Low prevalence of SV40 in Swiss mesothelioma patients after elimination of false-positive PCR results

The association of simian virus 40 (SV40) with malignant pleural mesothelioma is currently under debate. In some malignancies of viral aetiology, viral DNA can be detected in the patients' serum or plasma. To characterize the prevalence of SV40 in Swiss mesothelioma patients, we optimized a real-time PCR for quantitative detection of SV40 DNA in plasma, and used a monoclonal antibody for immunohistochemical detection of SV40 in mesothelioma tissue microarrays. Real-time PCR was linear over five orders of magnitude, and sensitive to a single gene copy. Repeat PCR determinations showed excellent reproducibility. However, SV40 status varied for independent DNA isolates of single samples. We noted that SV40 detection rates by PCR were drastically reduced by the implementation of strict room compartmentalization and decontamination procedures. Therefore, we systematically addressed common sources of contamination and found no cross-reactivity with DNA of other polyomaviruses. Contamination during PCR was rare and plasmid contamination was infrequent. SV40 DNA was reproducibly detected in only 4 of 78 (5.1%) plasma samples. SV40 DNA levels were low and not consistently observed in paired plasma and tumour samples from the same patient. Immunohistochemical analysis revealed a weak but reproducible SV40 staining in 16 of 341 (4.7%) mesotheliomas. Our data support the occurrence of non-reproducible SV40 PCR amplifications and underscore the importance of proper sample handling and analysis. SV40 DNA and protein were found at low prevalence (5%) in plasma and tumour tissue, respectively. This suggests that SV40 does not appear to play a major role in the development of mesothelioma.

Enhanced detection of EGFR mutations in plasma from non-small cell lung cancer (NSCLC) patients using Scorpion primers

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Background: Activating epidermal growth factor receptor (EGFR) mutations identified in NSCLC patient tumors are often associated with rapid and profound response to EGFR tyrosine kinase inhibitors (TKIs). Conventional detection methods are cumbersome and may underestimate mutations frequencies due to limited sensitivity. We and others have shown that tumor-specific mutations such as KRAS can be detected in tumor DNA shed into patient plasma (Kimura, Ann N Y Acad Sci, 2004). Here we describe the performance of an allele- specific real-time PCR system utilizing Scorpion primers (kindly provided by DxS, UK) to detect EGFR mutations in plasma. Methods: DNA was extracted from archival tumor blocks, slides and plasma obtained from consenting patients. In order to determine the sensitivity of this technique both in terms of the ratio of mutant-to-wild-type genomic DNA as well as the minimum amount of DNA required for detection, a dilution experiment was conducted. Genomic DNA from cell lines containing either the exon 21 L858R point mutation or the exon 21 E746–750 deletion was diluted with wild-type genomic DNA at ratios ranging from 1:2 to 1:10,000. Clinical specimens including plasma and/or tissue from 35 advanced stage NSCLC patients treated with EGFR-TKIs were examined. Results: Mutant DNA was successfully detected when it comprised as little as 0.1% of the total sample or as low as 25 pg of mutant-positive genomic DNA in a pool of 2.5 μg of total DNA. EGFR mutations were identified by this approach in both plasma and tissue of 2 patients who were complete responders to EGFR-TKI therapy, only one of which was detectable by direct sequencing. For the 7 patients where only tissue was available, two were positive both with the Scorpion primers and direct sequencing while the rest were wild-type. Of 21 patients where only plasma was available, 6 mutations were detected using the Scorpion primers. Conclusions: Allele-specific Scorpion technology is 1) highly specific and sensitive for EGFR mutation analysis, 2) able to detect mutations that were not observable by direct sequencing in plasma and tissue, 3) capable of detecting mutations in shed tumor DNA in plasma of advanced NSCLC patients and 4) may be suitable for monitoring response or detecting recurrence.

No significant financial relationships to disclose.

