Defensive role of pleural mesothelial cell sialomucins in tumor metastasis.
OBJECTIVE
Sialomucin complex (SMC) is a heterodimeric glycoprotein, and is found on the surfaces of the mesothelia of the pleura, pericardium, and peritoneum. Sialomucins play a significant role in adhesion as well as in defense. In this study, we hypothesized that pleural mesothelial cells (PMCs) express SMC and thus prevent the adherence of ovarian cancer cells (HTB-77) to the pleura.


METHODS
PMCs were plated, and the adherence of HTB-77 cells was observed using a cytofluor. The PMC monolayer was pretreated with sialidase, and HTB-77 adherence was observed using cytofluor. In another set of HTB-77 cells, adherence was observed when the PMC monolayer was pretreated with supernatants of HTB-77 cells. Last, supernatants of HTB-77 cells were assayed for sialidase activity.


RESULTS
The removal of SMC by sialidase greatly increased the adherence of HTB-77 cells to the PMC monolayer, which was statistically significant (p < 0.05). Similar results were obtained when the PMC monolayer was pretreated with the supernatants of HTB-77 cells. Supernatants of HTB-77 cells showed the presence of sialidase.


CONCLUSIONS
The presence of SMC on the PMC acts as a defense layer, and its removal by sialidase increases the susceptibility of the PMC layer to the adherence of malignant cells and to increased metastasis. HTB-77 cells also express sialidase, which by its action on the monolayer aids in the adherence of tumor cells to the pleural surface.
Sharma
Ramit K
RK
Division of Pulmonary and Critical Care Medicine, Department of Medicine, Veterans Affairs Medical Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Mohammed
Kamal A
KA
Nasreen
Najmunnisa
N
Hardwick
Joyce
J
Van Horn
Robert D
RD
Ramirez-Icaza
Carlos
C
Antony
Veena B
VB
D002448:Cell Adhesion / Q000502:physiology; D005260:Female; D006801:Humans; D009077:Mucins / Q000502:physiology*; D009362:Neoplasm Metastasis / Q000517:prevention & control*; D009439:Neuraminidase / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000201:enzymology / Q000378:metabolism*; D010994:Pleura / Q000502:physiology*; D052116:Sialomucins; D014407:Tumor Cells, Cultured
D009077:Mucins; D052116:Sialomucins; D009439:Neuraminidase