Gain of glucose-independent growth upon metastasis of breast cancer cells to the brain

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

Metastases arising from tumors have the proclivity to colonize specific organs, suggesting that they must rewire their biology to meet the demands of the organ colonized, thus altering their primary properties. Each metastatic site presents distinct metabolic challenges to a colonizing cancer cell, ranging from fuel and oxygen availability to oxidative stress. Here, we discuss the organ-specific metabolic adaptations that cancer cells must undergo, which provide the ability to overcome the unique barriers to colonization in foreign tissues and establish the metastatic tissue tropism phenotype.

Targeting FBPase is an emerging novel approach for cancer therapy

Cancer is a leading cause of death in both developed and developing countries. Metabolic reprogramming is an emerging hallmark of cancer. Glucose homeostasis is reciprocally controlled by the catabolic glycolysis and anabolic gluconeogenesis pathways. Previous studies have mainly focused on catabolic glycolysis, but recently, FBPase, a rate-limiting enzyme in gluconeogenesis, was found to play critical roles in tumour initiation and progression in several cancer types. Here, we review recent ideas and discoveries that illustrate the clinical significance of FBPase expression in various cancers, the mechanism through which FBPase influences cancer, and the mechanism of FBPase silencing. Furthermore, we summarize some of the drugs targeting FBPase and discuss their potential use in clinical applications and the problems that remain unsolved.

Expression of glutamine metabolism-related proteins in thyroid cancer

PURPOSE

This study aimed to investigate the expression of glutamine metabolism-related protein in tumor and stromal compartments among the histologic subtypes of thyroid cancer.

RESULTS

GLS1 and GDH expression in tumor and stromal compartments were the highest in AC than in other subtypes. Tumoral ASCT2 expression was higher in MC but lower in FC (p < 0.001). In PTC, tumoral GLS1 and tumoral GDH expression was higher in the conventional type than in the follicular variant (p = 0.043 and 0.001, respectively), and in PTC with BRAF V600E mutation than in PTC without BRAF V600E mutation (p<0.001). Stromal GDH positivity was the independent factor associated with short overall survival (hazard ratio: 21.48, 95% confidence interval: 2.178-211.8, p = 0.009).

METHODS

We performed tissue microarrays with 557 thyroid cancer cases (papillary thyroid carcinoma [PTC]: 344, follicular carcinoma [FC]: 112, medullary carcinoma [MC]: 70, poorly differentiated carcinoma [PDC]: 23, and anaplastic carcinoma [AC]: 8) and 152 follicular adenoma (FA) cases. We performed immunohistochemical staining of glutaminolysis-related proteins (glutaminase 1 [GLS1], glutamate dehydrogenase [GDH], and amino acid transporter-2 [ASCT-2]).

CONCLUSION

Glutamine metabolism-related protein expression differed among the histologic subtypes of thyroid cancer.

Metabolic strategies of melanoma cells: Mechanisms, interactions with the tumor microenvironment, and therapeutic implications

Melanomas are metabolically heterogeneous, and they are able to adapt in order to utilize a variety of fuels that facilitate tumor progression and metastasis. The significance of metabolism in melanoma is supported by growing evidence of impact on the efficacy of contemporary therapies for this disease. There are also data to support that the metabolic phenotypes of melanoma cells depend upon contributions from both intrinsic oncogenic pathways and extrinsic factors in the tumor microenvironment. This review summarizes current understanding of the metabolic processes that promote cutaneous melanoma tumorigenesis and progression, the regulation of cancer cell metabolism by the tumor microenvironment, and the impact of metabolic pathways on targeted and immune therapies.

The biology and therapeutic management of melanoma brain metastases

The recent years have seen significant progress in the development of systemic therapies to treat patients with advanced melanoma. Use of these new treatment modalities, which include immune checkpoint inhibitors and small molecule BRAF inhibitors, lead to increased overall survival and better outcomes. Although revolutionary, these therapies are often less effective against melanoma brain metastases, and frequently the CNS is the major site of treatment failure. The development of brain metastases remains a serious complication of advanced melanoma that is associated with significant morbidity and mortality. New approaches to both prevent the development of brain metastases and treat established disease are urgently needed. In this review we will outline the mechanisms underlying the development of melanoma brain metastases and will discuss how new insights into metastasis biology are driving the development of new therapeutic strategies. Finally, we will describe the latest data from the ongoing clinical trials for patients with melanoma brain metastases.

