Background: Metastasis is the leading cause of fatality in 90 % of cancer and approximately 60 % of patients will have metastasis at initial diagnosis. The striking similarity which exists between out-flux of tumor mass from the circulation and attraction of the circulating leucocytes to the injured site in inflammation points out to the possibility of same inflammatory mediators might be utilized for both purposes. . In this aspect, SP is a primary regulator of inflammatory extravasation and leukocyte adhesion to vascular endothelial cells. SP is highly expressed in several neoplasms, particularly metastatic lesions. Understanding the adhesion of cancer cells as rate limiting steps in metastasis, will improve outcome of cancer patients. We hypothesized that cancer utilizes the inflammatory mediator SP to adhere to EC, in acute phase, through inducing adhesion molecules expression in blood and solid tumor cell lines. The study was done with the following objectives; (1) to examine the adhesion of different tumor cell lines to endothelial cells and determine the effect of SP on this adhesion in acute phase (1-6). (2)To examine the expression of binding legends of endothelial adhesion molecules in those cell lines. (3) To examine the effect of SP treatment on the expression of these molecules. (4) To examine the effect of neurokinin receptor-1 antagonist (NK-1R) on the adhesion and adhesion molecule expression.
Methodology: We used Leukaemia cell line Jurkat (clone E6-1) and oral squamous cell carcinoma cell lines in different stages of the tumor (DOK, SCC25, CAL27, H157, and BICR22). Endothelial adhesion assay and fluorescence microscopy were used to quantify the adhesion of those cell lines to endothelial cells (HUV-EC-C) when treated with SP in acute phase. Flow cytometry was used to measure the adhesion molecules (CD49, CD11, and CD15s) in those cell lines. Statistical analysis was done with one-way ANOVA with P<0.05 considered statistically significant.
Results: Treatment of Jurkat, H157 cell lines with SP significantly increased adhesion to EC in a time dependent manner with a peak at 3 hours. Additionally, SP treatment increased the adhesion of CAL27 and DOK cell lines significantly at 3 hours. SP treatment significantly increased the CD49 (VLA-4) in both Jurkat and CAL27 in similar manner with a maximum threshold at 3 hours. Using the NK-1R inhibitor and V-CAM monoclonal antibody significantly inhibited the adhesion to EC as well as the adhesion molecule expression in both time and dose dependent manner compared with the TNF as positive control. Untreated oral cell lines showed increasing expression of their adhesion molecules in proportion to their malignant stages.
Conclusion: Adhesion of tumor cells and endothelial cells represents a critical step in tumor metastasis and extravasation4. This adhesion is vital for survival of tumor cells, therefore, it must occur within few hours of tumor cells entering the blood vessels (i.e. acute phase like inflammation). Our results, albeit requiring further in-vivo validation, highlights potential role for SP in acute adhesion and extravasation of tumor cells through EC. The study has important implications for the development of novel strategies for “Metastasis Prevention”.