Cancer, metastases and stem cells

Les chimiokines sont des protéines appartenant à la famille des cytokines. A l'origine, ces molécules ont été étudiées pour leur implication dans la régulation du trafic leucocytaire. Depuis une dizaine d'années, de nombreuses études ont cependant démontré que les chimiokines sont aussi impliquées dans les différentes étapes de la cancérogénèse : inhibition de l'immunité anti-tumorale, rôle de facteur de croissance des cellules tumorales, régulation de l'angiogénèse et particulièrement induction de la migration des métastases. En effet, les chimiokines sont capables de guider les cellules métastatiques de la tumeur primaire vers leur lieu d'implantation. Ce guidage passe par la liaison de la chimiokine à son récepteur, ce qui conduit à l'activation de différentes cascades signalétiques intracellulaires qui aboutiront in fine à la migration et le guidage des cellules le long du gradient de chimiokine, et ce jusqu'au lieu d'implantation où une tumeur secondaire pourra alors se former.C'est la compréhension du rôle des chimiokines dans la migration des métastases qui a conduit à l'étude de l'expression de leurs récepteurs dans le cancer. Après avoir étudié dans un premier temps les outils nécessaires à l'obtention de résultats fiables notamment en PCR quantitative, le profil d'expression de différents récepteurs aux chimiokines a été analysé chez des patients atteints d'un cancer colorectal. Les résultats montrent que seules les expressions des récepteurs CCR10 et CXCR4 diminuent chez les patients ayant développé des métastases. De plus cette baisse est corrélée à un mauvais pronostique. Cependant, des études in vitro démontrent que les lignées coliques métastatiques surexpriment ces récepteurs, et que la migration de celles-ci est sensible à un gradient de CCL27, le ligand du récepteur CCR10.Ces résultats a priori paradoxaux prennent tout leur sens lorsqu'on rapproche le concept métastatique du concept de cellule souche. Dans les deux cas, ces types cellulaires aux capacités phénotypiques communes (migration, survie, prolifération) peuvent donner une population cellulaire hétérogène. La mise au point d'une méthode permettant de faire passer les cellules tumorales (prolifératives) en cellules métastatiques (migratoires) et vice versa nous a conduit à un concept syncrétique dans lequel les notions de cellules tumorales, de métastases et de cellules souches se confondent. Dans celui-ci, les cellules tumorales, qu'elles soient ou non issues de cellules souches saines, sont capables de changer réversiblement de phénotype pour former des métastases (équivalent de la transition épithélio-mésenchymateuse). La notion de réversibilité est ici essentielle car elle permet d'expliquer comment une cellule métastatique, une fois implantée, peut s'activer et redonner une population cellulaire tumorale proliférative. Cela implique aussi que les métastases, capables de rester plusieurs mois en dormance, partagent les mêmes mécanismes que les cellules souches.Enfin, l'étude en parallèle de nouvelles voies de régulation de l'angiogénèse - qui fournit aux métastases le moyen de quitter la tumeur primaire - faisant intervenir le récepteur à la thrombine PAR1 d'une part et la chimiokine CXCL4, plus communément appelée PF4 d'autre part, pourrait aboutir à l'élaboration de nouvelles molécules à visée thérapeutique.Chimiokines are proteins belonging to the cytokines' family. In the beginning, chemokines were studied for their implication in the leucocytic trafic regulation. Since ten years, many studies however show that chemokines are also implied in all of carcinogenesis steps: antitumor immunity inhibition, role of growth factor of tumoral cells, angiogenesis regulation and especially metastases migration induction. Indeed, chemokines are able to guide metastatic cells from the primary tumour towards their secondary site thanks to chemokine / chemokine receptors interactions which lead to metastases migration along a chemokine gradient until their secondary site. Then, metastases activation will lead to the development of a secondary tumour.It is the understanding of chemokines' role in metastases migration that led to the study of their receptors expression in cancer. After having initially studied the tools that were necessary to obtain reliable results in particular in quantitative PCR, expression profile of several chemokine receptors was established on patients developing a colorectal cancer. Results show that only CCR10 and CXCR4 expressions significantly decrease in patients who develop metastases. Moreover this decrease is correlated with poor prognostic. However, in vitro studies show that metastatic colon cell lines overexpress the both receptors, and that migration of those cells is sensitive to a CCL27 gradient, the CCR10 ligand.These paradoxical results may however be easily explained if the metastatic concept is compared to the stem cell one. In both cases, these cellular types share phenotypical properties (migration, survival, proliferation) and are able to give a heterogeneous cellular population. The development of a protocol that turns proliferative tumoral cells into migratory metastatic ones (and vice versa) led us to a syncretic concept in which tumoral cells, metastases and stem cells notions are merging. In this concept, tumoral cells (which result or not from healthy stem cells), are able to reversibly change their phenotype to form metastases (‘epithelial-mesenchymal transition' equivalent). Reversibility is actually an essential concept because it may explain how a metastatic cell, once established, can be activated again and become a proliferative tumoral cell. That also implies that metastases, able to remain several months in dormancy, share the same mechanisms as stem cells ones.Lastly, the study of new angiogenesis regulation pathways - which provides to metastases the means of leaving the primary tumour - involving on the one hand PAR1 thrombin receptor, and on the other hand chemokine CXCL4 (also called PF4), may lead to the development of new therapeutic molecules

