Inhibition of nuclear factor kappaB chemosensitizes non-small cell lung cancer through cytochrome c release and caspase activation

Serum and Glucocorticoid-Inducible Kinase 1 (SGK1) in NSCLC Therapy

Non-small cell lung cancer (NSCLC) remains the most prevalent and one of the deadliest cancers worldwide. Despite recent success, there is still an urgent need for new therapeutic strategies. It is also becoming increasingly evident that combinatorial approaches are more effective than single modality treatments. This review proposes that the serum and glucocorticoid-inducible kinase 1 (SGK1) may represent an attractive target for therapy of NSCLC. Although ubiquitously expressed, SGK1 deletion in mice causes only mild defects of ion physiology. The frequent overexpression of SGK1 in tumors is likely stress-induced and provides a therapeutic window to spare normal tissues. SGK1 appears to promote oncogenic signaling aimed at preserving the survival and fitness of cancer cells. Most importantly, recent investigations have revealed the ability of SGK1 to skew immune-cell differentiation toward pro-tumorigenic phenotypes. Future studies are needed to fully evaluate the potential of SGK1 as a therapeutic target in combinatorial treatments of NSCLC. However, based on what is currently known, SGK1 inactivation can result in anti-oncogenic effects both on tumor cells and on the immune microenvironment. A first generation of small molecules to inactivate SGK1 has already been already produced.

NF-κB inhibitors in treatment and prevention of lung cancer

Intracellular signalling pathways have provided excellent resource for drug development particularly in the development of cancer therapeutics. A wide variety of malignancies common in human exhibit aberrant NF-κB constitutive expression which results in tumorigenic processes and cancer survival in a variety of solid tumour, including pancreatic cancer, lung, cervical, prostate, breast and gastric carcinoma. Numerous evidences indicate that NF-κB signalling mechanism is mainly involved in the progression of several cancers which may intensify an enhanced knowledge on its role in disease particularly lung tumorigenesis. This has led to tremendous research in designing a variety of NF-κB antagonists with enhanced clinical applications through different approaches the most common being suppression of IκB kinase (IKK) beta activity. Many NF-κB inhibitors for lung cancer are now under clinical trials. Preliminary results of clinical trials for several of these agents include small-molecule inhibitors and monoclonal antibodies. A few combinatorial treatment therapies are currently under investigation in the clinics and have shown promise, particularly NF-κB inhibition associated with lung cancer.

The Fire Within: NF-κB Involvement in Non-Small Cell Lung Cancer

Thirty-four years since its discovery, NF-κB remains a transcription factor with great potential for cancer therapy. However, NF-κB-targeted therapies have yet to find a way to be clinically translatable. Here, we focus exclusively on the role of NF-κB in non-small cell lung cancer (NSCLC) and discuss its contributing effect on cancer hallmarks such as inflammation, proliferation, survival, apoptosis, angiogenesis, epithelial-mesenchymal transition, metastasis, stemness, metabolism, and therapy resistance. In addition, we present our current knowledge of the clinical significance of NF-κB and its involvement in the treatment of patients with NSCLC with chemotherapy, targeted therapies, and immunotherapy.

Aqueous extract of Sapindus mukorossi induced cell death of A549 cells and exhibited antitumor property in vivo

Sapindus mukorossi is a deciduous plant and has recently been recognized to have anticancer property. In the present study, we discovered that S. mukorossi leaf and stem aqueous extract (SaM) contained two polysaccharides mainly made of myo-inositol, galactose, glucose, and fructose and the aim of this study was to investigate the antitumor property the aqueous extract SaM. In vitro treatment of SaM diminished proliferative potential of lung adenocarcinomic cells and induced intracellular oxidative stress, as well as necrotic cell death. Moreover, exposure to SaM attenuated cell migration, demonstrating the effectiveness at reducing invasive property of malignant lung cells. Gene and protein expression studies indicated that SaM treatment altered the expression of proliferation/survival modulator NF-κB, tumor growth modulator ERK2, metastasis-associated molecules MMP9/12, and tumor suppressor p53 in A549 cells. Using model animals bearing Lewis lung cancer cell LL/2, we demonstrated that SaM was antitumoral and did not induce any undesired organ damage, immunotoxicity, and off-target inflammation. This work, to our knowledge, is the first study documents the antitumor bioactivity of aqueous extract riched in polysaccharides from S. mukorossi and provides insights into the potential pharmacological application of SaM as antitumor agent against lung cancer.

Cancer cell growth inhibitory effect of bee venom via increase of death receptor 3 expression and inactivation of NF-kappa B in NSCLC cells

Our previous findings have demonstrated that bee venom (BV) has anti-cancer activity in several cancer cells. However, the effects of BV on lung cancer cell growth have not been reported. Cell viability was determined with trypan blue uptake, soft agar formation as well as DAPI and TUNEL assay. Cell death related protein expression was determined with Western blotting. An EMSA was used for nuclear factor kappaB (NF-κB) activity assay. BV (1–5 μg/mL) inhibited growth of lung cancer cells by induction of apoptosis in a dose dependent manner in lung cancer cell lines A549 and NCI-H460. Consistent with apoptotic cell death, expression of DR3 and DR6 was significantly increased. However, deletion of DRs by small interfering RNA significantly reversed BV induced cell growth inhibitory effects. Expression of pro-apoptotic proteins (caspase-3 and Bax) was concomitantly increased, but the NF-κB activity and expression of Bcl-2 were inhibited. A combination treatment of tumor necrosis factor (TNF)-like weak inducer of apoptosis, TNF-related apoptosis-inducing ligand, docetaxel and cisplatin, with BV synergistically inhibited both A549 and NCI-H460 lung cancer cell growth with further down regulation of NF-κB activity. These results show that BV induces apoptotic cell death in lung cancer cells through the enhancement of DR3 expression and inhibition of NF-κB pathway.

Minnelide: a novel therapeutic that promotes apoptosis in non-small cell lung carcinoma in vivo

BACKGROUND

Minnelide, a pro-drug of triptolide, has recently emerged as a potent anticancer agent. The precise mechanisms of its cytotoxic effects remain unclear.

METHODS

Cell viability was studied using CCK8 assay. Cell proliferation was measured real-time on cultured cells using Electric Cell Substrate Impedence Sensing (ECIS). Apoptosis was assayed by Caspase activity on cultured lung cancer cells and TUNEL staining on tissue sections. Expression of pro-survival and anti-apoptotic genes (HSP70, BIRC5, BIRC4, BIRC2, UACA, APAF-1) was estimated by qRTPCR. Effect of Minnelide on proliferative cells in the tissue was estimated by Ki-67 staining of animal tissue sections.

RESULTS

In this study, we investigated in vitro and in vivo antitumor effects of triptolide/Minnelide in non-small cell lung carcinoma (NSCLC). Triptolide/Minnelide exhibited anti-proliferative effects and induced apoptosis in NSCLC cell lines and NSCLC mouse models. Triptolide/Minnelide significantly down-regulated the expression of pro-survival and anti-apoptotic genes (HSP70, BIRC5, BIRC4, BIRC2, UACA) and up-regulated pro-apoptotic APAF-1 gene, in part, via attenuating the NF-κB signaling activity.

