Abstract
Obtaining protein profiles from a homogeneous cell population in tissues can significantly improve our capability in protein biomarker discovery. In this study, unique protein profiles from the top and bottom sections of mouse crypts and Apc(Min+/-) adenomas were obtained using laser capture microdissection (LCM) combined with MALDI MS. Statistically significant protein peaks with differential expression were selected, and a set of novel protein biomarkers were identified. Immunohistochemistry was performed to confirm the differentially expressed protein biomarkers found by LCM combined with MALDI MS. To validate the relevance of the findings in human colorectal cancer (CRC), S100A8 was further confirmed in human CRC using immunohistochemistry. In addition, S100A8 was found to have an increased expression at different human CRC stages (Duke's A-D) compared with controls at both protein (n = 168 cases) and RNA (n = 215 cases) levels. Overall LCM combined with MALDI MS is a promising method to identify intestinal protein biomarkers from minute amounts of tissue. The novel protein biomarkers identified from the top and bottom crypts will increase our knowledge of the specific protein changes taking place during cell migration from the crypt bottom to top. In addition, the identified cancer protein biomarkers will aid in the exploration of colorectal tumorigenesis mechanisms as well as in the advancement of molecularly based diagnosis of colorectal cancer.
Highlights
Obtaining protein profiles from a homogeneous cell population in tissues can significantly improve our capability in protein biomarker discovery
We aimed to identify a set of proteomic profiles that can differentiate murine top and bottom crypts and ApcMinϩ/Ϫ adenomas using laser capture microdissection (LCM) combined with MALDI MS
S100A8 Differential Expression in Human colorectal cancer (CRC)—To further analyze the differential expression of S100A8 at the protein level in human CRC, we examined its expression in a cohort of samples comprising 66 human normal controls and 104 CRC cases representing Duke’s stages A–D
Summary
Obtaining protein profiles from a homogeneous cell population in tissues can significantly improve our capability in protein biomarker discovery. Unique protein profiles from the top and bottom sections of mouse crypts and ApcMin؉/؊ adenomas were obtained using laser capture microdissection (LCM) combined with MALDI MS. Immunohistochemistry was performed to confirm the differentially expressed protein biomarkers found by LCM combined with MALDI MS. The ApcMinϩ/Ϫ mouse model, and other similar models based on truncating mutations in Apc, have been widely used to study intestinal neoplasia This model contains a germ line mutation in the adenomatous polyposis coli (Apc) munohistochemistry; Min, multiple intestinal neoplasia; WFCCM, weighted flexible compound covariate method; MDS, multidimensional scaling; MIF, macrophage migration inhibitory factor; DAPK, death-associated protein kinase; CRIP, cysteine-rich intestinal protein. The ApcMinϩ/Ϫ mouse is a promising mouse model for the discovery of potential early CRC markers using a proteomics approach
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