Ehrlich II –2nd World Conference on Magic Bullets

Drug discovery related to vaspin, visceral adipose tissue-derived serine protease inhibitor, a novel adipokine with insulin-sensitizing effects WADA J, NAKATSUKA A, MAKINO H Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Okayama, Japan Background: To delineate the relationship between increased adiposity and insulin resistance in metabolic syndrome, many researchers have identified adipokines. In such adipokines, TNF-, resistin and RBP4 (retinol binding protein-4) cause insulin resistance, while leptin and adiponectin enhance the insulin sensitivity. Otsuka Long-Evans Tokushima fatty (OLETF) rat is an animal model of type 2 diabetes, characterized by abdominal obesity, insulin resistance, hypertension, and dyslipidemia. Differential screening of the genes up-regulated in visceral adipose tissues of obese OLETF rats and down-regulated in non-obese and diabetes-resistant Long-Evans Tokushima Otsuka (LETO) rats led to the identification of vaspin (visceral adipose tissue-derived serine protease inhibitor), which is a member of serine protease inhibitor (serpin) gene family. Rat, mouse and human mature vaspins are made up of 392, 394 and 395 amino acids, exhibit ~40% homology with 1-antitrypsin. Vaspin mRNA is exclusively expressed in visceral adipose tissue in genetically obese rats and also expressed in white adipose tissues of human and its expression is correlated with BMI and insulin sensitivity. Methods: To explore the functional role of vaspin in metabolic syndrome, we prepared recombinant vaspin protein and generated vaspin transgenic (Tg) mice under a control of aP2 promoter. Results: Under high fat-high sucrose (HF) diet, recombinant vaspin-treated DIO and db/db mice, and vaspin Tg mice revealed improved insulin sensitivity. The body weight of Tg mice was ~8% less than wild type (WT) mice under HF diet. And serum leptin levels were significantly lower in Tg mice (2.7±2.9 ng/ml) compared with WT mice (10.9±6.4 ng/ml). Triglyceride accumulation in the liver is diminished in Tg mice rather than in WT mice. There were no differences in food intake and locomoter activity between Tg and WT mice. In liver, mRNA expression of gluconeogenesis (G6Pase, PEPCK) and lipogenesis related genes (SREBP1c, FAS, ACC, SCD) are reduced in Tg rather than WT mice under HF diet. Conclusions: Collectively, vaspin improves insulin sensitivity by acting on insulin target organs and may be a new molecular target in the treatment of metabolic syndrome.	NVP-AEB071: Oral and Specific Inhibitor of T Cell Activation for the Prevention of Graft Rejection and the Treatment of Autoimmune Diseases WAGNER J Novartis Institutes for BioMedical Research, Basel, CH-4002 Switzerland Inhibition of T-cell activation is the most efficient way to prevent transplant rejection. Among the immunosuppressants currently on the market, only calcineurin inhibitors (CNIs) inhibit T-cell activation, but their long term use is associated with side-effects (nephrotoxicity and cardiovascular side effects). NVP-AEB071 is the first LMW inhibitor preventing T-cell activation via a calcineurin-independent pathway. NVP-AEB071 inhibits all classical (,  and ) and novel  and ) protein kinase C isotypes. Herein, we present the case story of NVP-AEB071 including the medicinal chemistry approaches, critical PK properties of the compound, preclinical data including in vivo models in rodents and non-human primates as well as positive proof-of-concept results obtained with NVP-AEB071 in psoriasis patients.
