Effects of gemcitabine on cell proliferation and apoptosis in non-small-cell lung cancer (NSCLC) cell lines

Mind the Curve: Dose-Response Fitting Biases the Synergy Scores across Software Used for Chemotherapy Combination Studies

Drug combinations are increasingly studied in the field of anticancer agents. Mathematical models, such as Loewe, Bliss, and HSA, are used to interpret drug combinations, while informatics tools help cancer researchers identify the most effective combinations. However, the different algorithms each software uses lead to results that do not always correlate. This study compared the performance of Combenefit (Ver. 2.021) and SynergyFinder (Ver. 3.6) in analyzing drug synergy by studying combinations involving non-steroidal analgesics (celecoxib and indomethacin) and antitumor drugs (carboplatin, gemcitabine, and vinorelbine) on two canine mammary tumor cell lines. The drugs were characterized, their optimal concentration-response ranges were determined, and nine concentrations of each drug were used to make combination matrices. Viability data were analyzed under the HSA, Loewe, and Bliss models. Celecoxib-based combinations showed the most consistent synergistic effect among software and reference models. Combination heatmaps revealed that Combenefit gave stronger synergy signals, while SynergyFinder produced better concentration-response fitting. When the average values of the combination matrices were compared, some combinations shifted from synergistic to antagonistic due to differences in the curve fitting. We also used a simulated dataset to normalize each software's synergy scores, finding that Combenefit tends to increase the distance between synergistic and antagonistic combinations. We conclude that concentration-response data fitting biases the direction of the combination (synergistic or antagonistic). In contrast, the scoring from each software increases the differences among synergistic or antagonistic combinations in Combenefit when compared to SynergyFinder. We strongly recommend using multiple reference models and reporting complete data analysis for synergy claiming in combination studies.

Gemcitabine-loaded Folic Acid Tagged Liposomes: Improved Pharmacokinetic and Biodistribution Profile

BACKGROUND

Gemcitabine (GEM) is found effective in the treatment of many solid tumors. However, its use is restricted due to its small circulation half-life, fast metabolism and low capacity for selective tumor uptake. Folate receptors (FRs) have been recognized as cellular surface markers, which can be used for cancer targeting. PEGylated liposomes decorated with folic acid have been investigated for several anticancer agents not only to extend plasma half-life but also for tumor targeting via folic acid receptors which overexpressed on tumor cell surface.

OBJECTIVE

Therefore, the objective of the present study was to prepare GEM-loaded folic acid tagged liposomes to improve the pharmacokinetics and tumor distribution of GEM.

METHODS

The blank folate-targeted liposomes composed of HSPC/DSPE-mPEG2000/DSPE-mPEG-Folic acid were prepared first by thin film hydration technique. GEM was then loaded into liposomes by remote loading technique. The optimized liposomal formulations were evaluated in vitro for GEM release using dialysis technique, HeLa cell uptake using FACS technique, and cytotoxicity using MTT dye reduction assay. The comparative in vivo pharmacokinetic and biodistribution characteristics of radiolabeled (99mTc-labeled) plain GEM solution, and all liposomal formulations (conventional:CLs; stealth: SLs; folate targeted: FTLs) were evaluated in mice model.

RESULTS

GEM-loaded FTLs showed sustained release profile, efficient uptake by HeLa cells and greater cytotoxicity. Further, FTLs displayed significantly improved pharmacokinetics, and biodistribution profile of loaded GEM.

CONCLUSION

In conclusion, the developed GEM-loaded folic acid receptor-targeted liposomal formulation could be a promising and potential alternative formulation for further development.

