NFKB1 Haplotype Boosts Response to Ropeginterferon in MPN Subtypes

NFKB1 rs230511 genetic variant improves treatment outcomes for patients with polycythemia vera and essential thrombocythemia.

A recent study presented at the 2024 American Society of Hematology Annual Meeting and Exposition revealed that patients with polycythemia vera (PV) and essential thrombocythemia (ET) who carry the NFKB1 rs230511 haplotype experience reduced inflammation and a more pronounced response to ropeginterferon alfa-2b (Besremi) treatment.¹

Among 30 patients with PV and 15 with ET, the NFKB1 rs230511 haplotype was more common among those who experienced a complete hematologic response (CHR) to ropeginterferon alfa-2b treatment (58.6%) compared with those who did not (33.3%; P < .0001). A CHR was defined as a white blood cell count of less than 10,000/uL, hematocrit levels less than 49%, and a platelet count of less than 400,000/uL. Patients with cytopenia were classified as not having a CHR.

“PV and ET are caused by mutations in hematopoietic stem cells [and although] PV leads to a high hemoglobin level, ET is marked by an increase in platelet count,” Jihyun Song, PhD, research assistant professor, Division of Hematology & Hematologic Malignancies, University of Utah Huntsman Cancer Institute, Salt Lake City, said during a presentation of the data. “The genetic drivers of these disorders are different. PV is linked to gain of function mutation[s] in JAK2 and ET is caused by mutations of JAK2, CALR, and/or MPL. However, both disorders result in hyperactive JAK-STAT pathway signaling that plays a key role in increased expression of inflammatory genes; one of the features of PV and ET is chronic inflammation. This chronic inflammation increases the severity of disease, and addressing it is a critical aspect of managing these disorders.”

JAK inhibitors do not completely normalize elevated inflammation in PV and ET, suggesting that other pathways beyond the JAK-STAT pathway are contributing to chronic inflammation, Song continued. NFKB1 plays a central role in inflammation as a master regulator of inflammation in PV and ET, as this pathway is activated in these diseases, she said.

In November 2021, the FDA approved ropeginterferon alfa-2b for the treatment of adult patients with PV.² The regulatory decision was supported by findings from the phase 1/2 PEGINVERA study(NCT01193699), which demonstrated that patients who received the interferon therapy (n = 51) experienced a CHR rate of 61%. Notably, ropeginterferon alfa-2b was the first agent approved in PV that patients are permitted to receive irrespective of their treatment history.

To conduct their study, Song and her coauthors identified genetic variants associated with high altitude adaptation across Andean, Ethiopian, and Tibetan populations.¹ Investigators noted that although Ethiopian and Tibetan individuals maintained hemoglobin levels similar with those observed at sea level, Andean individuals exhibited higher hemoglobin levels compared with sea level and high-altitude European populations.

To determine why this was the case, study authors performed whole transcriptome analysis of granulocytes from 7 Aymaran individuals and 4 European individuals living at 4000 m above sea level in La Paz, Bolivia. They found that most of the dysregulated genes were involved in the inflammatory pathway, including the NF-KB pathway. Using the STRING database, investigators performed a protein-protein analysis which demonstrated that NFKB1 was highlighted as a half gene.

Upon whole transcriptional analysis, investigators identified 3 novel alternatively spliced transcripts of NFKB1 (AS-NFKB1): exon 14 skipped (AS1), exon 5 skipped (AS2), and both exons 4 and 5 skipped (AS3). These AS-NFKB1 transcripts were observed at higher levels among the Aymaran individuals compared with the European individuals.

“NFKB1 is a crucial component of NF-KB transcription factor [and] has a door function in inflammation, acting as both an inducer and a suppressor of inflammation,” Song explained. “To identify any genetic signatures associated with the spliced NFKB1 transcript labels, we looked at whole-genome sequencing [data] and found NFKB1 rs230511. This was more common in 2 Andean populations, Aymaran and Quechuan, and was also present in other populations. NFKB1 is a key regulator of inflammation and we found that individuals with the Aymaran-enriched allele [T] have higher inflammatory gene expression and protein levels.”

Most Aymaran (87.8%) and Quechuan (76%) individuals expressed the NFKB1 rs230511-enriched allele. Comparatively, it was present in Tibetan (36.4%), Han Chinese (38.8%), European (33.4%), and Yoruban (0.9%) individuals at much lower rates.

Song went on to note that AS-NFKB1 and NFKB1 rs230511 was positively correlated with IL-6 and IFN-γ levels. Canonical NFKB1 expression levels were not correlated with IL-6 and IFN-γ transcript levels in granulocytes and AS-NFKB1 was correlated with the upregulation of hypoxia-inducible factors (HIFs) and increased hemoglobin in Aymaran individuals.

“We conducted an experiment to test whether AS-NFKB1 alters inflammatory gene expression under inflammatory stress [when] induced by tumor necrosis factor [TNF] treatment,” Song said. “Using an HL60 neutrophil cell line, we transfected plasmids containing each NFKB1 variant and treated the cell [line] with or without TNF.”

Cytoplasmic NFKB1 showed no significant differences under any conditions. However, treatment with TNF induced nuclear translocation of NFKB1. Additionally, NFKB1 splice variants reduced NFKB1 translocation compared with canonical NFKB1. Overexpression of NFKB1 splice variants induced inflammatory gene expression and the NFKB1 variants decreased inflammatory gene expression under inflammatory stress from TNF treatment.

Additional data from the study showed that patients who did not experience a CHR had the C/C and T/T genotypes at rates of 44.44% and 22.22%, respectively. These respective rates were 34.48% and 6.90% among those who achieved a CHR. Individuals with the C/T or T/T genotype also displayed significantly lower inflammatory gene expression compared with those with the C/C genotype.

“We observed lower level of inflammatory gene expression in PV and ET with the C/T genotype, and these patients are more likely to achieve CHRs by ropeginterferon alfa-2b treatment,” Song said in conclusion. “These findings suggest that NFKB1 could serve as a biomarker for treatment response in PV and ET.”

References

1. Song J, Kim SJ, Prchal JT. Andean enriched NFKB1 haplotype reduces inflammation and improves response to ropeginterferon alfa-2b in polycythemia vera (PV) and essential thrombocythemia (ET). Blood. 2024;144(suppl 2):LBA-4. doi:10.1182/blood-2024-213103
2. FDA approves treatment for rare blood disease. FDA. November 12, 2021. Accessed December 10, 2024. https://www.fda.gov/news-events/press-announcements/fda-approves-treatment-rare-blood-disease#:~:text=For%20Immediate%20Release:%20November%2012,is%20one%20of%20these%20medicines