Dimeric and tetrameric forms of muscle fructose-1,6-bisphosphatase play different roles in the cell

Muscle fructose 1,6-bisphosphatase (FBP2), besides being a regulatory enzyme of glyconeogenesis also protects mitochondria against calcium stress and plays a key role in regulation of the cell cycle, promoting cardiomyocytes survival. However, in cancer cells, FBP2 acts as an anti-oncogenic/anti-proliferative protein. Here, we show that the physiological function of FBP2 depends both on its level of expression in a cell as well as its oligomerization state. Animal fructose-1,6-bisphosphatases are thought to function as tetramers. We present evidence that FBP2 exists in an equilibrium between tetramers and dimers. The dimeric form is fully active and insensitive to AMP, the main allosteric inhibitor of FBP2. Tetramerization induces the sensitivity of the protein to AMP, but it requires the presence of a hydrophobic central region in which leucine 190 plays a crucial role. Only the tetrameric form of FBP2 is retained in cardiomyocyte cell nucleus whereas only the dimeric form associates with mitochondria and protects them against stress stimuli, such as elevated calcium and H₂O₂ level. Remarkably, in hypoxic conditions, which are typical for many cancers, FBP2 ceases to interact with mitochondria and loses its pro-survival potential. Our results throw new light on the basis of the diverse role of FBP2 in cells.

Breast Cancer-Derived Lung Metastases Show Increased Pyruvate Carboxylase-Dependent Anaplerosis

Cellular proliferation depends on refilling the tricarboxylic acid (TCA) cycle to support biomass production (anaplerosis). The two major anaplerotic pathways in cells are pyruvate conversion to oxaloacetate via pyruvate carboxylase (PC) and glutamine conversion to α-ketoglutarate. Cancers often show an organ-specific reliance on either pathway. However, it remains unknown whether they adapt their mode of anaplerosis when metastasizing to a distant organ. We measured PC-dependent anaplerosis in breast-cancer-derived lung metastases compared to their primary cancers using in vivo ¹³C tracer analysis. We discovered that lung metastases have higher PC-dependent anaplerosis compared to primary breast cancers. Based on in vitro analysis and a mathematical model for the determination of compartment-specific metabolite concentrations, we found that mitochondrial pyruvate concentrations can promote PC-dependent anaplerosis via enzyme kinetics. In conclusion, we show that breast cancer cells proliferating as lung metastases activate PC-dependent anaplerosis in response to the lung microenvironment.

The Glycogen Shunt Maintains Glycolytic Homeostasis and the Warburg Effect in Cancer

Despite many decades of study there is a lack of a quantitative explanation for the Warburg effect in cancer. We propose that the glycogen shunt, a pathway recently shown to be critical for cancer cell survival, may explain the excess lactate generation under aerobic conditions characteristic of the Warburg effect. The proposal is based on research on yeast and mammalian muscle and brain that demonstrates that the glycogen shunt functions to maintain homeostasis of glycolytic intermediates and ATP during large shifts in glucose supply or demand. Loss of the glycogen shunt leads to cell death under substrate stress. Similarities between the glycogen shunt in yeast and cancer cells lead us here to propose a parallel explanation of the lactate produced by cancer cells in the Warburg effect. The model also explains the need for the active tetramer and inactive dimer forms of pyruvate kinase (PKM2) in cancer cells, similar to the two forms of Pyk2p in yeast, as critical for regulating the glycogen shunt flux. The novel role proposed for the glycogen shunt implicates the high activities of glycogen synthase and fructose bisphosphatase in tumors as potential targets for therapy.

