Genetic changes in tumour microenvironments

Therapeutic Strategies to Overcome Fibrotic Barriers to Nanomedicine in the Pancreatic Tumor Microenvironment

Pancreatic cancer is notorious for its dismal prognosis. The enhanced permeability and retention (EPR) effect theory posits that nanomedicines (therapeutics in the size range of approximately 10-200 nm) selectively accumulate in tumors. Nanomedicine has thus been suggested to be the "magic bullet"-both effective and safe-to treat pancreatic cancer. However, the densely fibrotic tumor microenvironment of pancreatic cancer impedes nanomedicine delivery. The EPR effect is thus insufficient to achieve a significant therapeutic effect. Intratumoral fibrosis is chiefly driven by aberrantly activated fibroblasts and the extracellular matrix (ECM) components secreted. Fibroblast and ECM abnormalities offer various potential targets for therapeutic intervention. In this review, we detail the diverse strategies being tested to overcome the fibrotic barriers to nanomedicine in pancreatic cancer. Strategies that target the fibrotic tissue/process are discussed first, which are followed by strategies to optimize nanomedicine design. We provide an overview of how a deeper understanding, increasingly at single-cell resolution, of fibroblast biology is revealing the complex role of the fibrotic stroma in pancreatic cancer pathogenesis and consider the therapeutic implications. Finally, we discuss critical gaps in our understanding and how we might better formulate strategies to successfully overcome the fibrotic barriers in pancreatic cancer.

The Tumor Microenvironment in Tumorigenesis and Therapy Resistance Revisited

Tumorigenesis is a complex and dynamic process involving cell-cell and cell-extracellular matrix (ECM) interactions that allow tumor cell growth, drug resistance and metastasis. This review provides an updated summary of the role played by the tumor microenvironment (TME) components and hypoxia in tumorigenesis, and highlight various ways through which tumor cells reprogram normal cells into phenotypes that are pro-tumorigenic, including cancer associated- fibroblasts, -macrophages and -endothelial cells. Tumor cells secrete numerous factors leading to the transformation of a previously anti-tumorigenic environment into a pro-tumorigenic environment. Once formed, solid tumors continue to interact with various stromal cells, including local and infiltrating fibroblasts, macrophages, mesenchymal stem cells, endothelial cells, pericytes, and secreted factors and the ECM within the tumor microenvironment (TME). The TME is key to tumorigenesis, drug response and treatment outcome. Importantly, stromal cells and secreted factors can initially be anti-tumorigenic, but over time promote tumorigenesis and induce therapy resistance. To counter hypoxia, increased angiogenesis leads to the formation of new vascular networks in order to actively promote and sustain tumor growth via the supply of oxygen and nutrients, whilst removing metabolic waste. Angiogenic vascular network formation aid in tumor cell metastatic dissemination. Successful tumor treatment and novel drug development require the identification and therapeutic targeting of pro-tumorigenic components of the TME including cancer-associated- fibroblasts (CAFs) and -macrophages (CAMs), hypoxia, blocking ECM-receptor interactions, in addition to the targeting of tumor cells. The reprogramming of stromal cells and the immune response to be anti-tumorigenic is key to therapeutic success. Lastly, this review highlights potential TME- and hypoxia-centered therapies under investigation.

Genomic Landscape in Neoplasm-Like Stroma Reveals Distinct Prognostic Subtypes of Pancreatic Ductal Adenocarcinoma

As a main component of the tumor microenvironment, the stroma is critical in development, progression, and metastasis of pancreatic ductal adenocarcinoma (PDAC). The genomic status and its relationship of neoplastic and stromal components remain unclear in PDAC. We performed targeted sequencing for 1,021 cancer-suspected genes on parallel microdissected stromal and neoplastic components from 50 operable PDAC patients. Clonality analysis of mutations was conducted to reconstruct the evolutionary trajectory, and then molecular subtypes were established. Multi-lineage differentiation potential and mesenchymal transformation of KRAS-mutant cell line Panc1 were evaluated using RT-PCR and immunofluorescence staining. In this study, 39 (78.0%) were genomically altered in stroma, with KRAS (71.8%), TP53 (61.5%), and CDKN2A (23.1%) as the most commonly mutated genes. The majority of stromal mutations (89.8%) were detected in matched neoplastic components. Patients with KRAS/TP53-mut stroma demonstrated a higher tumor cell fraction (TCF) than did those with wild-type (WT) stroma (p = 0.0371, p = 0.0014). In both components, mutants KRAS and TP53 often occurred as clonal events, and the allele frequencies presented linear correlation in the same specimen. All neoplasm-like stroma (characterized with all or initial neoplastic clones and driver events in stroma) harbored KRAS or TP53 mutations. Neoplasm-like and KRAS-mutant stroma was associated with shorter disease-free survival. It is a new finding for the existence of driver gene mutations in PDAC stroma. These data suggest that genomic features of stromal components may serve as prognostic biomarkers in resectable PDAC and might help to guide a more precise treatment paradigm in therapeutic options.

