Adriana Aguilar-Mahecha

Mesenchymal Stromal Cells Ameliorate Experimental Autoimmune Encephalomyelitis by Inhibiting CD4 Th17 T Cells in a CC Chemokine Ligand 2-Dependent Manner

The administration of ex vivo culture-expanded mesenchymal stromal cells (MSCs) has been shown to reverse symptomatic neuroinflammation observed in experimental autoimmune encephalomyelitis (EAE). The mechanism by which this therapeutic effect occurs remains unknown. In an effort to decipher MSC mode of action, we found that MSC conditioned medium inhibits EAE-derived CD4 T cell activation by suppressing STAT3 phosphorylation via MSC-derived CCL2. Further analysis demonstrates that the effect is dependent on MSC-driven matrix metalloproteinase proteolytic processing of CCL2 to an antagonistic derivative. We also show that antagonistic CCL2 suppresses phosphorylation of AKT and leads to a reciprocal increased phosphorylation of ERK associated with an up-regulation of B7.H1 in CD4 T cells derived from EAE mice. CD4 T cell infiltration of the spinal cord of MSC-treated group was robustly decreased along with reduced plasma levels of IL-17 and TNF-α levels and in vitro from restimulated splenocytes. The key role of MSC-derived CCL2 was confirmed by the observed loss of function of CCL2−/− MSCs in EAE mice. In summary, this is the first report of MSCs modulating EAE biology via the paracrine conversion of CCL2 from agonist to antagonist of CD4 Th17 cell function.

PDK1-Dependent Metabolic Reprogramming Dictates Metastatic Potential in Breast Cancer

Metabolic reprogramming is a hallmark of cellular transformation, yet little is known about metabolic changes that accompany tumor metastasis. Here we show that primary breast cancer cells display extensive metabolic heterogeneity and engage distinct metabolic programs depending on their site of metastasis. Liver-metastatic breast cancer cells exhibit a unique metabolic program compared to bone- or lung-metastatic cells, characterized by increased conversion of glucose-derived pyruvate into lactate and a concomitant reduction in mitochondrial metabolism. Liver-metastatic cells displayed increased HIF-1α activity and expression of the HIF-1α target Pyruvate dehydrogenase kinase-1 (PDK1). Silencing HIF-1α reversed the glycolytic phenotype of liver-metastatic cells, while PDK1 was specifically required for metabolic adaptation to nutrient limitation and hypoxia. Finally, we demonstrate that PDK1 is required for efficient liver metastasis, and its expression is elevated in liver metastases from breast cancer patients. Our data implicate PDK1 as a key regulator of metabolism and metastatic potential in breast cancer.

CXCR4 peptide antagonist inhibits primary breast tumor growth, metastasis and enhances the efficacy of anti-VEGF treatment or docetaxel in a transgenic mouse model

CXCR4 is a chemokine receptor implicated in the homing of cancer cells to target metastatic organs, which overexpress its ligand, stromal cell‐derived factor (SDF)‐1. To determine the efficacy of targeting CXCR4 on primary tumor growth and metastasis, we used a peptide inhibitor of CXCR4, CTCE‐9908, that was administered in a clinically relevant approach using a transgenic breast cancer mouse model. We first performed a dosing experiment of CTCE‐9908 in the PyMT mouse model, testing 25, 50 and 100 mg/kg versus the scrambled peptide in groups of 8–16 mice. We then combined CTCE‐9908 with docetaxel or DC101 (an anti‐VEGFR2 monoclonal antibody). We found that increasing doses of CTCE‐9908 alone slowed the rate of tumor growth, with a 45% inhibition of primary tumor growth at 3.5 weeks of treatment with 50 mg/kg of CTCE‐9908 (p = 0.005). Expression levels of VEGF were also found to be reduced by 42% with CTCE‐9908 (p = 0.01). In combination with docetaxel, CTCE‐9908 administration decreased tumor volume by 38% (p = 0.02), an effect that was greater than that observed with docetaxel alone. In combination with DC101, CTCE‐9908 also demonstrated an enhanced effect compared to DC101 alone, with a 37% decrease in primary tumor volume (p = 0.01) and a 75% reduction in distant metastasis (p = 0.009). In combination with docetaxel or an anti‐angiogenic agent, the anti‐tumor and anti‐metastatic effects of CTCE‐9908 were markedly enhanced, suggesting potentially new effective combinatorial therapeutic strategies in the treatment of breast cancer, which include targeting the SDF‐1/CXCR4 ligand/receptor pair.

