DNMT3a plays a role in switches between doxorubicin‐induced senescence and apoptosis of colorectal cancer cells

Abstract

The DNA-damaging drug doxorubicin (Dox) induces cell senescence at concentrations significantly lower than those required for induction of apoptosis. At low Dox concentrations, tumor suppressor p53 is activated, which enhances the expression of p21 Waf1/Cip1 (p21). At high concentrations, Dox activates p53 leading to apoptosis without enhancing p21 expression. The underlying mechanisms and factors that govern the differential effects of Dox in inducing senescence and apoptosis are unclear. Here, we report that the DNA methyltransferase (DNMT) DNMT3a was upregulated by Dox especially at concentrations that induced apoptosis in HCT116 colorectal cancer cells, and this process was regulated by p53. Meanwhile, p21 expression was significantly upregulated at senescence-inducing concentrations and kept low on treatment with apoptosis-inducing concentrations of Dox. The differential expression of DNMT3a and p21 in response to Dox suggests that DNMT3a may be a key factor in switches between Dox-induced senescence and apoptosis. Moreover, when DNMT3a was silenced, treatment of HCT116 cells with apoptosis-inducing concentration of Dox increased the percentage of cells undergoing senescence, accompanied by upregulation of p21. Contrarily, senescence-inducing concentration of Dox promoted apoptosis rate, and p21 expression was repressed. Surprisingly, no changes in DNA methylation status at p21 promoter were detected at either ranges of Dox, although DNMT3a and HDAC1 were recruited to p21 promoter at apoptosis-inducing Dox concentration, where they were present in the same complex. Overall, these data demonstrate that DNMT3a impacts the expression of p21 and plays a role in determining the Dox-induced senescence and apoptosis in HCT116 cells.When proliferating cells encounter a genotoxic stress, induced by, for instance the chemotherapeutic drugs, the cell cycle must be arrested immediately to ensure DNA integrity. This event is usually followed by a decision of whether the cells remain arrested in the cell cycle for initiating DNA repair, or execute the apoptotic program. The anthracycline antibiotic agent doxorubicin (Dox) has been used as a chemotherapeutic drug for >40 years for the treatment of a variety of malignancies. 1 Despite the extensive and long-standing clinical utilization of Dox, the mechanism of its action remains uncertain and has long been an issue of controversy. Dox can induce at least 3 distinct types of cell death, i.e., senescence, apoptosis, and necrosis, in a concentration-dependent manner. Specific molecular markers such as p21, activated caspase-3 and activated Akt, were associated with these death modes. 2 At low concentrations, the predominant effect of Dox is to initiate senescence, whereas at high Dox concentrations, tumor cells may undergo cell death.The p53 tumor suppressor is a transcription factor that is involved in the cellular DNA damage response, causing either G1 arrest or apoptosis. 3 p53 plays an important role in Doxinduced senescence and apoptosis. At low concentrations of Dox, p...

DNMT3A Mutational Status Affects the Results of Dose-Escalated Induction Therapy in Acute Myelogenous Leukemia

“…Alternatively, DNMT3A mRNA and protein have been shown to be upregulated in response to increasing doses of doxorubicin in human colorectal cell lines, and silencing of DNMT3A increased the percentage of senescent cells in response to treatment with doxorubicin. 23 DNMT3A mutations, particularly the single amino acid mutation, R882, has been shown to result in decreased function of the methyltransferase enzyme in in vitro studies. 15 It is plausible that the decreased function of DNMT3A allows for a better response to high dose anthracycline chemotherapy.…”

Do AML patients with DNMT3A exon 23 mutations benefit from idarubicin as compared to daunorubicin? A single center experience

“…However, it has been recently shown that DNMT3A could play a role in anthracyclines-induced apoptosis of colorectal cancer cells. Indeed, the expression of DNMT3A is upregulated at apoptosis-inducing concentrations of doxorubicin and involved in p21 repression thereby blocking senescence [27]. Whether this program is induced by idarubicin but not daunorubicin in DNMT3A mutated/haploinsufficient cells remains to be determined.…”

Senescent cells: an emerging target for diseases of ageing

“…The disruption of p53-binding domain cooperativity through the E177R mutation similarly ablates pro- apoptotic but not pro-senescent p53 target gene expression 79 . p21 itself can block apoptosis 80,81 , and — intriguingly — may inhibit caspase 3 (CASP3) activity directly 82 . Indeed, apoptotic cells actively silence p21 expression via p53-dependent DNA (cytosine-5)- methyltransferase 3A (DNMT3A) activity 80 .…”

“…p21 itself can block apoptosis 80,81 , and — intriguingly — may inhibit caspase 3 (CASP3) activity directly 82 . Indeed, apoptotic cells actively silence p21 expression via p53-dependent DNA (cytosine-5)- methyltransferase 3A (DNMT3A) activity 80 .…”