Lung cancer cell invasion and expression of intercellular adhesion molecule-1 (ICAM-1) are attenuated by secretory phospholipase A₂ inhibition

Abstract

Objective: Invasive lung tumors are associated with intercellular adhesion molecule-1 (ICAM-1) expression. Secretory phospholipase A(2) (sPLA(2)) enzymes produce inflammatory mediators that stimulate ICAM-1 expression, and upregulation of PLA(2) activity can enhance metastasis. We hypothesize a link between sPLA(2) activity, ICAM-1 expression, and tumor cell invasion. We propose that inhibition of sPLA(2) modulates ICAM-1 expression in cancer cells and attenuates their invasiveness.

Methods: Human lung adenocarcinoma cells (A549) were treated with an ICAM-1 blocking antibody and assayed for invasion. Lung cancer cells (A549 and H358) were then treated with an sPLA(2) inhibitor and evaluated by immunoblotting for ICAM-1 expression. Next cells (A549) treated with sPLA(2) inhibitor were assayed for invasion. Finally, sPLA(2) messenger RNA and protein expression were evaluated by quantitative reverse-transcriptase polymerase chain reaction and immunofluorescence microscopy, respectively. Statistical analysis was performed by the Student t test or analysis of variance, as appropriate.

Results: Antibody blockade of ICAM-1 decreased lung cancer cell invasion. sPLA(2) inhibition significantly reduced ICAM-1 expression and invasion. sPLA(2) inhibition also significantly decreased sPLA(2) mRNA expression and immunofluorescent staining of sPLA(2).

Conclusions: sPLA(2) plays a significant role in mediating the inflammatory signals that induce ICAM-1 expression in lung cancer cells. Inhibition of the enzyme can significantly decrease ICAM-1 expression and subsequent cancer cell invasion. This lays the groundwork for further investigation into the cellular mechanisms of sPLA(2) and its role in lung cancer.