Increased C-CRK proto-oncogene expression is associated with an aggressive phenotype in lung adenocarcinomas.
The C-CRK gene, cellular homolog of the avian v-crk oncogene, encodes two alternatively spliced adaptor signaling proteins, CRKI (28 kDa) and CRKII (40 kDa). Both CRKI and CRKII have been shown to activate kinase signaling and anchorage-independent growth in vitro and CRKI transformed cells readily form tumors in nude mice. Affymetrix oligonucleotide arrays were used to analyse 86 lung adenocarcinomas and 10 uninvolved lung tissues. C-CRK mRNA expression was increased in more advanced (stage III versus stage I), larger (T(2-4) versus T(1)), and poorly differentiated tumors and in tumors from patients demonstrating poor survival (P=0.00034). An overlapping series of 93 lung adenocarcinomas (64 stage I and 29 stage III) and 10 uninvolved lung specimens were measured for quantitative differences in CRKI and CRKII protein levels using 2-D PAGE. CRK protein spots were identified using mass spectrometry and 2-D Western blotting. A significant increase in levels of the CRKI oncoprotein and the phosphorylated isoform of CRKII was observed in tumors (P<0.05). No difference in protein level was evident between stages. Concordant with mRNA expression, CRKI and CRKII were increased in poorly differentiated tumors (P<0.05). CRK immunohistochemical analysis of tumor tissue arrays using the same tumor series also demonstrated increased abundance of nuclear and cytoplasmic CRK in more proliferative tumors (P<0.05). This study provides the first quantitative analysis of discrete CRKI and CRKII protein isoforms in human lung tumors and provides evidence that the C-CRK proto-oncogene may foment a more aggressive phenotype in lung cancers.
Miller
Charles T
CT
Department of Surgery, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Chen
Guoan
G
Gharib
Tarek G
TG
Wang
Hong
H
Thomas
Dafydd G
DG
Misek
David E
DE
Giordano
Thomas J
TJ
Yee
John
J
Orringer
Mark B
MB
Hanash
Samir M
SM
Beer
David G
DG
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D002455:Cell Division / Q000235:genetics; D015180:Electrophoresis, Gel, Two-Dimensional; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology*; D009361:Neoplasm Invasiveness; D010641:Phenotype; D020033:Protein Isoforms / Q000235:genetics; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured
C000715470:MAS1 protein, human; D020033:Protein Isoforms; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D012333:RNA, Messenger