Therapy-induced developmental reprogramming of prostate cancer cells and acquired therapy resistance

Treatment-induced neuroendocrine transdifferentiation (NEtD) complicates therapies for metastatic prostate cancer (PCa). Based on evidence that PCa cells can transdifferentiate to other neuroectodermally-derived cell lineages in vitro, we proposed that NEtD requires first an intermediary reprogramming to metastable cancer stem-like cells (CSCs) of a neural class and we demonstrate that several different AR+/PSA+ PCa cell lines were efficiently reprogrammed to, maintained and propagated as CSCs by growth in androgen-free neural/neural crest (N/NC) stem medium. Such reprogrammed cells lost features of prostate differentiation; gained features of N/NC stem cells and tumor-initiating potential; were resistant to androgen signaling inhibition; and acquired an invasive phenotype in vitro and in vivo. When placed back into serum-containing mediums, reprogrammed cells could be re-differentiated to N-/NC-derived cell lineages or return back to an AR+ prostate-like state. Once returned, the AR+ cells were resistant to androgen signaling inhibition. Acute androgen deprivation or anti-androgen treatment in serum-containing medium led to the transient appearance of a sub-population of cells with similar characteristics. Finally, a 132 gene signature derived from reprogrammed PCa cell lines distinguished tumors from PCa patients with adverse outcomes. This model may explain neural manifestations of PCa associated with lethal disease. The metastable nature of the reprogrammed stem-like PCa cells suggests that cycles of PCa cell reprogramming followed by re-differentiation may support disease progression and therapeutic resistance. The ability of a gene signature from reprogrammed PCa cells to identify tumors from patients with metastasis or PCa-specific mortality implies that developmental reprogramming is linked to aggressive tumor behaviors

Correction: Epidermal Growth Factor Receptor in Prostate Cancer Derived Exosomes

<p>Correction: Epidermal Growth Factor Receptor in Prostate Cancer Derived Exosomes</p

Epidermal Growth Factor Receptor in Prostate Cancer Derived Exosomes

<div><p>Exosomes proteins and microRNAs have gained much attention as diagnostic tools and biomarker potential in various malignancies including prostate cancer (PCa). However, the role of exosomes and membrane-associated receptors, particularly epidermal growth factor receptor (EGFR) as mediators of cell proliferation and invasion in PCa progression remains unexplored. EGFR is frequently overexpressed and has been associated with aggressive forms of PCa. While PCa cells and tissues express EGFR, it is unknown whether exosomes derived from PCa cells or PCa patient serum contains EGFR. The aim of this study was to detect and characterize EGFR in exosomes derived from PCa cells, LNCaP xenograft and PCa patient serum. Exosomes were isolated from conditioned media of different PCa cell lines; LNCaP xenograft serum as well as patient plasma/serum by differential centrifugation and ultracentrifugation on a sucrose density gradient. Exosomes were confirmed by electron microscopy, expression of exosomal markers and NanoSight^™ analysis. EGFR expression was determined by western blot analysis and ELISA. This study demonstrates that exosomes may easily be derived from PCa cell lines, serum obtained from PCa xenograft bearing mice and clinical samples derived from PCa patients. Presence of exosomal EGFR in PCa patient exosomes may present a novel approach for measuring of the disease state. Our work will allow to build on this finding for future understanding of PCa exosomes and their potential role in PCa progression and as minimal invasive biomarkers for PCa.</p></div

EGFR in PCa derived-exosomes.

