Rahul Bhome

RANTES release by human adipose tissue in vivo and evidence for depot-specific differences

Obesity is associated with elevated inflammatory signals from various adipose tissue depots. This study aimed to evaluate release of regulated on activation, normal T cell expressed and secreted (RANTES) by human adipose tissue in vivo and ex vivo, in reference to monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) release. Arteriovenous differences of RANTES, MCP-1, and IL-6 were studied in vivo across the abdominal subcutaneous adipose tissue in healthy Caucasian subjects with a wide range of adiposity. Systemic levels and ex vivo RANTES release were studied in abdominal subcutaneous, gastric fat pad, and omental adipose tissue from morbidly obese bariatric surgery patients and in thoracic subcutaneous and epicardial adipose tissue from cardiac surgery patients without coronary artery disease. Arteriovenous studies confirmed in vivo RANTES and IL-6 release in adipose tissue of lean and obese subjects and release of MCP-1 in obesity. However, in vivo release of MCP-1 and RANTES, but not IL-6, was lower than circulating levels. Ex vivo release of RANTES was greater from the gastric fat pad compared with omental (P = 0.01) and subcutaneous (P = 0.001) tissue. Epicardial adipose tissue released less RANTES than thoracic subcutaneous adipose tissue in lean (P = 0.04) but not obese subjects. Indexes of obesity correlated with epicardial RANTES but not with systemic RANTES or its release from other depots. In conclusion, RANTES is released by human subcutaneous adipose tissue in vivo and in varying amounts by other depots ex vivo. While it appears unlikely that the adipose organ contributes significantly to circulating levels, local implications of this chemokine deserve further investigation.

A top-down view of the tumor microenvironment: structure, cells and signaling

It is well established that the tumor microenvironment (TME) contributes to cancer progression. Stromal cells can be divided into mesenchymal, vascular, and immune. Signaling molecules secreted by the tumor corrupts these cells to create “activated” stroma. Equally, the extracellular matrix (ECM) contributes to tumor development and invasion by forming a biologically active scaffold. In this review we describe the key structural, cellular and signaling components of the TME with a perspective on stromal soluble factors and microRNAs (miRNAs).

Low-dose acetylsalicylic acid inhibits the secretion of interleukin-6 from white adipose tissue

Background:Chronically elevated interleukin-6 (IL-6) is implicated in obesity-associated pathologies, where a proportion of this cytokine is derived from adipose tissue. Proinflammatory prostaglandins, which regulate this cytokine elsewhere, are also produced by this tissue.Objective:To investigate whether constitutively active cyclooxygenase (COX)/prostaglandin (PG) pathway in white adipose tissue (WAT) is responsible for basal IL-6 production.Design:The effect of acetylsalicylic acid (ASA), an inhibitor of COX, on IL-6 was assessed in human subjects and mice. COX, downstream PG synthase (PGS) activity and PG receptor signalling were determined in subcutaneous (SC), gonadal (GN) WAT and adipocytes.Methods and Results:In obese humans, low-dose ASA (150 mg day−1 for 10 days) inhibited systemic IL-6 and reduced IL-6 release from SC WAT ex vivo (0.2 mM). Similarly, in mice, ASA (0.2 and 2.0 mg kg−1) suppressed SC WAT 6-keto-PGF1α (a stable metabolite of prostacyclin) and IL-6 release. Although both COX isoforms are comparably expressed, prostacyclin synthase expression is higher in GN WAT, with levels of activity correlating directly with IL-6. Both ASA (5 mM) and NS-398 (COX-2 selective inhibitor ⩽1 μM), but not SC-560 (COX-1 selective inhibitor ⩽1 μM), attenuated IL-6 release from murine WAT in vitro and abolished its depot differences. Prostacyclin receptor (IP) and, to a lesser extent, PGE2 (EP2 and EP4) receptor agonists elevated the release of IL-6 from adipocytes.Conclusions:In adipose tissue, constitutive COX-2-coupled prostacyclin triggers the release of basal IL-6, which in obese subjects is significantly dampened by ASA ingestion, thus offering a novel, modifiable pathway to regulate the potentially pathological component of this cytokine.

Translational aspects in targeting the stromal tumour microenvironment: From bench to bedside

Solid tumours comprise, not only malignant cells but also a variety of stromal cells and extracellular matrix proteins. These components interact via an array of signalling pathways to create an adaptable network that may act to promote or suppress cancer progression. To date, the majority of anti-tumour chemotherapeutic agents have principally sought to target the cancer cell. Consequently, resistance develops because of clonal evolution, as a result of selection pressure during tumour expansion. The concept of activating or inhibiting other cell types within the tumour microenvironment is relatively novel and has the advantage of targeting cells which are genetically stable and less likely to develop resistance. This review outlines key players in the stromal tumour microenvironment and discusses potential targeting strategies that may offer therapeutic benefit. Focal points: • Benchside ○ The tumour stroma consists of mesenchymal, immune and vascular cells housed in an extracellular matrix. Stromal cells and extracellular matrix proteins represent genetically stable targets which can be exploited in cancer treatment. Numerous in vitro and animal studies support the concept of stromal-directed treatment.• Bedside ○ Several therapeutic strategies have been developed or repurposed to target the stroma. The anti-angiogenic agent bevacizumab was one of the first specific stromal-targeting agents to be licensed for cancer treatment over a decade ago. More recently, immune modulation of the stroma has become a hugely successful strategy, with novel drugs such as checkpoint inhibitors set to revolutionise cancer treatment.• Governments ○ Funding bodies should continue to acknowledge the pivotal role that the stroma plays in cancer progression, in parallel with cancer cell itself. Undoubtedly, the most successful treatment regimens of the future will address both the “seed” and the “soil”.

