Hyperthermia Selectively Destabilizes Oncogenic Fusion Proteins.

The PML/RARα fusion protein is the oncogenic driver in acute promyelocytic leukemia (APL). Although most APL cases are cured by PML/RARα-targeting therapy, relapse and resistance can occur due to drug-resistant mutations. Here we report that thermal stress destabilizes the PML/RARα protein, including clinically identified drug-resistant mutants. AML1/ETO and TEL/AML1 oncofusions show similar heat shock susceptibility. Mechanistically, mild hyperthermia stimulates aggregation of PML/RARα in complex with nuclear receptor corepressors leading to ubiquitin-mediated degradation via the SIAH2 E3 ligase. Hyperthermia and arsenic therapy destabilize PML/RARα via distinct mechanisms and are synergistic in primary patient samples and in vivo, including three refractory APL cases. Collectively, our results suggest that by taking advantage of a biophysical vulnerability of PML/RARα, thermal therapy may improve prognosis in drug-resistant or otherwise refractory APL. These findings serve as a paradigm for therapeutic targeting of fusion oncoprotein-associated cancers by hyperthermia. SIGNIFICANCE: Hyperthermia destabilizes oncofusion proteins including PML/RARα and acts synergistically with standard arsenic therapy in relapsed and refractory APL. The results open up the possibility that heat shock sensitivity may be an easily targetable vulnerability of oncofusion-driven cancers.See related commentary by Wu et al., p. 300.

The impact of oral arsenic and all-trans-retinoic acid on coagulopathy in acute promyelocytic leukemia.

The aim of our study was to evaluate the impact of oral arsenic (the realgar-indigo naturalis formula, RIF) and all-trans retinoic acid (ATRA) on coagulopathy in acute promyelocytic leukemia (APL) compared with intravenous arsenic trioxide (ATO) and ATRA during induction. Mitoxantrone was added to all the patients at a dose of 1.4mg/m2 per day for 5-7 days. D-dimer levels, prothrombin time (PT), fibrinogen (Fbg) levels and the platelet count were comparably analyzed among 83 newly diagnosed APL patients treated with RIF (n=45) or with ATO (n=38). Since induction therapy with RIF and ATRA, the median levels of Fbg, PT and platelets were recovered to the normal range within 4days, 10days and 28days, respectively. The last day of platelet and plasma transfusion was day 12 (range: 0-24 days) and day 3 (range: 0-27 days), respectively. Among the 42 patients with a disseminated intravascular coagulation (DIC) score=4, the consumption of transfused platelets was less in the RIF group than that in the ATO group (P=0.037). In the 17 patients with a DIC score <4, prompt recovery of Fbg levels (P=0.028) was observed in the RIF group compared with that in the ATO group (P=0.401). RIF and ATO showed similar effects on the recovery of coagulopathy in APL patients. RIF had a potential beneficial effect in accelerating the recovery of thrombocytopenia and hypofibrinogenemia for subclinical DIC patients.

The kinetics of white blood cell and the predictive factors of leukocytosis under oral or intravenous arsenic as the first-line treatment for acute promyelocytic leukemia.

OBJECTIVE: We aimed to compare the kinetics of white blood cell (WBC) and explore predictive factors of leukocytosis in non-high-risk acute promyelocytic leukemia (APL), with oral arsenic plus all-trans retinoic acid (ATRA) or intravenous arsenic trioxide (ATO) plus ATRA as a first-line treatment. METHODS: The absolute count, doubling time and peak time of WBC were analyzed in 64 newly diagnosed non-high-risk APL patients who were treated with different induction regimens containing either oral Realgar-indigo naturalis formula (RIF) (n=35) or ATO (n=29). The end points were the dynamic changes of the WBC counts during induction. The time points started at day 1 and were selected over 3-day intervals for 28days. RESULTS: Among the 64 included patients, the median initial and peak WBC counts were 1.78×109/L (range 0.31-9.89) and 12.16×109/L (range 1.56-80.01), respectively. The incidence of differentiation syndrome was 9.38%. The dynamic changes in leukocytosis showed a single peak wave in all the patients, and the median time to peak was 10 (range 2-26) days. A higher WBC count was observed in the RIF group than in the ATO group after 10days of treatment (9.22×109/L vs. 4.10×109/L, p=0.015). Patients with the peak WBC count >10×109/L had a shorter WBC doubling time compared to patients with a lower peak WBC (RIF group 4days vs. 7days, p=0.001; ATO group 4.5days vs. 23days, p=0.002). Univariate and multivariable analyses showed that the doubling time of WBC is an independent factor for the peak WBC count. CONCLUSION: Different kinetics of WBC proliferation were observed during induction with oral arsenic plus ATRA and ATO plus ATRA. The doubling time of WBC is an important independent factor for predicting the peak WBC count.

Oral tetra-arsenic tetra-sulfide formula versus intravenous arsenic trioxide as first-line treatment of acute promyelocytic leukemia: a multicenter randomized controlled trial.

PURPOSE: This randomized, multicenter, phase III noninferiority trial was designed to test the efficacy and safety of an oral tetra-arsenic tetra-sulfide (As4S4) -containing formula named the Realgar-Indigo naturalis formula (RIF) compared with intravenous arsenic trioxide (ATO) as both induction and maintenance therapies for newly diagnosed acute promyelocytic leukemia (APL). PATIENTS AND METHODS: In all, 242 patients with APL were randomly assigned (1:1) to oral RIF (60 mg/kg) or ATO (0.16 mg/kg) combined with all-trans retinoic acid (ATRA; 25 mg/m(2)) during induction therapy. After achieving complete remission (CR), all patients received three courses of consolidation chemotherapy and maintenance treatment with sequential ATRA followed by either RIF or ATO for 2 years. The primary end point was the rate of disease-free survival (DFS) at 2 years, which was assessed for noninferiority with a 10% noninferiority margin. RESULTS: The median follow-up time was 39 months. DFS at 2 years was 98.1% (106 of 108) in the RIF group and 95.5% (107 of 112) in the ATO group. The DFS difference was 2.6% (95% CI, -3.0% to 8.0%). The lower limit of the 95% CI of DFS difference was greater than the -10% noninferiority margin, confirming noninferiority (P < .001). No significant differences were noted between the RIF and ATO groups with regard to the CR rate (99.1% v 97.2%; P = .62) or the overall survival at 3 years (99.1% v 96.6%; P = .18). The rates of adverse events were similar in the two groups. CONCLUSION: Oral RIF plus ATRA is not inferior to intravenous ATO plus ATRA as first-line treatment of APL and may be considered as a routine treatment option for appropriate patients.