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

Cell contractility drives mechanical memory of oral squamous cell carcinoma

Matrix stiffening is ubiquitous in solid tumors and can direct epithelial-mesenchymal transition (EMT) and cancer cell migration. Stiffened niche can even cause poorly invasive oral squamous cell carcinoma (OSCC) cell lines to acquire a less adherent, more migratory phenotype, but mechanisms and durability of this acquired "mechanical memory" are unclear. Here, we observed that contractility and its downstream signals could underlie memory acquisition; invasive SSC25 cells overexpress myosin II (vs. noninvasive Cal27 cells) consistent with OSCC. However, prolonged exposure of Cal27 cells to a stiff niche or contractile agonists up-regulated myosin and EMT markers and enabled them to migrate as fast as SCC25 cells, which persisted even when the niche softened and indicated "memory" of their prior niche. Stiffness-mediated mesenchymal phenotype acquisition required AKT signaling and was also observed in patient samples, whereas phenotype recall on soft substrates required focal adhesion kinase (FAK) activity. Phenotype durability was further observed in transcriptomic differences between preconditioned Cal27 cells cultured without or with FAK or AKT antagonists, and such transcriptional differences corresponded to discrepant patient outcomes. These data suggest that mechanical memory, mediated by contractility via distinct kinase signaling, may be necessary for OSCC to disseminate.

Interplay between tumor-derived factors and tumor-associated neutrophils: opportunities for therapeutic interventions in cancer

Neutrophils have emerged as important players in the tumor microenvironment, largely attributed to their plasticity and heterogeneity. Evidence accumulated thus far indicates that neutrophils signaled by external cues can promote tumor progression via several mechanisms. Hence, in our quest to target tumor-associated neutrophils to improve treatment, understanding the mechanisms by which tumor-derived factors regulate neutrophils to gain pro-tumor functions and the feedback loop by which these neutrophils promote tumor progression is very crucial. Herein, we review the published data on how tumor-derived factors alter neutrophils phenotype to promote tumor progression with particular emphasis on immunosuppression, autophagy, angiogenesis, tumor proliferation, metastasis, and therapeutic resistance. These deeper insights could provide a wider view and novel therapeutic approach to neutrophil-targeted therapy in cancer.

Development and Validation of Ferroptosis- and Immune-Related lncRNAs Signatures for Breast Infiltrating Duct and Lobular Carcinoma

Background

Heterogeneity of breast cancer (BRCA) is significantly correlated with its prognosis. Target therapy for ferroptosis and immunity is a new cancer treatment option discovered in recent years. In the present study, we aimed to identify ferroptosis- and immune-related long non-coding RNAs (lncRNAs) to accurately predict the prognosis and diagnosis of patients with breast infiltrating duct and lobular carcinoma by integrated analyses.

Methods

The corresponding data for the patients with breast infiltrating duct and lobular carcinoma by integrated analyses were obtained from The Cancer Genome Atlas (TCGA). Analyses of univariate and multivariate Cox regressions were used to identify the suitable candidate biomarkers.

Results

We found that seven ferroptosis- and immune-related differentially expressed lncRNAs (FI-DELs) (AC007686.3, AC078883.1, ADAMTS9-AS1, AL035661.1, CBR3-AS1, FTX, and TMEM105) were correlated with the overall survival of patients with breast infiltrating duct and lobular carcinoma. The areas under the receiver operating characteristic (AUCs) value of the prognosis model were all over 0.6 in training, validation, and entire groups. The sensitivity and specificity of the diagnosis model was 87.84% and 97.06%, respectively.

Conclusions

Through a series of bioinformatics analyses, we found that the seven FI-DELs could serve as prognostic and diagnostic biomarkers for patients with breast infiltrating duct and lobular carcinoma. However, whether these seven biomarkers could be really applied to the clinic requires further investigations.

A uracil auxotroph Toxoplasma gondii exerting immunomodulation to inhibit breast cancer growth and metastasis

BACKGROUND

Breast cancer is the most common cause of cancer-related death among women, and prognosis is especially poor for patients with triple-negative breast cancer (TNBC); therefore, there is an urgent need for new effective therapies. Recent studies have demonstrated that the uracil auxotroph Toxoplasma gondii vaccine displays anti-tumor effects. Here, we examined the immunotherapy effects of an attenuated uracil auxotroph strain of T. gondii against 4T1 murine breast cancer.

