Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML), characterized by the oncogenic fusion protein PML-RARα, which results from the t(15;17) chromosomal translocation. APL accounts for approximately 4-10% of AML cases worldwide. The median age at diagnosis falls around the fifth decade of life, with a slight male predominance (PMID: 39682277).

The PML-RARα fusion protein plays an essential role in the pathogenesis of APL by enhancing hypoxia-inducible factor (HIF)-driven transcriptional activity. PML-RARα acts as a transcriptional co-activator of HIF-α, amplifying HIF-mediated transcription independently of PML protein inhibition. This activation is unique to APL-specific fusion proteins; it is absent in other AML subtypes. The interaction of PML-RARα and HIF factors significantly influences disease progression and relapse. (PMID: 24711541).

Transcriptomic analyses of APL cells reveal enrichment of NF-κB signaling pathways among differentially expressed genes, particularly those involved in cancer pathways. This suggests that NFKB1 contributes to the proliferative and survival signaling in APL cells (Villiers W, Nat. Commun, 2023). However, PML-RARα disrupts NF-κB activity by inhibiting phosphorylation and DNA binding of the NF-κB p65 subunit, suppressing NF-κB target gene expression. This disruption contributes to leukemogenesis through impaired differentiation and altered transcriptional regulation (Ahmed A, Sci.rep, March 2017).

The incidence of APL varies across geographic regions and ethnic groups. Higher frequencies have been observed in Latin American populations compared to North America and Europe. These disparities suggest that genetic and environmental factors contribute to differences in disease distribution and outcomes (PMID: 12935956) and currently, there are no published data directly comparing APL incidence between populations living at sea level and those residing at high altitudes.

We investigated the proportion of AML cases diagnosed as APL in Bolivian Andean highlanders residing at 4000 m, a population characterized by elevated HIF-α expression and a predominant NFKB1 haplotype rs230511 (95%) that results in a non-functional NFKB1 protein. We then compared the proportion of APL cases from Bolivian populations living at 2000m and 400 m.

We analyzed 1,273 AML diagnoses from January 2000 to June 2025, grouped by altitude of residence: 406 at 4,000 m (mean age 37 years), 412 at 2,000 m (mean age 41 years), and 455 at 400 m (mean age 28 years). The overall mean age at AML diagnosis was 35 ± 25 years, with a male predominance of 54%. Among the total AML cases, 140 (11.0%) were identified as APL.

We compared the proportion of AML cases classified as APL across three altitudes: at 4,000 m, 38 of 406 AML cases (9.4%) were APL; at 2,000 m, 46 of 412 cases (11.2%); and at 400 m, 56 of 455 cases (12.3%). There was a trend toward a lower proportion of APL cases at 4,000 m compared to 2,000 m and 400 m, although this difference was not statistically significant (P = 0.17).

The age distribution of APL cases was as follows: 1-17 years, 44 cases (31.4%); 18-39 years, 59 cases (41.7%); 40–59 years, 30 cases (21.4%); and ≥60 years, 7 cases (5.0%). The age of AML patients was significantly lower at 400 m compared to the higher altitudes, whereas the proportion of males did not differ significantly by altitude.

Conclusions

  • The APL tends to decrease with increasing altitude, consistent with genetic adaptations in high-altitude Andean populations (~4000 m) involving increased HIF activity and a specific NFKB1 haplotype

  • The 25-year incidence of APL was significantly lower in the La Paz population at 4000 m compared to populations at lower elevations (P < 0.020).

  • Individuals younger than 40 years are disproportionately affected, representing 73.1% of APL cases. The increased incidence in younger age groups does not vary by altitude, suggesting that genetic factors may predominantly drive this demographic pattern.

  • Investigating genetic adaptations in high-altitude populations could offer novel insights into APL pathobiology and therapeutic strategies.

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2025
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