Evaluation of the repair of diaphyseal fracture of femoral bone using bone marrow mesenchymal stem cells in nicotine-bearing rat

OBJECTIVE

Following bone fractures during accidents, some patients suffer from poor repair of bone fractures and subsequent aesthetic and psychological problems. One of the treatments is based on transplantation of stem cells (seeded on scaffolds) to the lesion site. Bone marrow stromal cells (BMSCs) are multivalent stem cells which are able to reproduce and differentiate into osteogenic cells. The objective of this study was to evaluate the treatment of bone fractures by means of transplantation of the latter cells in rats.

METHODS

In this study, the therapeutic effect of mesenchymal stem cells from bone marrow adipocytes was evaluated in bone fractures. BMSCs were isolated from rat femur. Two sources of differentiated and non-differentiated osteocyte cells were provided and mixed with collagen in order to be transferred to animals divided in three main groups of model: nicotine, non-nicotine and control groups. After four weeks, the repair of the fracture that had been inflicted by a 2‑mm drill into the diaphyseal region of the femoral bone was investigated by radiographic tests and histopathologic staining.

RESULTS

The radiographic results as well as those of histopathologic staining showed that osteogenesis was more intensive in the non-nicotine group than in the nicotine group with differentiated and non-differentiated osteocyte cells.

CONCLUSION

The transplantation of differentiated BMSCs to a bone lesion affected the repair of bone fractures while the nicotine agent played an important role in delaying the bone regeneration (Tab. 1, Fig. 8, Ref. 31).

Assessing the miRNA sponge potential of RUNX1T1 in t(8;21) acute myeloid leukemia

t(8;21) acute myeloid leukemia (AML) is characterized by a translocation between chromosomes 8 and 21 and formation of a distinctive RUNX1-RUNX1T1 fusion transcript. This translocation places RUNX1T1 under control of the RUNX1 promoter leading to a pronounced upregulation of RUNX1T1 transcripts in t(8;21) AML, compared to normal hematopoietic cells. We investigated the role of highly-upregulated RUNX1T1 under the hypothesis that it acts as competing endogenous RNA (ceRNA) titrating microRNAs (miRNAs) away from their target transcripts and thus contributes to AML formation. Using publicly available t(8;21) AML RNA-Seq and miRNA-Seq data available from The Cancer Genome Atlas (TCGA) project, we obtained a network consisting of 605 genes that may act as ceRNAs competing for miRNAs with the suggested RUNX1T1 miRNA sponge. Among the 605 ceRNA candidates, 121 have previously been implied in cancer development. Players in the integrin, cadherin, and Wnt signaling pathways affected by the RUNX1T1 sponge were overrepresented. Finally, among a set of 21 high interest RUNX1T1 ceRNAs we found multiple genes that have previously been linked to AML formation. In conclusion, our study offers a novel look at the role of the RUNX1-RUNX1T1 fusion transcript in t(8;21) AML beyond previously investigated genetic and epigenetic aberrations.

Abstract 196: A SNP in the 3′-untranslated region of FZD4 linked to lung cancer survival modulates a miRNA-mediated FZD4 transcript binding, cleavage, expression, and Wnt-signaling in NSCLC cells

Single nucleotide polymorphisms (SNPs) in miRNA genes and miRNA-associated pathways (miR-SNPs) are predicted to have significant effects on gene expression and cellular processes by disrupting miRNA biogenesis and modulating miRNA-mRNA interactions. We identified several germline SNPs at potential miRNA-binding sites in the 3′ untranslated regions (3′UTRs) of genes in the wingless (Wnt) signaling pathway to be significantly associated with overall survival in NSCLC patients. SNP (rs713065 with a C allele) in the 3′UTR of the FZD4 gene in the Wnt canonical pathway displayed a significant association with decreased risk of death in early NSCLC patients. We aimed to determine the biological function and clinical relevance of this novel epidemiological FZD4-miR-SNP (rs713065) in NSCLC by identifying specific miRNAs that could directly interact with the FZD4-miR-SNP locus and assessing the effect of such a SNP and associated miRNAs on target gene regulation and NSCLC prognosis. We used a novel stem-loop array-reverse transcription-PCR (SLA-RT-PCR) assay to assess miRNA:target mRNA interaction at the specific SNP locus and detected miRNA-mediated FZD4 mRNA cleavage and 3′-uridylation activities in FZD4-SNP (C, rs713065) allele-bearing NSCLC cells H1299 and H322, but not in FZD4-WT (T) allele-containing A549 and normal human bronchial epithelial cells. A significant down regulation of GFP and Luciferase (Luc) gene and protein expression in the presence of FZD4-SNP was detected in NSCLC cell lines using both GFP-SNP and Dual-Luc-SNP reporter systems. The presence of the FZD4-SNP in the 3′UTR also down-regulated the ectopic expression of the host FZD4 gene and protein and inhibited tumor colony formation and tumor cell mobility in NSCLC cells. We identified miR-204 as a potential miRNA candidate that differentially interacts with and targets allelic variants at FZD4-miR-SNP (rs713065) loci. Target mRNA cleavage was detected at the SNP C allele site but not at the WT-allele T site in H1299 cells after co-transfection with a GFP-FZD4-SNP reporter and miR-204 expression constructs by SLA-RT-PCR. A significant correlation of miR-204 with FZD4 gene expression was also detected in NSCLC cell lines and primary tumor specimens in various miRNA expression profiling databases. Our findings suggest that the miR-204 binding site at the SNP (rs713065) loci in the 3′UTR of FZD4 may influence survival in NSCLC by modulating FZD4 expression and the Wnt/FZD4-signaling driven tumor cell proliferation and progression. (This study is partially supported by NIH/NCI grants Lung SPORE 5P50CA070907 and R01CA176568, a CPRIT Grant and a MDACC Moonshot Program Grant)