CONCLUSION

In conclusion, our results provide supporting mechanistic evidence for Minnelide as a potential in NSCLC.

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.

NF-kappaB in lung cancer, a carcinogenesis mediator and a prevention and therapy target

Lung cancer ranks as the first malignant tumor killer worldwide. Despite the knowledge that carcinogens from tobacco smoke and the environment constitute the main causes of lung cancer, the mechanisms for lung carcinogenesis are still elusive. Cancer development and progression depend on the balance between cell survival and death signals. Common cell survival signaling pathways are activated by carcinogens as well as by inflammatory cytokines, which contribute substantially to cancer development. As a major cell survival signal, nuclear factor-kappaB (NF-kappaB) is involved in multiple steps in carcinogenesis and in cancer cell's resistance to chemo- and radio-therapy. Recent studies with animal models and cell culture systems have established the links between NF-kappaB and lung carcinogenesis, highlighting the significance of targeting NF-kappa signaling pathway for lung cancer treatment and chemoprevention. In this review, we summarize progresses in understanding the NF-kappaB pathway in lung cancer development as well as in modulating NF-kappaB for lung cancer prevention and therapy.

Multigene expression-based predictors for sensitivity to Vorinostat and Velcade in non-small cell lung cancer

The ability to predict the efficacy of molecularly targeted therapies for non-small cell lung cancer (NSCLC) for an individual patient remains problematic. The purpose of this study was to identify, using a refined "coexpression extrapolation (COXEN)" algorithm with a continuous spectrum of drug activity, tumor biomarkers that predict drug sensitivity and therapeutic efficacy in NSCLC to Vorinostat, a histone deacetylase inhibitor, and Velcade, a proteasome inhibitor. Using our refined COXEN algorithm, biomarker prediction models were discovered and trained for Vorinostat and Velcade based on the in vitro drug activity profiles of nine NSCLC cell lines (NCI-9). Independently, a panel of 40 NSCLC cell lines (UVA-40) were treated with Vorinostat or Velcade to obtain 50% growth inhibition values. Genome-wide expression profiles for both the NCI-9 and UVA-40 cell lines were determined using the Affymetrix HG-U133A platform. Modeling generated multigene expression signatures for Vorinostat (45-gene; P = 0.002) and Velcade (15-gene; P = 0.0002), with one overlapping gene (CFLAR). Examination of Vorinostat gene ontogeny revealed a predilection for cellular replication and death, whereas that of Velcade suggested involvement in cellular development and carcinogenesis. Multivariate regression modeling of the refined COXEN scores significantly predicted the activity of combination therapy in NSCLC cells (P = 0.007). Through the refinement of the COXEN algorithm, we provide an in silico method to generate biomarkers that predict tumor sensitivity to molecularly targeted therapies. Use of this refined COXEN method has significant implications for the a priori examination of targeted therapies to more effectively streamline subsequent clinical trial design and cost.

Chemosensitization in non-small cell lung cancer cells by IKK inhibitor occurs via NF-kappaB and mitochondrial cytochrome c cascade

In this study, we demonstrated with mechanistic evidence that parthenolide, a sesquiterpene lactone, could antagonize paclitaxel-mediated NF-κB nuclear translocation and activation by selectively targeting I-κB kinase (IKK) activity. We also found that parthenolide could target IKK activity and then inhibit NF-κB; this promoted cytochrome c release and activation of caspases 3 and 9. Inhibition of caspase activity blocked the activation of caspase cascade, implying that the observed synergy was related to caspases 3 and 9 activation of parthenolide. In contrast, paclitaxel individually induced apoptosis via a pathway independent of the mitochondrial cytochrome c cascade. Finally, exposure to parthenolide resulted in the inhibition of several NF-κB transcript anti-apoptotic proteins such as c-IAP1 and Bcl-xl. These data strengthen the rationale for using parthenolide to decrease the apoptotic threshold via caspase-dependent processes for treatment of non-small cell lung cancer with paclitaxel chemoresistance.

Bexarotene: a promising anticancer agent

Retinoids are biologically active derivatives of vitamin A, which play essential roles in embryonic or adult cell behavior modulating cell proliferation, differentiation and apoptosis. The biologic effects of retinoids are mediated by two distinct families of intracellular receptors: retinoid acid receptors (RARs)-α, -β and -γ and retinoid X receptors (RXR)-α, -β and -γ. Bexarotene is a selective RXR agonist, which exerts its effects in blocking cell cycle progression, inducing apoptosis and differentiation, preventing multidrug resistance, and inhibiting angiogenesis and metastasis, making it a promising chemopreventive agent against cancer.

Nuclear factor-kappaB inhibition by parthenolide potentiates the efficacy of Taxol in non-small cell lung cancer in vitro and in vivo

In this study, we have examined the molecular events induced by parthenolide, a sesquiterpene lactone, and explored possible mechanisms of resistance and sensitization of tumor cells to Taxol. We showed that parthenolide could antagonize Taxol-mediated nuclear factor-kappaB (NF-kappaB) nuclear translocation and activation and Bcl-xl up-regulation by selectively targeting I-kappaB kinase activity. In A549 cells, inhibition of nuclear factor-kappaB by parthenolide resulted in activation of the mitochondrial death pathway to promote cytochrome c release and caspase 3 and 9 activation. In contrast, Taxol alone induced apoptosis via a pathway independent of mitochondria cytochrome c cascade. In addition, depletion of Bcl-xl rescued the apoptotic response to Taxol. Moreover, treatment with parthenolide increased the efficacy of the Taxol-induced inhibition of A549 tumor xenografts in mice. This study elucidated the cellular responses induced by parthenolide that decrease the threshold of mitochondria-dependent apoptosis in the treatment of non-small cell lung cancer cells.

Antiapoptotic activity of autocrine interleukin-22 and therapeutic effects of interleukin-22-small interfering RNA on human lung cancer xenografts

PURPOSE

Non-small cell lung carcinoma (NSCLC) is one of most common malignant diseases and usually is resistant against apoptosis-inducing chemotherapy. This study is to explore the antiapoptotic mechanisms of interleukin (IL)-22 in human lung cancer.

EXPERIMENTAL DESIGN

Nineteen cases with stage I to III NSCLC were collected to determine the expression of IL-22. Stable transfection of human IL-22 cDNA into A549 and PG cells and transfection of IL-22-RNA interference (RNAi) into these cancer cell lines were done to reveal the molecular mechanisms of IL-22.

RESULTS

It was found that IL-22 was highly expressed in primary tumor tissue, malignant pleural effusion, and serum of patients with NSCLC. IL-22R1 mRNA was also detected in lung cancer tissues as well as lung cancer cell lines. Overexpression of IL-22 protected lung cancer cell lines from serum starvation-induced and chemotherapeutic drug-induced apoptosis via activation of STAT3 and its downstream antiapoptotic proteins such as Bcl-2 and Bcl-xL and inactivation of extracellular signal-regulated kinase 1/2. Exposure to blocking antibodies against IL-22R1 or transfection with the IL-22-RNAi plasmid in vitro resulted in apoptosis of these lung cancer cells via STAT3 and extracellular signal-regulated kinase 1/2 pathways. Furthermore, an in vivo xenograft study showed that administration of IL-22-RNAi plasmids significantly inhibited the human tumor cell growth in BALB/c nude mice.

