Properties of classic protein kinase C in human small cell lung carcinoma NCI-H345 cells.
Bombesin-like peptides (BLPs) activate protein kinase C (PKC), which leads to proliferation in nonmalignant Swiss 3T3 cells. The purpose of this study was to determine if PKC expression in the classic human small cell lung carcinoma NCI-H345 cell line, which has an autocrine growth loop involving BLPs, exhibited unique properties that could result in malignant behavior. PKC activity and phorbol dibutyrate binding in NCI-H345 cells had properties similar to other reports. PKC activity in the cytosolic fraction increased to 100% as cells proliferated through lag, log, and plateau growth states. However, during the first 3 days after plating (lag growth state), 40-50% of the PKC activity was membrane associated, indicating a substantial portion in an activated form, possibly a result of BLP autocrine stimulation. NCI-H345 cells expressed the PKC isoenzymes alpha, beta, delta, sigma, and eta, but not gamma or epsilon, a pattern different from Swiss 3T3 cells or normal brain. further characterization of the Ca2+/phospholipid-dependent (classic) PKC isoenzymes, alpha and beta, showed that PKC beta was predominantly cytosolic (80%) as expected, but PKC alpha was primarily membrane associated (80-90%). Exposure of NCI-H345 cells to 200 nm phorbol 12-myristyl 13-acetate rapidly (within 2 min) decreased cytosolic PKC activity, with no change in the particulate activity, but did not alter [3H]-thymidine incorporation or subcellular distribution of PKC alpha or beta by Western blot. These results suggest altered PKC regulation in human small cell lung carcinoma NCI-H345 cells, which could contribute to their malignant behavior.
Jones
C L
CL
Medical Oncology Section, Denver Veterans Affairs Medical Center, Colorado 80220, USA.
Beck
L K
LK
Brozna
J P
JP
Holley
M
M
Dempsey
E J
EJ
Kane
M A
MA
D016475:3T3 Cells; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D018288:Carcinoma, Small Cell / Q000201:enzymology*; D002455:Cell Division; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008175:Lung Neoplasms / Q000201:enzymology*; D051379:Mice; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism; D011493:Protein Kinase C / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors; D014407:Tumor Cells, Cultured
D007527:Isoenzymes; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C