METHODS

We constructed a uracil auxotroph T. gondii RH strain via orotidine 5'-monophosphate decarboxylase gene deletion (RH-Δompdc) with CRISPR/Cas9 technology. The strain's virulence in the T. gondii-infected mice was determined in vitro and in vivo by parasite replication assay, plaque assay, parasite burden detection in mice peritoneal fluids and survival analysis. The immunomodulation ability of the strain was evaluated by cytokine detection. Its anti-tumor effect was evaluated after its in situ inoculation into 4T1 tumors in a mouse model; the tumor volume was measured, and the 4T1 lung metastasis was detected by hematoxylin and eosin and Ki67 antibody staining, and the cytokine levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

The RH-Δompdc strain proliferated normally when supplemented with uracil, but it was unable to propagate without the addition of uracil and in vivo, which suggested that it was avirulent to the hosts. This mutant showed vaccine characteristics that could induce intense immune responses both in vitro and in vivo by significantly boosting the expression of inflammatory cytokines. Inoculation of RH-Δompdc in situ into the 4T1 tumor inhibited tumor growth, reduced lung metastasis, promoted the survival of the tumor-bearing mice and increased the secretion of Th1 cytokines, including interleukin-12 (IL-12) and interferon-γ (INF-δ), in both the serum and tumor microenvironment (TME).

CONCLUSION

Inoculation of the uracil auxotroph RH-Δompdc directly into the 4T1 tumor stimulated anti-infection and anti-tumor immunity in mice, and resulted in inhibition of tumor growth and metastasis, promotion of the survival of the tumor-bearing mice and increased secretion of IL-12 and IFN-γ in both the serum and TME. Our findings suggest that the immunomodulation caused by RH-Δompdc could be a potential anti-tumor strategy.

Association of Pharyngocutaneous Fistula With Cancer Outcomes in Patients After Laryngectomy: A Multicenter Collaborative Cohort Study

Importance

Pharyngocutaneous fistula (PCF) results in an inflammatory reaction, but its association with the rate of locoregional and distant control, disease-free survival, and overall survival in laryngeal cancer remains uncertain.

Objective

To determine if pharyngocutaneous fistula after salvage laryngectomy is associated with locoregional and distant control, disease-free survival, and/or overall survival.

Design, Setting, and Participants

A multicenter collaborative retrospective cohort study conducted at 5 centers in Canada and the US of 550 patients who underwent salvage laryngectomy for recurrent laryngeal cancer from January 1, 2000, to December 31, 2014. The median follow-up time was 5.7 years (range, 0-18 years).

Main Outcomes and Measures

Outcomes examined included locoregional and distant control, disease-free survival, and overall survival. Fine and Gray competing risk regression and Cox-proportional hazard regression models were used for outcomes. Competing risks and the Kaplan-Meier methods were used to estimate outcomes at 3 years and 5 years.

Results

In all, 550 patients (mean [SD] age, 64 [10.4] years; men, 465 [85%]) met inclusion criteria. Pharyngocutaneous fistula occurred in 127 patients (23%). The difference in locoregional control between the group of patients with PCF (75%) and the non-PCF (72%) group was 3% (95% CI, -6% to 12%). The difference in overall survival between the group with PCF (44%) and the non-PCF group (52%) was 8% (95% CI, -2% to 20%). The difference in disease-free survival between PCF and non-PCF groups was 6% (95% CI, -4% to 16%). In the multivariable model, patients with PCF were at a 2-fold higher rate of distant metastases (hazard ratio, 2.00; 95% CI, 1.22 to 3.27). Distant control was reduced in those with PCF, a 13% (95% CI, 3% to 21%) difference in 5-year distant control.

Conclusions and Relevance

This multicenter retrospective cohort study found that development of PCF after salvage laryngectomy is associated with an increased risk for the development of distant metastases.

A Complex and Evolutive Character: Two Face Aspects of ECM in Tumor Progression

Tumor microenvironment, including extracellular matrix (ECM) and stromal cells, is a key player during tumor development, from initiation, growth and progression to metastasis. During all of these steps, remodeling of matrix components occurs, changing its biochemical and physical properties. The global and basic cancer ECM model is that tumors are surrounded by activated stromal cells, that remodel physiological ECM to evolve into a stiffer and more crosslinked ECM than in normal conditions, thereby increasing invasive capacities of cancer cells. In this review, we show that this too simple model does not consider the complexity, specificity and heterogeneity of each organ and tumor. First, we describe the general ECM in context of cancer. Then, we go through five invasive and most frequent cancers from different origins (breast, liver, pancreas, colon, and skin), and show that each cancer has its own specific matrix, with different stromal cells, ECM components, biochemical properties and activated signaling pathways. Furthermore, in these five cancers, we describe the dual role of tumor ECM: as a protective barrier against tumor cell proliferation and invasion, and as a major player in tumor progression. Indeed, crosstalk between tumor and stromal cells induce changes in matrix organization by remodeling ECM through invadosome formation in order to degrade it, promoting tumor progression and cell invasion. To sum up, in this review, we highlight the specificities of matrix composition in five cancers and the necessity not to consider the ECM as one general and simple entity, but one complex, dynamic and specific entity for each cancer type and subtype.

