Hui Wu

Involvement of miR-326 in chemotherapy resistance of breast cancer through modulating expression of multidrug resistance-associated protein 1

Multidrug resistance-associated protein (MRP-1/ABCC1) transports a wide range of therapeutic agents and may play a critical role in the development of multidrug resistance (MDR) in tumor cells. However, the regulation of MRP-1 remains controversial. To explore whether miRNAs are involved in the regulation of MRP-1 expression and modulate the sensitivity of tumor cells to chemotherapeutic agents, we analyzed miRNA expression levels in VP-16-resistant MDR cell line, MCF-7/VP, in comparison with its parent cell line, MCF-7, using a miRNA microarray. MCF-7/VP overexpressed MRP-1 mRNA and protein not MDR-1 and BCRP. miR-326 was downregulated in MCF-7/VP compared to MCF-7. Additionally, miR-326 was downregulated in a panel of advanced breast cancer tissues and consistent reversely with expression levels of MRP-1. Furthermore, the elevated levels of miR-326 in the mimics-transfected VP-16-resistant cell line, MCF-7/VP, downregulated MRP-1 expression and sensitized these cells to VP-16 and doxorubicin. These findings demonstrate for the first time the involvement of miRNAs in multidrug resistance mediated by MRP-1 and suggest that miR-326 may be an efficient agent for preventing and reversing MDR in tumor cells.

Potential Biomarker of L-type Amino Acid Transporter 1 in Breast Cancer Progression

PurposeL-type amino acid transporter 1 (LAT1) is essential for the transport of large neutral amino acids. However, its role in breast cancer growth remains largely unknown. The purpose of the study is to investigate whether LAT1 is a potential biomarker for the diagnosis and treatment of breast cancer.MethodsLAT1 mRNA and protein levels in breast cancer cell lines and tissues were analyzed. In addition, the effects of targeting LAT1 for the inhibition of breast cancer cell tumorigenesis were assessed with soft agar assay. The imaging of xenograft with anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid (anti-[18F]FACBC) PET was assessed for its diagnostic biomarker potential.ResultsNormal breast tissue or low malignant cell lines expressed low levels of LAT1 mRNA and protein, while highly malignant cancer cell lines and high-grade breast cancer tissue expressed high levels of LAT1. In addition, higher expression levels of LAT1 in breast cancer tissues were consistent with advanced-stage breast cancer. Furthermore, the blockade of LAT1 with its inhibitor, 2-amino-bicyclo[2.2.1]heptane-2-carboxylic acid (BCH), or the knockdown of LAT1 with siRNA, inhibited proliferation and tumorigenesis of breast cancer cells. A leucine analog, anti-[18F]FACBC, has been demonstrated to be an excellent PET tracer for the non-invasive imaging of malignant breast cancer using an orthotopic animal model.ConclusionsThe overexpression of LAT1 is required for the progression of breast cancer. LAT1 represents a potential biomarker for therapy and diagnosis of breast cancer. Anti-[18F]FACBC that correlates with LAT1 function is a potential PET tracer for malignant breast tumor imaging.

Wnt-beta-catenin pathway signals metastasis-associated tumor cell phenotypes in triple negative breast cancers.