Citation Format: Jing Lin, Roza Zandi, Jian Gu, Yuanqin Ye, Alexander Pertsemlidis, Xifeng Wu, Jack A. Roth, Lin Ji. A SNP in the 3′-untranslated region of FZD4 linked to lung cancer survival modulates a miRNA-mediated FZD4 transcript binding, cleavage, expression, and Wnt-signaling in NSCLC cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 196. doi:10.1158/1538-7445.AM2015-196

Demonstration of angle-dependent Casimir force between corrugations

The normal Casimir force between a sinusoidally corrugated gold coated plate and a sphere was measured at various angles between the corrugations using an atomic force microscope. A strong dependence on the orientation angle of the corrugation is found. The measured forces were found to deviate from the proximity force approximation and are in agreement with the theory based on the gradient expansion including correlation effects of geometry and material properties. We analyze the role of temperature. The obtained results open new opportunities for control of the Casimir effect in micromechanical systems.

The effect of adenovirus-mediated gene expression of FHIT in small cell lung cancer cells

The candidate tumor suppressor fragile histidine traid (FHIT) is frequently inactivated in small cell lung cancer (SCLC). Mutations in the p53 gene also occur in the majority of SCLC leading to the accumulation of the mutant protein. Here we evaluated the effect of FHIT gene therapy alone or in combination with the mutant p53-reactivating molecule, PRIMA-1(Met)/APR-246, in SCLC. Overexpression of FHIT by recombinant adenoviral vector (Ad-FHIT)-mediated gene transfer in SCLC cells inhibited their growth by inducing apoptosis and when combined with PRIMA-1(Met)/APR-246, a synergistic cell growth inhibition was achieved.

PRIMA-1Met/APR-246 induces apoptosis and tumor growth delay in small cell lung cancer expressing mutant p53

PURPOSE

Small cell lung cancer (SCLC) is a highly malignant disease with poor prognosis, necessitating the need to develop new and efficient treatment modalities. PRIMA-1(Met) (p53-dependent reactivation of massive apoptosis), also known as APR-246, is a small molecule, which restores tumor suppressor function to mutant p53 and induces cancer cell death in various cancer types. Since p53 is mutated in more than 90% of SCLC, we investigated the ability of PRIMA-1(Met) to induce apoptosis and inhibit tumor growth in SCLC with different p53 mutations.

EXPERIMENTAL DESIGN

The therapeutic effect of PRIMA-1(Met)/APR-246 was studied in SCLC cells in vitro using cell viability assay, fluorescence-activated cell-sorting analysis, p53 knockdown studies, and Western blot analyses. The antitumor potential of PRIMA-1(Met)/APR-246 was further evaluated in two different SCLC xenograft models.

RESULTS

PRIMA-1(Met)/APR-246 efficiently inhibited the growth of the SCLC cell lines expressing mutant p53 in vitro and induced apoptosis, associated with increased fraction of cells with fragmented DNA, caspase-3 activation, PARP cleavage, Bax and Noxa upregulation and Bcl-2 downregulation in the cells. The growth suppressive effect of PRIMA-1(Met)/APR-246 was markedly reduced in SCLC cell lines transfected with p53 siRNA, supporting the role of mutant p53 in PRIMA-1(Met)/APR-246-induced cell death. Moreover, in vivo studies showed significant antitumor effects of PRIMA-1(Met) after i.v. injection in SCLC mouse models with no apparent toxicity.