Mechanisms and clinical implications of tumor heterogeneity and convergence on recurrent phenotypes

Tumor heterogeneity has been identified at various -omic levels. The tumor genome, transcriptome, proteome, and phenome can vary widely across cells in patient tumors and are influenced by tumor cell interactions with heterogeneous physical conditions and cellular components of the tumor microenvironment. Here, we explore the concept that while variation exists at multiple -omic levels, changes at each of these levels converge on the same pathways and lead to convergent phenotypes in tumors that can provide common drug targets. These phenotypes include cellular growth and proliferation, sustained oncogenic signaling, and immune avoidance, among others. Tumor heterogeneity complicates treatment of patient cancers as it leads to varied response to therapies. Identification of convergent cellular phenotypes arising in patient cancers and targeted therapies that reverse them has the potential to transform the way clinicians treat these cancers and to improve patient outcome.

[Tumor Cells and Micro-environment in Brain Metastases]

近年来，随着早期诊断的方法的出现及精准治疗的应用，肺癌患者的生存及生活质量都得到很大改善。然而，对于肺癌的脑转移病灶，目前仍缺乏一个理想的治疗方案，严重影响了该部分患者生存状态。了解肿瘤细胞如何在中枢神经系统定植、生长和侵袭等相关生物学行为及其产生机制对预防及治疗肿瘤细胞脑转移病灶具有重大的意义。“种子-土壤”这一假说可以很好的解释这一过程，这一假说的关键即肿瘤细胞可与中枢神经系统微环境各组成之间产生相互适应性变化，正是这种相互作用决定了脑转移病灶的发生发展。本文就脑转移肿瘤细胞、脑转移肿瘤微环境及他们之间的相互作用进行综述，旨在为脑转移病灶的治疗提供新的思路。

High glucose levels boost the aggressiveness of highly metastatic cholangiocarcinoma cells via O-GlcNAcylation

Increased glucose utilization is a feature of cancer cells to support cell survival, proliferation, and metastasis. An association between diabetes mellitus and cancer progression was previously demonstrated in cancers including cholangiocarcinoma (CCA). This study was aimed to determine the effects of high glucose on protein O-GlcNAcylation and metastatic potentials of CCA cells. Two pairs each of the parental low metastatic and highly metastatic CCA sublines were cultured in normal (5.6 mM) or high (25 mM) glucose media. The migration and invasion abilities were determined and underlying mechanisms were explored. Results revealed that high glucose promoted migration and invasion of CCA cells that were more pronounced in the highly metastatic sublines. Concomitantly, high glucose increased global O-GlcNAcylated proteins, the expressions of vimentin, hexokinase, glucosamine-fructose-6-phosphate amidotransferase (GFAT) and O-GlcNAc transferase of CCA cells. The glucose level that promoted migration/invasion was shown to be potentiated by the induction of GFAT, O-GlcNAcylation and an increase of O-GlcNAcylated vimentin and vimentin expression. Treatment with a GFAT inhibitor reduced global O-GlcNAcylated proteins, vimentin expression, and alleviated cell migration. Altogether, these results suggested the role of high glucose enhanced CCA metastasis via modulation of O-GlcNAcylation, through the expressions of GFAT and vimentin.

Cerebral Gluconeogenesis and Diseases

The gluconeogenesis pathway, which has been known to normally present in the liver, kidney, intestine, or muscle, has four irreversible steps catalyzed by the enzymes: pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase, and glucose 6-phosphatase. Studies have also demonstrated evidence that gluconeogenesis exists in brain astrocytes but no convincing data have yet been found in neurons. Astrocytes exhibit significant 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 activity, a key mechanism for regulating glycolysis and gluconeogenesis. Astrocytes are unique in that they use glycolysis to produce lactate, which is then shuttled into neurons and used as gluconeogenic precursors for reduction. This gluconeogenesis pathway found in astrocytes is becoming more recognized as an important alternative glucose source for neurons, specifically in ischemic stroke and brain tumor. Further studies are needed to discover how the gluconeogenesis pathway is controlled in the brain, which may lead to the development of therapeutic targets to control energy levels and cellular survival in ischemic stroke patients, or inhibit gluconeogenesis in brain tumors to promote malignant cell death and tumor regression. While there are extensive studies on the mechanisms of cerebral glycolysis in ischemic stroke and brain tumors, studies on cerebral gluconeogenesis are limited. Here, we review studies done to date regarding gluconeogenesis to evaluate whether this metabolic pathway is beneficial or detrimental to the brain under these pathological conditions.

