Inside anticancer therapy resistance and metastasis. Focus on CD36.

Despite recent advances in targeted cancer therapies, drug resistance remains an important setback in tumor control. Understanding the complex mechanisms involved in both innate and acquired drug resistance represents the first step in discovering novel therapeutic agents. Because of its importance in tumorigenesis, progression, and metastasis, lipid metabolism is increasingly garnering attention. CD36 is a membrane receptor at the top of the signaling cascade that transports lipids. Its expression has been repeatedly presented as an unfavorable prognostic factor for various tumor types, raising the question: could CD36 be a critical factor in cancer treatment resistance? In our review, we set out to explore the most prominent studies on the implication of CD36 in resistance to platinum-based drugs and other adjuvant cancer therapies in solid and haematological neoplasia. Moreover, we provide an overview of the latest anti-CD36 cancer therapies, thus opening new perspectives for future personalized medicine.

Dermal Telocytes: A Different Viewpoint of Skin Repairing and Regeneration.

Fifteen years after their discovery, telocytes (TCs) are yet perceived as a new stromal cell type. Their presence was initially documented peri-digestively, and gradually throughout the interstitia of many (non-)cavitary mammalian, human, and avian organs, including skin. Each time, TCs proved to be involved in diverse spatial relations with elements of interstitial (ultra)structure (blood vessels, nerves, immune cells, etc.). To date, transmission electron microscopy (TEM) remained the single main microscopic technique able to correctly and certainly attest TCs by their well-acknowledged (ultra)structure. In skin, dermal TCs reiterate almost all (ultra)structural features ascribed to TCs in other locations, with apparent direct implications in skin physiology and/or pathology. TCs' uneven distribution within skin, mainly located in stem cell niches, suggests involvement in either skin homeostasis or dermatological pathologies. On the other hand, different skin diseases involve different patterns of disruption of TCs' structure and ultrastructure. TCs' cellular cooperation with other interstitial elements, their immunological profile, and their changes during remission of diseases suggest their role(s) in tissue regeneration/repair processes. Thus, expanding the knowledge on dermal TCs could offer new insights into the natural skin capacity of self-repairing. Moreover, it would become attractive to consider that augmenting dermal TCs' presence/density could become an attractive therapeutic alternative for treating various skin defects.

Low-Concentrations of Fatty Acids Induce an Early Increase in IL-8 Levels in Normal Human Astrocytes.

Fatty acids (FAs) have been shown to exhibit a pro-inflammatory response in various cell types, but astrocytes have been mostly overlooked. FAs, both saturated and unsaturated, have previously been shown to induce pro-inflammatory responses in astrocytes at high concentrations of hundreds of µg/mL. SSO (Sulfo-N-succinimidyl Oleate sodium), an inhibitor of FA translocase CD36, has been shown to prevent inflammation in the mouse brain by acting on local microglia and infiltrating monocytes. Our hypothesis was that SSO treatment would also impact astrocyte pro-inflammatory response to FA. In order to verify our assumption, we evaluated the expression of pro- and anti-inflammatory cytokines in normal human astrocyte cell culture pre-treated (or not) with SSO, and then exposed to low concentrations of both saturated (palmitic acid) and unsaturated (oleic acid) FAs. As a positive control for astrocyte inflammation, we used fibrillary amyloid. Neither Aß 1-42 nor FAs induced CD36 protein expression in human astrocytes in cell culture At low concentrations, both types of FAs induced IL-8 protein secretion, and this effect was specifically inhibited by SSO pre-treatment. In conclusion, low concentrations of oleic acid are able to induce an early increase in IL-8 expression in normal human astrocytes, which is specifically downregulated by SSO.

A Fatty Acid Fraction Purified From Sea Buckthorn Seed Oil Has Regenerative Properties on Normal Skin Cells.

In recent years, natural product's research gained momentum, fueled by technological advancement and open availability of research data. To date, sea buckthorn (Hippophae rhamnoides L. [Elaeagnaceae]) plant parts, especially berries, are well characterized and repeatedly tested for antioxidant activity and regenerative properties, in various cell types and tissues. However, fatty acids (FA) have been less investigated in term of biological effects, although, they are important bioactive components of the sea buckthorn fruit and oil. The aim of our work was to determine whether sea buckthorn seed oil is a suitable source of FA with regenerative properties on normal skin cells. Using high-performance liquid chromatography (HPLC) and liquid chromatography - mass spectrometry (LC-MS), we purified and characterized four fractions enriched in saturated (palmitic) and non-saturated (linoleic, alfa-linolenic, oleic) FA, which were tested for cytotoxicity, cytokine and growth factor production, and regenerative effect on normal keratinocytes and skin fibroblasts. Evidence is presented that the palmitic acid enriched fraction was a suitable sea buckthorn seed oil derived product with cell proliferation properties on both skin cell types.