Cigarette smoke and non-neuronal cholinergic system in the airway epithelium of COPD patients

Acetylcholine (ACh), synthesized by Choline Acetyl-Transferase (ChAT), exerts its physiological effects via mAChRM3 in epithelial cells. We hypothesized that cigarette smoke affects ChAT, ACh, and mAChRM3 expression in the airways from COPD patients promoting airway disease. ChAT, ACh, and mAChRM3 were assessed: "ex vivo" in the epithelium from central and distal airways of COPD patients, Healthy Smoker (S) and Healthy Subjects (C), and "in vitro" in bronchial epithelial cells stimulated with cigarette smoke extract (CSE). In central airways, mAChRM3, ChAT, and ACh immunoreactivity was significantly higher in the epithelium from S and COPD than in C subjects. mAChRM3, ChAT, and ACh score of immunoreactivity was high in the metaplastia area of COPD patients. mAChRM3/ChAT and ACh/ChAT co-localization of immunoreactivity was observed in the bronchial epithelium from COPD. In vitro, CSE stimulation significantly increased mAChRM3, ChAT, and ACh expression and mAChRM3/ChAT and ACh/ChAT co-localization in 16HBE and NHBE, and increased 16HBE proliferation. Cigarette smoke modifies the levels of mAChMR3, ChAT expression, and ACh production in bronchial epithelial cells from COPD patients. Non-neuronal components of cholinergic system may have a role in the mechanism of bronchial epithelial cell proliferation, promoting alteration of normal tissue, and of related pulmonary functions.

Electrophilic derivatives of omega-3 fatty acids counteract lung cancer cell growth

PURPOSE

17-oxo-DHA is an electrophilic keto-derivative of the omega-3 fatty acid docosahexaenoic acid (DHA) endogenously generated by cyclooxygenase-2 and a cellular dehydrogenase. 17-oxo-DHA displays anti-inflammatory and cytoprotective actions. DHA, alone or in combination with standard chemotherapy, displays antitumor activity. However, the effects of electrophilic keto-derivatives of DHA on cancer growth have never been evaluated. We investigated whether 17-oxo-DHA, alone or in combination with gemcitabine, displayed antitumor effects. Furthermore, we evaluated whether the enzyme 15-prostaglandin dehydrogenase (15-PGDH) was required for transducing the antitumor effects of DHA.

METHODS

A panel of five histologically different human non-small cell lung cancer (NSCLC) cell lines was used. Cells were treated with 17-oxo-DHA and gemcitabine, alone or in combination, and apoptosis, proliferation, Fas and FasL expression (mRNA and protein) and active caspase-3/7 and -8 were assessed. Furthermore, an inhibitor of 15-PGDH was used to test the involvement of this enzyme in mediating the antitumor effects of DHA.

RESULTS

17-oxo-DHA (50 µM, 72 h) significantly reduced proliferation, increased cell apoptosis, Fas and FasL expression as well as active caspase-8 and -3/7. When 17-oxo-DHA was given in combination with gemcitabine, stronger effects were observed compared to gemcitabine alone. The enzyme 15-PGDH was required for DHA to promote its full anti-apoptotic effect suggesting that enzymatically generated keto-derivatives of DHA mediate its antitumor actions.

CONCLUSIONS

Data herein provided, demonstrate that 17-oxo-DHA displays antitumor effects in NSCLC cell lines. Of note, the combination of 17-oxo-DHA plus gemcitabine, resulted in stronger anticancer effects compared to gemcitabine alone.

Apoptosis and Compensatory Proliferation Signaling Are Coupled by CrkI-Containing Microvesicles

Apoptosis has been implicated in compensatory proliferation signaling (CPS), whereby dying cells induce proliferation in neighboring cells as a means to restore homeostasis. The nature of signaling between apoptotic cells and their neighboring cells remains largely unknown. Here we show that a fraction of apoptotic cells produce and release CrkI-containing microvesicles (distinct from exosomes and apoptotic bodies), which induce proliferation in neighboring cells upon contact. We provide visual evidence of CPS by videomicroscopy. We show that purified vesicles in vitro and in vivo are sufficient to stimulate proliferation in other cells. Our data demonstrate that CrkI inactivation by ExoT bacterial toxin or by mutagenesis blocks vesicle formation in apoptotic cells and inhibits CPS, thus uncoupling apoptosis from CPS. We further show that c-Jun amino-terminal kinase (JNK) plays a pivotal role in mediating vesicle-induced CPS in recipient cells. CPS could have important ramifications in diseases that involve apoptotic cell death.