Cancer and the metastatic substrate

Seventy percent of cancer patients have detectable metastases when they receive a diagnosis and 90% of cancer deaths result from metastases. These two facts emphasise the urgency for research to study the mechanisms and processes that enable metastasis. We need to develop a greater understanding of the cellular and molecular mechanisms that cause metastasis and also we need to do more. We must also consider the micro- and macro-environmental factors that influence this disease. Studying this environmental context has led us to update the ‘seed and soil’ hypothesis which dates back to the 19th century. This theory describes cancerous cells as seeds and the substrate as the soil in target organs though this may seem antiquated. Nonetheless, the tissue specificity that researchers have recently observed in metastatic colonisation supports the validity of the seed and soil theory. We now know that the metastatic potential of a tumour cell depends on multiple, reciprocal interactions between the primary tumour and distant sites. These interactions determine tumour progression. Studies of metastasis have allowed us to develop treatments that focus on therapeutic effectiveness. These new treatments account for the frequent metastasis of some tumours to target organs such as bones, lungs, brain, and liver. The purpose of this review is first to describe interactions between the cellular and molecular entities and the target organ tumour environment that enables metastasis. A second aim is to describe the complex mechanisms that mediate these interactions.

Brain metastasis: Unique challenges and open opportunities

The metastasis of cancer to the central nervous system (CNS) remains a devastating clinical reality, carrying an estimated survival time of less than one year in spite of recent therapeutic breakthroughs for other disease contexts. Advances in brain metastasis research are hindered by a number of factors, including its complicated nature and the difficulty of modeling metastatic cancer growth in the unique brain microenvironment. In this review, we will discuss the clinical challenge, and compare the merits and limitations of the available models for brain metastasis research. Additionally, we will specifically address current knowledge on how brain metastases take advantage of the unique brain environment to benefit their own growth. Finally, we will explore the distinctive metabolic and chemical characteristics of the brain and how these paradoxically represent barriers to establishment of brain metastasis, but also provide ample supplies for metastatic cells' growth in the brain. We envision that multi-disciplinary innovative approaches will open opportunities for the field to make breakthroughs in tackling unique challenges of brain metastasis.

Diagnostic value of gadobutrol versus gadopentetate dimeglumine in enhanced MRI of brain metastases

PURPOSE

To compare gadobutrol and gadopentetate dimeglumine (Gd-DTPA) contrast-enhanced magnetic resonance imaging (MRI) at 3T for visualizing brain metastases.

MATERIALS AND METHODS

The present randomized study included 60 consecutive patients with known or suspected brain metastases from systemic malignancies. Two enhanced cerebral MR scans were performed in each patient within an interval of 2-5 days using different contrast agents (gadobutrol or Gd-DTPA) at 3T. The dose of the contrast agents (0.1 mmol/kg Gd) was also identical. The axial T₁ FLAIR images at 3, 7, and 10 minutes after the injection of the contrast agent were obtained for evaluation. Two experienced radiologists performed subjective evaluation of the image quality, made the choice of the optimal images, and performed an objective evaluation including: signal-to-noise ratio (SNR) of the brain metastases, contrast-to-noise ratio (CNR), contrast enhancement (CE), contrast-to-brain ratio (CBR), and contrast enhancement ratio (CER) of the brain metastases.

