4th LTBW Absiracts / Lung Cancer 10 (1994) 347-373

hibit the process, which is therefore presumably a proteolytic degradation.

We are continuing our studies to determine the sites of pro- teolytic cleavage of Y-23-R-NH,, and to elucidate whether inhibiting the cleavage may stimulate the mitogenic effects shown for this peptide.

Binding of cellular proteins to the conformational domain of ~53 Maxwell SA, Roth JA. Department of Thoracic Surgery, Uni- versity of Texas M.D. Anderson Cancer Center, 1515 Holcombe. Houston, Texas, 77030.

The genes regulated by ~53, as well as the factors modulating its function, need to be identified to understand definitively the mechanism of its action in control of cell growth. Since binding of the SV40 large T-antigen protein to a domain of p53 contain- ing evolutionally conserved sites (conformational domain) alters its tertiary structure and inactivates its DNA-binding capability, we postulated that cellular proteins normally bind to this same region of ~53 to regulate its function. Chimeric proteins comprised of wild-type ~53 sequences from amino acids I IS and 295, and ~53 sequences mutated at amino acids 273 or 175, fused protein A were used to probe for binding pro- teins in detergent lysates of non-small cell lung carcinoma (NSCLC) cells. The wild-type ~53 chimeric protein associated with several major proteins of 45 k, 56 k, and 70 k Mr’s, as well as other minor species ranging in size from 30-90 k Mr. These proteins bound specifically to ~53, since protein A alone was negative for binding and the mutant ~53 proteins exhibited relative 40-25% decreases in binding. Conditions of cell growth had a profound effect on the expression of p53-binding pro- teins, with highest yields being recovered from cultures in an active growth state. Quantitative differences in expression of p53-binding proteins were also observed among different NSCLC cell lines. The influence of these p53-binding proteins on conformation and DNA-binding activity of purified wild- type ~53 is currently being investigated.

Bombesiilike peptides, neuroendacrine cells and pulmonary carcinogenesis Miller YE, Aguayo SM. Denver and Atlanra VAMC.

Pulmonary neuroendocrine cells are the first cells to differen- tiate from the primitive respiratory epithelium during lung de- velopment. Pulmonary neuroendocrine cells contain a variety of neuropeptides, at least two of which, gastrin releasing pep- tide and calcitonin gene related peptide, have been demonstrated to be growth factors for bronchial epithelial cells. Further evidence for a role of the pulmonary endocrine cell in regulating the growth of respiratory epithelium is that an in- verse correlation exists between distance from clusters of neuroendocrine cells and epithelial cell thymidine incorpora- tion in developing hamster lung. Furthermore, administration of bombesin to pregnant mice results in increased growth and maturation of fetal lungs.

A number of animal models of lung injury and car- cinogenesis display pulmonary neuroendocrine cell hyper- plasia. Schuller has presented evidence that regenerating airway epithelium can display a neuroendocrine phenotype. In adult

humans, neuroendocrine hyperplasia has been described as oc- curring frequently in association with lung cancer as well as with a variety of nonmalignant disorders. Pulmonary neuroen- docrine cell hyperplasia has also been demonstrated in a num- ber of airway diseases associated with tobacco smoke, including chronic bronchitis, eosinophilic granuloma, and res- piratory bronchiolitis. Many of these disorders are associated with an increased risk of lung cancer over smoking alone.

We have studied asymptomatic cigarette smokers with nor- mal pulmonary function tests and demonstrated that a subset of this group expresses increased levels of a bombesin-like peptide in their lower respiratory tract. Urinary bombesin-like peptide levels are likewise elevated in a subset of clinically nor- mal smokers and are elevated in all smokers studied to date who express increased levels of lower respiratory tract bombesin-like peptides. Bronchoscopy with bronchoalveolar lavage is too invasive and expensive to be useful as a population screening tool. Furthermore, there are serious technical pro- blems with interpreting the levels of mediators in broncho- alveolar lavage of individuals with different forms of lung disease. Therefore, urinary levels of bombesin-like peptides and other neuropeptide mediators may be clinically more useful.

We are now attempting to test the hypothesis that elevated bombesin-like peptide levels are a marker for lung injury which identities a subset of smokers at increased risk for the develop- ment of lung cancer. We have begun two studies. The first is a cross sectional survey of urinary bombesin-like peptide levels in normal non-smokers and smokers, smokers with mild chronic obstructive pulmonary disease, and patients with lung cancer of all histologic types. Analysis of this study is not yet complete, but preliminary data show an increased level of urinary bombesin-like peptide in smokers with lung cancer. Factors such as tumor production of neuropeptide, hypoxemia or the co-existence of pneumonia likely confound these data. We are also beginning a population survey in which 4000 smokers with chronic obstructive pulmonary disease will undergo sputum cytology testing as well as urinary bombesin-like peptide levels. We hope to determine whether elevated urinary bombesin-like peptides correlate with various cytologic abnormalities in sputum as well as with the eventual development of lung cancer in these individuals. If the hypothesis that smokers with in- creased levels of urinary bombesin-like peptides are at increas- ed risk for the development of lung cancer is supported, then this group could be selected for chemoprevention studies and urinary bombesin-like peptide levels could be evaluated as an intermediate end-point marker.

Peptide receptor antagonists ami lung cancer Moody TW. Department of Biochemistry & Molecular Biology, The George Washington University School of Medicine and Health Sciences. Washington, DC 20037.

SCLC is a neuroendocrine tumor which uses gastrin releas- ing peptide (GRP) and neuromedin B (NMB) as autocrine growth factors. High levels of GRP immunoreactivity and mRNA are present in some classic but not variant SCLC cell lines. In contrast, low levels of NMB immunoreactivity and mRNA are present in SCLC and NSCLC cell lines. GRP is