Feasibility of functional precision medicine for guiding treatment of relapsed or refractory pediatric cancers

Children with rare, relapsed or refractory cancers often face limited treatment options, and few predictive biomarkers are available that can enable personalized treatment recommendations. The implementation of functional precision medicine (FPM), which combines genomic profiling with drug sensitivity testing (DST) of patient-derived tumor cells, has potential to identify treatment options when standard-of-care is exhausted. The goal of this prospective observational study was to generate FPM data for pediatric patients with relapsed or refractory cancer. The primary objective was to determine the feasibility of returning FPM-based treatment recommendations in real time to the FPM tumor board (FPMTB) within a clinically actionable timeframe (<4 weeks). The secondary objective was to assess clinical outcomes from patients enrolled in the study. Twenty-five patients with relapsed or refractory solid and hematological cancers were enrolled; 21 patients underwent DST and 20 also completed genomic profiling. Median turnaround times for DST and genomics were within 10 days and 27 days, respectively. Treatment recommendations were made for 19 patients (76%), of whom 14 received therapeutic interventions. Six patients received subsequent FPM-guided treatments. Among these patients, five (83%) experienced a greater than 1.3-fold improvement in progression-free survival associated with their FPM-guided therapy relative to their previous therapy, and demonstrated a significant increase in progression-free survival and objective response rate compared to those of eight non-guided patients. The findings from our proof-of-principle study illustrate the potential for FPM to positively impact clinical care for pediatric and adolescent patients with relapsed or refractory cancers and warrant further validation in large prospective studies. ClinicalTrials.gov registration: NCT03860376 .

Imaging neuroinflammation with TSPO: A new perspective on the cellular sources and subcellular localization

Translocator Protein 18 kDa (TSPO), previously named Peripheral Benzodiazepine Receptor, is a well-validated and widely used biomarker of neuroinflammation to assess diverse central nervous system (CNS) pathologies in preclinical and clinical studies. Many studies have shown that in animal models of human neurological and neurodegenerative disease and in the human condition, TSPO levels increase in the brain neuropil, and this increase is driven by infiltration of peripheral inflammatory cells and activation of glial cells. Therefore, a clear understanding of the dynamics of the cellular sources of the TSPO response is critically important in the interpretation of Positron Emission Tomography (PET) studies and for understanding the pathophysiology of CNS diseases. Within the normal brain compartment, there are tissues and cells such as the choroid plexus, ependymal cells of the lining of the ventricles, and vascular endothelial cells that also express TSPO at even higher levels than in glial cells. However, there is a paucity of knowledge if these cell types respond and increase TSPO in the diseased brain. These cells do provide a background signal that needs to be accounted for in TSPO-PET imaging studies. More recently, there are reports that TSPO may be expressed in neurons of the adult brain and TSPO expression may be increased by neuronal activity. Therefore, it is essential to study this topic with a great deal of detail, methodological rigor, and rule out alternative interpretations and imaging artifacts. High levels of TSPO are present in the outer mitochondrial membrane. Recent studies have provided evidence of its localization in other cellular compartments including the plasma membrane and perinuclear regions which may define functions that are different from that in mitochondria. A greater understanding of the TSPO subcellular localization in glial cells and infiltrating peripheral immune cells and associated function(s) may provide an additional layer of information to the understanding of TSPO neurobiology. This review is an effort to outline recent advances in understanding the cellular sources and subcellular localization of TSPO in brain cells and to examine remaining questions that require rigorous investigation.

The Translocator Protein (TSPO) Genetic Polymorphism A147T Is Associated with Worse Survival in Male Glioblastoma Patients

Simple Summary

The translocator protein 18 kDa (TSPO) gene is highly expressed in glioblastoma (GBM), the most common primary malignant brain tumor, which remains one of the most difficult tumors to treat. TSPO is located in the outer mitochondrial membrane and binds cholesterol through its C-terminal domain. One frequent single-nucleotide polymorphism (SNP) rs6971, which changes the alanine 147 into threonine (Ala147Thr), has been found in the C-terminal domain of the TSPO region and dramatically alters the affinity with which TSPO binds drug ligands. However, the potential association between the TSPO genetic variants and GBM clinical outcomes is not known. Here, we evaluated the effects of the Ala147Thr SNP localized in this TSPO region on biological, sex-specific, overall, and progression-free GBM survival. Our findings suggest an association between the TSPO rs6971 variant and adverse outcomes in male GBM patients but not in females. These findings also suggest that the TSPO rs6971 SNP could be used as a prognostic marker of survival in GBM patients.

