GNS561, a New Autophagy Inhibitor Active against Cancer Stem Cells in Hepatocellular Carcinoma and Hepatic Metastasis from Colorectal Cancer

Abstract

Patients with advanced hepatocellular carcinoma (HCC) or metastatic colorectal cancer (mCRC) have a very poor prognosis due to the lack of efficient treatments. As observed in several other tumors, the effectiveness of treatments is mainly hampered by the presence of a highly tumorigenic sub-population of cancer cells called cancer stem cells (CSCs). Indeed, CSCs are resistant to chemotherapy and radiotherapy and can regenerate the tumor bulk. Hence, innovative drugs that are efficient against both bulk tumor cells and CSCs would likely improve cancer treatment. In this study, we demonstrated that GNS561, a new autophagy inhibitor that induces lysosomal cell death, showed significant activity against not only the whole tumor population but also a sub-population displaying CSC features (high ALDH activity and tumorsphere formation ability) in HCC and in liver mCRC cell lines. These results were confirmed in vivo in HCC from a DEN-induced cirrhotic rat model in which GNS561 decreased tumor growth and reduced the frequency of CSCs (CD90⁺CD45^-). Thus, GNS561 offers great promise for cancer therapy by exterminating both the tumor bulk and the CSC sub-population. Accordingly, a global phase 1b clinical trial in liver cancers was recently completed.

Keywords: GNS561; cancer stem cell; colorectal cancer; liver cancer; lysosome; therapy.

Figure 1

GNS561 is efficient against subpopulation displaying CSC features. (A) Box and whisker representation (min to max) of the percentage of ALDH^bright cells after 72 h of treatment with GNS561 in three liver mCRC cell lines with the indicated concentrations. For comparison with the control, one-way ANOVA with Dunnett's post hoc analysis was performed. *, P < 0.05. Antitumor activity of GNS561 on whole tumor (circle) or CSC-enriched populations (square) in Hep3B (B) and Huh7 (C) HCC cell lines after 48 or 72 h of treatment with GNS561. The curves represent the mean of two independent experiments in triplicate.

Figure 2

GNS561 alters the self-renewal of liver mCRC and HCC cell lines. (A) Tumorsphere forming efficiency of three liver mCRC (CPP19, CPP30 and CPP36) and one HCC (Hep3B) cell lines treated with the indicated GNS561 concentrations. Scale bars represent 50 µm. (B) Number of spheres > 50 µm. For comparison with the control, statistical significance was determined using one-way ANOVA and Dunnett's post hoc test. *, P < 0.05.

Figure 3

GNS561 decreases CSC frequency in vivo. Box and whisker representation (min to max) of the percentage of CSCs in liver tumor (A) and blood (B) samples in a diethylnitrosamine-induced cirrhotic rat model of HCC. Rats received vehicle (control), sorafenib at 10 mg/kg or GNS561 at 15 mg/kg. For comparison with the control non-treated group, the non-parametric Kruskal-Wallis test was performed. **, P < 0.01.