

RESULTS

We were able to identify apoptosis-specific changes in the metabolite profile. Moreover, the amino acids alanine and glutamate were both significantly up-regulated in apoptotic HepG2 and HEK293 cells irrespective of the apoptosis inducer.

CONCLUSION

Our observations clearly indicate the potential of metabolomics in detecting metabolic biomarkers applicable in theranostics and for monitoring drug efficacy.

Prospective randomized trial of short-term neoadjuvant chemotherapy for advanced gastric cancer

BACKGROUND

We performed short-term neoadjuvant chemotherapy (s-NAC) to examine whether anticancer drugs can change the proliferative ability of cancer cells in gastric cancer patients.

METHODS

Chemotherapy was performed for 72 h before gastrectomy in 63 gastric cancer patients. Patients were classed into four groups: Group F, 16 cases who received a single administration of 5-fluorouracil (5-FU); Group C, 15 cases who received a single administration of cis-diamminedichloroplatinum (CDDP; cisplatin); Group FC, 16 cases who received both 5-FU+CDDP; and a Control group, 16 cases who did not receive chemotherapy. We reviewed neoadjuvant biopsy tissue and gastric cancer tissue delivered by operation in these cases. The TUNEL method and immunohistochemistry with an anti-MIB-1 antibody were used to evaluate cellular apoptosis and proliferative ability, respectively. The apoptotic index (AI) and an MIB-1 index (MI) were also calculated.

RESULTS

There were no differences in AI or MI in biopsy tissue between the groups. The AI of gastric cancer tissue in Group FC was significantly higher than in the other groups (P < 0.01). The MI of Group FC was significantly lower than in the other groups (P < 0.05). In addition, after s-NAC operation there was a significant inhibition of proliferative potency and an induction of apoptosis in Group FC.

CONCLUSION

Combination of CDDP and 5-FU reduced proliferative potency and increased cellular apoptosis in gastric cancer cells.

Role of apoptosis in the response of lung carcinomas to anti-cancer treatment

Resistance of tumor cells to treatment often accounts for the failure of traditional forms of anti-cancer therapy. It is well known that tumors from the same histological group and stage of development are highly heterogeneous in their sensitivity to therapy. Among the factors that can influence tumor sensitivity are DNA repair capacity, distribution of cells throughout the cell cycle, proliferation potential, etc. In many cases, anti-cancer therapy eliminates tumor cells via apoptosis, an active form of cell death characterized by cell shrinkage and the removal of cells in a neat, orderly fashion. However, this process is not always efficient. In the present review, the precise role that apoptosis plays in the response of lung carcinomas to chemotherapy and radiation treatment is discussed.

Up-regulation of telomerase activity in human pancreatic cancer cells after exposure to etoposide

Telomerase plays a critical role in the development of cellular immortality and oncogenesis. Activation of telomerase occurs in a majority of human malignant tumours, and the relation between telomerase and vulnerability to drug-mediated apoptosis remains unclear. In this study, we demonstrate, for the first time, up-regulation of telomerase activity in human pancreatic cancer cells treated with etoposide, a topoisomerase II inhibitor. Exposure of MIA PaCa-2 cells to etoposide at various concentrations (1-30 microM) resulted in two- to threefold increases in telomerase activity. Up-regulation was detectable 24 h after drug exposure and was accompanied by enhanced expression of mRNA of the human telomerase reverse transcriptase. Telomerase activation was also observed in AsPC-1 and PANC-1 cells but not in KP-3 and KP-1N cells. Furthermore, we found a negative correlation between increased telomerase activity and the percentage of dead cells after etoposide treatment. These findings suggest the existence of an anti-apoptotic pathway through which telomerase is up-regulated in response to DNA damage. This telomerase activation pathway may be one of the mechanisms responsible for the development of etoposide resistance in certain pancreatic cancer cells.

doc-1--mediated apoptosis in malignant hamster oral keratinocytes

PURPOSE

Cell cycle mediators involved in inducing apoptosis are frequently deregulated during carcinogenesis. Deleted in oral cancer-1 (doc-1) is an S-phase regulator that is inactivated during oral carcinogenesis. Transfection of doc-1 into malignant oral keratinocytes leads to increased cell loss. It is hypothesized that ectopic expression of doc-1 in hamster oral cancer cells induces apoptosis.