Sea-Buckthorn Seed Oil Induces Proliferation of both Normal and Dysplastic Keratinocytes in Basal Conditions and under UVA Irradiation.

Past decades demonstrate an increasing interest in herbal remedies in the public eye, with as many as 80% of people worldwide using these remedies as healthcare products, including those for skin health. Sea buckthorn and its derived products (oil; alcoholic extracts), rich in flavonoids and essential fatty acids, are among these healthcare products. Specifically, sea buckthorn and its derivatives are reported to have antioxidant and antitumor activity in dysplastic skin cells. On the other hand, evidence suggests that the alteration of lipid metabolism is related to increased malignant behavior. Given the paradoxical involvement of lipids in health and disease, we investigated how sea-buckthorn seed oil, rich in long-chain fatty acids, modifies the proliferation of normal and dysplastic skin cells in basal conditions, as well as under ultraviolet A (UVA) radiation. Using real-time analysis of normal and dysplastic human keratinocytes, we showed that sea-buckthorn seed oil stimulated the proliferation of dysplastic cells, while it also impaired the ability of both normal and dysplastic cells to migrate over a denuded area. Furthermore, UVA exposure increased the expression of CD36/SR-B2, a long-chain fatty acid translocator that is related to the metastatic behavior of tumor cells.

Caveolae as Potential Hijackable Gates in Cell Communication.

Caveolae are membrane microdomains described in many cell types involved in endocytocis, transcytosis, cell signaling, mechanotransduction, and aging. They are found at the interface with the extracellular environment and are structured by caveolin and cavin proteins. Caveolae and caveolins mediate transduction of chemical messages via signaling pathways, as well as non-chemical messages, such as stretching or shear stress. Various pathogens or signals can hijack these gates, leading to infectious, oncogenic and even caveolin-related diseases named caveolinopathies. By contrast, preclinical and clinical research have fallen behind in their attempts to hijack caveolae and caveolins for therapeutic purposes. Caveolae involvement in human disease is not yet fully explored or understood and, of all their scaffold proteins, only caveolin-1 is being considered in clinical trials as a possible biomarker of disease. This review briefly summarizes current knowledge about caveolae cell signaling and raises the hypothesis whether these microdomains could serve as hijackable "gatekeepers" or "gateways" in cell communication. Furthermore, because cell signaling is one of the most dynamic domains in translating data from basic to clinical research, we pay special attention to translation of caveolae, caveolin, and cavin research into clinical practice.

Gene expression profile of adhesion and extracellular matrix molecules during early stages of skeletal muscle regeneration.

Skeletal muscle regeneration implies the coordination of myogenesis with the recruitment of myeloid cells and extracellular matrix (ECM) remodelling. Currently, there are no specific biomarkers to diagnose the severity and prognosis of muscle lesions. In order to investigate the gene expression profile of extracellular matrix and adhesion molecules, as premises of homo- or heterocellular cooperation and milestones for skeletal muscle regeneration, we performed a gene expression analysis for genes involved in cellular cooperation, migration and ECM remodelling in a mouse model of acute crush injury. The results obtained at two early time-points post-injury were compared to a GSE5413 data set from two other trauma models. Third day post-injury, when inflammatory cells invaded, genes associated with cell-matrix interactions and migration were up-regulated. After day 5, as myoblast migration and differentiation started, genes for basement membrane constituents were found down-regulated, whereas genes for ECM molecules, macrophage, myoblast adhesion, and migration receptors were up-regulated. However, the profile and the induction time varied according to the experimental model, with only few genes being constantly up-regulated. Gene up-regulation was higher, delayed and more diverse following more severe trauma. Moreover, one of the most up-regulated genes was periostin, suggestive for severe muscle damage and unfavourable architecture restoration.

Caveolin-1-Knockout Mouse as a Model of Inflammatory Diseases.