Abstract

Glioblastoma (GBM) is the most common primary brain tumor in adults, with few available therapies and a five-year survival rate of 7.2%. Hence, strategies for improving GBM prognosis are urgently needed. The translocator protein 18kDa (TSPO) plays crucial roles in essential mitochondria-based physiological processes and is a validated biomarker of neuroinflammation, which is implicated in GBM progression. The TSPO gene has a germline single nucleotide polymorphism, rs6971, which is the most common SNP in the Caucasian population. High TSPO gene expression is associated with reduced survival in GBM patients; however, the relation between the most frequent TSPO genetic variant and GBM pathogenesis is not known. The present study retrospectively analyzed the correlation of the TSPO polymorphic variant rs6971 with overall and progression-free survival in GBM patients using three independent cohorts. TSPO rs6971 polymorphism was significantly associated with shorter overall survival and progression-free survival in male GBM patients but not in females in one large cohort of 441 patients. We observed similar trends in two other independent cohorts. These observations suggest that the TSPO rs6971 polymorphism could be a significant predictor of poor prognosis in GBM, with a potential for use as a prognosis biomarker in GBM patients. These results reveal for the first time a biological sex-specific relation between rs6971 TSPO polymorphism and GBM.

Surface translocator protein 18 kDa (TSPO) localization on immune cells upon stimulation with LPS and in ART-treated HIV+ subjects

Translocator protein 18 kDa (TSPO) is a well-known outer mitochondrial membrane protein and it is widely used as a biomarker of neuroinflammation and brain injury. Although it is thought that TSPO plays key roles in a multitude of host cell functions, including steroid biosynthesis, apoptosis, generation of reactive oxygen species, and proliferation, some of these functions have recently been questioned. Here, we report the unexpected finding that circulating immune cells differentially express basal levels of TSPO on their cell surface, with a high percentage of monocytes and neutrophils expressing cell surface TSPO. In vitro stimulation of monocytes with LPS significantly increases the frequency of cells with surface TSPO expression in the absence of altered gene expression. Importantly, the LPS increase in TSPO cell surface expression in monocytes appears to be selective for LPS because two other distinct monocyte activators failed to increase the frequency of cells with surface TSPO. Finally, when we quantified immune cell TSPO surface expression in antiretroviral therapy-treated HIV⁺ donors, a chronic inflammatory disease, we found significant increases in the frequency of TSPO surface localization, which could be pharmacologically suppressed with ∆⁹ -tetrahydrocannabinol. These findings suggest that cell surface TSPO in circulating leukocytes could serve as a peripheral blood-based biomarker of inflammation.

A Novel Interaction of Translocator Protein 18 kDa (TSPO) with NADPH Oxidase in Microglia

In the brain neuropil, translocator protein 18 kDa (TSPO) is a stress response protein that is upregulated in microglia and astrocytes in diverse central nervous system pathologies. TSPO is widely used as a biomarker of neuroinflammation in preclinical and clinical neuroimaging studies. However, there is a paucity of knowledge on the function(s) of TSPO in glial cells. In this study, we explored a putative interaction between TSPO and NADPH oxidase 2 (NOX2) in microglia. We found that TSPO associates with gp91^phox and p22^phox, the principal subunits of NOX2 in primary murine microglia. The association of TSPO with gp91^phox and p22^phox was observed using co-immunoprecipitation, confocal immunofluorescence imaging, and proximity ligation assay. We found that besides gp91^phox and p22^phox, voltage-dependent anion channel (VDAC) also co-immunoprecipitated with TSPO consistent with previous reports. When we compared lipopolysaccharide (LPS) stimulated microglia to vehicle control, we found that a lower amount of gp91^phox and p22^phox protein co-immunoprecipitated with TSPO suggesting a disruption of the TSPO-NOX2 subunits association. TSPO immuno-gold electron microscopy confirmed that TSPO is present in the outer mitochondrial membrane but it is also found in the endoplasmic reticulum (ER), mitochondria-associated ER membrane (MAM), and in the plasma membrane. TSPO localization at the MAM may represent a subcellular site where TSPO interacts with gp91^phox and p22^phox since the MAM is a point of communication between outer mitochondria membrane proteins (TSPO) and ER proteins (gp91^phox and p22^phox) where they mature and form the cytochrome b₅₅₈ (Cytb₅₅₈) heterodimer. We also found that an acute burst of reactive oxygen species (ROS) increased TSPO levels on the surface of microglia and this effect was abrogated by a ROS scavenger. These results suggest that ROS production may alter the subcellular distribution of TSPO. Collectively, our findings suggest that in microglia, TSPO is associated with the major NOX2 subunits gp91^phox and p22^phox. We hypothesize that this interaction may regulate Cytb₅₅₈ formation and modulate NOX2 levels, ROS production, and redox homeostasis in microglia.

