Influence of tumour micro-environment heterogeneity on therapeutic response

Patient-derived tumour xenografts for breast cancer drug discovery

Despite remarkable advances in our understanding of the drivers of human malignancies, new targeted therapies often fail to show sufficient efficacy in clinical trials. Indeed, the cost of bringing a new agent to market has risen substantially in the last several decades, in part fuelled by extensive reliance on preclinical models that fail to accurately reflect tumour heterogeneity. To halt unsustainable rates of attrition in the drug discovery process, we must develop a new generation of preclinical models capable of reflecting the heterogeneity of varying degrees of complexity found in human cancers. Patient-derived tumour xenograft (PDTX) models prevail as arguably the most powerful in this regard because they capture cancer's heterogeneous nature. Herein, we review current breast cancer models and their use in the drug discovery process, before discussing best practices for developing a highly annotated cohort of PDTX models. We describe the importance of extensive multidimensional molecular and functional characterisation of models and combination drug-drug screens to identify complex biomarkers of drug resistance and response. We reflect on our own experiences and propose the use of a cost-effective intermediate pharmacogenomic platform (the PDTX-PDTC platform) for breast cancer drug and biomarker discovery. We discuss the limitations and unanswered questions of PDTX models; yet, still strongly envision that their use in basic and translational research will dramatically change our understanding of breast cancer biology and how to more effectively treat it.

Understanding the epigenetic regulation of tumours and their microenvironments: opportunities and problems for epigenetic therapy

The tumour microenvironment plays an instrumental role in cancer development, progression and treatment response/resistance. Accumulating evidence is underscoring the fundamental importance of epigenetic regulation in tumour immune evasion. Following many pioneering discoveries demonstrating malignant transformation through epigenetic anomalies ('epimutations'), there is also a growing emphasis on elucidating aberrant epigenetic mechanisms that reprogramme the milieu of tumour-associated immune and stromal cells towards an immunosuppressive state. Pharmacological inhibition of DNA methylation and histone modifications can augment the efficiency of immune checkpoint blockage, and unleash anti-tumour T-cell responses. However, these non-specific agents also represent a 'double-edged sword', as they can also reactivate gene transcription of checkpoint molecules, interrupting immune surveillance programmes. By understanding the impact of epigenetic control on the tumour microenvironment, rational combinatorial epigenetic and checkpoint blockage therapies have the potential to harness the immune system for the treatment of cancer. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

A novel signaling role for miR-451 in esophageal tumor microenvironment and its contribution to tumor progression

OBJECTIVE

We evaluated miR-451 expression in serum and tissue samples of esophageal squamous cell carcinoma (ESCC) patients. Then, we examined a secretory role of miR-451 in esophageal tumor microenvironment.

METHODS

miR-451 expression was evaluated in 39 serum samples from esophageal SCC patients compared to 39 normal individuals as well as 26 pairs of fresh-frozen tumor and adjacent normal tissues from patients with ESCC, using qRT-PCR. In a co-culture system of human normal fibroblasts (HFSF-PI3) and esophageal cancer cell line (KYSE-30), we evaluated exosomal miR-451 secretion into the conditioned medium (CM) of both cell lines. Then, we analyzed the effect of primiR-451-transfected fibroblasts on the migration potency of their neighboring KYSE-30 cells.

RESULTS

We detected miR-451 over-expression in serum samples of esophageal cancer patients compared to the normal group (P = 0.005). Interestingly, fresh-frozen tumor tissues from the same patients showed miR-451 down-regulation compared to their adjacent normal counterparts (P = 0.043). Co-culturing the KYSE-30 cell line with normal fibroblasts significantly induced miR-451 exosomal secretion into the CM. Moreover, co-culture of KYSE-30 cell line with miR-451-over-expressing fibroblasts significantly induced migration tendency in KYSE-30 cell line compared to the mock-transfected fibroblasts (P < 0.0001). In this system, MIF expression (a validated target of miR-451) in the KYSE-30 cell line was increased although this alteration was not statistically significant (fold change = 4.44).

CONCLUSIONS

Our data suggest that cancer-associated fibroblasts use exosomal miR-451 as a signaling molecule to provide a favorable niche for tumor cell migration and cancer progression. Our findings provide new insights into the stromal role of miR-451 in the esophageal tumor microenvironment as a communicatory molecule and suggest a signaling role for miR-451 in extracellular matrix cross-talks.

A COL11A1-correlated pan-cancer gene signature of activated fibroblasts for the prioritization of therapeutic targets

Although cancer-associated fibroblasts (CAFs) are viewed as a promising therapeutic target, the design of rational therapy has been hampered by two key obstacles. First, attempts to ablate CAFs have resulted in significant toxicity because currently used biomarkers cannot effectively distinguish activated CAFs from non-cancer associated fibroblasts and mesenchymal progenitor cells. Second, it is unclear whether CAFs in different organs have different molecular and functional properties that necessitate organ-specific therapeutic designs. Our analyses uncovered COL11A1 as a highly specific biomarker of activated CAFs. Using COL11A1 as a 'seed', we identified co-expressed genes in 13 types of primary carcinoma in The Cancer Genome Atlas. We demonstrated that a molecular signature of activated CAFs is conserved in epithelial cancers regardless of organ site and transforming events within cancer cells, suggesting that targeting fibroblast activation should be effective in multiple cancers. We prioritized several potential pan-cancer therapeutic targets that are likely to have high specificity for activated CAFs and minimal toxicity in normal tissues.

Enigmas in tumor resistance to kinase inhibitors and calculation of the drug resistance index for cancer (DRIC)

Darwinian selection is also applicable when antibiotics, the immune system or other host factors shape the repertoire of microorganisms, and similarly, clonal selection is the hallmark of tumor evolution. The ongoing revolution in new anti-cancer treatment modalities, combined with an unprecedented precision in characterizing malignant clones at the level below one percent, profoundly improves the understanding of repertoire-tuning mechanisms. There is no fundamental difference between selection of the tumor cells in the presence, or absence, of therapy. However, under treatment the influence of a single agent can be measured, simplifying the analysis. Because of their beneficial and selective therapeutic effect, the focus in this review is set on protein kinase inhibitors (PKIs), predominantly tyrosine kinase inhibitors (TKIs). This is one of the most rapidly growing families of novel cancer medicines. In order to limit the number of drugs, the following representative target kinases are included: ALK, BCR-ABL, BRAF, BTK, and EGFR. A key therapeutic challenge is how to reduce tumor growth after treatment, since this is rate-limiting for the generation and expansion of more malignant escape mutants. Thus, upon efficient treatment, tumor cell loss often enables a profoundly increased growth rate among resistant cells. Strategies to reduce this risk, such as concomitant, competitive outgrowth of non-transformed cells, are described. Seven parameters: 1. Drug type, 2. tumor type, 3. presence of metastases or phenotypic change, 4. tumor cell number, 5. net growth rate (proliferation minus cell death), 6. inherited genetic- and 7. epigenetic- variations are crucial for drug responses. It is envisaged that it might become possible to calculate a clinically relevant Drug Resistance Index for Cancer (DRIC) for each patient.