Caveolin-1 (CAV1) is the scaffold protein of caveolae, which are minute invaginations of the cell membrane that are involved in endocytosis, cell signaling, and endothelial-mediated inflammation. CAV1 has also been reported to have a dual role as either a tumor suppressor or tumor promoter, depending on the type of cancer. Inflammation is an important player in tumor progression, but the role of caveolin-1 in generating an inflammatory milieu remains poorly characterized. We used a caveolin-1-knockout (CAV1-/-) mouse model to assess the inflammatory status via the quantification of the pro- and anti-inflammatory cytokine levels, as well as the ability of circulating lymphocytes to respond to nonspecific stimuli by producing cytokines. Here, we report that the CAV1-/- mice were characterized by a low-grade systemic proinflammatory status, with a moderate increase in the IL-6, TNF-α, and IL-12p70 levels. CAV1-/- circulating lymphocytes were more prone to cytokine production upon nonspecific stimulation than the wild-type lymphocytes. These results show that CAV1 involvement in cell homeostasis is more complex than previously revealed, as it plays a role in the inflammatory process. These findings indicate that the CAV1-/- mouse model could prove to be a useful tool for inflammation-related studies.

Emerging Therapeutic Targets in Oncologic Photodynamic Therapy.

BACKGROUND: Reactive oxygen species sustain tumorigenesis and cancer progression through deregulated redox signalling which also sensitizes cancer cells to therapy. Photodynamic therapy (PDT) is a promising anti-cancer therapy based on a provoked singlet oxygen burst, exhibiting a better toxicological profile than chemo- and radiotherapy. Important gaps in the knowledge on underlining molecular mechanisms impede on its translation towards clinical applications. AIMS AND METHODS: The main objective of this review is to critically analyse the knowledge lately gained on therapeutic targets related to redox and inflammatory networks underlining PDT and its outcome in terms of cell death and resistance to therapy. Emerging therapeutic targets and pharmaceutical tools will be documented based on the identified molecular background of PDT. RESULTS: Cellular responses and molecular networks in cancer cells exposed to the PDT-triggered singlet oxygen burst and the associated stresses are analysed using a systems medicine approach, addressing both cell death and repair mechanisms. In the context of immunogenic cell death, therapeutic tools for boosting anti-tumor immunity will be outlined. Finally, the transcription factor NRF2, which is a major coordinator of cytoprotective responses, is presented as a promising pharmacologic target for developing co-therapies designed to increase PDT efficacy. CONCLUSION: There is an urgent need to perform in-depth molecular investigations in the field of PDT and to correlate them with clinical data through a systems medicine approach for highlighting the complex biological signature of PDT. This will definitely guide translation of PDT to clinic and the development of new therapeutic strategies aimed at improving PDT.

Telocytes and putative stem cells in the lungs: electron microscopy, electron tomography and laser scanning microscopy.

This study describes a novel type of interstitial (stromal) cell - telocytes (TCs) - in the human and mouse respiratory tree (terminal and respiratory bronchioles, as well as alveolar ducts). TCs have recently been described in pleura, epicardium, myocardium, endocardium, intestine, uterus, pancreas, mammary gland, etc. (see www.telocytes.com ). TCs are cells with specific prolongations called telopodes (Tp), frequently two to three per cell. Tp are very long prolongations (tens up to hundreds of µm) built of alternating thin segments known as podomers (≤ 200 nm, below the resolving power of light microscope) and dilated segments called podoms, which accommodate mitochondria, rough endoplasmic reticulum and caveolae. Tp ramify dichotomously, making a 3-dimensional network with complex homo- and heterocellular junctions. Confocal microscopy reveals that TCs are c-kit- and CD34-positive. Tp release shed vesicles or exosomes, sending macromolecular signals to neighboring cells and eventually modifying their transcriptional activity. At bronchoalveolar junctions, TCs have been observed in close association with putative stem cells (SCs) in the subepithelial stroma. SCs are recognized by their ultrastructure and Sca-1 positivity. Tp surround SCs, forming complex TC-SC niches (TC-SCNs). Electron tomography allows the identification of bridging nanostructures, which connect Tp with SCs. In conclusion, this study shows the presence of TCs in lungs and identifies a TC-SC tandem in subepithelial niches of the bronchiolar tree. In TC-SCNs, the synergy of TCs and SCs may be based on nanocontacts and shed vesicles.

Telocytes in pleura: two- and three-dimensional imaging by transmission electron microscopy.