Epidermal growth factor receptor inhibitors plus chemotherapy in non-small-cell lung cancer: biologic rationale for combination strategies

Chemotherapy continues to play an essential role in the treatment of most stages of non-small-cell lung cancer (NSCLC). In fact, within the past 5 years, this role has greatly expanded into adjuvant therapy for early-stage resected disease. Likewise, agents targeting the epidermal growth factor receptor (EGFR), particularly the tyrosine kinase inhibitors gefitinib and erlotinib, have proven to be clinically active in patients with advanced-stage NSCLC. Because of these findings, it is logical to expect that combinations of these 2 classes of antineoplastic agents would prove more efficacious than either one alone. Yet 4 large randomized phase III trials of chemotherapy with or without an EGFR tyrosine kinase inhibitor in unselected patients with advanced-stage NSCLC, altogether totaling > 4000 patients, did not demonstrate improvement in clinical outcomes with the combination. Whether these negative results will be reproduced in ongoing combination studies of chemotherapy plus monoclonal antibodies directed against EGFR remain to be determined. Herein, we review recent preclinical and clinical data addressing this topic and explore the biologic rationale for developing new combination strategies based on patient selection by molecular and clinical factors, or by pharmacodynamic parameters.

Origin and prognostic value of circulating KRAS mutations in lung cancer patients

Because of the current controversy on the origin and clinical value of circulating KRAS codon 12 mutations in lung cancer, we screened 180 patients using a combined restriction fragment-length polymorphism and polymerase chain reaction (RFLP-PCR) assay. We detected KRAS mutations in 9% plasma samples and 0% matched lymphocytes. Plasma KRAS mutations correlated significantly with poor prognosis. We validated the positive results in a second laboratory by DNA sequencing and found matching codon 12 sequences in blood and tumor in 78% evaluable cases. These results support the notion that circulating KRAS mutations originate from tumors and are prognostically relevant in lung cancer.

Cyclin D1 in non-small cell lung cancer: a key driver of malignant transformation

PURPOSE

To review the evidence implicating the deregulation of cyclin D1 in the pathogenesis of non-small cell lung cancer (NSCLC), and to discuss the opportunities for targeted clinical intervention.

METHODS

Data published until June 2006 are summarized, and previously unpublished results from our own research are included.

RESULTS

In normal cells, cyclin D1 complexes with and activates cyclin-dependent kinases (CDK) and acts as a transcriptional regulator. The protein is frequently overexpressed in a wide range of cancers, sometimes coincident with CCND1 (cyclin D1) gene amplification (5-20% of tumours). A low level of somatic mutations have been seen in certain tumours. CCND1 is amplified in NSCLC and cyclin D1 is frequently overexpressed in tumours and pre-invasive bronchial lesions, generally from one parental allele. Mutation analyses revealed a frequent CCND1 gene polymorphism (A870G) that modulates alternative splicing and allows expression of an alternative cyclin D1 transcript (transcript cyclin D1b). The encoded cyclin D1b protein lacks a specific phosphorylation site required for nuclear export. Genotype has been correlated with the risk and/or severity of disease or drug response across a range of malignancies, including lung cancer. Together, these findings suggest a strong pathological role for cyclin D1 deregulation in bronchial neoplasia.

CONCLUSION

Current data indicate that cyclin D1 overexpression is not a consequence of, but rather a pivotal element in the process of malignant transformation in the lung and other tissues. This understanding may open new avenues for lung cancer diagnosis, treatment and prevention.

Aurora Kinase Inhibitors: A New Class of Targeted Drugs in Cancer

Aurora kinases (A, B, and C) are essential for spindle assembly, centrosome maturation, chromosomal segregation, and cytokinesis. Aurora kinases A and B are overexpressed in many cancers, including non-small-cell lung cancer and mesothelioma. Small-molecule inhibitors selective for aurora kinases have shown promising activity in preclinical tumor models. To date, phase I studies with aurora kinase inhibitors have shown that myelosuppression is the dose-limiting toxicity, and disease stabilization was achieved in a number of tumor types, including non-small-cell lung cancer. Phase II trials are under way in selected tumor types. This article reviews the biology of aurora kinases, their potential role in the treatment of lung cancer, and challenges in the clinical development of this unique class of antineoplastic agents.

Preclinical evaluation of the dual specific Src/Abl kinase inhibitor AZD0530 in lung cancer