Tumor necrosis factor α in the onset and progression of leukemia

Tumor necrosis factor alpha (TNF-α), originally described as an anti-neoplastic cytokine, has been found, in apparent contradiction to its name, to play an important role in promoting the development and progression of malignant disease. Targeting TNF-α with TNF antagonists has elicited an objective response in certain solid tumors in phase I and II clinical trials. This review focuses on the relationship of TNF-α expressed by leukemia cells and adverse clinical features of leukemia. TNF-α is involved in all steps of leukemogenesis, including cellular transformation, proliferation, angiogenesis, and extramedullary infiltration. TNF-α is also an important factor in the tumor microenvironment and assists leukemia cells in immune evasion, survival, and resistance to chemotherapy. TNF-α may be a potent target for leukemia therapy.

Cancer stem cell targeted therapy: progress amid controversies

Although cancer stem cells have been well characterized in numerous malignancies, the fundamental characteristics of this group of cells, however, have been challenged by some recent observations: cancer stem cells may not necessary to be rare within tumors; cancer stem cells and non-cancer stem cells may undergo reversible phenotypic changes; and the cancer stem cells phenotype can vary substantially between patients. Here the current status and progresses of cancer stem cells theory is illustrated and via providing a panoramic view of cancer therapy, we addressed the recent controversies regarding the feasibility of cancer stem cells targeted anti-cancer therapy.

Spectral Clustering Predicts Tumor Tissue Heterogeneity Using Dynamic 18F-FDG PET: A Complement to the Standard Compartmental Modeling Approach

In this study, we described and validated an unsupervised segmentation algorithm for the assessment of tumor heterogeneity using dynamic ¹⁸F-FDG PET. The aim of our study was to objectively evaluate the proposed method and make comparisons with compartmental modeling parametric maps and SUV segmentations using simulations of clinically relevant tumor tissue types. Methods: An irreversible 2-tissue-compartmental model was implemented to simulate clinical and preclinical ¹⁸F-FDG PET time-activity curves using population-based arterial input functions (80 clinical and 12 preclinical) and the kinetic parameter values of 3 tumor tissue types. The simulated time-activity curves were corrupted with different levels of noise and used to calculate the tissue-type misclassification errors of spectral clustering (SC), parametric maps, and SUV segmentation. The utility of the inverse noise variance- and Laplacian score-derived frame weighting schemes before SC was also investigated. Finally, the SC scheme with the best results was tested on a dynamic ¹⁸F-FDG measurement of a mouse bearing subcutaneous colon cancer and validated using histology. Results: In the preclinical setup, the inverse noise variance-weighted SC exhibited the lowest misclassification errors (8.09%-28.53%) at all noise levels in contrast to the Laplacian score-weighted SC (16.12%-31.23%), unweighted SC (25.73%-40.03%), parametric maps (28.02%-61.45%), and SUV (45.49%-45.63%) segmentation. The classification efficacy of both weighted SC schemes in the clinical case was comparable to the unweighted SC. When applied to the dynamic ¹⁸F-FDG measurement of colon cancer, the proposed algorithm accurately identified densely vascularized regions from the rest of the tumor. In addition, the segmented regions and clusterwise average time-activity curves showed excellent correlation with the tumor histology. Conclusion: The promising results of SC mark its position as a robust tool for quantification of tumor heterogeneity using dynamic PET studies. Because SC tumor segmentation is based on the intrinsic structure of the underlying data, it can be easily applied to other cancer types as well.

Development and characterization of a microfluidic model of the tumour microenvironment

The physical microenvironment of tumours is characterized by heterotypic cell interactions and physiological gradients of nutrients, waste products and oxygen. This tumour microenvironment has a major impact on the biology of cancer cells and their response to chemotherapeutic agents. Despite this, most in vitro cancer research still relies primarily on cells grown in 2D and in isolation in nutrient- and oxygen-rich conditions. Here, a microfluidic device is presented that is easy to use and enables modelling and study of the tumour microenvironment in real-time. The versatility of this microfluidic platform allows for different aspects of the microenvironment to be monitored and dissected. This is exemplified here by real-time profiling of oxygen and glucose concentrations inside the device as well as effects on cell proliferation and growth, ROS generation and apoptosis. Heterotypic cell interactions were also studied. The device provides a live 'window' into the microenvironment and could be used to study cancer cells for which it is difficult to generate tumour spheroids. Another major application of the device is the study of effects of the microenvironment on cellular drug responses. Some data is presented for this indicating the device's potential to enable more physiological in vitro drug screening.

Application of clinical bioinformatics in lung cancer-specific biomarkers

The fact that lung cancer is a heterogeneous disease suggests that there is a high likelihood that effective lung cancer biomarkers will need to address patient-specific molecular defects, clinical characters, and aspects of the tumor microenvironment. In this transition, clinical bioinformatics tools and resources are the most appropriate means to improve the analysis, as major biological databases are now containing clinical data alongside genomics, proteomics, and other biological data. Clinical bioinformatics comprises a series of concepts and approaches that have been used successfully both to delineate novel biological mechanisms and to drive translational advances in individualized healthcare. In this article, we outline several of emerging clinical bioinformatics-based strategies as they apply specifically to lung cancer.

