The role of DNA damage and repair in decitabine-mediated apoptosis in multiple myeloma

Abstract

DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) are under investigation for the treatment of cancer, including the plasma cell malignancy multiple myeloma (MM). Evidence exists that DNA damage and repair contribute to the cytotoxicity mediated by the DNMTi decitabine. Here, we investigated the DNA damage response (DDR) induced by decitabine in MM using 4 human MM cell lines and the murine 5T33MM model. In addition, we explored how the HDACi JNJ-26481585 affects this DDR. Decitabine induced DNA damage (gamma-H2AX foci formation), followed by a G0/G1- or G2/M-phase arrest and caspase-mediated apoptosis. JNJ-26481585 enhanced the anti-MM effect of decitabine both in vitro and in vivo. As JNJ-26481585 did not enhance decitabine-mediated gamma-H2AX foci formation, we investigated the DNA repair response towards decitabine and/or JNJ-26481585. Decitabine augmented RAD51 foci formation (marker for homologous recombination (HR)) and/or 53BP1 foci formation (marker for non-homologous end joining (NHEJ)). Interestingly, JNJ-26481585 negatively affected basal or decitabine-induced RAD51 foci formation. Finally, B02 (RAD51 inhibitor) enhanced decitabine-mediated apoptosis. Together, we report that decitabine-induced DNA damage stimulates HR and/or NHEJ. JNJ-26481585 negatively affects RAD51 foci formation, thereby providing an additional explanation for the combinatory effect between decitabine and JNJ-26481585.

Optimizing drug combinations against multiple myeloma using a quadratic phenotypic optimization platform (QPOP)

“…Targeting DNA methylation in MM Dec works by inhibiting DNMTs and promoting DNA hypomethylation (35). Previous studies have found that relapsed MM cases had much higher amounts of global DNA methylation compared to monoclonal gammopathy of undetermined significance and newly diagnosed MM cases (36).…”

Epigenetic‐Based Mechanisms of Osteoblast Suppression in Multiple Myeloma Bone Disease

“…DNA methyltransferase inhibitors (DNMTi), eg, azacitidine and decitabine, have been reported to have anti‐MM effects by inducing cell cycle arrest and impacting the growth of resistant MM cell lines and primary patient‐derived MM cells . Maes and colleagues used a combination of the DNMTi decitabine and the HDACi quisinostat in the in vivo syngeneic 5T33MM mouse model to test the antitumor activity of these epigenetic modulating agents.…”

Exposure to hypomethylating agent 5-aza-2’-deoxycytidine (decitabine) causes rapid, severe DNA damage, telomere elongation and mitotic dysfunction in human WIL2-NS cells

“…These observations are consistent with previous work on the effects of 5azadC showing that only a few hours exposure caused single and double strand breaks, together with decondensation of genetically inactive chromatin (25). 5azadC is a robust inducer of γ-H2AX, an early marker of DSB, activation of DNA repair proteins, and DNA fragmentation (7, 26, 27). Interestingly, the reduction of DNMT1 caused by 5azadC also impairs the cell’s capacity to respond to damage, as DNMT1 is required to co-localise with γ-H2AX at sites of damage.…”

“…Previous studies to determine the degree of cytotoxicity and DNA damage caused by 5azadC have measured the extent to which H2AX, a key ‘first responder’ in a DNA breakage damage response, is phosphorylated to generate γH2AX (7). While informative, this method is specific to DNA breaks and does not capture the different forms of chromosomal instability induced by hypomethylation and DNA replication stress.…”