Conventional Cytostatic Drugs Research Articles

Mitochondria-targeted compounds in the treatment of cancer.

Mitochondria are highly dynamic organelles involved in many cellular functions. Beyond their central role in metabolism, they also take a part in maintaining calcium homeostasis, cell death, immunity, and ROS production. Changes in these functions have been shown to be crucial for the adaptation and survival of cancer cells. Mitochondria, therefore, constitute a promising target for the development of novel anticancer agents. The triphenylphosphonium (TPP+) moiety has been widely used to target molecules into mitochondria. TPP+ derivatives of a variety of conventional cytostatic drugs, natural substances, metformin, antioxidants or a range of newly synthesized molecules have shown promising results against cancer cells. In this review, we discuss biochemical differences between cancer cells and normal cells with a specific focus on mitochondria, and how mitochondrially targeted molecules can be used to selectively affect mitochondrial function in normal and cancer cells. We summarize the published data on mitochondrially targeted anticancer agents and propose future research avenues.

Type I Interferons and Cancer: An Evolving Story Demanding Novel Clinical Applications.

The first report on the antitumor effects of interferon α/β (IFN-I) in mice was published 50 years ago. IFN-α were the first immunotherapeutic drugs approved by the FDA for clinical use in cancer. However, their clinical use occurred at a time when most of their mechanisms of action were still unknown. These cytokines were being used as either conventional cytostatic drugs or non-specific biological response modifiers. Specific biological activities subsequently ascribed to IFN-I were poorly considered for their clinical use. Notably, a lot of the data in humans and mice underlines the importance of endogenous IFN-I, produced by both immune and tumor cells, in the control of tumor growth and in the response to antitumor therapies. While many oncologists consider IFN-I as “dead drugs”, recent studies reveal new mechanisms of action with potential implications in cancer control and immunotherapy response or resistance, suggesting novel rationales for their usage in target and personalized anti-cancer treatments. In this Perspectives Article, we focus on the following aspects: (1) the added value of IFN-I for enhancing the antitumor impact of standard anticancer treatments (chemotherapy and radiotherapy) and new therapeutic approaches, such as check point inhibitors and epigenetic drugs; (2) the role of IFN-I in the control of cancer stem cells growth and its possible implications for the development of novel antitumor therapies; and (3) the role of IFN-I in the development of cancer vaccines and the intriguing therapeutic possibilities offered by in situ delivery of ex vivo IFN-stimulated dendritic cells.

Targeting Metastasis with Snake Toxins: Molecular Mechanisms.

Metastasis involves the migration of cancer cells from a primary tumor to invade and establish secondary tumors in distant organs, and it is the main cause for cancer-related deaths. Currently, the conventional cytostatic drugs target the proliferation of malignant cells, being ineffective in metastatic disease. This highlights the need to find new anti-metastatic drugs. Toxins isolated from snake venoms are a natural source of potentially useful molecular scaffolds to obtain agents with anti-migratory and anti-invasive effects in cancer cells. While there is greater evidence concerning the mechanisms of cell death induction of several snake toxin classes on cancer cells; only a reduced number of toxin classes have been reported (i.e., disintegrins/disintegrin-like proteins, C-type lectin-like proteins, C-type lectins, serinproteases, cardiotoxins, snake venom cystatins) as inhibitors of adhesion, migration, and invasion of cancer cells. Here, we discuss the anti-metastatic mechanisms of snake toxins, distinguishing three targets, which involve (1) inhibition of extracellular matrix components-dependent adhesion and migration, (2) inhibition of epithelial-mesenchymal transition, and (3) inhibition of migration by alterations in the actin/cytoskeleton network.

