myelin-basic-protein and Carcinoma--Squamous-Cell

Human brain myelin basic protein (MBP) distributes in nervous system and other tissues extensively, and can be detected in many kinds of tumor cells, such as lung cancer, breast cancer, and neuroglioma. However, it has not been reported whether MBP is relevant to the activity of neural invasion of tumors and whether MBP plays a role in biological behaviors of human lung cancer cells. This study was to investigate the inhibitory effect of MBP on hydrogen peroxide (H2O2)-induced apoptosis of human lung cancer cell line YTLMC-90.. YTLMC-90 cells were transfected with plasmid pSVCEPMBPCAT containing MBP cDNA minigene (test group), or empty vector pSVCEPCAT, or received no transfection (control group), and exposed to H2O2. The expression of MBP in YTLMC-90 cells was detected by Western blot. Cell proliferation was measured by MTT assay. The morphologic and ultra-structural changes of apoptotic cells were observed by microscopy with fluorescent staining of acridine orange (AO) and electron microscopy. The DNA fragmentation was examined by agarose gel electrophoresis.. After exposed to 200 micromol/L H2O2 for 24 h, the inhibitory rate of cell growth was significantly lower in test group than in empty vector group and control group (36.67% vs. 78.67% and 84.00%, P<0.001). The morphologic and biochemical changes of apoptotic cells, such as shrinkage of cytoplasm and nucleus, fragmentation of chromatin, and ladder pattern of DNA, were commonly observed in cells in control group, but these apoptotic features were not discovered in test group.. MBP markedly inhibits H2O2 cytotoxicity to YTLMC-90 cells through promoting cell proliferation and antagonizing H2O2-induced apoptosis.

Topics: Apoptosis; Carcinoma, Squamous Cell; Cell Line, Tumor; Cell Proliferation; DNA Fragmentation; DNA, Complementary; Humans; Hydrogen Peroxide; Lung Neoplasms; Myelin Basic Protein

Several non-small cell lung carcinomas (squamous cell carcinomas and adenocarcinomas) were analyzed for protein kinase activity. Soluble protein extracts derived from these tumors and from the lung parenchyma adjacent to the tumors were resolved by Mono Q anion exchange chromatography, and the fractions were assayed for phosphotransferase activity towards in vitro substrates. Myelin basic protein, casein, and a ribosomal S6-1 COOH-terminus peptide were efficient substrates for protein kinases that exhibited elevated phosphotransferase activity in the tumor extracts when compared to extracts derived from the adjacent nonneoplastic lung or from the lung parenchyma from patients with nonneoplastic lung disorders. Casein phosphotransferase activity was resolved into two peaks that eluted at 0.44 M NaCl and 0.56 M NaCl. The second peak was identified as casein kinase 2, based upon immunoreactivity to casein kinase 2-specific antipeptide antibodies and its sensitivity to inhibition by heparin sulfate. Myelin basic protein phosphotransferase activity eluted at 0.44 M NaCl, but Western blot analysis revealed that this could not be ascribed to mitogen-activated protein (MAP) kinases. This tumor associated protein kinase, designated p40TAK, exhibited a molecular mass of approximately 40 kDa upon gel filtration. In addition to myelin basic protein, it phosphorylated S6 peptide analogues and histone H1 on seryl residues. Like casein kinase 2, p40TAK exhibited elevated basal phosphotransferase activity in squamous cell carcinomas and adenocarcinomas of the lung when compared to the nonneoplastic lung parenchyma adjacent to the tumor.

Topics: Adenocarcinoma; Amino Acid Sequence; Antibodies; Blotting, Western; Carcinoma, Non-Small-Cell Lung; Carcinoma, Squamous Cell; Casein Kinases; Caseins; Chromatography, Ion Exchange; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Humans; Kinetics; Lung; Lung Neoplasms; Molecular Sequence Data; Myelin Basic Protein; Peptides; Phosphoserine; Phosphothreonine; Phosphotyrosine; Protein Kinases; Protein Serine-Threonine Kinases; Ribosomal Protein S6; Ribosomal Proteins; Substrate Specificity; Tyrosine