The relationship between post-surgery infection and breast cancer recurrence

Breast cancer is the second most prevalent form of cancer in women worldwide, with surgery remaining the standard treatment. The adverse impact of the surgery remains controversial. It has been suggested that systemic factors during the postoperative period may increase the risk of recurrence, specifically surgical site infection (SSI). The aim of this review was to critically appraise current published literature regarding the influence of SSIs, after primary breast cancer surgery, on breast cancer recurrence, and to delve into potential links between these. This systematic review adopted two approaches: to identify the incidence rates and risk factors related to SSI after primary breast cancer surgery; and, secondly, to examine breast cancer recurrence following SSI occurrence. Ninety-nine studies with 484,605 patients were eligible in the SSI-focused searches, and 53 studies with 17,569 patients for recurrence-focused. There was a 13.07% mean incidence of SSI. Six-hundred and thirty-eight Gram-positive and 442 Gram-negative isolates were identified, with methicillin-susceptible Staphylococcus aureus and Escherichia coli most commonly identified. There were 2077 cases of recurrence (11.8%), with 563 cases of local recurrence, 1186 cases of distant and 25 cases which recurred both locally and distantly. Five studies investigated the association between SSI and breast cancer recurrence with three concluding that an association did exist. In conclusion, there is association between SSI and adverse cancer outcomes, but the cellular link between them remains elusive. Confounding factors of retrospective study design, surgery type and SSI definition make results challenging to compare and interpret. A standardized prospective study with appropriate statistical power is justified.

ROCK-mediated selective activation of PERK signalling causes fibroblast reprogramming and tumour progression through a CRELD2-dependent mechanism

It is well accepted that cancers co-opt the microenvironment for their growth. However, the molecular mechanisms that underlie cancer-microenvironment interactions are still poorly defined. Here, we show that Rho-associated kinase (ROCK) in the mammary tumour epithelium selectively actuates protein-kinase-R-like endoplasmic reticulum kinase (PERK), causing the recruitment and persistent education of tumour-promoting cancer-associated fibroblasts (CAFs), which are part of the cancer microenvironment. An analysis of tumours from patients and mice reveals that cysteine-rich with EGF-like domains 2 (CRELD2) is the paracrine factor that underlies PERK-mediated CAF education downstream of ROCK. We find that CRELD2 is regulated by PERK-regulated ATF4, and depleting CRELD2 suppressed tumour progression, demonstrating that the paracrine ROCK-PERK-ATF4-CRELD2 axis promotes the progression of breast cancer, with implications for cancer therapy.

Breast cancer

Breast cancer is the most frequent malignancy in women worldwide and is curable in ~70-80% of patients with early-stage, non-metastatic disease. Advanced breast cancer with distant organ metastases is considered incurable with currently available therapies. On the molecular level, breast cancer is a heterogeneous disease; molecular features include activation of human epidermal growth factor receptor 2 (HER2, encoded by ERBB2), activation of hormone receptors (oestrogen receptor and progesterone receptor) and/or BRCA mutations. Treatment strategies differ according to molecular subtype. Management of breast cancer is multidisciplinary; it includes locoregional (surgery and radiation therapy) and systemic therapy approaches. Systemic therapies include endocrine therapy for hormone receptor-positive disease, chemotherapy, anti-HER2 therapy for HER2-positive disease, bone stabilizing agents, poly(ADP-ribose) polymerase inhibitors for BRCA mutation carriers and, quite recently, immunotherapy. Future therapeutic concepts in breast cancer aim at individualization of therapy as well as at treatment de-escalation and escalation based on tumour biology and early therapy response. Next to further treatment innovations, equal worldwide access to therapeutic advances remains the global challenge in breast cancer care for the future.

The Calcium-Signaling Toolkit in Cancer: Remodeling and Targeting

Processes that are important in cancer progression, such as sustained cell growth, invasion to other organs, and resistance to cell death inducers, have a clear overlap with pathways regulated by Ca²⁺ signaling. It is therefore not surprising that proteins important in Ca²⁺ signaling, sometimes referred to as the "Ca²⁺ signaling toolkit," can contribute to cancer cell proliferation and invasiveness, and the ability of agents to induce cancer cell death. Ca²⁺ signaling is also critical in other aspects of cancer progression, including events in the tumor microenvironment and processes involved in the acquisition of resistance to anticancer therapies. This review will consider the role of Ca²⁺ signaling in tumor progression and highlight areas in which a better understanding of the interplay between the Ca²⁺-signaling toolkit and tumorigenesis is still required.