Architecture of Cancer-Associated Fibroblasts in Tumor Microenvironment: Mapping Their Origins, Heterogeneity, and Role in Cancer Therapy Resistance

The tumor stroma, a key component of the tumor microenvironment (TME), is a key determinant of response and resistance to cancer treatment. The stromal cells, extracellular matrix (ECM), and blood vessels influence cancer cell response to therapy and play key roles in tumor relapse and therapeutic outcomes. Of the stromal cells present in the TME, much attention has been given to cancer-associated fibroblasts (CAFs) as they are the most abundant and important in cancer initiation, progression, and therapy resistance. Besides releasing several factors, CAFs also synthesize the ECM, a key component of the tumor stroma. In this expert review, we examine the role of CAFs in the regulation of tumor cell behavior and reveal how CAF-derived factors and signaling influence tumor cell heterogeneity and development of novel strategies to combat cancer. Importantly, CAFs display both phenotypic and functional heterogeneity, with significant ramifications on CAF-directed therapies. Principal anti-cancer therapies targeting CAFs take the form of: (1) CAFs' ablation through use of immunotherapies, (2) re-education of CAFs to normalize the cells, (3) cellular therapies involving CAFs delivering drugs such as oncolytic adenoviruses, and (4) stromal depletion via targeting the ECM and its related signaling. The CAFs' heterogeneity could be a result of different cellular origins and the cancer-specific tumor microenvironmental effects, underscoring the need for further multiomics and biochemical studies on CAFs and the subsets. Lastly, we present recent advances in therapeutic targeting of CAFs and the success of such endeavors or their lack thereof. We recommend that to advance global public health and personalized medicine, treatments in the oncology clinic should be combinatorial in nature, strategically targeting both cancer cells and stromal cells, and their interactions.

NK Cell and Fibroblast-Mediated Regulation of Skin Squamous Cell Carcinoma Invasion by CLEC2A Is Compromised in Xeroderma Pigmentosum

The ability of cancer cells to invade and disseminate can be affected by components of the surrounding microenvironment. To identify dermal components that regulate the growth of epidermal carcinomas, we studied the genetic disease called xeroderma pigmentosum that bears mutations in genes involved in the nucleotide excision repair of DNA. Patients with xeroderma pigmentosum are more prone to develop cutaneous tumors than the general population and their dermal fibroblasts display the features of dermal cancer-associated fibroblasts, which promote the invasion of keratinocytes. Here, we report that 3-dimensional dermal cultures of fibroblasts from healthy donors but not from patients with xeroderma pigmentosum complementation group C express CLEC2A, which is the ligand of the activating NK cell receptor NKp65. A similar loss of CLEC2A was observed in sporadic dermal cancer-associated fibroblasts and upon the culture of fibroblasts with cutaneous squamous cell carcinoma-conditioned medium. Using an innovative 3-dimensional organotypic skin culture model that contain NK cells in addition to fibroblasts and squamous cell carcinoma cells, we unveiled a key role of CLEC2A that orchestrates a crosstalk between fibroblasts and NK cells, thereby leading to the control of squamous cell carcinoma invasion. These findings indicate that CLEC2A-expressing dermal fibroblasts play a major role in immune surveillance of the skin.

