Metastasis is a lethal attribute of a cancer and presents a continuing therapeutic challenge. Metastasis is a highly complex process and more knowledge about the mechanisms behind metastasis is highly desirable. Isogenic CMT cell lines were selected from a spontaneous mouse lung adenocarcinoma and characterized in vivo to have different metastatic potential. In this study, the comprehensive protein expression profiles of three of these CMT cell lines at passage 5, 15 and 35 were analyzed by 2-DE separation followed by MS identification. As a result, 82 and 40 unique proteins were found to be significantly up- or down-regulated between cell lines with different metastatic potential at passages 5 and 15, respectively. These proteins were identified by MS and most of them have previously been reported to be related to cancer development and/or metastasis. Bioinformatics analysis indicated that several of the proteins were involved in proteasome, cell-cycle and cell-communication pathways. Among them, some keratins, 14-3-3 proteins and 26S proteasome proteins were identified and their aberrant expression may be directly or indirectly involved in cancer development and metastasis. In conclusion, our comprehensive 2-DE-based proteomics studies revealed some candidate proteins, protein families and signaling pathways, which might be important in cancer development and metastasis.