MATERIALS AND METHODS

Malignant hamster oral keratinocytes (wt-HCPC-1), which lack measurable doc-1 mRNA and protein, were previously transfected with either a CMV-doc-1 expression vector construct (doc-HCPC-1) or the parental control vector pcDNA3 (cv-HCPC-1). A trypan blue exclusion assay was performed to examine cell death in the parental or wild-type HCPC-1 keratinocytes, HCPC-1 transfected with the parental pcDNA3 vector, and the doc-1 transfected HCPC-1 cells. To examine whether ectopic expression of doc-1 mediates gross cellular changes consistent with apoptosis, toluidine blue-safranin differential staining and the quantitative fluorescent microscopy assays were performed. To identify early apoptotic cytochemical changes observed in the cell membrane and nucleus, annexin V/propidium iodide (PI) fluorescence-activated cell sorter (FACS) analysis and the terminal deoxytransferase-mediated dUTP nick-end labeling (TUNEL) assay were performed.

RESULTS

Doc-HCPC-1 showed elevated numbers of dead cells over wt-HCPC-1 and cv-HCPC-1 in the trypan blue exclusion assay. Toluidine blue-safranin staining and quantitative fluorescent microscopy showed significant morphologic changes in the doc-1 transfectants consistent with apoptosis (P < .05). TUNEL assays (P < .05) and annexin V/PI FACS analysis (P < .05) also showed early cytochemical changes in the doc-HCPC-1 transfectants, confirming that ectopic expression of doc-1 induces apoptosis.

CONCLUSIONS

These data suggest that doc-1 induces apoptosis in malignant hamster oral keratinocytes. It is hypothesized that doc-1 is a mediator of apoptosis that is inactivated during hamster oral carcinogenesis.

Manganese superoxide dismutase negatively regulates the induction of apoptosis by 5-fluorouracil, peplomycin and gamma-rays in squamous cell carcinoma cells

We investigated the relationship between manganese superoxide dismutase (Mn-SOD) activity and apoptosis induced by anticancer drugs and radiation. Although the activity of copper, zinc-SOD did not differ greatly among 9 squamous cell carcinoma (SCC) cell lines (OSC-1 to OSC-9), the Mn-SOD activity did differ among the cell lines. The Mn-SOD activity was increased by treatments with 5-fluorouracil (5-FU), peplomycin and 137Cs, reaching plateau levels at 12 h after treatment and then decreasing gradually. When OSC-1 and OSC-3, and OSC-2 and OSC-4 were examined as representative cell lines with low and high Mn-SOD activity, respectively, the decrease was more prominent in OSC-1 and OSC-3 than in OSC-2 and OSC-4. The intracellular levels of superoxide and hydrogen peroxide (H2O2) were increased after treatment with the anticancer agents, and the increases were larger in OSC-1 and OSC-3 than in OSC-2 and OSC-4. The decrease of mitochondrial membrane potential (deltapsi(m)) by the anticancer agents was marked in OSC-1 and OSC-3. Correspondingly, the release of cytochrome c, the activation of caspase-3 and the cleavage of poly(ADP-ribose)polymerase were stronger in OSC-3 than in OSC-4. In addition, apoptosis induced by the anticancer agents was prominent in OSC-3, exhibiting a close relationship with the deltapsi(m) and the H2O2 level. These results indicate that Mn-SOD in SCC cells modulates apoptosis induction and the inactivation of Mn-SOD might be a promising strategy for SCC treatment.

Cell cycle disturbances and apoptosis induced by topotecan and gemcitabine on human lung cancer cell lines

Apoptosis is a major mode of cell death in response to cytotoxic drug treatment. A correlation between induction of apoptosis and chemosensitivity has been documented in some preclinical models. Topotecan (a topoisomerase I inhibitor) and gemcitabine (a deoxycytidine analogue), two active new drugs for the treatment of lung cancer, were evaluated for their growth inhibitory effect on human lung cancer cell lines and their effect on cell cycle perturbation, apoptosis and apoptosis-related genes. The cytotoxicities of topotecan and gemcitabine on the human lung cancer cell lines H460 (wild-type-p53) and H322 (mutant p53 were determined after 72 h drug exposure employing the MTT assay. The apoptotic index (AI) was assessed by three methods: analysis of morphological changes using May-Grünwald-Giemsa (MGG) staining, the TUNEL assay and FACS analysis. Cell cycle disturbances were studied by FACS and the number of cells expressing p53 and p21 were determined by immunohistochemistry. Both gemcitabine and topotecan had potent growth inhibitory effects in human lung cancer cell lines; combination treatment with these two drugs showed some additivity but no synergism. Induction of apoptosis after treatment was concentration- and time-dependent with both drugs and IC80 concentrations induced the highest values. The DNA histograms at 4, 24, 48 and 72 h indicate that topotecan at IC80 concentrations causes accumulation of cells in S and G2/M phases, whereas gemcitabine at IC80 concentrations causes, accumulation of cells in G1 phase. Both compounds induced p53 and p21 expression in the H460 cell line but not in the H322 cell line; the percentage of cells expressing p53 was highest at IC80 values, whereas the highest percentage of p21 positive cells could be induced with IC50 values. This could suggest that p53 induces cell cycle arrest at low drug concentrations, whereas p53 induces apoptosis at higher concentrations. In conclusion, p53-dependent and independent pathways of apoptosis exist in lung cancer cell lines. Activation of the p53 pathway depends on the induced cellular damage. Understanding the cell cycle disturbances induced by these drugs may help in the design of more rational treatment schedules.