CONCLUSION

This study is the first to show the potential use of p53-reactivating molecules such as PRIMA-1(Met)/APR-246 for the treatment of SCLC.

Mechanisms for oncogenic activation of the epidermal growth factor receptor

The Epidermal growth factor receptor (EGFR) is a membrane spanning glycoprotein, which frequently has been implicated in various cancer types. The mechanisms by which EGFR becomes oncogenic are numerous and are often specific for each cancer type. In some tumors, EGFR is activated by autocrine/paracrine growth factor loops, whereas in others activating mutations promote EGFR signaling. Overexpression and/or amplification of the EGFR gene are prevalent in many cancer types leading to aberrant EGFR signaling. In addition, failure to attenuate receptor signaling by receptor downregulation can also lead to cellular transformation. Heterodimerization of EGFR with ErbB2 inhibits downregulation of EGFR and thereby prolongs growth factor signaling. This also indicates that cross-talk between EGFR and heterologous receptor systems serves as another mechanism for oncogenic activation of EGFR. Because of its role in tumor promotion, the EGFR has been intensely studied as a therapeutic target. There are currently two major mechanisms by which the EGFR is targeted: antibodies binding to the extracellular domain of EGFR and small-molecule tyrosine-kinase inhibitors. However, tumorigenesis is a multi-step process involving several mutations, which might explain why EGFR therapeutics has only been partially successful. This highlights the importance of pinpointing the mechanisms by which EGFR becomes oncogenic in a particular cancer. In this review, each of the above mentioned mechanisms will be discussed, as a detailed molecular and genetic understanding of how EGFR contributes to the malignant phenotype might offer new promise for the design, development and clinical evaluation of future tumor-specific anticancer approaches.

EGFRvIII escapes down-regulation due to impaired internalization and sorting to lysosomes

EGFRvIII is a mutant variant of the epidermal growth factor receptor (EGFR) found exclusively in various cancer types. EGFRvIII lacks a large part of the extracellular domain and is unable to bind ligands; however, the receptor is constitutively phosphorylated and able to activate downstream signaling pathways. Failure to attenuate signaling by receptor down-regulation could be one of the major mechanisms by which EGFRvIII becomes oncogenic. Using a cell system expressing either EGFR or EGFRvIII with no expression of other EGFR family members and with endogenous levels of key degradation proteins, we have investigated the down-regulation of EGFRvIII and compared it to that of EGFR. We show that, in contrast to EGFR, EGFRvIII is inefficiently degraded. EGFRvIII is internalized, but the internalization rate of the mutated receptor is significantly less than that of unstimulated EGFR. Moreover, internalized EGFRvIII is recycled rather than delivered to lysosomes. EGFRvIII binds the ubiquitin ligase c-Cbl via Grb2, whereas binding via phosphorylated tyrosine residue 1045 seems to be limited. Despite c-Cbl binding, the receptor fails to become effectively ubiquitinylated. Thus, our results suggest that the long lifetime of EGFRvIII is caused by inefficient internalization and impaired sorting to lysosomes due to lack of effective ubiquitinylation.

Radial distribution function of rod-like polyelectrolytes

We study the effect of electrostatic interactions on the distribution function of the end-to-end distance of a single polyelectrolyte chain in the rod-like limit. The extent to which the radial distribution function of a polyelectrolyte is reproduced by that of a wormlike chain with an adjusted effective persistence length is investigated. Strong evidence is found for a universal scaling formula connecting the effective persistence length of a polyelectrolyte with the strength of the electrostatic interaction and the Debye screening length.

Constraints, histones, and the 30-nm spiral

We investigate the mechanical stability of a segment of DNA wrapped around a histone in the nucleosome configuration, under the assumption that the proper model for this packaging arrangement is that of an elastic rod that is free to twist and that writhes subject to mechanical constraints. We find that the number of constraints required to stabilize the nuclesome configuration is determined by the length of the segment, the number of times the DNA wraps around the histone spool, and the specific constraints utilized. While it can be shown that four constraints suffice, in principle, to insure stability of the nucleosome, a proper choice must be made to guarantee the effectiveness of this minimal number. The optimal choice of constraints appears to bear a relation to the existence of a spiral ridge on the surface of the histone octamer. The particular configuration that we investigate is related to the 30-nm spiral, a higher-order organization of DNA in chromatin.