Megha Suresh

Bio: Megha Suresh is an academic researcher from Northeastern University. The author has contributed to research in topics: Tumor microenvironment & Cancer cell. The author has an hindex of 2, co-authored 3 publications receiving 387 citations.

Reversing epigenetic mechanisms of drug resistance in solid tumors using targeted microRNA delivery.

Abstract: Introduction: Tumor cells utilize many different mechanisms to desensitize themselves to the cytotoxic effects of drugs, but it has recently been recognized that alterations in epigenetic control of gene expression underly many of them. As master regulators of gene expression, microRNAs (miRNAs) present a promising therapeutic strategy for the reversal of epigenetic changes that lead to drug resistance phenotypes in tumor cells.Areas covered: Effects of epigenetic changes on drug resistance in a variety of solid tumors are discussed. Specific miRNAs that are involved with the regulation of epigenetic machinery are highlighted. Further, we consider how delivery of miRNA or antagomirs may be utilized to resensitize drug-resistant tumor cells.Expert opinion: Reversal of epigenetically controlled tumor drug resistance mechanisms via miRNA delivery presents a novel strategy for enhancing the efficacy of chemotherapeutics. Further, the ability to target delivery of miRNAs may provide the opportunity to ...

In vitro model of inflammatory, hypoxia, and cancer stem cell signaling in pancreatic cancer using heterocellular 3-dimensional spheroids

Abstract: Introduction As one of the most aggressive cancers worldwide, pancreatic cancer is associated with an extremely poor prognosis. The pancreatic tumor microenvironment consists of cancer cells and other tumor associated cells. Cross-talk between these different cell types through various signaling molecules results in the development of a more aggressive and malignant phenotype. Additionally, due to the highly dysregulated vasculature of tumors, the inner tumor core becomes hypoxic and eventually necrotic. Therefore, there is a need for the development of a physiologically relevant in vitro model that recapitulates these dynamic cell-cell interactions and the 3-dimensional (3D) structure of pancreatic tumors. Methods Four different 3D co-culture spheroid models using different combinations of Panc-1 tumor cells, J774.A1 macrophages, and NIH-3T3 fibroblast cell lines were reproducibly developed using the hanging drop technique in order to mimic the tumor microenvironment and to evaluate the differences in expression of various inflammatory, hypoxia, and cancer stem cell markers, including IL-8, TNF-α, TGF-β, HIF-1α HIF-2α, SCF, and LDH-A. Additionally, immunofluorescence studies were employed to investigate whether these spheroids tested positive for a cancer stem cell population. Results Pronounced differences in morphology as well as expression of signalling markers were observed using qPCR, indicative of strong influences of co-culturing different cell lines. These models also tested positive for cancer stem cell (CSCs) markers based on immunofluorescence and qPCR analysis. Conclusion Our results demonstrate the potential of 3D co-culture spheroid models to capture the inflammatory and hypoxic markers of pancreatic tumor microenvironment. We further demonstrate the presence of cancer cells with stem cell markers, similar to actual pancreatic cancer tumor. These spheroids present excellent in vitro system to study tumor-immune-stromal cell interactions as well as test deliverability of potential therapeutics in the tumor microenvironment with accurate physical and physiological barriers.

A regulatory role for the unstructured C-terminal domain of the CtBP transcriptional corepressor

Abstract: The C-terminal Binding Protein (CtBP) is a transcriptional corepressor that plays critical roles in development, tumorigenesis, and cell fate. CtBP proteins are structurally similar to alpha hydroxyacid dehydrogenases and additionally feature an unstructured C-terminal domain (CTD). The role of a possible dehydrogenase activity has been postulated for the corepressor, although in vivo substrates are unknown, but the functional significance of the CTD is unclear. In the mammalian system, CtBP proteins lacking the CTD are able to function as transcriptional regulators and oligomerize, putting into question the significance of the CTD for gene regulation. Yet, the presence of an unstructured CTD of ∼100 residues, including some short motifs, is conserved across Bilateria, indicating the importance of this domain. To study the in vivo functional significance of the CTD, we turned to the Drosophila melanogaster system, which naturally expresses isoforms with the CTD (CtBP(L)), and isoforms lacking the CTD (CtBP(S)). We used the CRISPRi system to test dCas9-CtBP(S) and dCas9-CtBP(L) on diverse endogenous genes, to directly compare their transcriptional impacts in vivo. Interestingly, CtBP(S) was able to significantly repress transcription of the E2F2 and Mpp6 genes, while CtBP(L) had minimal impact, suggesting that the long CTD modulates CtBP’s repression activity. In contrast, in cell culture, the isoforms behaved similarly on a transfected Mpp6 reporter. Thus, we have identified context-specific effects of these two developmentally-regulated isoforms, and propose that differential expression of CtBP(S) and CtBP(L) may provide a spectrum of repression activity suitable for developmental programs.