Gastrin activates autophagy and increases migration and survival of gastric adenocarcinoma cells

BackgroundThe peptide hormone gastrin exerts a growth-promoting effect in both normal and malignant gastrointestinal tissue. Gastrin mediates its effect via the cholecystokinin 2 receptor (CCKBR/CCK2R). Although a substantial part of the gastric adenocarcinomas express gastrin and CCKBR, the role of gastrin in tumor development is not completely understood. Autophagy has been implicated in mechanisms governing cytoprotection, tumor growth, and contributes to chemoresistance. This study explores the role of autophagy in response to gastrin in gastric adenocarcinoma cell lines.MethodsImmunoblotting, survival assays and the xCELLigence system were used to study gastrin induced autophagy. Chemical inhibitors of autophagy were utilized to assess the role of this process in the regulation of cellular responses induced by gastrin. Further, knockdown studies using siRNA and immunoblotting were performed to explore the signaling pathways that activate autophagy in response to gastrin treatment.ResultsWe demonstrate that gastrin increases the expression of the autophagy markers MAP1LC3B-II and SQSTM1 in gastric adenocarcinoma cells. Gastrin induces autophagy via activation of the STK11-PRKAA2-ULK1 and that this signaling pathway is involved in increased migration and cell survival. Furthermore, gastrin mediated increase in survival of cells treated with cisplatin is partially dependent on induced autophagy.ConclusionThis study reveals a novel role of gastrin in the regulation of autophagy. It also opens up new avenues in the treatment of gastric cancer by targeting CCKBR mediated signaling and/or autophagy in combination with conventional cytostatic drugs.

Ferulic acid reverses ABCB1-mediated paclitaxel resistance in MDR cell lines

Multidrug resistance (MDR) remains a major obstacle in cancer chemotherapy. The use of the dietary phytochemicals as chemosensitizing agents to enhance the efficacy of conventional cytostatic drugs has recently gained the attention as a plausible approach for overcoming the drug resistance. The aim of this study was to investigate whether a naturally occurring diet-based phenolic acid, ferulic acid, could sensitize paclitaxel efficacy in ABCB1 overexpressing (P-glycoprotein) colchicine selected KB ChR8-5 cell line. In vitro drug efflux assays demonstrated that ferulic acid inhibits P-glycoprotein transport function in drug resistant KB ChR8-5 cell lines. However, ferulic acid significantly downregulates ABCB1 expression in a concentration dependent manner. Cytotoxicity assay reveals that ferulic acid decreased paclitaxel resistance in KBChR8-5 and HEK293/ABCB1 cells, which indicates its chemosensitizing potential. Clonogenic cell survival assay and apoptotic morphological staining further confirm the chemosensitizing potential of ferulic acid in drug resistant KB ChR8-5 cell lines. Ferulic acid treatment enhances paclitaxel mediated cell cycle arrest and upregulates paclitaxel-induced apoptotic signaling in KB resistant cells. Hence, it has been concluded that downregulation of ABCB1 and subsequent induction of paclitaxel-mediated cell cycle arrest and apoptotic signaling may be the cause for the chemosensitizing potential of ferulic acid in P-gp overexpressing cell lines.

Paclitaxel and the dietary flavonoid fisetin: a synergistic combination that induces mitotic catastrophe and autophagic cell death in A549 non-small cell lung cancer cells

Background The use of the dietary polyphenols as chemosensitizing agents to enhance the efficacy of conventional cytostatic drugs has recently gained the attention of scientists and clinicians as a plausible approach for overcoming the limitations of chemotherapy (e.g. drug resistance and cytotoxicity). The aim of this study was to investigate whether a naturally occurring diet-based flavonoid, fisetin, at physiologically attainable concentrations, could act synergistically with clinically achievable doses of paclitaxel to produce growth inhibitory and/or pro-death effects on A549 non-small cell lung cancer cells, and if it does, what mechanisms might be involved.MethodsThe drug–drug interactions were analyzed based on the combination index method of Chou and Talalay and the data from MTT assays. To provide some insights into the mechanism underlying the synergistic action of fisetin and paclitaxel, selected morphological, biochemical and molecular parameters were examined, including the morphology of cell nuclei and mitotic spindles, the pattern of LC3-II immunostaining, the formation of autophagic vacuoles at the electron and fluorescence microscopic level, the disruption of cell membrane asymmetry/integrity, cell cycle progression and the expression level of LC3-II, Bax, Bcl-2 and caspase-3 mRNA.ResultsHere, we reported the first experimental evidence for the existence of synergism between fisetin and paclitaxel in the in vitro model of non-small cell lung cancer. This synergism was, at least partially, ascribed to the induction of mitotic catastrophe. The switch from the cytoprotective autophagy to the autophagic cell death was also implicated in the mechanism of the synergistic action of fisetin and paclitaxel in the A549 cells. In addition, we revealed that the synergism between fisetin and paclitaxel was cell line-specific as well as that fisetin synergizes with arsenic trioxide, but not with mitoxantrone and methotrexate in the A549 cells.ConclusionsOur results provide rationale for further testing of fisetin in the combination with paclitaxel or arsenic trioxide to obtain detailed insights into the mechanism of their synergistic action as well as to evaluate their toxicity towards normal cells in an animal model in vivo. We conclude that this study is potentially interesting for the development of novel chemotherapeutic approach to non-small cell lung cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12935-016-0288-3) contains supplementary material, which is available to authorized users.

