Laminin-5 β3A expression in LNCaP human prostate carcinoma cells increases cell migration and tumorigenicity

Interactions between extracellular matrix proteins and prostate carcinoma cells change dramatically during prostate tumor progression. We have concentrated on two key modifications that occur in the hemidesmosome in prostate carcinoma: loss of laminin-5 protein expression and altered basal cell polarity of the α6β4 integrin. We previously demonstrated two cell line-specific isoforms (β3A and β3B) of the LAMB3 message. Cells expressing only the β3B isoform did not translate the β3 protein and were unable to assemble the laminin-5 trimer. One such cell line, LNCaP, was selected to determine whether restoration of the laminin-5 β3A isoform would cause expression of a functional laminin-5 β3 chain, assembly and secretion of the laminin-5 trimer, and reversion to a non-neoplastic phenotype. Laminin-5 β3A cDNA was cloned and stably transfected into LNCaP cells. We observed the restoration of the β3 protein, but a laminin-5 trimer was not secreted. Moreover, increased cell migration was demonstrated, and tumorigenicity was increased in SCID mice. A microarray analysis, performed between transfected and nontransfected LNCaP cells, showed most changing genes to be associated with signal transduction. The p3 chain of laminin-5 may thus play an important role in signal transduction, which may enhance cell motility and tumorigenesis.