Localization of mRNAs at the front of migrating cells is a widely used mechanism that functionally supports efficient cell movement. It is observed in single cells on two-dimensional surfaces, as ...well as in multicellular three-dimensional (3D) structures and in tissue in vivo. 3D multicellular cultures can reveal how the topology of the extracellular matrix and cell-cell contacts influence subcellular mRNA distributions. Here we describe a method for mRNA imaging in an inducible system of collective cancer cell invasion. MDA-MB-231 cancer cell spheroids are embedded in Matrigel, induced to invade, and processed to image mRNAs with single-molecule sensitivity. An analysis algorithm is used to quantify and compare mRNA distributions at the front of invasive leader cells. The approach can be easily adapted and applied to analyze RNA distributions in additional settings where cells polarize along a linear axis.
A critical early event in the HIV type 1 (HIV-1) particle assembly pathway is the targeting of the Gag protein to the site of virus assembly. In many cell types, assembly takes place predominantly at ...the plasma membrane. Cellular factors that regulate Gag targeting remain undefined. The phosphoinositide phosphatidylinositol (4,5) bisphosphate PI(4,5) P2 controls the plasma membrane localization of a number of cellular proteins. To explore the possibility that this lipid may be involved in Gag targeting and virus particle production, we overexpressed phosphoinositide 5-phosphatase IV, an enzyme that depletes cellular PI(4,5) P2, or overexpressed a constitutively active form of Arf6 (Arf6/Q67L), which induces the formation of PI(4,5) P2-enriched endosomal structures. Both approaches severely reduced virus production. Upon 5-phosphatase IV overexpression, Gag was no longer localized on the plasma membrane but instead was retargeted to late endosomes. Strikingly, in cells expressing Arf6/Q67L, Gag was redirected to the PI(4,5) P2-enriched vesicles and HIV-1 virions budded into these vesicles. These results demonstrate that PI(4,5) P2 plays a key role in Gag targeting to the plasma membrane and thus serves as a cellular determinant of HIV-1 particle production.
Localization of RNAs at protrusive regions of cells is important for single-cell migration on two-dimensional surfaces. Protrusion-enriched RNAs encode factors linked to cancer progression, such as ...the RAB13 GTPase and the NET1 guanine nucleotide exchange factor, and are regulated by the tumor-suppressor protein APC. However, tumor cells in vivo often do not move as single cells but rather utilize collective modes of invasion and dissemination. Here, we developed an inducible system of three-dimensional (3D) collective invasion to study the behavior and importance of protrusion-enriched RNAs. We find that, strikingly, both the RAB13 and NET1 RNAs are enriched specifically at the invasive front of leader cells in invasive cell strands. This localization requires microtubules and coincides with sites of high laminin concentration. Indeed, laminin association and integrin engagement are required for RNA accumulation at the invasive front. Importantly, perturbing RNA accumulation reduces collective 3D invasion. Examination of in vivo tumors reveals a similar localization of the RAB13 and NET1 RNAs at potential invasive sites, suggesting that this mechanism could provide a targeting opportunity for interfering with collective cancer cell invasion.
Proinflammatory signaling pathways are commonly up-regulated in breast cancer. In estrogen receptor-negative (ER⁻) and triple-negative breast cancer (TNBC), nitric oxide synthase-2 (NOS2) and ...cyclooxygenase-2 (COX2) have been described as independent predictors of disease outcome. We further explore these findings by investigating the impact of their coexpression on breast cancer survival. Elevated coexpression of NOS2/COX2 proteins is a strong predictor of poor survival among ER⁻ patients (hazard ratio: 21). Furthermore, we found that the key products of NOS2 and COX2, NO and prostaglandin E2 (PGE2), respectively, promote feed-forward NOS2/COX2 crosstalk in both MDA-MB-468 (basal-like) and MDA-MB-231 (mesenchymal-like) TNBC cell lines in which NO induced COX2 and PGE2 induced NOS2 proteins. COX2 induction by NO involved TRAF2 activation that occurred in a TNFα-dependent manner in MDA-MB-468 cells. In contrast, NO-mediated TRAF2 activation in the more aggressive MDA-MB-231 cells was TNFα independent but involved the endoplasmic reticulum stress response. Inhibition of NOS2 and COX2 using amino-guanidine and aspirin/indomethacin yielded an additive reduction in the growth of MDA-MB-231 tumor xenografts. These findings support a role of NOS2/COX2 crosstalk during disease progression of aggressive cancer phenotypes and offer insight into therapeutic applications for better survival of patients with ER⁻ and TNBC disease.
Recent findings suggest that co‐expression of NOS2 and COX2 is a strong prognostic indicator in triple‐negative breast cancer patients. These two key inflammation‐associated enzymes are responsible ...for the biosynthesis of NO and PGE2, respectively, and can exert their effect in both an autocrine and paracrine manner. Impairment of their physiological regulation leads to critical changes in both intra‐tumoural and intercellular communication with the immune system and their adaptation to the hypoxic tumour micro‐environment. Recent studies have also established a key role of NOS2–COX2 in causing metabolic shift. This review provides an extensive overview of the role of NO and PGE2 in shaping communication between the tumour micro‐environment composed of tumour and immune cells that in turn favours tumour progression and metastasis.