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Background: AZD0530 is a highly selective, orally available, dual specific Src/Abl kinase inhibitor in clinical development. We tested this agent in multiple lung cancer cell lines in vitro. We hypothesized that activity of AZD0530 may depend on the level of activated (pY416-)Src, and that Src inhibition may decrease Bcl-xL protein levels and lower the barrier to apoptosis. Methods: NSCLC (A549, Calu-1, Calu-6) and SCLC (H69, H526) cells were incubated with 0.001–100 μM AZD0530 for 1–72hrs. Proliferation (MTT), DNA-content (flow cytometry), and protein levels of Src, pY416-Src, PARP, and Bcl-xL (Western blotting) were assessed. Results: Basal pY416-Src was detectable in most cell lines except H526. AZD0530 decreased pY416-Src levels at submicromolar concentrations in pY416-Src positive cells. In A549, Calu-1 and Calu-6, AZD0530 blocked cell growth in a time- and dose-dependent way (IC50 = 7–25 μM) by arrest in G1, retaining a cytostatic effect at submicromolar concentrations in A549 and Calu-1. AZD0530 induced apoptosis in 10–22% of these cells at micromolar concentrations, accompanied by a decrease of Bcl-xL protein in A549 and Calu-1. In H69 and H526, growth inhibition by AZD0530 was limited (IC50 >100 μM). Conclusions: 1) AZD0530 induced apoptosis at micromolar concentrations, and inhibited cell growth at micromolar to submicromolar concentrations in some cell lines. 2) pY416-Src is a potential marker for drug responsiveness, but other factors should also be tested. 3) Decrease of Bcl-xL by AZD0530 may render cancer cells more sensitive to chemotherapy. These data suggest that Src kinase inhibitors merit further testing in lung cancer, both alone and in combination with other agents. (Support: Swiss National Science Foundation, Swiss Cancer League, AstraZeneca).

[Table: see text]

Clinical Development of Src Tyrosine Kinase Inhibitors in Lung Cancer

Src tyrosine kinases regulate a large number of important mechanisms in normal and cancerous cells, are overexpressed in a broad range of tumors including lung cancer, and thus represent a potential target for cancer therapy. Preclinical experiments indicate that small-molecule inhibitors of Src block tumor growth, metastasis, and angiogenesis. Phase I data from healthy volunteers also suggest that inhibitors of Src prevent bone resorption. Several phase II trials with small-molecule inhibitors of Src are under way or have been initiated in lung cancer and in other malignancies, as discussed herein.

Cyclin D1 (CCND1) A870G gene polymorphism modulates smoking-induced lung cancer risk and response to platinum-based chemotherapy in non-small cell lung cancer (NSCLC) patients

PURPOSE

The cyclin D1 (CCND1) A870G gene polymorphism is linked to the outcome in patients with resectable non-small cell lung cancer (NSCLC). Here, we investigated the impact of this polymorphism on smoking-induced cancer risk and clinical outcome in patients with NSCLC stages I-IV.

METHODS

CCND1 A870G genotype was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (RFLP) of DNA extracted from blood. The study included 244 NSCLC patients and 187 healthy control subjects.

RESULTS

Patient characteristics were: 70% male, 77% smokers, 43% adenocarcinoma, and 27% squamous cell carcinoma. Eighty-one percent of the patients had stages III-IV disease. Median age at diagnosis was 60 years and median survival was 13 months. Genotype frequencies of patients and controls both conformed to the Hardy Weinberg equilibrium. The GG genotype significantly correlated with a history of heavy smoking (>or=40 py, P=0.02), and patients with this genotype had a significantly higher cigarette consumption than patients with AA/AG genotypes (P=0.007). The GG genotype also significantly correlated with tumor response or stabilization after a platinum-based first-line chemotherapy (P=0.04). Survival analysis revealed no significant differences among the genotypes.

CONCLUSION

Evidence was obtained that the CCND1 A870G gene polymorphism modulates smoking-induced lung cancer risk. Further studies are required to explore the underlying molecular mechanisms and to test the value of this gene polymorphism as a predictor for platinum-sensitivity in NSCLC patients.

Overexpression of aurora B kinase (AURKB) in primary non-small cell lung carcinoma is frequent, generally driven from one allele, and correlates with the level of genetic instability

Aurora kinases are key regulators of chromosome segregation during mitosis. We have previously shown by microarray analysis of primary lung carcinomas and matched normal tissue that AURKB (22 out of 37) and AURKA (15 out of 37) transcripts are frequently over-represented in these tumours. We now confirm these observations in a second series of 44 carcinomas and also show that aurora B kinase protein levels are raised in the tumours compared to normal tissue. Elevated levels of expression in tumours are not a consequence of high-level amplification of the AURKB gene. Using a coding sequence polymorphism we show that in most cases (seven out of nine) tumour expression is predominantly driven from one AURKB allele. Given the function of aurora B kinase, we examined whether there was an association between expression levels and genetic instability. We defined two groups of high and low AURKB expression. Using a panel of 10 microsatellite markers, we found that the group showing the higher level of expression had a higher frequency of allelic imbalance (P=0.0012). Analysis of a number of other genes that are strongly and specifically expressed in tumour over normal lung, including SERPINB5, TERT and PRAME, showed marked allelic expression imbalances in the tumour tissue in the context of balanced or only marginally imbalanced relative allelic copy numbers. Our data support a model of early carcinogenesis wherein defects in the process of inactivation of lung stem-cell associated genes during differentiation, contributes to the development of carcinogenesis.