CONCLUSIONS

Our study indicates that autocrine production of IL-22 contributes to human lung cancer cell survival and resistance to chemotherapy through the up-regulation of antiapoptotic proteins.

TNF potentiates anticancer activity of bortezomib (Velcade) through reduced expression of proteasome subunits and dysregulation of unfolded protein response

Bortezomib (Velcade) exploits proteasome inhibition as a unique mechanism of anticancer activity. The effectiveness of bortezomib is, however, limited, therefore, the search for therapeutic regimens combining bortezomib with other agents. In the present work we demonstrate enhanced anticancer activity of bortezomib by its combination with tumor necrosis factor (TNF) in the experimental model of C-26 colon carcinoma in mice. This interaction likely relies on the induction of a dysregulated response to ER stress, leading to apoptosis of cancer cells, evidenced by caspase-3 cleavage, p53 accumulation as well as increased SAPK/JNK phosphorylation. ER stress induced by the combination of TNF and bortezomib is corroborated by upregulation of BiP, PDI and calnexin as well as cleavage of caspase-12; however, in contrast to the classic pathway, it is also associated with decreased phosphorylation of eIF2 alpha and prevention of XBP-1 splicing. TNF prevented the upregulation of Hsp27 induced by bortezomib, which may contribute to enhanced ER stress. Moreover, TNF interfered with bortezomib-induced upregulation of distinct subunits of the 26S proteasome. Bortezomib concentration used in this study was not sufficient to prevent TNF from inducing nuclear translocation of p65/RelA; however, the combination of both agents reduced total p65/RelA levels. Combined treatment of tumor-bearing mice with bortezomib and TNF not only inhibited tumor growth but also significantly prolonged animal survival. Therefore, combination of bortezomib with TNF is an attractive option for further clinical studies.

Many faces of NF-kappaB signaling induced by genotoxic stress

The nuclear factor-kappaB (NF-kappaB) family of dimeric transcription factors plays pivotal roles in physiologic and pathologic processes, including immune and inflammatory responses and development and progression of various human cancers. Inactive NF-kappaB dimers normally exist in the cytoplasm in association with inhibitor proteins belonging to the inhibitor of NF-kappaB (IkappaB) family of related proteins. Activation of NF-kappaB involves its release from IkappaB and subsequent nuclear translocation to induce expression of target genes. Intense research effort has revealed many distinct signaling pathways and mechanisms of NF-kappaB activation induced by immune and inflammatory stimuli. These aspects of NF-kappaB biology have been amply reviewed in the literature. However, those that involve DNA-damaging agents are less well understood, and multiple conflicting pathways and mechanisms have been described in the literature. In this review, we summarize the proposed mechanisms of NF-kappaB activation by various DNA-damaging agents, discuss the significance of such activation in the context of cancer treatment, and highlight some of the critical questions that remain to be addressed in future studies.

Novel targeted therapies for non-small cell lung cancer

Targeted therapies will advance the treatment of NSCLC as we improve our understanding of the underlying biology of NSCLC and enhance our ability to clinically target the optimal therapy to an individual's cancer. Ongoing translational research including tissue arrays, genomic, and proteomic studies will help to identify clinically useful biomarkers that will allow further classification of NSCLC and may allow accurate prediction of response to specific chemotherapeutic regimens. Advances in targeted therapy in NSCLC are already yielding exciting results, and promises to become an increasingly important adjunct to surgical management of NSCLC.

Breast cancer metastasis suppressor 1 functions as a corepressor by enhancing histone deacetylase 1-mediated deacetylation of RelA/p65 and promoting apoptosis

The antiapoptotic transcription factor NF-kappaB is constitutively activated in many cancers and is important for cytokine-mediated progression and metastatic movement of tumors. Breast cancer metastasis suppressor 1 (BRMS1) is a metastasis suppressor gene whose mechanisms of action are poorly understood. In this report, we demonstrate that BRMS1 decreases the transactivation potential of RelA/p65 and ameliorates the expression of NF-kappaB-regulated antiapoptotic gene products. BRMS1 immunoprecipitates with the RelA/p65 subunit of NF-kappaB with protein-protein interactions occurring at the C terminus region of the rel homology domain but not at its known transactivation domains. Moreover, BRMS1 functions as a corepressor by promoting binding of HDAC1 to RelA/p65, where it deacetylates lysine K310 on RelA/p65, which suppresses RelA/p65 transcriptional activity. Selective small interfering RNA knockdown of BRMS1 confirms that chromatin-bound BRMS1 is required for deacetylation of RelA/p65, while enhancing chromatin occupancy of HDAC1 onto the NF-kappaB-regulated promoters cIAP2 and Bfl-1/A1. We observed in cells lacking BRMS1 a dramatic increase in cell viability after the loss of attachment from the extracellular matrix. Collectively, these results suggest that BRMS1 suppresses metastasis through its ability to function as a transcriptional corepressor of antiapoptotic genes regulated by NF-kappaB.

Proteasome inhibitors in lung cancer

Proteasome inhibition is a novel therapeutic approach that is being investigated in non-small cell and small cell lung cancer (NSCLC and SCLC). Proteasome inhibition affects a range of intracellular signals and disrupts the levels of numerous proteins, causing apoptosis via multiple pathways. Importantly, malignant cells are more sensitive to proteasome inhibition than normal cells. A number of proteasome inhibitors have demonstrated activity in preclinical studies, both as single agents and in combination with conventional and novel antineoplastic agents. However, only bortezomib, a dipeptide boronic acid analog, has been investigated in lung cancer clinical trials, in which it has shown activity as a single agent and in combination regimens. Numerous preclinical and clinical studies are ongoing in both NSCLC and SCLC. Proteasome inhibition could potentially play a significant role in the future management of these conditions.

Effect of gemcitabine on the expression of apoptosis-related genes in human pancreatic cancer cells

AIM: To investigate the expression of genes involved in the gemcitabine-induced cytotoxicity in human pancreatic cancer cells.

METHODS: A human pancreatic cancer cell line, PANC-1, was cultured. 1 x 10⁴ PANC-1 cells were plated in 96-well microtiter plates. After being incubated for 24 h, gemcitabine was added to the medium at concentrations ranging 2.5 -1 000 mg/L. The AlamarBlue dye method was used for cell growth analysis. DNA fragmentation was quantitatively assayed using a DNA fragmentation enzyme-linked immunosorbent assay (ELISA) kit. PAP and TP53INP1 mRNA expression was determined using the reverse transcription-polymerase chain reaction with semi-quantitative analysis. The expression of GSK-3β and phospho-GSK-3β proteins was examined with Western blot analysis.

RESULTS: The IC₅₀ for the drug after a 48-h exposure to gemcitabine was 16 mg/L. The growth of PANC-1 cells was inhibited by gemcitabine in a concentration-dependent manner (P < 0.0001) and the cell growth was also inhibited throughout the time course (P < 0.0001). The DNA fragmentation rate in the gemcitabine-treated group at 48 h was 44.7 %, whereas it was 25.3 % in the untreated group. The PAP mRNA expression was decreased after being treated with gemcitabine, whereas the TP53INP1 mRNA was increased by the gemcitabine treatment. Western blot analysis showed that phospho- GSK-3β^ser9 was induced by the gemcitabine treatment.

