Silymarin Targets β-Catenin Signaling in Blocking Migration/Invasion of Human Melanoma Cells

Metastatic melanoma is a leading cause of death from skin diseases, and is often associated with activation of Wnt/β-catenin signaling pathway. We have examined the inhibitory effect of silymarin, a plant flavanoid from Silybum marianum, on cell migration of metastasis-specific human melanoma cell lines (A375 and Hs294t) and assessed whether Wnt/β-catenin signaling is the target of silymarin. Using an in vitro invasion assay, we found that treatment of human melanoma cell lines with silymarin resulted in concentration-dependent inhibition of cell migration, which was associated with accumulation of cytosolic β-catenin, while reducing the nuclear accumulation of β-catenin (i.e., β-catenin inactivation) and reducing the levels of matrix metalloproteinase (MMP) -2 and MMP-9 which are the down-stream targets of β-catenin. Silymarin enhanced: (i) the levels of casein kinase 1α, glycogen synthase kinase-3β and phosphorylated-β-catenin on critical residues Ser45, Ser33/37 and Thr41, and (ii) the binding of β-transducin repeat-containing proteins (β-TrCP) with phospho forms of β-catenin in melanoma cells. These events play important roles in degradation or inactivation of β-catenin. To verify whether β-catenin is a potent molecular target of silymarin, the effect of silymarin was determined on β-catenin-activated (Mel 1241) and β-catenin-inactivated (Mel 1011) melanoma cells. Treatment of Mel 1241 cells with silymarin or FH535, an inhibitor of Wnt/β-catenin pathway, significantly inhibited cell migration of Mel 1241 cells, which was associated with the elevated levels of casein kinase 1α and glycogen synthase kinase-3β, and decreased accumulation of nuclear β-catenin and inhibition of MMP-2 and MMP-9 levels. However, this effect of silymarin and FH535 was not found in Mel 1011 melanoma cells. These results indicate for the first time that silymarin inhibits melanoma cell migration by targeting β-catenin signaling pathway

Myc Stimulates Cell Cycle Progression Through the Activation of Cdk1 and Phosphorylation of p27

Cell cycle stimulation is a major transforming mechanism of Myc oncoprotein. This is achieved through at least three concomitant mechanisms: upregulation of cyclins and Cdks, downregulation of the Cdk inhibitors p15 and p21 and the degradation of p27. The Myc-p27 antagonism has been shown to be relevant in human cancer. To be degraded, p27 must be phosphorylated at Thr-187 to be recognized by Skp2, a component of the ubiquitination complex. We previously described that Myc induces Skp2 expression. Here we show that not only Cdk2 but Cdk1 phosphorylates p27 at the Thr-187. Moreover, Myc induced p27 degradation in murine fibroblasts through Cdk1 activation, which was achieved by Myc-dependent cyclin A and B induction. In the absence of Cdk2, p27 phosphorylation at Thr-187 was mainly carried out by cyclin A2-Cdk1 and cyclin B1-Cdk1. We also show that Cdk1 inhibition was enough for the synthetic lethal interaction with Myc. This result is relevant because Cdk1 is the only Cdk strictly required for cell cycle and the reported synthetic lethal interaction between Cdk1 and Myc.The work was supported by grant SAF2017-88026-R from MINECO, Spanish Government, to JL and MDD (partially funded by FEDER program from European Union). L.G.G. was recipient of FPI fellowship from Spanish Government. We are grateful Sandra Zunzunegui for technical assistance and John Sedivy and M. Dolores Delgado for helpful discussion

Outcomes of Resectability Assessment of the Dutch Colorectal Cancer Group Liver Metastases Expert Panel

BACKGROUND: Decision making on optimal treatment strategy in patients with initially unresectable colorectal cancer liver metastases (CRLM) remains complex because uniform criteria for (un) resectability are lacking. This study reports on the feasibility and short-term outcomes of The Dutch Colorectal Cancer Group Liver Expert Panel. STUDY DESIGN: The Expert Panel consists of 13 hepatobiliary surgeons and 4 radiologists. Resectability assessment is performed independently by 3 randomly assigned surgeons, and CRLM are scored as resectable, potentially resectable, or permanently unresectable. In absence of consensus, 2 additional surgeons are invited for a majority consensus. Patients with potentially resectable or unresectable CRLM at baseline are evaluated every 2 months of systemic therapy. Once CRLM are considered resectable, a treatment strategy is proposed. RESULTS: Overall, 398 panel evaluations in 183 patients were analyzed. The median time to panel conclusion was 7 days (interquartile range [IQR] 5-11 days). Intersurgeon disagreement was observed in 205 (52%) evaluations, with major disagreement (resectable vs permanently unresectable) in 42 (11%) evaluations. After systemic treatment, 106 patients were considered to have resectable CRLM, 84 of whom (79%) underwent a curative procedure. R0 resection (n = 41), R0 resection in combination with ablative treatment (n = 26), or ablative treatment only (n = 4) was achieved in 67 of 84 (80%) patients. CONCLUSIONS: This study analyzed prospective resectability evaluation of patients with CRLM by a panel of radiologists and liver surgeons. The high rate of disagreement among experienced liver surgeons reflects the complexity in defining treatment strategies for CRLM and supports the use of a panel rather than a single-surgeon decision. (C) 2019 by the American College of Surgeons. Published by Elsevier Inc. All rights reserved