Malignant melanoma (MM) is one of the most malignant tumors and has a very poor prognosis. However, there are no effective drugs to treat this disease. As a kind of iron flavin dependent enzyme, dihydroorotate dehydrogenase (DHODH, EC 1.3.3.1) is the fourth and a key enzyme in the de novo biosynthesis of pyrimidines. Herein, we found that DHODH inactivation/deficiency inhibited melanoma cell proliferation, induced cell cycle arrest at S phase and lead to autophagy in human melanoma cells. Meanwhile, leflunomide treatment induced cell apoptosis and deficiency of DHODH sensitized cells to drug-induced apoptosis in BCL-2 deficient melanoma cells, while not in BCL-2 abundant melanoma cells. Then we found that BCL-2 could rescue apoptosis induced by DHODH inactivation/deficiency. Moreover, BCL-2 also showed to promote cell cycle arrest and to inhibit autophagy induced by leflunomide. To explore the mechanisms underlying autophagy induced by DHODH inhibition, we found that AMPK-Ulk1 axis was activated in this process. Besides, JNK was phosphorylated and activated to phosphorylate BCL-2, which abrogated the interaction between BCL-2 and Beclin1 and then abolished autophagy. Our findings provided evidences for the potential of DHODH used as a drug target for melanoma treatment.

Purpose: Alkaloids are naturally occurring chemical compounds that are widely distributed in plants, and have pharmaceutical values and low toxicity. In recent years, some of them have been demonstrated to be promising therapeutic drug candidates for cancer treatment. Herein, we tried to explore the antitumor effect of dehydrocorydaline (DHC), a natural alkaloid isolated from Corydalis , on malignant melanoma. Methods: We treated two malignant metastatic melanoma cell lines, A375 and MV3, and a normal melanocyte cell line, PIG1, with various concentrations of DHC for set amounts of time, and detected cell proliferation, migration, and invasion by using MTT, BrdU, transwell, Western blot and soft agar assay in vitro and tumorigenicity in the xenografts in vivo. Results: Our results showed that DHC dramatically blocked cell proliferation and led to cell cycle arrest at G0/G1 phase and downregulated the expressions of cell cycle regulators CDK6 and Cyclin D1 in melanoma cells. However, DHC had little inhibitory effect on normal melanocyte cell line PIG-1. Meanwhile, DHC suppressed cell invasion and migration through modulating the epithelial–mesenchymal transition (EMT) markers including E-cadherin, vimentin, as well as β-catenin. In addition, DHC also significantly attenuated tumor growth in vivo. The expressions of cell cycle-related and metastasis-related proteins were further confirmed by immunohistochemical staining in the xenografts. Importantly, MEK1/2-ERK1/2 cascade was inactivated after DHC treatment and ERK activator t-butylhydroquinone (tBHQ) treatment rescued DHC-induced cell proliferation inhibition. Conclusions: Our results indicated that DHC inhibited cell proliferation and migration/invasion via inactivating MAPK signaling, and showed that DHC might be a potential novel drug to treat malignant melanoma.

As a critical subunit of the constitutive photomorphogenesis 9 (COP9) signalosome (CSN), CSN6 is upregulated in some human cancers and plays critical roles in tumorigenesis and progression, but its biological functions and molecular mechanisms in melanoma remain unknown. Our study showed that CSN6 expression was upregulated in melanoma patients and cells, and correlated with poor survival in melanoma patients. In melanoma cells, CSN6 knockdown remarkably inhibited cell proliferation, tumorigenicity, migration, and invasion, whereas CSN6 recovery rescued the proliferative and metastatic abilities. Notably, we identified that CSN6 stabilized CDK9 expression by reducing CDK9 ubiquitination levels, thereby activating CDK9-mediated signaling pathways. In addition, our study described a novel CSN6-interacting E3 ligase UBR5, which was negatively regulated by CSN6 and could regulate the ubiquitination and degradation of CDK9 in melanoma cells. Furthermore, in CSN6-knockdown melanoma cells, UBR5 knockdown abrogated the effects caused by CSN6 silencing, suggesting that CSN6 activates the UBR5/CDK9 pathway to promote melanoma cell proliferation and metastasis. Thus, this study illustrates the mechanism by which the CSN6-UBR5-CDK9 axis promotes melanoma development, and demonstrate that CSN6 may be a potential biomarker and anticancer target in melanoma.

Dihydrocapsaicin (DHC) is one of the main components of capsaicinoids in Capsicum. It has been reported that DHC exerts anti-cancer effects on diverse malignant tumors, such as colorectal cancer, breast cancer, and glioma. However, studies focused on the effect of DHC upon melanoma have rarely been done. In the present study, melanoma A375 and MV3 cell lines were treated with DHC and the cell proliferation, migration, and invasion were significantly suppressed. Furthermore, DHC effectively inhibited xenograft tumor growth and pulmonary metastasis of melanoma cells in NOD/SCID mice model. It was identified that β-catenin, which plays significant roles in cell proliferation and epithelial-mesenchymal transition, was down-regulated after DHC treatment. In addition, cyclin D1, c-Myc, MMP2, and MMP7, which are critical in diverse cellular process regulation as downstream proteins of β-catenin, were all decreased. Mechanistically, DHC accelerates ubiquitination of β-catenin and up-regulates the beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC) in melanoma cells. The DHC induced suppression of cell proliferation, migration, and invasion were partly rescued by exogenous β-catenin overexpression, both in vitro and in vivo. Taken together, DHC may serve as a candidate natural compound for human melanoma treatment through β-catenin pathway.

The plasma skin regeneration (PSR) system is a safe device for skin regeneration, which is usually carried out under local anesthetic to control the pain. Topical anesthesia and subcutaneous infiltration anesthesia are the common and safe anesthetizations. This study was undertaken to evaluate the effects of PSR after using topical anesthetization as compared with subcutaneous infiltration anesthesia, thereby inquiring into the effect of subcutaneous infiltration anesthesia in PSR and increasing electivity for clinical work. 14 Sprague Dawley rats were randomly utilized in this experiment. After adequate sedation and depilation, the rat's back was randomly divided into three experimental regions marked as A, B, and C. A and B were treated with lidocaine cream and lidocaine hydrochloride, respectively, before PSR. C was treated solely with PSR without any anesthesia. Biopsies were taken from all treatment sites at 4 and 30 days after treatment to observe the skin necrosis and thickness of new collagen fiber. Histopathologic examination was performed by observers blinded to the treatment conditions. In this analysis, there was a statistically significant reduction (P < 0.01) in the skin necrosis and thickness of new collagen fiber in the topical anesthesia group compared with that in the other two groups, while a statistically significant increase (P< 0.01) in the subcutaneous infiltration anesthesia group. The results suggest that subcutaneous infiltration anesthesia group showed a deeper range of tissue effects via the treatment of PSR as compared with the topical anesthesia and the control groups. Meanwhile, the effect of the topical anesthesia was the lowest. So we conclude that subcutaneous infiltration anesthesia for PSR treatment was superior to that of the topical anesthesia.