Cancer-associated fibroblasts (CAF) engage in tumor progression by promoting the ability of cancer cells to undergo epithelial-mesenchymal transition (EMT), and also by enhancing stem cells traits and metastatic dissemination. Here we show that the reciprocal interplay between CAFs and prostate cancer cells goes beyond the engagement of EMT to include mutual metabolic reprogramming. Gene expression analysis of CAFs cultured ex vivo or human prostate fibroblasts obtained from benign prostate hyperplasia revealed that CAFs undergo Warburg metabolism and mitochondrial oxidative stress. This metabolic reprogramming toward a Warburg phenotype occurred as a result of contact with prostate cancer cells. Intercellular contact activated the stromal fibroblasts, triggering increased expression of glucose transporter GLUT1, lactate production, and extrusion of lactate by de novo expressed monocarboxylate transporter-4 (MCT4). Conversely, prostate cancer cells, upon contact with CAFs, were reprogrammed toward aerobic metabolism, with a decrease in GLUT1 expression and an increase in lactate upload via the lactate transporter MCT1. Metabolic reprogramming of both stromal and cancer cells was under strict control of the hypoxia-inducible factor 1 (HIF1), which drove redox-and SIRT3-dependent stabilization of HIF1 in normoxic conditions. Prostate cancer cells gradually became independent of glucose consumption, while developing a dependence on lactate upload to drive anabolic pathways and thereby cell growth. In agreement, pharmacologic inhibition of MCT1-mediated lactate upload dramatically affected prostate cancer cell survival and tumor outgrowth. Hence, cancer cells allocate Warburg metabolism to their corrupted CAFs, exploiting their byproducts to grow in a low glucose environment, symbiotically adapting with stromal cells to glucose availability. Cancer Res; 72(19); 5130-40. Ó2012 AACR.

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Low molecular weight protein tyrosine phosphatase (LMW-PTP) is an enzyme involved in platelet-derived growth factor (PDGF)-induced mitogenesis and cytoskeleton rearrangement because it is able to bind and dephosphorylate the activated receptor. LMW-PTP presents two cysteines in positions 12 and 17, both belonging to the catalytic pocket; this is a unique feature of LMW-PTP among all protein tyrosine phosphatases. Our previous results demonstrated that in vitro LMW-PTP is oxidized by either H 2 O 2 or nitric oxide with the formation of a disulfide bond between Cys-12 and Cys-17. This oxidation leads to reversible enzyme inactivation because treatment with reductants permits catalytic activity rescue. In the present study we investigated the in vivo inactivation of LMW-PTP by either extracellularly or intracellularly generated H 2 O 2 , evaluating its action directly on its natural substrate, PDGF receptor. LMW-PTP is oxidized and inactivated by exogenous oxidative stress and recovers its activity after oxidant removal. LMW-PTP is oxidized also during PDGF signaling, very likely upon PDGF-induced H 2 O 2 production, and recovers its activity within 40 min. Our results strongly suggest that reversibility of in vivo LMW-PTP oxidation is glutathione-dependent. In addition, we propose an intriguing and peculiar role of Cys-17 in the formation of a S-S intramolecular bond, which protects the catalytic Cys-12 from further and irreversible oxidation. On the basis of our results we propose that the presence of an additional cysteine near the catalytic cysteine could confer to LMW-PTP the ability to rapidly recover its activity and finely regulate PDGF receptor activation during both extracellularly and intracellularly generated oxidative stress.Protein tyrosine phosphorylation plays a key role in the regulation of many cellular processes in eukaryotes such as cellular metabolism, proliferation, differentiation, and oncogenic transformation (1). Accumulating evidence indicates that the contribution of phosphotyrosine protein phosphatases (PTPs) 1 to the control of the cell phosphorylation state is as relevant as that of phosphotyrosine protein kinases. The PTP superfamily is composed of over 70 enzymes that, despite very limited sequence similarity, share a common CX 5 R active site motif and an identical catalytic mechanism. On the basis of their function, structure, and sequence, PTPs can be classified in four main families: 1) tyrosine-specific phosphatases, 2) VH1-like dual specificity PTPs, 3) the cdc25 phosphatases, and 4) the low molecular weight phosphatase (2).The low molecular weight protein tyrosine phosphatase (LMW-PTP) is an 18-kDa enzyme that is expressed in many mammalian tissues (3). Our previous studies on the molecular biology of LMW-PTP in NIH3T3 cells demonstrated a well defined role of this enzyme in platelet-derived growth factor (PDGF)-induced mitogenesis. The most relevant phenotypic effect of LMW-PTP overexpression is a strong reduction of the cell growth rate in response to PDGF stimulation. We ...

Tumor stromal cells can supply appropriate signals that may develop aggressive phenotypes of carcinoma cells and establish a complex scenario which culminates in metastasis. Recent works proposed that bone marrow-derived mesenchymal stem cells (MSC) are recruited to primary tumors. However, the exact functions of these cells in the tumor microenvironment are not well characterized, as it is reported that MSC can either promote or inhibit tumor progression. In the present study, we aim at investigating the signaling molecules which regulate the interplay between MSC, prostate carcinoma (PCa) cells and two important cellular types constituting the tumor-associated stroma, macrophages and fibroblasts, during their progression toward malignancy. We identified TGF-β1 as a crucial molecule able to attract MSC recruitment both to PCa cells as well as to tumor stroma components. Moreover, PCa- and tumor stroma-secreted TGF-β1 is important to induce MSC transdifferentiation into carcinoma-associated fibroblast (CAF)-like cells. Consequently, the CAF-like phenotype acquired by MSC is central to promote tumor progression related effects. Thus, tumor-educated MSC enhance PCa invasiveness compared to nonactivated MSC. Additionally, differing from normal MSC, CAF-like MSC perform vascular mimicry and recruit monocytes, which can be further polarized to M2 macrophages within the PCa environment. Our findings indicate a prominent role for TGF-β1 in MSC mobilization and activation strengthened by the fact that the blockade of TGF-β1 signaling impairs MSC promotion of PCa progression. Stem Cells 2016;34:2536-2547.