CONCLUSION: Gemcitabine suppresses PANC-1 cell proliferation and induces apoptosis. Apoptosis is considered to be associated with the inhibition of PAP and GSK-3β, and the activation of TP53INP1 and pospho-GSK-3β^ser9.

A selective retinoid X receptor agonist bexarotene (LGD1069, Targretin) prevents and overcomes multidrug resistance in advanced prostate cancer

BACKGROUND

We previously reported that a retinoid X receptor agonist bexarotene prevented and overcame acquired drug resistance in advanced breast cancer and non-small cell lung cancer. The present study was to evaluate the effect of bexarotene on the development of multidrug resistance in advanced prostate cancer.

METHODS

Human prostate cancer cells PC3 were repeatedly treated in culture with paclitaxel, doxorubicin, or cisplatin with or without bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity.

RESULTS

Compared to parental cells, cells treated with a single therapeutic agent was resistant to the therapeutic agent, whereas cells treated with the combination remained chemosensitive. Cells with acquired drug resistance showed increased sensitivity to the cytotoxic agent when treated with the combination. Fluctuation analysis demonstrated that treatment with bexarotene decreased the rate of spontaneous development of drug resistance. These in vitro findings were further confirmed in the PC3 xenograft model.

CONCLUSION

Our results suggest a role of bexarotene in combination with chemotherapeutic agents in prevention and overcoming acquired drug resistance in advanced prostate cancer.

Targeted therapy for non-small cell lung cancer

The overall survival for the treatment of lung cancer patients is less than 15%, despite advances in chemotherapy, radiation therapy, and surgery, due to the inability to control metastatic disease. Over the past three decades, the genetics of lung cancer has been progressively delineated. Small molecule drugs or monoclonal antibodies have been developed that target and inactivate specific cancer-related proteins, such as growth factor receptors or their kinases. This article will review the therapeutic implications of molecular changes associated with non-small cell lung cancer and the status of targeted therapies in its treatment.

Preclinical data with bortezomib in lung cancer

More effective therapies are needed for non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). Proteasome inhibitors are one class of molecularly targeted antineoplastic agents being investigated for these diseases. These agents block the activity of the 26S proteasome, which is responsible for the degradation of the vast majority of intracellular proteins and thus affect multiple signaling pathways within cells. Bortezomib is the first proteasome inhibitor to be evaluated in human studies and is approved for use in multiple myeloma. Bortezomib is now being investigated as a potential treatment for NSCLC and SCLC. Preclinical studies have shown that single-agent bortezomib causes growth inhibition and apoptosis in numerous NSCLC cell lines in vitro and has antitumor activity in vivo. Bortezomib affects the levels of several proteins known to be of significance in lung cancers. Studies of bortezomib in combination with other antitumor agents in vitro and in vivo demonstrate that these combination regimens can offer additive/synergistic effects compared with the single agents. Bortezomib has been investigated in combination with taxanes, gemcitabine, carboplatin, histone deactylase inhibitors, and other molecularly targeted agents in various NSCLC cell lines. The sequence of administration of the agents in preclinical combination regimens in vitro and in vivo has been shown to be of significance; further elucidation of the mechanism of efficacy of bortezomib in lung cancer is required. Numerous clinical studies have been carried out or are ongoing. Bortezomib has the potential to play a significant role in the future management of NSCLC and SCLC.

Tumor-derived p53 mutants induce NF-kappaB2 gene expression

Overexpression of mutant p53 is a common theme in tumors, suggesting a selective pressure for p53 mutation in cancer development and progression. To determine how mutant p53 expression may lead to survival advantage in human cancer cells, we generated stable cell lines expressing p53 mutants p53-R175H, -R273H, and -D281G by use of p53-null human H1299 (lung carcinoma) cells. Compared to vector-transfected cells, H1299 cells expressing mutant p53 showed a survival advantage when treated with etoposide, a common chemotherapeutic agent; however, cells expressing the transactivation-deficient triple mutant p53-D281G (L22Q/W23S) had significantly lower resistance to etoposide. Gene expression profiling of cells expressing transcriptionally active mutant p53 proteins revealed the striking pattern that all three p53 mutants induced expression of approximately 100 genes involved in cell growth, survival, and adhesion. The gene NF-kappaB2 is a prominent member of this group, whose overexpression in H1299 cells also leads to chemoresistance. Treatment of H1299 cells expressing p53-R175H with small interfering RNA specific for NF-kappaB2 made these cells more sensitive to etoposide. We have also observed activation of the NF-kappaB2 pathway in mutant p53-expressing cells. Thus, one possible pathway through which mutants of p53 may induce loss of drug sensitivity is via the NF-kappaB2 pathway.

Increased staining for phospho-Akt, p65/RELA and cIAP-2 in pre-neoplastic human bronchial biopsies

Background

The development of non-small cell lung carcinoma proceeds through a series of well-defined pathological steps before the appearance of invasive lung carcinoma. The molecular changes that correspond with pathology changes are not well defined and identification of the molecular events may provide clues on the progression of intraepithelial neoplasia in the lung, as well as suggest potential targets for chemoprevention. The acquisition of anti-apoptotic signals is critical for the survival of cancer cells but the pathways involved are incompletely characterized in developing intra-epithelial neoplasia (IEN).

Methods

We used immunohistochemistry to determine the presence, relative levels, and localization of proteins that mediate anti-apoptotic pathways in developing human bronchial neoplasia.

Results

Bronchial epithelial protein levels of the phosphorylated (active) form of AKT kinase and the caspase inhibitor cIAP-2 were increased in more advanced grades of bronchial IEN lesions than in normal bronchial epithelium. Additionally, the percentage of biopsies with nuclear localization of p65/RELA in epithelial cells increased with advancing pathology grade, suggesting that NF-κB transcriptional activity was induced more frequently in advanced IEN lesions.

Conclusion

Our results indicate that anti-apoptotic pathways are elevated in bronchial IEN lesions prior to the onset of invasive carcinoma and that targeting these pathways therapeutically may offer promise in prevention of non-small cell lung carcinoma.

Suberoylanilide hydroxamic acid combined with gemcitabine enhances apoptosis in non-small cell lung cancer

BACKGROUND

We have shown that non-small cell lung cancer (NSCLC) is resistant to the histone deacetylase inhibitor (HDI) suberoylanilide hydroxamic acid (SAHA) through upregulation of the antiapoptotic transcription factor nuclear factor-kappaB (NF-kappaB). HDIs also promote chromatin remodeling, potentially making the DNA more accessible to chemotherapy. We hypothesize that combined SAHA and gemcitabine sensitizes NSCLC to apoptosis.

