Enhanced susceptibility of oral squamous cell carcinoma cell lines to FAS-mediated apoptosis by cisplatin and 5-fluorouracil

Progress in Drug and Formulation Development for the Chemoprevention of Oral Squamous Cell Carcinoma: A Review

BACKGROUND

Cancer is a life-threatening global problem with high incidence rates. Prioritizing the prevention of cancer, chemopreventive agents have drawn much attention from the researchers.

OBJECTIVE

This review focuses on the discussion of the progress in the development of chemopreventive agents and formulations related to the prevention of oral cancer.

METHODS

In this perspective, an extensive literature survey was carried out to understand the mechanism, control and chemoprevention of oral cancer. Different patented agents and formulations have also exhibited cancer preventive efficacy in experimental studies. This review summarizes the etiology of oral cancer and developments in prevention strategies.

RESULTS

The growth of oral cancer is a multistep activity necessitating the accumulation of genetic as well as epigenetic alterations in key regulatory genes. Many risk factors are associated with oral cancer. Genomic technique for sequencing all tumor specimens has been made available to help detect mutations. The recent development of molecular pathway and genetic tools has made the process of diagnosis easier, better forecast and efficient therapeutic management. Different chemical agents have been studied for their efficacy to prevent oral cancer and some of them have shown promising results.

CONCLUSION

Use of chemopreventive agents, either synthetic or natural origin, to prevent carcinogenesis is a worthy concept in the management of cancers. Preventive measures are helpful in controlling the occurrence or severity of the disease. The demonstrated results of preventive agents have opened an arena for the development of promising chemopreventive agents in the management of oral squamous cell carcinoma.

Polyamino Acid Layer-by-Layer (LbL) Constructed Silica-Supported Mesoporous Titania Nanocarriers for Stimuli-Responsive Delivery of microRNA 708 and Paclitaxel for Combined Chemotherapy

Cellular Fas-associated protein with death domain-like interleukin-1β-converting enzyme-inhibitory protein (c-FLIP), often strongly expressed in numerous cancers, plays a pivotal role in thwarting apoptosis and inducing chemotherapy resistance in cancer. An integrated approach combining chemotherapy with suppression of c-FLIP levels could prove paramount in the treatment of cancers with c-FLIP overexpression. In this study, we utilized a polymeric layer-by-layer (LbL) assembly of silica-supported mesoporous titania nanoparticles (MTNst) to co-deliver paclitaxel (PTX) and microRNA 708 (miR708) for simultaneous chemotherapy and c-FLIP suppression in colorectal carcinoma. The resulting LbL miR708/PTX-MTNst showed dose-dependent cytotoxicity in HCT-116 and DLD-1 colorectal carcinoma cell lines, which was remarkably superior to that of free PTX or LbL PTX-MTNst. LbL miR708/PTX-MTNst strongly inhibited c-FLIP expression and resulted in increased expression of proapoptotic proteins. In DLD-1 xenograft tumor-bearing mice, the nanoparticles accumulated in the tumor, resulting in remarkable tumor regression, with the PTX and miR708-loaded nanoparticles showing significantly greater inhibitory effects than the free PTX or PTX-loaded nanoparticles. Immunohistochemical analyses of the tumors further confirmed the remarkable apoptotic and antiproliferative effects of the nanoparticles, whereas organ histology reinforced the biocompatibility of the system. Therefore, the LbL miR708/PTX-MTNst system, owing to its ability to deliver both chemotherapeutic drug and inhibitory miRNA to the tumor site, shows great potential to treat colorectal carcinoma in clinical settings.