A-kinase anchoring protein 12 is downregulated in human hepatocellular carcinoma and its deficiency in mice aggravates thioacetamide-induced liver injury

AKAP12 belongs to A-kinase anchoring protein (AKAP) family of scaffold proteins and is known as a tumor suppressor in several human cancer types. Its role as a tumor suppressor in hepatocellular carcinoma (HCC) was proposed due to its downregulation and epigenetic modification in human HCC; however, the effect of its deficiency on liver injuries, such as liver fibrosis and cancer has been poorly studied. By analyzing tumor and non-tumor tissues of 15 patients with HCC, it was confirmed that AKAP12 expression was downregulated in human HCC as compared with adjacent non-tumor tissues. Immunohistochemical staining of mouse liver tissue for AKAP12 revealed that its sinusoidal expression was diminished in capillarized endothelium after 8 weeks of thioacetamide (TAA) administration. AKAP12 deficiency resulted in the promotion of ductular response of biliary epithelial cells, whereas overall fibrosis and myofibroblast activation were comparable between genotypes after short-term TAA treatment. The mRNA expressions of some fibrosis-related genes such as those encoding epithelial cell adhesion molecule, collagen type 1 α1 and elastin were upregulated in liver tissues of AKAP12-knockout mice. Long-term administration of TAA for 26 weeks led to the development of liver tumors; the incidence of tumor development was higher in AKAP12-deficient mice than in wild-type littermates. Together, these results suggest that AKAP12 functions as a tumor suppressor in liver cancer and is associated with the regulation of hepatic non-parenchymal cells.

Teaming Up for Trouble: Cancer Cells, Transforming Growth Factor-β1 Signaling and the Epigenetic Corruption of Stromal Naïve Fibroblasts

It is well recognized that cancer cells subvert the phenotype of stromal naïve fibroblasts and instruct the neighboring cells to sustain their growth agenda. The mechanisms underpinning the switch of fibroblasts to cancer-associated fibroblasts (CAFs) are the focus of intense investigation. One of the most significant hallmarks of the biological identity of CAFs is that their tumor-promoting phenotype is stably maintained during in vitro and ex vivo propagation without the continual interaction with the adjacent cancer cells. In this review, we discuss robust evidence showing that the master cytokine Transforming Growth Factor-β1 (TGFβ-1) is a prime mover in reshaping, via epigenetic switches, the phenotype of stromal fibroblasts to a durable state. We also examine, in detail, the pervasive involvement of TGFβ-1 signaling from both cancer cells and CAFs in fostering cancer development, taking colorectal cancer (CRC) as a paradigm of human neoplasia. Finally, we review the stroma-centric anticancer therapeutic approach focused on CAFs—the most abundant cell population of the tumor microenvironment (TME)—as target cells.

Mast cells are directly activated by contact with cancer cells by a mechanism involving autocrine formation of adenosine and autocrine/paracrine signaling of the adenosine A3 receptor

Mast cells (MCs) constitute an important part of the tumor microenvironment (TME). However, their underlying mechanisms of activation within the TME remain poorly understood. Here we show that recapitulating cell-to-cell contact interactions by exposing MCs to membranes derived from a number of cancer cell types, results in MC activation, evident by the increased phosphorylation of the ERK1/2 MAP kinases and Akt, in a phosphatidylinositol 3-kinase dependent fashion. Activation is unidirectional since MC derived membranes do not activate cancer cells. Stimulated ERK1/2 phosphorylation is strictly dependent on the ecto enzyme CD73 that mediates autocrine formation of adenosine, and is inhibited by knockdown of the A3 adenosine receptor (A3R) as well as by an A3R antagonist or by agonist-stimulated down-regulation of the A3R. We also show that cancer cell mediated triggering upregulates expression and stimulates secretion of interleukin 8 from the activated MCs. These findings provide evidence for a novel mode of unidirectional crosstalk between MCs and cancer cells implicating direct activation by cancer cells in MC reprogramming into a pro tumorigenic profile.

Cells Comprising the Prostate Cancer Microenvironment Lack Recurrent Clonal Somatic Genomic Aberrations

Prostate cancer-associated stroma (CAS) plays an active role in malignant transformation, tumor progression, and metastasis. Molecular analyses of CAS have demonstrated significant changes in gene expression; however, conflicting evidence exists on whether genomic alterations in benign cells comprising the tumor microenvironment (TME) underlie gene expression changes and oncogenic phenotypes. This study evaluates the nuclear and mitochondrial DNA integrity of prostate carcinoma cells, CAS, matched benign epithelium and benign epithelium-associated stroma by whole-genome copy-number analyses, targeted sequencing of TP53, and FISH. Array comparative genomic hybridization (aCGH) of CAS revealed a copy-neutral diploid genome with only rare and small somatic copy-number aberrations (SCNA). In contrast, several expected recurrent SCNAs were evident in the adjacent prostate carcinoma cells, including gains at 3q, 7p, and 8q, and losses at 8p and 10q. No somatic TP53 mutations were observed in CAS. Mitochondrial DNA (mtDNA) extracted from carcinoma cells and stroma identified 23 somatic mtDNA mutations in neoplastic epithelial cells, but only one mutation in stroma. Finally, genomic analyses identified no SCNAs, LOH, or copy-neutral LOH in cultured cancer-associated fibroblasts, which are known to promote prostate cancer progression in vivo

IMPLICATIONS

The gene expression changes observed in prostate cancer-adjacent stroma and the attendant contribution of the stroma to the development and progression of prostate cancer are not due to frequent or recurrent genomic alterations in the TME.