<p>EGFR was present in exosomes derived from <b>a) panel</b> of AR-responsive and AR-unresponsive as well as benign prostate epithelial cells (RWPE-1) and compared with cell lysate, <b>b)</b> Control nude mouse and LNCaP xenograft serum. <b>c)</b> EGFR is contained in exosomes derived from four different PCa patients’ plasma (1–4), 3 serum samples (5–7) and control subject and in unprocessed plasma from control subject and patient (1 and 2). <b>d)</b> The expression of EGFR at 170kDa and 110kDa in serum and plasma is increased with increasing loading protein concentration. Interestingly, there is a significant amount of EGFR in unprocessed plasma which is in addition to the exosomal fraction. The histogram <b>(e)</b> shows EGFR levels (ng/ml) measured by ELISA in unprocessed plasma from control subject and PCa patient plasma/serum and exosomes derived from corresponding plasma/serum. The levels of serum EGFR are relatively similar in control and PCa subjects whereas exosomes isolated from PCa patient serum contained significantly higher amounts of EGFR than the control subject. Data represented as mean ±SEM, *p<0.05.</p

Exosome isolation from plasma is validated by the presence of exosome markers.

<p><b>a)</b> CD9 was present in exosomes derived from LNCaP xenograft mice bearing small, medium and large LNCaP tumours whereas the control mouse serum lacked CD9. GRP94, a known endoplasmic reticulum protein which is used as a negative control was absent in the exosomes suggesting enrichment <b>b)</b> LAMP2 was present in exosomes derived from PCa patient plasma whereas absence of LAMP2 in whole plasma indicated successful enrichment. <b>c)</b> Alix was present in exosomes derived from patient plasma at different exosomal protein concentrations.</p

Inhibiting Endothelial Cell Function in Normal and Tumor Angiogenesis Using BMP Type I Receptor Macrocyclic Kinase Inhibitors

Angiogenesis, i.e., the formation of new blood vessels from pre-existing endothelial cell (EC)-lined vessels, is critical for tissue development and also contributes to neovascularization-related diseases, such as cancer. Vascular endothelial growth factor (VEGF) and bone morphogenetic proteins (BMPs) are among many secreted cytokines that regulate EC function. While several pharmacological anti-angiogenic agents have reached the clinic, further improvement is needed to increase clinical efficacy and to overcome acquired therapy resistance. More insights into the functional consequences of targeting specific pathways that modulate blood vessel formation may lead to new therapeutic approaches. Here, we synthesized and identified two macrocyclic small molecular compounds termed OD16 and OD29 that inhibit BMP type I receptor (BMPRI)-induced SMAD1/5 phosphorylation and downstream gene expression in ECs. Of note, OD16 and OD29 demonstrated higher specificity against BMPRI activin receptor-like kinase 1/2 (ALK1/2) than the commonly used small molecule BMPRI kinase inhibitor LDN-193189. OD29, but not OD16, also potently inhibited VEGF-induced extracellular regulated kinase MAP kinase phosphorylation in ECs. In vitro, OD16 and OD29 exerted strong inhibition of BMP9 and VEGF-induced ECs migration, invasion and cord formation. Using Tg (fli:EGFP) zebrafish embryos, we found that OD16 and OD29 potently antagonized dorsal longitudinal anastomotic vessel (DLAV), intra segmental vessel (ISV), and subintestinal vessel (SIV) formation during embryonic development. Moreover, the MDA-MB-231 breast cancer cell-induced tumor angiogenesis in zebrafish embryos was significantly decreased by OD16 and OD29. Both macrocyclic compounds might provide a steppingstone for the development of novel anti-angiogenesis therapeutic agents

Representative graphs of NanoSight^™ particle tracking analysis.

<p>The analysis showed that mean size of exosomes isolated from control mouse was 126 nm <b>(a)</b> whereas LNCaP xenografted mice bearing small tumour was 81nm (b), 137 nm from medium <b>(c)</b> and 67 nm from large tumours <b>(d)</b>. The concentration of exosomes secreted increased with the increasing size of the tumour.</p

Information of PCa plasma and serum used to derive exosomes.

<p>Information of PCa plasma and serum used to derive exosomes.</p

TEM analysis show presence of exosomes.

<p>Representative TEM images of exosomes derived from <b>a)</b> C42 PCa cell line <b>b)</b> LNCaP xenograft serum and <b>c)</b> patient plasma by ultracentrifugation method. Exosomes were negatively stained with 2% uracyl acetate after removal of moisture. Arrows indicate cup-shaped structures which are identified as exosomes (30–100 nm in diameter).</p