Analysis of the antiproliferative effects of 3-deazaneoplanocin A in combination with standard anticancer agents in rhabdoid tumor cell lines.

Rhabdoid tumors (RTs) are highly aggressive pediatric malignancies with a rather poor prognosis. New therapeutic approaches and optimization of already established treatment protocols are urgently needed. The histone methyltransferase enhancer of zeste homolog 2 (EZH2) is highly overexpressed in RTs and associated strongly with epigenetic silencing in cancer. EZH2 is involved in aggressive cell growth and stem cell maintenance. Thus, EZH2 is an attractive therapeutic target in RTs. The aim of the study presented here was to analyze the effects of a pharmacological inhibition of EZH2 alone and in combination with other anticancer drugs on RTs cells in vitro. The antitumor activity of the S-adenosyl-homocysteine-hydrolase inhibitor 3-deazaneplanocin A (DZNep) alone and in combination with conventional cytostatic drugs (doxorubicin, etoposide) or epigenetic active compounds [5-Aza-CdR, suberoylanilide hydroxamic acid (SAHA)] was assessed by MTT cell proliferation assays on three RT cell lines (A204, BT16, G401). Combinatorial treatment with DZNep synergistically and significantly enhanced the antiproliferative activity of etoposide, 5-Aza-CdR, and SAHA. In functional analyses, pretreatment with DZNep significantly increased the effects of 5-Aza-CdR and SAHA on apoptosis, cell cycle progression, and clonogenicity. Microarray analyses following sequential treatment with DZNep and 5-Aza-CdR or SAHA showed changes in global gene expression affecting apoptosis, neuronal development, and metabolic processes. In-vitro analyses presented here show that pharmacological inhibition of EZH2 synergistically affects the antitumor activity of the epigenetic active compounds 5-Aza-CdR and SAHA. Sequential treatment with these drugs combined with DZNep may represent a new therapeutic approach in RTs.

Selected attributes of polyphenols in targeting oxidative stress in cancer.

Various plant polyphenols have been recognized as redox active molecules. This review discusses some aspects of polyphenols' modes of redox action, corresponding structure-activity relationships and their potential to be applied as adjuvants to conventional cytostatic drugs. Polyphenols' antioxidative capacity has been discussed as the basis for targeting oxidative stress and, consequently, for their chemopreventive and anti-inflammatory activities, which may alleviate side-effects on normal cells arising from oxidative stress caused by cytostatics. Some polyphenols may scavenge various free radicals directly, and some of them are found to suppress free radical production through inhibiting NADPH oxidases and xanthine oxidase. Additionally, polyphenols may increase antioxidative defense in normal cells by increasing the activity of NRF2, transcription factor for many protective proteins. The activation of the NRF2-mediated signaling pathways in cancer cells results in chemoresistance. Luteolin, apigenin and chrysin reduce NRF2 expression and increase the chemosensitivity of cancer cells to cytostatic drugs. Their common 5,7-dihydroxy-4H-chromen-4-one moiety, may represent a starting pharmacophore model for designing novel, non-toxic compounds for overcoming chemoresistance. However, prooxidative activity of some polyphenols (quercetin, EGCG) may also provide a basis for their use as chemotherapeutic adjuvants since they may enhance cytotoxic effects of cytostatics selectively on cancer cells. However, considerable caution is needed in applying polyphenols to anticancer therapy, since their effects greatly depend on the applied dose, the cell type, exposure time and environmental conditions.

