gramicidin-a and Carcinoma--Small-Cell

Bombesin is a 14 amino acid peptide originally isolated from amphibian skin; its mammalian homolog is gastrin-releasing peptide (GRP). GRP is found in a high proportion of human small cell lung cancer (SCLC) cell lines. [Tyr4]bombesin caused an increase in intracellular Ca2+ ([Ca2+]i) in 5/11 SCLC cell lines tested. Bombesin action was not inhibited by agents known to alter the plasma membrane potential, nor did replacement of external Na+ with choline affect the bombesin-induced signal. [Tyr4]bombesin did not itself affect the membrane potential. Chelation of external Ca2+ reduced but did not prevent the bombesin-evoked increase in [Ca2+]i. This suggested that in SCLC, bombesin congeners not only promote an influx of extracellular Ca2+ but also release Ca2+ from intracellular stores. [Tyr4]bombesin increased levels of inositol 1,4,5-trisphosphate within seconds of addition to SCLC cell cultures and enhanced the accumulation of inositol 1-phosphate and inositol 4-phosphate in the presence of Li+. The SCLC cell lines responsive to bombesin constitutively expressed L-myc and did not express c-myc or N-myc. In contrast, SCLC cells non-responsive to bombesin had prominent constitutive expression of c-myc or N-myc with or without L-myc expression. Responding cell lines also had constitutive expression of the preproGRP gene, while non-responding cell lines showed no evidence of GRP gene expression. These data support the concept that SCLC which constitutively express the GRP gene and L-myc but not c-myc or N-myc can be stimulated in an autocrine fashion by GRP or its congeners to increase [Ca2+]i by a pathway involving phosphatidylinositol turnover.

Topics: Bombesin; Calcium; Carcinoma, Small Cell; Cell Line; Choline; Gene Expression Regulation; Gramicidin; Humans; Lung Neoplasms; Membrane Potentials; Phosphatidylinositols; Potassium; Proto-Oncogenes; Tumor Cells, Cultured

A multidrug resistant variant (H69AR) of the human small cell lung cancer cell line NCI-H69 was obtained by culturing these cells in gradually increasing doses of Adriamycin up to 0.8 microM after a total of 14 months. H69AR expresses the multidrug resistant phenotype because it is cross-resistant to anthracycline analogues including daunomycin, epirubicin, menogaril, and mitoxantrone as well as to acivicin, etoposide, gramicidin D, colchicine, and the Vinca alkaloids, vincristine and vinblastine. H69AR is also similar to other multidrug resistant cell lines in that it displays little or no cross-resistance to bleomycin, 5-fluorouracil, and carboplatin. It has a slight collateral sensitivity to 1-dehydrotestosterone and lidocaine. H69AR has increased cell-cell adhesiveness compared to H69, but a similar growth rate in vitro and tumorigenicity in nude mice. When cultured in the absence of Adriamycin, there is a 40% decrease in resistance by 35 days of culture, compared to cells in continuous culture in drug, but no further decrease in resistance up to 181 days. Monoclonal antibodies to P-glycoprotein have no detectable reactivity with H69AR cells as determined by enzyme-linked immunosorbent assay and immunoblotting techniques. Thus, unlike most multidrug resistant cell lines, H69AR does not appear to express enhanced levels of P-glycoprotein. H69AR will provide a useful model for the study of multidrug resistance in human small cell lung cancer.

Topics: Animals; Antibodies, Monoclonal; ATP Binding Cassette Transporter, Subfamily B, Member 1; Carcinoma, Small Cell; Cell Line; Colchicine; Daunorubicin; Doxorubicin; Drug Resistance; Enzyme-Linked Immunosorbent Assay; Epirubicin; Etoposide; Glycoproteins; Gramicidin; Humans; Immunosorbent Techniques; Isoxazoles; Lung Neoplasms; Menogaril; Mice; Mice, Inbred BALB C; Mitoxantrone; Nogalamycin; Phenotype; Vinblastine; Vincristine