FLIP as a therapeutic target in cancer

One of the classic hallmarks of cancer is disruption of cell death signalling. Inhibition of cell death promotes tumour growth and metastasis, causes resistance to chemo- and radiotherapies as well as targeted agents, and is frequently due to overexpression of antiapoptotic proteins rather than loss of pro-apoptotic effectors. FLIP is a major apoptosis-regulatory protein frequently overexpressed in solid and haematological cancers, in which its high expression is often correlated with poor prognosis. FLIP, which is expressed as long (FLIP(L)) and short (FLIP(S)) splice forms, achieves its cell death regulatory functions by binding to FADD, a critical adaptor protein which links FLIP to the apical caspase in the extrinsic apoptotic pathway, caspase-8, in a number of cell death regulating complexes, such as the death-inducing signalling complexes (DISCs) formed by death receptors. FLIP also plays a key role (together with caspase-8) in regulating another form of cell death termed programmed necrosis or 'necroptosis', as well as in other key cellular processes that impact cell survival, including autophagy. In addition, FLIP impacts activation of the intrinsic mitochondrial-mediated apoptotic pathway by regulating caspase-8-mediated activation of the pro-apoptotic Bcl-2 family member Bid. It has been demonstrated that FLIP can not only inhibit death receptor-mediated apoptosis, but also cell death induced by a range of clinically relevant chemotherapeutic and targeted agents as well as ionizing radiation. More recently, key roles for FLIP in promoting the survival of immunosuppressive tumour-promoting immune cells have been discovered. Thus, FLIP is of significant interest as an anticancer therapeutic target. In this article, we review FLIP's biology and potential ways of targeting this important tumour and immune cell death regulator.

Adoptive immunotherapy combined with FP treatment for head and neck cancer: An in vitro study

FP treatment, which combines 5-fluorouracil (5-FU) and cisplatin (CDDP) chemotherapy, is widely used for treatment of advanced head and neck cancer (HNC). It has been suggested that these drugs cause immunomodulation in the cancer microenvironment, for example, downregulation of immunosuppressive cells such as regulatory T-cells (Tregs) and myeloid-derived suppressive cells (MDSCs), activating dendritic cells (DCs), and upregulation of tumor antigens and major histocompatibility complex (MHC) molecules in cancer cells leads to enhancement of cancer immunity, which is important in cancer treatment, as well as providing a direct killing effect. Therefore, development of chemoimmunotherapy by combining FP treatment with immunotherapy for HNC has become a recent challenging issue. However, the direct effects of these drugs on immune effector cells, especially cytotoxic T-lymphocytes (CTLs), are not well known. We have investigated the direct actions of these drugs on CTL functions in in vitro experiments using cytomegalovirus (CMV) pp65 antigen-specific CTLs (CMVpp65-CTLs) and oral squamous cell cancer (OSCC) cell lines overexpressing CMVpp65 antigen as target cells. Although CDDP partially inhibited proliferation of memory CMVpp65-CTL in peripheral blood, the proliferation was not inhibited by 5-FU. Cytotoxicity and the IFN-γ release response of the CMVpp65-CTLs were not inhibited by these drugs, and it is important to note that these drugs, especially 5-FU, sensitized OSCC cell lines to CMVpp65-CTL. Furthermore, CMVpp65-CTL cytotoxicity to CDDP-resistant OSCC cells, HSC-3/CDDP-R1, was the same as the cytotoxicity to the parental cells. Thus, we suggest that combined immunotherapy with FP treatment is an effective novel HNC treatment.

Differential resistance to platinum-based drugs and 5-fluorouracil in p22phox-overexpressing oral squamous cell carcinoma: Implications of alternative treatment strategies

BACKGROUND

We have previously shown that p22phox confers resistance to cisplatin in oral squamous cell carcinoma (OSCC). Whether p22phox has clinical correlation with cisplatin resistance and affects the efficacy of other platinum or nonplatinum drugs is unknown.

METHODS

The p22phox expression in tissues and apoptotic markers in cell lines was detected by immunoblotting. The cytotoxicity of chemotherapy drugs was determined by methylthiazol tetrazolium assay. In vivo chemoresistance of p22phox-overexpressing tumors was confirmed by the xenograft mouse model.

RESULTS

The p22phox was upregulated in tumors of patients with OSCC refractory to cisplatin treatment. The p22phox overexpression markedly increased the resistance to cisplatin and carboplatin, but not oxaliplatin and 5-fluorouracil (5-FU), in OSCC cells by differentially inhibiting the drug-induced apoptosis. Furthermore, p22phox-dependent resistance to cisplatin, but not 5-FU, was demonstrated in mouse xenograft tumors.

CONCLUSION

The p22phox expression may not only be a prognostic biomarker for prediction of chemotherapy outcomes, but the indication for alternative treatment strategies in oral cancer.

