No abstract

Tumor- or cancer-associated fibroblasts (CAFs) are one of the most abundant stromal cell types in different carcinomas and comprise a heterogeneous cell population. Classically, CAFs are assigned with pro-tumorigenic effects stimulating tumor growth and progression. More recent studies demonstrated also tumor-inhibitory effects of CAFs suggesting that tumor-residing fibroblasts exhibit a similar degree of plasticity as other stromal cell types. Reciprocal interactions with the tumor milieu and different sources of origin are emerging as two important factors underlying CAF heterogeneity. This review highlights recent advances in our understanding of CAF biology and proposes to expand the term of cellular “polarization,” previously introduced to describe different activation states of various immune cells, onto CAFs to reflect their phenotypic diversity.

This study explored the role of secreted fibroblast-derived factors in prostate cancer growth. Analyses of matched normal and tumor tissue revealed up-regulation of CXCL14 in cancer-associated fibroblasts of a majority of prostate cancer. Fibroblasts overexpressing CXCL14 promoted the growth of prostate cancer xenografts, and increased tumor angiogenesis and macrophage infiltration. Mechanistic studies demonstrated that autocrine CXCL14-stimulation of fibroblasts stimulate migration and ERKdependent proliferation of fibroblasts. CXCL14-stimulation of monocyte migration was also demonstrated. Furthermore, CXCL14-producing fibroblasts, but not recombinant CXCL14, enhanced in vitro proliferation and migration of prostate cancer cells and in vivo angiogenesis. These studies thus identify CXCL14 as a novel autocrine stimulator of fibroblast growth and migration, with multi-modal tumor-stimulatory activities. In more general terms, our findings suggest autocrine stimulation of fibroblasts as a previously unrecognized mechanism for chemokine-mediated stimulation of tumor growth, and suggest a novel mechanism whereby cancer-associated fibroblasts achieve their pro-tumorigenic phenotype.cancer-associated fibroblasts ͉ prostate cancer ͉ tumor stroma

Cancer cells adapt to their inherently increased oxidative stress through activation of the glutathione (GSH) and thioredoxin (TXN) systems. Inhibition of both of these systems effectively kills cancer cells, but such broad inhibition of antioxidant activity also kills normal cells, which is highly unwanted in a clinical setting. We therefore evaluated targeting of the TXN pathway alone and, more specifically, selective inhibition of the cytosolic selenocysteine-containing enzyme TXN reductase 1 (TXNRD1). TXNRD1 inhibitors were discovered in a large screening effort and displayed increased specificity compared to pan-TXNRD inhibitors, such as auranofin, that also inhibit the mitochondrial enzyme TXNRD2 and additional targets. For our lead compounds, TXNRD1 inhibition correlated with cancer cell cytotoxicity, and inhibitor-triggered conversion of TXNRD1 from an antioxidant to a pro-oxidant enzyme correlated with corresponding increases in cellular production of HO In mice, the most specific TXNRD1 inhibitor, here described as TXNRD1 inhibitor 1 (TRi-1), impaired growth and viability of human tumor xenografts and syngeneic mouse tumors while having little mitochondrial toxicity and being better tolerated than auranofin. These results display the therapeutic anticancer potential of irreversibly targeting cytosolic TXNRD1 using small molecules and present potent and selective TXNRD1 inhibitors. Given the pronounced up-regulation of TXNRD1 in several metastatic malignancies, it seems worthwhile to further explore the potential benefit of specific irreversible TXNRD1 inhibitors for anticancer therapy.

Ras-GTP imaging studies using the Ras-binding domain (RBD) of the Ras effector c-Raf as a reporter for overexpressed Ras have produced discrepant results about the possible activation of Ras at the Golgi apparatus. We report that RBD oligomerization provides probes for visualization of endogenous Ras-GTP, obviating Ras overexpression and the side effects derived thereof. RBD oligomerization results in tenacious binding to Ras-GTP and interruption of Ras signalling. Trimeric RBD probes fused to green fluorescent protein report agonist-induced endogenous Ras activation at the plasma membrane (PM) of COS-7, PC12 and Jurkat cells, but do not accumulate at the Golgi. PM illumination is exacerbated by Ras overexpression and its sensitivity to dominant-negative RasS17N and pharmacological manipulations matches Ras-GTP formation assessed biochemically. Our data illustrate that endogenous Golgi-located Ras is not under the control of growth factors and argue for the PM as the predominant site of agonist-induced Ras activation.