Tumor cells acquire metastasis-associated (MA) phenotypes following genetic alterations in them which cause deregulation of different signaling pathways. Earlier, we reported that an upregulation of the Wnt-beta-catenin pathway (WP) is one of the genetic salient features of triple-negative breast cancer (TNBC), and WP signaling is associated with metastasis in TNBC. Using cBioPortal, here we found that collective % of alteration(s) in WP genes, CTNNB1, APC and DVL1 among breast-invasive-carcinomas was 21% as compared to 56% in PAM50 Basal. To understand the functional relevance of WP in the biology of heterogeneous/metastasizing TNBC cells, we undertook this comprehensive study using 15 cell lines in which we examined the role of WP in the context of integrin-dependent MA-phenotypes. Directional movement of tumor cells was observed by confocal immunofluorescence microscopy and quantitative confocal-video-microscopy while matrigel-invasion was studied by MMP7-specific casein-zymography. WntC59, XAV939, sulindac sulfide and beta-catenin siRNA (1) inhibited fibronectin-directed migration, (2) decreased podia-parameters and motility-descriptors, (3) altered filamentous-actin, (4) decreased matrigel-invasion and (5) inhibited cell proliferation as well as 3D clonogenic growth. Sulindac sulfide and beta-catenin siRNA decreased beta-catenin/active-beta-catenin and MMP7. LWnt3ACM-stimulated proliferation, clonogenicity, fibronection-directed migration and matrigel-invasion were perturbed by WP-modulators, sulindac sulfide and GDC-0941. We studied a direct involvement of WP in metastasis by stimulating brain-metastasis-specific MDA-MB231BR cells to demonstrate that LWnt3ACM-stimulated proliferation, clonogenicity and migration were blocked following sulindac sulfide, GDC-0941 and beta-catenin knockdown. We present the first evidence showing a direct functional relationship between WP activation and integrin-dependent MA-phenotypes. By proving the functional relationship between WP activation and MA-phenotypes, our data mechanistically explains (1) why different components of WP are upregulated in TNBC, (2) how WP activation is associated with metastasis and (3) how integrin-dependent MA-phenotypes can be regulated by mitigating the WP.

Abstract 2240: Pre-clinical potency of INK128, a highly potent TORC1/2 kinase inhibitor in the HER2 amplified breast cancer model

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: The PI3K-AKT-mTOR pathway is commonly activated in breast cancers due to the amplification of receptor tyrosine kinase (HER2), the mutation of PIK3CA or the loss of expression/function of PTEN. About 20% of HER2+ breast cancer patients have PIK3CA mutation, which has resulted in a trend toward shorter progression-free survival with trastuzumab-based therapy. Resistance (intrinsic or acquired) to trastuzumab is a significant clinical challenge, partly due to the overriding activation of PI3K-AKT-mTOR pathway. The PI3K pathway activation leads to stimulation of the key growth and proliferation regulatory kinase, mTOR which can be blocked by allosteric inhibitors (rapalogous) or by ATP-comptetive mTOR kinase inhibitor (TORC1/2). Purpose: We investigated the effects of INK128; a potent and selective TORC1/2 kinase inhibitor alone or in conjunction with trastuzumab in HER2 amplified breast tumor cell lines. We also sought to identify the molecular response determinants of mTOR kinase inhibitor predicting potent activity in HER2+/trastuzumab-resistant cell lines. Experimental Design: Here, we used the HER2 amplified trastuzumab-sensitive breast tumor cell line (BT474), the trastuzumab-resistant breast tumor cell line (BT474HR) and HER2 amplified/PIK3CA mutated breast tumor cell lines (HCC1954, UACC893). Results: We demonstrate that 1) HER2+ cells are sensitive to INK128 (IC50 ∼40nM), 2) INK128 is also effective in trastuzumab-resistant and PIK3CA mutaed/HER2+ breast tumor cells (IC50 ∼20 and 20-30nM respectively), 3) INK128 is mechanistically distinct from rapalogous by a more potent and comprehensive inhibition of PI3K-AKT-mTOR signaling network: a) avoids S6K inhibition-mediated feedback activation of PI3K-AKT and b) abrogates 4EBP1 phosphorylation; 4) ligand-induced HIF1α accumulation is inhibited by prior treatment of INK128, and 5) the combination of trastuzumab plus INK128 more effectively blocked PI3K-AKT-mTOR signaling and HIF1α accumulation both in parental and trastuzumab-resistant cells. Conclusion: Our results suggest that i) therapeutic targeting of PI3K-AKT-mTOR signaling should be effective in abrogating resistance to trastuzumab therapy in HER2+ breast cancer, ii) combination of trastuzumab and INK128 is a promising treatment approach for HER2 overexpressed as well as trastuzumab-resistant breast cancer patients and iii) dual TORC1/2 inhibitor also mitigates the feedback activation of AKT caused by selective inhibition of mTORC1, and because of this, INK128 may yield greater therapeutic benefit in breast cancer patients. 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 2240. doi:1538-7445.AM2012-2240

