Chronic exposure to
carcinogens represents the major risk factor for
head and neck squamous cell carcinoma (
HNSCC). Beverages derived from broccoli sprout extracts (BSE) that are rich in
glucoraphanin and its bioactive metabolite
sulforaphane promote detoxication of airborne
pollutants in humans. Herein, we investigated the potential chemopreventive activity of
sulforaphane using in vitro models of normal and malignant mucosal epithelial cells and an in vivo model of murine
oral cancer resulting from the
carcinogen 4-nitroquinoline-1-oxide (4NQO).
Sulforaphane treatment of Het-1A, a normal mucosal epithelial cell line, and 4
HNSCC cell lines led to dose- and time-dependent induction of NRF2 and the NRF2 target genes NQO1 and GCLC, known mediators of
carcinogen detoxication.
Sulforaphane also promoted NRF2-independent dephosphorylation/inactivation of pSTAT3, a key oncogenic factor in
HNSCC. Compared with vehicle,
sulforaphane significantly reduced the incidence and size of 4NQO-induced tongue
tumors in mice. A pilot clinical trial in 10 healthy volunteers evaluated the bioavailability and pharmacodynamic activity of three different BSE regimens, based upon urinary
sulforaphane metabolites and NQO1 transcripts in buccal scrapings, respectively. Ingestion of
sulforaphane-rich BSE demonstrated the greatest, most consistent bioavailability. Mucosal bioactivity, defined as 2-fold or greater upregulation of NQO1
mRNA, was observed in 6 of 9 evaluable participants ingesting
glucoraphanin-rich BSE; 3 of 6 ingesting
sulforaphane-rich BSE; and 3 of 9 after topical-only exposure to
sulforaphane-rich BSE. Together, our findings demonstrate preclinical chemopreventive activity of
sulforaphane against
carcinogen-induced
oral cancer, and support further mechanistic and clinical investigation of
sulforaphane as a chemopreventive agent against tobacco-related
HNSCC.
Cancer Prev Res; 9(7); 547-57. ©2016 AACR.