Interferon-α-inducible Dendritic Cells Matured with OK-432 Exhibit TRAIL and Fas Ligand Pathway-mediated Killer Activity

Active human dendritic cells (DCs), which efficiently induce immune responses through their functions as antigen-presenting cells, exhibit direct anti-tumour killing activity in response to some pathogens and cytokines. These antigen-presenting and tumour killing abilities may provide a breakthrough in cancer immunotherapy. However, the mechanisms underlying this killer DC activity have not been fully proven, despite the establishment of interferon-α (IFN-α)-generated killer DCs (IFN-DCs). Here mature IFN-DCs (mIFN-DCs), generated from IFN-DCs primed with OK-432 (streptococcal preparation), exhibited elevated expression of CD86 and human leukocyte antigen-DR (minimum criteria for DC vaccine clinical trials) as well as antigen-presenting abilities comparable with those of mature IL-4-DCs (mIL-4-DCs). Interestingly, the killing activity of mIFN-DCs, which correlated with the expression of CD56 (natural killer cell marker) and was activated via the tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand pathway, was stronger than that of IFN-DCs and remarkably stronger than that of mIL-4-DCs. Therefore, mIFN-DCs exhibit great potential as an anti-cancer vaccine that would promote both acquired immunity and direct tumour killing.

Comparative evaluation of PLGA nanoparticle delivery system for 5-fluorouracil and curcumin on squamous cell carcinoma

PURPOSE

The purpose of this study is to assess the effect of 5-fluorouracil nanoparticles and curcumin naoparticles on cell proliferation and the expression of the apoptotic marker (caspase 3) in squamous cell carcinoma cell line.

MATERIAL AND METHODS

PLGA 5-fluorouracil nanopartciles and PLGA curcumin nanoparticles were prepared and applied for 24 and 48h on human laryngeal squamous carcinoma cell line (Hep-2) as regard IC 50 concentration. MTT assay was used for evaluation of cytotoxicity of prepared nanoparticles. Quantitaive reverse transcriptase polymerase chain reaction (QRT-PCR) was used for the assessment of caspase-3 expression in the treated cell line.

RESULTS

The drug release rate profiles was dependent upon polymer to drug ratio, noting that the higher PLGA polymer ratio to 5-fluprouracil or curcumin drug showed faster release rates. On the other hand, the least PLGA polymer ratio to 5-fluprouracil or curcumin drug showed the slowest release rates. MTT assay revelaed that 5-fluorouracil nanoparticels or curcumin nanoparticels showed a clear cytotoxic effect on Hep-2 cell line compared to non treated cancer cells. The RT-PCR assessment of caspase-3 expression revealed that there was a significant increase in caspase-3 expression in Hep-2 cell line treated with 5-fluorouracil nanoparticles or curcumin compared to non treated cancer cells.

CONCLUSION

Curcumin nanoparticles could be more active in inducing apoptosis in short term assays (24h) than long term assays (48h) due to differential cellular uptake. While 5-fluorouracil nanoparticles induced higher significant apoptosis in long term (48h) compared to curcumin group.

In vitro and in vivo characterisation of a novel c-FLIP-targeted antisense phosphorothioate oligonucleotide

Previous studies have suggested that the caspase 8 inhibitor FLIP is a promising anti-cancer therapeutic target. In this study, we characterised a novel FLIP-targeted antisense phosphorothioate oligonucleotide (AS PTO). FLIP AS and control PTOs were assessed in vitro in transient transfection experiments and in vivo using xenograft models in Balb/c nude mice. FLIP expression was assessed by QPCR and Western. Apoptosis induction was determined by flow cytometry and Western. Of 5 sequences generated, one potently down-regulated FLIP. AS PTO-mediated down-regulation of FLIP resulted in caspase 8 activation and apoptosis induction in non-small cell lung (NSCLC) cells but not in normal lung cells. Similar results were observed in colorectal and prostate cancer cells. Furthermore, the FLIP AS PTO sensitized cancer cells but not normal lung cells to apoptosis induced by rTRAIL. Moreover, the FLIP AS PTO enhanced chemotherapy-induced apoptosis in NSCLC cells. Importantly, compared to a control non-targeted PTO, intra-peritoneal delivery of FLIP AS PTO inhibited the growth of NSCLC xenografts and enhanced the in vivo antitumour effects of cisplatin. We have identified a novel FLIP-targeted AS PTO that has in vitro and in vivo activity and which therefore has potential for further pre-clinical development.