Dysregulation of redox-state-regulating enzymes in melanocytic skin tumours and the surrounding microenvironment

AIMS

To investigate redox-regulating enzymes that may have a special role in melanoma pathogenesis due to continuous exposure to microenvironment-produced and ultraviolet radiation-induced oxidative stress.

METHODS AND RESULTS

We assessed immunohistochemically the expression of antioxidant enzymes peroxiredoxins (Prxs) I-IV, sulfiredoxin (Srx) and redox-regulated proto-oncogene DJ-1 in material consisting of 30 benign naevi, 14 lentigo malignas and 67 malignant melanomas. Evaluation of immunostaining was performed with special attention paid to protein expression in different tumour compartments. In particular, the expression patterns of nuclear Prx I and Prx II and cytoplasmic DJ-1 were decreased significantly in melanomas compared with dysplastic and benign naevi. In multivariate analysis, several prognostic factors were identified: Prx III expression in the cytoplasm of stromal fibroblasts was associated with shortened melanoma-specific survival [hazard ratio (HR) 6.730; 95% confidence interval (CI) 1.579-28.689], while cytoplasmic Prx IV expression in endothelial cells (HR 6.563; 95% CI 1.750-24.620) and Srx expression in the cytoplasm of keratinocytes (HR 6.988; 95% CI 1.559-31.324) were associated with better prognosis independently of ulceration, thickness of melanoma or its diagnostic type.

CONCLUSIONS

Redox-regulating enzymes have the potential to serve as novel prognostic factors and targeting them may offer new therapeutic options in malignant melanoma.

Twist1 is a key regulator of cancer-associated fibroblasts

Cancer-associated fibroblasts (CAF) are key contributors to malignant progression, but their critical regulators remain largely unknown. In this study, we examined the role of Twist1, a central regulator of epithelial-mesenchymal transition in carcinoma cells, in the transdifferentiation of normal quiescent fibroblasts to CAF and we defined its upstream controls and downstream effectors. Primary human gastric fibroblast and CAF cultures were established from gastrectomy specimens and validated as nontumor cells by somatic mutation analyses. In these cultures, exposure to the proinflammatory cytokine IL6 commonly expressed in tumors was sufficient to induce Twist1 expression in normal fibroblasts and transdifferentiate them into CAFs via STAT3 phosphorylation. In xenograft models, tumor infiltration of Twist1-expressing CAFs was enhanced strongly by ectopic IL6 expression in gastric or breast cancer cells. We found that Twist1 expression was necessary and sufficient for CAF transdifferentiation. Enforced expression of Twist1 in normal fibroblasts was also sufficient to drive CAF marker expression and malignant character in gastric cancer cells both in vitro and in vivo. Conversely, silencing the expression of Twist1 in CAFs abrogated their tumor-promoting properties. Downstream of Twist1, we defined the chemokine CXCL12 as a transcriptional target. Clinically, CXCL12 and Twist1 expression were correlated in CAFs present in gastric tumor specimens. Finally, ectopic expression of Twist1 in normal fibroblasts suppressed premature senescence, whereas Twist1 attenuation accelerated senescence in CAFs. Our findings define Twist1 as a compelling target to deprogram the tumor-supporting features of the cancer microenvironment.

The clinical implication of cancer-associated microvasculature and fibroblast in advanced colorectal cancer patients with synchronous or metachronous metastases

BACKGROUND

We aimed to evaluate the clinical significance of microvessel density (MVD), lymphatic vessel density (LVD), and cancer-associated fibroblasts (CAFs) in relation to tumor location in advanced colorectal cancer (CRC).