METHODS

Three NSCLC cell lines (A549, H358, H460) were untreated, or treated with SAHA, gemcitabine, or both agents. NF-kappaB-dependent transcription was determined by reporter gene assays, reverse transcriptase-polymerase chain reaction RT-PCR, and Western blot analysis for the NF-kappaB-regulated antiapoptotic gene MnSOD. Survival of NSCLC cells overexpressing Bfl/A1, Bcl-X(L), or MnSOD and treated with SAHA and gemcitabine was determined in the presence or absence of NF-kappaB. Survival of treated cells overexpressing HDAC-1, 2, 3 or p/CAF was determined. Apoptosis was determined by fluorescence-activated cell sorter analysis, DNA fragmentation, and caspase-3 activity. Colony formation assays were performed on cells treated concurrently and sequentially with SAHA and gemcitabine. Assays were performed in triplicate, and the Student t test was applied as appropriate.

RESULTS

SAHA-activated NF-kappaB (P <or= .05) and gemcitabine inhibited these effects (P <or= .01). Increased cell survival was observed after overexpression of antiapoptotic genes, as well as in cells overexpressing HDAC-1, -2, and -3. Fluorescence-activated cell sorter analysis, DNA fragmentation, and caspase-3 assays all showed enhanced apoptosis with combined therapy, compared with single-agent therapy (P <or= .01). Sequential treatment offered no improvement over concurrent treatment.

CONCLUSIONS

Combined SAHA and gemcitabine sensitized NSCLC cells to apoptosis. Potential "proapoptotic" mechanisms for this finding include gemcitabine inhibition of SAHA-induced NF-kappaB activation and chromatin remodeling mediated by the inhibition of histone deacetylases.

Inhibition of phosphatidylinositol 3-kinase/Akt and histone deacetylase activity induces apoptosis in non-small cell lung cancer in vitro and in vivo

OBJECTIVE

Resistance to histone deacetylase inhibitors in non-small cell lung cancer is mediated in part through activation of nuclear factor-kappaB through a phosphatidylinositol 3-kinase/Akt-dependent pathway. We hypothesize that inhibition of phosphatidylinositol 3-kinase/Akt will sensitize non-small cell lung cancer cells to histone deacetylase inhibitor-induced apoptosis.

METHODS

Tumorigenic non-small cell lung cancer cell lines H157, H358, H460, and A549 were treated with nothing, the histone deacetylase inhibitor butyrate, the phosphatidylinositol 3-kinase/Akt inhibitor LY294002, or both compounds. Nuclear factor-kappaB activity was assessed by reporter gene assays and reverse transcriptase-polymerase chain reaction of the nuclear factor-kappaB dependent genes cIAP-2, Bfl/A1, and MnSOD. Whole cell extracts were immunoblotted for phospho-Akt, Akt, and phospho-ser/thr-Akt substrate. Cell death and apoptosis were measured by crystal violet staining, caspase-3 activity, and DNA fragmentation. A549 non-small cell lung cancer xenografts were created in athymic nude mice, and tumor growth was assessed after treatments as noted above. Explanted tumors underwent terminal deoxynucleotide transferase-mediated dUTP nick-end labeling and Western blot analyses for apoptosis assessment and drug target validation, respectively.

RESULTS

Butyrate activated nuclear factor-kappaB-dependent transcription, and LY294002 abrogated this effect. Combined treatment induced more apoptosis and cell death in vitro compared with either drug alone as measured by caspase-3, DNA fragmentation, and clonogenic survival. Combined butyrate and LY294002 was tumoristatic in vivo, but all other xenografts grew. This decreased tumor growth correlated with more apoptosis in the xenografts treated with combined therapy. Tumor levels of phospho-Akt and acetylated histone H3 were decreased and increased, respectively, in xenografts treated with combined therapy.

CONCLUSIONS

Combined histone deacetylase inhibitor and phosphatidylinositol 3-kinase/Akt pathway inhibition sensitized non-small cell lung cancer xenografts to apoptosis. Further investigations of this combined therapy are warranted as new pharmacologic phosphatidylinositol 3-kinase/Akt pathway inhibitors are developed.

The retinoid X receptor agonist bexarotene (Targretin) synergistically enhances the growth inhibitory activity of cytotoxic drugs in non-small cell lung cancer cells

This study was designed to evaluate, using preclinical models of non-small cell lung cancer (NSCLC), the growth inhibitory effects of the retinoid X receptor (RXR) agonist bexarotene (LGD1069, Targretin) in combination with cytotoxic agents currently used as standard first-line therapy in advanced disease. Although single-agent bexarotene had modest growth inhibitory effects in several cell lines, efficacy was observed only in the micromolar range (>1muM), which approximates the plasma C(max) measured in pharmacokinetic studies in patients. However, when combined with paclitaxel or vinorelbine, bexarotene produced a concentration-dependent enhancement of the growth inhibitory activities of paclitaxel and vinorelbine. Formal synergy analysis using the Calu3 cell line demonstrated that the combination of bexarotene with either cytotoxic agent produced synergistic activity (combination index, CI<1). The in vitro observations were confirmed in vivo in a NSCLC xenograft tumor model (Calu3), where both bexarotene/paclitaxel and bexarotene/vinorelbine combinations produced significantly greater antitumor effects than the single agents. These results demonstrate that bexarotene can cooperate with widely used cytotoxic agents to decrease the growth of NSCLC tumor cells both in vitro and in vivo, and suggest the potential benefit of adding a RXR-selective agonist in combination with chemotherapy for NSCLC treatment. Furthermore, the data support the clinical observation from phase I/IIa trials suggesting that bexarotene has beneficial effects on survival when used in combination with cytotoxic agents in advanced NSCLC.

Gemcitabine-mediated apoptosis is associated with increased CD95 surface expression but is not inhibited by DN-FADD in Colo357 pancreatic cancer cells

This study investigates the role of caspase-8 and DN-FADD, an inhibitor of CD95-dependent caspase-8 activation, in gemcitabine-induced apoptosis of Colo357 pancreatic cancer cells. Gemcitabine-mediated apoptosis was monitored by the kinetics of caspase-8 activation and cytochrome c release. Gemcitabine treatment of Colo357 cells increased CD95 surface expression, raising the possibility of the involvement of CD95 in gemcitabine-mediated caspase-8 activation. However, ectopic expression of DN-FADD and treatment of cells with the antagonistic anti-CD95 antibody ZB4 both failed to suppress gemcitabine-induced apoptosis but substantially inhibited CD95-mediated apoptosis. DN-FADD, which surprisingly accumulated in nuclei of Colo357 cells, was unable to block caspase-8 activation mediated by either gemcitabine or CD95. These observations argue against a role of CD95 in gemcitabine-induced caspase-8 activation and reveal that the anti-apoptotic function of DN-FADD differs from caspase-8 inhibition in Colo357 cells.

