Integrin α11 regulates IGF2 expression in fibroblasts to enhance tumorigenicity of human non-small-cell lung cancer cells

doi:10.1073/pnas.0703040104

Integrin α11 regulates IGF2 expression in fibroblasts to enhance tumorigenicity of human non-small-cell lung cancer cells

*Ontario Cancer Institute and Princess Margaret Hospital, University Health Network, Toronto, ON, Canada M5G 2M9;
^†Department of Biomedicine, Division of Physiology, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway; and
Departments of ^§Medical Biophysics,
^¶Computer Science, and
^‖Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada M5G 2M9

Edited by Tak Wah Mak, The Campbell Family Institute for Breast Cancer Research, Toronto, ON, Canada, and approved June 1, 2007 (received for review April 2, 2007)

Abstract

Integrin α11 (ITGA11/α11) is localized to stromal fibroblasts and commonly overexpressed in non-small-cell lung carcinoma (NSCLC). We hypothesized that stromal α11 could be important for the tumorigenicity of NSCLC cells. SV40 immortalized mouse embryonic fibroblasts established from wild-type (WT) and Itga11-deficient [knockout (KO)] mice were tested for their tumorigenicity in immune-deficient mice when implanted alone or coimplanted with the A549 human lung adenocarcinoma cells. A549 coimplanted with the fibroblasts showed a markedly enhanced tumor growth rate compared with A549, WT, or KO, which alone formed only small tumors. Importantly, the growth was significantly greater for A549+WT compared with A549+KO tumors. Reexpression of human α11 cDNA in KO cells rescued a tumor growth rate to that comparable with the A549+WT tumors. These findings were validated in two other NSCLC cell lines, NCI-H460 and NCI-H520. Gene expression profiling indicated that IGF2 mRNA expression level was >200 times lower in A549+KO compared with A549+WT tumors. Stable short-hairpin RNA (shRNA) down-regulation of IGF2 in WT (WT_shIGF2) fibroblasts resulted in a decreased growth rate of A549+WT_shIGF2, compared with A549+WT tumors. The results indicate that α11 is an important stromal factor in NSCLC and propose a paradigm for carcinoma–stromal interaction indirectly through interaction between the matrix collagen and stromal fibroblasts to stimulate cancer cell growth.

Footnotes

**To whom correspondence should be addressed. Email: ming.tsao{at}uhn.on.ca
Author contributions: C.-Q.Z., S.N.P., and E.R.S.B. contributed equally to this work; C.-Q.Z., E.R.S.B., I.J., D.G., and M.-S.T. designed research; C.-Q.Z., S.N.P., E.R.S.B., D.B.-L., R.N., W.S., M. Li, M. Lu, and M.-S.T. performed research; S.N.P., D.B.-L., L.Z.P., D.G., and M.-S.T. contributed new reagents/analytic tools; C.-Q.Z., S.N.P., and M.-S.T. analyzed data; and C.-Q.Z., E.R.S.B., R.N., W.S., I.J., L.Z.P., D.G., and M.-S.T. wrote the paper.
↵ ^‡Present address: Sir Alastair Currie Cancer Research UK Laboratories, Molecular Medicine Centre, The University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh EH4 2XU, United Kingdom.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0703040104/DC1.
Abbreviations:

CAF,

carcinoma-associated fibroblast;

KI,

knockin;

KO,

knockout;

NSCLC,

non-small-cell lung carcinoma;

MEF,

mouse embryonic fibroblast;

q-RT-PCR,

quantitative RT-PCR;

SHRNA,

short-hairpin RNA.