METHODS

Using immunohistochemistry, we examined 181 advanced CRC patients for CD31 and D2-40 to measure MVD and LVD, respectively, α-smooth muscle actin (SMA) and desmin to identify CAFs, and PTEN to examine genetic changes of CAFs. To evaluate the regional heterogeneity of these properties, we examined tissue from four sites (the center and periphery of the primary cancer, a distant metastasis, and a lymph node metastasis) in each patient.

RESULTS

MVD, LVD, and CAFs showed significant heterogeneity with respect to the tumor location. LVD was the greatest in the center of the primary cancers and the amount of CAFs was the lowest in distant metastases. In distant metastases, those from the lung had higher LVD and MVD, but fewer CAFs than those from the liver, peritoneum, or ovary. Patients with low MVD and LVD in the center of the primary cancer had worse outcomes and patients with few CAFs in distant metastases and in the primary tumor had a lower survival rate. PTEN expression in CAFs in distant metastases was lost in 11 of 181 CRC patients (6.1%), which was associated with a worse prognosis.

CONCLUSIONS

The microenvironment, including cancer-associated microvasculature and fibroblasts, is heterogeneous with respect to the tumor location in CRC patients. Therefore, heterogeneity of microenvironments should be taken into account when managing CRC patients.

MicroRNA-21 in pancreatic ductal adenocarcinoma tumor-associated fibroblasts promotes metastasis

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is projected to rise to the second leading cause of U.S. cancer-related deaths by 2020. Novel therapeutic targets are desperately needed. MicroRNAs (miRs) are small noncoding RNAs that function by suppressing gene expression and are dysregulated in cancer. miR-21 is overexpressed in PDAC tumor cells (TC) and is associated with decreased survival, chemoresistance and invasion. Dysregulation of miR regulatory networks in PDAC tumor-associated fibroblasts (TAFs) have not been previously described. In this study, we show that miR-21 expression in TAFs promotes TC invasion.

METHODS

In-situ hybridization for miR-21 was performed on the 153 PDAC patient UCLA tissue microarray and 23 patient-matched lymph node metastases. Stromal and TC histoscores were correlated with clinicopathologic parameters by univariate and multivariate Cox regression. miR-21 positive cells were further characterized by immunofluorescence for mesenchymal/epithelial markers. For in vitro studies, TAFs were isolated from freshly resected human PDAC tumors by the outgrowth method. miR-21 was overexpressed/inhibited in fibroblasts and then co-cultured with GFP-MiaPaCa TCs to assess TC invasion in modified Boyden chambers.

RESULTS

miR-21 was upregulated in TAFs of 78% of tumors, and high miR-21 significantly correlated with decreased overall survival (P = 0.04). Stromal miR-21 expression was also significantly associated with lymph node invasion (P = 0.004), suggesting that it is driving TC spread. Co-immunofluorescence revealed that miR-21 colocalized with peritumoral fibroblasts expressing α-smooth muscle actin. Moreover, expression of miR-21 in primary TAFs correlated with miR-21 in TAFs from patient-matched LN metastases; evidence that PDAC tumor cells induce TAFs to express miR-21. miR-21 expression in TAFs and TCs promotes invasion of TCs and is inhibited with anti-miR-21.

CONCLUSIONS

miR-21 expression in PDAC TAFs is associated with decreased overall survival and promotes TC invasion. Anti-miR-21 may represent a novel therapeutic strategy for dual targeting of both tumor and stroma in PDAC.

Prevalence of PIK3CA mutations and the SNP rs17849079 in Arab breast cancer patients

Carcinomas initiate and progress due to genetic and epigenetic alterations in epithelial cells. However, recently, these alterations have also been reported in stromal fibroblasts. The gain-of-function mutations in the PI3K p110 catalytic subunit (PIK3CA) have been identified in many cancers with a current global incidence of 26% (18-40%) in breast carcinomas. We analyzed the mutational frequency of PIK3CA of three hotspots (exons 1, 9, and 20) in 81 primary invasive breast cancers (BC) and 25 cultured breast cancer-associated fibroblast (CAF) samples by Sanger sequencing in Arab breast cancer patients. Associations between the incidence of any PIK3CA mutation and several clinicopathologic characteristics were assessed using chi-square tests for categorical or t test for continuous variables. Furthermore, survival curves were estimated using the Kaplan-Meier method with the log rank test to evaluate the significance of their differences. We identified a total of 21 PIK3CA missense mutations with a frequency of 25.9%. The majority of the mutations, 17 out of 21 (81%), were in exon 20 (p.His1047Arg, p.His1047Lys, p.Thr1025Ala, p.Gly1049Arg, p.Asp1056Asn) while the remainder, 4 out of 21 (19%) were in exon 9 (p.Glu545Lys). PIK3CA mutations were significantly associated with lower grade and hormone receptor positivity. Although there was a favorable trend in overall survival for patients whose tumor harbored PIK3CA mutations, the difference was not statistically significant (P = 0.10). However, we did not detect any somatic mutations in CAFs. Furthermore, we have shown a high prevalence (8.2-fold) of a silent variant (SNP, rs17849079) in the Arab breast cancer population compared with disease-free individuals.