Effects of electrical stimulation on cell proliferation and apoptosis

The application of exogenous electrical stimulation (ES) to cells in order to manipulate cell apoptosis and proliferation has been widely investigated as a possible method of treatment in a number of diseases. Alteration of the transmembrane potential of cells via ES can affect various intracellular signaling pathways which are involved in the regulation of cellular function. Controversially, several types of ES have proved to be effective in both inhibiting or inducing apoptosis, as well as increasing proliferation. However, the mechanisms through which ES achieves this remain fairly unclear. The aim of this review was to comprehensively summarize current findings from in vitro and in vivo studies on the effects of different types of ES on cell apoptosis and proliferation, highlighting the possible mechanisms through which ES induced these effects and define the optimum parameters at which ES can be used. Through this we hope to provide a greater insight into how future studies can most effectively use ES at the clinical trial stage.

14-3-3σ regulation of and interaction with YAP1 in acquired gemcitabine resistance via promoting ribonucleotide reductase expression

Gemcitabine is an important anticancer therapeutics approved for treatment of several human cancers including locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC). Its clinical effectiveness, however, is hindered by existence of intrinsic and development of acquired resistances. Previously, it was found that 14-3-3σ expression associates with poor clinical outcome of PDAC patients. It was also found that 14-3-3σ expression is up-regulated in gemcitabine resistant PDAC cells and contributes to the acquired gemcitabine resistance. In this study, we investigated the molecular mechanism of 14-3-3σ function in gemcitabine resistance and found that 14-3-3σ up-regulates YAP1 expression and then binds to YAP1 to inhibit gemcitabine-induced caspase 8 activation and apoptosis. 14-3-3σ association with YAP1 up-regulates the expression of ribonucleotide reductase M1 and M2, which may mediate 14-3-3σ/YAP1 function in the acquired gemcitabine resistance. These findings suggest a possible role of YAP1 signaling in gemcitabine resistance.

Gemcitabine sensitizes lung cancer cells to Fas/FasL system-mediated killing

Gemcitabine is a chemotherapy agent commonly used in the treatment of non-small cell lung cancer (NSCLC) that has been demonstrated to induce apoptosis in NSCLC cells by increasing functionally active Fas expression. The aim of this study was to evaluate the Fas/Fas ligand (FasL) system involvement in gemcitabine-induced lung cancer cell killing. NSCLC H292 cells were cultured in the presence or absence of gemcitabine. FasL mRNA and protein were evaluated by real-time PCR, and by Western blot and flow cytometry, respectively. Apoptosis of FasL-expressing cells was evaluated by flow cytometry, and caspase-8 and caspase-3 activation by Western blot and a colorimetric assay. Cytotoxicity of lymphokine-activated killer (LAK) cells and malignant pleural fluid lymphocytes against H292 cells was analysed in the presence or absence of the neutralizing anti-Fas ZB4 antibody, by flow cytometry. Gemcitabine increased FasL mRNA and total protein expression, the percentage of H292 cells bearing membrane-bound FasL (mFasL) and of mFasL-positive apoptotic H292 cells, as well as caspase-8 and caspase-3 cleavage. Moreover, gemcitabine increased CH11-induced caspase-8 and caspase-3 cleavage and proteolytic activity. Cytotoxicity of LAK cells and pleural fluid lymphocytes was increased against gemcitabine-treated H292 cells and was partially inhibited by ZB4 antibody. These results demonstrate that gemcitabine: (i) induces up-regulation of FasL in lung cancer cells triggering cell apoptosis via an autocrine/paracrine loop; (ii) induces a Fas-dependent apoptosis mediated by caspase-8 and caspase-3 activation; (iii) enhances the sensitivity of lung cancer cells to cytotoxic activity of LAK cells and malignant pleural fluid lymphocytes, partially via Fas/FasL pathway. Our data strongly suggest an active involvement of the Fas/FasL system in gemcitabine-induced lung cancer cell killing.