Absorption, Kinetics, Metabolism and Disposition of the Renin Inhibitor Drug Aliskiren WALDMEIER F^1, GLAENZEL U^1, WIRZ B^1, OBERER L^1, SCHMID D^1, SEIBERLING M^2, VALENCIA J^3, RIVIERE GJ^4, END P^1, VAIDYANATHAN S^3 ^1Novartis Pharma AG, Basel, Switzerland; ^2Swiss Pharma Contract, Allschwil, Switzerland; ^3Novartis Pharmaceuticals Corp, East Hanover, New Jersey USA ^4Novartis Pharma SAS, Rueil-Malmaison, France Background: Aliskiren is the first in a new class of orally active, non-peptide direct renin inhibitors developed for the treatment of hypertension. Over decades, efforts to develop clinically effective renin inhibitors failed, often due to low oral bioavailability. Aliskiren was designed based on crystallographic analysis and molecular modelling. After oral bioavailability had been found in animals, clinical development was initiated and clinical efficacy and safety could be shown. Absolute bioavailability in humans was determined as 2.6%. Methods: To elucidate the fate of aliskiren in the human body, an absorption, distribution, metabolism and excretion study was performed in healthy volunteers (n=4) with ^14C-labeled aliskiren. Single doses of 300 mg aliskiren (2.8 MBq) were administered in a aqueous drink solution. Analysis of biological samples was by liquid scintillation counting and accelerator mass spectrometry for ^14C, and LC-MS/MS for aliskiren. Metabolites were analysed using LC-MS/MS and ^1H-NMR. Results: Peak plasma levels of aliskiren (Cmax) were measured between 2 and 5 h post-dose. Unchanged aliskiren represented the principal circulating species in plasma, accounting for 81% of plasma radioactivity (AUC0–∞), and indicating low exposure to metabolites. Terminal half-lives of aliskiren and radioactivity in plasma were 49 and 44 h, respectively. Dose recovery over 168 h was complete (91.5%), with excretion occurring largely via the faecal route, and mainly in the form of unabsorbed, unchanged drug. Mean urinary excretion was 0.6% of dose. The main metabolic pathways were O-demethylations and subsequent side chain oxidation. Conclusions: The exact extent of absorption of aliskiren was not determined. Absorption was cautiously estimated to at least 5% but may well have been higher. Absorbed aliskiren was partly metabolized and eliminated mainly via the hepatobiliary route. Aliskiren is a substrate of pgp. Due to the limited extent of aliskiren biotransformation and since aliskiren does not inhibit CYP enzymes to a relevant degree, aliskiren has a low potential for metabolic drug interactions.	Progesterone and its Metabolites have Functional Effects on Processes other than Pregnancy, such as those involving Stress, Affect, and Cognition WALF AA^1, FRYE CA^1-4 ^1Psychology, ^2Biology, ^3Center for Neuroscience, ^4Center for Life Science Research, Univ. at Albany-SUNY, Albany, NY, USA Background: Although progesterone (P$) and its products, such as 5α-pregnan-3α-ol-20-one (3α,5α-ΤΗP; allopregnanolone), are typically thought of in their role in maintaining pregnancy, P4 and 3α,5α-ΤΗP can enhance a wide variety of other functional processes. There are data from clinical studies and animal models that 3α,5α-ΤΗP can modulate the hypothalamic-pituitary-adrenal axis/stress responses, decrease anxiety or depressive-like behavior, and may even exert some protective effects in neurodegeneration (i.e. epilepsy, Alzheimer’s Disease). We have been investigating the effects and mechanisms of progestins using a bioassay, reproductive behavior (lordosis) of female rodents. We have shown that 3α,5α-ΤΗP has actions in the midbrain ventral tegmental area (VTA) to modulate the intensity and duration of lordosis and actions in the hippocampus to reduce anxiety-like behavior. Furthermore, 3α,5α-ΤΗP increases in midbrain as well as the hippocampus in response to reproductive, as well as stressful/noxious, stimuli. Of interest are the effects of progestins for other hippocampally-mediated processes, such as cognition. Methods: We have conducted studies investigating the effects of progestins in the hippocampus in young and aged rodent models to test the hypothesis that 3α,5α-ΤΗP can have mnemonic effects. In each, the main endogenous source of P4 was removed (the ovaries), P4 or 3α,5α-ΤΗP or placebo vehicle was administered to experimental subjects, and cognitive performance was assessed. Results: We found that young ovariectomized rats or mice, as well as aged mice (which have naturally low progestin levels) administered treatments that enhance 3α,5α-ΤΗP (P4, 3α,5α-ΤΗP), but not those that do not enhance 3α,5α-ΤΗP (placebo vehicle, medroxyprogesterone acetate) have enhanced cognitive performance. In a transgenic mouse model of Alzheimer’s Disease, there were concomitant deficits in hippocampus-mediated processes and 3α,5α-ΤΗP evels following long-term P4 administration, compared to that observed in wildtype mice. Conclusions: These data suggest that progestins can have functional effects beyond their modulation of reproduction and affective behavior to influence mnemonic processes through actions in the hippocampus.