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This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc
An anion‐binding approach to the problem of preparing enantioenriched γ‐lactams from enolisable anhydrides and imines is reported. A simple bisurea catalyst promotes the cycloaddition between α‐aryl ...succinic anhydrides and either PMP‐ or benzhydryl‐protected aldimines to provide γ‐lactams with two contiguous stereocentres (one quaternary) with complete diastereocontrol and high to excellent enantioselectivity for the first time. A DFT study has provided insight into the catalyst mode of action and the origins of the observed stereocontrol.
The scope of the asymmetric cycloaddition between simple imines and anhydrides has been expanded to include highly enantioselective synthesis of γ‐lactams for the first time.
A strong correlation between NOS2 and COX2 tumor expression and poor clinical outcomes in ER breast cancer has been established. However, the mechanisms of tumor induction of these enzymes are ...unclear. Analysis of The Cancer Genome Atlas (TCGA) revealed correlations between NOS2 and COX2 expression and Th1 cytokines. Herein, single-cell RNAseq analysis of TNBC cells shows potent NOS2 and COX2 induction by IFNγ combined with IL1β or TNFα. Given that IFNγ is secreted by cytolytic lymphocytes, which improve clinical outcomes, this role of IFNγ presents a dichotomy. To explore this conundrum, tumor NOS2, COX2, and CD8
T cells were spatially analyzed in aggressive ER-, TNBC, and HER2 + breast tumors. High expression and clustering of NOS2-expressing tumor cells occurred at the tumor/stroma interface in the presence of stroma-restricted CD8
T cells. High expression and clustering of COX2-expressing tumor cells extended into immune desert regions in the tumor core where CD8
T cell penetration was limited or absent. Moreover, high NOS2-expressing tumor cells were proximal to areas with increased satellitosis, suggestive of cell clusters with a higher metastatic potential. Further in vitro experiments revealed that IFNγ + IL1β/TNFα increased the elongation and migration of treated tumor cells. This spatial analysis of the tumor microenvironment provides important insight into distinct neighborhoods where stroma-restricted CD8
T cells exist proximal to NOS2-expressing tumor niches that could have increased metastatic potential.
Genomes are nonrandomly organized within the three-dimensional space of the cell nucleus. Here, we have identified several genes whose nuclear positions are altered in human invasive breast cancer ...compared with normal breast tissue. The changes in positioning are gene specific and are not a reflection of genomic instability within the cancer tissue. Repositioning events are specific to cancer and do not generally occur in noncancerous breast disease. Moreover, we show that the spatial positions of genes are highly consistent between individuals. Our data indicate that cancer cells have disease-specific gene distributions. These interphase gene positioning patterns may be used to identify cancer tissues.
Split-protein systems, an approach that relies on fragmentation of proteins with their further conditional re-association to form functional complexes, are increasingly used for various biomedical ...applications. This approach offers tight control of protein functions and improved detection sensitivity. Here we report a similar technique based on a pair of RNA-DNA hybrids that can be used generally for triggering different split functionalities. Individually, each hybrid is inactive but when two cognate hybrids re-associate, different functionalities are triggered inside mammalian cells. As a proof of concept, this work mainly focuses on the activation of RNA interference. However, the release of other functionalities (such as resonance energy transfer and RNA aptamer) is also shown. Furthermore, in vivo studies demonstrate a significant uptake of the hybrids by tumours together with specific gene silencing. This split-functionality approach presents a new route in the development of 'smart' nucleic acid-based nanoparticles and switches for various biomedical applications.
The metabolic requirements and functions of cancer and normal tissues are vastly different. Due to the rapid growth of cancer cells in the tumor microenvironment, distorted vasculature is commonly ...observed, which creates harsh environments that require rigorous and constantly evolving cellular adaption. A common hallmark of aggressive and therapeutically resistant tumors is hypoxia and hypoxia-induced stress markers. However, recent studies have identified alterations in a wide spectrum of metabolic pathways that dictate tumor behavior and response to therapy. Accordingly, it is becoming clear that metabolic processes are not uniform throughout the tumor microenvironment. Metabolic processes differ and are cell type specific where various factors promote metabolic heterogeneity within the tumor microenvironment. Furthermore, within the tumor, these metabolically distinct cell types can organize to form cellular neighborhoods that serve to establish a pro-tumor milieu in which distant and spatially distinct cellular neighborhoods can communicate via signaling metabolites from stroma, immune and tumor cells. In this review, we will discuss how biochemical interactions of various metabolic pathways influence cancer and immune microenvironments, as well as associated mechanisms that lead to good or poor clinical outcomes.
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