Hyperthermia promotes degradation of the acute promyelocytic leukemia driver oncoprotein ZBTB16/RARα.

The acute promyelocytic leukemia (APL) driver ZBTB16/RARα is generated by the t(11;17) (q23;q21) chromosomal translocation, which is resistant to combined treatment of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) or conventional chemotherapy, resulting in extremely low survival rates. In the current study, we investigated the effects of hyperthermia on the oncogenic fusion ZBTB16/RARα protein to explore a potential therapeutic approach for this variant APL. We showed that Z/R fusion protein expressed in HeLa cells was resistant to ATO, ATRA, and conventional chemotherapeutic agents. However, mild hyperthermia (42 °C) rapidly destabilized the ZBTB16/RARα fusion protein expressed in HeLa, 293T, and OCI-AML3 cells, followed by robust ubiquitination and proteasomal degradation. In contrast, hyperthermia did not affect the normal (i.e., unfused) ZBTB16 and RARα proteins, suggesting a specific thermal sensitivity of the ZBTB16/RARα fusion protein. Importantly, we found that the destabilization of ZBTB16/RARα was the initial step for oncogenic fusion protein degradation by hyperthermia, which could be blocked by deletion of nuclear receptor corepressor (NCoR) binding sites or knockdown of NCoRs. Furthermore, SIAH2 was identified as the E3 ligase participating in hyperthermia-induced ubiquitination of ZBTB16/RARα. In short, these results demonstrate that hyperthermia could effectively destabilize and subsequently degrade the ZBTB16/RARα fusion protein in an NCoR-dependent manner, suggesting a thermal-based therapeutic strategy that may improve the outcome in refractory ZBTB16/RARα-driven APL patients in the clinic.

Oral arsenic and retinoic acid for high-risk acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) has become curable over 95% patients under a complete chemo-free treatment with all-trans retinoic acid (ATRA) and arsenic trioxide in low-risk patients. Minimizing chemotherapy has proven feasible in high-risk patients. We evaluated oral arsenic and ATRA without chemotherapy as an outpatient consolidation therapy and no maintenance for high-risk APL. We conducted a multicenter, single-arm, phase 2 study with consolidation phases. The consolidation therapy included Realgar-Indigo naturalis formula (60 mg/kg daily in an oral divided dose) in a 4-week-on and 4-week-off regimen for 4 cycles and ATRA (25 mg/m2 daily in an oral divided dose) in a 2-week-on and 2-week-off regimen for 7 cycles. The primary end point was the disease-free survival (DFS). Secondary end points included measurable resident disease, overall survival (OS), and safety. A total of 54 participants were enrolled at seven centers from May 2019. The median age was 40 years. At the median follow-up of 13.8 months (through April 2022), estimated 2-year DFS and OS were 94% and 100% in an intention-to-treat analysis. All the patients achieved complete molecular remission at the end of consolidation phase. Two patients relapsed after consolidation with a cumulative incidence of relapse of 6.2%. The majority of adverse events were grade 1-2, and only three grade 3 adverse events were observed. Oral arsenic plus ATRA without chemotherapy was active as a first-line consolidation therapy for high-risk APL.Trial registration: chictr.org.cn number, ChiCTR1900023309.

Early Death and Survival of Patients With Acute Promyelocytic Leukemia in ATRA Plus Arsenic Era: A Population-Based Study.

Most randomized trials for acute promyelocytic leukemia (APL) have investigated highly selected patients under idealized conditions, and the findings need to be validated in the real world. We conducted a population-based study of all APL patients in Zhejiang Province, China, with a total population of 82 million people, to assess the generalization of all-trans retinoic acid (ATRA) and arsenic as front-line treatment. The outcomes of APL patients were also analyzed. Between January 2015 and December 2019, 1,233 eligible patients were included in the final analysis. The rate of ATRA and arsenic as front-line treatment increased steadily from 66.2% in 2015 to 83.3% in 2019, with no difference among the size of the center (≥5 or <5 patients per year, p = 0.12) or age (≥60 or <60 years, p = 0.35). The early death (ED) rate, defined as death within 30 days after diagnosis, was 8.2%, and the 3-year overall survival (OS) was 87.9% in the whole patient population. Age (≥60 years) and white blood cell count (>10 × 109/L) were independent risk factors for ED and OS in the multivariate analysis. This population-based study showed that ATRA and arsenic as front-line treatment are widely used under real-world conditions and yield a low ED rate and a high survival rate, which mimic the results from clinical trials, thereby supporting the wider application of APL guidelines in the future.