Original association of ion transporters mediates the ECM-induced breast cancer cell survival: Kv10.1-Orai1-SPCA2 partnership

In the last years it has been shown that many components of tumor microenvironment (TM) can induce cell signaling that permit to breast cancer cells (BC) to maintain their aggressiveness. Ion channels have a role in mediating TM signal; recently we have demonstrated a functional collaboration between Kv10.1 and Orai1 channels in mediating the pro-survival effect of collagen 1 on BC cells. Here we show how SPCA2 (Secretory Pathway Ca²⁺ ATPase) has a role in this process and is able to support survival and proliferation induced by collagen 1. By participating to an auto-sustaining loop, SPCA2 enhances membrane expression of Kv10.1 and Orai1; the activity of every component of this trio is necessary to mediate a store independent calcium entry (SICE). This SICE is fundamental to maintain both the activation of the pro-survival pathway and the membrane localization and consequently the activity of the two channels. Moreover, the three proteins and the collagen receptor DDR1 are overexpressed only in aggressive tumors tissues. In this work, we propose a novel association between SPCA2, Kv10.1 and Orai1 involved in mediating transduction signals from TM to the BC cells that can be potentially exploited in the search of novel therapeutic targets specific to tumor tissues.

Prolyl-4-hydroxylase Α subunit 2 (P4HA2) expression is a predictor of poor outcome in breast ductal carcinoma in situ (DCIS)

Background

Extracellular matrix (ECM) plays a crucial role in tumour behaviour. Prolyl-4-hydroxlase-A2 (P4HA2) is a key enzyme in ECM remodelling. This study aims to evaluate the prognostic significance of P4HA2 in breast ductal carcinoma in situ (DCIS).

Methods

P4HA2 expression was assessed immunohistochemically in malignant cells and surrounding stroma of a large DCIS cohort comprising 481 pure DCIS and 196 mixed DCIS and invasive carcinomas. Outcome analysis was evaluated using local recurrence free interval (LRFI).

Results

High P4HA2 expression was detected in malignant cells of half of pure DCIS whereas its expression in stroma was seen in 25% of cases. Higher P4HA2 expression was observed in mixed DCIS cases compared to pure DCIS both in tumour cells and in stroma. High P4HA2 was associated with features of high risk DCIS including younger age, higher grade, comedo necrosis, triple negative and HER2-positive phenotypes. Interaction between P4HA2 and radiotherapy was also observed regarding the outcome. High P4HA2 expression was an independent prognostic factor in predicting shorter LRFI.

Conclusion

P4HA2 plays a role in DCIS progression and can potentially be used to predict DCIS outcome. Incorporation of P4HA2 with other clinicopathological parameters could refine DCIS risk stratification that can potentially guide management decisions.

Calcium signaling and the therapeutic targeting of cancer cells

The calcium signal is implicated in a variety of processes important in tumor progression (e.g. proliferation and invasiveness). The calcium signal has also been shown to be important in other processes important in cancer progression including the development of resistance to current cancer therapies. In this review, we discuss how Ca²⁺ channels, pumps and exchangers may be drug targets in some cancer types. We consider what factors should be taken into account when considering an optimal Ca²⁺ channel, pump or exchanger as a candidate for further assessment as a novel drug target in cancer. We also present and summarize how some therapies for the treatment of cancer intersect with Ca²⁺ signaling and how pharmacological manipulation of the machinery of Ca²⁺ signaling could promote the effectiveness of some therapies. We also review new therapeutic opportunities for Ca²⁺ signal modulators in the context of the tumor microenvironment.

Ionizing radiation-mediated premature senescence and paracrine interactions with cancer cells enhance the expression of syndecan 1 in human breast stromal fibroblasts: the role of TGF-β

The cell surface proteoglycan syndecan 1 (SDC1) is overexpressed in the malignant breast stromal fibroblasts, creating a favorable milieu for tumor cell growth. In the present study, we found that ionizing radiation, a well-established treatment in human breast cancer, provokes premature senescence of human breast stromal fibroblasts in vitro, as well as in the breast tissue in vivo. These senescent cells were found to overexpress SDC1 both in vitro and in vivo. By using a series of specific inhibitors and siRNA approaches, we showed that this SDC1 overexpression in senescent cells is the result of an autocrine action of Transforming Growth Factor-β (TGF-β) through the Smad pathway and the transcription factor Sp1, while the classical senescence pathways of p53 or p38 MAPK - NF-kB are not involved. In addition, the highly invasive human breast cancer cells MDA-MB-231 (in contrast to the low-invasive MCF-7) can also enhance SDC1 expression, both in early-passage and senescent fibroblasts via a paracrine action of TGF-β. The above suggest that radiation-mediated premature senescence and invasive tumor cells, alone or in combination, enhance SDC1 expression in breast stromal fibroblasts, a poor prognostic factor for cancer growth, and that TGF-β plays a crucial role in this process.