Liposomal polychemotherapy improves adrenocortical carcinoma treatment in a preclinical rodent model

Owing to high relapse rates and early metastatic spread, prognosis in adrenocortical carcinoma (ACC) patients remains poor, highlighting the importance of developing new treatment alternatives for them. Recently, polychemotherapy regimens including etoposide, doxorubicin, and cisplatin together with mitotane (EDP-M) have been defined as the standard treatment for late-stage disease patients. Nevertheless, the administration of conventional cytostatic drugs is associated with severe and dose-limiting side effects. In an attempt to optimize existing clinical treatment regimens, in this study, we investigated the therapeutic efficacy of EDP-M in comparison with that of a paclitaxel-modified scheme (paclitaxel, doxorubicin, cisplatin plus mitotane (PDP-M)) in preclinical in vitro and in vivo models. In addition, based on an extraordinary uptake phenomenon of liposomes in ACC cells, we further evaluated liposomal variants of these protocols (etoposide, liposomal doxorubicin, liposomal cisplatin plus mitotane (LEDP-M) and nab-paclitaxel, liposomal doxorubicin, liposomal cisplatin plus mitotane (LPDP-M)). In vitro, PDP-M was more potent in the induction of apoptosis and inhibition of cell viability as well as cell proliferation than EDP-M. Following the administration of a single therapeutic cycle, we further demonstrated that LEDP-M and LPDP-M exerted significant antitumoral effects in vivo, which were not as evident upon EDP-M and PDP-M treatments. These results were confirmed in a long-term experiment, in which the highest and sustained antitumoral effects were observed for LEDP-M. In summary, liposomal cytostatic substances could represent a promising option that deserves testing in appropriate clinical protocols for the treatment of ACC patients.

CD4+Foxp3+ regulatory T cells prolong drug-induced disease remission in (NZBxNZW) F1 lupus mice

IntroductionThe ability to ameliorate murine lupus renders regulatory T cells (Treg) a promising tool for the treatment of systemic lupus erythematosus (SLE). In consideration to the clinical translation of a Treg-based immunotherapy of SLE, we explored the potential of CD4+Foxp3+ Treg to maintain disease remission after induction of remission with an established cyclophosphamide (CTX) regimen in lupus-prone (NZBxNZW) F1 mice. As a prerequisite for this combined therapy, we also investigated the impact of CTX on the biology of endogenous Treg and conventional CD4+ T cells (Tcon).MethodsRemission of disease was induced in diseased (NZBxNZW) F1 mice with an established CTX regimen consisting of a single dose of glucocorticosteroids followed by five day course with daily injections of CTX. Five days after the last CTX injection, differing amounts of purified CD4+Foxp3+CD25+ Treg were adoptively transferred and clinical parameters, autoantibody titers, the survival and changes in peripheral blood lymphocyte subsets were determined at different time points during the study. The influence of CTX on the numbers, frequencies and proliferation of endogenous Treg and Tcon was analyzed in lymphoid organs by flow cytometry.ResultsApart from abrogating the proliferation of Tcon, we found that treatment with CTX induced also a significant inhibition of Treg proliferation and a decline in Treg numbers in lymphoid organs. Additional adoptive transfer of 1.5 × 106 purified Treg after the CTX regimen significantly increased the survival and prolonged the interval of remission by approximately five weeks compared to mice that received only the CTX regimen. The additional clinical amelioration was associated with an increase in the Treg frequency in the peripheral blood indicating a compensation of CTX-induced Treg deficiency by the Treg transfer.ConclusionsTreg were capable to prolong the interval of remission induced by conventional cytostatic drugs. This study provides valuable information and a first proof-of-concept for the feasibility of a Treg-based immunotherapy in the maintenance of disease remission in SLE.