Anoikis mediators in oral squamous cell carcinoma

Anoikis - apoptotic cell death triggered by loss of extracellular matrix (ECM) contacts - is dysregulated in many chronic debilitating and fatal diseases. Mechanisms rendering tumor cells resistant to anoikis, although not completely understood, possess significant therapeutic promise. In death receptor-mediated anoikis mechanisms, focal adhesion kinase (FAK) and receptor-interacting protein (RIP) dissociate, leading to association of RIP with Fas, formation of the death-inducing signaling complex (DISC), activation of caspase-3, and propagation of anoikis. In contrast, anoikis resistance is accomplished through constitutive activation of survival pathways that include integrin-dependent activation of FAK and extracellular-signal-regulated kinase (ERK). In addition, FAK and RIP association confers anoikis resistance by inhibiting the association of RIP with Fas and formation of the death signaling complex, which allows cells to escape anoikis. Up-regulation of CD44 also contributes to survival signals and promotes anoikis resistance. This review will focus on the roles of death receptors, prosurvival pathways, and the molecular players involved in anoikis escalation and resistance in oral squamous cell carcinoma.

Early effects of FOLFOX treatment of colorectal tumour in an animal model: assessment of changes in gene expression and FDG kinetics

PURPOSE

The very early chemotherapeutic effects of the FOLFOX (fluorouracil, folinic acid, oxaliplatin) protocol were assessed in mice implanted with a human colorectal cell line. The aim of this study was to identify changes in gene expression patterns and to detect combinations of PET parameters that may be helpful in identifying treated tumours early after chemotherapy using dynamic PET studies.

METHODS

A human colorectal cell line (HCT 116) was used in nude mice. Dynamic PET studies were performed in untreated (n = 13) and treated (n = 12) animals. The data were assessed using compartmental and noncompartmental analysis. The removed tumour specimens were assessed by gene array analysis to obtain quantitative information on gene expression.

RESULTS

One chemotherapeutic treatment using the FOLFOX protocol resulted in an upregulation of 2,078 gene probes by more than 25%, while 2,254 probes were downregulated following treatment. The gene array data demonstrated primarily an enhancement of genes related to apoptosis. In particular, the apoptosis antigen 1 (APO-1), p21 and the G protein-coupled receptor 87 (G-87) were 2.6- to 3.3-fold upregulated as compared to the expression in untreated animals. There was a 100% separation of untreated and treated animals on the basis of these three genes. The SUV and the FDG kinetic parameters obtained by compartmental and noncompartmental fitting were not significantly different when individual parameters were compared between groups. However, classification analysis of the combination of the PET parameters VB, K1, k3, and influx revealed an overall accuracy of 84%. We were able to identify 91.7% (11/12) of the treated animals and 76.9% (10/13) of the untreated animals correctly using the classification analysis of PET data.

CONCLUSION

Even one chemotherapeutic treatment using FOLFOX has an impact on gene expression and significantly modulates FDG kinetics. Quantitative assessment of the tracer kinetics and the application of classification analysis to the data are promising tools to identify those tumours that demonstrate a chemotherapeutic effect very early following treatment.

Chinese herb related molecules of cancer-cell-apoptosis: a minireview of progress between Kanglaite injection and related genes

Many kinds of Chinese herb had been confirmed to have the character of anti-tumor, clinical reports about anti-tumor effects of Chinese herb had also been found in recent years, but most of the reports were focused on the clinical treatment of effectiveness for Chinese herb, on the other hand, review about Chinese herbal related with molecules on cancer-cell-apoptosis was seldom, many scientists could not believe such kinds of clinical describes about anti-tumor effects for Chinese herb, because these describes were lack of molecular biology evidence. Kanglaite(KLT) injection is an anti-tumor new drug which extracts from Chinese medicine-coix seed with modern advanced pharmaceutical technology, it is also a new biphase extended-spectrum anticancer medicine, the food and drug administration(FDA) of United States also approved a phase II trial of KLT to test its efficacy in treating non-small-cell lung cancer. Some studies show it could inhibit some anti-apoptotic gene and activate some pro-apoptotic gene, its injection solution is one of the new anticancer medicine that can significantly inhibit a various kinds of tumor cells, so it has become the core of research that how to further explore KLT injection to promote tumor cell apoptosis by impacting on related genes. In this review, the relationship between KLT and some tumor cell apoptosis molecules had been discussed and reviewed generally.

