Metaplastic breast carcinoma (MBC) is a rare subtype of invasive breast
cancer and has poor prognosis. In general, cancers are heterogeneous
cellular masses comprised of different cell types and their
extracellular matrix (ECM). However, little is known about the
composition of the ECM and its constituents in MBC. Decorin is a
ubiquitous ECM macromolecule known of its oncosuppressive activity. As
such, it provides an intriguing molecule in the development of novel
therapeutics for different malignancies such as MBC. In this study,
decorin immunoreactivity and the effect of adenoviral decorin cDNA
(Ad-DCN) transduction were examined in MBC. Multiple immunohistochemical
stainings were used to characterize a massive breast tumour derived
from an old woman. Furthermore, three-dimensional (3D) explant cultures
derived from the tumour were transduced with Ad-DCN to study the effect
of the transduction on the explants. The MBC tumour was shown to be
completely negative for decorin immunoreactivity demonstrating that the
malignant cells were not able to synthesize decorin. Ad-DCN transduction
resulted in a markedly altered cytological phenotype of MBC explants by
decreasing the amount of atypical cells and by inhibiting cell
proliferation. The results of this study support approaches to develop
new, decorin-based adjuvant therapies for MBC.