Plasticity of disseminating cancer cells in patients with epithelial malignancies

Current models suggest that at a certain but yet undefined time point of tumour development malignant cells with an aggressive phenotype start to disseminate via the blood stream into distant organs. This invasive phenotype appears to be associated with an epithelial-mesenchymal transition (EMT), which enables detachment of tumour cells from a primary site and migration. The reverse process of mesenchymal-epithelial transition (MET) might play a crucial role in the further steps of metastasis when circulating tumour cells (CTCs) settle down in distant organs and establish (micro-)metastasis. Nevertheless, the exact mechanisms and interplay of EMT and MET are only partially understood and their relevance in cancer patients is unclear. Research groups have just started to apply EMT-related markers in their studies on CTCs in cancer patients. In the present review, we summarize and discuss the current state of investigations on CTCs in the context of research on EMT/MET.

Genomic (in)stability of the breast tumor microenvironment

The breast tumor microenvironment plays an active role in tumorigenesis. Molecular alterations have been identified in tumor-associated stroma; however, there is considerable debate as to whether the stroma is characterized by genomic instability or whether detection of chromosomal alterations reflects technological artifact rather than the true genomic content of the tumor microenvironment. Thus, breast stroma specimens from 112 women undergoing reductive mammoplasty (n = 7), prophylactic mastectomy (n = 6), or mastectomy for a breast disease (n = 99) were frozen in optimal cutting temperature medium. Allelic imbalance (AI) analysis was conducted using a panel of 52 microsatellite markers in 484 stromal specimens from 98 women, of which 92% had no detectable AI events. When compared with previously generated AI data from 77 formalin-fixed, paraffin-embedded (FFPE) stroma specimens, 42% of which harbored at least one detectable AI event, the frequency of AI in the FFPE specimens (4.62%) was significantly higher (P < 0.001) than that found in frozen specimens (0.45%). This comparison of AI between FFPE and research-grade specimens suggests that past reports of AI in breast stroma reflect artifact in the archival specimens caused by formalin-fixation, paraffin-embedding and tissue storage. Furthermore, SNP data were generated from a subset of 86 stromal specimens using SNP arrays and copy number alterations were identified using Partek Genomics Suite. For 95% of the specimens, no detectable copy number alterations were found and the 11 changes that were detected were small and not shared between specimens. These data, therefore, support a model in which the tumor microenvironment is genetically stable.

An "elite hacker": breast tumors exploit the normal microenvironment program to instruct their progression and biological diversity

The year 2011 marked the 40 year anniversary of Richard Nixon signing the National Cancer Act, thus declaring the beginning of the "War on Cancer" in the United States. Whereas we have made tremendous progress toward understanding the genetics of tumors in the past four decades, and in developing enabling technology to dissect the molecular underpinnings of cancer at unprecedented resolution, it is only recently that the important role of the stromal microenvironment has been studied in detail. Cancer is a tissue-specific disease, and it is becoming clear that much of what we know about breast cancer progression parallels the biology of the normal breast differentiation, of which there is still much to learn. In particular, the normal breast and breast tumors share molecular, cellular, systemic and microenvironmental influences necessary for their progression. It is therefore enticing to consider a tumor to be a "rogue hacker"--one who exploits the weaknesses of a normal program for personal benefit. Understanding normal mammary gland biology and its "security vulnerabilities" may thus leave us better equipped to target breast cancer. In this review, we will provide a brief overview of the heterotypic cellular and molecular interactions within the microenvironment of the developing mammary gland that are necessary for functional differentiation, provide evidence suggesting that similar biology--albeit imbalanced and exaggerated--is observed in breast cancer progression particularly during the transition from carcinoma in situ to invasive disease. Lastly we will present evidence suggesting that the multigene signatures currently used to model cancer heterogeneity and clinical outcome largely reflect signaling from a heterogeneous microenvironment-a recurring theme that could potentially be exploited therapeutically.