Circulating deoxyribonucleic Acid as prognostic marker in non-small-cell lung cancer patients undergoing chemotherapy

PURPOSE

Circulating cell-free DNA is present in increased amounts in the blood of cancer patients, but the clinical relevance of this phenomenon remains unclear. We conducted a clinical study to assess the value of circulating DNA as a prognostic marker in patients with non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

A standard protocol for the quantification of circulating DNA by real-time polymerase chain reaction was set up and validated at two oncology units. One hundred eighty-five informed patients with NSCLC and 46 healthy controls were included in the study. DNA concentrations were determined in paired plasma and serum samples and analyzed for a relationship with leukocyte counts and lactate dehydrogenase (LDH) levels. DNA concentrations in healthy controls and in patients were compared, and cutoff levels for plasma and serum DNA were determined. Patient survival was analyzed relative to baseline DNA concentrations, and the relationship between tumor responses and changes in DNA concentrations was assessed in patients receiving chemotherapy.

RESULTS

We found a significant correlation between increased plasma DNA concentrations and elevated LDH levels (P = .009), advanced tumor stage (P < .003), and poor survival (P < .001). Tumor progression after chemotherapy was significantly (P = .006) associated with increasing plasma DNA concentrations. Serum DNA concentrations strongly correlated (P < .001) with leukocyte counts.

CONCLUSION

Our data demonstrate that quantification of plasma DNA is an accurate technique amenable to standardization, which might complement current methods for the prediction of patient survival. This approach might be considered for evaluation in large prospective studies.

Molekulare Therapie beim Lungenkarzinom

In den letzten Jahren wurden bedeutende Fortschritte in der Erforschung der Tumorbiologie gemacht. Dies führte zur Entwicklung von neuen Substanzen, die gezielt in molekulare Prozesse eingreifen und das Verhalten von Tumorzellen beeinflussen können. Bei Patienten mit fortgeschrittenem Lungenkarzinom wurden bereits einige solche molekularen Therapieansätze geprüft, zum Teil mit Erfolg. Dieser Artikel gibt einen Einblick in den gegenwärtigen Stand der klinischen Forschung und beschreibt erste Erfahrungen mit den am weitesten entwickelten Substanzen.

Successful treatment of chemotherapy-refractory Sézary syndrome with alemtuzumab (Campath-1H)

INTRODUCTION

Sézary syndrome (SS) is a cutaneous T-cell lymphoma characterized by erythroderma, lymphadenopathy and circulating atypical T cells. Median survival after diagnosis is 10 yr, with chemotherapy resistance being a major problem in advanced disease. Alemtuzumab (Campath-1H) is a monoclonal antibody directed against the lymphocytic antigen CD52, expressed on B- and T-cells. Alemtuzumab is approved for relapsing chronic B-cell leukemia and seems to be active also in T-cell lymphomas such as T-cell prolymphocytic lymphoma, SS and mycosis fungiodes.

CASE HISTORY

A 32-yr-old male patient presented with advanced stage, extensively pretreated SS with heavily itching erythroderma, peripheral lymphadenopathy, circulating Sézary cells and bone marrow infiltration. The disease had not responded to PUVA/interferon-alpha and progressed on chemotherapy with CHOP, 2-CDA, vinorelbine, etoposide and liposomal doxorubicin. Following treatment with alemtuzumab (30 mg i.v. three times per week for 10 wk), itching resolved rapidly and an almost complete remission was achieved within 3 months after starting this treatment. At 12-month follow up, no disease progression was present.

CONCLUSION

In accordance with previous data, this single case underlines the potent activity of alemtuzumab in advanced, chemotherapy-refractory SS.