The Dynamics of Developmental and Tumor Angiogenesis—A Comparison

The blood vasculature in cancers has been the subject of intense interest during the past four decades. Since the original ideas of targeting angiogenesis to treat cancer were proposed in the 1970s, it has become evident that more knowledge about the role of vessels in tumor biology is needed to fully take advantage of such strategies. The vasculature serves the surrounding tissue in a multitude of ways that all must be taken into consideration in therapeutic manipulation. Aspects of delivery of conventional cytostatic drugs, induction of hypoxia affecting treatment by radiotherapy, changes in tumor cell metabolism, vascular leak and trafficking of leukocytes are affected by interventions on vascular function. Many tumors constitute a highly interchangeable milieu undergoing proliferation, apoptosis, and necrosis with abundance of growth factors, enzymes and metabolites. These aspects are reflected by the abnormal tortuous, leaky vascular bed with detached mural cells (pericytes). The vascular bed of tumors is known to be unstable and undergoing remodeling, but it is not until recently that this has been dynamically demonstrated at high resolution, facilitated by technical advances in intravital microscopy. In this review we discuss developmental genetic loss-of-function experiments in the light of tumor angiogenesis. We find this a valid comparison since many studies phenocopy the vasculature in development and tumors.

Regulation of Interferon-Inducible Proteins by Doxorubicin via Interferon γ-Janus Tyrosine Kinase-Signal Transducer and Activator of Transcription Signaling in Tumor Cells

Activation of the immune system is a way for host tissue to defend itself against tumor growth. Hence, treatment strategies that are based on immunomodulation are on the rise. Conventional cytostatic drugs such as the anthracycline doxorubicin can also activate immune cell functions of macrophages and natural killer cells. In addition, cytotoxicity of doxorubicin can be enhanced by combining this drug with the cytokine interferon-γ (IFNγ). Although doxorubicin is one of the most applied cytostatics, the molecular mechanisms of its immunomodulation ability have not been investigated thoroughly. In microarray analyses of HeLa cells, a set of 19 genes related to interferon signaling was significantly over-represented among genes regulated by doxorubicin exposure, including signal transducer and activator of transcription (STAT) 1 and 2, interferon regulatory factor 9, N-myc and STAT interactor, and caspase 1. Regulation of these genes by doxorubicin was verified with real-time polymerase chain reaction and immunoblotting. An enhanced secretion of IFNγ was observed when HeLa cells were exposed to doxorubicin compared with untreated cells. IFNγ-neutralizing antibodies and inhibition of Janus tyrosine kinase (JAK)-STAT signaling [aurintricarboxylic acid (ATA), (E)-2-cyano-3-(3,4-dihydrophenyl)-N-(phenylmethyl)-2-propenamide (AG490), STAT1 small interfering RNA] significantly abolished doxorubicin-stimulated expression of interferon signaling-related genes. Furthermore, inhibition of JAK-STAT signaling significantly reduced doxorubicin-induced caspase 3 activation and desensitized HeLa cells to doxorubicin cytotoxicity. In conclusion, we demonstrate that doxorubicin induces interferon-responsive genes via IFNγ-JAK-STAT1 signaling and that this pathway is relevant for doxorubicin's cytotoxicity in HeLa cells. Immunomodulation is a promising strategy in anticancer treatment, so this novel mode of action of doxorubicin may help to further improve the use of this drug among different types of anticancer treatment strategies.

Radiotherapy and "new" drugs-new side effects?

Background and purposeTargeted drugs have augmented the cancer treatment armamentarium. Based on the molecular specificity, it was initially believed that these drugs had significantly less side effects. However, currently it is accepted that all of these agents have their specific side effects. Based on the given multimodal approach, special emphasis has to be placed on putative interactions of conventional cytostatic drugs, targeted agents and other modalities. The interaction of targeted drugs with radiation harbours special risks, since the awareness for interactions and even synergistic toxicities is lacking. At present, only limited is data available regarding combinations of targeted drugs and radiotherapy. This review gives an overview on the current knowledge on such combined treatments.Materials and methodsUsing the following MESH headings and combinations of these terms pubmed database was searched: Radiotherapy AND cetuximab/trastuzumab/panitumumab/nimotuzumab, bevacizumab, sunitinib/sorafenib/lapatinib/gefitinib/erlotinib/sirolimus, thalidomide/lenalidomide as well as erythropoietin. For citation crosscheck the ISI web of science database was used employing the same search terms.ResultsSeveral classes of targeted substances may be distinguished: Small molecules including kinase inhibitors and specific inhibitors, antibodies, and anti-angiogenic agents. Combination of these agents with radiotherapy may lead to specific toxicities or negatively influence the efficacy of RT. Though there is only little information on the interaction of molecular targeted radiation and radiotherapy in clinical settings, several critical incidents are reported.ConclusionsThe addition of molecular targeted drugs to conventional radiotherapy outside of approved regimens or clinical trials warrants a careful consideration especially when used in conjunction in hypo-fractionated regimens. Clinical trials are urgently needed in order to address the open question in regard to efficacy, early and late toxicity.

