Matrix metalloproteinase-7 activates heparin-binding epidermal growth factor-like growth factor in cutaneous squamous cell carcinoma

Background  Tumour-specific expression of matrix metalloproteinase (MMP)-7 has been noted in cutaneous squamous cell carcinomas (SCCs) in patients with recessive dystrophic epidermolysis bullosa (RDEB).

Objectives  To examine the potential role of MMP-7 in shedding of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in RDEB-associated and sporadic SCCs.

Methods  Tissue microarrays of RDEB-associated SCC (n = 20), non-EB SCC (n = 60) and Bowen disease (n = 28) were immunostained for MMP-7, CD44 variant 3 (CD44v3) and HB-EGF. Shedding of HB-EGF was studied in vitro using two cutaneous SCC cell lines.

Results  Immunohistochemical analysis showed that HB-EGF was absent in tumour cells when MMP-7 and CD44v3 colocalized, and that the absence of HB-EGF was more pronounced in RDEB-associated SCCs than in non-EB SCCs. The loss of HB-EGF in MMP-7–CD44v3 double-positive areas was interpreted to indicate shedding and activation of HB-EGF; this was also detected in Bowen disease indicating its importance in the early phase of SCC development. Specific knockdown of MMP-7 expression in human cutaneous SCC cells by small interfering RNA inhibited shedding of HB-EGF and resulted in diminished activation of the EGF receptor (EGFR) and ERK1/2, and in reduced proliferation of SCC cells.

Conclusions  These findings provide evidence for the role of MMP-7 in promoting the growth of cutaneous SCCs by shedding HB-EGF, and identify EGFR signalling as a potential therapeutic target in RDEB-associated SCC and unresectable sporadic cutaneous SCC.