Abstract 2227: P110 α-specific inhibitor is more suitable in PIK3CA mutated breast cancer model but ineffective in PTEN loss of function breast cancer model

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: Members of the phosphatidylinositiol 3-kinase (PI3K) pathway are frequently upregulated/amplified in broad range of cancers including breast cancer. The PIK3CA mutation or the loss-of-function of PTEN, which are found in different subsets of breast cancer, activates the PI3K-AKT-mTOR pathway, resulting in breast cancer development, progression and lower clinical benefit rate. Purpose: We investigated the comparison of inhibitory potency of p110α-specific inhibitor (INK1402) versus PI3K/mTOR dual inhibitor (BEZ235) in PI3K activated (define as activating mutation of PIK3CA or by loss-of-function of PTEN) hormone receptor positive (HR+) and triple negative (TN) breast tumor cells (a proof-of-concept study). Experimental Design: We used HR+ (MCF7, T47D and MDA-MB415) and TN (MDA-MB231 and MDA-MB468) breast cancer cell lines. We have tested the effects of INK1402 and BEZ235 on the, (a) cell survival/proliferation, (b) downstream signaling pathways for proliferation and (c) 3D ON-TOP-colony formation. Results: Here, we demonstrate that 1) both PIK3CA mutated and PTEN null or mutated breast cancer cells (ER+ and TN) are sensitive to BEZ235 (∼IC50 7 nM-30 nM), 2) only PIK3CA mutated cells (not PTEN loss-of-function cell lines) are sensitive to INK1402 (∼IC50 2 µM-12 µM), 3) anti-clonogenic growth property (3D-ON TOP colony formation assay) of INK1402 is more pronounced (80%-100%) in PIK3CA mutated cells as compared to PTEN loss-of-function cells (∼50%-60%), 4) BEZ235 shows anti-clonogenic property (3D-ON TOP colony formation assay) in all cell lines (∼60%-80%), 5) INK1402 and BEZ235 differentially inhibit PI3K-AKT-mTOR pathway and RAS-MAPK pathway in PIK3CA mutated, PTEN mutated (ER+), and PTEN null (TN) breast cancer cell lines: a) INK1402 is significantly more effective in PIK3CA mutated cell lines as compared to PTEN null or mutated cell lines, b) BEZ235 blocks the activation of PI3K-mTOR pathway components (p-AKT, p-S6RP) in both PIK3CA mutated and PTEN null or mutated cell lines, and c) interestingly, INK1402 blocks ERK activation in PIK3CA mutated cells whereas BEZ235 upregulates ERK activation in both PI3K mutated and PTEN null or mutated cell lines. Conclusion: These findings confirm the mutually exclusive behavior of PIK3CA mutation and PTEN loss in breast tumor models (Ellis MJ et al Cancer Research 2009; Russillo M et al JCO 2011). Our initial finding may provide a rationale to guide selection of patients who may benefit from PI3K-isoform (p110α)-specific inhibitor or PI3K/mTOR dual inhibitor therapy, and highlights the importance of accurately accessing the expression/functional status of PIK3CA or PTEN status in breast tumor samples. Acknowledgement: We sincerely thank to Novartis and Intellikine Inc for proving us with BEZ235 and INK1402 respectively. 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 2227. doi:1538-7445.AM2012-2227

Radiochemical Synthesis and Evaluation of 13N-Labeled 5-Aminolevulinic Acid for PET Imaging of Gliomas

The endogenous amino acid, 5-aminolevulinic acid (5-ALA), has received significant attention as an imaging agent, including ongoing clinical trials for image-guided tumor resection due to its selective uptake and subsequent accumulation of the fluorescent protoporphyrin IX in tumor cells. Based on the widely reported selectivity of 5-ALA, a new positron emission tomography imaging probe was developed by reacting methyl 5-bromolevulinate with [13N] ammonia. The radiotracer, [13N] 5-ALA, was produced in high radiochemical yield (65%) in 10 min and could be purified using only solid phase cartridges. In vivo testing in rats bearing intracranial 9L glioblastoma showed peak tumor uptake occurred within 10 min of radiotracer administration. Immunohistochemical staining and fluorescent imaging was used to confirm the tumor location and accumulation of the tracer seen from the PET images. The quick synthesis and rapid tumor specific uptake of [13N] 5-ALA makes it a potential novel clinical applicable radiotracer for detecting and monitoring tumors noninvasively.

