A molecular optomechanics approach reveals functional relevance of force transduction across talin and desmoplakin

Many mechanobiological processes that govern development and tissue homeostasis are regulated on the level of individual molecular linkages, and a number of proteins experiencing piconewton-scale forces in cells have been identified. However, under which conditions these force-bearing linkages become critical for a given mechanobiological process is often still unclear. Here, we established an approach to revealing the mechanical function of intracellular molecules using molecular optomechanics. When applied to the integrin activator talin, the technique provides direct evidence that its role as a mechanical linker is indispensable for the maintenance of cell-matrix adhesions and overall cell integrity. Applying the technique to desmoplakin shows that mechanical engagement of desmosomes to intermediate filaments is expendable under homeostatic conditions yet strictly required for preserving cell-cell adhesion under stress. These results reveal a central role of talin and desmoplakin as mechanical linkers in cell adhesion structures and demonstrate that molecular optomechanics is a powerful tool to investigate the molecular details of mechanobiological processes.

Association of high miR-27a, miR-206, and miR-214 expression with poor patient prognosis and increased chemoresistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents the most aggressive breast cancer subtype, associated with early metastasis and recurrence as well as poor patient outcome. TNBC does not or weakly respond to hormonal or HER2-targeted therapies. Therefore, there is a strong need to identify other potential molecular targets for TNBC therapy. Micro-RNAs play important roles in the post-transcriptional regulation of gene expression. Thus, micro-RNAs, displaying an association between elevated expression and poor patient prognosis, may represent candidates for such novel tumor targets. In the present study, we evaluated the prognostic impact of miR-27a, miR-206, and miR-214 in TNBC via qPCR in tumor tissue (n=146). In univariate Cox regression analysis, elevated expression of all three analyzed micro-RNAs was significantly associated with shortened disease-free survival (hazard ratio [HR] for miR-27a: 1.85, P=0.038; miR-206: 1.83, P=0.041; miR-214: 2.06, P=0.012). In multivariable analysis, the micro-RNAs remained independent biomarkers for disease-free survival (HR for miR-27a: 1.99, P=0.033; miR-206: 2.14, P=0.018; miR-214: 2.01, P=0.026). Furthermore, our results suggest that elevated levels of these micro-RNAs are linked to enhanced resistance to chemotherapy. Based on the association of high expression levels with shortened patient survival and increased chemoresistance, miR-27a, miR-206, and miR-214 may represent novel molecular targets for TNBC.

Greeen tea extracts lower serum folates in rats at very high dietary concentrations only and do not affect plasma folates in a human pilot study

Green tea catechins (GTC) have been shown to inhibit the activities of enzymes involved in folate uptake. Hence, regular green tea drinkers may be at risk of impaired folate status. The present experiments aimed at studying the impact of dietary GTC on folate concentrations and metabolism. In a human pilot study (parallel design) healthy men consumed for 3 weeks 6 capsules (approximately 670 mg GTC) per day (2 capsules with each principal meal) containing aqueous extracts of the leaves of Camellia sinensis (n=17) or placebo (n=16). No differences in plasma folate concentrations were observed between treatments. We further fed groups of 10 male rats diets fortified with 0, 0.05, 0.5, 1, or 5 g GTC/kg for 6 weeks. Only at the highest intake, GTC significantly decreased serum 5-methyl-tetrahydrofolate concentrations in rats, while mRNA concentrations of reduced folate carrier, proton-coupled folate transporter/heme carrier protein 1, and dihydrofolate reductase (DHFR) remained unchanged in intestinal mucosa. Using an in vitro enzyme activity assay, we observed a time- and dose-dependent inhibition of DHFR activity by epigallocatechin gallate and a green tea extract. Our data suggest that regular green tea consumption is unlikely to impair folate status in healthy males, despite the DHFR inhibitory activity of GTC.

