Interplay Between Mitophagy and Apoptosis Defines a Cell Fate Upon Co-treatment of Breast Cancer Cells With a Recombinant Fragment of Human κ-Casein and Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand
Authors: Tanja Vidaković-Koch
Inna N Lavrik
Lado Otrin
Olga Koval
Fabian Wohlfromm
Max Richter
Vladimir Richter
Kamil Seyrek
Elena Kuligina
Journal: Frontiers in Cell and Developmental Biology (2021)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: RL2; TOM70; TRAIL; apoptosis; lactaptin
Affiliations: Translational Inflammation Research, Medical Faculty, Otto von Guericke University, Magdeburg, Germany., Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany., Department of Biotechnology, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences (SB RAS), Novosibirsk, Russia.

Abstract:  A recombinant fragment of human κ-Casein, termed RL2, induces cell death of breast cancer cells; however, molecular mechanisms of RL2-mediated cell death have remained largely unknown. In the current study, we have decoded the molecular mechanism of the RL2-mediated cell death and found that RL2 acts via the induction of mitophagy. This was monitored by the loss of adenosine triphosphate production, LC3B-II generation, and upregulation of BNIP3 and BNIP3L/NIX, as well as phosphatase and tensin homolog-induced kinase 1. Moreover, we have analyzed the cross talk of this pathway with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis upon combinatorial treatment with RL2 and TRAIL. Strikingly, we found two opposite effects of this co-treatment. RL2 had inhibitory effects on TRAIL-induced cell death upon short-term co-stimulation. In particular, RL2 treatment blocked TRAIL-mediated caspase activation, cell viability loss, and apoptosis, which was mediated via the downregulation of the core proapoptotic regulators. Contrary to short-term co-treatment, upon long-term co-stimulation, RL2 sensitized the cells toward TRAIL-induced cell death; the latter observation provides the basis for the development of therapeutic approaches in breast cancer cells. Collectively, our findings have important implications for cancer therapy and reveal the molecular switches of the cross talk between RL2-induced mitophagy and TRAIL-mediated apoptosis. 

Retracted: No

PubPeer comments:
 Could the author please describe how the statistical analysis has been performed? Have the authors checked for prerequisites to apply parametric statistical tests such as Students t-test or ANOVA? In particular: In Fig. 1E: The error bar of the control seems to be not present, since all replicates seem to be normalized to the control. However, if that is true, the prerequisite for normally distributed data is not fulfilled for applying a parametric t-test. In Fig. 3A,B: Has data been checked for normal distribution and homogeneity of the variances? Why did the author perform an ANOVA without post hoc tests and instead performed a t-test? In Fig. 6A,B: Why did the author perform a paired t-test? The data seems not to be sufficient to perform this test. The author should consider re-perform the statistical analysis after checking the data for applicability of either non-parametric or parametric tests. I highly recommend improving the statistical analysis since the conclusions the author has drawn from these tests might be incorrect. Thank you ,