EAT/mcl-1, a member of the bcl-2 related genes, confers resistance to apoptosis induced by cis-diammine dichloroplatinum (II) via a p53-independent pathway

EAT/mcl-1 showed increased expression during the differentiation of a multipotent human embryonic carcinoma cell line, NCR-G3, and of myeloblastic cells "ML-1," and has sequence similarity to Bcl-2. In this present study, we determined whether the apoptotic cell death induced by chemotherapeutic agents could be inhibited by EAT/mcl-1, as has been found with Bcl-2. Cells transfected with EAT/mcl-1 showed higher resistance to cis-diammine dichloroplatinum (II) (CDDP) and carboplatin compared with the parental line (10)1 and neomycin-resistance gene-transfected clone, (10)1/neo. There was, however, no difference in sensitivity to etoposide, N,N-bis-(2-chloroethyl)-N'-(3-hydroxypropyl) phosphordiamidic acid cyclic ester monohydrate, adriamycin or other chemotherapeutic agents tested. DNA fragmentation of the parental cells following treatment with CDDP and carboplatin was observed in a concentration-dependent manner. In contrast, cells transfected with EAT/mcl-1 did not show DNA fragmentation following treatment with the same concentration of these drugs. EAT/mcl-1 was capable of delaying the onset of p53-independent apoptosis, although it could not inhibit apoptosis completely. Since CDDP and carboplatin damage DNA and then activate c-abl and the JNK/SAPK pathway, EAT/mcl-1 may inhibit p53-independent apoptosis through a c-abl/JNK (SAPK)-dependent mechanism. EAT/mcl-1 has functional homology to Bcl-2 in that it can enhance cell viability under conditions which otherwise cause apoptosis and increase resistance to chemotherapeutic agents.

Apoptosis in neurological disease

Enormous interest in cell death in the past several years has moved apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development, and immunological functioning. It also occurs in pathological conditions, including cancer and acquired immunodeficiency syndrome, and is implicated in neurodegenerative diseases. Claims of neuronal apoptosis induced by various agents and conditions are published regularly, but in many instances the data are questionable because they are incomplete. This review presents a brief history of apoptosis and describes the evidence required before claims of apoptosis are made. Summaries and critiques of important investigations concerning the genetic and biochemical regulation of neuronal apoptosis are presented, as are other studies describing connections between apoptosis and neuronal cell death in physiological and pathological situations. There is a realization that apoptosis can be programmed and is distinguishable from necrotic cell death. Combining apoptosis with programmed cell death produces misleading terminology and confusion over these two forms of cell degeneration. Further investigations into neuronal apoptosis should focus on all of the criteria that the original investigators outlined 25 years ago, to clarify whether apoptosis and/or another form of cell death mediates neuronal degeneration in physiological settings and in neurological diseases such as Alzheimer's disease, Parkinson's disease, epilepsy, and ischemia/stroke.

A topoisomerase II inhibitor, NK109, induces DNA single- and double-strand breaks and apoptosis

2,3-(Methylenedioxy)-5-methyl-7-hydroxy-8-methoxybenzo[c]phenanthr idinium hydrogensulfate dihydrate, called NK109, is a benzo[c]phenanthridine derivative, which inhibits DNA topoisomerase II activity by stabilizing the DNA-enzyme-drug complex, and shows strong growth-inhibitory effects on several human cancer cells. In the present study, NK109 treatment induced DNA fragmentation and a rise in the level of cytoplasmic nucleosomes, which are markers of apoptosis, in human small-cell lung carcinoma SBC-3 cells. These effects were inhibited by zinc ions and enhanced by cycloheximide or actinomycin D. Dose-dependent single- and double-strand DNA breaks were observed, using alkaline and neutral elution assays, in SBC-3 cells treated with more than 0.2 microM NK109 for 4 h. Treatment with NK109 caused more DNA single- and double-strand breaks than treatment with an equimolar amount of VP-16. These results suggest that NK109 induces DNA strand breaks and apoptosis. In addition, it appears that this process does not require protein or RNA synthesis, but involves a specific endonuclease which is inhibited by zinc ions.