Exosomal microRNAs (exomiRs): Small molecules with a big role in cancer

Exosomes are secreted vesicles which can transmit molecular cargo between cells. Exosomal microRNAs (exomiRs) have drawn much attention in recent years because there is increasing evidence to suggest that loading of microRNAs into exosomes is not a random process. Preclinical studies have identified functional roles for exomiRs in influencing many hallmarks of cancer. Mechanisms underpinning their actions, such as exomiR receptors (“miRceptors”), are now becoming apparent. Even more exciting is the fact that exomiRs are highly suitable candidates for use as non-invasive biomarkers in an era of personalized cancer medicine.

Profiling the MicroRNA Payload of Exosomes Derived from Ex Vivo Primary Colorectal Fibroblasts

The tumor microenvironment is a heterogeneous and dynamic network that exists between cancer and stroma, playing a critical role in cancer progression. Certain tumorigenic signals such as microRNAs are derived from the stroma and conveyed to cancer cells (and vice versa) in nanoparticles called exosomes. Their identification and characterization is an important step in better understanding cellular cross talk and its consequences. To this end we describe how to culture primary ex vivo derived fibroblasts from colorectal tissue, isolate their exosomes, extract exosomal RNA and perform microRNA profiling.

Exosomal microRNAs derived from colorectal cancer-associated fibroblasts: role in driving cancer progression

Colorectal cancer is a global disease with increasing incidence. Mortality is largely attributed to metastatic spread and therefore, a mechanistic dissection of the signals which influence tumor progression is needed. Cancer stroma plays a critical role in tumor proliferation, invasion and chemoresistance. Here, we sought to identify and characterize exosomal microRNAs as mediators of stromal-tumor signaling. In vitro, we demonstrated that fibroblast exosomes are transferred to colorectal cancer cells, with a resultant increase in cellular microRNA levels, impacting proliferation and chemoresistance. To probe this further, exosomal microRNAs were profiled from paired patient-derived normal and cancer-associated fibroblasts, from an ongoing prospective biomarker study. An exosomal cancer-associated fibroblast signature consisting of microRNAs 329, 181a, 199b, 382, 215 and 21 was identified. Of these, miR-21 had highest abundance and was enriched in exosomes. Orthotopic xenografts established with miR-21-overexpressing fibroblasts and CRC cells led to increased liver metastases compared to those established with control fibroblasts. Our data provide a novel stromal exosome signature in colorectal cancer, which has potential for biomarker validation. Furthermore, we confirmed the importance of stromal miR-21 in colorectal cancer progression using an orthotopic model, and propose that exosomes are a vehicle for miR-21 transfer between stromal fibroblasts and cancer cells.

The Colorectal Cancer Microenvironment: Strategies for Studying the Role of Cancer-Associated Fibroblasts

Colorectal cancer (CRC) is a key public health concern and the second highest cause of cancer related death in Western society. A dynamic interaction exists between CRC cells and the surrounding tumor microenvironment, which can stimulate not only the development of CRC, but its progression and metastasis, as well as the development of resistance to therapy. In this chapter, we focus on the role of fibroblasts within the CRC tumor microenvironment and describe some of the key methods for their study, as well as the evaluation of dynamic interactions within this biological ecosystem.

Clinical relevance, prognostic potential, and therapeutic strategies of noncoding RNAs in cancer

Noncoding RNAs (ncRNAs) are master regulators of the genome, controlling the most fundamental of cellular processes. Several hundred studies have demonstrated their dysregulation across a range of cancer types, and translational follow-on studies have led to the development of putative ncRNA biomarkers for identification and staging of cancer. Additionally, mechanistic studies have clearly identified key functions for ncRNAs in cancer progression, and highlighted actionable pathways to be targeted by ncRNA-directed therapies. Consequently, ncRNA-derived therapeutics is now entering later stage clinical trials. In this chapter, we describe the classification of ncRNAs, their biology, and their potential clinical applications.

Long non-coding RNAs within the tumour microenvironment and their role in tumour-stroma cross-talk

Long non-coding RNAs (lncRNAs) are a diverse class of RNA transcripts which have limited protein coding potential. They perform a variety of cellular functions in health, but have also been implicated during malignant transformation. A further theme in recent years is the critical role of the tumour microenvironment and the dynamic interactions between cancer and stromal cells in promoting invasion and disease progression. Whereas the contribution of deregulated lncRNAs within cancer cells has received considerable attention, their significance within the tumour microenvironment is less well understood. The tumour microenvironment consists of cancer-associated stromal cells and structural extracellular components which interact with one another and with the transformed epithelium via complex extracellular signalling pathways. LncRNAs are directly and indirectly involved in tumour/stroma cross-talk and help stimulate a permissive tumour microenvironment which is more conducive for invasive tumour growth. Furthermore, lncRNAs play key roles in determining the phenotype of cancer associated stromal cells and contribute to angiogenesis and immune evasion pathways, extracellular-matrix (ECM) turnover and the response to hypoxic stress. Here we explore the multifaceted roles of lncRNAs within the tumour microenvironment and their putative pathophysiological effects.