Identification of two Eleusine indica (goosegrass) biotypes of cool-season turfgrass resistant to dithiopyr

BACKGROUND

Turfgrass managers reported poor Eleusine indica control following applications of the mitosis-inhibiting herbicide dithiopyr in cool-season turfgrass. Field, glasshouse, and laboratory experiments were conducted to understand the response of these biotypes to dithiopyr and prodiamine.

RESULTS

In field experiments at two locations with putative dithiopyr-resistant E. indica, preemergence applications of dithiopyr provided no E. indica control. Single applications of the protoporphyrinogen oxidase (PPO)-inhibitor, oxadiazon, provided > 85% control at these locations. When subjected to agar-based bioassays, root growth of putative resistant biotypes planted with 0.01 mmol L^-1 dithiopyr was slightly reduced (< 25%) whereas roots were completely inhibited in the susceptible biotype. Glasshouse whole plant rate-response experiments found that the cytochrome P450 inhibitor, piperonyl butoxide (PBO), did not increase the sensitivity of these putative resistant biotypes to dithiopyr. Sequencing of α-tubulin 1 (TUA1) revealed a Leu-136-Phe substitution in both dithiopyr-resistant populations.

CONCLUSION

Eleusine indica biotypes with resistance to dithiopyr are present in cool-season turfgrass systems in the United States. Resistance is possibly related to a single nucleotide polymorphism (SNP) of an α-tubulin gene. If turfgrass managers suspect resistance to dithiopyr, oxadiazon can still be an effective alternative for preemergence control. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Abstract P6-04-04: Hypoxia Is Associated with Somatic Loss of BRCA1 Protein and Pathway Activity in Triple Negative Breast Cancer

Background: Triple negative breast cancer (TNBC) has loss of BRCA1 activity either through germline mutation, epigenetic modification or negative transcriptional regulators. Yale investigators have demonstrated that tumor hypoxia leads to loss of critical DNA repair activities, including BRCA1, RAD-51 and γ-H2AX (Bindra RS, et al. Cancer Res 2005;65(24): 11597-604). This study was designed to explore the relationship of BRCA1 loss and hypoxia using Carbonic Anhydrase IX (CA-IX), a downstream target of hypoxia-induced factor 1a (HIF-1a), an accepted surrogate biomarker for tumor hypoxia, in TNBC. Methods: Two cohorts of breast tumors from Yale archival materials were studied. The first consisted of 660, unselected breast tumors, the second a cohort of 130 TNBC, both with long term clinical followup. Automated Quantitative Analysis (AQUA) was used to detect the intensity of BRCA1 and CAIX within specific subcellular compartments. CA-IX antibody M75 was provided by the J Zavada lab (1:10000), BRCA1 monoclonal antibody M110 (Ab-1) was purchased from Calbiochem (1:1000). The 130 TNBC cohort was also subjected to whole genome expression analysis. In brief, tissue core biopsies from tumor blocks were subjected to nucleic acid extraction using RecoverAll Total Nucleic Acid Isolation kit (Applied Biosystems) and 600ng total RNA were processed by the Keck Microarray Facility for the Illumina DASL platform. Statistical analysis of gene expression data was carried out in Bioconductor/R software. A set of relevant signatures was selected by enrichment analysis of modules identified by principal component analysis. Signature scores were computed as Pearson correlation between the signature vector of gene contributions and each sample's expression profile for these genes. Results: In the cohort of 660 specimens, 22 were found to have high CA-IX expression score (above cut-off value of 10). Cut-off was based on known positive cell lines and corresponding AQUA scores, as well as visual confirmation of positivity. A negative correlation (Rho=-0.6, p=0.0165) of BRCA1 nuclear protein with CA-IX level was found and this data was reproducible on a duplicate array. Of note, 14 out of 22 hypoxic breast tumors were from triple negative breast cancers (TNBC) (p=0.0034). In the triple negative cohort, CAIX staining was positive in 20 % of cases (n=15/75) and in these samples it was associated with the 2002 van ‘t Veer BRCA1 mutant signature (Rho=0.51). Positive CAIX staining was also associated with worse outcome (p=0.046) as was CAIX mRNA expression (p=0.02).

Conclusions: In human breast tumors BRCA1 nuclear expression is negatively correlated with tumor hypoxia, measured by CAIX. A subset of TNBC has higher levels of hypoxia and BRCA1 signatures. This data suggests that CAIX may be a useful biomarker for BRCA1 loss, and possibly for response to PARP inhibitor therapy. This will be evaluated in our recently completed trial of BSI-201+Irinotecan.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-04.