A Comprehensive MicroRNA Expression Profile of Liver and Lung Metastases of Colorectal Cancer with Their Corresponding Host Tissue and Its Prognostic Impact on Survival

MicroRNAs are small non-coding RNAs with a length of 18–25 nucleotides. They can regulate tumor invasion and metastasis by changing the expression and translation of their target mRNAs. Their expression is substantially altered in colorectal cancer cells as well as in the adjacent tumor-associated stroma. Both of these compartments have a mutual influence on tumor progression. In the development of metastases, cancer cells initially interact with the host tissue. Therefore, compartment-specific expression signatures of these three locations—tumor, associated stroma, and host tissue—can provide new insights into the complex tumor biology of colorectal cancer. Frozen tissue samples of colorectal liver (n = 25) and lung metastases (n = 24) were laser microdissected to separate tumor cells and the adjacent tumor-associated stroma cells. Additionally, normal lung and liver tissue was collected from the same patients. We performed a microarray analysis in four randomly selected liver metastases and four randomly selected lung metastases, analyzing a total of 939 human miRNAs. miRNAs with a significant change >2-fold between the tumor, tumor stroma, and host tissue were analyzed in all samples using RT-qPCR (11 miRNAs) and correlated with the clinical data. We found a differential expression of several miRNAs between the tumor, the tumor-associated stroma, and the host tissue compartment. When comparing liver and lung metastases, miR-194 showed a 1.5-fold; miR-125, miR-127, and miR-192 showed a 2.5-fold; miR-19 and miR-215 a 3-fold; miR-145, miR-199-3, and miR-429 a 5-fold; miR-21 a 7-fold; and, finally, miR-199-5 a 12.5-fold downregulation in liver metastases compared to lung metastases. Furthermore miR-19, miR-125, miR-127, miR-192, miR-194, miR-199-5, and miR-215 showed a significant upregulation in the normal liver tissue compared to the normal lung tissue. Univariate analysis identified an association of poor survival with the expression of miR-125 (p = 0.05), miR-127 (p = 0.001), miR-145 (p = 0.005), miR-192 (p = 0.015), miR-194 (0.003), miR-199-5 (p = 0.008), miR-215 (p < 0.001), and miR-429 (p = 0.03) in the host liver tissue of the liver metastases. Colorectal liver and lung metastases have a unique miRNA expression profile. miRNA expression in the host tissue of colorectal liver metastases seems to be able to influence tumor progression and survival. These findings can be used in the development of tailored therapies.

Heterotypic 3D tumor culture in a reusable platform using pneumatic microfluidics

The construction of a micro-platform capable of microscale control for continuous, dynamic, and high-throughput biomimetic tumor manipulation and analysis plays a significant role in biological and clinical research. Here, we introduce a pneumatic microstructure-based microfluidic platform for versatile three-dimensional (3D) tumor cultures. The manipulative potential of pneumatic microstructures in a fabrication-optimized microfluidic device can be stimulated to achieve ultra-repetitive (tens of thousands of times) and persistent (over several months) microfluidic control. We demonstrated that the microfluidic platform is reusable (dozens of times) for stable, reproducible, and high-throughput generation of tumors with uniform size. Various heterotypic and homotypic 3D tumor arrays can be produced successfully in the device based on robust pneumatic control. On-chip monitoring and analysis of tumor phenotypes and responses to different culture conditions and chemotherapies were also achieved in real-time in the microfluidic platform. The results indicate that fibroblasts cocultured with tumor cells positively promote the phenotypical appearance of heterotypic tumors. This microfluidic advancement offers a new methodological approach for the development of high-performance and non-disposable 3D culture systems and for tissue-mimicking cancer research. We believe that it could be valuable for various tumor-related research fields such as oncology, pharmacology, tissue engineering, and bioimaging.

Development of TRACER: tissue roll for analysis of cellular environment and response

The tumour microenvironment is heterogeneous and consists of multiple cell types, variable extracellular matrix (ECM) composition, and contains cell-defined gradients of small molecules, oxygen, nutrients and waste. Emerging in vitro cell culture systems that attempt to replicate these features often fail to incorporate design strategies to facilitate efficient data collection and stratification. The tissue roll for analysis of cellular environment and response (TRACER) is a novel strategy to assemble layered, three-dimensional tumours with cell-defined, graded heterogeneous microenvironments that also facilitates cellular separation and stratification of data from different cell populations from specific microenvironments. Here we describe the materials selection and development of TRACER. We find that cellulose fibre scaffolding is an ideal support to generate tissue constructs having homogenous cell seeding and consistent properties. We explore ECM remodeling and long-term cell growth in the scaffold, and characterize the tumour microenvironment in assembled TRACERs using multiple established analysis methods. Finally, we confirm that TRACERs replicate small molecule gradients of glucose and lactate, and explore cell phenotype associated with these gradients using confocal microscopy, flow cytometry, and quantitative PCR analysis. We envision this technology will provide a platform to create complex, yet controlled tumour microenvironments that can be easily disassembled for snapshot analysis of cell phenotype and response to therapy in relation to microenvironment properties.

Immune Priming of the Tumor Microenvironment by Radiation

Ionizing irradiation can induce a multitude of alterations within the tumor microenvironment. Unlike targeted therapies, radiation delivered to the tumor bed can prompt phenotypic changes in both normal stromal and cancer cells, leading to molecular and physiological alterations within the tumor microenvironment. These environmental modulations directly influence the degree of immunogenicity of the tumor microenvironment and may ultimately affect tumor responsiveness to cancer immunotherapies. Here we review the preclinical evidence for tumor microenvironment-mediated immune suppression and how radiation can modulate immune properties within a tumor. We then discuss the therapeutic opportunities for combining radiation with molecular agents to enhance tumor immunogenicity and how this represents a potential exciting strategy to complement immunotherapies including immune checkpoint blockers in cancer treatment.

Chemoresistance in Pancreatic Cancer Is Driven by Stroma-Derived Insulin-Like Growth Factors

Tumor-associated macrophages (TAM) and myofibroblasts are key drivers in cancer that are associated with drug resistance in many cancers, including pancreatic ductal adenocarcinoma (PDAC). However, our understanding of the molecular mechanisms by which TAM and fibroblasts contribute to chemoresistance is unclear. In this study, we found that TAM and myofibroblasts directly support chemoresistance of pancreatic cancer cells by secreting insulin-like growth factors (IGF) 1 and 2, which activate insulin/IGF receptors on pancreatic cancer cells. Immunohistochemical analysis of biopsies from patients with pancreatic cancer revealed that 72% of the patients expressed activated insulin/IGF receptors on tumor cells, and this positively correlates with increased CD163⁺ TAM infiltration. In vivo, we found that TAM and myofibroblasts were the main sources of IGF production, and pharmacologic blockade of IGF sensitized pancreatic tumors to gemcitabine. These findings suggest that inhibition of IGF in combination with chemotherapy could benefit patients with PDAC, and that insulin/IGF1R activation may be used as a biomarker to identify patients for such therapeutic intervention. Cancer Res; 76(23); 6851-63. ©2016 AACR.