Data-driven analysis of immune infiltrate in a large cohort of breast cancer and its association with disease progression, ER activity, and genomic complexity

The tumor microenvironment is now widely recognized for its role in tumor progression, treatment response, and clinical outcome. The intratumoral immunological landscape, in particular, has been shown to exert both pro-tumorigenic and anti-tumorigenic effects. Identifying immunologically active or silent tumors may be an important indication for administration of therapy, and detecting early infiltration patterns may uncover factors that contribute to early risk. Thus far, direct detailed studies of the cell composition of tumor infiltration have been limited; with some studies giving approximate quantifications using immunohistochemistry and other small studies obtaining detailed measurements by isolating cells from excised tumors and sorting them using flow cytometry. Herein we utilize a machine learning based approach to identify lymphocyte markers with which we can quantify the presence of B cells, cytotoxic T-lymphocytes, T-helper 1, and T-helper 2 cells in any gene expression data set and apply it to studies of breast tissue. By leveraging over 2,100 samples from existing large scale studies, we are able to find an inherent cell heterogeneity in clinically characterized immune infiltrates, a strong link between estrogen receptor activity and infiltration in normal and tumor tissues, changes with genomic complexity, and identify characteristic differences in lymphocyte expression among molecular groupings. With our extendable methodology for capturing cell type specific signal we systematically studied immune infiltration in breast cancer, finding an inverse correlation between beneficial lymphocyte infiltration and estrogen receptor activity in normal breast tissue and reduced infiltration in estrogen receptor negative tumors with high genomic complexity.

Normal mammary epithelial cells promote carcinoma basement membrane invasion by inducing microtubule-rich protrusions

Recent work suggests that the dissemination of tumor cells may occur in parallel with, and even preceed, tumor growth. The mechanism for this early invasion is largely unknown. Here, we find that mammary epithelial cells (MECs) induce neighboring breast carcinoma cells (BCCs) to cross the basement membrane by secreting soluble laminin. Laminin continuously produced by MECs induce long membrane cellular protrusions in BCCs that promote their contractility and invasion into the surrounding matrix. These protrusions depend on microtubule bundles assembled de novo through laminin-integrin β1 signaling. These results describe how non-cancerous MECs can actively participate in the invasive process of BCCs.

Social networking in tumor cell communities is associated with increased aggressiveness

Extracellular vesicles (EVs) are lipid-bilayer-enclosed vesicles that contain proteins, lipids and nucleic acids. EVs produced by cells from healthy tissues circulate in the blood and body fluids, and can be taken up by unrelated cells. As they have the capacity to transfer cargo proteins, lipids and nucleic acids (mostly mRNAs and miRNAs) between different cells in the body, EVs are emerging as mediators of intercellular communication that could modulate cell behavior, tissue homeostasis and regulation of physiological functions. EV-mediated cell-cell communications are also proposed to play a role in disease, for example, cancer, where they could contribute to transfer of traits required for tumor progression and metastasis. However, direct evidence for EV-mediated mRNA transfer to individual cells and for its biological consequences in vivo has been missing until recently. Recent studies have reported elegant experiments using genetic tracing with the Cre recombinase system and intravital imaging that visualize and quantify functional transfer of mRNA mediated by EVs in the context of cancer and metastasis.

Breast Cancer/Stromal Cells Coculture on Polyelectrolyte Films Emulates Tumor Stages and miRNA Profiles of Clinical Samples

In this study, we demonstrate a method for controlling breast cancer cells adhesion on polyelectrolyte multilayer (PEM) films without the aid of adhesive proteins/ligands to study the role of tumor and stromal cell interaction on cancer biology. Numerous studies have explored engineering coculture of tumor and stromal cells predominantly using transwell coculture of stromal cells cultured onto coverslips that were subsequently added to tumor cell cultures. However, these systems imposed an artificial boundary that precluded cell-cell interactions. To our knowledge, this is the first demonstration of patterned coculture of tumor cells and stromal cells that captures the temporal changes in the miRNA signature as the breast tumor develops through various stages. In our study we used synthetic polymers, namely poly(diallyldimethylammonium chloride) (PDAC) and sulfonated poly(styrene) (SPS), as the polycation and polyanion, respectively, to build PEMs. Breast cancer cells attached and spread preferentially on SPS surfaces while stromal cells attached to both SPS and PDAC surfaces. SPS patterns were formed on PEM surfaces, by either capillary force lithography (CFL) of SPS onto PDAC surfaces or vice versa, to obtain patterns of breast cancer cells and patterned cocultures of breast cancer and stromal cells. In this study, we utilized cancer cells derived from two different tumor stages and two different stromal cells to effectively model a heterogeneous tumor microenvironment and emulate various tumor stages. The coculture model mimics the proliferative index (Ki67 expression) and tumor aggressiveness (HER-2 expression) akin to those observed in clinical tumor samples. We also demonstrated that our patterned coculture model captures the temporal changes in the miRNA-21 and miRNA-34 signature as the breast tumor develops through various stages. The engineered coculture platform lays groundwork toward precision medicine wherein patient-derived tumor cells can be incorporated within our in vitro models to identify potential pathways and drug treatment regimens for individual patients.