RESULTS

Subjective evaluation showed that at 3, 7, and 10 minutes gadobutrol elicited higher scores (margin score: 3.56 ± 0.74 vs. 3.33 ± 0.93, 3.68 ± 0.57 vs. 3.45 ± 0.81, 3.58 ± 0.71 vs. 3.43 ± 0.76; interior score: 2.83 ± 0.42 vs. 2.63 ± 0.61, 2.86 ± 0.38 vs. 2.73 ± 0.52, 2.80 ± 0.42 vs. 2.69 ± 0.53; and overall score: 4.42 ± 0.98 vs. 4.09 ± 1.19, 4.57 ± 0.75 vs. 4.26 ± 1.05, 4.48 ± 0.83 vs. 4.21 ± 1.03, respectively) in displaying the details and overall lesions than Gd-DTPA (repeated measures analysis of variance [ANOVA], margin score: P = 0.001, < 0.0001, 0.006; interior score: P < 0.0001, 0.004, 0.009; and overall score: P = 0.001, < 0.0001, < 0.0001, respectively). Subjective optimal image evaluation showed that the percentage of image assessed as "gadobutrol was better than Gd-DTPA (41.2-44.1%)" was greater than that assessed as "Gd-DTPA was better than gadobutrol (5.9-26.5%)." Objective evaluation showed that at 3, 7, and 10 minutes the SNR (214.17 ± 85.70 vs. 199.57 ± 85.08, 214.80 ± 86.03 vs. 199.19 ± 84.74, and 213.83 ± 82.46 vs. 193.68 ± 79.59, respectively), CNR (68.64 ± 50.18 vs. 57.88 ± 51.06, 75.42 ± 53.19 vs. 63.74 ± 53.91, and 77.13 ± 51.86 vs. 63.21 ± 51.71, respectively), CE (101.76 ± 63.31 vs. 87.61 ± 64.85, 99.85 ± 61.56 vs. 85.08 ± 64.98, and 100.33 ± 58.63 vs. 82.73 ± 61.73, respectively), CBR (0.48 ± 0.32 vs. 0.40 ± 0.33, 0.54 ± 0.34 vs. 0.46 ± 0.35, and 0.56 ± 0.34 vs. 0.47 ± 0.34, respectively), and CER (0.99 ± 0.69 vs. 0.88 ± 0.81, 0.97 ± 0.68 vs. 0.86 ± 0.84, and 0.98 ± 0.65 vs. 0.85 ± 0.80, respectively) were all higher when using gadobutrol compared with Gd-DTPA in the enhanced MR (repeated measures ANOVA, all P < 0.0001). On Gd-DTPA enhanced images, 289, 292, and 292 lesions at 3, 7, and 10 minutes were detected by the two radiologists, while 295, 301, and 301 lesions were detected on gadobutrol-enhanced images, respectively.

CONCLUSION

Using a 3T T₁ FLAIR sequence, gadobutrol (0.1 mmol/kg body weight)-enhanced MR resulted in more conspicuous brain metastases, and more metastases compared with the same dose of Gd-DTPA. A delay time of 7 minutes for postcontrast MRI in patients with brain metastases is suggested in clinical practice.

LEVEL OF EVIDENCE

2 J. MAGN. RESON. IMAGING 2017;45:1827-1834.

ERRα-Regulated Lactate Metabolism Contributes to Resistance to Targeted Therapies in Breast Cancer

Imaging studies in animals and in humans have indicated that the oxygenation and nutritional status of solid tumors is dynamic. Furthermore, the extremely low level of glucose within tumors, while reflecting its rapid uptake and metabolism, also suggests that cancer cells must rely on other energy sources in some circumstances. Here, we find that some breast cancer cells can switch to utilizing lactate as a primary source of energy, allowing them to survive glucose deprivation for extended periods, and that this activity confers resistance to PI3K/mTOR inhibitors. The nuclear receptor, estrogen-related receptor alpha (ERRα), was shown to regulate the expression of genes required for lactate utilization, and isotopomer analysis revealed that genetic or pharmacological inhibition of ERRα activity compromised lactate oxidation. Importantly, ERRα antagonists increased the in vitro and in vivo efficacy of PI3K/mTOR inhibitors, highlighting the potential clinical utility of this drug combination.

Glycogen metabolism has a key role in the cancer microenvironment and provides new targets for cancer therapy

Metabolic reprogramming is a hallmark of cancer cells and contributes to their adaption within the tumour microenvironment and resistance to anticancer therapies. Recently, glycogen metabolism has become a recognised feature of cancer cells since it is upregulated in many tumour types, suggesting that it is an important aspect of cancer cell pathophysiology. Here, we provide an overview of glycogen metabolism and its regulation, with a focus on its role in metabolic reprogramming of cancer cells under stress conditions such as hypoxia, glucose deprivation and anticancer treatment. The various methods to detect glycogen in tumours in vivo as well as pharmacological modulators of glycogen metabolism are also reviewed. Finally, we discuss the therapeutic value of targeting glycogen metabolism as a strategy for combinational approaches in cancer treatment.