Patient-derived xenograft models of colorectal cancer in pre-clinical research: a systematic review

AIMS

We sought to objectively assess the internal and external validity of patient-derived xenograft (PDX) models as a platform in pre-clinical research into colorectal cancer (CRC). Metastatic disease is the most common cause of death from CRC, and despite significant research, the results of current combination chemotherapy and targeted therapies have been underwhelming for most of this patient group. One of the key factors limiting the success of translational CRC research is the biologically inaccurate models in which new therapies are developed.

METHODS

We used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) checklist and SYRCLE (Systematic Review Centre for Laboratory animal Experimentation) guidelines to search Ovid MEDLINE and Embase databases up to July 2015 to identify studies involving PDX models of CRC where the model had been validated across multiple parameters. Data was extracted including host mouse strain, engraftment rate, site of engraftment, donor tumour source and development of metastases in the model.

RESULTS

Thirteen articles satisfied the inclusion criteria. There was significant heterogeneity amongst the included studies, but overall the median engraftment rate was high (70%) and PDX models faithfully recapitulated the characteristics of their patient tumours on the microscopic, genetic and functional levels.

CONCLUSIONS

PDX models of CRC have a reasonable internal validity and a high external validity. Developments in xenografting technology are broadening the applications of the PDX platform. However, the included studies could be improved by standardising reporting standards and closed following the ARRIVE (Animals in Research: Reporting In Vivo Experiments) guidelines.

Targeting Hypoxic Prostate Tumors Using the Novel Hypoxia-Activated Prodrug OCT1002 Inhibits Expression of Genes Associated with Malignant Progression

Purpose: To understand the role of hypoxia in prostate tumor progression and to evaluate the ability of the novel unidirectional hypoxia-activated prodrug OCT1002 to enhance the antitumor effect of bicalutamide.Experimental Design: The effect of OCT1002 on prostate cancer cells (LNCaP, 22Rv1, and PC3) was measured in normoxia and hypoxia in vitroIn vivo, tumor growth and lung metastases were measured in mice treated with bicalutamide, OCT1002, or a combination. Dorsal skin fold chambers were used to image tumor vasculature in vivo Longitudinal gene expression changes in tumors were analyzed using PCR.Results: Reduction of OCT1002 to its active form (OCT1001) decreased prostate cancer cell viability. In LNCaP-luc spheroids, OCT1002 caused increased apoptosis and decreased clonogenicity. In vivo, treatment with OCT1002 alone, or with bicalutamide, showed significantly greater tumor growth control and reduced lung metastases compared with controls. Reestablishment of the tumor microvasculature following bicalutamide-induced vascular collapse is inhibited by OCT1002. Significantly, the upregulation of RUNX2 and its targets caused by bicalutamide alone was blocked by OCT1002.Conclusions: OCT1002 selectively targets hypoxic tumor cells and enhances the antitumor efficacy of bicalutamide. Furthermore, bicalutamide caused changes in gene expression, which indicated progression to a more malignant genotype; OCT1002 blocked these effects, emphasizing that more attention should be attached to understanding genetic changes that may occur during treatment. Early targeting of hypoxic cells with OCT1002 can provide a means of inhibiting prostate tumor growth and malignant progression. This is of importance for the design and refinement of existing androgen-deprivation regimens in the clinic. Clin Cancer Res; 23(7); 1797-808. ©2016 AACR.

Regulation of Transdifferentiation and Retrodifferentiation by Inflammatory Cytokines in Hepatocellular Carcinoma

Liver cancers are typically inflammation-associated cancers characterized by close communication between the tumor cells and the tumor environment. This supportive inflammatory environment contributes to the establishment of a pathologic niche consisting of transformed epithelial cells, tumor-educated fibroblasts, endothelial cells, and immunosuppressive immature myeloid cells. Stromal and infiltrated immune cells help determine tumor fate, but the tumor cells themselves, including cancer stem cells, also influence the surrounding cells. This bidirectional communication generates an intricate network of signals that promotes tumor growth. Cell plasticity, which includes transdifferentiation and retrodifferentiation of differentiated cells, increases tumor heterogeneity. Plasticity allows non-cancer stem cells to replenish the cancer stem cell pool, initiate tumorigenesis, and escape the effects of therapeutic agents; it also promotes tumor aggressiveness. There is increasing evidence that an inflammatory environment promotes the retrodifferentiation of tumor cells into stem or progenitor cells; this could account for the low efficacies of some chemotherapies and the high rates of cancer recurrence. Increasing our understanding of the signaling network that connects inflammation with retrodifferentiation could identify new therapeutic targets, and lead to combined therapies that are effective against highly heterogeneous tumors.

Exosomes derived from HCC cells induce sorafenib resistance in hepatocellular carcinoma both in vivo and in vitro

Background

Exosomes are carriers of intercellular information and regulate the tumor microenvironment. They play an important role in drug resistance by transporting RNA molecules and proteins. However, their effects on sorafenib resistance in hepatocellular carcinoma (HCC) are not completely understood.

Methods

Exosomes were isolated from two invasive hepatoma cell lines (MHCC-97 L and MHCC-97H), and their roles in regulating sorafenib resistance in liver cancer cells as well as the underlying molecular mechanisms were determined. The exosomes were analyzed by TEM (transmission electron microscopy), DLS (dynamic light scattering) and Western blotting. Cell viability, cell death and the effects of exosomes on the HGF/c-Met/Akt signaling pathway in cancer cells were analyzed by MTT assays, FACS analysis and Western blotting, respectively. Moreover, the effects of exosomes on sorafenib resistance in vivo were investigated using a subcutaneous transplantation tumor model in athymic nude mice.

Results

Exosomes derived from HCC cells were of the expected size and expressed the exosomal markers CD9 and CD63. They induced sorafenib resistance in vitro by activating the HGF/c-Met/Akt signaling pathway and inhibiting sorafenib-induced apoptosis. They also induced sorafenib resistance in vivo by inhibiting sorafenib-induced apoptosis. Moreover, exosomes derived from highly invasive tumor cells had greater efficacy than that of exosomes derived from less invasive cells.