Bioartificial Human Tissues as Model Systems for Pharmaceutical Target Screening and Drug Development WALLES T^1,2, SCHANZ J^2, HAMPEL M^2, MICHAELIS J^2, HANSMANN J^2, MERTSCHING H^2 ^1Schillerhöhe Hospital, Gerlingen, Germany; ^2Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB), Stuttgart, Germany Background: In order to translate the findings from basic research into clinical applications, cell-based models need to recapitulate both the three-dimensional (3D) organization and multicellular complexity of an organ. Tissue engineering provides new perspectives for basic and applied research by offering 3D tissue-cultures resolving fundamental obstacles encountered in currently applied 2D and 3D cell-culture systems, including their lack of vascularization. Affording more detailed insight into the complex interactions in tissue differentiation, carcinogenesis, angiogenesis and stromal reactions they may accelerate the progress in design and development of cancer therapies. Methods: Bioartificial human tissues equipped with a feeding artery, a communicating capillary network and a draining vein were generated by decellularization of porcine jejunal segments and reseeding it with human cells isolated from tissue biopsies. Depending on the intended model system, dermal fibroblasts, hepatocytes, respiratory epithelium, enterocytes or various tumor tissues (carcinoid, pleural mesothelioma, non-small cell lung cancer, lymphangiomatosis) were used for scaffold reseeding following re-endothelialization of the enclosed vascular and capillary network. Tissue differentiation was controlled by histology, immunhistochemistry, cytokine relase, metabolite release, and tissue specific microarrays. In preliminary studies, the metabolic activity of bioartifical human liver-like tissue was characterized. Results: Co-culture conditions for various cell types were successfully developed to generate bioartificial human skin, liver, airway and eventually intestinal tissue. These tissues could be applied for applied research: I) drug diffusion, II) drug resorption, III) drug penetration, IV) circulatory distribution and V) drug metabolization. Using lymphangioma-tumor tissue, a new tumor cell type could be identified. The bioartificial liver tissue was viable for 3 weeks without histological and functional evidence of dedifferentiation. Biochemical testing revealed stable metabolic activity of the tissue culture. The bioarticial airway model showed coordinated cilial activity for more than two weeks. Conclusions: Bioartifical human tissues represent versatile model systems for pharmaceutical target screening and drug development, complying with the European Union’s REACH regulations. However, their effective potential in expediting drug development and testing is subject of ongoing research.	TNF mAbs: Magic bullets for tuberculosis? WALLIS RS Pfizer TNF is central to the pathogenesis of chronic inflammation but is required for host defenses against granulomatous pathogens such as M. tuberculosis. The TNF antibodies infliximab and adalimumab are differentiated from soluble TNF receptor (etanercept) by their efficacy against granulomatous forms of inflammation (e.g., Crohn’s disease), and their 5-10 fold higher high risk of reactivating latent M. tuberculosis infection. We examined the basis of these observations by studying the effects of TNF blockers on TB-induced gene expression in whole blood cultures of 6 healthy tuberculin reactive volunteers. 791 genes were significantly up or downregulated by Mtb, of which some were downregulated by TNF blockers: 75 by infliximab, 60 by adalimumab, and 40 by etanercept (P<.001). All 40 of the etanercept-affected genes were also affected by infliximab and/or adalimumab. Among the genes specifically inhibited by TNF mAbs were IFN, INDO, OAS3, and STAT1. Inhibition of these key immune response genes in TB granulomas may account for the excess risk of reactivation posed by anti-TNF antibodies. The granulomatous response to Mtb contains an infection that cannot be otherwise readily eradicated. However, in TB, this response causes clinical disease manifestations and lung pathology. Granulomas also interfere with the microbiologic response to therapy, preventing drug access and delaying sterilization of sequestered dormant bacilli. The deleterious