Ovarian Cancer Treatment Stratification Using Ex Vivo Drug Sensitivity Testing

BACKGROUND

Treatment options for patients with platinum-resistant ovarian cancer are generally palliative in nature and rarely have realistic potential to be curative. Because many patients with recurrent ovarian cancer receive aggressive chemotherapy for prolonged periods, sometimes continuously, therapy-related toxicities are a major factor in treatment decisions. The use of ex vivo drug sensitivity screens has the potential to improve the treatment of patients with platinum-resistant ovarian cancer by providing personalized treatment plans and thus reducing toxicity from unproductive therapy attempts.

MATERIALS AND METHODS

We evaluated the treatment responses of a set of six early-passage patient-derived ovarian cancer cell lines towards a set of 30 Food and Drug Administration-approved chemotherapy drugs using drug-sensitivity testing.

RESULTS

We observed a wide range of treatment responses of the cell lines. While most compounds displayed vastly different treatment responses between cell lines, we found that some compounds such as docetaxel and cephalomannine reduced cell survival of all cell lines.

CONCLUSION

We propose that ex vivo drug-sensitivity screening holds the potential to greatly improve patient outcomes, especially in a population where multiple continuous treatments are not an option due to advanced disease, rapid disease progression, age or poor overall health. This approach may also be useful to identify potential novel therapeutics for patients with ovarian cancer.

Dual Src and MEK Inhibition Decreases Ovarian Cancer Growth and Targets Tumor Initiating Stem-Like Cells

Purpose: Rational targeted therapies are needed for treatment of ovarian cancers. Signaling kinases Src and MAPK are activated in high-grade serous ovarian cancer (HGSOC). Here, we tested the frequency of activation of both kinases in HGSOC and the therapeutic potential of dual kinase inhibition.Experimental Design: MEK and Src activation was assayed in primary HGSOC from The Cancer Genome Atlas (TGGA). Effects of dual kinase inhibition were assayed on cell-cycle, apoptosis, gene, and proteomic analysis; cancer stem cells; and xenografts.Results: Both Src and MAPK are coactivated in 31% of HGSOC, and this associates with worse overall survival on multivariate analysis. Frequent dual kinase activation in HGSOC led us to assay the efficacy of combined Src and MEK inhibition. Treatment of established lines and primary ovarian cancer cultures with Src and MEK inhibitors saracatinib and selumetinib, respectively, showed target kinase inhibition and synergistic induction of apoptosis and cell-cycle arrest in vitro, and tumor inhibition in xenografts. Gene expression and proteomic analysis confirmed cell-cycle inhibition and autophagy. Dual therapy also potently inhibited tumor-initiating cells. Src and MAPK were both activated in tumor-initiating populations. Combination treatment followed by drug washout decreased sphere formation and ALDH1⁺ cells. In vivo, tumors dissociated after dual therapy showed a marked decrease in ALDH1 staining, sphere formation, and loss of tumor-initiating cells upon serial xenografting.Conclusions: Selumetinib added to saracatinib overcomes EGFR/HER2/ERBB2-mediated bypass activation of MEK/MAPK observed with saracatinib alone and targets tumor-initiating ovarian cancer populations, supporting further evaluation of combined Src-MEK inhibition in clinical trials. Clin Cancer Res; 24(19); 4874-86. ©2018 AACR.

Abstract P5-07-13: Identification of a cancer stem sell-specific function for the histone deacetylases, HDAC1 and HDAC7, in breast and ovarian cancer

This abstract was withdrawn by the authors.

