Stromal-targeting with quercetin in patient-derived models of head and neck squamous cell carcinoma (HNSCC)

Abstract

Head and neck squamous cell carcinoma (HNSCC) is an aggressive cancer with a high recurrence rate. Recurrences occur in ~25% cases of early -stage patients (Stage I-II) and 50-60% cases of advanced stage (Stage II-IV) patients. Cumulative evidences suggest that tumor stroma, especially cancer-associated fibroblast (CAF) plays a protective role and contributes to drug-resistance in HNSCC, leading to recurrences after treatment. Quercetin is a flavonoid purified from natural plants, such as green tea, onions and berries. It has been reported to suppress CAFs and reduce collagen accumulation surrounding tumors, potentially facilitating drug delivery to tumors. Here, we hypothesize that quercetin targeting of CAFs may enhance the anti-tumor efficacy of cisplatin, and potentially other antitumor therapies in HNSCC. Using a primary co-culture system with primary HNSCC cells (70%) and the paired CAFs (30%) from HNSCC patients, we investigated the effect of quercetin and cisplatin combination treatment in vitro. We found that combination of quercetin and cisplatin elicited a significantly greater growth inhibition (70% of inhibition) as compared to 37% of inhibition with cisplatin and 15% of inhibition with quercetin alone. This result appeared to demonstrate some anti-CAF effects and antitumor effects exerted by this combination strategy.Using patient-derived HNSCC primary tumor cells, stromal-rich xenografts were successfully developed in vivo. The stromal-suppressive effect of quercetin was then examined upon treatment with increasing doses of quercetin (DMF, 2.5, 5 or 10 μM in 5 microliter volume, 2 times injection). Potential alteration of the tumor architecture by quercetin (vs. vehicle treatment) was examined by H&E staining. A marked reduction of stromal component was found in quercetin -treated tumors vs. vehicle-treated tumors. Importantly, we also found that these quercetin-treated tumors have 80.4% reduction in α-SMA protein expression (6.0% in vehicle vs.1.2% in treatment group), strongly indicating a significant stromal suppressive action of quercetin in an HNSCC primary culture-derived xenograft model. Furthermore, quercetin (10 μM) treatment reduced collagen expression by ~80% (vs. vehicle treatment) in the HNSCC primary culture-derived xenograft model by Masson’s trichrome staining. In conclusion, quercetin can effectively suppress the activated status of CAFs and may potentially enhance anti-tumor effect of cisplatin in an HNSCC patient-relevant manner. The antitumor efficacy of quercetin combination strategies should warrant further investigations.