effects of the granulomatous host response in TB are most apparent in patients with paradoxical worsening precipitated by withdrawal of TNF blockade, in whom TNF-dependent inflammation is restored. We present two such cases of life-threatening paradoxical worsening treated by resuming or starting TNF mAb therapy. In both cases the clinical therapeutic response to anti-TNF therapy was strikingly rapid. In neither case was the microbiologic response to TB therapy adversely affected. Further studies of adjunctive anti-TNF therapy in TB are warranted. Current recommendations for the routine withdrawal of TNF blockade in patients who develop TB should be reconsidered.
Chronic Levonorgestrel Treatment in a Macaque Species (Macaca sylvanus): effects on sex steroids and secondary sex characteristics WALLNER B ^1,2, MÖSTL E ^3, DITTAMI J^1,4 ^1Univ. of Vienna, Vienna, Austria; ^2Dept. of Anthropology; ^3Veterinary Univ. of Vienna, Vienna; Austria; Institute of Biochemistry; ^4Depart. Behavioural Biology Background: Administered levonorgestrel enables contraception under normal cyclicity of the ovaries and does not suppress the development of cyclic perineal swellings. This study investigated the influence of levonorgestrel on fecal gonadal steroid excretion rates and the expression of perineal swelling size. Methods: Two groups of Barbary macaque females were observed: Twenty-four implanted individuals under semifree conditions and five non-implanted individuals under caged conditions. Eight of the implanted females had large expressions of the perinea and sixteen reduced. The non-implanted group had no perineal swellings. To determine the individual steroid excretion rates an enzymeimmunoassay for fecal samples was established. Results: Estradiol excretion rates did not differ in distinctively swollen implanted females, but were increased when compared to non-implanted individuals (df=2; p=0.0002). Implanted females with large perineal swellings had lower progesterone concentrations in the feces compared to individuals with reduced swellings and did not differ from the non-swollen group (df=2; p=0.054). Females with large perineal swellings showed a higher calculated estradiol to progesterone ratio index than the other groups (df=2; p=0.0005). Non-implanted individuals showed increased testosterone excretion rates (df.=2; p=0.0001). Conclusions: The results indicate a positive relationship between the perineal swelling size and levonorgestrel implantation. The ratio of fecal estradiol and progesterone titers can be judged as an endocrine indicator for the expression rate of perineal swelling size.	Antimicrobial Resistance in South Africa: ‘Craving for a Magic Bullet’ WALUBO A, VAN WYK R Department of Pharmacology, University of the Free State, Bloemfontein, South Africa Background: Antibiotic resistance (AR) is a problem in South Africa owing to their wide spread use. Several studies have shown that resistance is of concern in hospitals due to nosocomial infections, but community acquired infections have also exhibited change in the resistance pattern. Also, antibiotic resistance in public health facilities appears to be different from that in private institution. Unfortunately, this information is reported in different articles. Here, we undertake a review and analysis of these reports with a hope that it will improve accessibility and utility in the fight against AR. Methods: A search for relevant abstracts during 1966 to 2007 was done on Medline database using search terms that included: South Africa, antibiotic, resistance and prevalence. The full length articles of the relevant abstracts were evaluated for inclusion in the review. Other relevant articles were obtained from local journals. Results were reported as average prevalence (%) of AR with time or to multiple antibiotics. Results: Thirty-four abstracts were recovered and, of these, 9 articles qualified to be used in this review. In survey of 7 academic hospitals (2001-2004), the prevalence of MRSA was 46.4%, while in a 6 month study of 12 private laboratories, it was 36%. The prevalence of Penicillin-resistant pneumococci (PRP) was 45% in 1997, having risen from 31.3% in 1996. In another report, the prevalence of PRP in community acquired Lower Respiratory Tract Infections increased from 29.4% in 1996 to 35.8% in 1997, while the prevalence of β-lactamase producing H. influenzae in one academic hospital rose from 33% in 2001 to 40% in 2003. Regarding multiple AR the prevalence was gentamycin 45.6% and ciprofloxacin 11.3%, while that of Ps. aeruginosa it was; meropenem 42%, imipenem 45%, cefepime 53% and ciprofloxacin 46%. Conclusions: 1) The prevalence of AR in South Africa is very high (> 20%), on an upward trend, and multiple AR is on the increase. 