Fenretinide (4-HPR) Suppresses Transformed Keratinocyte Migration: An Additional Chemopreventive Mechanism

Epithelial cell conversion to a mobile phenotype is essential for growth and wound healing. The epithelial-mesenchymal transition (EMT) that occurs in precancerous oral lesions, however, is an aberrant variant of wound healing that facilitates malignant transformation.  The cancer preventing agent, fenretinide, is well-recognized for its abilities to induce keratinocyte differentiation and/or apoptosis. Recent literature shows that a fenretinide metabolite perturbs microtubule formation.

Objectives: This study evaluated whether fenretinide’s chemopreventive effects extend beyond growth state regulation to include modulation of cell motility.

Methods: A continuum of cell lines ranging from normal oral keratinocytes (HOK3437), dysplastic keratinocytes (HOKs transfected with HPV E6/E7) and two oral squamous cell carcinoma (OSCC) cell lines (SCC15 and SCC2095) were treated with 1 and 5μM fenretinide. Fenretinide’s effects on: 1) cell proliferation and viability (hemocytometer counts and trypan blue exclusion, post 24h, 48h, 72h, 96h treatment) and 2) cell motility (0h, 24h, 48h, 72h area analyses of wound healing) were assessed. ANOVA (Bonferroni post hoc) and Kruskal-Wallis (Dunn’s Multiple Comparison post hoc) statistical analyses were used. 

Results: While 5µM fenretinide reduced SCC-cell proliferation related to matched controls (SCC15 + SCC2095 p<0.05, 72h; SCC2095 p<0.01, 96h; n=4), viabilities were comparable among all SCC cultures. Fenretinide elicited a concentration-dependent effect on dysplastic cells, which demonstrated a marked decrease in viability after treatment (control vs 5μM p<0.05, over time-course; n=4).  In contrast, HOK3437 keratinocytes experienced no adverse effects in terms of proliferation or viability. Cell migration assays demonstrated both 1&5μM fenretinide significantly inhibited SCC15 and SCC2095 cell lines (p<0.0001, n>18). Wound healing in dysplastic and normal HOK3437 cells was only significantly affected at the final 72h time point (p<0.0001, n=18). Studies to elucidate mechanisms responsible for fenretinide’s inhibitory effects on migration are ongoing.

Conclusions: These data imply that fenretinide’s multimodal chemopreventive effects extend to controlled regulation of cell motility.