Acute Respiratory Failure and Cerebral Hemorrhage due to Primary Epstein-Barr Virus Infection

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus with worldwide distribution. Primary infection with EBV occurs early in life and typically presents as infectious mononucleosis. The usual course of the disease is benign and most patients recover uneventfully. Severe infections are reported particularly in immunocompromised patients. Mild, asymptomatic pneumonitis is reported in about 5-10% of cases of infectious mononucleosis, but severe pneumonitis with hypoxemia is very rare in immunocompetent individuals. We report a young female adolescent in whom an acute EBV infection led to severe bilateral pneumonitis, a systemic inflammatory response and intracerebral bleeding. The clinical course and results of quantitative viral DNA determinations in plasma are presented.

Persistent polyclonal B-cell lymphocytosis is an expansion of functional IgD(+)CD27(+) memory B cells

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare disorder of unknown aetiology affecting predominantly young to middle-aged women. It is characterized by a polyclonal expansion of B cells, including typical binucleated lymphocytes, and is associated with the presence of the translocation t(14;18), involving the bcl-2 oncogene. The stage of differentiation of the B cells expanded in PPBL is not known. We analysed the immunophenotype of the expanded B-cell subset in five new patients with PPBL and found a large uniform expansion of a recently defined human memory B-cell population, IgD(+)CD27(+) memory B cells. After in vitro stimulation with interleukin 2 (IL-2) and Staphylococcus aureus Cowan strain I, B cells from PPBL patients produced high levels of IgM immunoglobulins, which is a characteristic feature of IgD(+)CD27(+) memory B cells. Using a quantitative real-time polymerase chain reaction method, we found a high frequency of the translocation t(14;18) in the range of 1000-3000 per 106 B cells in PPBL patients. In contrast, a much smaller number of cells with a t(14;18) was found in B cells from healthy individuals. Our finding that PPBL is an accumulation of memory B cells further suggests that chronic antigeneic stimulation plays an important part in the pathogenesis of this disorder. This IgD(+)CD27(+) memory B-cell population might harbour a certain number of 'physiological' t(14;18) translocations that increases as this population expands in PPBL patients and constitutes the majority of peripheral blood lymphocytes.

Activity of a novel bcl-2/bcl-xL-bispecific antisense oligonucleotide against tumors of diverse histologic origins

BACKGROUND

Increased expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL is involved in the development and progression of many tumors. We recently reported that the bcl-2/bcl-xL-bispecific antisense oligonucleotide 4625 induces apoptosis in lung carcinoma cells. To further assess the therapeutic potential of oligonucleotide 4625, we investigated its effect on a series of human tumor cell lines of diverse histologic origins in vitro and in vivo.

METHODS

Oligonucleotide 4625-mediated inhibition of bcl-2 and bcl-xL expression in vitro was measured in breast carcinoma cells with the use of reverse transcription-polymerase chain reaction (PCR), real-time PCR, and western blotting. Cytotoxicity was assessed in several different cell lines by measurement of tumor cell growth, propidium iodide uptake, and nuclear apoptosis. The in vivo activity of oligonucleotide 4625 was determined by the inhibition of growth of established tumor xenografts in nude mice, immunohistochemical staining of Bcl-2 and Bcl-x proteins in the tumors, and western blotting of tumor lysates. Apoptosis in tumor xenografts was detected with the use of in situ TUNEL (i.e., terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick end labeling) staining. All statistical tests are two-sided.

RESULTS

In breast carcinoma cells, oligonucleotide 4625 treatment reduced bcl-2 and bcl-xL messenger RNA levels in a dose-dependent manner. At 600 nM:, oligonucleotide 4625 reduced Bcl-2 and Bcl-xL protein levels to 25% (95% confidence interval [CI] = 16% to 34%) and 20% (95% CI = 14% to 26%), respectively, of the levels in untreated cells and it decreased viability in all cell lines mainly by inducing apoptosis. In vivo, oligonucleotide 4625 statistically significantly inhibited the growth of breast and colorectal carcinoma xenografts by 51% (95% CI = 28% to 74%) and 59% (95% CI = 44% to 74%), respectively, relative to those treated with control oligonucleotide 4626; it also reduced Bcl-2 and Bcl-xL protein levels and induced tumor cell apoptosis.

CONCLUSION

The bcl-2/bcl-xL-bispecific antisense oligonucleotide 4625 merits further study as a novel compound for cancer therapy.