Clinical efficacy of CyberKnife combined with chemotherapy and hyperthermia for advanced non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is responsible for at least 80% of all lung tumors and has a poor prognosis, since 75% of NSCLCs are first diagnosed at an advanced stage. This study was conducted to evaluate the therapeutic efficacy of CyberKnife in combination with chemotherapy and hyperthermia for selected patients with advanced non-small cell lung cancer (NSCLC). Clinical charts, imaging and pathology reports of patients with advanced NSCLC who underwent CyberKnife therapy in our Tumor Therapy Center were retrospectively reviewed. Clinical efficacy was evaluated for local control, Karnofsky performance status scale (KPS) and toxicity analysis. A total of 119 patients with 136 target areas were evaluated. A prescribed dose of 24-51 Gy to the gross tumor volume was delivered in 3-6 fractions. The median prescription dose was 35 Gy (mean, 34.73±4.80 Gy), with an average of five fractions. Patients, who voluntarily participated in the study, were assigned to one of three groups, which were as follows: CyberKnife therapy alone, CyberKnife combined with chemotherapy and CyberKnife combined with chemotherapy and hyperthermia. The median follow-up period was 6 months and curative efficiencies were 62.16, 71.79 and 90.70%, respectively, as determined by radiographic and clinical re-examinations. Patients treated by CyberKnife combined with chemotherapy and hyperthermia achieved optimal improvement in the aspect of KPS, which was statistically different compared to the other two groups (P<0.05). In conclusion, our results indicated that CyberKnife combined with chemotherapy and hyperthermia achieved favorable short-term outcomes and may be a more viable option for patients with advanced NSCLC. However, further investigations are required to evaluate long-term outcomes.

The C-terminal region of Bfl-1 sensitizes non-small cell lung cancer to gemcitabine-induced apoptosis by suppressing NF-κB activity and down-regulating Bfl-1

Gemcitabine is used to treat several cancers including lung cancer. However, tumor cells often escape gemcitabine-induced cell death via various mechanisms, which include modulating bcl-2 family members and NF-κB activation. We previously reported that the C-terminal region of Bfl-1 fused with GFP (BC) is sufficient to induce apoptosis in 293T cells. In the present study, we investigated the anti-tumor effect of combined BC gene therapy and gemcitabine chemotherapy in vitro and in vivo using non-small cell lung cancer cell lines and a xenograft model. Cell lines were resistant to low dose gemcitabine (4-40 ng/ml), which induced NF-κB activation and concomitant up-regulation of Bfl-1 (an NF-κB-regulated anti-apoptotic protein). BC induced the apoptosis of A549 and H157 cells with caspase-3 activation. Furthermore, co-treatment with BC and low dose gemcitabine synergistically and efficiently induced mitochondria-mediated apoptosis in these cells. When administered alone or with low dose gemcitabine, BC suppressed NF-κB activity, inhibited the nuclear translocation of p65/relA, and down-regulated Bfl-1 expression. Furthermore, direct suppression of Bfl-1 by RNA interference sensitized cells to gemcitabine-induced cell death, suggesting that Bfl-1 importantly regulates lung cancer cell sensitivity to gemcitabine. BC and gemcitabine co-treatment also showed a strong anti-tumor effect in a nude mouse/A549 xenograft model. These results suggest that lung cancer cells become resistant to gemcitabine via NF-κB activation and the subsequent overexpression of Bfl-1, and that BC, which has both pro-apoptotic and NF-κB inhibitory effects, could be harnessed as a gene therapy to complement gemcitabine chemotherapy in non-small cell lung cancer.

Tamoxifen enhances therapeutic effects of gemcitabine on cholangiocarcinoma tumorigenesis