Abstract 2230: Preclinical activity of INK128, a TORC1/2 inhibitor, in triple negative breast cancer: A combination of PARP inhibitor with PI3K-mTOR pathway-targeted inhibitor

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Introduction: Recent understanding of the biology of Triple Negative (TN) tumor cells has resulted in the recognition of following molecular targets for the development of novel therapeutics, (1) cell surface receptor tyrosine kinases (RTKs, e.g. EGFR, IGFR, c-MET, FGFR), (2) intracellular signaling pathway(s) (PI3K-AKT-mTOR, RAS-MAPK-ERK), and (3) DNA-damage (chemo- or radiotherapy) repair pathway. INK128 is an orally bioavailable, potent and selective ATP site kinase inhibitor of mTOR complexes TORC1 and TORC2 that together play a crucial role in regulating tumor cell growth, metabolism and motility. INK128 is structurally and mechanistically distinct from allosteric rapamycin-based mTOR inhibitors such as RAD001. Methods: We tested effects of INK128 (alone or in combination with carboplatin and ABT888) on, (a) cell survival/proliferation, (b) cell signaling marker(s) of proliferation, (c) fibronectin-mediated migration, (d) fibronectin-directed matrigel-invasion, and (e) clonogenic survival (3D-ON-TOP assay) in different TNBT cell lines with high expression of EGFR (MDA-MB468, SUM149), BRCA mutations (HCC1937, SUM149) no expression of PTEN protein (HCC70, HCC1937, MDA-MB468, SUM149), PIK3CA mutation (BT20) and RAS/RAF mutation (MDA-MB231). Results: Data showed that, (1) although the range of EC50s for INK128 varied from 50 nM-500 nM in different TNBT cells, the PTEN-null cells exhibited favorable EC50s compared to the rest of the cell lines (with exception to HCC1937), (2) inhibition of phosphorylation of AKT (S473), S6RP, and 4EBP1 was observed following INK128 treatment (100 nM and 200 nM) as early as 6 hours, (3) treatment with 200 nM INK128 for 24 hours differentially blocked pERK in PTEN-null MDA-MB468 as compared to MDA-MB231 cells, (4) INK128 treatment (100 nM) inhibited migration of different TNBT cells (as compared to 2 uM RAD001, allosteric, partial TORC1 inhibitor)) and the inhibition was differentially pronounced in PTEN-null TNBT cells lines, (5) INK128 treatment (100 nM) also blocked invasion of MDA-MB468 cells, and (6) INK128 dose-dependently blocked clonogenic growth of TNBT cells. This effect was potentiated in the presence of ABT888 (10uM; small molecule PARP inhibitor) plus carboplatin (10uM; chemotherapeutic agent). Conclusion: INK128 (alone or in combination with carboplatin and ABT888) has anti-proliferative effect on TNBT cells. INK128 has anti-migratory and anti-invasive effects on TNBT cells. Interestingly, the anti-migratory effect of INK128 was most prominent in PTEN-null TNBT cells. We are currently pursuing studies to test the effect of INK128 on the endothelial cells, the results of which will be presented in the meeting. 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 2230. doi:1538-7445.AM2012-2230

Abstract 2935: Anti-proliferative and pro-apoptotic effects of Olaparib, in triple negative subset of breast cancer: Does tumor suppressor PTEN play a role

