Scutellarin inhibits the invasive potential of malignant melanoma cells through the suppression epithelial-mesenchymal transition and angiogenesis via the PI3K/Akt/mTOR signaling pathway

Abstract

Malignant melanoma is the leading cause of death from skin disease, due in large part to its propensity to metastasize. Scutellarin is an active flavone extracted from traditional Chinese herb Erigeron breviscapus (Vant.) Hand. Mazz. Recent studies have reported that scutellarin can be utilized to treat various types of tumors. In this study, we investigated the effects of scutellarin on melanoma cancer cell invasive potential and the molecular mechanisms underlying these effects using A375 melanoma cells lines. The in-vitro antitumor activity of scutellarin was evaluated by CCK-8 assay, wound-healing assay, transwell assays, adhesion assays, and tube formation assays to assess the cell viability, migration, invasion, adhesion, and angiogenesis, respectively. Also, western blotting assay was used to assess the level of PI3K/Akt/mTOR signaling pathway proteins in A375 cells. We found that scutellarin significantly inhibited melanoma cell lines and HUVECs viability in a time- and concentration-dependent manners. Additionally, scutellarin effectively suppressed tumor cell migration, invasion, adhesion through the suppression of EMT and angiogenesis by inhibiting the PI3K/Akt/mTOR signaling pathway. These results indicated that scutellarin could markedly inhibit the invasive potential of melanoma cell lines by suppressing the EMT and angiogenesis through the PI3K/Akt/mTOR signaling pathway. It suggests that scutellarin might be a potential compound in malignant melanoma treatment.

Introduction

Malignant melanoma of the skin is the leading cause of mortality from skin cancer (Saraya et al., 2018). Malignant melanoma is particularly deadly due to its propensity to metastasize, and approximately 20–25% of patients with malignant melanoma die of metastasis (Gastman et al., 2019). Although significant progress has been made in therapeutics for melanoma, metastasis is still the leading cause of the skin-related death. Therefore, it is very urgent to develop an effective compound for inhibiting melanoma metastasis.

Metastasis of melanoma is a multistep process involving the migration of tumor cells, local invasion, entry into the circulation, arrest at secondary sites, extravasation, and colonization (Cheng et al., 2017). Numerous studies implicate that epithelial-mesenchymal transition (EMT) is a well-described process not only involved in developmental processes but also in metastasis and chemotherapy resistance of cancer cells (Asnaghi et al., 2015; Hintsala et al., 2017). During the processes of EMT, cells lose their epithelial traits and obtain mesenchymal properties, such as the down-regulation E-cadherin and up-regulation of N-cadherin and Vimentin, resulting in weakened adhesion ability and enhanced motility (Ryu et al., 2017). A critical step in metastasis process is an invasion into tissues, which require proteolytic degradation of extracellular matrix (ECM) components (Erdogan and Webb, 2017). Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteinases that cleave ECM components. MMPs play an important role in cell proliferation, angiogenesis, and apoptosis. Among them, MMP-2 and MMP-9 have been identified as major critical molecules that assist melanoma cells during metastasis (Wang et al., 2018). In addition, tumor angiogenesis, one of the essential hallmarks of cancer, is critical for the growth and metastasis of cancer cells which supply oxygen and nutrients and dispose of catabolic products (Park et al., 2018). Thus, the exploration of effective natural compounds targeting EMT and angiogenesis has been an efficient therapeutic approach for the treatment of metastatic cancers. (Shi and Zhou, 2018).

Scutellarin is an active flavone extracted from the Chinese traditional herb Erigeron breviscapus (Vant.) Hand. Mazz., which was clinically used to treat patients with ischemic heart diseases and cerebral vascular diseases (Chledzik et al., 2018; Wang et al., 2016). Recent studies have reported that scutellarin can be used to treat various types of tumors, such as hepatocellular carcinoma, colorectal cancer, and tongue squamous carcinoma, although the underlying mechanisms have not been entirely determined (Deng et al., 2018; Han et al., 2014; Yang et al., 2017). However, so far, little is known about whether scutellarin could inhibit the metastasis of melanoma.

In this study, we analyzed the anti-tumor effect of scutellarin on melanoma cells and determined whether scutellarin could reduce the invasive potential of malignant melanoma cells through the suppression EMT and angiogenesis via the PI3K/Akt/mTOR signaling.