Epidermal growth factor receptor inhibitors enhance susceptibility to Fas-mediated apoptosis in oral squamous cell carcinoma cells

Molecular inhibition of epidermal growth factor receptor (EGFR) signaling is a promising cancer treatment strategy. We examined whether inhibition of EGFR signaling would affect the susceptibility of oral squamous cell carcinoma (OSCC) cells to Fas-mediated apoptosis. Treatment of OSCC cells with an anti-EGFR monoclonal antibody, C225, and an EGFR tyrosine kinase inhibitor, AG1478, which target the extracellular and intracellular domains of the receptor, respectively, inhibited phosphorylation of EGFR and its downstream effector molecule Akt and amplified the induction of Fas-mediated apoptosis. In OSCC cells treated with EGFR inhibitors, Fas-mediated apoptosis was accompanied by caspase-8 activation but not Bid cleavage. Caspase-3 and -8 inhibitors reduced the effect of EGFR inhibitors on Fas-mediated apoptosis in OSCC cells, but a caspase-9 inhibitor did not. These results indicate that the pro-apoptotic activity of EGFR inhibitors in OSCC cells depends on the extrinsic pathway of the caspase cascade. Although EGFR inhibitors did not affect the expression of Fas, the Fas-associated death domain protein, or procaspase-8 in OSCC cells, the inhibition downregulated cellular FLICE-inhibitory protein (c-FLIP). Moreover, knockdown of c-FLIP in HSC-2 cells with a small interfering RNA strongly enhanced Fas-mediated apoptosis. These results suggest that the EGFR signaling pathway may, in part, regulate Fas-mediated apoptosis in OSCC cells through c-FLIP expression.

Effects of cisplatin, alpha-interferon, and 13-cis retinoic acid on the expression of Fas (CD95), intercellular adhesion molecule-1 (ICAM-1), and epidermal growth factor receptor (EGFR) in oral cancer cell lines

BACKGROUND

Previous studies showed that many chemotherapeutic agents can induce immuno-suppression at therapeutic drug concentrations whereas low drug doses induce immuno-augmentation.

METHODS

The effect of low-dose cisplatin, interferon-alpha, and 13-cis retinoic acid on receptors involved in immune-mediated apoptosis (Fas/CD95), cell growth (epidermal growth factor receptor) and lymphocyte adhesion (intercellular adhesion molecule-1) was investigated in two oral cancer cell lines (UT-SCC-20A and UT-SCC-24A). Different methods for cell preparation were studied: mechanical and enzymatic detachment, and culture on chamber slides. Receptor expression was investigated using immunohistochemical staining. The amount of soluble and cell-bound Fas was determined with the ELISA technique, and the functional relevance of Fas expression, apoptosis induction, was analyzed.

RESULTS

Cisplatin enhanced cytoplasm and membrane staining for Fas in both cell lines. After cisplatin treatment, the amount of soluble Fas was increased in UT-SCC-20A cultures, but no effect was observed in the UT-SCC-24A cell line. Apoptosis, measured as enhanced caspase-3 activity, was induced by an agonistic Fas antibody (CH11) after cisplatin treatment in UT-SCC-24A cells.

CONCLUSIONS

Low-dose cisplatin treatment enhanced Fas expression in both cell lines and increased susceptibility to apoptosis in one of them.