The selective retinoid X receptor agonist bexarotene (LGD1069, Targretin) prevents and overcomes multidrug resistance in advanced breast carcinoma

Acquired drug resistance represents a major challenge in the therapeutic management of breast cancer patients. We reported previously that the retinoid X receptor-selective agonist bexarotene (LGD1069, Targretin) was efficacious in treating animal models of tamoxifen-resistant breast cancer. The goal of this study was to evaluate the effect of bexarotene on development of acquired drug resistance and its role in overcoming acquired drug resistance in advanced breast cancer. Paclitaxel, doxorubicin, and cisplatin were chosen as model compounds to determine the effect of bexarotene on the development of acquired drug resistance. Human breast cancer cells MDA-MB-231 were repeatedly treated in culture with a given therapeutic agent with or without bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity. Compared with parental cells, cells treated with a single therapeutic agent became resistant to the therapeutic agent, whereas cells treated with the bexarotene combination remained chemosensitive. Cells with acquired drug resistance, when treated with the combination, showed increased sensitivity to the cytotoxic agent. Furthermore, cells treated with the combination regimen had reduced invasiveness and angiogenic potential than their resistant counterparts. These in vitro findings were further confirmed in an in vivo MDA-MB-231 xenograft model. Our results suggest a role for bexarotene in combination with chemotherapeutic agents in prevention and overcoming acquired drug resistance in advanced breast carcinoma.

Molecular mechanisms of drug resistance

Resistance to chemotherapy limits the effectiveness of anti-cancer drug treatment. Tumours may be intrinsically drug-resistant or develop resistance to chemotherapy during treatment. Acquired resistance is a particular problem, as tumours not only become resistant to the drugs originally used to treat them, but may also become cross-resistant to other drugs with different mechanisms of action. Resistance to chemotherapy is believed to cause treatment failure in over 90% of patients with metastatic cancer, and resistant micrometastic tumour cells may also reduce the effectiveness of chemotherapy in the adjuvant setting. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanisms of drug resistance that operate to reduce drug sensitivity in cancer cells. Drug resistance can occur at many levels, including increased drug efflux, drug inactivation, alterations in drug target, processing of drug-induced damage, and evasion of apoptosis. Advances in DNA microarray and proteomic technology, and the ongoing development of new targeted therapies have opened up new opportunities to combat drug resistance. We are now able to characterize the signalling pathways involved in regulating tumour cell response to chemotherapy more completely than ever before. This will facilitate the future development of rational combined chemotherapy regimens, in which the newer targeted therapies are used in combination with cytotoxic drugs to enhance chemotherapy activity. The ability to predict response to chemotherapy and to modulate this response with targeted therapies will permit selection of the best treatment for individual patients.

Proteasome inhibition sensitizes non-small cell lung cancer to histone deacetylase inhibitor-induced apoptosis through the generation of reactive oxygen species

OBJECTIVES

The histone deacetylase inhibitor suberoylanilide hydroxamic acid induces apoptosis in some malignancies through mitochondrial injury and generation of reactive oxygen species. Histone deacetylase inhibitors also activate the antiapoptotic transcription factor nuclear factor kappaB. We hypothesize that proteasome inhibition with bortezomib (Velcade; Millennium Pharmaceuticals, Inc, Cambridge, Mass)will inhibit nuclear factor kappaB activation, enhance suberoylanilide hydroxamic acid-induced mitochondrial injury, and sensitize non-small cell lung cancer cells to apoptosis.

METHODS

Four tumorigenic non-small cell lung cancer cell lines were treated with nothing, suberoylanilide hydroxamic acid, bortezomib, or both drugs. Nuclear factor kappaB-dependent transcription was determined by reporter gene assays and endogenous interleukin 8 transcription. Reactive oxygen species were quantified by using the fluorophore H 2 DCFDA. Cell viability was determined on the basis of clonogenic survival, and apoptosis was measured by quantifying caspase-3 activity and DNA fragmentation. Apoptosis and cell-survival assays were repeated in similarly treated cells incubated in the presence or absence of N-acetyl cysteine. Statistical significance was determined by means of analysis of variance.

RESULTS

Suberoylanilide hydroxamic acid significantly enhanced interleukin 8 and nuclear factor kappaB-dependent reporter gene transcription, and these effects were inhibited by bortezomib ( P < or = .01). Combined treatment with suberoylanilide hydroxamic acid and bortezomib induced greater reactive oxygen species generation, more apoptosis ( P < or = .02), and more cell death ( P < or = .001) than either drug alone. N-acetyl cysteine diminished the induction of apoptosis and enhanced cell survival ( P < or = .04).

CONCLUSIONS

Suberoylanilide hydroxamic acid and bortezomib synergistically induce reactive oxygen species generation in non-small cell lung cancer, and this plays a critical role in the induction of apoptosis after treatment. Combined treatment with suberoylanilide hydroxamic acid and bortezomib might be an effective treatment strategy for non-small cell lung cancer.

A Selective Retinoid X Receptor Agonist Bexarotene (Targretin) Prevents and Overcomes Acquired Paclitaxel (Taxol) Resistance in Human Non–Small Cell Lung Cancer

PURPOSE

Paclitaxel is an important anticancer agent for the treatment of non-small cell lung cancer (NSCLC). However, its use in cancer therapy is limited by development of acquired drug resistance. The goal of this study was to determine the effect of bexarotene on development of acquired paclitaxel resistance in NSCLC.

EXPERIMENTAL DESIGN

Human NSCLC Calu3 cells were repeatedly treated in culture with intermittent paclitaxel alone or in combination with continuous bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity in vitro and in vivo.

RESULTS

Repeat exposure to paclitaxel alone resulted in development of paclitaxel resistance with cross-resistance to multidrug resistance P-glycoprotein substrates, whereas the bexarotene/paclitaxel combination prevented the development of drug resistance and the cells remained chemosensitive. Furthermore, paclitaxel resistance could be overcome when the resistant cells were treated with the combination regimen. Fluctuation analysis showed that treatment with bexarotene decreased the rate of spontaneous development of paclitaxel resistance. In vivo, the bexarotene/paclitaxel combination regimen produced a statistically significant decrease in tumor growth in a Calu3 NSCLC xenograft model compared with the single agents (two-tailed, P < 0.05). In addition, paclitaxel-resistant Calu3 tumors treated with the bexarotene/paclitaxel combination showed greater delay in tumor growth compared with those treated with paclitaxel alone.

CONCLUSIONS

Our results suggest that bexarotene may offer a novel approach to prevent and overcome paclitaxel resistance in patients with NSCLC.

Antiapoptotic signaling pathways in non-small-cell lung cancer: biology and therapeutic strategies

One of the hallmarks of lung cancer is the deregulation of apoptotic or programmed cell death mechanisms usually found in normal cells that allow for corrupted cells to undergo cellular suicide. This includes mechanisms that attenuate proapoptotic pathways and/or amplify antiapoptotic pathways. Increasing evidence suggests that lung cancer cells use multiple and perhaps redundant pathways to maintain survival. Increasing knowledge of these pathways offers a better understanding of the biology of lung cancer as well as novel therapeutic strategies that can enhance lung cancer cell death. This review discusses the apoptotic machinery and signal transduction pathways that regulate apoptosis, methods of identifying the presence of activated survival signaling pathways in human lung cancers, and the clinical significance and relevance for therapy for patients with lung cancer.

