A multiparametric niche-like drug screening platform in acute myeloid leukemia.

Functional precision medicine in AML often relies on short-term in vitro drug sensitivity screening (DSS) of primary patient cells in standard culture conditions. We designed a niche-like DSS assay combining physiologic hypoxia (O2 3%) and mesenchymal stromal cell (MSC) co-culture with multiparameter flow cytometry to enumerate lymphocytes and differentiating (CD11/CD14/CD15+) or leukemic stem cell (LSC)-enriched (GPR56+) cells within the leukemic bulk. After functional validation of GPR56 expression as a surrogate for LSC enrichment, the assay identified three patterns of response, including cytotoxicity on blasts sparing LSCs, induction of differentiation, and selective impairment of LSCs. We refined our niche-like culture by including plasma-like amino-acid and cytokine concentrations identified by targeted metabolomics and proteomics of primary AML bone marrow plasma samples. Systematic interrogation revealed distinct contributions of each niche-like component to leukemic outgrowth and drug response. Short-term niche-like culture preserved clonal architecture and transcriptional states of primary leukemic cells. In a cohort of 45 AML samples enriched for NPM1c AML, the niche-like multiparametric assay could predict morphologically (p = 0.02) and molecular (NPM1c MRD, p = 0.04) response to anthracycline-cytarabine induction chemotherapy. In this cohort, a 23-drug screen nominated ruxolitinib as a sensitizer to anthracycline-cytarabine. This finding was validated in an NPM1c PDX model.

The Folate Cycle Enzyme MTHFR Is a Critical Regulator of Cell Response to MYC-Targeting Therapies.

Deciphering the impact of metabolic intervention on response to anticancer therapy may elucidate a path toward improved clinical responses. Here, we identify amino acid-related pathways connected to the folate cycle whose activation predicts sensitivity to MYC-targeting therapies in acute myeloid leukemia (AML). We establish that folate restriction and deficiency of the rate-limiting folate cycle enzyme MTHFR, which exhibits reduced-function polymorphisms in about 10% of Caucasians, induce resistance to MYC targeting by BET and CDK7 inhibitors in cell lines, primary patient samples, and syngeneic mouse models of AML. Furthermore, this effect is abrogated by supplementation with the MTHFR enzymatic product CH3-THF. Mechanistically, folate cycle disturbance reduces H3K27/K9 histone methylation and activates a SPI1 transcriptional program counteracting the effect of BET inhibition. Our data provide a rationale for screening MTHFR polymorphisms and folate cycle status to nominate patients most likely to benefit from MYC-targeting therapies. SIGNIFICANCE: Although MYC-targeting therapies represent a promising strategy for cancer treatment, evidence of predictors of sensitivity to these agents is limited. We pinpoint that folate cycle disturbance and frequent polymorphisms associated with reduced MTHFR activity promote resistance to BET inhibitors. CH3-THF supplementation thus represents a low-risk intervention to enhance their effects.See related commentary by Marando and Huntly, p. 1791.This article is highlighted in the In This Issue feature, p. 1775.

Acute myeloid leukemia in the elderly.

The incidence of acute myeloid leukemia (AML) is increasing with age. As the results associated with standard intensive chemotherapy remain particularly disappointing in older patients, they represent an ideal target population for clinical and therapeutic investigations. Current attempts are to better define those who may draw a significant benefit from intensive chemotherapy, in order to test new less intensive approaches in the remaining patients. Hopefully, a lot of promising alternative therapies are emerging, including hypomethylating agents, histone deacetylase inhibitors, monoclonal antibodies, or chemotherapeutic agents such as cloretazine or clofarabine. Reduced-intensity conditioning stem cell transplantation or other various immunological approaches represent another way of investigation.

Dasatinib crosses the blood-brain barrier and is an efficient therapy for central nervous system Philadelphia chromosome-positive leukemia.