Mitochondrial Phosphoenolpyruvate Carboxykinase Regulates Metabolic Adaptation and Enables Glucose-Independent Tumor Growth

Cancer cells adapt metabolically to proliferate under nutrient limitation. Here we used combined transcriptional-metabolomic network analysis to identify metabolic pathways that support glucose-independent tumor cell proliferation. We found that glucose deprivation stimulated re-wiring of the tricarboxylic acid (TCA) cycle and early steps of gluconeogenesis to promote glucose-independent cell proliferation. Glucose limitation promoted the production of phosphoenolpyruvate (PEP) from glutamine via the activity of mitochondrial PEP-carboxykinase (PCK2). Under these conditions, glutamine-derived PEP was used to fuel biosynthetic pathways normally sustained by glucose, including serine and purine biosynthesis. PCK2 expression was required to maintain tumor cell proliferation under limited-glucose conditions in vitro and tumor growth in vivo. Elevated PCK2 expression is observed in several human tumor types and enriched in tumor tissue from non-small-cell lung cancer (NSCLC) patients. Our results define a role for PCK2 in cancer cell metabolic reprogramming that promotes glucose-independent cell growth and metabolic stress resistance in human tumors.

STAT3:FOXM1 and MCT1 drive uterine cervix carcinoma fitness to a lactate-rich microenvironment

Uterine cervix cancer is the second most common malignancy in women worldwide with human papillomavirus (HPV) as the etiologic factor. The two main histological variants, squamous cell carcinomas (SCC) and adenocarcinomas (AC), resemble the cell morphology of exocervix and endocervix, respectively. Cancer metabolism is a cancer hallmark conditioned by the microenvironment. As uterine cervix homeostasis is dependent on lactate, we hypothesized lactate plays a role in uterine cervix cancer progression. Using in vitro (SiHa-SCC and HeLa-AC) and BALB-c/SCID models, we demonstrated that lactate metabolism is linked to histological types, with SCC predominantly consuming and AC producing lactate. MCT1 is a key factor, allowing lactate consumption and being regulated in vitro by lactate through the FOXM1:STAT3 pathway. In vivo models showed that SCC (SiHa) expresses MCT1 and is dependent on lactate to grow, whereas AC (HeLa) expresses MCT1 and MCT4, with higher growth capacities. Immunohistochemical analysis of tissue microarrays (TMA) from human cervical tumors showed that MCT1 expression associates with the SCC type and metastatic behavior of AC, whereas MCT4 expression concomitantly increases from in situ SCC to invasive SCC and is significantly associated with the AC type. Consistently, FOXM1 expression is statistically associated with MCT1 positivity in SCC, whereas the expression of FOXO3a, a FOXM1 functional antagonist, is linked to MCT1 negativity in AC. Our study reinforces the role of the microenvironment in the metabolic adaptation of cancer cells, showing that cells that retain metabolic features of their normal counterparts are positively selected by the organ's microenvironment and will survive. In particular, MCT1 was shown to be a key element in uterine cervix cancer development; however, further studies are needed to validate MCT1 as a suitable therapeutic target in uterine cervix cancer.

The influence of the pre-metastatic niche on breast cancer metastasis

The emergence of metastatic disease constitutes a significant life-threatening development during cancer progression. To date, intensive efforts have been focused on understanding the intrinsic properties that confer malignant potential to cancer cells, as well as the role of the primary tumour microenvironment in promoting cancer metastasis. Beyond events occurring at the primary site, the metastatic cascade is composed of numerous barriers that must be overcome in order for disseminating cancer cells to form distal metastases. The most formidable of these is the ability of cancer cells to seed and grow in a completely foreign microenvironment. Interestingly, solid malignancies often display a particular tropism for specific tissue sites. For example, breast patients with metastatic disease will often develop bone, lung, liver or brain metastases. This mini-review will explore aspects of pre-existing and induced metastatic niches and focus on how the unique composition and function of diverse niche components, within common sites of breast cancer metastasis, enable the survival and growth of disseminated cancer cells. These common supportive functions of the niche are provided by a complex array of stromal components and molecular mechanisms that are, in part, reflective of the tissue in which the metastases arise. Finally, the metastatic niche is a dynamic structure that is continually altered and sculpted by the cancer cells during progression of the metastatic lesion.