Review article: The role of oncogenes, tumour suppressor genes and growth factors in oral squamous cell carcinoma: a case of apoptosis versus proliferation

Mutation, deactivation and disregulated expression of oncogenes and tumour-suppressor genes may be involved in the pathogenesis of oral squamous cell carcinoma (SCC). Deactivation of the p53 tumour-suppressor gene allows cell proliferation and blocks apoptosis of malignant oral keratinocytes. Mutation in the ras oncogene results in persistent mitogenic signalling. Upregulatioed c-Myc expression, in the presence of growth factors, provides an additional proliferative signal. Loss of retinoblastoma tumour-suppressor gene (Rb) function may contribute to oral keratinocyte hyperproliferation and recent evidence suggests that simultaneous deactivation of both p53 and Rb is required for tumourigenesis. Enhanced Bcl-2 and reduced Fas expression inhibit tumour cell apoptosis and may convey resistance to cytotoxic drugs and T cell-mediated cytotoxicity, respectively. Exogenous mutagens such as tobacco, alcohol and viral oncogenes may cause altered expression of oncogenes and tumour-suppressor genes in some cases of oral SCC. The impact of these mechanisms on future therapies for oral SCC is highlighted.

Enhancement of Ca(2+)-dependent endonuclease activity in L1210 cells during apoptosis induced by 1-beta-D-arabinofuranosylcytosine: possible involvement of activating factor(s)

Internucleosomal DNA fragmentation and morphological changes in nuclei typical of apoptosis were observed in L1210 cells incubated with 1.0 micrograms/ml of 1-beta-D-arabinofuranosylcytosine (ara-C). To investigate the mechanisms involved, we examined the activities of endogenous endonucleases in nuclei and cytoplasm. Both fractions of control cells contained Ca(2+)-dependent endonuclease which was capable of mediating internucleosomal DNA fragmentation. The assay system using two kinds of target substrates, i.e., nuclear chromatin of CCRF-CEM cells and naked DNA purified from the same cells, revealed that the activity of Ca(2+)-dependent endonuclease was enhanced in the crude nuclear extracts of cells treated with 1.0 microgram/ml of ara-C for 24 h or 48 h. The activity was extracted more easily from ara-C-treated cells than control cells without sonication of the nuclear fraction. On the other hand, in the cytoplasmic fraction of the cells, the activity towards naked DNA was unchanged, whereas that towards nuclear chromatin was clearly enhanced. These results suggest that internucleosomal DNA fragmentation induced by ara-C treatment is associated with enhancement and activation of constitutively expressed Ca(2+)-dependent endonuclease in L1210 cells.

Etoposide-induced cell cycle delay and arrest-dependent modulation of DNA topoisomerase II in small-cell lung cancer cells

As an approach to the rational design of combination chemotherapy involving the anti-cancer DNA topoisomerase II poison etoposide (VP-16), we have studied the dynamic changes occurring in small-cell lung cancer (SCLC) cell populations during protracted VP-16 exposure. Cytometric methods were used to analyse changes in target enzyme availability and cell cycle progression in a SCLC cell line, mutant for the tumour-suppressor gene p53 and defective in the ability to arrest at the G1/S phase boundary. At concentrations up to 0.25 microM VP-16, cells became arrested in G2 by 24 h exposure, whereas at concentrations 0.25-2 microM G2 arrest was preceded by a dose-dependent early S-phase delay, confirmed by bromodeoxyuridine incorporation. Recovery potential was determined by stathmokinetic analysis and was studied further in aphidicolin-synchronised cultures released from G1/S and subsequently exposed to VP-16 in early S-phase. Cells not experiencing a VP-16-induced S-phase delay entered G2 delay dependent upon the continued presence of VP-16. These cells could progress to mitosis during a 6-24 h period after drug removal. Cells experiencing an early S-phase delay remained in long-term G2 arrest with greatly reducing ability to enter mitosis up to 24 h after removal of VP-16. Irreversible G2 arrest was delimited by the induction of significant levels of DNA cleavage or fragmentation, not associated with overt apoptosis, in the majority of cells. Western blotting of whole-cell preparations showed increases in topoisomerase II levels (up to 4-fold) attributable to cell cycle redistribution, while nuclei from cells recovering from S-phase delay showed enhanced immunoreactivity with an anti-topoisomerase II alpha antibody. The results imply that traverse of G1/S and early S-phase in the presence of a specific topoisomerase II poison gives rise to progressive low-level trapping of topoisomerase II alpha, enhanced topoisomerase II alpha availability and the subsequent irreversible arrest in G2 of cells showing limited DNA fragmentation. We suggest that protracted, low-dose chemotherapeutic regimens incorporating VP-16 are preferentially active towards cells attempting G1/S transition and have the potential for increasing the subsequent action of other topoisomerase II-targeted agents through target enzyme modulation. Combination modalities which prevent such dynamic changes occurring would act to reduce the effectiveness of the VP-16 component.