Abstract
Background and PurposeMany cancer cells depend on anti‐apoptotic B‐cell lymphoma 2 (Bcl‐2) proteins for their survival. Bcl‐2 antagonism through Bcl‐2 homology 3 (BH3) mimetics has emerged as a novel anti‐cancer therapy. ABT‐199 (Venetoclax), a recently developed BH3 mimetic that selectively inhibits Bcl‐2, was introduced into the clinic for treatment of relapsed chronic lymphocytic leukaemia. Early generations of Bcl‐2 inhibitors evoked sustained Ca2+ responses in pancreatic acinar cells (PACs) inducing cell death. Therefore, BH3 mimetics could potentially be toxic for the pancreas when used to treat cancer. Although ABT‐199 was shown to kill Bcl‐2‐dependent cancer cells without affecting intracellular Ca2+ signalling, its effects on PACs have not yet been determined. Hence, it is essential and timely to assess whether this recently approved anti‐leukaemic drug might potentially have pancreatotoxic effects.Experimental ApproachSingle‐cell Ca2+ measurements and cell death analysis were performed on isolated mouse PACs.Key ResultsInhibition of Bcl‐2 via ABT‐199 did not elicit intracellular Ca2+ signalling on its own or potentiate Ca2+ signalling induced by physiological/pathophysiological stimuli in PACs. Although ABT‐199 did not affect cell death in PACs, under conditions that killed ABT‐199‐sensitive cancer cells, cytosolic Ca2+ extrusion was slightly enhanced in the presence of ABT‐199. In contrast, inhibition of Bcl‐xL potentiated pathophysiological Ca2+ responses in PACs, without exacerbating cell death.Conclusion and ImplicationsOur results demonstrate that apart from having a modest effect on cytosolic Ca2+ extrusion, ABT‐199 does not substantially alter intracellular Ca2+ homeostasis in normal PACs and should be safe for the pancreas during cancer treatment.Linked ArticlesThis article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc
Highlights
Impaired regulation of apoptosis is crucial to the process of carcinogenesis enabling cancer cells to evade cell death signals triggered by oncogenic stress and acquiring metastatic properties by accumulation of secondary genetic mutations (Adams and Cory, 2007; Hanahan and Weinberg, 2011)
B-cell lymphoma 2 (Bcl-2)-dependent cancers are often ‘primed for death’, a term used to describe the necessity of expressing high levels of the anti-apoptotic Bcl-2 proteins in order to actively sequester and inhibit the pro-apoptotic family members, Bcl-2-associated X protein (Bax) and the activator Bcl-2 homology 3 (BH3)-only protein Bcl-2-like protein 11 (Bim) (Akl et al, 2014)
In order to compare the effects of acute inhibition of different Bcl-2-protein family members on Ca2+ homeostasis in pancreatic acinar cell (PAC), several BH3 mimetics were tested (Figure 1)
Summary
Impaired regulation of apoptosis is crucial to the process of carcinogenesis enabling cancer cells to evade cell death signals triggered by oncogenic stress and acquiring metastatic properties by accumulation of secondary genetic mutations (Adams and Cory, 2007; Hanahan and Weinberg, 2011) In cancer cells, this is achieved by altered expression levels of either the pro- or anti-apoptotic B-cell lymphoma 2 (Bcl-2) family members, predominantly located at the mitochondrial membranes (Davids and Letai, 2012). Pharmacological disruption of the interaction between the anti- and pro-apoptotic Bcl-2 family members has the potential to activate Bax/Bak, and restore the programmed cell death (Wang et al, 2000; Chipuk et al, 2008) This spurred the development of Bcl-2 antagonists that target the hydrophobic cleft of the anti-apoptotic Bcl-2 proteins displacing Bax/Bak and Bim from Bcl-2. It is essential and timely to assess whether this recently approved anti-leukaemic drug might potentially have pancreatotoxic effects
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