Extensive rewiring of epithelial-stromal co-expression networks in breast cancer

BACKGROUND

Epithelial-stromal crosstalk plays a critical role in invasive breast cancer pathogenesis; however, little is known on a systems level about how epithelial-stromal interactions evolve during carcinogenesis.

RESULTS

We develop a framework for building genome-wide epithelial-stromal co-expression networks composed of pairwise co-expression relationships between mRNA levels of genes expressed in the epithelium and stroma across a population of patients. We apply this method to laser capture micro-dissection expression profiling datasets in the setting of breast carcinogenesis. Our analysis shows that epithelial-stromal co-expression networks undergo extensive rewiring during carcinogenesis, with the emergence of distinct network hubs in normal breast, and estrogen receptor-positive and estrogen receptor-negative invasive breast cancer, and the emergence of distinct patterns of functional network enrichment. In contrast to normal breast, the strongest epithelial-stromal co-expression relationships in invasive breast cancer mostly represent self-loops, in which the same gene is co-expressed in epithelial and stromal regions. We validate this observation using an independent laser capture micro-dissection dataset and confirm that self-loop interactions are significantly increased in cancer by performing computational image analysis of epithelial and stromal protein expression using images from the Human Protein Atlas.

CONCLUSIONS

Epithelial-stromal co-expression network analysis represents a new approach for systems-level analyses of spatially localized transcriptomic data. The analysis provides new biological insights into the rewiring of epithelial-stromal co-expression networks and the emergence of epithelial-stromal co-expression self-loops in breast cancer. The approach may facilitate the development of new diagnostics and therapeutics targeting epithelial-stromal interactions in cancer.

The hypoxic tumor microenvironment: A driving force for breast cancer progression

Intratumoral hypoxia is a common finding in breast cancer and is associated with a significantly increased risk of metastasis and patient mortality. Hypoxia-inducible factors activate the transcription of a large battery of genes encoding proteins that promote primary tumor vascularization and growth, stromal cell recruitment, extracellular matrix remodeling, premetastatic niche formation, cell motility, local tissue invasion, extravasation at sites of metastasis, and maintenance of the cancer stem cell phenotype that is required to generate secondary tumors. Recent preclinical studies suggest that the combination of cytotoxic chemotherapy with drugs that inhibit hypoxia-inducible factors may improve outcome for women with triple-negative breast cancer. This article is part of a Special Issue entitled: Tumor Microenvironment Regulation of Cancer Cell Survival, Metastasis, Inflammation, and Immune Surveillance edited by Peter Ruvolo and Gregg L. Semenza.

Yes-associated protein regulates the growth of human non-small cell lung cancer in response to matrix stiffness

The Yes‑associated protein (YAP) transcriptional coactivator is recognized as a crucial regulator of human cancer. However, its involvement in human non‑small cell lung cancer (NSCLC) in response to physical cues remains unclear. In this study, substrates with different rigidity were generated in order to evaluate the role of YAP, and its upstream regulators in the Hippo pathway, in the regulation of growth of an NSCLC cell line within particular environments. It was shown that the expression of the YAP protein in SPCA-1 NSCLC cells was significantly increased when cultured on a stiff substrate compared to a soft substrate. However, the expression of phospho‑YAP protein and large tumor suppressor kinase 1 (LATS1) were markedly decreased after culturing on the stiff substrate. Phosphorylation of YAP by LATS1 leads to cytoplasmic retention of YAP, which inhibits its function as a nuclear transcription coactivator. The study also found that the stiff substrate promoted the growth of NSCLC cells in vitro, and an increase in the transcription levels of Survivin, connective tissue growth factor, amphiregulin and Ki67, as well as a decrease in the expression level of YAP in the cytoplasm, and adecrease in p-YAP. In conclusion, the findings showed that the stiffness of the subcellular matrix altered the behavior of NSCLC cells, and that YAP regulated the growth of NSCLC cells in response to matrix stiffness, thereby suggesting a role for the Hippo‑YAP pathway in the response of NSCLC cell growth to specific microenvironments.

A simple and rapid protocol to non-enzymatically dissociate fresh human tissues for the analysis of infiltrating lymphocytes

The ability of malignant cells to evade the immune system, characterized by tumor escape from both innate and adaptive immune responses, is now accepted as an important hallmark of cancer. Our research on breast cancer focuses on the active role that tumor infiltrating lymphocytes play in tumor progression and patient outcome. Toward this goal, we developed a methodology for the rapid isolation of intact lymphoid cells from normal and abnormal tissues in an effort to evaluate them proximate to their native state. Homogenates prepared using a mechanical dissociator show both increased viability and cell recovery while preserving surface receptor expression compared to enzyme-digested tissues. Furthermore, enzymatic digestion of the remaining insoluble material did not recover additional CD45(+) cells indicating that quantitative and qualitative measurements in the primary homogenate likely genuinely reflect infiltrating subpopulations in the tissue fragment. The lymphoid cells in these homogenates can be easily characterized using immunological (phenotype, proliferation, etc.) or molecular (DNA, RNA and/or protein) approaches. CD45(+) cells can also be used for subpopulation purification, in vitro expansion or cryopreservation. An additional benefit of this approach is that the primary tissue supernatant from the homogenates can be used to characterize and compare cytokines, chemokines, immunoglobulins and antigens present in normal and malignant tissues. This protocol functions extremely well for human breast tissues and should be applicable to a wide variety of normal and abnormal tissues.