Although imatinib, a BCR-ABL tyrosine kinase inhibitor, is used to treat acute Philadelphia chromosome-positive (Ph(+)) leukemia, it does not prevent central nervous system (CNS) relapses resulting from poor drug penetration through the blood-brain barrier. Imatinib and dasa-tinib (a dual-specific SRC/BCR-ABL kinase inhibitor) were compared in a preclinical mouse model of intracranial Ph(+) leukemia. Clinical dasatinib treatment in patients with CNS Ph(+) leukemia was assessed. In preclinical studies, dasatinib increased survival, whereas imatinib failed to inhibit intracranial tumor growth. Stabilization and regression of CNS disease were achieved with continued dasa-tinib administration. The drug also demonstrated substantial activity in 11 adult and pediatric patients with CNS Ph(+) leukemia. Eleven evaluable patients had clinically significant, long-lasting responses, which were complete in 7 patients. In 3 additional patients, isolated CNS relapse occurred during dasatinib therapy; and in 2 of them, it was caused by expansion of a BCR-ABL-mutated dasatinib-resistant clone, implying selection pressure exerted by the compound in the CNS. Dasatinib has promising therapeutic potential in managing intracranial leukemic disease and substantial clinical activity in patients who experience CNS relapse while on imatinib therapy. This study is registered at ClinicalTrials.gov as CA180006 (#NCT00108719) and CA180015 (#NCT00110097).

Treatment of newly diagnosed acute promyelocytic leukemia (APL): a comparison of French-Belgian-Swiss and PETHEMA results.

All-trans retinoic acid (ATRA) plus anthracycline chemotherapy is the reference treatment of newly diagnosed acute promyelocytic leukemia (APL), whereas the role of cytosine arabinoside (AraC) remains disputed. We performed a joint analysis of patients younger than 65 years included in Programa para el Estudio de la Terapéutica en Hemopatía Maligna (PETHEMA) LPA 99 trial, where patients received no AraC in addition to ATRA, high cumulative dose idarubicin, and mitoxantrone, and APL 2000 trial, where patients received AraC in addition to ATRA and lower cumulative dose daunorubicin. In patients with white blood cell (WBC) count less than 10 x 10(9)/L, complete remission (CR) rates were similar, but 3-year cumulative incidence of relapse (CIR) was significantly lower in LPA 99 trial: 4.2% versus 14.3% (P = .03), although 3-year survival was similar in both trials. This suggested that AraC is not required in APL with WBC count less than 10 x 10(9)/L, at least in trials with high-dose anthracycline and maintenance treatment. In patients with WBC of 10 x 10(9)/L or more, however, the CR rate (95.1% vs 83.6% P = .018) and 3-year survival (91.5% vs 80.8%, P = .026) were significantly higher in APL 2000 trial, and there was a trend for lower 3-year CIR (9.9% vs 18.5%, P = .12), suggesting a beneficial role for AraC in those patients.

Phase II trial of arsenic trioxide and alpha interferon in patients with relapsed/refractory adult T-cell leukemia/lymphoma.

Human T-cell lymphotropic virus type 1 associated adult T-cell leukemia/lymphoma carries a very poor prognosis due to its intrinsic resistance to chemotherapy. Although zidovudine (AZT) and alpha-interferon (IFN) yield some responses and improve ATL prognosis, alternative therapies are needed. Arsenic trioxide (As) dramatically synergizes with IFN to induce growth arrest and apoptosis of ATL leukemia cells in vitro. These results prompted us to initiate a phase II trial of As/IFN combination in seven patients with relapsed/refractory ATL (four acute and three lymphoma). Four patients exhibited a clear initial response (one complete remission and three partial remissions). Yet, the treatment was discontinued after a median of 22 days because of toxicity (three patients) or subsequent progression (four patients). Six patients eventually died from progressive disease (five patients) or infection (one patient), but the remaining patient is still alive and disease free at 32 months. Pharmacokinetic studies showed that maximum arsenic blood levels (median 0.46 microM) were slowly achieved (8-15 days). In conclusion, arsenic/IFN treatment is feasible and exhibits an anti-leukemia effect in very poor prognosis ATL patients despite a significant toxicity. Future studies should assess the best timing for arsenic therapy: frontline with IFN/AZT or as maintenance after induction.