Divergent and convergent evolution in metastases suggest treatment strategies based on specific metastatic sites

Cancer cells, although maximally fit at their primary site, typically have lower fitness on the adaptive landscapes offered by the metastatic sites due to organ-specific variations in mesenchymal properties and signaling pathways. Clinically evident metastases will exhibit time-dependent divergence from the phenotypic mean of the primary population as the tumor cells evolve and adapt to their new circumstances. In contrast, tumors from different primary sites evolving on identical metastatic adaptive landscapes exhibit phenotypic convergence so that, for example, metastases in the liver from different primary tumors will evolve toward similar adaptive phenotypes. The combination of evolutionary divergence from the primary cancer phenotype and convergence towards similar adaptive strategies in the same tissue cause significant variations in treatment responses particularly for highly targeted therapies.

This suggest that optimal therapies for disseminated cancer must take into account the site(s) of metastatic growth as well as the primary organ.

Background and objective: Systemic therapy for metastatic cancer is currently determined exclusively by the site of tumor origin. Yet, there is increasing evidence that the molecular characteristics of metastases significantly differ from the primary tumor. We define the evolutionary dynamics of metastases that govern this molecular divergence and examine their potential contribution to variations in response to targeted therapies.

Methodology: Darwinian interactions of transformed cells with the tissue microenvironments at primary and metastatic sites are analyzed using evolutionary game theory. Computational models simulate responses to targeted therapies in different organs within the same patient.

Results: Tumor cells, although maximally fit at their primary site, typically have lower fitness on the adaptive landscapes offered by the metastatic sites due to organ-specific variations in mesenchymal properties and signaling pathways. Clinically evident metastases usually exhibit time-dependent divergence from the phenotypic mean of the primary population as the tumor cells evolve and adapt to their new circumstances. In contrast, tumors from different primary sites evolving on identical metastatic adaptive landscapes exhibit phenotypic convergence. Thus, metastases in the liver from different primary tumors and even in different hosts will evolve toward similar adaptive phenotypes. The combination of evolutionary divergence from the primary cancer phenotype and convergence towards similar adaptive strategies in the same tissue cause significant variations in treatment responses particularly for highly targeted therapies.

Conclusion and implications: The results suggest that optimal therapies for disseminated cancer must take into account the site(s) of metastatic growth as well as the primary organ.

Emerging strategies for treating brain metastases from breast cancer

Brain metastasis is an end stage in breast cancer progression. Traditional treatment options have minimal efficacy, and overall survival is on the order of months. The incidence of brain metastatic disease is increasing with the improved management of systemic disease and prolongation of survival. Unfortunately, the targeted therapies that control systemic disease have diminished efficacy against brain lesions. There are reasons to be optimistic, however, as emerging therapies have shown promise in preclinical and early clinical settings. This review discusses recent advances in breast cancer brain metastasis therapy and potential approaches for successful treatment.

Molecular and Genetic Predictors of Breast-to-Brain Metastasis: Review and Case Presentation

Brain metastases are the most common intracranial malignancy, and breast cancer is the second most common cancer to metastasize to the brain. Intracranial disease is a late manifestation of breast cancer with few effective treatment options, affecting 15-50% of breast cancer patients, depending upon molecular subtype. In this review article, we describe the genetic, molecular, and metabolic changes in breast cancer cells that facilitate breast to brain metastasis. We believe that advances in the understanding of breast to brain metastasis pathogenesis will lead to targeted molecular therapies and to improvements in the ability to prospectively identify patients at increased risk for developing intracranial disease.