Allo-SCT conditioning for myelodysplastic syndrome and acute myeloid leukemia with clofarabine, cytarabine and ATG

The application of myeloablative Allo-SCT is limited by its associated morbidity and mortality. Reduced-intensity conditioning regimens attempt to diminish these, but are associated with a higher risk of disease relapse. Given the evidence of activity of clofarabine and cytarabine in myelodysplastic syndrome/acute myeloid leukemia (MDS/AML), we explored a novel reduced-intensity conditioning regimen based on this backbone. Patients received clofarabine 40 mg/m(2) i.v. on days -6 to -2, cytarabine 1 g/m(2) i.v. on days -6 to -2 and anti-thymocyte globulin (ATG) 1 mg/kg on day -4 and 2.5 mg/kg x 2 days on days -3 and -2. Seven patients were enrolled. Their median age was 54 years; three were with MDS and four with AML. The median duration of neutropenia was 14 days and that of thrombocytopenia was 22 days. Toxicities included hand-foot syndrome (57% grade 2), elevated alanine aminotransferase (ALT) (57% grade 3), elevated aspartate aminotransferase (AST) (86% grade 3) and hyperbilirubinemia (29% grade 3-5). No acute GVHD was observed. Enrollment to the trial was halted after three of the first seven patients expired on days +15, +26 and +32. Three of the four surviving patients have relapsed with a median TTP of 152 days. This regimen was not sufficiently immunosuppressive to ensure engraftment, and was associated with substantial morbidity and mortality.

Vancomycin-resistant enterococcal bloodstream infections on a hematopoietic stem cell transplant unit: are the sick getting sicker?

Patients with hematologic malignancies and hematopoietic stem cell transplant (HSCT) recipients are at high risk for bacterial bloodstream infections (BSI) owing to resistant organisms. Data describing the outcomes of vancomycin-resistant enterococcal (VRE) BSI in this patient population are limited. We performed a retrospective cohort study of all cases of VRE BSI that occurred between February 1996 and December 2002 on the Leukemia/HSCT unit at Barnes-Jewish Hospital. There were 68 episodes of VRE BSI in 60 patients with acute (53%) or chronic (8%) leukemia, non-Hodgkin's lymphoma (22%) or other malignant hematologic disorders (17%). A total of 13, 32 and 32% were recipients of autologous, related and matched-unrelated transplants, respectively. Forty-two of allograft recipients had active acute graft-versus-host disease (GVHD) and 32% chronic GVHD. Only 57% were neutropenic, 52% had refractory/relapsed malignancy and 60% had end organ dysfunction with a median APACHE II score of 17. Median survival after VRE BSI was 19 days. Pneumonia, receipt of anti-fungal drugs and low APACHE II score at the time of the VRE BSI remained significant risk factors for death on multivariable analysis. Our analysis suggests that in patients with hematological malignancies or HSCT, VRE may not have the behavior of a virulent pathogen. VRE BSI may simply be a marker of these patients' already existing critical medical condition.

The structure and regulation of the oxytocin receptor

The oxytocin receptor (OTR) is part of an ancient hormone system expressed in diverse phyla in relation to acute reproductive smooth muscle responses, such as egg-laying, birth, or milk letdown. The regulation of the OTR gene, while correlating with steroid levels in vivo, remains elusive. There appear to be both inhibitory and stimulatory influences acting upon a constitutive pattern of basal expression. We have found no evidence, however, for an effect of the sex steroids either directly on gene transcription, or on the receptor itself at the protein level. In the prostatic carcinoma cell line Du145, we have shown that up-regulation of the OTR gene transcription can be effected by cAMP. In an attempt to characterize the expression of the OTR protein in vivo, we have shown, using ligand-blotting, that the OTR can be expressed at different sizes in transfected cells and in myometrium. Also, in the myometrium at term, immunohistochemistry suggests that there is both an increase in OTR protein per cell, as well as in the number of smooth muscle cells expressing OTR, emphasizing that perinatal changes are the results of both individual gene activation events and gross cellular differentiation. The OTR is a valuable model system reflecting molecular changes in the perinatal period. When we understand how this important molecule is regulated, we will also be a long way towards understanding the mechanisms controlling myometrial contractility at birth. Experimental Physiology (2001) 86.2, 289-296.