Antitumor Activity of a Novel Sphingosine-1-Phosphate 2 Antagonist, AB1, in Neuroblastoma

The bioactive lipid sphingosine-1-phosphate (S1P) and its receptors (S1P1-5) play critical roles in many pathologic processes, including cancer. The S1P axis has become a bona fide therapeutic target in cancer. JTE-013 [N-​(2,​6-​dichloro-​4-​pyridinyl)-​2-​[1,​3-​dimethyl-​4-​(1-​methylethyl)-​1H-​pyrazolo[3,​4-​b]pyridin-​6-​yl]-​hydrazinecarboxamide], a known S1P2 antagonist, suffers from instability in vivo. Structurally modified, more potent, and stable S1P2 inhibitors would be desirable pharmacological tools. One of the JTE-013 derivatives, AB1 [N-(1H-4-isopropyl-1-allyl-3-methylpyrazolo[3,4-b]pyridine-6-yl)-amino-N'-(2,6-dichloropyridine-4-yl) urea], exhibited improved S1P2 antagonism compared with JTE-013. Intravenous pharmacokinetics indicated enhanced stability or slower clearance of AB1 in vivo. Migration assays in glioblastoma showed that AB1 was slightly more effective than JTE-013 in blocking S1P2-mediated inhibition of cell migration. Functional studies in the neuroblastoma (NB) cell line SK-N-AS showed that AB1 displayed potency at least equivalent to JTE-013 in affecting signaling molecules downstream of S1P2. Similarly, AB1 inhibition of the growth of SK-N-AS tumor xenografts was improved compared with JTE-013. Cell viability assays excluded that this enhanced AB1 effect is caused by inhibition of cancer cell survival. Both JTE-013 and AB1 trended to inhibit (C-C motif) ligand 2 expression and were able to significantly inhibit subsequent tumor-associated macrophage infiltration in NB xenografts. Interestingly, AB1 was more effective than JTE-013 in inhibiting the expression of the profibrotic mediator connective tissue growth factor. The terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling assay and cleaved caspase-3 detection further demonstrated that apoptosis was increased in AB1-treated NB xenografts compared with JTE-013. Overall, the modification of JTE-013 to produce the AB1 compound improved potency, intravenous pharmacokinetics, cellular activity, and antitumor activity in NB and may have enhanced clinical and experimental applicability.

Induction of chemokine (C-C motif) ligand 2 by sphingosine-1-phosphate signaling in neuroblastoma

BACKGROUND/PURPOSE

Neuroblastoma (NB) is the most common extracranial solid tumor of childhood. Preliminary data derived from a human angiogenesis array in NB showed that the bioactive lipid sphingosine-1-phosphate (S1P) induced the secretion of several angiogenesis-related proteins including the important inflammatory factor chemokine (C-C motif) ligand 2 (CCL2). In the present study, we investigated the mechanism of S1P-induced CCL2 expression in NB.

METHODS

Quantitative real-time PCR and CCL2 ELISA were conducted to detect the mRNA expression and protein secretion of CCL2 in NB cells. Gain and loss of function studies were performed by using specific S1PR antagonists, adenoviral transduction and siRNA transfection. Macrophage F4/80 receptor in NB xenografts was detected by quantitative real-time PCR and immunohistochemistry staining.

RESULTS

S1P induced CCL2 mRNA expression and protein secretion in a time- and concentration-dependent manner in NB cells. Blockade of S1P2 signaling using the selective S1P2 antagonist JTE-013 inhibited S1P-induced CCL2 expression. Overexpression of S1P2 by adenoviral transduction increased CCL2 secretion while knockdown of S1P2 by siRNA transfection decreased S1P-induced CCL2 secretion in NB cells. Macrophage infiltration, as detected by F4/80 staining, was significantly decreased in JTE-013-treated NB xenografts.

CONCLUSIONS

Taken together, our data for the first time demonstrate that S1P induced the macrophage-recruiting factor CCL2 expression in NB cells via S1P2, providing new insights into the complicated functions of S1P2 in cancer.

