Fisetin, a phytochemical, potentiates sorafenib-induced apoptosis and abrogates tumor growth in athymic nude mice implanted with BRAF-mutated melanoma cells

Abstract

Melanoma is the most deadly form of cutaneous malignancy, and its incidence rates are rising worldwide. In melanoma, constitutive activation of the BRAF/MEK/ERK (MAPK) and PI3K/AKT/mTOR (PI3K) signaling pathways plays a pivotal role in cell proliferation, survival and tumorigenesis. A combination of compounds that lead to an optimal blockade of these critical signaling pathways may provide an effective strategy for prevention and treatment of melanoma. The phytochemical fisetin is known to possess anti-proliferative and pro-apoptotic activities. We found that fisetin treatment inhibited PI3K signaling pathway in melanoma cells. Therefore, we investigated the effect of fisetin and sorafenib (an RAF inhibitor) alone and in combination on cell proliferation, apoptosis and tumor growth. Combination treatment (fisetin + sorafenib) more effectively reduced the growth of BRAF-mutated human melanoma cells at lower doses when compared to individual agents. In addition, combination treatment resulted in enhanced (i) apoptosis, (ii) cleavage of caspase-3 and PARP, (iii) expression of Bax and Bak, (iv) inhibition of Bcl2 and Mcl-1, and (v) inhibition of expression of PI3K, phosphorylation of MEK1/2, ERK1/2, AKT and mTOR. In athymic nude mice subcutaneously implanted with melanoma cells (A375 and SK-MEL-28), we found that combination therapy resulted in greater reduction of tumor growth when compared to individual agents. Furthermore, combination therapy was more effective than monotherapy in: (i) inhibition of proliferation and angiogenesis, (ii) induction of apoptosis, and (iii) inhibition of the MAPK and PI3K pathways in xenograft tumors. These data suggest that simultaneous inhibition of both these signaling pathways using combination of fisetin and sorafenib may serve as a therapeutic option for the management of melanoma.

Potential therapeutic targets of epithelial–mesenchymal transition in melanoma

“…In vitro studies using A375 and SK-MEL-28 demonstrated that fisetin combined with sorafenib decreased invasion, migration, pMEK1/2, pERK1/2, PI3K activation (p110α), pAKT, and pmTOR while increasing PTEN. These results were confirmed in athymic nude mice [189]. Combination treatment using sorafenib and fisetin vigorously repressed migration, invasion, and expression of MMP-2 and MMP-9 compared with monotherapy.…”

Fisetin‐induced apoptosis of human oral cancer SCC‐4 cells through reactive oxygen species production, endoplasmic reticulum stress, caspase‐, and mitochondria‐dependent signaling pathways

“…It was assumed that CDC25C plays a role in the regulation of the CDK1/cyclin B complex for cell cycle progression . It was also reported that fisetin induced G2/M phase arrest in A431 epidermoid carcinoma cells . Results also showed that fisetin promoted the expression of Chk1 and ‐2 in SCC‐4 cells in time‐dependent manners.…”

Exploring the molecular targets of dietary flavonoid fisetin in cancer

“…It was demonstrated that melatonin potentiated the effect of fisetin in melanoma cells by activating cytochrome c-dependent apoptosis and inhibiting COX-2/iNOS and NF-κB/p300 signaling pathways [83]. Combination of fisetin and the BRAF inhibitor sorafenib was found to be extremely effective in inhibiting the growth of BRAF-mutated human melanoma cells resulting in enhanced apoptosis, reflected by cleavage of caspase-3 and PARP, increased expression of Bax and Bak, and inhibition of Bcl-2 and Mcl-1 [84]. In addition, synergistic effect of fisetin and sorafenib was observed in human cervical cancer HeLa cells, where i n vitro and in vivo studies revealed that the combination was clearly superior to sorafenib treatment alone.…”