AKT inhibition by triciribine alone or as combination therapy for growth control of gastroenteropancreatic neuroendocrine tumors

Up-regulation of phosphatidylinositol-3-kinase (PI3K)-AKT signaling facilitates tumor cell growth and inhibits cell demise. The AKT-pathway also plays an important role in cytostatic therapy resistance and response to hypoxia and angiogenesis. Using real-time cell proliferation assay we examined the potency of triciribine in three distinct neuroendocrine gastrointestinal tumor cell lines. Also we investigated triciribine's induction of apoptosis and effects on a broad range of cancer-associated gene products. Furthermore, we characterized the role of PTEN as a possible predictor of sensitivity to triciribine in GEP-NETs. We also looked for additive anti-neoplastic effects of triciribine when combined with conventional cytostatic drugs or other targeted drugs, affecting different molecules of the PI3K-AKT-pathway and we assessed the potency of triciribine to inhibit tumor growth in vivo, by using the chick chorioallantoic membrane assay. Treatment of insulinoma (CM) or gut neuroendocrine tumor cells (STC-1) with triciribine significantly reduced tumor cell growth by 59% and 65%, respectively. By contrast, the highly expressing PTEN carcinoid cell line BON did not respond, even at higher doses. Combinations of triciribine with classic cytostatic drugs as well as drugs targeting other molecules of the PI3K-AKT-pathway led to synergistic anti-proliferative effects. Additional in vivo-evaluations confirmed the anti-neoplastic potency of triciribine. Thus, our data show that inhibition the AKT-pathway potently reduces the growth of GEP-NET cells alone or in combination therapies. AKT inhibition may provide a rationale for future evaluations.

Lapatinib, a dual inhibitor of ErbB-1/-2 receptors, enhances effects of combination chemotherapy in bladder cancer cells

Survival rate of patients diagnosed with the invasive form of bladder cancer is low suggesting an urgent need to implement novel treatments. GTC (gemcitabine, paclitaxel and cisplatin) is a new chemotherapeutic regimen, which has shown promise in clinical trials. Given that receptor tyrosine kinases of the ErbB family are overexpressed in a high proportion of metastatic bladder tumours, approaches involving small-molecule inhibitors of ErbB receptors in combination with conventional cytostatic drugs are of potential interest. Here, we show that the dual inhibitor of ErbB receptors, lapatinib, enhances cytostatic and induces cytotoxic effects of GTC in two bladder cancer cell lines which differ with regard to expression levels of proteins taking part in the ErbB pathway. Lapatinib inhibited phosphorylation of ErbB receptors and also reduced the level of phosphorylated AKT. Flow cytometry analysis demonstrated that GTC treatment affects cell cycle distribution differently in the presence or absence of lapatinib. In RT112 cells, which express high levels of ErbB receptors and harbour wild-type p53, combined GTC/lapatinib treatment resulted in the phosphorylation of p53 at Ser46 and accumulation of sub-G1 cell populations. Our data indicate that a combinatorial approach involving GTC and lapatinib may have therapeutic potential in a subset of bladder tumours depending on the genetic context.

Roscovitine up‐regulates p53 protein and induces apoptosis in human HeLaS3 cervix carcinoma cells