Triple-negative breast tumors (TNBT) are associated with poor prognosis and high recurrence-rates after adjuvant therapy. Currently, there is no preferred standard form of chemotherapy for TNBT. Landmark studies on DNA damage checkpoints and associated repair function in preneoplastic and neoplastic cells have focused attention on the importance of the BRCA-RAD51 repair-pathway in the development and progression of TNBC. The PARP inhibitor (PARPi), Olaparib, is currently being tested in phase I / II trials in BC and holds promise for the treatment of BRCA-deficient basal-like and /or TNBC. PTEN protein/function is downregulated in ∼ 40% of breast cancer, including TNBT, and a recurrent gross-mutation of the PTEN gene is identified in breast cancer with deficient double-strand base-repair. We hypothesize that there is a cellular threshold for error-free DNA-repair in TNBT cells and that the absence of PTEN can sensitize these cells to a concurrent treatment of DNA-damaging agent (carboplatin) and PARPi (Olaparib). We determined: (a) the time course of expression of PAR protein following Olaparib in BRCA-incompetent TNBT cell lines, (b) enzymatic activity of PARPi in BRCA-competent MDA-MB-231(PTEN+), MDA468 (PTEN-null), and BT20, TNBT cells, (c) pro-apoptotic signals in both BRCA1-incompetent and BRCA1-competent TNBT cells, (d) anti-proliferative effect of Olaparib plus carboplatin on cell- survival (MTT assay, EC50s, automated live-cell counter), and 2D clonogenic assay. We have demonstrated: (1) a time dependent decrease in PAR expression with little alteration in the expression of total PARP within 24 hours of treatment of Olaparib in HCC1937 cells, (2) a comparable pattern of decrease in the levels of PAR expression in MDA-MB-231, MDA468, and BT20 cells following Olaparib and carboplatin at 24 and 48 hours, (3) a significant increase in the expression of cleaved-caspase 3 and 9, (4) a significant increase in the expression of cleaved-PARP, a downstream product of cleaved-caspase 3, (5) an increase in the TUNNEL-positive cells in response to Olaparib plus carboplatin and (6) a significant decrease in the percentage of cell-survival following combination-treatment. Strikingly, we found that amongst different BRCA-competent TNBT cells, PTEN-null MDA-MB468 cells appeared the most sensitive to the combination of Olaparib plus carboplatin with respect to EC50s, clonogenic assay, pro-apoptotic signals, and cell survival. Herein, we report a non-redundant function of PTEN in PARPi-mediated anti-proliferative and pro-apoptotic signals in TNBC. We are currently pursuing studies a) to delineate the mechanistic relationship between the thresholds of DNA repair and PTEN and b) to understand the phosphatase-independent role of PTEN in PARPi-mediated anti-proliferative / pro-apoptotic signals, the results of which will be presented in the meeting. 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 2935. doi:10.1158/1538-7445.AM2011-2935

P3-18-02: A Combination of Pathway-Targeted Inhibitor with DNA-Repair Inhibitor: Preclinical Efficacy of Zactima and Olaparib in Triple Negative Subset of Breast Cancer.