Expression of Stress Response Genes in Germ Cells During Spermatogenesis

Abstract During germ cell development different spermatogenic cell types show remarkable variation in their susceptibility to stressful stimuli. Various cellular mechanisms are triggered in germ cells after exposure to stress, but the expression of only a few of the genes involved in such pathways has been studied during spermatogenesis. In the present study we determined the expression profiles of 216 stress response genes in isolated rat germ cells (pachytene spermatocytes, and round and elongating spermatids) using cDNA atlas arrays. Of the 216 genes studied, 86 were detected in pachytene spermatocytes, 82 in round spermatids, and 52 in elongating spermatids. Fifty percent (48) of the total number of genes detected during spermatogenesis were detected in all three cell types while nearly 25% (25) were expressed exclusively in pachytene spermatocytes and round spermatids; some cell specific transcripts were observed also. The use of the K means clustering method allowed us to group genes by their pattern of expression during spermatogenesis; five specific expression profiles were obtained and analyzed. To determine how stress response genes are regulated throughout spermatogenesis, we examined the expression of genes involved in stress response mechanisms such as heat shock proteins-chaperones, DNA repair, and oxidative stress. Genes belonging to these families were differentially expressed during germ cell development. We suggest that the differential expression of stress response genes during spermatogenesis contributes to the selectivity of the susceptibility of germ cells to stress.

Chronic Cyclophosphamide Treatment Alters the Expression of Stress Response Genes in Rat Male Germ Cells

Abstract Increases in the survival rate of men treated with chemotherapeutic drugs and their desire to have children precipitate concerns about the effects of these drugs on germ cells. Azoospermia, oligospermia, and infertility are common outcomes resulting from treatment with cyclophosphamide, an alkylating agent. Exposure of male rats to cyclophosphamide results in dose-dependent and time-specific adverse effects on progeny outcome. Elucidation of the effects of chronic low-dose cyclophosphamide treatment on the expression of stress response genes in male germ cells may provide insight into the mechanisms underlying such adverse effects. Male rats were gavaged with saline or cyclophosphamide (6 mg/kg) for 4–5 wk; pachytene spermatocytes, round spermatids, and elongating spermatids were isolated; RNA was extracted and probed on cDNA arrays containing 216 cDNAs. After saline treatment, 125 stress response genes were expressed in pachytene spermatocytes (57% of genes studied), 122 in round spermatids (56%), and 83 in elongating spermatids (38%). Cyclophosphamide treatment reduced the number of genes detected in all germ cell types. The predominant effect of chronic cyclophosphamide exposure was to decrease the expression level of genes in pachytene spermatocytes (34% of genes studied), round spermatids (29%), and elongating spermatids (4%). In elongating spermatids only, drug treatment increased the expression of 8% of the genes studied. The expression profiles of genes involved in DNA repair, posttranslational modification, and antioxidant defense in male germ cells were altered by chronic cyclophosphamide treatment. We hypothesize that the effects of cyclophosphamide exposure on germ cell gene expression during spermatogenesis may have adverse consequences on male fertility and progeny outcome.

The effect of pre-analytical variability on the measurement of MRM-MS-based mid- to high-abundance plasma protein biomarkers and a panel of cytokines.

Blood sample processing and handling can have a significant impact on the stability and levels of proteins measured in biomarker studies. Such pre-analytical variability needs to be well understood in the context of the different proteomics platforms available for biomarker discovery and validation. In the present study we evaluated different types of blood collection tubes including the BD P100 tube containing protease inhibitors as well as CTAD tubes, which prevent platelet activation. We studied the effect of different processing protocols as well as delays in tube processing on the levels of 55 mid and high abundance plasma proteins using novel multiple-reaction monitoring-mass spectrometry (MRM-MS) assays as well as 27 low abundance cytokines using a commercially available multiplexed bead-based immunoassay. The use of P100 tubes containing protease inhibitors only conferred proteolytic protection for 4 cytokines and only one MRM-MS-measured peptide. Mid and high abundance proteins measured by MRM are highly stable in plasma left unprocessed for up to six hours although platelet activation can also impact the levels of these proteins. The levels of cytokines were elevated when tubes were centrifuged at cold temperature, while low levels were detected when samples were collected in CTAD tubes. Delays in centrifugation also had an impact on the levels of cytokines measured depending on the type of collection tube used. Our findings can help in the development of guidelines for blood collection and processing for proteomic biomarker studies.

Both t-Darpp and DARPP-32 can cause resistance to trastuzumab in breast cancer cells and are frequently expressed in primary breast cancers

The clinical use of trastuzumab (Herceptin™), a humanized antibody against the HER2 growth factor receptor, has improved survival in patients with breast tumors with ERBB2 amplification and/or over-expression. However, most patients with advanced ERBB2 amplified breast cancers whose tumors initially respond to trastuzumab develop resistance to the drug, leading to tumor progression. To identify factors responsible for acquired resistance to trastuzumab, gene expression profiling was performed on subclones of an ERBB2 amplified breast cancer cell line, BT474, which had acquired resistance to trastuzumab. The most overexpressed gene in these subclones was PPP1R1B, encoding the DARPP-32 phosphatase inhibitor. Western analysis revealed that only the truncated isoform of the DARPP-32 protein, t-Darpp, was overexpressed in the trastuzumab resistant cells. Using gene silencing experiments, we confirmed that t-Darpp over-expression was required for trastuzumab resistance in these cells. Furthermore, transfecting t-Darpp in parental BT-474 cells conferred resistance to trastuzumab, suggesting that t-Darpp expression was sufficient for trastuzumab resistance. We also found that t-Darpp over-expression was associated with Akt activation and that the T75 residue in t-Darpp was required for both Akt activation and trastuzumab resistance. Finally, we found that full-length DARPP-32 and t-Darpp are expressed in a majority of primary breast tumors. Over-expression of full-length DARPP-32 can also confer resistance to trastuzumab and, moreover, is associated with a poor prognostic value in breast cancers. Thus, t-Darpp and DARPP-32 expression are novel prognostic and predictive biomarkers in breast cancer.