Cholangiocarcinoma is a highly malignant tumor with limited therapeutic options. We have previously reported that tamoxifen (TMX) induces apoptosis of cholangiocarcinoma cells and reduces cholangiocarcinoma tumorigenesis in mice. In the present studies, we determined the effect of combination therapy of TMX and gemcitabine (GMT), another chemotherapeutical reagent for many cancers, on cholangiocarcinoma tumorigenesis and investigated the responsible mechanisms. GMT inhibited cell growth and induced apoptosis of cholangiocarcinoma cells in a concentration-dependent manner. TMX enhanced GMT-induced apoptosis of cholangiocarcinoma cells. Consistently, GMT (15 mg/kg) inhibited cholangiocarcinoma tumorigenesis in nude mice by 50%. TMX (15 mg/kg) enhanced the inhibitory effect of GMT on tumorigenesis by 33%. The inhibition of tumor growth correlated with enhanced apoptosis in tumor tissues. To elucidate the mechanisms underlying the additive effects of TMX on GMT-induced apoptosis, we determined the activation of caspases in cholangiocarcinoma cells exposed to GMT, TMX, or both. Activation of caspases 9 and 3, as well as cytochrome c release to the cytosol, was demonstrated in cells exposed to both reagents. In contrast, TMX activated caspase 2, whereas GMT had no effect. Inhibition of caspase 2 activation decreased TMX-, but not GMT-, induced activation of caspase 3 and apoptosis of cholangiocarcinoma cells. Similarly, activation of caspase 2 was found in tumors from TMX-treated mice, but not GMT-treated mice. Therefore, the enhanced effect of TMX on GMT-induced cholangiocarcinoma cell death is partially mediated by activation of caspase 2. TMX and GMT both induce apoptosis and inhibit cholangiocarcinoma tumorigenesis, which may be attributed to the activation of distinct apoptosis signals by TMX and GMT. Our studies provide in vivo evidence and molecular insight to support the use of TMX and GMT in combination as an effective therapy for cholangiocarcinoma.

Gemcitabine-based chemogene therapy for pancreatic cancer using Ad-dCK::UMK GDEPT and TS/RR siRNA strategies

Gemcitabine is a first-line agent for advanced pancreatic cancer therapy. However, its efficacy is often limited by its poor intracellular metabolism and chemoresistance. To exert its antitumor activity, gemcitabine requires to be converted to its active triphosphate form. Thus, our aim was to improve gemcitabine activation using gene-directed enzyme prodrug therapy based on gemcitabine association with the deoxycytidine kinase::uridine monophosphate kinase fusion gene (dCK::UMK) and small interference RNA directed against ribonucleotide reductase (RRM2) and thymidylate synthase (TS). In vitro, cytotoxicity was assessed by 3-[4,5-dimethylthiazol-2-yl]-3,5-diphenyl tetrazolium bromide and [(3)H]thymidine assays. Apoptosis-related gene expression and activity were analyzed by reverse transcription-polymerase chain reaction, Western blot, and ELISA. For in vivo studies, the treatment efficacy was evaluated on subcutaneous and orthotopic pancreatic tumor models. Our data indicated that cell exposure to gemcitabine induced a down-regulation of dCK expression and up-regulation of TS and RR expression in Panc1-resistant cells when compared with BxPc3- and HA-hpc2-sensitive cells. The combination of TS/RRM2 small interference RNA with Ad-dCK::UMK induced a 40-fold decrease of gemcitabine IC(50) in Panc1 cells. This strong sensitization was associated to apoptosis induction with a remarkable increase in TRAIL expression and a diminution of gemcitabine-induced nuclear factor-kappaB activity. In vivo, the gemcitabine-based tritherapy strongly reduced tumor volumes and significantly prolonged mice survival. Moreover, we observed an obvious increase of apoptosis and decrease of cell proliferation in tumors receiving the tritherapy regimens. Together, these findings suggest that simultaneous TS/RRM2-gene silencing and dCK::UMK gene overexpression markedly improved gemcitabine's therapeutic activity. Clearly, this combined strategy warrants further investigation.

The role of apoptotic cell death in the radiosensitising effect of gemcitabine

Background:

The aim of this study was to evaluate the radiosensitising effect of gemcitabine, in terms of cell-cycle progression, induction of apoptosis, and to investigate the molecular events regulating apoptosis.

Methods:

Tumour cells were treated with gemcitabine, radiation, or the combination. 0–72 h after treatment, cells were collected for cell-cycle analysis and apoptosis determination. Caspase 8 and 9, Bid and tBid expression were determined by western blot. The mitochondrial membrane potential was determined using flow cytometry. An RT²Profiler PCR Array for human apoptotic genes was performed after the combination or TRAIL treatment.

