Brain metastases are among the most feared complications in breast cancer, as no therapy exists that prevents or eliminates breast cancer spreading to the brain. New therapeutic strategies depend on specific knowledge of tumor cell properties that allow breast cancer cell growth within the brain tissue. To provide information in this direction, we established a human breast cancer cell model for brain metastasis based on circulating tumor cells from a breast cancer patient and variants of these cells derived from bone or brain lesions in immunodeficient mice. The brain-derived cells showed an increased potential for brain metastasis in vivo and exhibited a unique protein expression profile identified by large-scale proteomic analysis. This protein profile is consistent with either a selection of predisposed cells or bioenergetic adaptation of the tumor cells to the unique energy metabolism of the brain. Increased expression of enzymes involved in glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation pathways suggests that the brain metastatic cells derive energy from glucose oxidation. The cells further showed enhanced activation of the pentose phosphate pathway and the glutathione system, which can minimize production of reactive oxygen species resulting from an enhanced oxidative metabolism. These changes promoted resistance of brain metastatic cells to drugs that affect the cellular redox balance. Importantly, the metabolic alterations are associated with strongly enhanced tumor cell survival and proliferation in the brain microenvironment. Thus, our data support the hypothesis that predisposition or adaptation of the tumor cell energy metabolism is a key element in breast cancer brain metastasis, and raise the possibility of targeting the functional differentiation in breast cancer brain lesions as a novel therapeutic strategy. [Cancer Res 2007;67(4):1472-86]

- Awareness of the gold standard paradox is necessary when using traditional pathologist scores to analytically validate a tIA tool because image analysis is used specifically to overcome known sources of bias in visual assessment of tissue sections.

We have shown that ER-negative and invasive human breast cancer cell lines MDA-MB-468 and MDA-MB-231 have constitutively higher mitogen activated protein kinase (ERK1&2/MAPK) when compared to the ERpositive and non-invasive MCF-7 human breast cancer cells. In MCF-7 cells, TGFa stimulation induced only transient MAPK activation, leading to a transient increase in cell migration. However, MDA 231 and MDA 468 cells, TGFa stimulation induced sustained MAPK activation, which correlated with enhanced cell motility and in vitro invasion. Serum stimulation activates ERK/MAPK activity persistently in both ER-positive and ER-negative breast cancer cells, leading to enhanced and sustained cell migration. Inhibition of MAPK activation by anti-sense MEK expression in MDA-MB-468 cells signi®cantly inhibits cell migration and in vitro invasion. In contrast, MCF-7 cells expressing constitutively activated MEK show a signi®cant increase in MAPK activity and cell migration, but this failed to enhance in vitro invasion. The kinetic pro®les of MAPK activation and inhibition show a relationship between the duration and magnitude of MAPK activation and cell migration in both ER-positive and ER-negative human breast cancer cells. These studies show that cell motility is modulated by the magnitude and the duration of MAPK activation; but increased activation of MAPK may not be su cient to allow in vitro invasion in noninvasive MCF-7 breast cancer cells. Oncogene (2001) 20, 4209 ± 4218.