Conclusions

These data reveal the important role of HCC cell-derived exosomes in the drug resistance of liver cancer cells and demonstrate the intrinsic interaction between exosomes and their targeted tumor cells. This study suggests a new strategy for improving the effectiveness of sorafenib in treating HCC.

Spatial Proximity to Fibroblasts Impacts Molecular Features and Therapeutic Sensitivity of Breast Cancer Cells Influencing Clinical Outcomes

Using a three-dimensional coculture model, we identified significant subtype-specific changes in gene expression, metabolic, and therapeutic sensitivity profiles of breast cancer cells in contact with cancer-associated fibroblasts (CAF). CAF-induced gene expression signatures predicted clinical outcome and immune-related differences in the microenvironment. We found that fibroblasts strongly protect carcinoma cells from lapatinib, attributable to its reduced accumulation in carcinoma cells and an elevated apoptotic threshold. Fibroblasts from normal breast tissues and stromal cultures of brain metastases of breast cancer had similar effects as CAFs. Using synthetic lethality approaches, we identified molecular pathways whose inhibition sensitizes HER2⁺ breast cancer cells to lapatinib both in vitro and in vivo, including JAK2/STAT3 and hyaluronic acid. Neoadjuvant lapatinib therapy in HER2⁺ breast tumors lead to a significant increase of phospho-STAT3⁺ cancer cells and a decrease in the spatial proximity of proliferating (Ki67⁺) cells to CAFs impacting therapeutic responses. Our studies identify CAF-induced physiologically and clinically relevant changes in cancer cells and offer novel approaches for overcoming microenvironment-mediated therapeutic resistance. Cancer Res; 76(22); 6495-506. ©2016 AACR.

A bladder cancer microenvironment simulation system based on a microfluidic co-culture model

A tumor microenvironment may promote tumor metastasis and progression through the dynamic interplay between neoplastic cells and stromal cells. In this work, the most representative and significant stromal cells, fibroblasts, endothelial cells, and macrophages were used as vital component elements and combined with bladder cancer cells to construct a bladder cancer microenvironment simulation system. This is the first report to explore bladder cancer microenvironments based on 4 types of cells co-cultured simultaneously. This simulation system comprises perfusion equipment, matrigel channel units, a medium channel and four indirect contact culture chambers, allowing four types of cells to simultaneously interact through soluble biological factors and metabolites. With this system, bladder cancer cells (T24) with a tendency to form a ‘reticular’ structure under 3 dimensional culture conditions were observed in real time. The microenvironment characteristics of paracrine interactions and cell motility were successfully simulated in this system. The phenotype change process in stromal cells was successfully reproduced in this system by testing the macrophage effector molecule Arg-1. Arg-1 was highly expressed in the simulated tumor microenvironment group. To develop “precision medicine” in bladder cancer therapy, bladder cancer cells were treated with different clinical ‘neo-adjuvant’ chemotherapy schemes in this system, and their sensitivity differences were fully reflected. This work provides a preliminary foundation for neo-adjuvant chemotherapy in bladder cancer, a theoretical foundation for tumor microenvironment simulation and promotes individual therapy in bladder cancer patients.

CRISPR-Cas9 therapeutics in cancer: promising strategies and present challenges

Cancer is characterized by multiple genetic and epigenetic alterations that drive malignant cell proliferation and confer chemoresistance. The ability to correct or ablate such mutations holds immense promise for combating cancer. Recently, because of its high efficiency and accuracy, the CRISPR-Cas9 genome editing technique has been widely used in cancer therapeutic explorations. Several studies used CRISPR-Cas9 to directly target cancer cell genomic DNA in cellular and animal cancer models which have shown therapeutic potential in expanding our anticancer protocols. Moreover, CRISPR-Cas9 can also be employed to fight oncogenic infections, explore anticancer drugs, and engineer immune cells and oncolytic viruses for cancer immunotherapeutic applications. Here, we summarize these preclinical CRISPR-Cas9-based therapeutic strategies against cancer, and discuss the challenges and improvements in translating therapeutic CRISPR-Cas9 into clinical use, which will facilitate better application of this technique in cancer research. Further, we propose potential directions of the CRISPR-Cas9 system in cancer therapy.

Simultaneous targeting of Eph receptors in glioblastoma

Eph tyrosine kinase receptors are frequently overexpressed and functional in many cancers, and they are attractive candidates for targeted therapy. Here, we analyzed the expression of Eph receptor A3, one of the most up-regulated factors in glioblastoma cells cultured under tumorsphere-forming conditions, together with EphA2 and EphB2 receptors. EphA3 was overexpressed in up to 60% of glioblastoma tumors tested, but not in normal brain. EphA3 was localized in scattered areas of the tumor, the invasive ring, and niches near tumor vessels. EphA3 co-localized with macrophage/leukocyte markers, suggesting EphA3 expression on tumor-infiltrating cells of bone marrow origin. We took advantage of the fact that ephrinA5 (eA5) is a ligand that binds EphA3, EphA2 and EphB2 receptors, and used it to construct a novel targeted anti-glioblastoma cytotoxin. The eA5-based cytotoxin potently and specifically killed glioblastoma cells with an IC50 of at least 10-11 M. This and similar cytotoxins will simultaneously target different compartments of glioblastoma tumors while mitigating tumor heterogeneity.

Regional glutamine deficiency in tumours promotes dedifferentiation through inhibition of histone demethylation

Poorly organized tumour vasculature often results in areas of limited nutrient supply and hypoxia. Despite our understanding of solid tumour responses to hypoxia, how nutrient deprivation regionally affects tumour growth and therapeutic response is poorly understood. Here, we show that the core region of solid tumours displayed glutamine deficiency compared with other amino acids. Low glutamine in tumour core regions led to dramatic histone hypermethylation due to decreased α-ketoglutarate levels, a key cofactor for the Jumonji-domain-containing histone demethylases. Using patient-derived (V600E)BRAF melanoma cells, we found that low-glutamine-induced histone hypermethylation resulted in cancer cell dedifferentiation and resistance to BRAF inhibitor treatment, which was largely mediated by methylation on H3K27, as knockdown of the H3K27-specific demethylase KDM6B and the methyltransferase EZH2 respectively reproduced and attenuated the low-glutamine effects in vitro and in vivo. Thus, intratumoral regional variation in the nutritional microenvironment contributes to tumour heterogeneity and therapeutic response.