Results:

Gemcitabine and radiation resulted in an early S-phase block immediately after treatment, after which the cells moved synchronously through the cell cycle. When cell-cycle distribution returned to pre-treatment levels, an increased induction of apoptosis was observed with activation of caspase 8 and 9 and a reduction of the mitochondrial membrane potential. Gene expression after treatment with radiosensitising conditions was comparable with expression after the TRAIL treatment.

Conclusion:

A role for the cell-cycle perturbations and the induction of apoptosis could be attributed to the radiosensitising effect of gemcitabine. Apoptosis induction was comparable with the apoptotic pathway observed after the TRAIL treatment, that is the involvement of the extrinsic apoptosis pathway.

Gemcitabine-induced apoptosis in 5637 cell line: an in-vitro model for high-risk superficial bladder cancer

Recent data suggest that new treatment options for superficial bladder cancer are necessary, owing to the high recurrence rate after conventional treatment, especially in T1G3 and Bacillus Calmette-Guerin-refractory patients. Phase I and II studies have demonstrated that gemcitabine may represent a candidate for intravesical therapy in superficial bladder cancer. Despite clinical trials, the in-vitro cytotoxic and proapoptotic effects of gemcitabine have been poorly investigated. In the present study, we investigated how gemcitabine affects apoptosis in bladder cancer cell line 5637, which has the same molecular features of high-risk superficial bladder cancer. Apoptosis was evaluated by DNA fragmentation, flow cytometry and caspase activation. bcl-2, bcl-X, bax, survivin and fas gene expression were also evaluated by reverse-transcriptase polymerase chain reaction. Nuclear factor-kappa B activation was assessed by immunofluorescence. Gemcitabine induced apoptosis in 5637 cells in a time-dependent manner, with activation of caspase-3, -8 and -9. Expression of bcl-2, bax, survivin and bcl-X was not affected by treatment, whereas fas strongly increased after 24 h of treatment. After treatment, we failed to find any nuclear localization of nuclear factor-kappa B. As gemcitabine-induced apoptosis involves fas upregulation, these results may encourage the investigation of intravesical gemcitabine in fas-negative bladder tumors. Furthermore, as nuclear factor-kappa B activation by cisplatin, doxorubicin and adriamycin may result in enhanced proliferation, migration, immortality and inhibition of apoptosis, the observation that gemcitabine does not activate nuclear factor-kappa B may have implications in intravesical therapy of high-risk superficial bladder cancer.

Role of prostaglandin E2 in the invasiveness, growth and protection of cancer cells in malignant pleuritis

The recurrence of pleural effusions is a common event in a variety of neoplastic diseases. The objective of this study was to identify the mechanisms promoting the homing and growth of cancer cells within the pleural space. A cancer cell line recovered from malignant pleural fluids (lung adenocarcinoma cell line) that constitutively expresses cyclooxygenase 2 (COX-2) and all types of prostaglandin receptors was studied. It was first demonstrated using a matrigel system, that malignant pleural fluids increase the invasiveness of adenocarcinoma cells more than congestive heart failure (CHF) pleural fluids. Moreover, exposure to exudative malignant, but not to CHF pleural fluids, increased the mRNA (measured by real-time polymerase chain reaction (PCR)) and protein expression of COX-2 (measured by Western blot), as well as the activation and nuclear translocation of nuclear factor kappaB (NFkappaB) in cancer cells. These events are all actively regulated by prostaglandin E2 (PGE2), since the addition of synthetic PGE2 to cancer cells and the depletion of PGE2 from malignant pleural fluids or the inhibition of COX-2 activity significantly increased and reduced these phenomena, respectively. Moreover, malignant pleural effusions and synthetic PGE2 increased the long-term proliferation of cancer cells and reverted the impairment in long-term proliferation due to talc exposure. This study demonstrates that PGE2 present in malignant effusions contributes to cancer expansion and may protect cancer cells by anti-proliferative effects induced by talc.