Caspase-3 drives apoptosis in pancreatic cancer cells after treatment with gemcitabine

Pancreatic cancer remains a highly chemoresistant malignancy. Gemcitabine, the most effective first-line agent available, acts by disrupting cellular replication. Caspases belong to a family of proteases that function as key components of the apoptotic death machinery. We investigated the mechanisms by which gemcitabine blocks proliferation and whether it can induce apoptosis in pancreatic cancer cells. Quiescent pancreatic cancer cells (BxPC-3) were stimulated to proliferate (10% fetal calf serum) with or without gemcitabine, PS-341 (26S proteasome inhibitor), or both. Proliferation was measured by MTT assay and apoptosis by propidium iodine staining. To determine activation of the apoptotic regulatory cell proteins, caspase-3 and cleavage of poly(ADP-ribose)polymerase (PARP) into its 85-kDa fragment were assessed by Western blotting. Gemcitabine at even low doses (10 micromol/L) significantly inhibited cellular proliferation, whereas PS-341 (10 nmol/L) had no effect. With combined treatment, PS-341 potentiated the antiproliferative effects of gemcitabine (P=0.001). At 48 hours, the apoptotic fraction was greatly enhanced by the presence of PS-341 compared with gemcitabine alone. Caspase-3 accumulated as early as 30 minutes and was associated with cleavage of PARP to its apoptotic fragment. Gemcitabine, a nucleoside analogue, may in part exert its antiproliferative effects by directing pancreatic cancer cells to a default pathway of apoptosis. 26S proteasome inhibition potentiates this effect, suggesting its potential clinical value against chemoresistance in pancreatic cancer.

Proteasome Inhibition Sensitizes Non–Small-Cell Lung Cancer to Gemcitabine-Induced Apoptosis

BACKGROUND

My colleagues and I have previously shown that chemotherapy activates the antiapoptotic transcription factor nuclear factor (NF)-kappaB in non-small-cell lung cancer (NSCLC). We hypothesized that inhibition of NF-kappaB by using the proteasome inhibitor bortezomib (Velcade) would sensitize NSCLC to gemcitabine-induced apoptosis.

METHODS

Tumorigenic NSCLC cell lines (H157 and A549) were treated with nothing, gemcitabine, bortezomib, or both compounds. NF-kappaB activity was determined by nuclear p65 protein levels, electrophoretic mobility shift assays, and reverse transcription-polymerase chain reaction of the NF-kappaB-regulated genes interleukin-8, c-IAP2, and Bcl-xL. The p21 and p53 protein levels were determined in similarly treated cells. Cell-cycle dysregulation was assessed by fluorescence-activated cell sorting analysis. Cell death and apoptosis were quantified by clonogenic assays, caspase-3 activation, and DNA fragmentation. NSCLC A549 xenografts were generated and treated as noted previously. Tumor growth was assessed over a 4-week treatment period. Statistical analysis was performed with analysis of variance.

RESULTS

Gemcitabine enhanced nuclear p65 levels, NF-kappaB binding to DNA, and transcription of all NF-kappaB-regulated genes. Bortezomib inhibited each of these effects. Combined gemcitabine and bortezomib enhanced p21 and p53 expression and induced S-phase and G2/M cell-cycle arrests, respectively. Combined treatment killed 80% of the NSCLC cells and induced apoptosis, as determined by caspase-3 activation (p = 0.05) and DNA fragmentation (p = 0.02). NSCLC xenografts treated with combination therapy grew significantly slower than xenografts treated with gemcitabine alone (p = 0.02).

CONCLUSIONS

Bortezomib inhibits gemcitabine-induced activation of NF-kappaB and sensitizes NSCLC to death in vitro and in vivo. This combined treatment strategy warrants further investigation and may represent a reasonable treatment strategy for select patients with NSCLC given the current clinical availability of both drugs.

Caffeic acid phenethyl ester-induced PC-3 cell apoptosis is caspase-dependent and mediated through the loss of inhibitors of apoptosis proteins

OBJECTIVE

To investigate the effects of a novel agent, caffeic acid phethyl ester (CAPE) on nuclear factor (NF)-kappaB activation and apoptosis in the androgen-independent PC3 prostate cancer cell line.

MATERIALS AND METHODS

PC-3 cells were assessed for NF-kappaB activation induced by paclitaxel and tumour necrosis factor-alpha (TNF-alpha), using a p65 enzyme-linked immunosorbent assay, with or without CAPE treatment. The corresponding apoptosis was assessed with propidium iodide DNA staining using flow cytometry. The pan-caspase inhibitor Z-VAD-FMK was used to investigate the mechanism of apoptosis. Alterations in the expression of inhibitor of apoptosis proteins (IAP), cIAP-1, cIAP-2 and XIAP, were detected using western blot analysis.

RESULTS

CAPE prevented paclitaxel and TNFalpha-mediated NF-kappaB activation. Its ability to induce apoptosis in a dose-dependent manner was associated with the loss of cIAP-1, cIAP-2 and XIAP expression. Pretreatment with Z-VAD-FMK prevented CAPE-induced apoptosis and the loss of the IAPs.

CONCLUSIONS

CAPE is an effective inhibitor of NF-kappaB activation in PC-3 cells, but the mechanism of apoptosis, and the corresponding loss of IAP expression, is caspase-dependent.

Combined histone deacetylase and NF-κB inhibition sensitizes non-small cell lung cancer to cell death

BACKGROUND

Non-small cell lung cancer (NSCLC) remains resistant to traditional and novel chemotherapeutic agents, relating, in part, to the activation of the antiapoptotic transcription factor NF-kappaB. We hypothesize that inhibition of NF-kappaB using BAY-11-7085 will sensitize NSCLC cells to death, induced by the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA).

METHODS

Five tumorigenic NSCLC cell lines (A549, H157, H358, H460, H1299) were treated with nothing, SAHA, BAY-11-7085, or both compounds. Cell death was determined by crystal violet staining. p65 nuclear translocation was determined by Western blot analysis. NF-kappaB activity was determined by reporter-gene assays and by reverse transcriptase-polymerase chain reaction of the endogenous NF-kappaB-dependent gene interleukin 8. Apoptosis was determined by DNA fragmentation. Clonogenic cell survival assays were also performed. Data was analyzed with the Student t test when appropriate.

RESULTS

SAHA alone resulted in no meaningful NSCLC cell death. SAHA induced nuclear translocation of p65, which was inhibited by BAY-11-7085. SAHA significantly induced NF-kappaB-dependent transcription which was ameliorated after treatment with BAY-11-7085 (P = .01). Combined SAHA and BAY-11-7085 induced significantly more apoptosis and cell death than either drug alone (P = .002).

CONCLUSIONS

Combined HDI and NF-kappaB inhibition using BAY-11-7085 sensitizes NSCLC cells to cell death and appears promising as a novel treatment strategy for this disease.

RETRACTED: Retrovirally mediated RNA interference targeting the M2 subunit of ribonucleotide reductase: A novel therapeutic strategy in pancreatic cancer

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors-in-Chief, because an investigation by Harvard Medical School and the Brigham and Women’s Hospital has concluded that Figure 1A is invalid and no underlying research data are available to resolve the discrepancies or validate the reported results.