2) There was increased use of the newer antibiotics such as moxofloxacin, levofloxacin, telithromycin for community acquired infections, and the meropenem, linezolide and vancomycin for nosocomial infections, and this has lead to emergence of resistant strains to these drugs. 3) There is a need for new and more effective antibiotics before we run out of options. In effect, South Africa is craving for a Magic Bullet.
Therapeutic protein engineering via the incorporation of non‐natural amino acids WANG A, NAIRN N, GRADDIS T, SHANEBECK K, THORNTON K, GRABSTEIN K Allozyne Corporation, 1600 Faireview Ave E, Suite 300, Seattle, WA 98102 Incorporation of unnatural amino acids into recombinant proteins represents a powerful tool for protein engineering and protein therapeutic development. The presence of the unnatural amino acid in recombinant protein enables site-specific modification of protein at these unnatural amino acids. For example, site-specific pegylation of protein extends the in vivo half-life of therapeutic protein, while site-specific conjugation of antibody to toxin has long been regarded as “guided missile” in treating cancer patients. In this study, we have engineered human interferon-beta protein with two unnatural amino acids, L-azidohomoalanine (AHA) and L-homopropargylglycine (HPG). We report the effects of the penultimate residue (the residue after the initiator Met) on the processing of AHA and HPG, at the N-terminus of recombinant human interferon-beta in E. coli. We have identified specific amino acids at the penultimate position that can be used to efficiently retain or remove N-terminal AHA or HPG. Retention of N-terminal AHA or HPG can be achieved by choosing amino acids with large side-chains (such as Gln, Glu and His) at the penultimate position, while Ala can be selected for the removal of N-terminal AHA or HPG. We also report site-specific pegylation at AHA site and characterization of pegylated IFN-beta protein.	The treatment of patients with multi-drug resistant cavitary pulmonary tuberculosis with gelatin containing anti-tuberculosis medicines by fiberbronchoscope WANG A*, WANG W, LIN M, CHENG H, LI S Institute of Tuberculosis Research, the Second Affliated Hospital of Chinese PLA General Hospital, Beijing100091, China Background: The situation of tuberculosis (TB) and drug resistance were severe in China. The emergence of multidrug-resistant M. tuberculosis (MDR-TB) strains has made the treatment of TB (specially cavitary pulmonary TB) become more difficult. The standard chemotherapy for them needs longer curable duration. The goal of this paper is to describe the effect of local treatment of MDR-cavitary pulmonary TB by fiberbronchoscope. Methods: Two hundredes and twenty-three patients with MDR- cavitary pulmonary TB were treated with the same standard chemotherapeutic scheme. They were divided into two groups: control group and interposition group. The control group (containing 37 patients) was treated only with medication, while interposition group (containing 186 patients) was treated in combination with gelatin containing Dipasic, streptomycin, Pyrazinamide, and Levofloxacin by fiberbronchoscope. The clinical curative effects were observed for 6 months. Results: In the interposition group at the end of six-month therapy, the sputum negative conversion rate was 73.1%, the lesion marked absorption rate was 85.4%, and cavity closing rate was 81%, which were higher than that of the controls (51.3 %, 56.7% and 51.4%, P < 0.05). The time of sputum negative conversion was 36.3 days in interposition group, which was shorter than that of the controls (61.8 days, P < 0.01). There was not severe adverse reaction in interposition group. Conclusion: The efficiency of the chemotherapy combined with local treatment by fiberbronchoscope is better than the routine chemotherapy for the MDR-cavitary pulmonary TB.