Bcl-xl antisense treatment induces apoptosis in breast carcinoma cells

Upregulated expression of bcl-xL is involved in the initiation and progression of breast cancer by inhibiting tumor cell apoptosis. Here we describe the use of the 2;-O-methoxy-ethoxy antisense oligonucleotide 4259 targeting nucleotides 687-706 of the bcl-xL mRNA, a sequence that does not occur in the pro-apoptotic bcl-xS transcript, to restore apoptosis in estrogen-dependent and independent breast carcinoma cells. The antisense effect of oligonucleotide 4259 was examined on the mRNA and protein level using real-time PCR and Western blot analysis, respectively, and the induction of cell death was investigated in viability and apoptosis assays. Treatment of MCF7 cells with oligonucleotide 4259 at a concentration of 600 nM for 20 hr decreased bcl-xL mRNA and protein levels by more than 80% and 50%, respectively. This resulted in the induction of apoptosis characterized by mitochondrial cytochrome c release, decrease of mitochondrial transmembrane potential, and the appearance of condensed nuclei in approximately 40% of cells. Moreover, oligonucleotide 4259 efficiently downregulated bcl-xL expression and decreased cell growth in the breast carcinoma cell lines T-47D, ZR-75-1, and MDA-MB-231. Our data emphasize the importance of bcl-xL as a survival factor for breast carcinoma cells and suggest that oligonucleotide 4259 deserves further investigations for use in breast cancer therapy.

A novel bispecific antisense oligonucleotide inhibiting both bcl-2 and bcl-xL expression efficiently induces apoptosis in tumor cells

Bcl-2 and Bcl-xL are inhibitors of apoptosis frequently overexpressed in solid tumors. The bcl-2 and bcl-xL mRNAs share a region of homology comprising nucleotides 605-624 and 687-706, respectively, which differs by only three nucleotides. This sequence does not occur in the proapoptotic splice variant bcl-xS. To test the possibility that oligonucleotides targeting this region have the potential to down-regulate bcl-2 and bcl-xL expression simultaneously, three 2'-O-methoxy-ethoxy-modified phosphorothioate oligonucleotides were designed. These oligonucleotides differed in the number of mismatches to bcl-2 and bcl-xL and in the number of nucleotides to which the modifications were made. The effects of these oligonucleotides on bcl-2 and bcl-xL expression, as well as their abilities to induce apoptosis, were assessed in small cell and non-small cell lung cancer cell lines expressing different basal levels of bcl-2 and bcl-xL. Although all oligonucleotides down-regulated bcl-2 and bcl-xL expression, oligonucleotide 4625, which has no mismatching nucleotides to bcl-2 but three to bcl-xL, two of which were modified by 2'-O-methoxy-ethoxy residues, showed the strongest bispecific activity on the transcript and protein level. In all cell lines this bispecific activity induced apoptotic cell death, as demonstrated by increased uptake of propidium iodide, a 10-100-fold increase in caspase-3-like protease activity, and nuclear condensation and fragmentation. This is the first report of a bcl-2/bcl-xL bispecific antisense oligonucleotide that deserves attention as a therapeutic compound in lung cancer and other malignancies in which bcl-2 and/or bcl-xL are overexpressed.

Induction of apoptosis in lung-cancer cells following bcl-xL anti-sense treatment

Over-expression of the anti-apoptotic protein bcl-xL is frequently found in lung cancer where it potentially contributes to tumor development, progression and drug resistance. To override the apoptotic block in lung-adenocarcinoma and small-cell-lung-cancer (SCLC) cells caused by over-expression of bcl-xL, an anti-sense oligodeoxynucleotide was designed targeting a sequence unique to the bcl-xL coding region and not shared by the pro-apoptotic splice variant bcl-xS. Moreover, to improve the biophysical properties of the anti-sense compound, 2;-methoxy-ethoxy modifications were made to selected deoxy-ribose residues. The resulting gapmer oligonucleotide 4259 was tested on lung-adenocarcinoma and SCLC cell lines in vitro. Treatment of the adenocarcinoma cell lines A549 and NCI-H125 and the SCLC cell lines SW2 and NCI-H69 with 600 nM 4259 reduced bcl-xL levels by 70 to 90%. In the lung-adenocarcinoma cell lines, apoptosis was induced, as indicated by caspase-3-like protease activation and nuclear condensation and fragmentation. In contrast, in the SCLC cell lines, no induction of apoptosis could be demonstrated. These findings imply that bcl-xL is a more critical survival factor for lung adenocarcinomas than for SCLC, and suggest the use of oligonucleotide 4259 for therapy of this major sub-type of lung cancer.