The expression and prognostic impact of CXC-chemokines in stage II and III colorectal cancer epithelial and stromal tissue

Abstract

Background: The CXC-chemokine expression is linked with colorectal cancer (CRC) progression but their significance in resected CRC is unclear. We explored the prognostic impact of such expression in stage II and III CRC.

Methods: Tissue microarrays were constructed from stage II and III CRC biopsies (n=254), and the expression of CXCL1 and CXCL8, and their receptors CXCR1 and CXCR2, in malignant and adjacent normal tissue was graded by immunohistochemistry and was correlated with prognostic factors.

Results: Expression of CXCL1, CXCR1 and CXCR2 was elevated in tumour epithelium relative to normal adjacent tissue (P<0.001). CXCL8 expression was detectable in the peritumoural inflammatory infiltrate. There was no overall association between CXCL1, CXCR1 or CXCR2 expression and prognostic endpoints; however, univariate subgroup survival analysis demonstrated an inverse association between CXCL1 and recurrence-free survival (RFS) in stage III patients (P=0.041). The CXCL8 positivity in the tumour infiltrate, however, correlated with earlier disease stage (P<0.001) and improved relapse-free survival across the cohort (P<0.001). Disease stage (P<0.001) and tumour infiltrate CXCL8 positivity (P=0.007) were associated with enhanced RFS in multivariate Cox regression analysis.

Conclusion: Autocrine CXC-chemokine signalling may have adverse prognostic effects in early CRC. Conversely, CXCL8 positivity within the immune infiltrate may have good prognostic significance.

Figure 1

Immunohistochemical characterisation of CXC-chemokine and its receptor expression in colorectal tissue. (A) Representative high-powered images (magnification × 200) illustrating weak (left panel) and strong (right panel) immunoreactivity to antibodies used to characterize the expression of CXCR1, CXCR2 and CXCL1 in colorectal biopsy tissue. (B) Representative low-powered images showing differential expression of CXCL8 within the inflammatory cells surrounding the colorectal epithelial tissue.

Figure 2

Quantitative comparison of CXC-chemokine and its receptor expression in colorectal tissue. (A) Bar graphs presenting the relative immunoreactivity score calculated for CXCR1, CXCR2 and CXCL1 in normal and malignant colorectal epithelial cells. The mean expression in tumor and normal tissues was compared using Student's t-test. Malignant tissue showed significantly higher levels of expression of all three markers in comparison to the surrounding normal tissue; ^***P<0.001. (B) Bar graph illustrating the number of positive cases in which CXCL8 immunoreactivity was detected in the inflammatory cells surrounding the normal and malignant epithelial cells in the colorectal tissue. The majority of the cores with normal epithelium are absent for CXCL8 expression within the inflammatory infiltrate. In contrast, a greater number of cores with malignant epithelium show inflammatory cell CXCL8 positivity.

Figure 3

Relapse-free survival of stage II and III CRC patients, based on CXCL8 expression within the tumour inflammatory infiltrate. Kaplan–Meier curve representing the recurrence-free survival of stage II and stage III colorectal cancer patients. Samples were stratified on the basis of either positive or negative CXCL8 immunoreactivity within the infiltrating immune cells surrounding the tumor epithelium. Patients with a CXCL8 positive infiltrate were shown to have an increased relapse-free survival with the median interval not being reached. In contrast, patients with no CXCL8 immunoreactivity had a median survival of 69 months (P<0.01; log-ranks test).