Reasons for quitting smoking among low-income African American smokers

The psychometric characteristics of the Reasons For Quitting scale (RFQ) were assessed among a sample of African American smokers with low income (N=487). The intrinsic and extrinsic scales and their respective subscales were replicated. As hypothesized, higher levels of motivation were associated significantly, in patterns that supported the measure's construct validity, with advanced stage of readiness to quit smoking, greater perceived vulnerability to health effects of smoking, and greater social support for cessation. On the basis of the present study, the RFQ might best predict short-term cessation among older and female smokers. Refinement of the RFQ is needed to assess intrinsic motivators other than health concerns and to identify salient motivators for young and male smokers.

Integration of peripheral blood biomarkers with computed tomography to differentiate benign from malignant pulmonary opacities

Our purpose was to determine whether peripheral blood biomarkers MUC1 and CK19 could be used to complement imaging studies in differentiating benign from malignant indeterminate pulmonary nodules or masses detected on computed tomography CT. One hundred and eighteen patients had a thoracic CT and blood drawn for tumor marker reverse transcriptase-polymerase chain reaction analysis. Thirty-five of the 118 patients had an indeterminate pulmonary nodular opacity on CT, and the findings then were correlated with the reverse transcriptase-polymerase chain reaction results. The sensitivity and specificity for the markers in determining malignancy was calculated. Thirteen of the 35 opacities on CT proved to be benign, and 22 proved to be lung cancer. Among the patients with indeterminate pulmonary abnormalities, polymorphic epithelial mucin protein 1 had a sensitivity and specificity for lung cancer of 100% and 46%, respectively. Cytokeratin 19 had a sensitivity and specificity for lung cancer of 95% and 8%, respectively. These preliminary data showed that serum biomarkers polymorphic epithelial mucin protein 1 and cytokeratin 19 were not specific for lung cancer, although patients with an indeterminate pulmonary abnormality and negative markers were unlikely to have lung cancer. Integration of imaging studies with the appropriate biomarkers may prove useful in evaluating indeterminate pulmonary nodules or masses.

Transcript map and complete genomic sequence for the 310 kb region of minimal allele loss on chromosome segment 11p15.5 in non-small-cell lung cancer

Molecular, functional, and clinical analyses strongly suggest that chromosome segment 11p15.5 contains a gene involved in lung cancer pathogenesis. The critical region of allele loss is 310 kb in size. We used our contig of P1-phage artificial chromosome (PAC) clones together with newly identified bacterial artificial chromosome (BAC) clones and the draft human genome sequence to complete a contiguous string of 380 407 bp. Three PAC clones that span the region were used to identify transcripts by exon trapping. Computational gene prediction algorithms were used to query the sequence for potential genes and exons. Screening for expression was performed with tissue-specific and cell line derived mRNA arrays. The region contains the complete SSA/Ro52 and RRM1 genes, exons 7-12 of the GOK gene, and the psirad pseudo-gene. A cluster of six nearly identical genes with an intact open reading frame (ORF) of 585 bp that share 75% identity with the HSPC182 gene was found. In addition, five putative novel genes were identified. Sequence tagged sites (STS) and polymorphic markers were used to screen 117 lung cancer cell lines for homozygous deletions and none were identified. These data provide the basis for the identification of a lung cancer suppressor gene on 11p15.5.

Comparison of cytochrome P450 2A6 polymorphism frequencies in Caucasians and African-Americans using a new one-step PCR-RFLP genotyping method

CYP2A6 (cytochrome P450 2A6), which was first identified as the human coumarin 7-hydroxylase, is the most important enzyme in nicotine C-oxidation. The enzyme also metabolically activates the tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in vitro. Polymorphisms in the CYP2A6 gene may thus impact on both smoking behavior and lung cancer susceptibility. Several different genotyping methods have been reported with conflicting results in the frequencies of CYP2A6 polymorphic variants. Thus we decided to perform a sequence analysis of the entire CYP2A6 gene. Sequencing confirmed the published CYP2A6 cDNA sequence. However, intron sequences differed considerably from the reported sequence of the CYP2A6*3 (v2) variant. Our analyses revealed that parts of introns shared homologies with the published sequence of CYP2A13. Based on our sequence data we developed a one step protocol for specific amplification of exon 3 of CYP2A6. The resulting PCR product can be used directly for restriction endonuclease digestion with XcmI and DdeI to determine the frequencies of the reported variant alleles CYP2A6*2 and CYP2A6*3. In a population of 305 African-Americans and 145 Caucasians, we found allele frequencies of 0.003 (2/610) for CYP2A6*2 and 0 (0/610) for CYP2A6*3 in African-Americans and allele frequencies of 0.014 (4/290) and 0 (0/290) in Caucasians. We conclude that both alleles are considerably less frequent in populations than previously reported.

