Chemokine receptor CXCR4 expression in patients with melanoma and colorectal cancer liver metastases and the association with disease outcome

Abstract

Objective: To determine the role of chemokine receptor (CR) expression in patients with melanoma and colorectal cancer (CRC) liver metastases.

Summary background data: Murine and in vitro models have identified CR as potential factors in organ-specific metastasis of multiple cancers. Chemokines via their respective receptors have been shown to promote cell migration to distant organs.

Methods: Patients who underwent hepatic surgery for melanoma or CRC liver metastases were assessed. Screening cDNA microarrays of melanoma/CRC cell lines and tumor specimens were analyzed to identify CR. Microarray data were validated by quantitative real-time RT-PCR (qRT) in paraffin-embedded liver metastases. Migration assays and immunohistochemistry were performed to verify CR function and confirm CR expression, respectively.

Results: Microarray analysis identified CXCR4 as the most common CR expressed by both cancers. qRT demonstrated CXCR4 expression in 24 of 27 (89%) melanoma and 28 of 29 (97%) CRC liver metastases. In vitro treatment of melanoma or CRC cells with CXCL12, the ligand for CXCR4, significantly increased cell migration (P < 0.001). Low versus high CXCR4 expression in CRC liver metastases correlated with a significant difference in overall survival (median 27 months vs. 10 months, respectively; P = 0.036). In melanoma, low versus high CXCR4 expression in liver metastases demonstrated no difference in overall survival (median 11 months vs. 8 months, respectively; P = not significant).

Conclusions: CXCR4 is expressed and functional on melanoma and CRC cells. The ligand for CXCR4 is highly expressed in liver and may specifically attract melanoma and CRC CXCR4 (+) cells. Quantitative analysis of CXCR4 gene expression in patients with liver metastases has prognostic significance for disease outcome.

FIGURE 1. A, CXCR4 screening of CRC cell lines. B, CXCR4 screening of melanoma cell lines. Cell lines A and B (MA and MB), which were established from melanoma liver metastases, had the highest levels of CXCR4 gene expression.

FIGURE 2. A, CXCR4 gene expression in patients with CRC metastasis to the liver. B, CXCR4 expression in patients with melanoma metastasis to the liver.

FIGURE 3. Kaplan-Meier survival curves demonstrate prolonged overall survival in colorectal cancer patients whose liver metastases had lower CXCR4 expression (log-rank test, P = 0.036).

FIGURE 4. Kaplan-Meier curves demonstrate a nonsignificant increase in overall survival of melanoma patients whose liver metastases had low CXCR4 expression (log-rank test, P = 0.19).

FIGURE 5. A, Representative liver metastasis specimen demonstrating strong immunoreactivity of the CXCR4 protein in melanoma cells. B, Normal liver specimen demonstrating minimal to absent cytoplasmic immunostaining of the CXCR4 protein in hepatocytes (hematoxylin stain, original magnification ×400).