New exposure biomarkers as tools for breast cancer epidemiology, biomonitoring, and prevention: a systematic approach based on animal evidence

BACKGROUND

Exposure to chemicals that cause rodent mammary gland tumors is common, but few studies have evaluated potential breast cancer risks of these chemicals in humans.

OBJECTIVE

The goal of this review was to identify and bring together the needed tools to facilitate the measurement of biomarkers of exposure to potential breast carcinogens in breast cancer studies and biomonitoring.

METHODS

We conducted a structured literature search to identify measurement methods for exposure biomarkers for 102 chemicals that cause rodent mammary tumors. To evaluate concordance, we compared human and animal evidence for agents identified as plausibly linked to breast cancer in major reviews. To facilitate future application of exposure biomarkers, we compiled information about relevant cohort studies.

RESULTS

Exposure biomarkers have been developed for nearly three-quarters of these rodent mammary carcinogens. Analytical methods have been published for 73 of the chemicals. Some of the remaining chemicals could be measured using modified versions of existing methods for related chemicals. In humans, biomarkers of exposure have been measured for 62 chemicals, and for 45 in a nonoccupationally exposed population. The Centers for Disease Control and Prevention has measured 23 in the U.S. population. Seventy-five of the rodent mammary carcinogens fall into 17 groups, based on exposure potential, carcinogenicity, and structural similarity. Carcinogenicity in humans and rodents is generally consistent, although comparisons are limited because few agents have been studied in humans. We identified 44 cohort studies, with a total of > 3.5 million women enrolled, that have recorded breast cancer incidence and stored biological samples.

CONCLUSIONS

Exposure measurement methods and cohort study resources are available to expand biomonitoring and epidemiology related to breast cancer etiology and prevention.

Cellular heterogeneity profiling by hyaluronan probes reveals an invasive but slow-growing breast tumor subset

Tumor heterogeneity confounds cancer diagnosis and the outcome of therapy, necessitating analysis of tumor cell subsets within the tumor mass. Elevated expression of hyaluronan (HA) and HA receptors, receptor for HA-mediated motility (RHAMM)/HA-mediated motility receptor and cluster designation 44 (CD44), in breast tumors correlates with poor outcome. We hypothesized that a probe for detecting HA-HA receptor interactions may reveal breast cancer (BCa) cell heterogeneity relevant to tumor progression. A fluorescent HA (F-HA) probe containing a mixture of polymer sizes typical of tumor microenvironments (10-480 kDa), multiplexed profiling, and flow cytometry were used to monitor HA binding to BCa cell lines of different molecular subtypes. Formulae were developed to quantify binding heterogeneity and to measure invasion in vivo. Two subsets exhibiting differential binding (HA(-/low) vs. HA(high)) were isolated and characterized for morphology, growth, and invasion in culture and as xenografts in vivo. F-HA-binding amounts and degree of heterogeneity varied with BCa subtype, were highest in the malignant basal-like cell lines, and decreased upon reversion to a nonmalignant phenotype. Binding amounts correlated with CD44 and RHAMM displayed but binding heterogeneity appeared to arise from a differential ability of HA receptor-positive subpopulations to interact with F-HA. HA(high) subpopulations exhibited significantly higher local invasion and lung micrometastases but, unexpectedly, lower proliferation than either unsorted parental cells or the HA(-/low) subpopulation. Querying F-HA binding to aggressive tumor cells reveals a previously undetected form of heterogeneity that predicts invasive/metastatic behavior and that may aid both early identification of cancer patients susceptible to metastasis, and detection/therapy of invasive BCa subpopulations.

Extracellular matrix signatures of human mammary carcinoma identify novel metastasis promoters

The extracellular matrix (ECM) is a major component of tumors and a significant contributor to cancer progression. In this study, we use proteomics to investigate the ECM of human mammary carcinoma xenografts and show that primary tumors of differing metastatic potential differ in ECM composition. Both tumor cells and stromal cells contribute to the tumor matrix and tumors of differing metastatic ability differ in both tumor- and stroma-derived ECM components. We define ECM signatures of poorly and highly metastatic mammary carcinomas and these signatures reveal up-regulation of signaling pathways including TGFβ and VEGF. We further demonstrate that several proteins characteristic of highly metastatic tumors (LTBP3, SNED1, EGLN1, and S100A2) play causal roles in metastasis, albeit at different steps. Finally we show that high expression of LTBP3 and SNED1 correlates with poor outcome for ER⁻/PR⁻breast cancer patients. This study thus identifies novel biomarkers that may serve as prognostic and diagnostic tools.

