Combinatorial Microenvironments Impose a Continuum of Cellular Responses to a Single Pathway-Targeted Anti-cancer Compound.

Tumor microenvironments are a driver of resistance to anti-cancer drugs. Dissecting cell-microenvironment interactions into tractable units of study presents a challenge. Here, we assess the impact of hundreds of tumor-inspired microenvironments, in parallel, on lapatinib responses in four cancer cell lines. Combinations of ECM and soluble factors were printed on stiffness-tunable substrata to generate a collection of controlled microenvironments in which to explore cell-based functional responses. Proliferation, HER2 protein expression and phosphorylation, and morphology were measured in single cells. Using dimension reduction and linear modeling, the effects of microenvironment constituents were identified and then validated empirically. Each of the cell lines exhibits unique microenvironment-response patterns. Fibronectin, type IV collagen, and matrix rigidity are significant regulators of lapatinib resistance in HER2-amplified breast cancer cells. Small-molecule inhibitors were identified that could attenuate microenvironment-imposed resistance. Thus, we demonstrate a strategy to identify resistance- and sensitivity-driving microenvironments to improve the efficacy of anti-cancer therapeutics.

Fluorescent D-amino-acids reveal bi-cellular cell wall modifications important for Bdellovibrio bacteriovorus predation.

Modification of essential bacterial peptidoglycan (PG)-containing cell walls can lead to antibiotic resistance; for example, ß-lactam resistance by L,D-transpeptidase activities. Predatory Bdellovibrio bacteriovorus are naturally antibacterial and combat infections by traversing, modifying and finally destroying walls of Gram-negative prey bacteria, modifying their own PG as they grow inside prey. Historically, these multi-enzymatic processes on two similar PG walls have proved challenging to elucidate. Here, with a PG-labelling approach utilizing timed pulses of multiple fluorescent D-amino acids, we illuminate dynamic changes that predator and prey walls go through during the different phases of bacteria:bacteria invasion. We show formation of a reinforced circular port-hole in the prey wall, L,D-transpeptidaseBd-mediated D-amino acid modifications strengthening prey PG during Bdellovibrio invasion, and a zonal mode of predator elongation. This process is followed by unconventional, multi-point and synchronous septation of the intracellular Bdellovibrio, accommodating odd- and even-numbered progeny formation by non-binary division.

Activity of distinct growth factor receptor network components in breast tumors uncovers two biologically relevant subtypes.

BACKGROUND: The growth factor receptor network (GFRN) plays a significant role in driving key oncogenic processes. However, assessment of global GFRN activity is challenging due to complex crosstalk among GFRN components, or pathways, and the inability to study complex signaling networks in patient tumors. Here, pathway-specific genomic signatures were used to interrogate GFRN activity in breast tumors and the consequent phenotypic impact of GRFN activity patterns. METHODS: Novel pathway signatures were generated in human primary mammary epithelial cells by overexpressing key genes from GFRN pathways (HER2, IGF1R, AKT1, EGFR, KRAS (G12V), RAF1, BAD). The pathway analysis toolkit Adaptive Signature Selection and InteGratioN (ASSIGN) was used to estimate pathway activity for GFRN components in 1119 breast tumors from The Cancer Genome Atlas (TCGA) and across 55 breast cancer cell lines from the Integrative Cancer Biology Program (ICBP43). These signatures were investigated for their relationship to pro- and anti-apoptotic protein expression and drug response in breast cancer cell lines. RESULTS: Application of these signatures to breast tumor gene expression data identified two novel discrete phenotypes characterized by concordant, aberrant activation of either the HER2, IGF1R, and AKT pathways ("the survival phenotype") or the EGFR, KRAS (G12V), RAF1, and BAD pathways ("the growth phenotype"). These phenotypes described a significant amount of the variability in the total expression data across breast cancer tumors and characterized distinctive patterns in apoptosis evasion and drug response. The growth phenotype expressed lower levels of BIM and higher levels of MCL-1 proteins. Further, the growth phenotype was more sensitive to common chemotherapies and targeted therapies directed at EGFR and MEK. Alternatively, the survival phenotype was more sensitive to drugs inhibiting HER2, PI3K, AKT, and mTOR, but more resistant to chemotherapies. CONCLUSIONS: Gene expression profiling revealed a bifurcation pattern in GFRN activity represented by two discrete phenotypes. These phenotypes correlate to unique mechanisms of apoptosis and drug response and have the potential of pinpointing targetable aberration(s) for more effective breast cancer treatments.

Cross-platform pathway-based analysis identifies markers of response to the PARP inhibitor olaparib.