Cancer therapeutic potential of combinatorial immuno- and vasomodulatory interventions

Currently, most of the basic mechanisms governing tumour-immune system interactions, in combination with modulations of tumour-associated vasculature, are far from being completely understood. Here, we propose a mathematical model of vascularized tumour growth, where the main novelty is the modelling of the interplay between functional tumour vasculature and effector cell recruitment dynamics. Parameters are calibrated on the basis of different in vivo immunocompromised Rag1(-/-) and wild-type (WT) BALB/c murine tumour growth experiments. The model analysis supports that tumour vasculature normalization can be a plausible and effective strategy to treat cancer when combined with appropriate immunostimulations. We find that improved levels of functional tumour vasculature, potentially mediated by normalization or stress alleviation strategies, can provide beneficial outcomes in terms of tumour burden reduction and growth control. Normalization of tumour blood vessels opens a therapeutic window of opportunity to augment the antitumour immune responses, as well as to reduce intratumoral immunosuppression and induced hypoxia due to vascular abnormalities. The potential success of normalizing tumour-associated vasculature closely depends on the effector cell recruitment dynamics and tumour sizes. Furthermore, an arbitrary increase in the initial effector cell concentration does not necessarily imply better tumour control. We evidence the existence of an optimal concentration range of effector cells for tumour shrinkage. Based on these findings, we suggest a theory-driven therapeutic proposal that optimally combines immuno- and vasomodulatory interventions.

Heralding a new paradigm in 3D tumor modeling

Numerous studies to date have contributed to a paradigm shift in modeling cancer, moving from the traditional two-dimensional culture system to three-dimensional (3D) culture systems for cancer cell culture. This led to the inception of tumor engineering, which has undergone rapid advances over the years. In line with the recognition that tumors are not merely masses of proliferating cancer cells but rather, highly complex tissues consisting of a dynamic extracellular matrix together with stromal, immune and endothelial cells, significant efforts have been made to better recapitulate the tumor microenvironment in 3D. These approaches include the development of engineered matrices and co-cultures to replicate the complexity of tumor-stroma interactions in vitro. However, the tumor engineering and cancer biology fields have traditionally relied heavily on the use of cancer cell lines as a cell source in tumor modeling. While cancer cell lines have contributed to a wealth of knowledge in cancer biology, the use of this cell source is increasingly perceived as a major contributing factor to the dismal failure rate of oncology drugs in drug development. Backing this notion is the increasing evidence that tumors possess intrinsic heterogeneity, which predominantly homogeneous cancer cell lines poorly reflect. Tumor heterogeneity contributes to therapeutic resistance in patients. To overcome this limitation, cancer cell lines are beginning to be replaced by primary tumor cell sources, in the form of patient-derived xenografts and organoids cultures. Moving forward, we propose that further advances in tumor engineering would require that tumor heterogeneity (tumor variants) be taken into consideration together with tumor complexity (tumor-stroma interactions). In this review, we provide a comprehensive overview of what has been achieved in recapitulating tumor complexity, and discuss the importance of incorporating tumor heterogeneity into 3D in vitro tumor models. This work carves out the roadmap for 3D tumor engineering and highlights some of the challenges that need to be addressed as we move forward into the next chapter.

Lysyl oxidase isoforms in gastric cancer

Gastric cancer (GC) is the fifth most frequent cancer in the world and shows the highest incidence in Latin America and Asia. An increasing amount of evidence demonstrates that lysyl oxidase isoforms, a group of extracellular matrix crosslinking enzymes, should be considered as potential biomarkers and therapeutic targets in GC. In this review, we focus on the expression levels of lysyl oxidase isoforms, its functions and the clinical implications in GC. Finding novel proteins related to the processing of these extracellular matrix enzymes might be helpful in the design of new therapies, which, in combination with classic pharmacology, could be used to delay the progress of this aggressive cancer and offer a wider temporal window for clinical intervention.

Simulation of heterogeneous molecular delivery in tumours using μCT reconstructions and MRI validation

PRIMARY OBJECTIVE

Utilizing the detailed vascular network obtained from micro-computed tomography (μCT) to establish a mathematical model of the temporal molecular distribution within a murine C3H mammary carcinoma.

PROCEDURES

Female CDF1 mice with a C3H mammary carcinoma on the right rear foot were used in this study. Dynamic information for each tumour was achieved by Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI) on a 16.4 T system. Detailed morphologic information on the tumour vasculature was obtained by ex vivo μCT and compared to CD34 immunohistochemical staining of tissue sections. The reconstructed vascular network served as origin for the diffusion (described by the apparent diffusion coefficient) within the tumour (the restricted volume described by the interstitial volume fraction derived from DCE-MRI). The resulting partial differential equation was solved using Finite-Element and a combined mathematical graph describing molecular distribution within the tumour was obtained.

RESULTS

The established molecular distribution model predicted a heterogeneous distribution throughout the tumour related to the layout of the vascular network. Central tumour section concentration-time curves estimated from the established molecular distribution model were compared with physical measurements obtained by DCE-MRI of the same tumours and showed excellent correlation.

CONCLUSIONS

A mathematical model describing temporal molecular distribution based on detailed vascular network structures was established and compared to DCE-MRI. The improved morphological insight will enhance future studies of heterogeneous tumours.

Acoustic Cluster Therapy (ACT) enhances the therapeutic efficacy of paclitaxel and Abraxane® for treatment of human prostate adenocarcinoma in mice

Acoustic cluster therapy (ACT) is a novel approach for ultrasound mediated, targeted drug delivery. In the current study, we have investigated ACT in combination with paclitaxel and Abraxane® for treatment of a subcutaneous human prostate adenocarcinoma (PC3) in mice. In combination with paclitaxel (12mg/kg given i.p.), ACT induced a strong increase in therapeutic efficacy; 120days after study start, 42% of the animals were in stable, complete remission vs. 0% for the paclitaxel only group and the median survival was increased by 86%. In combination with Abraxane® (12mg paclitaxel/kg given i.v.), ACT induced a strong increase in the therapeutic efficacy; 60days after study start 100% of the animals were in stable, remission vs. 0% for the Abraxane® only group, 120days after study start 67% of the animals were in stable, complete remission vs. 0% for the Abraxane® only group. For the ACT+Abraxane group 100% of the animals were alive after 120days vs. 0% for the Abraxane® only group. Proof of concept for Acoustic Cluster Therapy has been demonstrated; ACT markedly increases the therapeutic efficacy of both paclitaxel and Abraxane® for treatment of human prostate adenocarcinoma in mice.

