Background

Myeloproliferative neoplasms (MPN) are rare blood cancers where genetic mutations in hematopoietic stem cells cause abnormal overproduction of specific blood cells such as red blood cells, platelets, and white blood cells. The JAK2 gene mutation is a primary driver, posing high risks of thrombosis or progression to acute myeloid leukemia if left untreated. Clinically, long-term administration of interferon-alpha (IFN-α) has been used to lower blood cell counts and suppress disease exacerbation. In some patients, molecular genetic remission—a significant reduction in the proportion of malignant hematopoietic stem cell clones carrying mutations—has been observed.

Despite proven clinical efficacy, the exact molecular biological pathway through which IFN-α suppresses abnormal blood cell production and selectively controls mutant cells has remained a long-standing mystery. Existing blood analysis methods and bulk sequencing were limited by measuring average values within a mixture of hundreds of millions of cells. It was difficult to precisely track how individual hematopoietic stem cells respond to drugs and alter differentiation pathways within the bone marrow microenvironment, where normal and tumor mutant cells coexist. Consequently, it was difficult for clinicians to predict which patients would respond to treatment in advance, and identifying drug resistance mechanisms faced significant hurdles.

Key Findings

The researchers applied single-cell multiomics technology, combining single-cell RNA sequencing (scRNA-seq) and genomic mutation analysis, to hematopoietic stem cells isolated from the bone marrow of MPN patients. They reconstructed cell differentiation trajectories by mapping the gene expression profiles and JAK2 mutation status of individual stem cells before and after IFN-α administration.

Analysis revealed that IFN-α completely redirected the fate of hematopoietic stem cells at their differentiation branch points. First, the drug blocked the flow where hematopoietic stem cells were abnormally biased toward myeloid differentiation and significantly strengthened lymphoid differentiation signals. As the differentiation programs for B-cell and T-cell precursors, which are commonly suppressed in myeloproliferative neoplasms (MPN), were promoted, excessive proliferation of red blood cells and platelets was inhibited, and peripheral blood counts returned to normal ranges.

The drug also revealed a novel cell death pathway in mutant clones. Unlike normal cells, JAK2-mutant hematopoietic stem cells stimulated by IFN-α were driven into a chronic inflammatory myeloid differentiation pathway. In this process, mutant stem cells lost their inherent self-renewal capacity and were forced to differentiate into terminal inflammatory cells, leading to gradual depletion. This confirms a mechanism of clonal dynamics control in which the drug does not directly and immediately kill mutant cells, but instead induces excessive inflammatory differentiation to cause their natural elimination from the stem cell pool.

Significance and Outlook

This achievement is of profound significance as it elucidated the mechanistic 'black box' of interferon therapy—long reliant on empirical approaches—at single-cell resolution. It clearly demonstrated that the reduction in abnormal blood counts and the suppression of malignant clones are driven independently yet complementarily at distinct cell differentiation branch points.

Clinically, this provides a major turning point for establishing personalized treatment strategies. Signatures of lymphocyte differentiation and markers of inflammatory myeloid differentiation captured at the single-cell level can be utilized as biomarkers to identify initial responders and non-responders to treatment. Furthermore, it provides a solid theoretical foundation for designing next-generation targeted therapies or combination therapies that precisely stimulate only these differentiation pathways while reducing the toxic side effects of IFN-α.

However, several challenges remain before these research results can be immediately applied to actual clinical practice. Since the cohort size used for single-cell multiomics analysis was limited, large-scale validation is required to generalize the mechanism across patient groups possessing various genetic mutations (such as CALR, MPL, etc.). Studies of follow-up clinical protocols to block the emergence of treatment-resistant clones during long-term administration should also be conducted in parallel.