Luteolin sensitizes the anticancer effect of cisplatin via c-Jun NH2-terminal kinase-mediated p53 phosphorylation and stabilization

Luteolin is an important flavonoid with a potential anticancer effect. In this study, we examined the molecular mechanisms involved in the sensitization effect of luteolin on cancer cell killing induced by cisplatin, an important cancer chemotherapeutic agent. First, we provided evidence that the sensitization effect of luteolin on cisplatin-induced apoptosis is p53 dependent, as such effect is only found in p53 wild-type cancer cells but not in p53 mutant cancer cells. Moreover, knockdown of p53 by small interfering RNA made p53 wild-type cancer cells resistant to luteolin and cisplatin. Second, we observed a significant increase of p53 protein level in luteolin-treated cancer cells without increase of p53 mRNA level, indicating the possible effect of luteolin on p53 posttranscriptional regulation. Third, we identified the critical role of c-Jun NH(2)-terminal kinase (JNK) in regulation of p53 protein stability: luteolin activates JNK, and JNK then stabilizes p53 via phosphorylation, leading to reduced ubiquitination and proteasomal degradation. Finally, by using an in vivo nude mice xenograft model, we confirmed that luteolin enhanced the cancer therapeutic activity of cisplatin via p53 stabilization and accumulation. In summary, data from this study reveal a novel molecular mechanism involved in the anticancer effect of luteolin and support its potential clinical application as a chemosensitizer in cancer therapy.

Role of the Fas/FasL pathway in combination therapy with interferon-alpha and fluorouracil against hepatocellular carcinoma in vitro

BACKGROUND/AIMS

Several studies have reported the efficacy of combination therapy of interferon (IFN) alpha and 5-fluorouracil (5-FU) for hepatocellular carcinoma (HCC). However, the mechanism underlying the clinical anti-tumor effects of this treatment is not well understood. The aim of this study was to determine the role of Fas/FasL signaling in the anti-tumor effect of this combination therapy.

METHODS AND RESULTS

We used six human hepatoma cell lines, three of which are known Fas-expressing cells. Growth of Fas-positive hepatoma cell lines was inhibited by an agonistic anti-Fas antibody in a dose-dependent manner, and these effects were enhanced by IFNalpha or 5-FU alone, but even more so by combination therapy using both agents. Annexin-V assay implicated apoptosis as the main mechanism underlying these growth inhibitory effects, although changes in Fas expression regulated by IFNalpha and/or 5-FU did not correlate with increased apoptosis. Caspase-3 activation was exclusively increased by IFNalpha/5-FU combination treatment, which was compatible with enhancement of the synergistic apoptotic effect, and other caspases and apoptotic factors (FLIP, BCL-xl, and Bax) were also regulated by IFNalpha/5-FU. 51Cr-release assay revealed that pretreatment with IFN activated cytotoxicity of peripheral blood mononuclear cells (PBMCs) against HCC cells. The largest interaction was observed when both PBMC and HCC cells were pretreated with the combination of IFNalpha/5-FU. These cytotoxicities were markedly inhibited by a neutralizing anti-Fas antibody.

CONCLUSIONS

Our results indicated that IFNalpha/5-FU combination treatment enhances the induction of apoptosis and the cytotoxic effect of PBMCs via the Fas/FasL pathway. The Fas/FasL pathway seems, at least in part, to contribute to the anti-tumor effects of IFNalpha/5-FU against HCCs.

Enhancement of susceptibility to Fas-mediated apoptosis in oral squamous cell carcinoma cells by phosphatidylinositol 3-kinase inhibitor

In general, oral squamous cell carcinoma (OSCC) cells are relatively resistant to Fas-mediated apoptosis during in vitro culture. Here, we studied the role of survival/apoptosis associated phosphatidylinositol 3-kinase (PI 3-K)/Akt in this process. We found that both PI 3-K inhibitors, wortmannin and LY294002, markedly suppressed the phosphorylation of Akt and accelerated Fas-mediated apoptosis in OSCC cells. It was found that caspase-3 and -8 inhibitors reduced the accelerative effect of PI 3-K inhibitor on Fas-mediated apoptosis in OSCC cells, but not caspase-9 inhibitor. Although PI 3-K inhibitors did not affect the Fas expression of OSCC cells, cellular FLICE-inhibitory protein (c-FLIP) levels were markedly reduced by PI 3-K inhibitor treatment. Moreover, antisense oligonucleotide to c-FLIP confirmed that the down-regulation of c-FLIP enhanced the sensitization to Fas-mediated apoptosis in OSCC cells. These results suggest that PI 3-K/Akt signaling pathway may, in part, regulate Fas-mediated apoptosis in OSCC cells through c-FLIP expression.