MCM2 is an independent predictor of survival in patients with non-small-cell lung cancer

PURPOSE

Minichromosome maintenance protein 2 (MCM2) is a component of the prereplicative complex. It is essential for eukaryotic DNA replication and is only expressed in proliferating cells. The prognostic utility of MCM2 compared with Ki-67, another marker of proliferating cells, on survival of patients with non-small-cell lung cancer (NSCLC) was studied.

PATIENTS AND METHODS

We examined the immunohistochemical expression of MCM2 and Ki-67 in primary pathologic tumor specimens from 221 NSCLC patients. For each marker, the fraction of tumor cells with positive staining was assessed as a percentage and categorized into four groups: 0% to 24%, 25% to 49%, 50% to 74%, and > or = 75%. MCM2 and Ki-67 immunoreactivities were compared with each other, and associations with pathologic and clinical parameters predictive of survival were analyzed with the chi(2) test. Cox regression models were used to assess associations between MCM2 and Ki-67 and survival while controlling for confounders.

RESULTS

Independent variables significantly associated with survival were tumor stage, performance status, and staining category. Patients with less than 25% MCM2 immunoreactivity had a longer median survival time than patients with > or = 25% MCM2 immunoreactivity (46 v 31 months; P =.039) and a lower relative risk (RR) of death (RR, 0.55, 95% confidence interval, 0.34 to 0.88). There was no significant association between survival and Ki-67 expression.

CONCLUSION

Immunostaining of tumor cells for MCM2 is an independent prognostic parameter of survival for patients with NSCLC. Interpretable results can be obtained on more than 96% of paraffin-embedded specimens, and approximately 35% will be in the favorable subgroup, with less than 25% positively stained tumor cells. Whether MCM2 is predictive of response to therapy needs to be studied.

Reasons for quitting smoking among low-income African American smokers

The psychometric characteristics of the Reasons For Quitting scale (RFQ) were assessed among a sample of African American smokers with low income (N=487). The intrinsic and extrinsic scales and their respective subscales were replicated. As hypothesized, higher levels of motivation were associated significantly, in patterns that supported the measure's construct validity, with advanced stage of readiness to quit smoking, greater perceived vulnerability to health effects of smoking, and greater social support for cessation. On the basis of the present study, the RFQ might best predict short-term cessation among older and female smokers. Refinement of the RFQ is needed to assess intrinsic motivators other than health concerns and to identify salient motivators for young and male smokers.

Rater agreement and utility of the mutagen-induced chromosome damage assay

Chromosomal damage in peripheral blood lymphocytes induced by short-term in vitro exposure to the cytotoxic antibiotic bleomycin was first described in 1983 and proposed as a phenotypic assay for chromosome instability. This assay was subsequently described as potentially useful in assessing an individual's risk to environmental carcinogens in 1989. Since 1995 numerous published studies have used this assay to assess risk for cancer in the aerodigestive tract, particularly lung cancer, in various ethnic populations. Odds ratios up to 8.5 have been reported for individuals deemed "mutagen sensitive" (defined as > or = 1 chromatid break per metaphase averaged in 50 metaphases analyzed). While this phenotypic assay is appealing for lung cancer risk assessment it has not been reproduced by other investigators. Because of our interest in lung cancer biology, epidemiology, and genetics, we sought to independently assess the rater agreement of this assay. We found that 1) the assay is laborious to conduct (8 hours of labor) and relatively expensive (> $100), yet reducing the number of metaphases from 50 to 20 produced a reliable, less expensive, and less laborious test; and 2) the rater agreement of individual metaphase readings is poor, but agreement for a summary measure is high.