Optical Properties of CdS and CdTe Sensitized ZnO Nanorods

Optical properties of ZnO-CdTe electrochemically prepared on a core-shell nanostructure (NS) were studied. Numerical simulations based on effective medium approximation give higher absorption than ZnO-CdS samples and a sensitive dependence on CdTe content. The absorption edges for deep black samples found by transmittance (T(λ)) and diffuse reflectance (Rdiff(λ)) measurements were at 1.33eV and 1.55eV, respectively. A split-off band edge was also found by Rdiff(λ) at ∼2.5eV. The red shift observed in T(λ), previously observed in ZnO-CdS, and may confirm the enhancement of sub-bandgap absorption due to the NS nature of samples.

FTY720 inhibits tumor growth and enhances the tumor-suppressive effect of topotecan in neuroblastoma by interfering with the sphingolipid signaling pathway

BACKGROUND

Neuroblastoma (NB) is the most common extra-cranial solid tumor in childhood. Poor outcomes for children with advanced disease underscore the need for novel therapeutic strategies. FTY720, an immunomodulating drug approved for multiple sclerosis, has been investigated in oncology with promising preclinical activities. To date, its effect in NB has not been explored. Herein we describe our preclinical experience with FTY720, alone or in combination with topotecan, and its putative mechanism of action in NB.

PROCEDURE

MTT assay was performed to assess the effect of FTY720 on cell viability. A NB xenograft model was employed to assess the efficacy of FTY720 on tumor growth. Quantitative real-time PCR and Western blot were employed to determine changes of mRNA and protein expression, respectively. Liquid chromatography/tandem mass spectrometry was used to measure sphingolipid levels.

RESULTS

FTY720, but not FTY720-P induced NB cell death. FTY720 inhibited the growth of NB xenografts and enhanced the tumor-suppressive effect of topotecan both in vitro and in vivo. FTY720 significantly inhibited sphingosine kinase 2 (SphK2) mRNA and protein expression in NB cells. Pro-apoptotic sphingosine levels were increased in NB cells and NB xenografts treated with FTY720. FTY720-induced cell death was caspase-independent and involved the dephosphorylation of Akt and BAD at Ser136.

CONCLUSIONS

Our data demonstrate that FTY720 has potent preclinical anti-cancer activity in NB. Its unique death signaling mechanism, interference with the sphingolipid pathway, acts cooperatively with that of topotecan, suggesting that FTY720 related molecules may be useful in NB treatment.

Inter- and intraradiologist variability in the BI-RADS assessment and breast density categories for screening mammograms

OBJECTIVE

The aim of this study was to evaluate reader variability in screening mammograms according to the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) assessment and breast density categories.

METHODS

A stratified random sample of 100 mammograms was selected from a population-based breast cancer screening programme in Barcelona, Spain: 13 histopathologically confirmed breast cancers and 51 with true-negative and 36 with false-positive results. 21 expert radiologists from radiological units of breast cancer screening programmes in Catalonia, Spain, reviewed the mammography images twice within a 6-month interval. The readers described each mammography using BI-RADS assessment and breast density categories. Inter- and intraradiologist agreement was assessed using percentage of concordance and the kappa (κ) statistic.

RESULTS

Fair interobserver agreement was observed for the BI-RADS assessment [κ=0.37, 95% confidence interval (CI) 0.36-0.38]. When the categories were collapsed in terms of whether additional evaluation was required (Categories III, 0, IV, V) or not (I and II), moderate agreement was found (κ=0.53, 95% CI 0.52-0.54). Intra-observer agreement for BI-RADS assessment was moderate using all categories (κ=0.53, 95% CI 0.50-0.55) and substantial on recall (κ=0.66, 95% CI 0.63-0.70). Regarding breast density, inter- and intraradiologist agreement was substantial (κ=0.73, 95% CI 0.72-0.74 and κ=0.69, 95% CI 0.68-0.70, respectively).

CONCLUSION

We observed a substantial intra-observer agreement in the BI-RADS assessment but only moderate interobserver agreement. Both inter- and intra-observer agreement in mammographic interpretation of breast density was substantial. Advances in knowledge Educational efforts should be made to decrease radiologists' variability in BI-RADS assessment interpretation in population-based breast screening programmes.