In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Metformin is a widely used antidiabetic agent, which regulates glucose homeostasis through inhibition of liver glucose production and an increase in muscle glucose uptake. Recent studies suggest that metformin may reduce the risk of cancer, but its mode of action in cancer remains not elucidated. We investigated the effect of metformin on human prostate cancer cell proliferation in vitro and in vivo. Metformin inhibited the proliferation of DU145, PC-3 and LNCaP cancer cells with a 50% decrease of cell viability and had a modest effect on normal prostate epithelial cell line P69. Metformin did not induce apoptosis but blocked cell cycle in G 0 /G 1 . This blockade was accompanied by a strong decrease of cyclin D1 protein level, pRb phosphorylation and an increase in p27 kip protein expression. Metformin activated the AMP kinase pathway, a fuel sensor signaling pathway. However, inhibition of the AMPK pathway using siRNA against the two catalytic subunits of AMPK did not prevent the antiproliferative effect of metformin in prostate cancer cells. Importantly, oral and intraperitoneal treatment with metformin led to a 50 and 35% reduction of tumor growth, respectively, in mice bearing xenografts of LNCaP. Similar, to the in vitro study, metformin led to a strong reduction of cyclin D1 protein level in tumors providing evidence for a mechanism that may contribute to the antineoplastic effects of metformin suggested by recent epidemiological studies.

Metformin is a widely prescribed antidiabetic drug associated with a reduced risk of cancer. Many studies show that metformin inhibits cancer cell viability through the inhibition of mTOR. We recently showed that antiproliferative action of metformin in prostate cancer cell lines is not mediated by AMP-activated protein kinase (AMPK). We identified REDD1 (also known as DDIT4 and RTP801), a negative regulator of mTOR, as a new molecular target of metformin. We show that metformin increases REDD1 expression in a p53-dependent manner. REDD1 invalidation, using siRNA or REDD1 À/À cells, abrogates metformin inhibition of mTOR. Importantly, inhibition of REDD1 reverses metformin-induced cell-cycle arrest and significantly protects from the deleterious effects of metformin on cell transformation. Finally, we show the contribution of p53 in mediating metformin action in prostate cancer cells. These results highlight the p53/REDD1 axis as a new molecular target in anticancer therapy in response to metformin treatment. Cancer Res; 71(13); 4366-72. '2011 AACR.

that is activated and on the cellular model analysed. In addition, the duration of the stimulus can also affect the cellular response. A wide panel of different stimuli are capable to activate the MAPK pathways, but a good correlation has been found between the types of stimulus and the function assigned to the pathway. Schematically, ERK is preferentially activated by mitogens such as the serum or growth factors and, accordingly, this pathway is an important regulator of cell cycle and cell proliferation. p38 and JNK are more responsive to various stress stimuli from UV to cytokines and they have been involved in apoptosis and/or in the response to cellular stresses. Because they have been extensively studied (see for reviews [2] [3]), these general aspects will not be detailed in this review, except for their specific relevance towards adipogenesis.Regarding the process of differentiation, the role of MAPKs is extremely complex and depends on multiple parameters. The complexity is due, firstly, to the biological process itself, which, most of the time, involves different successive steps. Furthermore, each of these steps can be modulated by MAPKs leading, sometimes, to opposite effects. Probably because this complexity renders experimental models extremely sensitive, most of the tools used for Because of its essential role in cell proliferation and the fact that adipogenic stimuli, such as insulin, activate the ERK pathway, the role of this pathway in normal and pathological adipogenesis has been intensively investigated the last decade. Indeed, obesity is due to the hypertrophy of adipocytes and to the recruitment of new adipocytes from precursor cells, two processes largely dependent on regulation of adipocyte differentiation. In addition, obesity is associated with insulin resistance both in experimental models and in humans, and the role of adipose tissue and, consequently, of adipocyte differentiation is important in this pathology. Although the implication of MAPKs in insulin resistance is largely documented, our review does not discuss this aspect in details because Gual et al. review it in this series.Although much of the knowledge originates from analysis of preadipocyte cell lines, such as 3T3-L1 or 3T3-F442A, various cellular models are now available; they are summarized in figure 2.