Dipeptidyl peptidase II and leukocyte cell death

Dipeptidyl peptidase (DPP) II (E.C. 3.4.14.2) is an intracellular protease that releases, preferably at acidic pH, N-terminal dipeptides from oligopeptides with Pro or Ala in the penultimate position. The natural substrates and the physiological role of DPPII remain unclear. The aim of the present study was to investigate the involvement of DPPII activity in different forms of cell death (apoptosis, necrosis and autophagy) in human leukocytes. We determined specific DPP activities in leukocytes. Compared to other subpopulations of peripheral blood mononuclear cells (PBMC), we observed relatively high DPPII specific activity in monocytic cells, opening new perspectives for further investigation of the DPPII functions. A second intriguing finding was that DPPII specific activity increased during necrosis, whereas induction of apoptosis or autophagy did not affect any of the dipeptidyl peptidase activities. Finally, we showed that inhibition of DPPII (>90%) using the in vitro applicable, highly potent (K(i) of 0.082+/-0.048 nM) and selective DPPII inhibitor UAMC00039, did not induce any form of cell death in leukocytes. These data are of importance for a more precise interpretation of the in vitro and in vivo effects of other dipeptidyl peptidase inhibitors.

Interaction between gemcitabine and topotecan in human non-small-cell lung cancer cells: effects on cell survival, cell cycle and pharmacogenetic profile

The pyrimidine analogue gemcitabine is an established effective agent in the treatment of non-small-cell lung cancer (NSCLC). The present study investigates whether gemcitabine would be synergistic with the topoisomerase I inhibitor topotecan against the NSCLC A549 and Calu-6 cells. Cells were treated with gemcitabine and topotecan for 1 h and the type of drug interaction was assessed using the combination index (CI). Cell cycle alterations were analysed by flow cytometry, while apoptosis was examined by the occurrence of DNA internucleosomal fragmentation, nuclear condensation and caspase-3 activation. Moreover, the possible involvement of the PI3K-Akt signalling pathway was investigated by the measurement of Akt phosphorylation. Finally, quantitative, real-time PCR (QRT-PCR) was used to study modulation of the gemcitabine-activating enzyme deoxycytidine kinase (dCK) and the cellular target enzyme ribonucleotide reductase (RR). In results, it was found that simultaneous and sequential topotecan → gemcitabine treatments were synergistic, while the reverse sequence was antagonistic in both cell lines. DNA fragmentation, nuclear condensation and enhanced caspase-3 activity demonstrated that the drug combination markedly increased apoptosis in comparison with either single agent, while cell cycle analysis showed that topotecan increased cells in S phase. Furthermore, topotecan treatment significantly decreased the amount of the activated form of Akt, and enhanced the expression of dCK (+155.0 and +115.3% in A549 and Calu-6 cells, respectively), potentially facilitating gemcitabine activity. In conclusion, these results indicate that the combination of gemcitabine and topotecan displays schedule-dependent activity in vitro against NSCLC cells. The gemcitabine → topotecan sequence is antagonistic while drug synergism is obtained with the simultaneous and the sequential topotecan → gemcitabine combinations, which are associated with induction of decreased Akt phosphorylation and increased dCK expression.

Extracellular signal-regulated kinase activation and Bcl-2 downregulation mediate apoptosis after gemcitabine treatment partly via a p53-independent pathway

Gemcitabine is a promising compound for the treatment of human lung cancer. Although apoptosis has been shown to play a role in certain cell types with gemcitabine, the steps leading to cell death after the drug-target interaction are not well understood. We studied the molecular mechanisms of gemcitabine-induced apoptosis and determined the role of p53 function on the cytotoxic effects of gemcitabine in human nonsmall cell lung cancer (NSCLC) H1299 and H1299/p53 cells. Here, we found that gemcitabine induced an apoptotic cell death via a Bcl-2-dependent caspase-9 activation pathway. Moreover, phosphorylated activation of extracellular signal-regulated kinase (ERK) was observed upon gemcitabine treatment. Genetical or pharmacological inhibition of ERK activation markedly blocked gemcitabine-induced cell death. Furthermore, inactivation of Akt was also involved in this event. Taken together, our observations indicate that ERK activation and Akt inactivation mediated gemcitabine-induced apoptosis independently of p53 in human NSCLC H1299 cells.