Germline copy number variants are not associated with globally acquired copy number changes in familial breast tumours

A characteristic of sporadic and familial breast tumours is genomic instability, resulting from either inherited mutations in genes that control genome integrity or mutations that are acquired in somatic cells during development. It is well established that abnormal chromosome number and structural changes to chromosomes play an important role in the cause and progression of breast cancer. Familial BRCA1 breast tumours are characterised by basal-like phenotype and high-histological grade which are typically associated with increased genomic instability. Consistent with previous studies, the genomes with the greatest number of base pairs covered by copy number change were typically found in basal-like and/or high-histological grade breast tumours within our cohort. Moreover, we show that luminal A tumours that are high grade had significantly less copy number variant (CNV) coverage than the more clinically aggressive high-grade luminal B tumours, suggesting that chromosomal instability rather than cellular differentiation contributes to the aggressive nature of luminal B tumours. It has previously been proposed that germline CNVs may contribute to somatically acquired chromosome changes in the tumour, but this is the first study to address this idea in breast cancer. By comparing germline CNVs and tumour-specific CNVs in matched breast tumour and normal tissue using data from the Illumina Human CNV370 duo beadarray, we provide evidence that germline CNVs do not tend to act as a foundation on which larger chromosome copy number aberrations develop in tumour cells. Further studies are required with increased sequence resolution that will detect smaller CNVs and define CNV breakpoints to comprehensively assess the relationship between inherited genomic variation and genome evolution in breast cancer.

Tumor heterogeneity: mechanisms and bases for a reliable application of molecular marker design

Tumor heterogeneity is a confusing finding in the assessment of neoplasms, potentially resulting in inaccurate diagnostic, prognostic and predictive tests. This tumor heterogeneity is not always a random and unpredictable phenomenon, whose knowledge helps designing better tests. The biologic reasons for this intratumoral heterogeneity would then be important to understand both the natural history of neoplasms and the selection of test samples for reliable analysis. The main factors contributing to intratumoral heterogeneity inducing gene abnormalities or modifying its expression include: the gradient ischemic level within neoplasms, the action of tumor microenvironment (bidirectional interaction between tumor cells and stroma), mechanisms of intercellular transference of genetic information (exosomes), and differential mechanisms of sequence-independent modifications of genetic material and proteins. The intratumoral heterogeneity is at the origin of tumor progression and it is also the byproduct of the selection process during progression. Any analysis of heterogeneity mechanisms must be integrated within the process of segregation of genetic changes in tumor cells during the clonal expansion and progression of neoplasms. The evaluation of these mechanisms must also consider the redundancy and pleiotropism of molecular pathways, for which appropriate surrogate markers would support the presence or not of heterogeneous genetics and the main mechanisms responsible. This knowledge would constitute a solid scientific background for future therapeutic planning.

Inflamm-aging of the stem cell niche: breast cancer as a paradigmatic example: breakdown of the multi-shell cytokine network fuels cancer in aged people

Inflamm-aging is a relatively new terminology used to describe the age-related increase in the systemic pro-inflammatory status of humans. Here, we represent inflamm-aging as a breakdown in the multi-shell cytokine network, in which stem cells and stromal fibroblasts (referred to as the stem cell niche) become pro-inflammatory cytokine over-expressing cells due to the accumulation of DNA damage. Inflamm-aging self-propagates owing to the capability of pro-inflammatory cytokines to ignite the DNA-damage response in other cells surrounding DNA-damaged cells. Macrophages, the major cellular player in inflamm-aging, amplify the phenomenon, by broadcasting pro-inflammatory signals at both local and systemic levels. On the basis of this, we propose that inflamm-aging is a major contributor to the increase in cancer incidence and progression in aged people. Breast cancer will be presented as a paradigmatic example for this relationship.

Cervical carcinoma-associated fibroblasts are DNA diploid and do not show evidence for somatic genetic alterations

Background

Cancer-associated fibroblasts (CAFs) have been recognized as important contributors to cancer development and progression. However, opposing evidence has been published whether CAFs, in addition to epigenetic, also undergo somatic genetic alterations and whether these changes contribute to carcinogenesis and tumour progression.