Exposure of human HeLaS(3) cervix carcinoma cells to high doses of conventional cytostatic drugs, e.g. cisplatin (CP) strongly inhibits their proliferation. However, most cytostatic agents are genotoxic and may generate a secondary malignancy. Therefore, therapeutic strategy using alternative, not cytotoxic drugs would be beneficial. Inhibition of cyclin-dependent kinases (CDKs) by pharmacological inhibitors became recently a promising therapeutic option. Roscovitine (ROSC), a selective CDK inhibitor, efficiently targets human malignant cells. ROSC induces cell cycle arrest and apoptosis in human MCF-7 breast cancer cells. ROSC also activates p53 protein. Activation of p53 tumor suppressor protein is essential for induction of apoptosis in MCF-7 cells. Considering the fact that in HeLaS(3) cells wt p53 is inactivated by the action of HPV-encoded E6 oncoprotein, we addressed the question whether ROSC would be able to reactivate p53 protein in them. Their exposure to ROSC for 24 h induced cell cycle arrest at G(2)/M and reduced the number of viable cells. Unlike CP, ROSC in the used doses did not induce DNA damage and was not directly cytotoxic. Despite lack of detectable DNA lesions, ROSC activated wt p53 protein. The increase of p53 levels was attributable to the ROSC-mediated protein stabilization. Further analyses revealed that ROSC induced site-specific phosphorylation of p53 protein at Ser46. After longer exposure, ROSC induced apoptosis in HeLaS(3) cells. These results indicate that therapy of HeLaS(3) cells by ROSC could offer an advantage over that by CP due to its increased selectivity and markedly reduced risk of generation of a secondary cancer.

Histone deacetylase inhibitor MS-275 alone or combined with bortezomib or sorafenib exhibits strong antiproliferative action in human cholangiocarcinoma cells

To investigate the antiproliferative effect of the histone deacetylase (HDAC) inhibitor MS-275 on cholangiocarcinoma cells alone and in combination with conventional cytostatic drugs (gemcitabine or doxorubicin) or the novel anticancer agents sorafenib or bortezomib. Two human bile duct adenocarcinoma cell lines (EGI-1 and TFK-1) were studied. Crystal violet staining was used for detection of cell number changes. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). Apoptosis was determined by measuring the enzyme activity of caspase-3. Cell cycle status reflected by the DNA content was detected by flow cytometry. MS-275 treatment potently inhibited the proliferation of EGI-1 and TFK-1 cholangiocarcinoma cells by inducing apoptosis and cell cycle arrest. MS-275-induced apoptosis was characterized by activation of caspase-3, up-regulation of Bax and down-regulation of Bcl-2. Cell cycle was predominantly arrested at the G(1)/S checkpoint, which was associated with induction of the cyclin-dependent kinase inhibitor p21(Waf/CIP1). Furthermore, additive anti-neoplastic effects were observed when MS-275 treatment was combined with gemcitabine or doxorubicin, while combination with the multi-kinase inhibitor sorafenib or the proteasome inhibitor bortezomib resulted in overadditive anti-neoplastic effects. The growth of human cholangiocarcinoma cells can be potently inhibited by MS-275 alone or in combination with conventional cytostatic drugs or new, targeted anticancer agents.

The insulin-like growth factor-1 receptor inhibitor PPP produces only very limited resistance in tumor cells exposed to long-term selection

The cyclolignan PPP was recently demonstrated to inhibit the activity of insulin-like growth factor-1 receptor (IGF-1R), without affecting the highly homologous insulin receptor. In addition, PPP caused complete regression of xenografts derived from various types of cancer. These data highlight the use of this compound in cancer treatment. However, a general concern with antitumor agents is development of resistance. In light of this problem, we aimed to investigate whether malignant cells may develop serious resistance to PPP. After trying to select 10 malignant cell lines, with documented IGF-1R expression and apoptotic responsiveness to PPP treatment (IC50s less than 0.1 microM), only two survived an 80-week selection but could only tolerate maximal PPP doses of 0.2 and 0.5 microM, respectively. Any further increase in the PPP dose resulted in massive cell death. These two cell lines were demonstrated not to acquire any essential alteration in responsiveness to PPP regarding IGF-1-induced IGF-1R phosphorylation. Neither did they exhibit any increase in expression of the multidrug resistance proteins MDR1 or MRP1. Consistently, they did not exhibit decreased sensitivity to conventional cytostatic drugs. Rather, the sensitivity was increased. During the first half of the selection period, both cell lines responded with a temporary and moderate increase in IGF-1R expression, which appeared to be because of an increased transcription of the IGF-1R gene. This increase in IGF-1R might be necessary to make cells competent for further selection but only up to a PPP concentration of 0.2 and 0.5 microM. In conclusion, malignant cells develop no or remarkably weak resistance to the IGF-1R inhibitor PPP.

