OBJECTIVETo analyze the differential protein expression of left-sided colon cancer and right-sided colon cancer.

METHODSTissue samples of left-sided colon cancer (n=7) and right-sided colon cancer (n=7) were collected. Tissue protein was abstracted and two-dimensional gel electrophoresis (2-DE) was used to examine the gel images. Peptide mass fingerprintings (PMF) was acquired by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and the proteins were identified by data searching with bioinformatics. Immunohistochemical SP method was used for the detection of glucose regulated protein 78 kD (GRP78) and heat shock protein 20 (HSP20) in left-sided colon cancer (n=50) and right-sided colon cancer (n=50) tissues.

RESULTSSixteen differentiating protein spots were identified. Compared with right-sided colon cancer, 10 proteins including GRP78 up-regulated and 6 proteins including HSP20 down-regulated in left-sided colon cancer. Immunohistochemical detection showed that in left and right sided colon cancer, the positive expression rate of GRP78 was 78% (39/50) and 56% (28/50) and the positive expression rate of HSP20 was 34% (17/50) and 72% (36/50), respectively, and the differences were statistically significant (both P<0.05). The positive rate of GRP78 was associated with tumor differentiation, infiltration layer, TNM staging, lymph node metastasis, and liver metastasis, while the positive rate of HSP20 was associated with tumor gross morphology, TNM staging, and lymph node metastasis (P<0.05).

CONCLUSIONSThere are differentially expressed proteins between left-sided colon cancer and right-sided colon cancer, especially for GRP78 and HSP20, which may be the cause leading to the biological differences between left-sided and right-sided colon cancer.