On the Delivery of Carmustine, Paclitaxel, and Etanidazole to Brain Tumors: An integrated study on the novel fabrication methods of pharmaceutical particles and 3-D computer simulations for chemotherapy and radiotherapy applications WANG CH Department of Chemical and Biomolecular Engineering, National University of Singapore Conventional treatment of brain tumor involves excising the main part of the tumor in conjunction with post-surgery treatments, such as chemotherapy, radiotherapy, or a combination of both. One of the difficulties associated with such treatment is that the tumor tissue cannot be completely removed without the risk of cutting off neighboring healthy normal tissue. In addition, the tumor that remains behind is capable of rapid multiplication and encroachment into nearby healthy tissues. In traditional chemotherapy, anti-cancer agents are delivered systemically to the malignant site via systemic administration to kill the cells. However, the presence of high interstitial pressure within the tumor's centre further poses severe problems to chemotherapy via systemic administration [1]. For effective radiotherapy, the patients are subjected to a scheduled course of repeated radiation to destroy the remnant tumor cells. The present study is undertaken to investigate the optimal way of drug administration to tumors via the combination of chemotherapy and radiotherapy. The study consists of two major parts: In the first part, controlled drug release devices are developed in the dosage forms of microparticles and disc wafers of biodegradable polymers PLGA [poly(d,l-lactide-co-glycolide) and PLA [poly(l-lactide)]. In the second part, computational fluid dynamics (CFD) simulations are used to analyze the spatial and temporal variations of drug concentration. The efficiencies of different ways of drug administration are compared among a variety of anticancer and radiosensitizer agents and drug-polymer systems. The first part of this study illustrates the fabrication of PLGA polymeric particles by electrohydrodynamic atomization (EHDA) for applications in sustained delivery of anticancer drug - paclitaxel to treat C6 glioma cells in vitro and in vivo. The differential scanning calorimetry study indicated that paclitaxel could be either in an amorphous or disordered-crystalline phase of a molecular dispersion or a solid solution state in the polymer matrix after fabrication. The X-ray photoelectron spectroscopy result suggested that some amount of paclitaxel could exist on the surface layer of the microparticles. The encapsulation efficiency was around 80% and more than 30 days in vitro sustained release profile could be achieved. Cell cycling results suggested that paclitaxel after encapsulation by EHDA could keep its biological function and inhibit C6 glioma cells in G2/M phase. The cytotoxicity of paclitaxel-loaded biodegradable microparticles to C6 glioma cells could be higher than Taxols(r) in the long-term in vitro tests evaluated by MTS assay. The drug delivery devices developed by EHDA in this study could be promising for the local drug delivery to treat malignant glioma. This work also examines the in vivo drug release profile and anti-tumor responses of BALB/c nude mice, bearing C6 glioma tumors subcutaneously, to treatments by PLGA microspheres, microparticles and discs-delivering Paclitaxel and Etanidazole. The in-vivo experimental results are used to correlate the efficacy of treatment to in vitro release profiles from the various formulations. Our study demonstrates that radio-sensitizing effects during irradiation could be achieved by double burst profiles from Etanidazole-loaded discs, when compared to controls 17 days after implantation despite the short half-life of Etanidazole (1.4 h) in vivo. These results also showed inhibited tumor growth on tumor volumes of 59%, 65% and 70% over the blank placebo groups after 21 days of tumor growth for spray-dried microspheres, EHDA microparticles and spray-dried discs, respectively [2,3,4]. The second part of this paper further reports the development