Microarray analysis of the differential transformation mediated by Kirsten and Harvey Ras oncogenes in a human colorectal adenocarcinoma cell line.
Colorectal cancer arises after a series of mutational events in the colon epithelia and is often used as a model of the multistep progression of tumorigenesis. Mutations in Ki-Ras have been detected in some 50% of cases and are thought to occur at an early stage. Almost never do mutations arise in the loci of other Ras isoforms (Ha- and N-), leading to the assumption that Ki-Ras plays a unique role in tumorigenesis. In order to examine the distinctive function that Ki-Ras plays in cancer development in the colon, we introduced constitutively active mutant Ki- and Ha-Ras genes into an intermediate-stage colon adenoma cell line (Caco-2). We found that mutant active Ha-RasV12 was more efficient at transforming these colon epithelial cells as assessed by anchorage-independent growth, tumor formation in SCID mice and the development of mesenchymal morphology compared to transformation by Ki-RasV12. We conducted microarray analysis in an attempt to reveal the genes whose aberrant expression is a direct result of overexpression of either Ki-RasV12 or Ha-RasV12. We used Clontech's Atlas cancer cDNA (588 genes) and RZPD's Onco Set 1 (1,544 genes) arrays. We identified fewer genes that were commonly regulated than were differentially expressed between Ki- and Ha-RasV12 isoforms. Specifically, we found that Ki-RasV12 regulated genes involved in cytokine signaling, cell adhesion and colon development, whereas Ha-RasV12 mainly regulated genes involved in controlling cell morphology, correlating to an epithelial-mesenchymal transition only observed in these cells. Our results demonstrate how 2 Ras isoforms regulate disparate biologic processes, revealing a number of genes whose deregulated expression may influence colon carcinogenesis (supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html).
Roberts
Michael L
ML
Institute of Biologic Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
Drosopoulos
Konstantinos G
KG
Vasileiou
Ioannis
I
Stricker
Mona
M
Taoufik
Era
E
Maercker
Christian
C
Guialis
Apostolia
A
Alexis
Michael N
MN
Pintzas
Alexander
A
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D020869:Gene Expression Profiling; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008648:Mesoderm; D051379:Mice; D016513:Mice, SCID; D009154:Mutation / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004273:DNA, Neoplasm; D020033:Protein Isoforms