Poly(ADP-ribose) polymerase (PARP) is an enzyme involved in DNA repair. PARP inhibitors can act as chemosensitizers, or operate on the principle of synthetic lethality when used as single agent. Clinical trials have shown drugs in this class to be promising for BRCA mutation carriers. We postulated that inability to demonstrate response in non-BRCA carriers in which BRCA is inactivated by other mechanisms or with deficiency in homologous recombination for DNA repair is due to lack of molecular markers that define a responding subpopulation. We identified candidate markers for this purpose for olaparib (AstraZeneca) by measuring inhibitory effects of nine concentrations of olaparib in 22 breast cancer cell lines and identifying features in transcriptional and genome copy number profiles that were significantly correlated with response. We emphasized in this discovery process genes involved in DNA repair. We found that the cell lines that were sensitive to olaparib had a significant lower copy number of BRCA1 compared to the resistant cell lines (p value 0.012). In addition, we discovered seven genes from DNA repair pathways whose transcriptional levels were associated with response. These included five genes (BRCA1, MRE11A, NBS1, TDG, and XPA) whose transcript levels were associated with resistance and two genes (CHEK2 and MK2) whose transcript levels were associated with sensitivity. We developed an algorithm to predict response using the seven-gene transcription levels and applied it to 1,846 invasive breast cancer samples from 8 U133A/plus 2 (Affymetrix) data sets and found that 8-21 % of patients would be predicted to be responsive to olaparib. A similar response frequency was predicted in 536 samples analyzed on an Agilent platform. Importantly, tumors predicted to respond were enriched in basal subtype tumors. Our studies support clinical evaluation of the utility of our seven-gene signature as a predictor of response to olaparib.

Rab25 increases cellular ATP and glycogen stores protecting cancer cells from bioenergetic stress.

Cancer cells are metabolically stressed during tumour progression due to limited tumour vascularity and resultant nutrient, growth factor and oxygen deficiency that can induce cell death and inhibit tumour growth. We demonstrate that Rab25, a small GTPase involved in endosomal recycling, that is genomically amplified in multiple tumour lineages, is a key regulator of cellular bioenergetics and autophagy. RAB25 enhanced survival during nutrient stress by preventing apoptosis and autophagy via binding and activating AKT leading to increased glucose uptake and improved cellular bioenergetics. Unexpectedly, Rab25 induced the accumulation of glycogen in epithelial cancer cells, a process not previously identified. Strikingly, an increase in basal ATP levels combined with AKT-dependent increases in glucose uptake and glycogen storage allowed maintenance of ATP levels during bioenergetic stress. The clinical relevance of these findings was validated by the ability of a Rab25-dependent expression profile enriched for bioenergetics targets to identify patients with a poor prognosis. Thus, Rab25 is an unexpected regulator of cellular bioenergetics implicated as a useful biomarker and potential therapeutic target.

Prediction of epigenetically regulated genes in breast cancer cell lines.

BACKGROUND: Methylation of CpG islands within the DNA promoter regions is one mechanism that leads to aberrant gene expression in cancer. In particular, the abnormal methylation of CpG islands may silence associated genes. Therefore, using high-throughput microarrays to measure CpG island methylation will lead to better understanding of tumor pathobiology and progression, while revealing potentially new biomarkers. We have examined a recently developed high-throughput technology for measuring genome-wide methylation patterns called mTACL. Here, we propose a computational pipeline for integrating gene expression and CpG island methylation profiles to identify epigenetically regulated genes for a panel of 45 breast cancer cell lines, which is widely used in the Integrative Cancer Biology Program (ICBP). The pipeline (i) reduces the dimensionality of the methylation data, (ii) associates the reduced methylation data with gene expression data, and (iii) ranks methylation-expression associations according to their epigenetic regulation. Dimensionality reduction is performed in two steps: (i) methylation sites are grouped across the genome to identify regions of interest, and (ii) methylation profiles are clustered within each region. Associations between the clustered methylation and the gene expression data sets generate candidate matches within a fixed neighborhood around each gene. Finally, the methylation-expression associations are ranked through a logistic regression, and their significance is quantified through permutation analysis. RESULTS: Our two-step dimensionality reduction compressed 90% of the original data, reducing 137,688 methylation sites to 14,505 clusters. Methylation-expression associations produced 18,312 correspondences, which were used to further analyze epigenetic regulation. Logistic regression was used to identify 58 genes from these correspondences that showed a statistically significant negative correlation between methylation profiles and gene expression in the panel of breast cancer cell lines. Subnetwork enrichment of these genes has identified 35 common regulators with 6 or more predicted markers. In addition to identifying epigenetically regulated genes, we show evidence of differentially expressed methylation patterns between the basal and luminal subtypes. CONCLUSIONS: Our results indicate that the proposed computational protocol is a viable platform for identifying epigenetically regulated genes. Our protocol has generated a list of predictors including COL1A2, TOP2A, TFF1, and VAV3, genes whose key roles in epigenetic regulation is documented in the literature. Subnetwork enrichment of these predicted markers further suggests that epigenetic regulation of individual genes occurs in a coordinated fashion and through common regulators.