Progress in Exosome Isolation Techniques.

Abstract: Exosomes are one type of membrane vesicles secreted into extracellular space by most types of cells. In addition to performing many biological functions particularly in cell-cell communication, cumulative evidence has suggested that several biological entities in exosomes like proteins and microRNAs are closely associated with the pathogenesis of most human malignancies and they may serve as invaluable biomarkers for disease diagnosis, prognosis, and therapy. This provides a commanding impetus and growing demands for simple, efficient, and affordable techniques to isolate exosomes. Capitalizing on the physicochemical and biochemical properties of exosomes, a number of techniques have been developed for the isolation of exosomes. This article summarizes the advances in exosome isolation techniques with an emphasis on their isolation mechanism, performance, challenges, and prospects. We hope that this article will provide an overview of exosome isolation techniques, opening up new perspectives towards the development more innovative strategies and devices for more time saving, cost effective, and efficient isolations of exosomes from a wide range of biological matrices.

The epigenetics of epithelial-mesenchymal plasticity in cancer

Abstract: Epithelial-mesenchymal transitions (EMTs) are a key requirement for cancer cells to metastasize and colonize in a new environment. Epithelial-mesenchymal plasticity is mediated by master transcription factors and is also subject to complex epigenetic regulation. This Review outlines our current understanding of the interactions between EMT-inducing transcription factors and epigenetic modulators during cancer progression and the therapeutic implications of exploiting this intricate regulatory process. During the course of malignant cancer progression, neoplastic cells undergo dynamic and reversible transitions between multiple phenotypic states, the extremes of which are defined by the expression of epithelial and mesenchymal phenotypes. This plasticity is enabled by underlying shifts in epigenetic regulation. A small cohort of pleiotropically acting transcription factors is widely recognized to effect these shifts by controlling the expression of a constituency of key target genes. These master regulators depend on complex epigenetic regulatory mechanisms, notably the induction of changes in the modifications of chromatin-associated histones, in order to achieve the widespread changes in gene expression observed during epithelial-mesenchymal transitions (EMTs). These associations indicate that an understanding of the functional interactions between such EMT-inducing transcription factors and the modulators of chromatin configuration will provide crucial insights into the fundamental mechanisms underlying cancer progression and may, in the longer term, generate new diagnostic and therapeutic modalities for treating high-grade malignancies.

Engineering exosomes as refined biological nanoplatforms for drug delivery.

Abstract: Exosomes, a subgroup of extracellular vesicles (EVs), have been recognized as important mediators of long distance intercellular communication and are involved in a diverse range of biological processes. Because of their ideal native structure and characteristics, exosomes are promising nanocarriers for clinical use. Exosomes are engineered at the cellular level under natural conditions, but successful exosome modification requires further exploration. The focus of this paper is to summarize passive and active loading approaches, as well as specific exosome modifications and examples of the delivery of therapeutic and imaging molecules. Examples of exosomes derived from a variety of biological origins are also provided. The biocompatible characteristics of exosomes, with suitable modifications, can increase the stability and efficacy of imaging probes and therapeutics while enhancing cellular uptake. Challenges in clinical translation of exosome-based platforms from different cell sources and the advantages of each are also reviewed and discussed.

Tumor-derived exosomal miR-1247-3p induces cancer-associated fibroblast activation to foster lung metastasis of liver cancer.

Abstract: The communication between tumor-derived elements and stroma in the metastatic niche has a critical role in facilitating cancer metastasis. Yet, the mechanisms tumor cells use to control metastatic niche formation are not fully understood. Here we report that in the lung metastatic niche, high-metastatic hepatocellular carcinoma (HCC) cells exhibit a greater capacity to convert normal fibroblasts to cancer-associated fibroblasts (CAFs) than low-metastatic HCC cells. We show high-metastatic HCC cells secrete exosomal miR-1247-3p that directly targets B4GALT3, leading to activation of β1-integrin–NF-κB signaling in fibroblasts. Activated CAFs further promote cancer progression by secreting pro-inflammatory cytokines, including IL-6 and IL-8. Clinical data show high serum exosomal miR-1247-3p levels correlate with lung metastasis in HCC patients. These results demonstrate intercellular crosstalk between tumor cells and fibroblasts is mediated by tumor-derived exosomes that control lung metastasis of HCC, providing potential targets for prevention and treatment of cancer metastasis.