SSA/RO52gene and expressed sequence tags in an 85 kb region of chromosome segment 11p15.5

Frequent allelic loss in lung cancer has been described in a region on chromosome segment 11p15.5 (LOH11A). The region is approximately 650 kb in size and flanked by the markers D11S988 centromeric and D11S860 telomeric. Clinical and cell biological studies suggest that it contains a gene associated with metastatic tumor spread. One of the genes identified within this region is SSA/Ro52, which has a RING finger domain and may be involved in gene regulation. We studied this gene for mutations using SSCP analysis and for expression using RT-PCR and Western blotting on lung cancer cell lines and tumor-normal tissue pairs. No mutations and no differences in mRNA or protein expression between tumor tissue and normal tissue pairs were identified. We discovered a novel polymorphic site (SSA44C/T) within exon 1 of this gene. Among 141 primary lung cancers, allelic loss was observed in 16% of informative cases. Our analyses excluded SSA/Ro52 as a tumor-suppressor gene in lung cancer and newly defined the centromeric border of the LOH11A region from D11S988 previously to SSA44C/T. This reduced the region of the putative suppressor gene to 460 to 485 kb. A significant difference (p = 0.01) in the frequency of alleles for this polymorphism between Caucasians and African-Americans was observed. The "T" allele frequency was 0.12 in Caucasians and 0.23 in African-Americans. A genomic EcoRI map over 85 kb surrounding the SSA/Ro52 gene was constructed, and 4 expressed sequence tags were identified by sequencing and studied.

Maximizing the motivational impact of feedback of lung cancer susceptibility on smokers' desire to quit

This two-by-two factorially designed study evaluate approaches for communicating feedback of lung cancer susceptibility to smokers as a method for motivating smoking cessation. The study factors were: method of communicating feedback (by mail with telephone follow-up or in-person) and carbon monoxide feedback (yes or no). One-hundred-forty-four smokers were stratified on race and randomized to one of four conditions. Participants were surveyed at baseline and 2-month follow-up. Polymerase chain reaction (PCR) testing for the absence of the glutathione S transferase mu (GSTM1) gene was the susceptibility marker. Regardless of counseling method or carbon monoxide (CO) feedback, the majority (90%) of smokers accurately recalled the test result and 66% accurately interpreted the meaning of the test result. Smokers who received their result in person were significantly less likely to have read the result booklet than those in the telephone counseling group (OR = .28, 95%; CI .12-.62; p < .05). Neither counseling method nor CO feedback increased smokers' perceived risks for lung cancer. However, at the counseling session those who received in-person counseling were significantly less frightened by the test result than those who received telephone counseling (OR = .42, 95%; CI .20-86; p < .05) and at the 2-month follow-up those who received a CO test were significantly less frightened by their susceptibility result (OR = .40, 95%; CI .17-.92; p < .05) than those who did not have a CO test. Evaluation of further refinements in communicating the meaning of susceptibility results to motivate smoking cessation is warranted.

The effect of orchiectomy on lung cancer survival

Gender is an independent prognostic factor for survival from lung cancer with the relative risk of lung cancer death for men compared to women being 1.3. This observation remains unexplained but in vitro data suggests a stimulatory effect of androgens on lung cancer growth. We hypothesized that androgen deprivation improves survival in men with lung cancer compared to hormonally intact men with lung cancer. On the basis of age, race and region, we matched 44 men with lung cancer and bilateral orchiectomy with 88 men who had lung cancer and no history of orchiectomy and compared their survival. Since hazards were non-proportional we chose the generalized gamma model to describe the survival function. The survival was significantly different between the two groups (p = 0.0048) with the orchiectomy group having a better two year overall survival. This retrospective study suggests that androgen depletion may significantly improve the short term survival of men with lung cancer but further, prospective investigation is required for confirmation.

Lung cancer epidemiology and genetics

Lung cancer is the number one cause of cancer death for all citizens of the United States regardless of gender, race, or ethnic background. Surgery, the only curative treatment available, is feasible in only 35% of all patients with lung cancer. But even in this group of patients, most will die of recurrent disease. Treatment advances have been modest at best, and the 5-year survival rate of approximately 15% has not changed appreciably in the past two decades. Population projections indicate a continuation of the lung cancer epidemic among men and a rise among women, in whom rates of smoking have remained relatively high. It is estimated that 90% of all lung cancers are smoking related, and gender, race, and family history are important risk modifiers. Several promising markers of lung cancer susceptibility have recently been identified. However, the relative contribution of individual intrinsic factors (genetic markers, family history, race, gender) on lung cancer susceptibility in the context of complex extrinsic factors (behavior, environmental exposure, socioeconomic status) is unknown and requires further study for more informed screening and primary prevention.