The incidence of brain metastasis is rising and poses a severe clinical problem, as we lack effective therapies and knowledge of mechanisms that control metastatic growth in the brain. Here we demonstrate a crucial role for high-affinity tumor cell integrin ␣v␤3 in brain metastatic growth and recruitment of blood vessels. Although ␣v␤3 is frequently up-regulated in primary brain tumors and metastatic lesions of brain homing cancers, we show that it is the ␣v␤3 activation state that is critical for brain lesion growth. Activated, but not non-activated, tumor cell ␣v␤3 supports efficient brain metastatic growth through continuous up-regulation of vascular endothelial growth factor (VEGF) protein under normoxic conditions. In metastatic brain lesions carrying activated ␣v␤3, VEGF expression is controlled at the post-transcriptional level and involves phosphorylation and inhibition of translational respressor 4E-binding protein (4E-BP1). In contrast, tumor cells with nonactivated ␣v␤3 depend on hypoxia for VEGF induction, resulting in reduced angiogenesis, tumor cell apoptosis, and inefficient intracranial growth. Importantly, the microenvironment critically influences the effects that activated tumor cell ␣v␤3 exerts on tumor cell growth. Although it strongly promoted intracranial growth, the activation state of the receptor did not influence tumor growth in the mammary fat pad as a primary site. Thus, we identified a mechanism by which metastatic cells thrive in the brain microenvironment and use the high-affinity form of an adhesion receptor to grow and secure host support for proliferation. Targeting this molecular mechanism could prove valuable for the inhibition of brain metastasis.angiogenesis ͉ brain metastasis ͉ integrin activation ͉ 4E-BP1 B rain metastases are diagnosed in 10% to 40% of patients with progressing cancer, and the incidence is rising as patients live longer and extracranial metastases respond to improved treatments. However, brain metastases still cannot be treated effectively, and mechanisms controlling brain metastatic growth are largely unknown (1-3).Here, we demonstrate that the high-affinity state of tumor cell adhesion receptor integrin ␣ v ␤ 3 critically promotes metastatic growth and recruitment of supporting blood vessels within the brain microenvironment. Integrins are cell surface receptors composed of non-covalently linked ␣ and ␤ subunits that mediate cell-matrix and cell-cell interactions and transduce signals that have impacts on cell survival, proliferation, adhesion, migration, and invasion. Integrin signals can also originate inside cells, affect receptor affinity, and thereby control ligand binding, cross talk with other receptors, and alter cell adhesion and proliferation (4-6). Integrin ␣ v ␤ 3 also plays a role on sprouting endothelial cells and contributes to angiogenesis (7). In several tumor types, including glioma, breast cancer, and melanoma, expression of ␣ v ␤ 3 supports invasion and metastasis (8-11). Notably, these tumors either originate in the brain or freque...

Quantitative clinical measurement of heterogeneity in immunohistochemistry staining would be useful in evaluating patient therapeutic response and in identifying underlying issues in histopathology laboratory quality control. A heterogeneity scoring approach (HetMap) was designed to visualize a individual patient's immunohistochemistry heterogeneity in the context of a patient population. HER2 semiquantitative analysis was combined with ecology diversity statistics to evaluate cell-level heterogeneity (consistency of protein expression within neighboring cells in a tumor nest) and tumor-level heterogeneity (differences of protein expression across a tumor as represented by a tissue section). This approach was evaluated on HER2 immunohistochemistry-stained breast cancer samples using 200 specimens across two different laboratories with three pathologists per laboratory, each outlining regions of tumor for scoring by automatic cell-based image analysis. HetMap was evaluated using three different scoring schemes: HER2 scoring according to American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) guidelines, H-score, and a new continuous HER2 score (HER2 cont ). Two definitions of heterogeneity, cell-level and tumor-level, provided useful independent measures of heterogeneity. Cases where pathologists had disagreement over reads in the area of clinical importance ( þ 1 and þ 2) had statistically significantly higher levels of tumor-level heterogeneity. Cell-level heterogeneity, reported either as an average or the maximum area of heterogeneity across a slide, had low levels of dependency on the pathologist choice of region, while tumor-level heterogeneity measurements had more dependence on the pathologist choice of regions. HetMap is a measure of heterogeneity, by which pathologists, oncologists, and drug development organizations can view cell-level and tumor-level heterogeneity for a patient for a given marker in the context of an entire patient cohort. Heterogeneity analysis can be used to identify tumors with differing degrees of heterogeneity, or to highlight slides that should be rechecked for QC issues. Tumor heterogeneity plays a significant role in disconcordant reads between pathologists.