A New Role for ERα: Silencing via DNA Methylation of Basal, Stem Cell, and EMT Genes

Resistance to hormonal therapies is a major clinical problem in the treatment of estrogen receptor α-positive (ERα⁺) breast cancers. Epigenetic marks, namely DNA methylation of cytosine at specific CpG sites (5mCpG), are frequently associated with ERα⁺ status in human breast cancers. Therefore, ERα may regulate gene expression in part via DNA methylation. This hypothesis was evaluated using a panel of breast cancer cell line models of antiestrogen resistance. Microarray gene expression profiling was used to identify genes normally silenced in ERα⁺ cells but derepressed upon exposure to the demethylating agent decitabine, derepressed upon long-term loss of ERα expression, and resuppressed by gain of ERα activity/expression. ERα-dependent DNA methylation targets (n = 39) were enriched for ERα-binding sites, basal-up/luminal-down markers, cancer stem cell, epithelial-mesenchymal transition, and inflammatory and tumor suppressor genes. Kaplan-Meier survival curve and Cox proportional hazards regression analyses indicated that these targets predicted poor distant metastasis-free survival among a large cohort of breast cancer patients. The basal breast cancer subtype markers LCN2 and IFI27 showed the greatest inverse relationship with ERα expression/activity and contain ERα-binding sites. Thus, genes that are methylated in an ERα-dependent manner may serve as predictive biomarkers in breast cancer.

IMPLICATIONS

ERα directs DNA methylation-mediated silencing of specific genes that have biomarker potential in breast cancer subtypes. Mol Cancer Res; 15(2); 152-64. ©2016 AACR.

Interactions between Adipocytes and Breast Cancer Cells Stimulate Cytokine Production and Drive Src/Sox2/miR-302b-Mediated Malignant Progression

Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. Obesity is a risk factor for many cancers, but the mechanisms by which it contributes to cancer development and patient outcome have yet to be fully elucidated. Here, we examined the effects of coculturing human-derived adipocytes with established and primary breast cancer cells on tumorigenic potential. We found that the interaction between adipocytes and cancer cells increased the secretion of proinflammatory cytokines. Prolonged culture of cancer cells with adipocytes or cytokines increased the proportion of mammosphere-forming cells and of cells expressing stem-like markers in vitro. Furthermore, contact with immature adipocytes increased the abundance of cancer cells with tumor-forming and metastatic potential in vivo. Mechanistic investigations demonstrated that cancer cells cultured with immature adipocytes or cytokines activated Src, thus promoting Sox2, c-Myc, and Nanog upregulation. Moreover, Sox2-dependent induction of miR-302b further stimulated cMYC and SOX2 expression and potentiated the cytokine-induced cancer stem cell-like properties. Finally, we found that Src inhibitors decreased cytokine production after coculture, indicating that Src is not only activated by adipocyte or cytokine exposures, but is also required to sustain cytokine induction. These data support a model in which cancer cell invasion into local fat would establish feed-forward loops to activate Src, maintain proinflammatory cytokine production, and increase tumor-initiating cell abundance and metastatic progression. Collectively, our findings reveal new insights underlying increased breast cancer mortality in obese individuals and provide a novel preclinical rationale to test the efficacy of Src inhibitors for breast cancer treatment.

Triple negative breast cancer initiating cell subsets differ in functional and molecular characteristics and in γ-secretase inhibitor drug responses

Increasing evidence suggests that stem-like cells mediate cancer therapy resistance and metastasis. Breast tumour-initiating stem cells (T-ISC) are known to be enriched in CD44⁺CD24^neg/low cells. Here, we identify two T-ISC subsets within this population in triple negative breast cancer (TNBC) lines and dissociated primary breast cancer cultures: CD44⁺CD24^low+ subpopulation generates CD44⁺CD24^neg progeny with reduced sphere formation and tumourigenicity. CD44⁺CD24^low+ populations contain subsets of ALDH1⁺ and ESA⁺ cells, yield more frequent spheres and/or T-ISC in limiting dilution assays, preferentially express metastatic gene signatures and show greater motility, invasion and, in the MDA-MB-231 model, metastatic potential. CD44⁺CD24^low+ but not CD44⁺CD24^neg express activated Notch1 intracellular domain (N1-ICD) and Notch target genes. We show N1-ICD transactivates SOX2 to increase sphere formation, ALDH1+ and CD44⁺CD24^low+cells. Gamma secretase inhibitors (GSI) reduced sphere formation and xenograft growth from CD44⁺CD24^low+ cells, but CD44⁺CD24^neg were resistant. While GSI hold promise for targeting T-ISC, stem cell heterogeneity as observed herein, could limit GSI efficacy. These data suggest a breast T-ISC hierarchy in which distinct pathways drive developmentally related subpopulations with different anti-cancer drug responsiveness.