Lung cancer and the human gene for ribonucleotide reductase subunit M1 (RRM1)

LOH11A is a region of Chromosome (Chr) 11p15.5 where 75% of lung cancers show loss of heterozygosity (LOH). Clinical and cell biological studies suggest that LOH11A contains a tumor/metastasis suppressor gene. We have mapped this region (650 kb) using overlapping genomic P1/PAC/BAC clones, and one of the genes that we have identified is RRM1. This gene encodes the large subunit (M1) of ribonucleotide reductase, the heterodimeric enzyme that catalyzes the rate-limiting step in deoxyribonucleotide synthesis. By comparing our genomic sequences with the previously published cDNA, we have found that the human gene is composed of 19 exons. It is oriented telomere to centromere and is Alu rich. In order to verify that RRM1 maps within the boundaries of LOH11A, we assessed the frequency of LOH at a SacI polymorphism within intron IX of the gene. We observed LOH in 48% (15/31) of informative lung tumor specimens. To determine whether RRM1 was mutated in tumors, SSCP analysis of the 19 RRM1 exons was performed. No mutations were revealed in 12 pairs of normal and tumor DNA samples. Immunoblots on protein extracts from normal/tumor pairs indicated that a protein of the expected size was present in both. Our conclusion is that RRM1 lies within the LOH11A region, but that its exons are not mutated in tumors. The potential for RRM1 to act as a tumor suppressor is discussed.

Molecular genetic analysis of primary lung cancer and cancer metastatic to the lung

The lung is a very common site for primary cancer and metastatic disease. Advances in tumor biology have provided insight into the sequence of genetic alterations leading to tumor and metastasis formation in the lung. In this review we address two genetic alterations, the dominant ras oncogene and the p53 tumor suppressor gene, which are commonly found in lung cancer and pulmonary metastases. We discuss their specific roles in tumor development, invasion, metastasis formation, and their potential prognostic utility. In addition, we will discuss the concept of a novel modulator gene, ribonucleotide reductase, and review its role in the control of metastasis formation.

A 1.4-Mb high-resolution physical map and contig of chromosome segment 11p15.5 and genes in the LOH11A metastasis suppressor region

The centromeric part of chromosome segment 11p15.5 contains a region of frequent allele loss in many adult solid malignancies. This region, called LOH11A, is lost in 75% of lung cancers and is thought to contain a gene that may function as a metastasis suppressor. Genetic complementation studies have shown suppression of the malignant phenotype including reduction of metastasis formation. We constructed a high-resolution physical map and contig over 1.4 Mb that includes the beta-hemoglobin gene cluster and the gene for the large subunit of ribonucleotide reductase (RRM1). Through sequencing and computerized analysis, we determined that this region contains an unusually large number of transposable elements, which suggests that double-stranded DNA breaks occur frequently here. Twenty-two putative genes were identified. Because of its location at the site of maximal allele loss in the 650-kb LOH11A region and previous functional studies, RRM1 is the most likely candidate gene with metastasis suppressor function. The malignant phenotype, in this case, results from a relative loss of function rather than a complete loss.

Hot spots for molecular genetic alterations in lung cancer

Lung cancers are a heterogeneous group of tumors broadly classified as small cell or non-small cell lung cancers. In each case, numerous DNA mutations precede tumor formation, resulting in the activation of growth stimulatory genes and the loss of tumor suppressor genes. The known cellular functions of the tumor suppressor genes most commonly affected in lung cancer are reviewed herein, including the retinoblastoma (Rb) gene on chromosome 13q14, the p53 gene on 17p13, and the cyclin-dependent kinase inhibitor (CDKN2) gene on 9p21. The chromosomal locations for other potential tumor suppressor genes are on chromosomes 3p, 9p, and 11p. Candidate genes in these regions include the von Hippel-Lindau (VHL) gene at 3p25, the ubiquitin-activating enzyme homologue (UBE1L at 3p21, the genes for the dinucleoside polyphosphate hydrolase FHIT and receptor protein-tyrosine phosphatase gamma PTPRG at 3p14.2, the genes for tropomyosin beta (TM1) and a talin homologue (talin) at 9p21, and the H-ras gene at 11p15.