The estrogen receptor alpha (ERa) signaling plays an essential role in breast cancer progression and endocrine therapy. Mitogen-activated protein kinase (MAPK/ Erk1/2) has been implicated in ligand-independent activation of ER, resulting in the cross-talk between growth factor and ER mediated signaling. In this study, we examined the e ect of the cross-talk on estradiol (E 2 )-mediated signaling, tumor growth and its e ect on anti-estrogen therapy. Our ®ndings demonstrate that expression of constitutively activated mitogen activated kinase kinase (MEK1), an immediate upstream activator of MAPK in estrogen receptor positive MCF-7 breast cancer cells (MEK/MCF-7), showed an increase in ERadriven transcriptional activation. In MEK/MCF-7 cells maximal transactivation levels were achieved in response to treatment with much lower E 2 concentrations (10 710 M E 2 ) when compared to MCF-7 control cells (10 78 M E 2 ). Furthermore, we have seen an increased association between ERa and its nuclear coactivators AIB1 or TIF-2, in MEK/MCF-7 cells relative to those seen in MCF-7 control cells. In addition, in vivo studies show that MEK/ MCF-7 cell tumors are *threefold larger than those of MCF-7 cell, in the presence of E 2 . Immunohistochemical staining demonstrates that progesterone receptor (PR) and pS2, two E 2 -regulated gene products, are signi®-cantly increased in MEK/MCF-7 cell tumors compared to those of MCF-7 control tumors, suggesting that activation of ERa by MAPK enhances the expression of E 2 -regulated genes and accelerates tumor growth. Remarkably, the antiestrogens tamoxifen and ICI 182,780, were shown both in vitro and in vivo studies to e ciently antagonize the stimulatory e ects of E 2 on ER regulated transactivation and tumor growth in MEK/ MCF-7 as well as MCF-7 cell lines. Taken together, these data suggest that MAPK/ER cross-talk enhances ERa-mediated signaling and accelerates E 2 -dependent tumor growth without diminishing sensitivity to the inhibitory e ects of anti-estrogens.

Cell cycle progression is dependent on the nuclear localization and transcriptional effects of activated extracellular signal-regulated kinase (ERK)1 and ERK2 mitogen-activated protein (MAP) kinases (ERK1/2). Phosphoprotein enriched in astrocytes (PEA-15) binds ERK1/2 and inhibits their nuclear localization, thus blocking cell proliferation. Here, we report that phosphorylation of PEA-15 blocks its interaction with ERK1/2 in vitro and in vivo and that phosphorylation of both Ser 104 and Ser 116 is required for this effect. Using phosphomimetic and nonphosphorylatable mutants of PEA-15, we found that PEA-15 phosphorylation abrogates its capacity to block the nuclear localization and transcriptional activities of ERK1/2; this phosphorylation therefore enables the proliferation of cells that express high levels of PEA-15. Additionally, we report that PEA-15 phosphorylation can modulate nontranscriptional activities of ERK1/2, such as the modulation of the affinity of integrin adhesion receptors. Finally, we used a novel anti-phospho-specific PEA-15 antibody to establish that PEA-15 is phosphorylated in situ in normal mammary epithelium. These results define a novel posttranslational mechanism for controlling the subcellular localization of ERK1/2 and for specifying the output of MAP kinase signaling.

Phosphoprotein enriched in astrocytes of 15 kDa (PEA-15) binds to extracellular signal-regulated kinase 1 and 2 (ERK1/2) mitogen-activated protein (MAP) kinases to alter ERK1/2 cellular localization and target preferences and binds to adaptors in the extrinsic cell death pathway to block apoptosis. Here, we report that PEA-15 protein expression is inversely correlated with the invasive behavior of breast cancer in an immunohistochemical analysis of a breast cancer progression tissue microarray. Short hairpin RNA-mediated inhibition of PEA-15 expression increased the invasion of PEA-15-expressing tumor cells in vitro, suggesting a causative role for PEA-15 in the inhibition of invasion. This causative role was confirmed by the finding that the enforced expression of PEA-15 in invasive tumor cells reduced invasion. The effect of PEA-15 on tumor invasion is mediated by its interaction with ERK1/2 as shown by the following: (a) PEA-15 mutants that fail to bind ERK1/2 did not inhibit invasion; (b) overexpression of ERK1 or activated MAP/ERK kinase (MEK) reversed the inhibitory effect of PEA-15; (c) when an inhibitor of ERK1/2 activation reduced invasion, PEA-15 expression did not significantly reduce invasion further. Furthermore, we find that the effect of PEA-15 on invasion seems to relate to the nuclear localization of activated ERK1/2. PEA-15 inhibits invasion by keeping ERK out of the nucleus, as a PEA-15 mutant that cannot prevent ERK nuclear localization was not able to inhibit invasion. In addition, membrane-localized ERK1, which sequesters endogenous ERK1 to prevent its nuclear localization, also inhibited invasion. These results reveal that PEA-15 regulates cancer cell invasion via its ability to bind ERK1/2 and indicate that nuclear entry of ERK1/2 is important in tumor behavior. [Cancer Res 2007;67(4):1536-44]