Mechanistic and predictive profiling of 5-Fluorouracil resistance in human cancer cells

Gene expression was analyzed in five pairs of 5-fluorouracil (5-FU) resistant and parental cancer cell lines on DNA microarrays. In unsupervised analysis, a prediction rule was built from the expression profiles of 29 genes, and 5-FU sensitivity class was predicted with 100% accuracy and high predictive strength. In supervised analysis of key 5-FU pathways, expression of 91 genes was associated with 5-FU sensitivity phenotype and segregated samples accordingly in hierarchical analysis. Key genes involved in 5-FU activation were significantly down-regulated (thymidine kinase, 2.9-fold; orotate phosphoribosyltransferase, 2.3-fold; uridine monophosphate kinase, 3.2-fold; pyrimidine nucleoside phosphorylase 3.6-fold) in resistant cells. Overexpression of thymidylate synthase and its adjacent gene, c-Yes, was detected in the resistant cell lines. The mRNA and protein overexpression of nuclear factor kappaB (NFkappaB) p65 and related antiapoptotic c-Flip gene was detected in resistant cells. The 5-FU-resistant cell lines also showed high NFkappaB DNA-binding activity. Cotransfection of NFkappaB p50 and p65 cDNA induced 5-FU resistance in MCF-7 cells. Both NFkappaB- and 5-FU-induced resistant cell lines manifested reduced expression of genes governing G(1)-S and S-phase transition. Expression of genes involved in DNA replication was also down-regulated in resistant cell lines. These findings were highly consistent with the slower growth rate, higher proportion of G(1), and lower proportion of S-phase cells in the resistant cell lines. This phenotype may protect resistant cells from cell death induced by incorporation of 5-FU into DNA chains, by allowing time to repair 5-FU-induced damage. Our findings may provide novel targets for tackling 5-FU resistance.

Lessons from TRAIL-resistance mechanisms in colorectal cancer cells: paving the road to patient-tailored therapy

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Intrinsic, as well as acquired, resistance to chemotherapy remains a major problem in the treatment of this disease. It is, therefore, of great importance to develop new, patient-tailored, treatment strategies for colorectal cancer patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) acts through the pro-apoptotic DR4 and DR5 receptors in tumor cells without harming normal cells and will soon be tested in clinical trials as a novel anti-cancer agent. However, not all human colon cancer cell lines are sensitive to TRAIL due to intrinsic or acquired TRAIL-resistance. This review discusses the mechanisms and modulation of TRAIL-resistance in colon cancer cells. Cell sensitivity to TRAIL can be affected by TRAIL-receptor expression at the cell membrane, DR4/DR5 ratio and functionality of TRAIL-receptors. Additional intracellular factors leading to TRAIL-resistance affect the caspase 8/c-FLIP ratio, such as loss of caspase 8 and caspase 10 due to mutations or gene methylation, CARP-dependent degradation of active caspase 8 and changes in caspase 8 or c-FLIP expression levels. Further downstream in the TRAIL apoptotic pathway, Bax mutations, or increased expression of IAP family members, in particularly XIAP and survivin, also cause resistance. Chemotherapeutic drugs, NSAIDs, interferon-gamma and proteasome inhibitors can overcome TRAIL-resistance by acting on TRAIL-receptor expression or changing the expression of pro- or anti-apoptotic proteins.

The role of apoptosis in oral disease: mechanisms; aberrations in neoplastic, autoimmune, infectious, hematologic, and developmental diseases; and therapeutic opportunities

Apoptosis is a genetically programmed form of cell death, which primarily functions to eliminate senescent or altered cells that are useless or harmful for the multicellular organism. Contrary to necrosis, apoptosis represents a physiologic cellular mechanism, normal function and control of which are critical for the development and homeostasis of multicellular organisms. In contrast, aberrations of the apoptotic mechanisms that cause excessive or deficient programmed cell death have been linked to a wide array of pathologic conditions. This review briefly summarizes the major apoptotic pathways and molecules and presents the most important oral diseases that are related to dysregulation of apoptosis. Knowledge of the association between aberrations in apoptotic mechanisms and human pathology hopefully will be implemented for the design of improved diagnostic and prognostic assays and the development of novel, more efficient, therapeutic strategies.