Expression of SDF-1 alpha and nuclear CXCR4 predicts lymph node metastasis in colorectal cancer

Abstract

Although stromal cell-derived factor (SDF)-1 alpha and its receptor CXCR4 are experimentally suggested to be involved in tumorigenicity, the clinicopathological significance of their expression in human disease is not fully understood. We examined SDF-1 alpha and CXCR4 expression in colorectal cancers (CRCs) and their related lymph nodes (LNs), and investigated its relationship to clinicopathological features. Specimens of 60 primary CRCs and 27 related LNs were examined immunohistochemically for not only positivity but also immunostaining patterns for SDF-1 alpha and CXCR4. The relationships between clinicopathological features and SDF-1 alpha or CXCR4 expression were then analysed. Stromal cell-derived factor-1 alpha and CXCR4 expression were significantly associated with LN metastasis, tumour stage, and survival of CRC patients. Twenty-nine of 47 CXCR4-positive CRCs (61.7%) showed clear CXCR4 immunoreactivity in the nucleus and a weak signal in the cytoplasm (nuclear type), whereas others showed no nuclear immunoreactivity but a diffuse signal in the cytoplasm and at the plasma membrane (cytomembrane type). Colorectal cancer patients with nuclear CXCR4 expression showed significantly more frequent LN metastasis than did those with cytomembrane expression. Colorectal cancer patients with nuclear CXCR4 expression in the primary lesion frequently had cytomembrane CXCR4-positive tumours in their LNs. In conclusion, expression of SDF-1 alpha and nuclear CXCR4 predicts LN metastasis in CRCs.

Figure 1

Immunohistochemistry for SDF-1α in the normal colon and in CRC tissues. (A) Weak to negative immunoreactivity is observed in the cytoplasm of non-neoplastic epithelial cells. (B) Immunoreactivity for SDF-1α is also observed in the lymphoid follicle in the colonic mucosa. (C) Strong type: immunoreactivity is strongly detected in the cytoplasm of cancer cells. (D) Weak type: immunoreactivity is weakly detected in the cytoplasm of cancer cells. Immunoreactivity is also observed in the endothelial cells of the tumour stroma. Scale bars=100 μm.

Figure 2

Immunohistochemistry for CXCR4 in the normal colon and in CRC tissues. (A) Weak immunoreactivity is observed in the cytoplasm and plasma membrane of non-neoplastic epithelium cells. (B) Nuclear type: immunoreactivity is detected in the cytoplasm of cancer cells weakly and in the nuclei strongly. (C) Cytomembrane type: immunoreactivity is detected in the cytoplasm and plasma membrane of cancer cells. Scale bars=100 μm.

Figure 3

Subcellular localisation of CXCR4 in the CRC cell line HT29. (A) Immunohistochemistry. CXCR4 immunoreactivity is detected not only weakly at the plasma membrane but also strongly in the nuclei. (B) Western blot analysis. CXCR4 immunoreactivity is detected not only in the cytoplasmic and membranous (‘cytomembrane’) fraction but also in the nuclear (‘nuclear’) protein fraction from HT29 cells.

Figure 4

Expression of SDF-1α and CXCR4 in MTLNs. Representative photomicrographs of MTLNs, showing (A) strong SDF-1α expression and (B) cytomembrane-type CXCR4. Scale bars=100 μm.

Figure 5

Immunostaining pattern of CXCR4 in primary CRCs and MTLNs. MTLNs show significant cytomembranous immunoreactivity even when the primary tumours show nuclear immunoreactivity (n=27, P=0.012).

Figure 6

Overall survival according to (A) SDF-1α immunoreactivity; (B) CXCR4 immunoreactivity; and (C) CXCR4 immunostaining pattern in patients with CRCs (n=60). Kaplan–Meier survival curves were constructed and pairwise differences were analysed by log-rank test. Nega, negative; Cytom, cytomembrane; Nuc, nuclear.