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Under retinoic acid exposure, the three SK-N-BE(2)-derived human neuroblastoma cell lines, BE(2)-NA, BE(2)-SA and BE(2)-M17 undergo mainly differentiation, apoptosis or continue to proliferate, respectively. We have used this model system to study the modulation of the transcriptional expression of putative processing enzymes, two novel metallopeptidases; i.e. N-arginine dibasic convertase (NRD convertase; EC 3.4,24,61) and an aminopeptidase-B after exposure of the cells either to retinoic acid or to synthetic retinoid analogs. The data indicate that the two respective enzymes are differently modulated in the various cell lines. Whereas aminopeptidase-B expression is enhanced in most cases, NRD convertase appears to undergo opposite regulation in proliferating versus differentiating neuroblastoma cells. It is concluded that both genes might contain retinoic acid regulatory elements (RARE) in their promoters.

The most prevalent lung cancer, non-small cell lung cancer (NSCLC) has receptors for vasoactive intestinal peptide (VIP). Here the effects of a VIP antagonist (VIP-hyb) on NSCLC growth were investigated. In vivo, when VIPhyb (10 micrograms, s.c.) was daily injected into nude mice, xenograft formation was significantly inhibited by approximately 80%. In vitro, VIP (100 nM) stimulated colony formation approximately 2-fold, whereas 1 microM VIPhyb inhibited colony formation by approximately 50% when adenocarcinoma cell line NCI-H838 was used. The attenuation of tumor proliferation is receptor mediated, as VIPhyb inhibited specific 125I-labeled VIP binding to cell lines NCI-H157 and NCI-H838 with an IC50 of 0.7 microM. VIP (10 nM) increased the cAMP levels 5-fold when cell line NCI-H838 was used, and 10 microM VIPhyb inhibited the increase in cAMP caused by VIP. Northern blot analysis and radioimmunoassays have shown VIP mRNA and VIP-like immunoreactivity in NSCLC cells. These data suggest that VIP may be a regulatory peptide in NSCLC and that VIPhyb is a VIP receptor antagonist that inhibits proliferation.

The effects of PACAP on c-fos mRNA using small cell lung cancer (SCLC) cell was investigated. PACAP-27 (100 nM) increased c-fos mRNA 5-fold using NCI-N417 cells. The increase was concentration dependent with 0.1 nM PACAP-27 half maximally increasing c-fos mRNA. Also the increase in c-fos mRNA caused by PACAP was time dependent; being maximal after 1 hour and returning to basal values after 4 hours. PACAP-38 but not PACAP(28-38) increased c-fos mRNA. One uM PACAP(6-38), a PACAP receptor antagonist, inhibited the increase in c-fos mRNA caused by 1 nM PACAP. These data indicate that PACAP stimulates nuclear oncogene expression in SCLC cells.

The ability of a chimeric toxin containing transforming growth factor alpha (TGF alpha) and truncated Pseudomonas exotoxin A to inhibit NSCLC growth was investigated. TGF alpha-PE40 inhibited binding of 125I-EGF to NSCLC cell lines with an IC50 value of 0.5-3 micrograms/ml. Similarly, other forms of the fusion protein, TGF alpha-PE38 and TGF alpha-PE40Asp553, which have active TGF alpha binding domains, inhibited specific 125I-EGF binding to NSCLC cells with IC50 values of 0.1-2 and 0.05-05 microgram/ml respectively. TGF alpha-PE40 inhibited 35S-methionine uptake by NSCLC cells with an ED50 value of 1-30 ng/ml. TGF alpha-PE38, which has one of the two disulfide pairs of PE40, inhibited amino acid uptake with ED50 values of 3-50 ng/ml whereas TGF alpha-PE40Asp553, which lacks ADP ribosylation activity, had an ED50100 ng/ml. TGF alpha-PE40 inhibited colony formation of NSCLC cells with an LD50 value of 0.008-0.1 ng/ml. Similarly, TGF alpha-PE38 inhibited NSCLC colony formation with LD50 values of 0.002-0.1 ng/ml whereas TGF alpha-PE40Asp553 had an LD5010 ng/ml. Also, TGF alpha-PE40 and TGF alpha-PE38 inhibited NSCLC xenograft formation in nude mice whereas TGF alpha-PE40Asp553 was inactive. These data suggest that TGF alpha-PE40 and TGF alpha-PE38 may be useful agents to inactivate NSCLC cells.

Bombesin/gastrin releasing peptide (BN/GRP) is an autocrine growth factor for some small cell lung cancer (SCLC) cells1. The GRP gene, which contains 2 introns and is localized to human chromosome 18q, is expressed in some SCLC cell lines such as NCI-H345 and H2092-4. GRP, which is present at high concentrations in classic SCLC cells, is released when the cAMP is elevated5,6. GRP binds with high affinity to NCI-H345 cells and stimulates phosphatidylinositol turnover7,8 The inositol-1,4,5-trisphosphate released elevates cytosolic calcium and the diacylglycerol released activated protein kinase C9,10 Also, GRP or BN stimulate SCLC colony formation and xenograft formation in nude mice11,12. SCLC growth in vitro and in vivo is blocked by synthetic BN/GRP receptor antagonists13,14