In vitro chemosensitivity testing of human non-small cell lung cancer cell lines

Three human non-small cell lung cancer (non-SCLC) cell lines, one each derived from squamous cell carcinoma, adenocarcinoma, and large cell carcinoma were tested for chemosensitivity to 23 cytostatic agents using the soft agarose clonogenic assay. Results were compared with in vitro responses of SCLC cell lines derived from patients with and without prior chemotherapy and with in vivo phase II clinical trials in non-SCLC. Carboplatin, daunorubicin, paclitaxel, and teniposide were active in two non-SCLC cell lines and actinomycin D, bleomycin, etoposide, irinotecan, and mithramycin were active in one cell line. The cell line from the treated SCLC patient was less sensitive to cytostatic agents than the cell line from the untreated SCLC patient and had a sensitivity pattern comparable to non-SCLC cell lines. These data are consistent with clinical experience in non-SCLC and suggest that non-SCLC cell lines in conjunction with the soft agarose clonogenic assay can be useful for in vitro drug screening. They confirm that carboplatin and paclitaxel are among the most active drugs in non-SCLC and suggest that daunorubicin and teniposide may be more active then their more frequently used analogues.

Molecular characterization of the human delta opioid receptor in lung cancer

A variety of neuropeptide receptors have been detected in human lung cancer. They are thought to play a role in autocrine/paracrine regulation of cell growth, and may be clinically useful as diagnostic, prognostic or therapeutic targets. The current study characterizes the molecular structure of the delta opioid receptor and its gene expression level in lung cancer cell lines relative to normal human lung using a sensitive RT-PCR approach. The goals of this investigation were a) to define the correlation between receptor binding and gene expression in lung cancer cell lines, and b) to determine the cDNA sequence integrity of this receptor in comparison to the receptor recently found in human brain. Five small cell lung cancer (SCLC) cell lines revealed size-matched RT-PCR products which strongly hybridized to the human brain delta opioid receptor probe. One of three non-small cell lung cancer (NSCLC) cell lines (NCI-H23), known to be negative by binding analysis, demonstrated low level expression. No gene expression was found in normal human lung. RT-PCR products from two SCLC cell lines (SCLC-22H and 16HC) as well as the low level expressing NSCLC cell line (NCI-23) were subjected to bidirectional DNA sequence analysis and the receptor ends were resolved using a 3'-end RACE and 5'-end gene-specific approach. The isolated cDNA sequences proved to be identical to the published human brain delta opioid receptor sequence. These data show that lung cancers with neuroendocrine features express human brain delta opioid receptors in contrast to normal lung, and that the delta opioid receptor mRNA in lung cancer is not mutated. This unique feature of lung cancer may be exploitable for diagnostic, prognostic, and therapeutic strategies.

Association of chromosome 11 locus D11S12 with histology, stage, and metastases in lung cancer

We have reported frequent allele loss for the marker D11S12 on chromosome band 11p15.5 in human lung cancer. The smallest common region of allele loss has been refined to approximately 500 kb and is confined between D11S1758 and D11S860. Here, we investigated the association of D11S12 allele loss with epidemiologic, pathologic, and clinical parameters. Analysis of allele loss was performed by Southern blotting on a cohort of 156 patients with lung cancer, and data were interpreted with the use of a phosphorimager. Results were statistically compared with retrospectively collected variables. D11S12 allele loss was found in 88% of small cell carcinomas, 57% of squamous cell carcinomas, and 40% of adenocarcinomas. Allele loss was associated with tumor stage (p = 0.04) and was more frequent in tumors that had already metastasized. These results suggest that a gene in the D11S12 region may be responsible for the metastatic potential of lung cancer. The functional status of this gene may thus be of future value in guiding clinicians on decisions regarding adjuvant and neoadjuvant therapies for patients with lung cancer.

Growth inhibition of a human lung adenocarcinoma cell line by genetic complementation with chromosome 11

Two regions on chromosome segment 11p15.5 have frequent allele loss in lung cancer. LOH11A is centromeric between loci D11S1758 and D11S12, and LOH11B is telomeric between HRAS and D11S1363. We studied the biological significance of this allele loss using microcell-mediated transfer of human chromosomes 11, 11p, and two radiation-reduced fragments of 11p into human lung adenocarcinoma cell lines. Chromosome 12, which has not been implicated in lung carcinogenesis, was used as a control. All four chromosome 11-containing hybrid clones showed significantly reduced tumorigenicity in nude mice and growth in liquid culture. These findings support the notion of a tumor suppressor gene located in the LOH11A region on chromosome segment 11p15.5.