External beam radiation of tumors alters phenotype of tumor cells to render them susceptible to vaccine-mediated T-cell killing

Local radiation is an established therapy for human tumors. Radiation also has been shown to alter the phenotype of target tissue, including gene products that may make tumor cells more susceptible to T-cell-mediated immune attack. We demonstrate a biological synergy between local radiation of tumor and active vaccine therapy. The model used consisted of mice transgenic for human carcinoembryonic antigen (CEA) and a murine carcinoma cell line transfected with CEA. The vaccine regimen consisted of a prime and boost strategy using vaccinia and avipox recombinants expressing CEA and three T-cell costimulatory molecules. One dose of 8-Gy radiation to tumor induced up-regulation of the death receptor Fas in situ for up to 11 days. However, neither radiation at this dose nor vaccine therapy was capable of inhibiting growth of 8-day established tumor. When vaccine therapy and local radiation of tumor were used in combination, dramatic and significant cures were achieved. This was mediated by the engagement of the Fas/Fas ligand pathway because Ag-bearing tumor cells expressing dominant-negative Fas were not susceptible to this combination therapy. Following the combination of vaccine and local radiation, tumors demonstrated a massive infiltration of T cells not seen with either modality alone. Mice cured of tumors demonstrated CD4(+) and CD8(+) T-cell responses specific for CEA but also revealed the induction of high levels of T-cell responses to two other antigens (gp70 and p53) overexpressed in tumor, indicating the presence of a consequential antigen cascade. Thus, these studies demonstrate a new paradigm for the use of local tumor irradiation in combination with active specific vaccine therapy to elicit durable antitumor responses of established tumors.

An anti-GD2 monoclonal antibody enhances apoptotic effects of anti-cancer drugs against small cell lung cancer cells via JNK (c-Jun terminal kinase) activation

Small cell lung cancer (SCLC) cell lines specifically express ganglioside GD2, and anti-GD2 monoclonal antibodies (mAbs) caused suppression of cell growth and induced apoptosis of SCLC cells with single use. Here, enhancement of the cytotoxic effects of various anti-cancer drugs with an anti-GD2 mAb was demonstrated. The cytotoxicity of all six drugs examined was markedly enhanced, i.e. 2.4 - 7.8-fold increase of cell sensitivity in terms of IC(50). In particular, the combination of cisplatin (CDDP) with an anti-GD2 mAb resulted in prominent enhancement of cytotoxicity even in low - moderate GD2-expressing lines. The anti-GD2 mAb induced weak activation of c-Jun terminal kinase (JNK) in SCLC cells, and all anti-cancer drugs also induced its activation to various degrees. When CDDP and an anti-GD2 mAb were used together, significantly stronger JNK activation was observed corresponding to the cytotoxic effects, suggesting that synergistic phosphorylation of JNK with two reagents induced prominent apoptosis. The essential role of JNK in the induction of SCLC apoptosis with CDDP and anti-GD2 mAb was confirmed by experiments with a JNK inhibitor, curcumin. These results suggest that anti-GD2 mAbs would be very efficient in combination with anti-cancer drugs, both to achieve SCLC-specific cytotoxicity and to enhance its magnitude.

Determinants of resistance to 2',2'-difluorodeoxycytidine (gemcitabine)

The inherent or induced resistance of tumors to cytostatic agents is a major clinical problem. In this review, we summarize the pre-clinical mechanisms of acquired and inherent resistance to the fluorinated deoxycytidine analog gemcitabine (2',2'-difluorodeoxycytidine, dFdC, Gemzar((R))), which has proven activity in non-small cell lung carcinoma, pancreatic and bladder cancer. Extensive research has been performed to elucidate the complex mechanism of action of this relatively new drug. Gemcitabine requires phosphorylation to mono-, di- and triphosphates to be active. Similar to the structurally and functionally related deoxycytidine analog ara-C, the first, crucial step in phosphorylation is catalyzed by deoxycytidine kinase (dCK). However, in contrast to ara-C, gemcitabine has multiple intracellular targets; up- or down-regulation of these targets may confer resistance to this drug. Resistance is associated with altered activities of enzymes involved in the metabolism of the drug, of target enzymes, and of enzymes involved in programmed cell death. However, the only strong correlations with gemcitabine sensitivity are dCK activity and dFdCTP pools, with a potential important role for ribonucleotide reductase.