According to research published in Antioxidants, differing oxidative stress response capabilities in patients with myelofibrosis (MF) may be a mechanism underlying disease progression.
The researchers of the MYeloid NEoplasms Research Venture, AIRC (Mynerva) studied the role of driver mutations in calreticulin (CALR) and Janus kinase 2 (JAK2) in oxidative stress by assessing reactive oxygen species (ROS) levels in CD34+ hematopoietic stem/progenitor cells of patients with MF.
Participants were recruited from 4 Italian centers. The researcher purified CD34+ cells from peripheral blood samples of 17 healthy donors (HDs) and 34 patients with a diagnosis of primary (n=18) and secondary (n=16) MF (according to 2016 World Health Organization criteria). Among patients with MF, 20 harbored JAK2 mutations (JAK2V617F or JAK2 exon 12 mutations) and 14 harbored CALR mutations (type 1/type 1-like or type 2/type 2-like). The team also collected plasma samples from 129 patients with MF (JAK2 mutations, n=86; CALR mutations, n=43).
The researchers induced oxidative stress by treating the CD34+ cells with the powerful oxidant, Melittin. They evaluated intracellular ROS levels, activity of superoxide dismutase (SOD, a biomarker for cellular response to oxidative stress), total antioxidant capacity, and levels of 8-hydroxy-20-deoxy-guanosine (8-OHdG, a biomarker of oxidative stress-mediated DNA damage), and lactate dehydrogenase (LDH).
The researchers demonstrated that Melittin induces significantly greater ROS accumulation in cells from patients with MF (either CALR-mutated or JAK2-mutated) than in cells from HDs (P <.0001 for both comparisons). ROS accumulation was significantly greater in cells from patients with CALR-mutated MF than in those from patients with JAK2-mutated MF (P <.0001). SOD antioxidant activity was significantly lower in cells from patients with MF compared with those from HDs both before (P <.01) and after Melittin treatment (P <.05), and the level was lower before treatment (P <.05) and trended lower after treatment among cells from patients with CALR-mutated MF than those from patients with JAK2-mutated MF.
Further analysis demonstrated that the increased ROS accumulation led to increased oxidative DNA damage in cells from patients with MF than those from HDs. Following Melittin treatment, cells from HDs were able to recover, while those from patients with JAK2-mutated MF (P <.01) and CALR-mutated MF (P <.05) had significantly higher 8-OHdG levels relative to cells from HDs.
In plasma samples from patients with MF, the researchers found that high levels of total antioxidant capacity correlated with detrimental clinical features, including high levels of LDH and circulating CD34+ cells (P <.05 for both). Among patients with MF, those with high levels of total antioxidant capacity had poorer overall survival (OS) than those with low levels (hazard ratio [HR], 2.304; 95% confidence interval [CI], 1.283–4.139; P =.0061). Patients with mutated CALR and the lowest levels of total antioxidant capacity activity were associated with the highest OS, while patients with mutated JAK2 and the highest levels of total antioxidant capacity activity were associated with the lowest OS (P =.0102).
Multivariate analyses revealed that high total antioxidant capacity classification was an independent prognostic factor allowing the identification of patients with MF (CALR-mutated MF and JAK2-mutated MF) with inferior OS in both the lowest (low and intermediated-1; HR, 2.155; 95% CI, 1.065–22.40; P =.0235) and highest (high and intermediated-2; HR, 2.155; 95% CI, 1.065–4.359; P =.0327) Dynamic International Prognostic Scoring System categories.
The researchers speculated, “the high increase in oxidative stress in [patients with mutated CALR] could be involved in the activation of protective mechanisms which ultimately promote cell death, while in patients with the [mutated JAK2], the slight increase in oxidative stress can be a mechanism that determines the persistence of cells with damaged DNA in which the accumulation of mutations promotes the disease progression.”
They suggested the assessment of response to oxidative damage, using the plasma assay presented in the study, could provide an additional variable to better define the prognosis of patients with MF.
Genovese E, Mirabile M, Rontauroli S, et al. The response to oxidative damage correlates with driver mutations and clinical outcome in patients with myelofibrosis. Antioxidants (Basel). 2022;11(1):113. doi:10.3390/antiox11010113