Activity and mechanism of action of histone deacetylase inhibitors in trastuzumab resistant breast cancer

Abstract #3060

Introduction: The Her2 antibody trastuzumab (T) is the first biological therapy that has proven the value of Her2 blockade in breast cancer. However, not all patients respond to trastuzumab and relapses occur after this treatment. Several studies suggest that histone deacetylase inhibitors (HDACis) are active in Her2-amplified breast cancer but none of them have addressed the role of HDACis in trastuzumab-resistant breast cancer. HDACis act by inhibiting the deacetylation of histones and other non-histone proteins such as Hsp90. Our goal is to study the activity, optimal sequencing and mechanism of action of HDACis in Her2-amplified cell lines, which demonstrate either de novo or acquired resistance to trastuzumab.&#x2028; Methods: T-sensitive and Her2-overexpressing BT474 & SkBr3, T-resistant BT474 and de novo T-resistant cell lines MDA-MB361, MDA-MB453, UACC812 and UACC893 were used for all experiments. The HDACi TSA (0-1uM) and trastuzumab at 100ug/mL were used for proliferation assays applying WST1 reagent (Roche). Western-immunoblotting was performed using cell lysates from untreated and treated cells. Proteolytic cleavage of caspase-3 and PARP was analyzed as indicator for apoptosis, Akt expression and phosphorylation for survival, Her2 and Erk1/2 expression and phosphorylation for proliferation and Hsp90 and Hsp70 were analyzed as key enzymes for chaperone activity.&#x2028; Results: TSA inhibited proliferation in all cell lines [IC50 100-300 nM]. The addition of trastuzumab was antagonistic in de novo T-resistant cell lines MDA MB 453, UACC 812 and 893 but did not change the effect induced by TSA in acquired T-resistant cells (BT474_H100). Her2 expression decreased in TSA and TSA+T treated cells but not in cells treated with trastuzumab alone. Erk1/2 phosphorylation decreased in TSA and TSA+T treated cells but was not affected by trastuzumab alone. Similar phosphorylation patterns were observed regarding Akt. Of note, Akt, Erk1/2, Hsp90 and Hsp70 levels did not change. Finally, TSA induced caspase-3 and PARP cleavage when given as single agent or in combination with trastuzumab.&#x2028; Discussion: This study suggests that HDACis are active in both trastuzumab-sensitive and de novo or acquired trastuzumab-resistant cell lines. However, use of trastuzumab together with TSA may be antagonistic in tumors that are resistant against trastuzumab. Further studies are required in these cell lines in order to elucidate the mechanism of resistance against trastuzumab and the mechanism of the here observed antagonistic effect between trastuzumab and TSA.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3060.

MicroRNA profiling of triple negative breast cancer: predicting outcome and targets

Abstract #2040

Background: Breast tumors have been categorized on their molecular basis into ER- and/or PR positive, HER2 gene amplified and triple-negative tumors. Among these, triple-negative tumors represent the most aggressive subclass of breast tumors that are most prevalent in African American women. Currently, no effective targeted therapies or potential biomarkers have been identified to predict outcome within this group.&#x2028; MicroRNAs(miRNAs) are global regulatory RNAs misregulated in almost every cancer and may function as tumor suppressor genes or proto-oncogenes. Specific miRNAs are aberrantly expressed in breast tumor versus normal tissue. Although miRNA expression profiles for the ER positive and HER2 positive subtype have been reported, the triple negative subtype remains to be studied.&#x2028; Hypothesis: We hypothesize that identifying the miRNA signature of the triple negative tumors as a subclass as well as differences in this signature between triple negative patients with known outcome will lead to the identification of miRNAs predictive of outcome. For these studies we will use a large, well-annotated database of triple negative breast cancer patients with long-term follow-up. We will then test the identified miRNAs in a well-established cell-culture system to determine which miRNAs can act as potential therapeutic agents in triple negative breast tumors.&#x2028; Study Design: We have performed miRNA microarray analysis to identify miRNA expression patterns in over 40 triple negative breast cancers using both fresh frozen tumors and formalin-fixed paraffin embedded (FFPE) samples. We have used the Ambion miRNA Taqman Low Density Array for analysis of these samples. The potential of specific miRNAs to predict outcome is currently being determined using statistical analysis.&#x2028; Results: Our initial studies indicated that the triple negative subgroup has a significantly different miRNA signature than the HER2 positive subtype. We also additionally found unique miRNA expression patterns that may define triple negative cancers as a class. The triple negative tumors are known to have low levels of p53 and our microarray data showed that miR-34a which has been shown to be co-regulated by p53 and has similar expression levels as p53 in tissues, was significantly low in the triple negative compared to HER 2 positive breast cancer. We are currently evaluating the impact of altering mir-34 expression in these cell lines in vitro.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2040.

