RAC1(P29S) Induces a Mesenchymal Phenotypic Switch via Serum Response Factor to Promote Melanoma Development and Therapy Resistance

RAC1 P29 is the third most commonly mutated codon in human cutaneous melanoma, after BRAF V600 and NRAS Q61. Here, we study the role of RAC1P29S in melanoma development and reveal that RAC1P29S activates PAK, AKT, and a gene expression program initiated by the SRF/MRTF transcriptional pathway, which results in a melanocytic to mesenchymal phenotypic switch. Mice with ubiquitous expression of RAC1P29S from the endogenous locus develop lymphoma. When expressed only in melanocytes, RAC1P29S cooperates with oncogenic BRAF or with NF1-loss to promote tumorigenesis. RAC1P29S also drives resistance to BRAF inhibitors, which is reversed by SRF/MRTF inhibitors. These findings establish RAC1P29S as a promoter of melanoma initiation and mediator of therapy resistance, while identifying SRF/MRTF as a potential therapeutic target

Towards precision medicine: defining and characterizing adipose tissue dysfunction to identify early immunometabolic risk in symptom-free adults from the GEMM family study

Interactions between macrophages and adipocytes are early molecular factors influencing adipose tissue (AT) dysfunction, resulting in high leptin, low adiponectin circulating levels and low-grade metaflammation, leading to insulin resistance (IR) with increased cardiovascular risk. We report the characterization of AT dysfunction through measurements of the adiponectin/leptin ratio (ALR), the adipo-insulin resistance index (Adipo-IRi), fasting/postprandial (F/P) immunometabolic phenotyping and direct F/P differential gene expression in AT biopsies obtained from symptom-free adults from the GEMM family study. AT dysfunction was evaluated through associations of the ALR with F/P insulin-glucose axis, lipid-lipoprotein metabolism, and inflammatory markers. A relevant pattern of negative associations between decreased ALR and markers of systemic low-grade metaflammation, HOMA, and postprandial cardiovascular risk hyperinsulinemic, triglyceride and GLP-1 curves was found. We also analysed their plasma non-coding microRNAs and shotgun lipidomics profiles finding trends that may reflect a pattern of adipose tissue dysfunction in the fed and fasted state. Direct gene differential expression data showed initial patterns of AT molecular signatures of key immunometabolic genes involved in AT expansion, angiogenic remodelling and immune cell migration. These data reinforce the central, early role of AT dysfunction at the molecular and systemic level in the pathogenesis of IR and immunometabolic disorders

A critical tyrosine residue of the mitochondrial oxaloacetate carrier determines its uncoupling protein (UCP)-like function in yeast

9 páginas, 5 figuras, 1 tabla -- PAGS nros. 317-325The mitochondrial Oac (oxaloacetate carrier) found in some fungi and plants catalyses the uptake of oxaloacetate, malonate and sulfate. Despite their sequence similarity, transport specificity varies considerably between Oacs. Indeed, whereas ScOac (Saccharomyces cerevisiae Oac) is a specific anion–proton symporter, the YlOac (Yarrowia lipolytica Oac) has the added ability to transport protons, behaving as a UCP (uncoupling protein). Significantly, we identified two amino acid changes at the matrix gate of YlOac and ScOac, tyrosine to phenylalanine and methionine to leucine. We studied the role of these amino acids by expressing both wild-type and specifically mutated Oacs in an Oac-null S. cerevisiae strain. No phenotype could be associated with the methionine to leucine substitution, whereas UCP-like activity was dependent on the presence of the tyrosine residue normally expressed in the YlOac, i.e. Tyr-ScOac mediated proton transport, whereas Phe-YlOac lost its protonophoric activity. These findings indicate that the UCP-like activity of YlOac is determined by the tyrosine residue at position 146This work was partially supported by the CONACYT (Consejo Nacional de Ciencia y Tecnología) [grant numbers 79989 (to S.U.C.) and 80684 (to D.G.)], the DGAPA/UNAM (Dirección General Asuntos del Personal Académico/Universidad Nacional Autónoma de México) [grant numbers IN217109 (to S.U.C.) and IN219709-3 (to D.G.)], the ICGEB (International Centre for Genetic Engineering and Biotechnology) [grant number CRPMEX008-02 (to D.G.)] and the Spanish Consolider-Ingenio project [grant number CSD2007-00020 (to E.R.)]. L.A.L.-M., D.A.-O. and C.B.-O. are CONACYT fellows enrolled in the Biochemistry Graduate Program at UNAMPeer reviewe

The cytotoxicity effect of 7-hydroxy-3,4-dihydrocadalene from Heterotheca inuloides and semisynthetic cadalenes derivates towards breast cancer cells: involvement of oxidative stress-mediated apoptosis

Background Heterotheca inuloides, traditionally employed in Mexico, has demonstrated anticancer activities. Although it has been proven that the cytotoxic effect is attributed to cadinane-type sesquiterpenes such as 7-hydroxy-3,4-dihydrocadalene, the mechanism of action by which these agents act in tumor lines and their regulation remain unknown. This study was undertaken to investigate for first time the cytotoxic activity and mechanism of action of 7-hydroxy-3,4-dihydrocadalene and two semi-synthetic cadinanes derivatives towards breast cancer cells. Methods Cell viability and proliferation were assayed by thiazolyl blue tetrazolium bromide (MTT) assay and Trypan blue dye exclusion assay. Cell migration measure was tested by wound-healing assay. Moreover, the reactive oxygen species (ROS) and lipid peroxidation generation were measured by 2′,7′-dichlorofluorescein diacetate (DCFH-DA) assay and thiobarbituric acid reactive substance (TBARS) assay, respectively. Furthermore, expression of caspase-3, Bcl-2 and GAPDH were analyzed by western blot. Results The results showed that 7-hydroxy-3,4-dihydrocadalene inhibited MCF7 cell viability in a concentration and time dependent manner. The cytotoxic potency of semisynthetic derivatives 7-(phenylcarbamate)-3,4-dihydrocadalene and 7-(phenylcarbamate)-cadalene was remarkably lower. Moreover, in silico studies showed that 7-hydroxy-3,4-dihydrocadalene, and not so the semi-synthetic derivatives, has optimal physical-chemical properties to lead a promising cytotoxic agent. Further examination on the action mechanism of 7-hydroxy-3,4-dihydrocadalene suggested that this natural product exerted cytotoxicity via oxidative stress as evidenced in a significantly increase of intracellular ROS levels and in an induction of lipid peroxidation. Furthermore, the compound increased caspase-3 and caspase-9 activities and slightly inhibited Bcl-2 levels. Interestingly, it also reduced mitochondrial ATP synthesis and induced mitochondrial uncoupling. Conclusion Taken together, 7-hydroxy-3,4-dihydrocadalene is a promising cytotoxic compound against breast cancer via oxidative stress-induction