Assessment of SIRT1-SIRT7 and TP53 Genes Expression in Patients with Acute Myeloid Leukemia

BACKGROUND

Sirtuins ( SIRTs) are a family of histone deacetylases with 7 representatives ( SIRT1-7), which affect cell survival and metabolism. They influence gene expression by interacting with histones and transcription factors, or directly modulate pathways associated with cell survival, for instance by downregulating p53, thus potentially contributing to cancerogenesis. On the other hand, SIRTs may function as tumor suppressors depending on cellular context. While the role of SIRTs expression is widely discussed in solid neoplasms, they have not been comprehensively evaluated in acute myeloid leukemia (AML) yet.

AIMS

To investigate the prognostic importance of initial SIRTs expression in AML patients (pts) and its relationship with the expression of TP53.

METHODS

The study included 40 newly diagnosed AML pts (19 women, 21 men), with a mean age of 62 years (range: 26-87). Low-, intermediate- or high-risk AML according to European LeukemiaNet (ELN) 2022 stratification was diagnosed in 6 (15%), 13 (32.5%), and 21 (52.5%) of pts respectively. The expression of SIRT1-7 and TP53 was examined by real-time PCR using the TaqMan chemistry and the QuantStudio7 thermal cycler (Applied Biosystems-Thermo Fisher Scientific). The reference genes were selected using GeNorm and NormFinder. The mRNA levels were normalized by the formula ∆Ct = Ct(reference) - Ct(particular mRNA). Group comparisons were performed using Welch's t-test. Pearson correlation evaluated the relationship between individual gene expression. Overall survival (OS) was assessed by the Kaplan-Meier method with the log-rank test. Cox proportional hazard regression of clinical factors and genes expression for predicting OS was performed.

RESULTS

FLT3 ITDor TKD mutations were present in 10 (25%) of pts, NPM1 in 9 (23%), and IDH1 or IDH2 in 6 (15%). 14 (35%) of the study group were diagnosed with AML with myelodysplasia-related cytogenetic abnormalities, AML progressed from myelodysplastic syndrome, or therapy-related AML (secondary AML, sAML). Standard induction chemotherapy was given in 42.5% of pts, 25% were treated with azacitidine+venetoclax (Aza+Ven), and other non-intensive therapies were administered to 32.5%.

SIRT4 expression was detected in 92.5% of pts, while expression of the other genes studied was found in all pts. There were no differences in SIRT 1-7 expression in terms of ELN2022 risk stratification. However, TP53 was downregulated in the high-risk group (fold change - FC=0.6, p=0.004). In pts with FLT3 mutation, SIRT7 was downregulated (FC=0.8, p=0.07), while in both NPM1 and IDH1/2 mutated groups, we showed upregulation of TP53 (FC=1.5, p=0.03, and FC=1.5, p=0.001, respectively). Moreover, in older pts (>60 years old) TP53 was downregulated (FC=0.7, p=0.02). In sAML group SIRT3 and TP53 were downregulated (FC=0.7, p=0.08, and FC=0.7, p=0.05, respectively).

Significant positive correlations were shown between the expression of individual SIRTs, and it was most strongly expressed between SIRT2 and SIRT6 (r=0.85, p=0.00), SIRT2 and SIRT7 (r=0.81, p=0.00), and SIRT6 and SIRT7 (r=0.76, p=0.00).

The median follow-up was 6.7 months (95% CI: 4.5-9.1). The median OS in the study cohort was not reached. There were no significant differences in treatment response or OS considering each SIRT expression level. However, pts with higher TP53 expression (> median) presented longer OS (median OS not reached vs 5.8 months (95% CI:1.3-5.8, p=0.05) [Figure 1].

In the multivariate Cox proportional hazard model for OS, upregulation of TP53 (HR 0.25, 95%CI: 0.08-0.60, p=0.01), age (HR 1.06, 95%CI: 1.01-1.12, p=0.03), as well as initial albumins (HR 0.01, 95%CI: 0.00-0.07, p=0.01), and LDH levels (HR 1.00, 95%CI: 1.00-1.01, p=0.01) were factors influencing the outcome [Table 1].

CONCLUSIONS

The expression of SIRTs in AML presented no evident impact on treatment outcome. However, our study revealed that higher TP53 expression was associated with longer OS. Moreover, TP53 upregulation was found in pts with certain mutational profiles, while downregulation in the elderly and those with sAML. The analysis indicates that SIRTs expression may also vary markedly depending on the clinical and molecular context. The expression of individual SIRTs is closely correlated with each other, but these preliminary results did not show their direct relationship with TP53 expression. Further studies on SIRTs are needed to assess their impact on AML.