Information about the ultrastructure of connective (interstitial) cells supporting the pleural mesothelium is scarce. Our aim has been to examine whether telocytes (TCs) are present in pleura, as in epicardium and mesentery. TCs are a distinct type of cell, characterized by specific prolongations named telopodes (Tp). We have used transmission electron microscopy (TEM) and electron tomography (ET) to determine whether ultrastructural diagnostic criteria accepted for TCs are fulfilled by any of the cell subpopulations existing in the sub-mesothelial layer in mouse and human pleura. TCs have been identified with TEM by their characteristic prolongations. Tp appear long and moniliform, because of the alternation of podomeres (thin segments of less than 0.2 µm) and podoms (small dilations accommodating caveolae, mitochondria, and endoplasmic reticulum). Tp ramifications follow a dichotomic pattern and establish specialized cell-to-cell junctional complexes. TCs, via their Tp, seem to form an interstitial network beneath the mesothelium, covering about two-thirds of the abluminal mesothelial layer. ET has revealed complex junctional structures and tight junctions connecting pleural TCs, and small vesicles at this level in Tp. Thus, pleural TCs share significant similarities with TCs described in other serosae. Whether TCs are a (major) player in mesothelial-cell-induced tissue repair remains to be established. Nevertheless, the extremely long thin Tp and complex junctional structures that they form and the release of vesicles (or exosomes) indicate the participation of TCs in long-distance homo- or heterocellular communication.

Telocytes in human term placenta: morphology and phenotype.

In the last few years, a new cell type - interstitial Cajal-like cell (ICLC) - has been described in digestive and extra-digestive organs. The name has recently been changed to telocytes (TC) and their typical thin, long processes have been named telopodes (TP). To support the hypothesis that TC may also be present in human placenta and add to the information already available, we provide evidence on the ultrastructure, immunophenotype, distribution, and interactions with the surrounding stromal cells of TC in the villous core of human term placenta. We used phase-contrast microscopy, light microscopy of semithin sections, transmission electron microscopy, immunohistochemistry, and immunofluorescence of tissue sections or cell cultures, following a pre-established diagnostic algorithm. Transmission electron microscopy showed cells resembling TC, most (∼76%) having 2-3 very thin, longprocesses (tens to hundreds of micrometers), with an uneven calibre(≤0.5 µm thick) and typical branching pattern. The dilations of processes accommodate caveolae, endoplasmic reticulum cisternae, and mitochondria. These TC have close contacts with perivascular SMC in stem villi. In situ, similar cells are positive for c-kit, CD34, vimentin, caveolin-1, vascular endothelial growth factor (VEGF), and inducible nitric oxide synathase (iNOS). The c-kit-positive cells inconsistently co-express CD34, CD44, αSMA, S100, neuron-specific enolase, and nestin. Among cells with a morphologic TC profile in cell cultures, about 13% co-express c-kit, vimentin, and caveolin-1; 70% of the c-kit-positive cells co-express CD34 and 12% co-express iNOS or VEGF. In conclusion, this study confirms the presence of TC in human term placenta and provides their ultrastructural and immunophenotypic characterization.

Mesenchymal stem cells and cardiac repair.

Accumulating clinical and experimental evidence indicates that mesenchymal stem cells (MSCs) are promising cell types in the treatment of cardiac dysfunction. They may trigger production of reparative growth factors, replace damaged cells and create an environment that favours endogenous cardiac repair. However, identifying mechanisms which regulate the role of MSCs in cardiac repair is still at work. To achieve the maximal clinical benefits, ex vivo manipulation can further enhance MSC therapeutic potential. This review focuses on the mechanism of MSCs in cardiac repair, with emphasis on ex vivo manipulation.

Interstitial Cajal-like cells in human gallbladder.

We describe here an interstitial Cajal-like cell type (ICLC) in human gallbladder, resembling the archetypal enteric interstitial cells of Cajal. Gallbladder ICLC were demonstrated in fresh preparations (tissue cryosections) using methylene-blue, and fixed specimens in Epon semi-thin sections stained with toluidine blue or transmission electron microscopy (TEM). The positive diagnosis of gallbladder ICLC was further verified by immunohistochemistry: CD117/c-kit, CD34, and another 16 antigens: vimentin, desmin, nestin, alpha-smooth muscle actin, NK-1, S-100, PGP-9.5, tau protein, chromogranin A, NSE, GFAP, CD1a, CD62-P, CD68, estrogen and progesterone receptors. Double immunostaining was performed for CD117, CD34 and CD117 and nestin, respectively. In fresh specimens, the spatial density of gallbladder ICLC was 100-110 cells/mm(2). ICLC mainly appeared beneath the epithelium and in muscularis (about 7%, and approximately 5%, respectively). In toto, ICLC represent in gallbladder approximately 5.5% of subepithelial cells. TEM showed that diagnostic criteria were fulfilled by ICLC. Moreover, TEM indicated that the main ultrastructural distinctive feature for ICLC, the cell processes, develop into the characteristic shape at a relatively early stage of development. It remains to be established if, in humans, ICLC are involved in gallbladder (dis)functions (e.g. pace-making, secretion (auto-, juxta- and/or paracrine), intercellular signaling, or stone formation).