A novel role for carcinoembryonic antigen-related cell adhesion molecule 6 as a determinant of gemcitabine chemoresistance in pancreatic adenocarcinoma cells

Most patients with pancreatic adenocarcinoma present with surgically incurable disease. Gemcitabine, the principal agent used to treat such patients, has little impact on outcome. Overexpression of carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 6, a feature of this malignancy, is associated with resistance to anoikis and increased metastasis. The purpose of this study was to determine the role of CEACAM6 in cellular chemoresistance to gemcitabine. CEACAM6 was stably overexpressed in Capan2 cells, which inherently express very low levels of the protein. Suppression of CEACAM6 expression was achieved in BxPC3 cells, which inherently overexpress CEACAM6, by stable transfection of a CEACAM6 small interfering RNA-generating vector. The effects of modulating CEACAM6 expression on gemcitabine-induced cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assay, flow cytometric apoptosis quantification, caspase profiling, and Western analysis of cytoplasmic cytochrome c release. The roles of Akt and c-Src kinases as downstream targets of CEACAM6 signaling were examined. Stable overexpression of CEACAM6 in Capan2 increased gemcitabine chemoresistance, whereas CEACAM6 gene silencing in BxPC3 markedly increased the sensitivity of these cells to gemcitabine. Differential expression of CEACAM6 modulates Akt activity in a c-Src-dependent manner, and CEACAM6 overexpression appears to protect cells from cytochrome c-induced caspase 3 activation and apoptosis.

Combined proteasome and histone deacetylase inhibition in non-small cell lung cancer

OBJECTIVE

Inhibitors of histone deacetylases are potent inducers of cell-cycle arrest and apoptosis in certain malignancies. We have previously demonstrated that chemotherapy activates the antiapoptotic transcription factor nuclear factor kappa B in non-small cell lung cancer and fails to induce significant levels of apoptosis. We hypothesize that nuclear factor kappa B inhibition with the proteasome inhibitor bortezomib (formerly known as PS-341) will sensitize non-small cell lung cancer cells to histone deacetylase inhibitor-mediated apoptosis.

METHODS

Tumorigenic non-small cell lung cancer cells (A549, H358, and H460) were treated with bortezomib, followed by the histone deactylase inhibitor sodium butyrate. After treatment, nuclear factor kappa B transcriptional activity was measured by using a luciferase reporter assay and transcription of the nuclear factor kappa B-dependent gene IL8. Apoptosis was determined on the basis of caspase-3 activation and DNA fragmentation. Western blot analyses for the cell-cycle regulatory proteins p21 and p53 were performed, and cell-cycle alterations were determined by means of FACS analysis. Experiments were performed in triplicate, and statistical significance was determined by using unpaired t tests.

RESULTS

Butyrate increased nuclear factor kappa B transcriptional activity 4-fold relative to that seen in control cells (P =.05) in all non-small cell lung cancer cell lines. Treatment with bortezomib reduced butyrate-induced activation of nuclear factor kappa B to baseline levels. The proteins p21 and p53 were stabilized after treatment with bortezomib, correlating with a G(2)/M cell-cycle arrest. Treatment with butyrate alone resulted in minimal apoptosis, but combined histone deacetylase and proteasome inhibition increased apoptosis 3- to 4-fold (P =.02).

CONCLUSIONS

Combined molecular targeting of histone deacteylases and proteasomes synergistically induced apoptosis in non-small cell lung cancer. Pharmacologic nuclear factor kappa B suppression through proteasome inhibition, followed by treatment with histone deacetylase inhibitors, might represent a novel treatment strategy for patients with non-small cell lung cancer.

Modulation of antiapoptotic cell signaling pathways in non-small cell lung cancer: the role of NF-κB

Apoptosis, or programmed cell death, is a natural phenomenon that is critical for normal embryonic development and the maintenance of homeostasis in multicellular organisms. In adults, apoptosis represents a protective strategy that limits the spread of infection and helps prevent the development of malignancies. Cells acquiring nonrepairable DNA mutations are capable of "committing suicide" to prevent propagation of acquired genetic mutations and to eliminate their own malignant potential. Although malignant cells maintain the necessary intracellular apoptotic machinery, inappropriate inhibition of apoptosis allows for continued tumor growth and metastases. The majority of nonsmall cell lung cancer (NSCLC) exhibits dysregulated antiapoptotic pathways involving the transcription factor NF-kappaB. In addition, in NSCLC both chemotherapy and radiation upregulate antiapoptotic and cell-cycle regulatory proteins through NF-kappaB-dependent signaling mechanisms. Preclinical and phase I clinical trials suggest that inhibition of NF-kappaB markedly attenuates the resistance of NSCLC to undergo apoptosis and sensitizes these cells to chemotherapy. Modulation of the antiapoptotic cascade mediated by NF-kappaB, combined with either traditional or novel chemotherapeutic agents, represents a promising treatment strategy for patients with NSCLC.

Ineffectiveness of histone deacetylase inhibitors to induce apoptosis involves the transcriptional activation of NF-kappa B through the Akt pathway

Histone deacetylase (HDAC) inhibitors are emerging as a new class of anticancer agents for the treatment of solid and hematological malignancies. Although HDAC inhibitors induce cell death through an apoptotic process, little is known about the molecular events that control their effectiveness. In this study, we demonstrate that HDAC inhibitors are limited in their ability to induce apoptosis in non-small cell lung cancer (NSCLC) cell lines despite their ability to effectively inhibit deacetylase activity. Because the anti-apoptotic transcription factor NF-kappa B has been shown to be under the control of HDAC-mediated repression, we analyzed whether HDAC inhibitors activated NF-kappa B in NSCLC cells. HDAC inhibitors effectively stimulated endogenous NF-kappa B-dependent gene expression by up-regulating IL-8, Bcl-XL, and MMP-9 transcripts. The ability of HDAC inhibitors to increase NF-kappa B transcriptional activity was not associated with signaling events that stimulated nuclear translocation, but rather modulated the transactivation potential of the RelA/p65 subunit of NF-kappa B. The inhibition of HDAC activity was associated with the recruitment of the p300 transcriptional co-activator to chromatin in an Akt-dependent manner. Moreover, Akt directly phosphorylated p300 in vitro and was required for stimulating the transactivation potential of the co-activator following the addition of HDAC inhibitors. Selective inhibition of either the phosphoinositide 3-kinase/Akt pathway, or NF-kappa B itself blocked the ability of HDAC inhibitors to activate NF-kappa B and dramatically sensitized NSCLC cells to apoptosis following of the addition of HDAC inhibitors. Our study indicates that the ineffectiveness of HDAC inhibitors to induce apoptosis in NSCLC cancer cells is associated with the ability of these molecules to stimulate NF-kappa B-dependent transcription and cell survival.

Nitric oxide: a key regulator of myeloid inflammatory cell apoptosis

Apoptosis of inflammatory cells is a critical event in the resolution of inflammation, as failure to undergo this form of cell death leads to increased tissue damage and exacerbation of the inflammatory response. Many factors are able to influence the rate of apoptosis in neutrophils, eosinophils, monocytes and macrophages. Among these is the signalling molecule nitric oxide (NO), which possesses both anti- and proapoptotic properties, depending on the concentration and flux of NO, and also the source from which NO is derived. This review summarises the differential effects of NO on inflammatory cell apoptosis and outlines potential mechanisms that have been proposed to explain such actions.