Effects of Acute and Chronic Cyclophosphamide Treatment on Meiotic Progression and the Induction of DNA Double-Strand Breaks in Rat Spermatocytes

Abstract Male rats treated with cyclophosphamide, an alkylating agent commonly used clinically in both acute and chronic regimens, present with damaged male germ cells and abnormal progeny outcome. The extent and type of damage induced by cyclophosphamide largely depend on the germ cell type exposed to the drug and its ability to respond to insult. In the present study, the response of pachytene spermatocytes to damage was evaluated by assessing their ability to undergo meiotic G2/MI transition following exposure to acute or chronic cyclophosphamide. Male rats were given an acute high dose (70 mg/kg, once) or chronic low doses (6 mg/kg, daily for 5–6 wk) of cyclophosphamide. Pachytene spermatocytes were isolated, cultured, and induced to undergo G2/MI transition with okadaic acid. To determine the effect of DNA damage on meiotic progression, induction of DNA double-strand breaks was detected after each treatment regimen by the formation of foci of phosphorylated histone H2AX. The transition from G2 to MI was impaired after acute cyclophosphamide treatment; this impairment in the progression of pachytene spermatocytes was correlated with extensive DNA double-strand breaks. In contrast, despite the presence of significant levels of DNA damage, meiotic progression was not impaired in spermatocytes after chronic cyclophosphamide exposure. We suggest that the cell cycle impairment induced after acute cyclophosphamide treatment could be mediated by a G2/M checkpoint activated in response to DNA damage. The absence of impairment after chronic treatment raises concern about the functionality of defense mechanisms in male germ cells after repeated exposure to low doses of genotoxic agents.

Development of reverse phase protein microarrays for the validation of clusterin, a mid-abundant blood biomarker

BackgroundMany putative disease blood biomarkers discovered in genomic and proteomic studies await validation in large clinically annotated cohorts of patient samples. ELISA assays require large quantities of precious blood samples and are not high-throughput. The reverse phase protein microarray platform has been developed for the high-throughput quantification of protein levels in small amounts of clinical samples.ResultsIn the present study we present the development of reverse-phase protein microarrays (RPPMs) for the measurement of clusterin, a mid-abundant blood biomarker. An experimental protocol was optimized for the printing of serum and plasma on RPPMs using epoxy coated microscope slides and a non-denaturing printing buffer. Using fluorescent-tagged secondary antibodies, we achieved the reproducible detection of clusterin in spotted serum and plasma and reached a limit of detection of 780 ng/mL. Validation studies using both spiked clusterin and clinical samples showed excellent correlations with ELISA measurements of clusterin.ConclusionSerum and plasma spotted in the reverse phase array format allow for reliable and reproducible high-throughput validation of a mid-abundant blood biomarker such as clusterin.

Next-generation biobanking of metastases to enable multidimensional molecular profiling in personalized medicine

Great advances in analytical technology coupled with accelerated new drug development and growing understanding of biological challenges, such as tumor heterogeneity, have required a change in the focus for biobanking. Most current banks contain samples of primary tumors, but linking molecular signatures to therapeutic questions requires serial biopsies in the setting of metastatic disease, next-generation of biobanking. Furthermore, an integration of multidimensional analysis of various molecular components, that is, RNA, DNA, methylome, microRNAome and post-translational modifications of the proteome, is necessary for a comprehensive view of a tumor’s biology. While data using such biopsies are now regularly presented, the preanalytical variables in tissue procurement and processing in multicenter studies are seldom detailed and therefore are difficult to duplicate or standardize across sites and across studies. In the context of a biopsy-driven clinical trial, we generated a detailed protocol that includes morphological evaluation and isolation of high-quality nucleic acids from small needle core biopsies obtained from liver metastases. The protocol supports stable shipping of samples to a central laboratory, where biopsies are subsequently embedded in support media. Designated pathologists must evaluate all biopsies for tumor content and macrodissection can be performed if necessary to meet our criteria of >60% neoplastic cells and <20% necrosis for genomic isolation. We validated our protocol in 40 patients who participated in a biopsy-driven study of therapeutic resistance in metastatic colorectal cancer. To ensure that our protocol was compatible with multiplex discovery platforms and that no component of the processing interfered with downstream enzymatic reactions, we performed array comparative genomic hybridization, methylation profiling, microRNA profiling, splicing variant analysis and gene expression profiling using genomic material isolated from liver biopsy cores. Our standard operating procedures for next-generation biobanking can be applied widely in multiple settings, including multicentered and international biopsy-driven trials.