Protein kinase CK2 has emerged as an attractive therapeutic target in acute myeloid leukemia (AML), an advent that becomes particularly relevant since the treatment of this hematological neoplasia remains challenging. Here we explored for the first time the effect of the clinical-grade peptide-based CK2 inhibitor CIGB-300 on AML cells proliferation and viability. CIGB-300 internalization and subcellular distribution were also studied, and the role of B23/nucleophosmin 1 (NPM1), a major target for the peptide in solid tumors, was addressed by knock-down in model cell lines. Finally, pull-down experiments and phosphoproteomic analysis were performed to study CIGB-interacting proteins and identify the array of CK2 substrates differentially modulated after treatment with the peptide. Importantly, CIGB-300 elicited a potent anti-proliferative and proapoptotic effect in AML cells, with more than 80% of peptide transduced cells within three minutes. Unlike solid tumor cells, NPM1 did not appear to be a major target for CIGB-300 in AML cells. However, in vivo pull-down experiments and phosphoproteomic analysis evidenced that CIGB-300 targeted the CK2α catalytic subunit, different ribosomal proteins, and inhibited the phosphorylation of a common CK2 substrates array among both AML backgrounds. Remarkably, our results not only provide cellular and molecular insights unveiling the complexity of the CIGB-300 anti-leukemic effect in AML cells but also reinforce the rationale behind the pharmacologic blockade of protein kinase CK2 for AML-targeted therapy.

The instrumental role of CK2 in the SARS-CoV-2 infection has pointed out this protein kinase as promising therapeutic target in COVID-19. Anti-SARS-CoV-2 activity has been reported by CK2 inhibitors in vitro ; however, no anti-CK2 clinical approach has been investigated in COVID-19. This trial aimed to explore the safety and putative clinical benefit of CIGB-325, an anti-CK2 peptide previously assessed in cancer patients. A monocentric, controlled, and therapeutic exploratory trial of intravenous CIGB-325 in adults hospitalized with COVID-19 was performed. Twenty patients were randomly assigned to receive CIGB-325 (2.5 mg/kg/day during 5-consecutive days) plus standard-of-care (10 patients) or standard-of-care alone (10 patients). Adverse events were classified by the WHO Adverse Reaction Terminology. Parametric and nonparametric statistical analyses were performed according to the type of variable. Considering the small sample size, differences between groups were estimated by Bayesian analysis. CIGB-325 induced transient mild and/or moderate adverse events such as pruritus, flushing, and rash in some patients. Both therapeutic regimens were similar with respect to SARS-CoV-2 clearance in nasopharynx swabs over time. However, CIGB-325 significantly reduced the median number of pulmonary lesions (9.5 to 5.5, p = 0.042) at day 7 and the proportion of patients with such an effect was also higher according to Bayesian analysis (pDif > 0; 0.951). Also, CIGB-325 significantly reduced the CPK ( p = 0.007) and LDH ( p = 0.028) plasma levels at day 7. Our preliminary findings suggest that this anti-CK2 clinical approach could be combined with standard-of-care in COVID-19 in larger studies.

Protein kinase CK2 is a highly pleiotropic and ubiquitously expressed Ser/Thr kinase with instrumental roles in normal and pathological states, including neoplastic phenotype in solid tumor and hematological malignancies. In line with previous reports, CK2 has been suggested as an attractive prognostic marker and molecular target in acute myeloid leukemia (AML), a blood malignant disorder that remains as an unmet medical need. Accordingly, this work investigates the complex landscape of molecular and cellular perturbations supporting the antileukemic effect exerted by CK2 inhibition in AML cells. To identify and functionally characterize the proteomic profile differentially modulated by the CK2 peptide-based inhibitor CIGB-300, we carried out LC-MS/MS and bioinformatic analysis in human cell lines representing two differentiation stages and major AML subtypes. Using this approach, 109 and 129 proteins were identified as significantly modulated in HL-60 and OCI-AML3 cells, respectively. In both proteomic profiles, proteins related to apoptotic cell death, cell cycle progression, and transcriptional/translational processes appeared represented, in agreement with previous results showing the impact of CIGB-300 in AML cell proliferation and viability. Of note, a group of proteins involved in intracellular redox homeostasis was specifically identified in HL-60 cell-regulated proteome, and flow cytometric analysis also confirmed a differential effect of CIGB-300 over reactive oxygen species (ROS) production in AML cells. Thus, oxidative stress might play a relevant role on CIGB-300-induced apoptosis in HL-60 but not in OCI-AML3 cells. Importantly, these findings provide first-hand insights concerning the CIGB-300 antileukemic effect and draw attention to the existence of both common and tailored response patterns triggered by CK2 inhibition in different AML backgrounds, a phenomenon of particular relevance with regard to the pharmacologic blockade of CK2 and personalized medicine.