Annexin A6 modulates apoptotic priming and BCL-2 dependency in acute lymphoblastic leukaemia

Abstract Annexin A6 (ANXA6) is a Ca²⁺-dependent membrane-binding protein involved in cellular signalling and membrane dynamics, yet its role in apoptosis in haematological malignancies remains poorly defined. Here, we identify ANXA6 as a regulator of apoptotic priming and BCL-2 family protein balance. Using BH3 profiling, we show that ANXA6 depletion reduces apoptotic priming in HeLa cells, indicating increased resistance to mitochondrial apoptosis. This phenotype is associated with increased BCL-2 expression and reduced BAK levels and occurs independently of changes in mitochondrial mass or morphology. Mechanistically, ANXA6-deficient HeLa cells display enhanced activation of pro-survival signalling pathways, such as AKT, which are known to modulate the BCL-2 family of proteins, supporting a role for ANXA6 as a negative regulator of pro-survival signalling. In an acute lymphoblastic leukaemia (ALL) model, ANXA6 expression inversely correlates with BCL-2 and positively with pro-apoptotic proteins BAK and BAD expression across cell lines and patient samples. Functionally, ANXA6 depletion reduces apoptotic priming in selected ALL cell models and increases sensitivity to BCL-2 and BCL-xL inhibition. Together, these findings position ANXA6 as a modulator of apoptotic threshold and a potential determinant of BCL-2 dependency and response to BH3 mimetics in ALL.