Smoking, gender, and survival association with allele loss for the LOH11B lung cancer region on chromosome 11

We have reported frequent allele loss for the marker HRAS on chromosome 11p in human lung cancer and defined the smallest common region of deletion (designated LOH11B) to approximately 500 kb. Here, we investigated the association of allele loss for LOH11B with epidemiological, pathological, and clinical parameters. Analysis of allele loss was performed using Southern blotting on a cohort of 200 patients with lung cancer, and data were interpreted with the use of a phosphorimager. Results were statistically compared with retrospectively collected variables. LOH11B allele loss was significantly associated with cigarette consumption (P = 0.009), gender (P = 0.02), and survival (P = 0.04). None of the nonsmokers had allele loss as compared with 28% of the patients with low and 43% with high cigarette consumption. Allele loss was more frequent in men (43%) than in women (11%). The median survival of patients without allele loss was 42 months compared with 25 months for patients with allele loss. These results suggest that the LOH11B region contains a gene responsible for a more malignant phenotype independent of the metastatic potential of lung cancer. They also suggest that alterations in this gene are associated with cigarette consumption and are more frequent in men than in women.

Delineation of the centromeric and telomeric chromosome segment 11p15.5 lung cancer suppressor regions LOH11A and LOH11B

We have reported frequent allele loss for two separate regions identified by the markers D11S12 and HRAS on chromosome 11p15.5. D11S12 allele loss was associated with tumor stage and type and HRAS allele loss with cigarette consumption, sex, and survival. To positionally clone the putative tumor suppressor genes located in these regions, we here report a reduction in the size of these intervals to approximately 250 kb. The markers used, ordered from centromere to telomere, were D11S932 -D11S1331-D11S1760-D11S1323-D11S4891 (HBB)-D11S1758-D11S12-D11S988-D11S860-D11S131 8-TH-HRAS-D11S1363-D11S2071. We analyzed 44 tissue pairs from patients with primary lung cancer. The smallest common regions of allele loss were located between D11S1758 and D11S12 in the centromeric region of chromosome segment 11p15.5 (region of LOH on chromosome 11 in lung cancer, LOH11A) and between HRAS and D11S1363 in the telomeric region (region of LOH on chromosome 11 in lung cancer, LOH11B). Loss of heterozygosity was observed in 24/39 (62%) primary lung cancers informative for LOH11A and in 17/34 (50%) informative for LOH11B. The pattern of allele loss strongly suggests that two lung cancer suppressor genes are located on chromosome segment 11p15.5, one between D11S1758 and D11S12 and the other between HRAS and D11S1363. The estimated physical size of each of these regions is 250 kb.

Characterization of delta opioid receptors in lung cancer using a novel nonpeptidic ligand

Cancer cells are often characterized by the presence of membrane receptors not normally associated with nontransformed cells from the same tissue type. Recent studies have demonstrated increased expression of high-affinity binding sites for opioid receptor-selective ligands in lung cancer cell lines relative to normal lung tissue. We investigated the binding of a nonpeptidic delta opioid receptor ligand in small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cells with the aim of developing the ligand as a novel lung cancer imaging agent. The ligand, [3H] (+)-4-[alpha-R)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3- hydroxybenzyl)-N,N-diethylbenzamide ([3H](+)BW373U86), bound with high-affinity [Kd (dissociation constant) = 0.066 +/- 0.012 nM] to membranes prepared from six different SCLC cell lines but not to those from seven NSCLC cell lines, including one mesothelioma. The number of biding sites varied from 10 to 300 fmol/mg membrane protein. Competition binding studies demonstrated displacement of [3H](+)BW373U86 binding by the delta-selective antagonists naltriben and 7-benzylidenenaltrexone but not with the mu- and kappa- selective antagonists D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 and trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]ben zeneacetamide methanesulfonate. Mean apparent Kis for naltriben and 7-benzylidenenaltrexone in membranes from two SCLC cell lines were 0.17 and 3.9 nM, respectively, but were >10 microM for the mu and kappa ligands. The nonselective antagonist naloxone displaced [3H](+)BW373U86 binding with an apparent Ki of approximately 29 nM. On the basis of these data, we believe the lung cancer receptor to be similar, if not identical, to the human brain delta opioid receptor. The lack of high-affinity [3H](+)BW373U86 binding in normal mouse lung membranes suggests a potential role for this ligand as a novel therapeutic or imaging agent.