Abstract 3478: CD44+CD24low+ progenitors in ER negative breast cancer have higher Notch1 activation, self-renewal, and chemo resistance and generate CD44+CD24neg cells and tumors that metastasize

CD44 surface expression is associated with self renewal in several cancers. While CD44+/CD24neg/low/ESA+ breast cancer subpopulations are enriched for cancer stem cells (CSC), the relative contributions of CD24 negative versus low subpopulations to stemness and metastasis is poorly defined. Here we show that CD44+/CD24low+ CSC give rise to CD44+/CD24neg progeny with reduced tumorigenicity and altered drug sensitivities. CD44+/CD24low+ subpopulations in MDA-MB-231 and in primary dissociated ER negative breast cancers show greater sphere and soft agar colony formation, Notch1 activation, Sox2 and Nanog expression and chemo resistance compared to CD44+/CD24neg. CD44+/CD24low+ can self-renew and give rise to CD44+/CD24neg cells, while CD44+/CD24neg progeny are exclusively CD44+/CD24neg. Tumorigenicity was increased and metastasis arose exclusively from orthotopic CD44+CD24low+ xenografts. CD44+/CD24low+ had greater expression of metastasis- and embryonic stem cell- associated and Notch pathway activated genes than CD44+/CD24neg cells. Moreover, MDA-MB-231 cells overexpressing Notch1 intracellular domain (N1-ICD) had higher Sox2 expression, and higher indices of CSC self-renewal (higher % CD44+/CD24low+, ALDH1 activity, sphere and soft agar colony formation), all of which were abrogated by Sox2 knockdown. Gamma secretase inhibition reduced ES-TFs and self-renewal in CD44+CD24low+ progenitors, but had no effect on proliferation or survival of CD44+CD24neg cells supporting further clinical development of Notch targeting drugs for cancer treatment in humans. Thus, CD44+CD24low+ and CD44+CD24neg CSC in ER negative breast cancer have distinct properties. CD44+CD24low+ can self-renew and generate CD44+CD24neg progeny. Orthotopic xenograft CD44+CD24low+ tumors arose with reduced latency with higher frequent, were larger, and the sole source of metastasis. Notch1 activation of Sox2 drives CD44+CD24low+ self-renewal and is blocked by GSI providing a strong rationale for use of GSI as CSC targeting agents in ER negative breast cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3478. doi:1538-7445.AM2012-3478

Abstract 2392: Primary cultures established from estrogen receptor negative breast tumors: Method and characterization

Approximately 35% of breast cancers lack expression of estrogen receptor (ER) protein. ER-negative (ER-) breast cancer carries a worse prognosis than ER positive (ER+) breast cancer, but more importantly, it precludes use of less toxic endocrine therapies. Our objective was to establish primary cultures from dissociation of ER- breast tumors in order to provide an alternative cellular model that can be used as a valuable tool for both in vitro and in vivo studies of ER- breast cancer. A total of eight ER- tumors were successfully dissociated into primary cultures: four from ER-/PR-/H2N- and four from ER-/PR-/H2N+ primary breast tumors with a 100% success rate. The epithelial-enriched cell pellet was placed in culture and for experiments carried for a maximum of 30 passages. These cells will be hereafter referred to as “dissociated tumor” (DT) cultures. Cells were grown in 2D culture and their in vitro morphology, proliferation rates, mammosphere and soft agar colony formation ability, and CD44/CD24 surface marker expression (tumor initiating cell (TIC) content) are determined. In addition we have performed gene expression profiling and established their tumorigenic potential in NOD/SCID female mice. Each culture exhibited its own relatively unique morphology; two of the eight cultures grew mainly as suspensions while the remaining six DT cultures grew with a higher percentage of attached, mesenchymal phenotype cells. Proliferation rates ranged from 38 to 60 hours, and while all of the DT cultures had the ability to form mammospheres, five of the eight DTs (DT13, DT16, DT22, DT25 and DT28) formed colonies in soft agar. Analysis of CD44 and CD24 surface markers expression showed that while all DT cultures were CD44 positive, expression of CD24 varied among DTs. Of the eight DT cultures, we found five of them to have a high (&gt;85%) CD44+/CD24-/lo cell content, one the CD44+/CD24high phenotype and two of eight have populations with increasing levels of CD24 expression ranging from -/lo to medium. This CD44+/CD24-/lo phenotype is stable when examined over several passages. Microarray analysis comparing the DT cultures to cancer cell lines showed that they clustered with each other and with several breast cancer cell lines of known ER- status and EGFR or Her2 overexpression status. In agreement with the soft agar assay, DT16, DT22, DT25 and DT28 had the ability to form tumors when injected into the mammary fat pad of female NOD/SCID mice. In summary, our study describes primary cultures of dissociated ER negative breast cancer cells that provide an alternative, primary cell based model that allows both in vitro as well as in vivo experimental approaches. The use of these types of cellular models may lead to a better understanding of ER- breast cancer biology as well as being a valuable tool for screening potential therapeutic options for ER- breast cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2011-2392

