SB225002 induces cell death and cell cycle arrest in acute lymphoblastic leukemia cells through the activation of GLIPR1

Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1 , a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1 , seems to underlie the anti-leukemic effect of SB225002

Plasma Hsp90 Level as a Marker of Early Acute Lymphoblastic Leukemia Engraftment and Progression in Mice

<div><p>Current monitoring of acute lymphoblastic leukemia (ALL) in living mice is based on FACS analysis of blood hCD45+ cells. In this work, we evaluated the use of human IGFBP2, B2M or Hsp90 as soluble markers of leukemia. ELISA for B2M and IGFBP2 resulted in high background levels in healthy animals, precluding its use. Conversely, plasma levels of Hsp90 showed low background and linear correlation to FACS results. In another experiment, we compared Hsp90 levels with percentage of hCD45+ cells in blood, bone marrow, liver and spleen of animals weekly sacrificed. Hsp90 levels proved to be a superior method for the earlier detection of ALL engraftment and correlated linearly to ALL burden and progression in all compartments, even at minimal residual disease levels. Importantly, the Hsp90/hCD45+ ratio was not altered when animals were treated with dexamethasone or a PI3K inhibitor, indicating that chemotherapy does not directly interfere with leukemia production of Hsp90. In conclusion, plasma Hsp90 was validated as a soluble biomarker of ALL, useful for earlier detection of leukemia engraftment, monitoring leukemia kinetics at residual disease levels, and pre-clinical or mouse avatar evaluations of anti-leukemic drugs.</p></div

ELISA of plasma Hsp90 levels for earlier engraftment confirmation.

<p>(A) Experimental workflow. Cryopreserved primary ALL cells were thawed and injected into 3 mice for expansion. Fresh xenograph ALL cells were then injected into 6 to 12 secondary animals for experiments. For RS4;11 and TALL-1, cultured cells were directly injected in animals for the experiments. Animals were monitored weekly and sacrificed as indicated. (B) Kinetic of Hsp90 plasma levels over time, following ALL injection. Data points represent mean of 3 animals. The cut-off Hsp90 value (0.1 ng/mL) is indicated. Asterisks represent starting week of sequential sacrifice of animals (Time Point 1). Some groups did not have enough animals for the experiment to be carried out until the third week of sacrifice. (C) Percentage of ALL cells (hCD45+) in bone marrow (BM) and peripheral blood (PB) at the different time points. Data points represent mean of 3 animals. Dotted line represents the usual cut-off (0.5%) for ALL detection by flow cytometry in blood samples. Different ALL cells are represented by colors. Circles; BCP-ALL. Triangles, T-ALL.</p

Correlation between plasma Hsp90 level and percentage of ALL cells in the different tissues analyzed.

<p>One representative case of three BCP-ALL or T-ALL analyzed is shown. For complete data refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129298#pone.0129298.s002" target="_blank">S2 Fig</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129298#pone.0129298.s003" target="_blank">S3 Fig</a> ELISA Hsp90 and flow cytometry hCD45+ data were transformed to log10 and analyzed by Pearson’s correlation. Correlations between ALL in peripheral blood and in the different tissues are shown for comparisons. Dotted line represents cut-off values for ALL detection by flow cytometry (0.5%) or Hsp90 levels (0.1 ng/mL). Data points correspond to individual samples. Numbers near each data point represent time point of sampling (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129298#pone.0129298.g002" target="_blank">Fig 2</a>). PB; peripheral blood. BM; bone marrow. Circles, BCP-ALL. Triangles, T-ALL.</p

Analysis of three potential leukemia plasma biomarkers.

<p>(A) Peripheral blood B2M, IGFBP-2 and Hsp90 levels (ELISA) in NOD/SCID mice transplanted with a primary human T-ALL or healthy controls. Animals were divided into groups according to the percentage of ALL cells (hCD45+) in peripheral blood by FACS. Data points correspond to individual samples, and horizontal bars correspond to median. *P<0.05; Mann-Whitney U test. (B) Correlation between Hsp90 levels and % ALL cells in peripheral blood. Data points correspond to individual samples. Data were transformed to log10 and analyzed by Pearson’s correlation. (C) Cut-off value of Hsp90 (dotted line) as determined by adding 2 times SD to mean. Animals transplanted with different BCP-ALL (n = 3) and T-ALL (n = 2), sacrificed at the earliest time point (time point 1, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129298#pone.0129298.g002" target="_blank">Fig 2</a>) were included in the analysis. Leukemia engraftment was confirmed by FACS analysis. Data points correspond to individual samples. PB, peripheral blood; SD, standard deviation.</p

Chemotherapy effects on biomarkers levels.

<p>Plasma biomarkers levels (ELISA) and matched percentage of ALL cells (hCD45+) in peripheral blood (PB) from animals under chemotherapy treatment. Samples were collected for analysis at the beginning (C1 = day 5), middle (C2 = day 19) and end (C3 = day 33) of treatment. Colored bars represent mean ± SD of biomarker levels (left Y axis) for individual mice samples analyzed in duplicate. Different colors represent different treatments. The PI3K inhibitor used was AS605240. Black bars represent percentages of ALL cells in peripheral blood (right Y axis). The dotted line in the Hsp90 graphic represents the ELISA cut-off value. Red arrows highlight lower than expected ELISA values, when compared to levels found in untreated animals with similar percentage of ALL cells.</p