Copper-Complexed Melphalan (MOC*M), a Member of a New Class of Anti-Leukemic and Anti-Tumouric Substances for Treatment of Primary and Relapsed Acute Lymphoblastic Leukemia in Childhood.

Acute lymphoblastic leukemia (ALL) is the most frequent malignant disease of childhood. Despite a relatively good prognosis (survival 80 %), approximately ¼ of the patients suffer from relapses with a much poorer prognosis (survival 40 %). If a complete remission through chemotherapy is not achieved, the patients will not survive. Thus, the search for new cytostatic substances which can break the resistance against conventional cytostatic drugs is of great interest.We developed a new class of copper-containing cytostatic agents with apoptosis-inducing properties. The present study deals with 20 children, who suffer from de novo ALL or relapsed ALL. In vitro measurement of DNA-fragmentation in primary lymphoblasts of the children showed, that the copper-complexed cytostatic drugs are considerably more effective, compared to conventional analogues and other cytostatic drugs (cytarabine p<0.002, vincristine p< 0.006) used against childhood ALL. Furthermore, the new copper-containing analogues overcome drug resistance against doxorubicin (p<0.001) in vitro. In addition, the prototype of copper-complexed drug analogues, MOC*M, a melphalan-copper-acetoacetonate-complex, has synergistic effects in apoptosis induction combined with melphalan or conventional drugs in therapy of ALL in childhood like vincristin, doxorubicin and cytarabine.Experiments revealed that MOC*M specifically induces apoptosis, as evidenced by DNA fragmentation and dissipation of the mitochondrial membrane potential. MOC*M induces cell death, which was functionally characterized by the use of different cellular model systems being devoid of defined molecular parts of the apoptosis machinery. MOC*M triggers apoptosis in a Bcl-2-independent manner in the multi-resistant melanoma cell line MelHO with a 30-fold over-expression of Bcl-2. In vitro and in vivo experiments on mice with tumors sarcom S-180, melanoma B-16 and adenocarcenom in the large intestine proved a high anti-tumor activity of MOC*M with anti-metastasis and immunizing properties without any side effects in kidney or liver. Thus, MOC*M is able to prolong the life of animals with leucosis L-1210 and P-388.We could show that the accumulation of the tritium-labelled MOC*M compounds took place mainly in the tumor cells in vivo. Moreover, MOC*M is also inhibiting glycolysis in the tumor cells.The result of pre-clinical tests with MOC*M preparations, tested on a limited quota of oncological patients with different tumors, was a very large spectrum of anti-tumor and anti-leukemic activities. Further MOC*M has an immense tolerability in vivo. All in all, copper-containing cytostatic drugs comprise an innovative, highly promising class of cytostatic agents for cancer and leukemia therapy, especially for the therapy of relapsed ALL in childhood.

Erlotinib induces cell cycle arrest and apoptosis in hepatocellular cancer cells and enhances chemosensitivity towards cytostatics

Hepatocellular carcinoma (HCC) is one of the most common cancer-related causes of death worldwide. In light of the very poor 5-year-survival new therapeutic approaches are urgently needed. Recently, evidence has been accumulated that the epidermal growth factor receptor (EGFR) is a promising target for cancer therapy. Several reports indicate that EGFRs are expressed frequently in HCC, most likely contributing to the aggressive growth characteristics of these tumors. Erlotinib, an inhibitor of EGFR-tyrosine kinase, potently suppresses the growth of various tumors, but its effect on HCC remains to be explored. We therefore studied the antineoplastic potency of erlotinib in human HCC cells (Huh-7 and HepG2 cell lines). We show that erlotinib inhibited HCC growth in a time- and dose-dependent manner. Moreover erlotinib treatment induced apoptosis and resulted in a dose-dependent arrest at the G1/S checkpoint of the cell cycle. Combining erlotinib with doxorubicin or docetaxel or SN-38 resulted in additive or even synergistic antiproliferative effects. Our data demonstrate that in human HCC cells the inhibition of EGFR-tyrosine kinase by erlotinib induces growth inhibition, apoptosis and cell cycle arrest. Additionally, erlotinib enhances the antineoplastic activity of conventional cytostatic drugs. Thus, inhibiting EGFR-tyrosine kinase appears to be a promising treatment strategy in HCC.