DOI:http://dx.doi.org/10.7554/eLife.01308.001

Metastasis is the process whereby tumor cells spread within the body and is the cause of most deaths from cancer. This complex process involves several steps: first the cancer cells invade the tissues that surround the tumor; second, the cancer cells enter the blood stream and travel throughout the body; and third, the cancer cells seed the growth of new tumors in distant organs.

Within tissues, the extracellular matrix forms a complex scaffold of proteins that surrounds cells, to support and organize them: it also provides signals that control how much cells can multiply, how likely cells are to stick together or migrate, and even a cell’s chances of survival. Pathologists have used an accumulation of extracellular matrix proteins in tumors as a sign that the outcome of the disease will likely be unfavorable for a patient, and that treatment will be challenging. However, we still do not have a clear picture of the composition of the tumor extracellular matrix and we do not know all the details of how it affects tumor growth and metastasis.

Now, Naba et al. have explored these questions by injecting different types of human breast tumor cells into mice. Some of the cells were capable of spreading throughout the body and were said to have a high ‘metastatic potential’; others were less capable of spreading and were said to have a low metastatic potential. Naba et al. then analyzed the proteins that made up the extracellular matrix of the tumors that grew in the mice. Some proteins were found in both types of tumor; whereas some proteins were only found in the tumors with low metastatic potential and some were only found in the highly metastatic tumors. Naba et al. also demonstrated that both cancer cells and non-cancer cells—which are also found within the tumors—contributed to the production of the extracellular matrix in the tumor. Moreover, and somewhat surprisingly, the contributions from the non-cancer cells in the two types of tumors were also different.

Computational analysis predicted that the production of several extracellular matrix proteins in the highly metastatic tumors was under the control of signaling pathways that are involved in cancer progression. Furthermore, Naba et al. also demonstrated that several of the extracellular matrix proteins specific to highly metastatic tumors were required for the cancer to spread. These proteins are involved in different stages of the metastatic process, and some of them are commonly over-produced in tumors from patients with some of the worst chances of recovery.

If similar results are consistently observed in clinical samples from humans, the work of Naba et al. could help doctors to discriminate between tumors that will spread and those that will not, which should lead to improved patient care. The proteins and pathways associated with the highly metastatic tumors could be also investigated as potential drug targets.

DOI:http://dx.doi.org/10.7554/eLife.01308.002

CX3CL1 promotes breast cancer via transactivation of the EGF pathway

Chemokines are relevant molecules in shaping the tumor microenvironment, although their contributions to tumorigenesis are not fully understood. We studied the influence of the chemokine CX3CL1/fractalkine in de novo breast cancer formation using HER2/neu transgenic mice. CX3CL1 expression was downmodulated in HER2/neu tumors, yet, paradoxically, adenovirus-mediated CX3CL1 expression in the tumor milieu enhanced mammary tumor numbers in a dose-dependent manner. Increased tumor multiplicity was not a consequence of CX3CL1-induced metastatic dissemination of the primary tumor, although CX3CL1 induced epithelial-to-mesenchymal transition in breast cancer cells in vitro. Instead, CX3CL1 triggered cell proliferation by induction of ErbB receptors through the proteolytic shedding of an ErbB ligand. This effect was important insofar as mammary tumorigenesis was delayed and tumor multiplicity was reduced by genetic deletion of CX3CL1 in HER2/neu mice, but not in polyoma middle T-antigen oncomice. Our findings support the conclusion that CX3CL1 acts as a positive modifier of breast cancer in concert with ErbB receptors.

Tumor microenvironment indoctrination: an emerging hallmark of cancer

Nastiness of cancer does not only reside in the corruption of cancer cells by genetic aberrations that drive their sustained proliferative power--the roots of malignancy--but also in its aptitude to reciprocally sculpt its surrounding environment and cellular stromal ecosystem, in such a way that the corrupted tumor microenvironment becomes a full pro-tumorigenic entity. Such a contribution had been appreciated three decades ago already, with the discovery of tumor angiogenesis and extracellular matrix remodeling. Nevertheless, the recent emergence of the tumor microenvironment as the critical determinant in cancer biology is paralleled by the promising therapeutic potential it carries, opening alternate routes to fight cancer. The study of the tumor microenvironment recruited numerous lead-scientists over the years, with distinct perspectives, and some of them have kindly accepted to contribute to the elaboration of this special issue entitled Tumor microenvironment indoctrination: An emerging hallmark of cancer.