Integrin alpha11 (ITGA11/alpha11) is localized to stromal fibroblasts and 
commonly overexpressed in non-small-cell lung carcinoma (NSCLC). We hypothesized 
that stromal alpha11 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 alpha11 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 alpha11 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.