The BH3 mimetic (\xb1) gossypol induces ROS-independent apoptosis and mitochondrial dysfunction in human A375 melanoma cells in vitro

Lisa Haasler,Claudia Von Montfort,Wilhelm Stahl,Peter Brenneisen,Peter Graf,Thanos Tsigaras,Arun Kumar Kondadi

doi:10.1007/s00204-021-02987-4

Lisa Haasler, Claudia Von Montfort + Show 5 more

Open Access

https://doi.org/10.1007/s00204-021-02987-4

Copy DOI

Abstract

A major challenge in current cancer therapy is still the treatment of metastatic melanomas of the skin. BH3 mimetics represent a novel group of substances inducing apoptosis. In this study, we investigated the cytotoxic effect of (±) gossypol (GP), a natural compound from cotton seed, on A375 melanoma cells and the underlying biochemical mechanisms. To prevent undesired side effects due to toxicity on normal (healthy) cells, concentrations only toxic for tumor cells have been elaborated. Viability assays were performed to determine the cytotoxicity of GP in A375 melanoma and normal (healthy) cells. For the majority of experiments, a concentration of 2.5 µM GP was used resulting in a ROS-independent but caspase-dependent cell death of A375 melanoma cells. At this level, GP was non-toxic for normal human epidermal melanocytes. GP has a very short half-life, however, it was demonstrated that only the “parent” compound and not decomposition products are responsible for the cytotoxic effect in A375 melanoma cells. GP significantly decreased mitochondrial membrane potential accompanied by a Drp1-dependent loss of mitochondrial integrity (fragmentation) in tumor cells. Taken together, GP induced a ROS-independent intrinsic apoptosis leading to the conclusion that within a specific concentration range, GP may work as effective anticancer drug without harmful side effects.

Highlights

Malignant melanoma is the most aggressive type of skin cancer due to its high potential to metastasize resulting in poor survival (Janostiak et al 2019; Miller and Mihm 2006; Zbytek et al 2008)
Since the MTT assay provides information on metabolic activity and MTT itself is toxic to cells over time resulting in falsepositive results, we used the Sulforhodamine B (SRB) assay to verify the effect of GP on the cells (Riss et al 2004)
The results from both assays and the IC50 values of GP after 96 h (Supplemental Fig. 1b, c), indicate that GP exerts a selective cytotoxicity on A375 melanoma cells

Summary

Introduction

Malignant melanoma is the most aggressive type of skin cancer due to its high potential to metastasize resulting in poor survival (Janostiak et al 2019; Miller and Mihm 2006; Zbytek et al 2008). Increasing resistance requires the development of new approaches to effectively treat these types of cancer. One focus is on stimulation of the programmed cell death, apoptosis (Mohammad et al 2015), that is often inhibited in cancer cells (Hanahan and Weinberg 2011). Key regulators in this pathway are members of the Bcl-2 protein family which is classified into anti- (e.g. Bcl-2, Bcl-xL, and MCL-1) and proapoptotic (e.g. Bax, Bak, Bim, and Bad) proteins, related to function and number of homology domains (BH1–4) (Cory and Adams 2002; Opydo-Chanek et al 2017; Vogler 2014). Several tumor cells including melanoma cells (Lee et al 2019) show an overexpression of

Methods

Results

Conclusion