Methods

We combined multiparameter DNA flow cytometry, flow-sorting and 6K SNP-arrays to study DNA aneuploidy, % S-phase, loss of heterozygosity (LOH) and copy number alterations (CNAs) in cervical cancer-associated stromal cell fractions (n = 57) from formalin-fixed, paraffin-embedded (FFPE) samples. Tissue sections were examined for the presence of CAFs. Microsatellite analysis was used to confirm LOH findings.

Results

Smooth muscle actin and vimentin immunohistochemistry verified the presence of CAFs in all cases tested. However, we found no evidence for DNA aneuploidy, somatic genetic alterations in the vimentin-positive stromal cell fractions of any samples, while high frequencies of DNA content abnormalities (43/57) and substantial numbers of CNAs and LOH were identified in the keratin-positive epithelial cell fractions. LOH hot-spots on chromosomes 3p, 4p and 6p found were confirmed by microsatellite analysis.

Conclusion

From our study we conclude that stromal cell fractions from cervical carcinomas are DNA diploid, have a genotype undistinguishable from patient-matched normal tissue and are genetically stable. Using flow cytometry and SNP-arrays, stromal genetic changes do not seem to play a role during cervical carcinogenesis and progression. In addition, the stromal cell fraction of cervical carcinomas can be used as reference allowing large retrospective studies of archival FFPE tissues for which no normal reference tissue is available.

Electronic supplementary material

The online version of this article (doi:10.1007/s13402-011-0061-5) contains supplementary material, which is available to authorized users.

The Amazing Power of Cancer Cells to Recapitulate Extraembryonic Functions: The Cuckoo's Tricks

Inflammation is implicated in tumor development, invasion, and metastasis. Hence, it has been suggested that common cellular and molecular mechanisms are activated in wound repair and in cancer development. In addition, it has been previously proposed that the inflammatory response, which is associated with the wound healing process, could recapitulate ontogeny through the reexpression of the extraembryonic, that is, amniotic and vitelline, functions in the interstitial space of the injured tissue. If so, the use of inflammation by the cancer-initiating cell can also be supported in the ability to reacquire extraembryonic functional axes for tumor development, invasion, and metastasis. Thus, the diverse components of the tumor microenvironment could represent the overlapping reexpression of amniotic and vitelline functions. These functions would favor a gastrulation-like process, that is, the creation of a reactive stroma in which fibrogenesis and angiogenesis stand out.

Disease progression mechanism in myelodysplastic syndromes: insight into the role of the microenvironment

The somatic mutation theory proposing that a sequential accumulation of genetic abnormalities plays a major role in cancer pathogenesis has not yet been confirmed for myelodysplastic syndromes (MDS). Meanwhile, recent data in some cancers has underscored the role of the microenvironment in tumor growth. MDS CD34+CD38- cells usually fail to repopulate after transplantation in mice, suggesting the importance of the microenvironment for MDS cells. Our recent data have provided a disease-progression model in which overproduction of interferon-γ and tumor necrosis factor-α in the microenvironment is the primary event. This causes B7-H1 molecule expression on MDS blasts, which generates a bifunctional signal inducing T-cell apoptosis and enhancing blast proliferation. The latter may provide more opportunity for developing secondary genetic changes.

Prognostic gene-expression signature of carcinoma-associated fibroblasts in non-small cell lung cancer

The tumor microenvironment strongly influences cancer development, progression, and metastasis. The role of carcinoma-associated fibroblasts (CAFs) in these processes and their clinical impact has not been studied systematically in non-small cell lung carcinoma (NSCLC). We established primary cultures of CAFs and matched normal fibroblasts (NFs) from 15 resected NSCLC. We demonstrate that CAFs have greater ability than NFs to enhance the tumorigenicity of lung cancer cell lines. Microarray gene-expression analysis of the 15 matched CAF and NF cell lines identified 46 differentially expressed genes, encoding for proteins that are significantly enriched for extracellular proteins regulated by the TGF-β signaling pathway. We have identified a subset of 11 genes (13 probe sets) that formed a prognostic gene-expression signature, which was validated in multiple independent NSCLC microarray datasets. Functional annotation using protein-protein interaction analyses of these and published cancer stroma-associated gene-expression changes revealed prominent involvement of the focal adhesion and MAPK signaling pathways. Fourteen (30%) of the 46 genes also were differentially expressed in laser-capture-microdissected corresponding primary tumor stroma compared with the matched normal lung. Six of these 14 genes could be induced by TGF-β1 in NF. The results establish the prognostic impact of CAF-associated gene-expression changes in NSCLC patients.