Phenotypic Evaluation of Natural Killer Cells and T Lymphocytes During the Response and After Discontinuation of Tyrosine Kinase Inhibitor Treatment in Patients with Chronic Myeloid Leukemia

• Grant number: 23/17821-9
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: July 01, 2024
• End date: September 30, 2025
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Lorena Lôbo de Figueiredo Pontes
• Grantee: Larissa Sarri Binelli
• Host Institution: Hemocentro de Ribeirão Preto. Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da USP (HCMRP). Secretaria da Saúde (São Paulo - Estado). Ribeirão Preto , SP, Brazil
• Associated research grant: 21/06841-3 - Molecular and phenotypical mechanisms driving immune evasion in myeloid malignancies, AP.JP2

Abstract

In Chronic Myeloid Leukemia (CML) patients achieving sustained deep molecular response (DMR) with tyrosine kinase inhibitor (TKI) may discontinue treatment. Treatment-free remission (TFR) occurs in a minority without predictive biomarkers. T-cell (LT) and Natural Killer (NK)-mediated antitumor immunity may impact TFR maintenance. We aim to correlate LT and NK phenotypes with measurable residual disease kinetics (TKI use) and TFR loss (discontinuation-DC). Healthy controls (CT) and 23 CML patients were studied. Patients included: 8 at diagnosis (DX), 4 treated >3 years with DMR4.5) at DC, followed at 3m (n=13), 6m (n=8), 9m (n=7), and 8 relapsed (R) at DC. Until 6m, patients had 50% TKI dose, then TKI was stopped. NK and LT frequency, subtypes, and maturation were assessed by flow cytometry. NK subtypes (CD45hiCD19-CD3-) were classified as secretory (CD56brightCD16-) or cytotoxic (CD56dimCD16+). CD19-CD3-CD56+ functional maturation included CD11b-CD27- (tolerant), CD27+CD11b- (immature secretory), CD27+CD11b+ (mature secretory), and CD11b+CD27- (cytotoxic), with CD57 and NKp80 activation markers. Subpopulations were analyzed based on BCR::ABL1 RT-qPCR levels. Compared to CT, active CML (DX, DMR<3, R) showed reduced total LT and NK, while good responders (DC) had increased LT (p=0.0002) and NK (p=0.0061). DX, DMR<3, R had reduced CD3+ and CD4+ and a trend of increased CD8+, while DC had increased CD3+ (p=0.0004) and CD4+ (p=0.0418) with a trend of reduced CD8+ (p>0.05). For NK subtypes - DX, DMR<3, R had decreased CD56dimCD16+, but DC had increased frequency (p=0.0017). CD56brightCD16- did not differ (p>0.05). In NK functional maturation - DX, DMR<3, R increased immature and tolerant secretory cells, while DC decreased immature (p=0.0387) and tolerant (p=0.0023) secretory cells with a trend of increased mature secretory cells (p>0.05). NK activation in DX, DMR<3, R showed decreased CD57+ (p=0.0358) and NKp80 (p=0.0036), while DC showed elevated values. Healthy, DMR>4.5 and DC patients had a mature NK profile similar to CT. Poor responders (DMR<3, R) exhibited an immature profile resembling DX with increased immature and tolerant secretory cells. CD56dim NK (antitumoral) frequency was reduced in active CML without achieving higher DMR. TKI use leds to BCR::ABL1 reduction concurrent with immune stimulation (recovering cytotoxic cells). NK activation via CD57 and NKp80 was impaired in molecular disease, suggesting monitoring CD4 and cytotoxic NK during discontinuation may predict TFR relapse. We aim to deepen these results for better understanding CML pathophysiology, prognosis, and monitoring, aiding individualized responses to TKI therapy and after discontinuation guiding therapeutic strategies in the context of healthcare systems and NK/LT-mediated immunotherapy.