Cancer heterogeneity determined by functional proteomics

Current manuscript gives a synopsis of tumor heterogeneity related to patient samples analyzed by proteomics, protein expression analysis and imaging mass spectrometry. First, we discuss the pathophysiologocal background of cancer biology as a multifactorial and challenging diseases. Disease pathology forms the basis for protein target selection. Therefore, histopathological diagnostics and grading of tumors is highlighted. Pathology is the cornerstone of state-of-the-art diagnostics of tumors today both by establishing dignity and - when needed - describing molecular properties of the cancers. Drug development by the pharmaceutical industry utilizes proteomics studies to pinpoint the most relevant targets. Molecular studies profiling affinity-interactions of the protein(s) with targeted small drug molecules to reach efficacy and optimal patient safety are today requested by the FDA and other agencies for new drug development. An understading of basic mechanisms, controlling drug action and drug binding is central, as a new era of personalized medicine becomes an important milestone solution for the healthcare sector as well as the Pharma and Biotech industry. Development of further diagnostic, prognostic and predictive tests will aid current and future treatment of cancer patients. In the paper we present current status of Proteomics that we believe requires attention in order to collectively advance forward in the fight against cancer, addressing the burning opportunities and challenges.

In Vitro Co-Culture Models of Breast Cancer Metastatic Progression towards Bone

Advanced breast cancer frequently metastasizes to bone through a multistep process involving the detachment of cells from the primary tumor, their intravasation into the bloodstream, adhesion to the endothelium and extravasation into the bone, culminating with the establishment of a vicious cycle causing extensive bone lysis. In recent years, the crosstalk between tumor cells and secondary organs microenvironment is gaining much attention, being indicated as a crucial aspect in all metastatic steps. To investigate the complex interrelation between the tumor and the microenvironment, both in vitro and in vivo models have been exploited. In vitro models have some advantages over in vivo, mainly the possibility to thoroughly dissect in controlled conditions and with only human cells the cellular and molecular mechanisms underlying the metastatic progression. In this article we will review the main results deriving from in vitro co-culture models, describing mechanisms activated in the crosstalk between breast cancer and bone cells which drive the different metastatic steps.

C-kit signaling promotes proliferation and invasion of colorectal mucinous adenocarcinoma in a murine model

It was reported that the receptor tyrosine kinase (RTK) family often highly expressed in several mucinous carcinomas. In the present study, we established a murine model of colorectal mucinous adenocardinoma (CRMAC) by treating C57 mice [both wild type (WT) and loss-of-function c-kit mutant type (Wads-/-)] with AOM+DSS for 37 weeks and found that c-kit, a member of RTK family, clearly enhanced the tumor cell proliferation by decreasing p53 and increasing cyclin D1 through AKT pathway. Significantly, c-kit strongly promoted tumor cell invasiveness by increasing ETV4, which induced MMP7 expression and epithelial-mesenchymal transition (EMT) via ERK pathway. In vitro up- or down-regulating c-kit activation in human colorectal cancer HCT-116 cells further consolidated these results. In conclusion, our data suggested that the c-kit signaling obviously promoted proliferation and invasion of CRMAC. Therefore, targeting the c-kit signaling and its downstream molecules might provide the potential strategies for treatment of patients suffering from CRMAC in the future.

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MOLECULAR EVALUATION OF METASTATIC DISEASE

WHY PATHOLOGY REMAINS (AND WILL REMAIN) MANDATORY?: Numerous techniques are now available for the molecular evaluation of a tissular or cellular sample in the context of metastatic disease. They include in situ molecular techniques, such as immunohistochemistry for the study of proteins and peptides, in situ hybridization for the study of nucleic acids and in situ cytogenetics (FISH and its variants) for the demonstration of chromosome alterations. They also include all the techniques of molecular biology, which can now be applied to frozen as well as fixed tissue samples. The combination of all these techniques makes it possible an integrated and coherent approach, not limited to the description of DNA abnormalities, but able to correlate genomic alterations with functional, and even structural changes. A second major interest of the analysis of tissue samples is that they make it possible to analyzing not only tumor cells, but also their environment, formed by the stroma and its populations. The study of stroma and of stromal cells, in particular of immune cells, is now of paramount importance for providing new prognostic and predictive biomarkers, especially for anti-angiogenic strategies and for cancer immunotherapy. Tissue analysis is therefore the only way to perform a « total », « phenogenomic » characterization of the tumor as an organ : this is particularly important in the moment in which descriptive genomics is substituted by functional genomics and integrated biology.

Human Organotypic Lung Tumor Models: Suitable For Preclinical 18F-FDG PET-Imaging

Development of predictable in vitro tumor models is a challenging task due to the enormous complexity of tumors in vivo. The closer the resemblance of these models to human tumor characteristics, the more suitable they are for drug-development and –testing. In the present study, we generated a complex 3D lung tumor test system based on acellular rat lungs. A decellularization protocol was established preserving the architecture, important ECM components and the basement membrane of the lung. Human lung tumor cells cultured on the scaffold formed cluster and exhibited an up-regulation of the carcinoma-associated marker mucin1 as well as a reduced proliferation rate compared to respective 2D culture. Additionally, employing functional imaging with 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography (FDG-PET) these tumor cell cluster could be detected and tracked over time. This approach allowed monitoring of a targeted tyrosine kinase inhibitor treatment in the in vitro lung tumor model non-destructively. Surprisingly, FDG-PET assessment of single tumor cell cluster on the same scaffold exhibited differences in their response to therapy, indicating heterogeneity in the lung tumor model. In conclusion, our complex lung tumor test system features important characteristics of tumors and its microenvironment and allows monitoring of tumor growth and -metabolism in combination with functional imaging. In longitudinal studies, new therapeutic approaches and their long-term effects can be evaluated to adapt treatment regimes in future.