of three-dimensional computer simulation models to study the effect of various factors on the delivery of carmustine, paclitaxel and etanidazole to brain tumors for integrated chemotherapy and radiotherapy applications. The study yields information on the efficacy of various delivery methods, and the optimal location of polymer implantation. Two types of drug deliveries, namely, systemic administration and controlled release from polymers, were simulated to predict the temporal and spatial variation of drug distribution. The simulation was carried out using CFD simulations with the model geometry constructed from magnetic resonance images (MRI) with reference to the Gliadel(r) wafers application [5]. The simulation results show that polymer-based delivery provides higher mean concentration, longer carmustine exposure time and reduced systemic toxicity than bolus injection. Polymer implanted in the core gives higher concentration of drug in both the core and viable zone than the polymer in the viable zone case. The implantation of carmustine/ polymer matrix at the lumen of the viable zone immediately following the surgical removal of 80% of the tumor may be an effective treatment for the chemotherapy of brain tumors. Removal of the tumor core by surgery and subsequent insertion of drug-carrying polymers in the resection cavity may further improve the treatment. The operation establishes a favourable pressure gradient towards the centre of the tumor and thus creates flow reversal immediately after the operation. The presence of post-surgery edema increases the interstitial pressure and fluid velocity, thus causing higher relative toxicity in the surrounding normal tissues. The CFD model is also extended to radiotherapy applications for analyzing the penetration depth of Etanidazole in tumor impanted with PLGA wafers in the resected cavity [6,7,8,9,10].	Nucleotide Excision Repair (NER) in cisplatin-induced cellular responses WANG G Institute of Environmental Health Sciences, Wayne State University, 2727 Second Avenue, Room 4325, Detroit, MI 48201 Cisplatin is an important anticancer drug that has been used in the treatment of many types of cancer. Cisplatin binds to the DNA template to form both intra- and inter-strand crosslinks (ICL). Recognition of this ICL damage can eventually lead to apoptotic cell death, which is an important mechanism for cisplatin in its anticancer action. Nucleotide excision repair (NER) plays an important role in removing DNA damage generated by cisplatin. The results obtained from our studies reveal that the DNA damage recognition signal initiated by XPC protein, an important DNA damage recognition protein for the NER, is essential for cisplatin-induced cellular responses such as cell cycle arrest and apoptosis. The DNA damage recognition signal of XPC protein is required for cisplatin-induced p53 phosphorylation, while the XPC-TFIIH complex formation plays a key role in the p53 phosphorylation. The phosphorylated p53 protein further regulates transcriptions of a series of downstream target genes to result in cell cycle arrest and/or apoptosis. Furthermore, the process of cisplatin DNA damage by NER also causes activation of the ATM protein, which then induces transcription of an important anti-apoptotic bcl-xl gene through NF-B, resulting in increased accumulation of Bcl-x(L) and subsequent cell survival under cisplatin treatment. Therefore, the NER possesses two very distinct roles in the cisplatin-induced cellular responses: (1) the DNA damage recognition signal initiated by the XPC protein is essential for cisplatin-induced cell cycle arrest and apoptosis; and (2) the NER process of cisplatin DNA damage is required for ATM activation and cell survival under cisplatin treatment. Therapeutic manipulations that enhance the DNA damage recognition-induced cell cycle arrest and apoptosis and repress the NER process-mediated ATM activation and cell survival will significantly improve the effectiveness of cisplatin in anticancer treatment and reduce tumor cell resistance to cisplatin.