Fig. 4.

The OPN receptor on the MSC membrane plays a vital role in MSC recruitment and adhesion to lung cancer cells. (A-C) CM was collected from A549-L cells. MSCs were treated with αvβ1, αvβ3, αvβ5, or CD44 siRNAs for 24 h. The CM was placed into the lower chamber of a Transwell assay and MSCs were placed into the upper chamber. The Transwell assay examined MSC recruitment. (D-F) MSCs were treated with αvβ1, αvβ3, αvβ5, or CD44 siRNAs for 24 h. A549-L cells were seeded into 24-well plates and co– cultivated with the MSCs. An adhesion assay examined levels of adhesion with lung cancer cells. (G) The model shows how cigarette smoke induces increases in OPN expression in lung cancer cells and OPN binding with OPN receptors on MSC cell membranes stimulates the recruitment and adhesion of MSCs to lung cancer cells. All results are expressed as the mean ± SD of three independent samples. *p < 0.05 compared with the parental group; #p < 0.05 compared with 1 μM B[α]P or 1% CSE treatment.