Intratumoral oxygen gradients mediate sarcoma cell invasion

Hypoxia is a critical factor in the progression and metastasis of many cancers, including soft tissue sarcomas. Frequently, oxygen (O2) gradients develop in tumors as they grow beyond their vascular supply, leading to heterogeneous areas of O2 depletion. Here, we report the impact of hypoxic O2 gradients on sarcoma cell invasion and migration. O2 gradient measurements showed that large sarcoma mouse tumors (>300 mm(3)) contain a severely hypoxic core [≤0.1% partial pressure of O2 (pO2)] whereas smaller tumors possessed hypoxic gradients throughout the tumor mass (0.1-6% pO2). To analyze tumor invasion, we used O2-controllable hydrogels to recreate the physiopathological O2 levels in vitro. Small tumor grafts encapsulated in the hydrogels revealed increased invasion that was both faster and extended over a longer distance in the hypoxic hydrogels compared with nonhypoxic hydrogels. To model the effect of the O2 gradient accurately, we examined individual sarcoma cells embedded in the O2-controllable hydrogel. We observed that hypoxic gradients guide sarcoma cell motility and matrix remodeling through hypoxia-inducible factor-1α (HIF-1α) activation. We further found that in the hypoxic gradient, individual cells migrate more quickly, across longer distances, and in the direction of increasing O2 tension. Treatment with minoxidil, an inhibitor of hypoxia-induced sarcoma metastasis, abrogated cell migration and matrix remodeling in the hypoxic gradient. Overall, we show that O2 acts as a 3D physicotactic agent during sarcoma tumor invasion and propose the O2-controllable hydrogels as a predictive system to study early stages of the metastatic process and therapeutic targets.

Infiltrating immune cells and gene mutations in pancreatic ductal adenocarcinoma

BACKGROUND

The aim of this study was to assess the immune profile within the microenvironment of pancreatic ductal adenocarcinoma (PDAC), and to investigate the prognostic value of intratumoral infiltrating immune/inflammatory cells (IICs) in patients after surgery.

METHODS

Eighteen phenotypic markers representing 11 types of IIC and the protein products of genes TP53, CDKN2A/p16 and SMAD4/DPC4 were assessed by immunohistochemistry of specimens from patients with pancreatic cancer. The expression of IICs and the mutational status of the genes were correlated with tumour recurrence and survival, and results were validated in an independent cohort.

RESULTS

CD15+ neutrophils, CD20+ B cells and CD206+ tumour-associated macrophages were seen frequently in tumours, and their presence was associated with reduced survival in a cohort of 79 patients. Expression of CD4+ T helper cells, CD8+ cytotoxic T lymphocytes and CD117+ mast cells was associated with a favourable prognosis. A weighted Cox regression recurrence-predictive model was constructed that showed good correlation of IICs and gene mutations. A combination of CD15, CD206, CD117 and Smad4 expression was independently associated with overall (hazard ratio (HR) 3·63, 95 per cent c.i. 2·18 to 6·04; P < 0·001) and recurrence-free (HR 2·93, 1·81 to 4·75; P < 0·001) survival. These findings were validated in an independent cohort (151 patients) and in 54 tissue samples obtained by preoperative endoscopic ultrasound-guided fine-needle aspiration.

CONCLUSION

PDAC has a unique immunosuppressive phenotype that is associated with characteristic gene mutations, disease recurrence and survival after pancreatectomy. Surgical relevance The immune microenvironment plays a critical role in the development of pancreatic ductal adenocarcinoma (PDAC). PDAC is associated with mutations in major driver genes, including KRAS, TP53, CDKN2A/p16 and SMAD4/DPC4. This study shows that the microenvironment of PDAC has a unique immunosuppressive phenotype, which may be driven by oncogene mutations. Patients with PDAC with a highly immunosuppressive profile tended to have poor postoperative survival. A model including three intratumoral infiltrating immune markers (CD15+, CD206+ and CD117+) and a SMAD4 mutation can be used to predict recurrence and survival in patients after surgery for PDAC.

Spatial Heterogeneity in the Tumor Microenvironment

Recent developments in studies of tumor heterogeneity have provoked new thoughts on cancer management. There is a desperate need to understand influence of the tumor microenvironment on cancer development and evolution. Applying principles and quantitative methods from ecology can suggest novel solutions to fulfil this need. We discuss spatial heterogeneity as a fundamental biological feature of the microenvironment, which has been largely ignored. Histological samples can provide spatial context of diverse cell types coexisting within the microenvironment. Advanced computer-vision techniques have been developed for spatial mapping of cells in histological samples. This has enabled the applications of experimental and analytical tools from ecology to cancer research, generating system-level knowledge of microenvironmental spatial heterogeneity. We focus on studies of immune infiltrate and tumor resource distribution, and highlight statistical approaches for addressing the emerging challenges based on these new approaches.

Patient-derived cell models as preclinical tools for genome-directed targeted therapy

Background

In this study, we established patient-derived tumor cell (PDC) models using tissues collected from patients with metastatic cancer and assessed whether these models could be used as a tool for genome-based cancer treatment.

Methods

PDCs were isolated and cultured from malignant effusions including ascites and pleural fluid. Pathological examination, immunohistochemical analysis, and genomic profiling were performed to compare the histological and genomic features of primary tumors, PDCs. An exploratory gene expression profiling assay was performed to further characterize PDCs.

Results

From January 2012 to May 2013, 176 samples from patients with metastatic cancer were collected. PDC models were successfully established in 130 (73.6%) samples. The median time from specimen collection to passage 1 (P1) was 3 weeks (range, 0.5–4 weeks), while that from P1 to P2 was 2.5 weeks (range, 0.5–5 weeks). Sixteen paired samples of genomic alterations were highly concordant between each primary tumor and progeny PDCs, with an average variant allele frequency (VAF) correlation of 0.878. We compared genomic profiles of the primary tumor (P0), P1 cells, P2 cells, and patient-derived xenografts (PDXs) derived from P2 cells and found that three samples (P0, P1, and P2 cells) were highly correlated (0.99–1.00). Moreover, PDXs showed more than 100 variants, with correlations of only 0.6–0.8 for the other samples. Drug responses of PDCs were reflective of the clinical response to targeted agents in selected patient PDC lines.

Conclusion(s)

Our results provided evidence that our PDC model was a promising model for preclinical experiments and closely resembled the patient tumor genome and clinical response.