Type 2 Diabetes Leads to the Senescence of the Bone Marrow Microenvironment, and the Increase in DNA Damage Repair Function of AML Cells Mediates Anthracycline Resistance through Sasp

The incidence of Acute Myeloid Leukemia (AML) is positively correlated with age. According to statistics, the median age of onset of AML is 68~70 years old, which means that more than 50% of AML cases occur in elderly patients aged 60 years and above. Type 2 Diabetes mellitus (T2DM), a group of metabolic disorders characterized by chronic hyperglycemia, has reached epidemic proportions globally, affecting millions of individuals, especially in the elderly. Both type 2 diabetes and AML are age-related diseases, so AML patients with type 2 diabetes are common in clinical practice, and in clinical experience, this subset of patients tends to have a worse prognosis.

Among AML patients who received standard induction chemotherapy regimens at our center, after excluding confounding factors such as genetic mutations and chromosomal abnormalities, those who had coexisting Type 2 Diabetes Mellitus exhibited a lower remission rate compared to their counterparts without diabetes. Specifically, the complete remission (CR) rate following two courses of induction chemotherapy was found to be 88.3% among patients with T2DM, whereas the CR rate among patients without diabetes stood at 91.4%.

We hypothesize that changes in the bone marrow microenvironment in patients with diabetes mellitus may have an impact on the chemotherapy sensitivity of leukemia cells. To test this hypothesis, we first collected bone marrow from streptozotocin-induced type 2 diabetic mice and bone marrow from control mice and then co-cultured them with AML cell lines. The sensitivity of AML cells to doxorubicin and cytarabine was detected after 5 days of co-culture. It was found that co-culture with bone marrow of diabetic mice reduced the sensitivity of AML cells to doxorubicin. Transcriptome sequencing was used to compare the gene expression of bone marrow of two groups and AML cells under different co-culture conditions. We found that the different genes of bone marrow were enriched in the senescence pathway, while the expression of genes related to DNA damage repair was increased in AML cells co-cultured with the bone marrow of diabetic mice.

We validated the bone marrow senescence induced by type 2 diabetes mellitus with different experimental methods. The results of western blot experiments showed that compared with the control group of mice, the expression of p21 protein in the bone marrow of T2DM mice was increased and the expression of LaminB1 protein decreased. Frozen sections of the femur were stained and increased β-galactosidase activity was found. Cytokines in the supernatant of bone marrow cell culture were detected by liquid microarray, and the result showed that senescence-associated secretory phenotype (SASP), such as IL-1β, IL-6, IL-10, CXCL-1, and INF-γ, were significantly increased in the bone marrow supernatant of diabetic mice.

In order to verify whether it is SASP that enhance the DNA damage repair function of AML cells, AML cells were pretreated with the cytokines mentioned above for 5 days before doxorubicin was applied to AML cells, and finally the expression of γ-H2AX was detected to show the degree of DNA damage. The results showed that doxorubicin treatment increased the expression of γ-H2AX, which means it induced DNA damage in AML cells, while SASP pretreatment was the same as diabetic bone marrow co-culture, which could reduce the increase in γ-H2AX.

Doxorubicin mediates cellular DNA damage through DNA double-strand breaks(DSB). Ataxia telangiectasia-mutated(ATM) protein is an important regulator in repair of DSB. We found that ATM protein expression was increased in AML cells in the SASP pretreatment group and the diabetic bone marrow co-culture group, along with an increase in phosphorylation of the JAK-STAT5 signaling pathway. It has been reported that STAT5 can regulate the expression of ATM protein through peroxisome proliferator-activated receptor γ (PPARγ). We speculate that this may be the mechanism by which SASP upregulates ATM protein expression in AML and increases DNA damage repair, which is being demonstrated through further experiments. If this hypothesis is confirmed, efficacy of chemotherapy in AML patients with type 2 diabetes could be enhanced by blocking this pathway.

In conclusion, our study will elucidate the reasons for the poor prognosis of AML patients with type 2 diabetes mellitus and try to find ways to improve patient outcomes from its mechanisms.