Introduction: Pathway-targeted therapy has not been established for the treatment of Triple Negative (TN) subset of breast cancer (BC). Despite emerging data supporting the use of polyADP-ribose polymerase (PARP) inhibitors, complete and durable responses are rare in TNBC and exploration of additional pathway-targeted therapies is needed. The high frequency (72-75%) of EGFR expression in TNBCs suggests that loss of BRCA1 may be coupled, either directly or indirectly, with EGFR overexpression in breast cancer ( Van der Groep et al., 2006) , and a recent report shows that even a partial loss of BRCA1 leads to an overall increase in EGFR expression in mammary epithelial cells ( Burga et al., 2011). We hypothesize that the combined inhibition of growth factor driven EGFR pathway (by Zactima, a small molecule kinase inhibitor of EGFR and VEGFR-2) and DNA-repair pathway (by Olaparib, PARP inhibitor) in the presence of DNA-damaging agent (carboplatin) will have anti-proliferative and anti-migratory effects on triple negative breast tumor (TNBT) cells. Methods : The effects of Zactima, Olaparib (single or in combination) and carboplatin were studied on: (a) the cell survival/proliferation (MTT, SRB, & cell titer-GLO assay), (b) EGF-induced upregulation of downstream proliferation markers, (c) the cellular signals for apoptosis, (d) fibronectin-directed migration (scratch-assay), (e) the vascular mimicry, and (f) the clonogenic survival (3D-ON-TOP assay) in different TNBT cell lines. Results : Our in vitro data show that, (1) Zactima (10 uM) blocked EGF-induced phosphorylation of AKT (S473 & T308), S6RP, 4EBP1 and ERK as early as 1 hr (after the treatment), (2) the range of EC50s for Zactima (96 hrs) varied from 5 uM −15 uM (HCC70, HCC1937, MDA-MB231, MDA-MB468, BT20), (3) EGFR over-expressing, PTEN-null, and ATM kinase mutated MDA-MB468 cell line exhibited lowest EC50 for Zactima as compared to other TNBT cell lines and was found to be the most sensitive cell line to Zactima (∼ 0.05 uM) when combined with 10 uM fixed dose of Olaparib, (4) a combination of Zactima with Olaparib plus carboplatin altered an adhesion-dependent cell-survival, increased caspase3 activity (expression of cleaved caspase3 and cleaved PARP) time dependently, inhibited vascular mimicry (at 6 and 24 hrs), blocked fibronectin-directed migration (scratch assay, 24 hrs), changed the organization of actin-cytoskeleton, and suppressed clonogenic growth in different TNBT cells lines. Conclusion : Zactima alone showed anti-proliferative/pro-apoptotic, and anti-migratory effects in TNBT cells. The combination of Zactima with Olaparib plus carboplatin was most effective in blocking the clonogenic growth of TNBT cells. We are currently pursuing studies to, (1) delineate the relationship between the anti-proliferative effects (clonogenic assay) of Zactima (alone or in combination) and the status of the EGFR/PI3K pathway using PIK3CA-mutated, PTEN-null and EGFR overexpressed TNBT cell lines, and (2) determine the effect of Zactima on angiogenesis using HUVEC cells, the results of which will be presented in the meeting. This work was generously supported by AVON foundation. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-18-02.

Abstract 2736: Overexpression of L-type amino acid transporter-1 in breast cancer cells and tissues: potential association with growth and progression of tumors

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC For a tumor to constantly proliferate, malignant cells require nutrients, especially glucose and amino acids. There is abundant evidence that tumor growth depends heavily on glucose uptake. The L-type amino acid transporter 1 (LAT1) is a major nutrient transport system responsible for the transport of large neutral essential amino acids. In the present study, we analyzed expression levels of LAT1 mRNA and protein with RT-PCR, Western blot and immunohistochemical staining. The results showed that normal breast tissues or low malignant cell lines expressed low levels of LAT1 mRNA and protein, while LAT1 was overexpressed in highly malignant cancer cell lines and high grade breast cancer tissues. In addition, we found higher expression levels of LAT1 in breast cancer tissues were consistent with high stages of breast cancer. Furthermore, we demonstrated that blockade of LAT1 with its inhibitor, 2-amino-bicyclo[2.2.1]heptane-2-carboxylic acid (BCH), or knockdown of LAT1 with transfection of specific siRNA inhibited proliferation of breast cancer cells. A variety of 11C- and 18F-labeled amino acids have been studied for potential use in positron emission tomography (PET) oncology. A non-natural, not-metabolizable leucine analog, anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid ([18F]FACBC), has shown superior tumor/normal brain ratio. We tested whether [18F]FACBC would also be an excellent PET tracer for malignant breast cancer imaging using an orthotopic breast cancer animal model and an experimental animal model of breast cancer metastasis. Our results support that [18F]FACBC could be a useful PET tracer for non-invasive imaging of breast cancer. These findings suggest that overexpression of LAT1 is necessary for proliferation of breast cancer cells and may contribute to progression of tumors. LAT1 may represent a potential target for diagnosis of breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2736.