Abstract 3335: Self-renewal, tumorigenicity and metastatic potential of CD44+ cells in ER-negative lines and dissociated primary human breast cancers is increased in CD24+ subsets

Primary human breast cancer subpopulations with a CD44+ CD24NEG/LOW ESA+ phenotype exhibit self-renewal and generate xenograft tumors with as few as 100 cells in immunodeficient mice. While CD44 expression is strongly associated with self renewal in several cancers, the relative contributions of CD24 negative versus low subpopulations to stemness is poorly defined. Early reports have not distinguished negative from low CD24 expression in human lines and primary tumors, and both, together with CD44+ status have been linked to breast cancer stem cell phenotypes. In contrast, certain reports have associated CD24 expression with tumor progression and metastasis. Here, we show increased mitogenic kinase activation, expression of ESC and EMT genes in the CD24LOW subpopulation of CD44+ cells in both triple negative MDA-MB-231 breast cancer cells and primary dissociated breast cancers (DTs) compared to the CD24NEG cells. Moreover, tumorigenicity was increased and metastasis arose exclusively from orthotopic xeno-implantation of the CD44+CD24LOW cells. MDA-MB-231 and two different primary DTs were live sorted into CD44+CD24NEG and CD44+CD24LOW enriched subpopulations. Cells expressing other putative stem cell markers, ALDH1 and ESA were almost entirely CD44+CD24LOW. CD44+CD24LOWcells showed higher PI3-kinase/Akt, MAPK, and Src activites compared to CD44+ CD24NEG cells. While both subpopulations formed soft agar colonies and/or mammospheres, those arising from CD44+CD24LOW were greater in number and size than from CD44+CD24NEG cells. When cultured in 2D after sorting, CD44+ CD24LOW cells gave rise to both CD44+ CD24LOW and CD44+ CD24NEG progeny while CD44+ CD24NEG yielded only CD44+ CD24NEG progeny. CD44+CD24LOW expressed higher levels of ESC genes and EMT-associated genes than CD44+CD24NEG cells and uniquely expressed stem cell-associated miRNAs. On orthotopic injection into BalbC nude mice, both subpopulations initiated tumors with as few as 100 cells, however tumors arising from CD44+CD24LOW cells had a shorter latency and grew more rapidly than those arising from CD44+CD24NEG cells. In vivo imaging of luciferase positive cells showed CD44+CD24LOW cells yield metastasis while CD44+CD24NEG cells did not.

Our data demonstrate, for the first time, distinct biological properties between the CD44+CD24LOW and CD44+CD24NEG enriched subpopulations of MDA-MB-231 and primary human breast cancer DTs. Low surface expression of CD24 is associated with ALDH1 and ESA+ status, increased self-renewal as shown by mammosphere and colony formation, tumorigenicity and metastatic potential of CD44+ cells. The ability to isolate and characterize such TSC-enriched subpopulations will be necessary for development of therapeutic strategies that preferentially target breast cancer stem cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3335. doi:10.1158/1538-7445.AM2011-3335

High-performance liquid chromatography method for quantifying sphingomyelin in rat brain

A rapid, reproducible and accurate high-performance liquid chromatographic (HPLC) method for the quantitative determination of sphingomyelin in rat brain was developed and validated using normal-phase silica gel column, acetonitrile-methanol-water (65:18:17 (v/v)) at a flow rate of 1 ml/min, isocratic elution, UV detection at 207 nm and 1,2-dimyristoyl-sn-glycero-3-phosphocholine as an internal standard. Total run time was 10.0 min. The calibration curve was linear over the range of 0.025-0.4 mg/ml sphingomyelin (R2>0.99). The intra-day coefficient of variation ranged from 1.4% to 2.2%. The average inter-day coefficient of variation over a period of 4 days was 3.1%. The practical limit of detection was 0.005 mg/ml with a quantification limit of 0.01 mg/ml.