Yin yang 1 modulates taxane response in epithelial ovarian cancer.

Survival of ovarian cancer patients is largely dictated by their response to chemotherapy, which depends on underlying molecular features of the malignancy. We previously identified YIN YANG 1 (YY1) as a gene whose expression is positively correlated with ovarian cancer survival. Herein, we investigated the mechanistic basis of this association. Epigenetic and genetic characteristics of YY1 in serous epithelial ovarian cancer were analyzed along with YY1 mRNA and protein. Patterns of gene expression in primary serous epithelial ovarian cancer and in the NCI60 database were investigated using computational methods. YY1 function and modulation of chemotherapeutic response in vitro was studied using small interfering RNA knockdown. Microarray analysis showed strong positive correlation between expression of YY1 and genes with YY1 and transcription factor E2F binding motifs in ovarian cancer and in the NCI60 cancer cell lines. Clustering of microarray data for these genes revealed that high YY1/E2F3 activity positively correlates with survival of patients treated with the microtubule-stabilizing drug paclitaxel. Increased sensitivity to taxanes, but not to DNA cross-linking platinum agents, was also characteristic of NCI60 cancer cell lines with a high YY1/E2F signature. YY1 knockdown in ovarian cancer cell lines results in inhibition of anchorage-independent growth, motility, and proliferation but also increases resistance to taxanes, with no effect on cisplatin sensitivity. These results, together with the prior demonstration of augmentation of microtubule-related genes by E2F3, suggest that enhanced taxane sensitivity in tumors with high YY1/E2F activity may be mediated by modulation of putative target genes with microtubule function.

Cellular effect of high doses of silica-coated quantum dot profiled with high throughput gene expression analysis and high content cellomics measurements.

Quantum dots (Qdots) are now used extensively for labeling in biomedical research, and this use is predicted to grow because of their many advantages over alternative labeling methods. Uncoated Qdots made of core/shell CdSe/ZnS are toxic to cells because of the release of Cd2+ ions into the cellular environment. This problem has been partially overcome by coating Qdots with polymers, poly(ethylene glycol) (PEG), or other inert molecules. The most promising coating to date, for reducing toxicity, appears to be PEG. When PEG-coated silanized Qdots (PEG-silane-Qdots) are used to treat cells, toxicity is not observed, even at dosages above 10-20 nM, a concentration inducing death when cells are treated with polymer or mercaptoacid coated Qdots. Because of the importance of Qdots in current and future biomedical and clinical applications, we believe it is essential to more completely understand and verify this negative global response from cells treated with PEG-silane-Qdots. Consequently, we examined the molecular and cellular response of cells treated with two different dosages of PEG-silane-Qdots. Human fibroblasts were exposed to 8 and 80 nM of these Qdots, and both phenotypic as well as whole genome expression measurements were made. PEG-silane-Qdots did not induce any statistically significant cell cycle changes and minimal apoptosis/necrosis in lung fibroblasts (IMR-90) as measured by high content image analysis, regardless of the treatment dosage. A slight increase in apoptosis/necrosis was observed in treated human skin fibroblasts (HSF-42) at both the low and the high dosages. We performed genome-wide expression array analysis of HSF-42 exposed to doses 8 and 80 nM to link the global cell response to a molecular and genetic phenotype. We used a gene array containing approximately 22,000 total probe sets, containing 18,400 probe sets from known genes. Only approximately 50 genes (approximately 0.2% of all the genes tested) exhibited a statistically significant change in expression level of greater than 2-fold. Genes activated in treated cells included those involved in carbohydrate binding, intracellular vesicle formation, and cellular response to stress. Conversely, PEG-silane-Qdots induce a down-regulation of genes involved in controlling the M-phase progression of mitosis, spindle formation, and cytokinesis. Promoter analysis of these results reveals that expression changes may be attributed to the down-regulation of FOXM and BHLB2 transcription factors. Remarkably, PEG-silane-Qdots, unlike carbon nanotubes, do not activate genes indicative of a strong immune and inflammatory response or heavy-metal-related toxicity. The experimental evidence shows that CdSe/ZnS Qdots, if appropriately protected, induce negligible toxicity to the model cell system studied here, even when exposed to high dosages. This study indicates that PEG-coated silanized Qdots pose minimal impact to cells and are a very promising alternative to uncoated Qdots.