Aberrant Elevation of Tyrosine‐specific Phosphorylation in Human Gastric Cancer Cells

Abstract

Phosphotyrosine‐containing proteins in various human cancer cell lines were studied by immunoblotting with anti‐phosphotyrosine antibody. Of 29 cell lines derived from oral epidermoid cancer, esophageal cancer, gastric cancer, colon cancer, pancreatic cancer, hepatocellular carcinoma and malignant melanoma, 3 of the 6 gastric cancer cells showed aberrant elevation of tyrosine‐speciflc phosphorylation. On the other hand, both esophageal cancer cells and colon cancer cells, which were reported to have amplified epidermal growth factor receptor and activated p60v‐src kinase, respectively, showed no apparent elevation of tyrosine‐specific phosphorylation, and their profiles of phosphorylation were similar to that of normal human fibroblasts. Two gastric cancer cells, NUGC‐4 and MKN‐45, showed similar profiles of phosphorylation but their responses to growth factors differed from each other. Tyrosine phosphorylation in NUGC‐4 was strongly activated by treatment with epidermal growth factor and quickly reduced by the acid treatment which is effective in removing growth factors from cellular surface receptors. On the contrary, phosphorylation in MKN‐45 did not respond to either growth factor or acid treatment. These results suggest that NUGC‐4 and MKN‐45 have tyrosine kinases which are activated by different mechanisms but share similar substrates.

Preclinical study of a “tailor-made” combination of NK4-expressing gene therapy and gefitinib (ZD1839, Iressa™) for disseminated peritoneal scirrhous gastric cancer

“…A constant phosphorylation of EGFR tyrosine kinase without the binding of ligands has been reported in MKN45 gastric cancer cells. 36 Gefitinib-resistance in GT3TKB and HSC45 might be induced by a similar maintenance of phosphorylation, and this will be investigated by further studies. Altogether, the tailor-made approach to gefitinib-mediated chemotherapy based on pretreatment evaluation of gefitnib-sensitivity is an attractive strategy.…”

Tyrosine phosphorylation of 100-130 kDa proteins in lung cancer correlates with poor prognosis

“…Tyrosine phosphorylation of similar proteins was widely observed in other cell lines derived from oesophageal, gastric and colon cancer (Figure lb). To assess the specificity of anti-pTyr antibody, we examined the inhibitory effect of the phosphoamino acids upon antibody-antigen recognition as previously described (Takeshima et al, 1991). Addition of 5 mM pTyr to the antipTyr antibody solution completely blocked the detection of these proteins, indicating that these proteins were indeed tyrosine phosphorylated (data not shown).…”

“…To analyse the signalling through tyrosine phosphorylation in human cancer, we have studied phosphotyrosine (pTyr)-containing proteins in various cancer cell lines with anti-pTyr antibody (Hamaguchi et al, 1988;Takeshima et al, 1991). To obtain more clues, we examined pTyrcontaining proteins in lung cancer tissues surgically resected from patients.…”

“…Cell lysates were prepared as described previously (Takeshima et al, 1991). Frozen tissue samples were crushed into fine pieces, suspended in a buffer containing 2% sodium dodecyl sulphate (SDS) and 5% mercaptoethanol, and immediately homogenised.…”

Altered regulation of Src upon cell detachment protects human lung adenocarcinoma cells from anoikis

“…There have been many studies showing that Src protein level or its kinase activity is increased in a variety of human cancers, such as lung cancer (Mazurenko et al, 1992), breast cancer (Jacobs and Rubsamen, 1983;Muthuswamy et al, 1994;Verbeek et al, 1996;Egan et al, 1999), colon cancer (Bolen et al, 1987;Cartwright et al, 1989Cartwright et al, , 1990Cartwright et al, , 1994Weber et al, 1992;Termuhlen et al, 1993;Windham et al, 2002), pancreatic cancer (Lutz et al, 1998), ovarian cancer (Budde et al, 1994;Wiener et al, 1999), neural cancer (Bolen et al, 1985;Bjelfman et al, 1990), esophageal cancer (Kumble et al, 1997), gastric cancer (Takeshima et al, 1991), melanoma (Bjorge et al, 1996), and Kaposi's sarcoma (Munshi et al, 2000). All these studies suggest that Src plays important roles in the occurrence and development of human cancers.…”