Autocrine IL-6 production by human transitional carcinoma cells upregulates expression of the alpha5beta1 firbonectin receptor.
OBJECTIVE
Studies have demonstrated elevated expression and secretion of IL-6 by transitional cell carcinomas (TCC) following bacillus Calmette-Guerin (BCG) therapy. At present, the role of IL-6 on the biology of TCC is poorly understood. This study evaluated the influence of IL-6 expression on a critical variable regulating BCG-tumor interaction, the tumor expression of alpha5beta1 integrin.


METHODS
A human TCC cell line (253J) was transfected with an expression vector containing the full-length IL-6 cDNA sequence. Overexpression of IL-6 mRNA and protein was confirmed by Northern analysis and ELISA, respectively. Clones found to overexpress IL-6 were then assayed for alpha5beta1 expression using Northern analysis and flow cytometry. The effect of alterations in alpha5beta1 expression on tumor adherence to fibronectin (FN), and BCG adherence to tumor cells was determined using specific adherence assays.


RESULTS
mRNAs for both the alpha5 and beta1 subunits of the FN receptor were increased an average of 9.4 fold and 125.7 fold respectively in the IL-6 overexpressing transfectants relative to the parental 253J cells. Increased mRNA of alpha5 and beta1 was associated with increased cell surface expression of both proteins. Increased protein expression resulted in greater FN substrate binding affinity and increased adherence of BCG to tumor cells.


CONCLUSIONS
Autocrine expression of IL-6 upregulates the expression of FN receptor subunits in TCC. Increased alpha5beta1 expression increases cellular adherence to FN, and BCG adherence to tumor cells. These results suggest a role for IL-6 in mediating the antitumor activity of BCG by influencing BCG's adherence to TCC.
Zhang
G J
GJ
University of Iowa Department of Urology, Iowa City, Iowa, USA.
Crist
S A
SA
McKerrow
A K
AK
Xu
Y
Y
Ladehoff
D C
DC
See
W A
WA
D019898:Autocrine Communication; D001500:BCG Vaccine / Q000378:metabolism; D002295:Carcinoma, Transitional Cell / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D017469:Receptors, Fibronectin / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D001500:BCG Vaccine; D015850:Interleukin-6; D017469:Receptors, Fibronectin