Induction of Erythropoiesis by MHC-Mediated Cognate Interactions between B- and T-Cells

We have previously shown that the expression of membrane burst-promoting activity (mBPA), an erythropoietic cytokine, by B-lymphocytes is augmented by the addition of allogeneic effector cells to the B-cells. Here, we have examined immune mechanisms involved in the induction/promotion of erythropoiesis as assessed by the capacity of autologous and allogeneic peripheral blood lymphocytes to augment burst-forming unit-erythroid (BFU-E) in normal human bone marrow cells in vitro. Preincubation of mBPA-expressing human B-cells with monoclonal antibodies to major histocompatibility complex (MHC) antigens, abrogated erythropoietic activity of both autologous and allogeneic lymphocytes, suggesting that MHC antigens play a role in regulating the expression of the erythroid growth factor. Inhibition of BFU-E proliferation was also evident when antibodies to MHC class-I or class-II antigens were added directly to marrow culture. Furthermore, addition of anti-CD4 antibody to the cultures of PBL and autologous target BM cells markedly reduced erythroid proliferation induced by PBL. By contrast, anti-CD8 and control (UPC-10) monoclonal antibodies had no effect. These results provide evidence that MHC-mediated cognate interactions between T- and B-lymphocytes may participate in the control of erythropoiesis, either directly or by modulating mBPA function.

Human macrophage colony-stimulating factor is expressed at and shed from the cell surface

Surface membrane-associated growth factors are being recognized as important for developmental processes, including cell assembly, differentiation, and growth. To investigate the role of membrane-bound macrophage colony-stimulating factor (M-CSF) in myelopoiesis, and whether this factor is released from the cell surface in association with shed membrane-derived vesicles, COS-1 cells were transfected with cDNAs for M-CSF-tau (containing the transmembrane domain) or a soluble mutant form of the molecule lacking the transmembrane domain ([s]M-CSF-alpha). COS-1 cells transfected with either cDNA released activity into the spent culture medium. Conditioned medium was separated by centrifugation into supernatants and pellets were found to contain plasma membrane-derived vesicles by transmission electron microscopy. When medium fractions were assayed in marrow cultures, activity was localized to shed plasma membrane-derived vesicles in medium conditioned by cells transfected with cDNA for M-CSF-tau and in the vesicle-free supernatants of medium conditioned by cells transfected with cDNA for [s]M-CSF-alpha. In addition, nuclear, mitochondrial, and plasma membrane subfractions of stably transfected cells were prepared and assayed for activity. Concentration-dependent stimulation of macrophage colony formation was observed with purified plasma membranes (but not nuclear or cytosolic proteins) from cells transfected with cDNA for M-CSF-tau. By contrast, membranes from untransfected cells and cells transfected with cDNA for [s]M-CSF-alpha or control DNA expressed no activity. Together, the data indicate that human M-CSF is expressed at the cell surface and exfoliated in association with surface membrane-derived vesicles.

Modulation of hematopoiesis by lymphocyte membrane-derived components

Membrane bound erythroid burst-promoting activity (mBPA) is an integral membrane protein that is present on normal B-cells and some activated T-cells, that induces burst-forming units-erythroid (BFU-E) when cultured with human erythropoietin (rHuEpo). Plasma membranes and vesicles shed from the leukemic A-1 cell line express mBPA. This activity derived from both A-1 cells and normal B-cells can be immunoadsorbed by the D3A4 antibody raised against mBPA. In this study, we demonstrate that interferon-gamma (IFN-gamma) suppresses BFU-E proliferation when added directly to culture of normal human bone marrow cells and in the absence and presence of A-1 cells. However, FACS analysis reveals that IFN-gamma enhances the surface expression of mBPA on A-1 cells. The role of IFN-gamma in modulating erythropoiesis in vitro is discussed with respect to the role of shedding membrane-derived vesicles from the B-cell surface.