ALBERT

Description: Background: Low oxygen levels are a defining characteristic of solid tumors, but the role of hypoxia in leukemogenesis remains unclear. Recent reports indicate that the endosteum at the murine bone-bone marrow (BM) interface is hypoxic, and data in a rat model demonstrate that leukemic cells infiltrating bone marrow were markedly hypoxic compared with cells in the BM of healthy rats. Hypoxia triggers a complex cellular and systemic adaptation mediated primarily through transcription by hypoxia inducible factors (HIFs) including HIF-1a. Although hypoxia is the best-characterized mechanism of HIF activation in tumors, HIF activity also can be induced in tumor cells through activation of the PI3K/Akt-signaling pathway. In this study, we assessed AKT and HIF-1a expression in newly diagnosed precursor B-cell acute lymphoblastic leukemia (pre-B ALL) and correlated the results with overall and progression-free patient survival. Methods: We analyzed expression of phosphorylated AKT (pAKT) and HIF-1a in leukemic cells by immunohistochemical methods using archival fixed, paraffin-embedded BM biopsy specimens of newly diagnosed pre-B ALL and antibodies specific for pAKT (Cell Signaling Technology, Beverly, MA) and HIF-1a (BD Biosciences, San Jose, CA). The initial observations were confirmed by a Reverse Phase Protein Array (RPPA) data set generated from protein lysates prepared from fresh blood and BM aspirate samples from patients with newly diagnosed pre-B ALL. Results: There were 26 men and 27 women with a median age of 39 years (range, 17–77). The median follow-up was 17 months (range, 1–71). The median WBC was 5.7 × 109/L (range, 0.8–369 × 109/L), the median percentage of blasts in bone marrow was 88% (range, 21–97%). Conventional cytogenetic studies detected a normal karyotype in 13 patients and abnormal karyotype in 37 patients including the Philadelphia chromosome (Ph) in 15 patients; no analyzable metaphases were recovered in 5 patients. Fluorescence in situ hybridization for BCR/ABL rearrangement was performed in all patients and was positive in all 15 patients with Ph and in 1 patient with normal conventional cytogenetics. 50 patients received HYPER-CVAD therapy, 3 patients received augmented BFM therapy. 49 (92%) patients achieved complete remission with a median time to response of 3 weeks (range, 2–8 weeks), 12 of them relapsed. 17 patients died, including 6 patients in complete remission. 3 year overall survival was 56% (CI, 46–66%). HIF-1a expression was detected in 37 (70%) patients, including 10 patients with Ph-positive ALL. HIF-1a expression was associated with expression of pAKT (R=0.4479, p