We investigated the metabolic profile of cancer stem cells (CSC) isolated from patients with epithelial ovarian cancer. CSC overexpressed genes associated with glucose uptake, oxidative phosphorylation (OXPHOS), and fatty acid β-oxidation, indicating higher ability to direct pyruvate towards the Krebs cycle. Consistent with a metabolic profile dominated by OXPHOS, the CSC showed higher mitochondrial reactive oxygen species (ROS) production and elevated membrane potential, and underwent apoptosis upon inhibition of the mitochondrial respiratory chain. The CSC also had a high rate of pentose phosphate pathway (PPP) activity, which is not typical of cells privileging OXPHOS over glycolysis, and may rather reflect the PPP role in recharging scavenging enzymes. Furthermore, CSC resisted in vitro and in vivo glucose deprivation, while maintaining their CSC phenotype and OXPHOS profile. These observations may explain the CSC resistance to anti-angiogenic therapies, and indicate this peculiar metabolic profile as a possible target of novel treatment strategies.

The miR-200 family of microRNAs (miRNAs) includes miR-200a, miR-200b, miR-200c, miR-141 and miR-429, five evolutionarily conserved miRNAs that are encoded in two clusters of hairpin precursors located on human chromosome 1 (miR-200b, miR-200a and miR-429) and chromosome 12 (miR-200c and miR-141). The mature -3p products of the precursors are abundantly expressed in epithelial cells, where they contribute to maintaining the epithelial phenotype by repressing expression of factors that favor the process of epithelial-to-mesenchymal transition (EMT), a key hallmark of oncogenic transformation. Extensive studies of the expression and interactions of these miRNAs with cell signaling pathways indicate that they can exert both tumor suppressor- and pro-metastatic functions, and may serve as biomarkers of epithelial cancers. This review provides a summary of the role of miR-200 family members in EMT, factors that regulate their expression, and important targets for miR-200-mediated repression that are involved in EMT. The second part of the review discusses the potential utility of circulating miR-200 family members as diagnostic/prognostic biomarkers for breast, colorectal, lung, ovarian, prostate and bladder cancers.

Human T-cell leukemia virus type 1 (HTLV-1) codes for 9 alternatively spliced transcripts and 2 major regulatory proteins named Tax and Rex that function at the transcriptional and posttranscriptional levels, respectively. We investigated the temporal sequence of HTLV-1 gene expression in primary cells from infected patients using splice site-specific quantitative RT-PCR. The results indicated a two-phase kinetics with the tax/rex mRNA preceding expression of other viral transcripts. Analysis of mRNA compartmentalization in cells transfected with HTLV-1 molecular clones demonstrated the strict Rex-dependency of the two-phase kinetics and revealed strong nuclear retention of HBZ mRNAs, supporting their function as noncoding transcripts. Mathematical modeling underscored the importance of a delay between the functions of Tax and Rex, which was supported by experimental evidence of the longer half-life of Rex. These data provide evidence for a temporal pattern of HTLV-1 expression and reveal major differences in the intracellular compartmentalization of HTLV-1 transcripts.

COQ2 (p-hydroxybenzoate polyprenyl transferase) encodes the enzyme required for the second step of the final reaction sequence of Coenzyme Q₁₀ (CoQ) biosynthesis. Its mutations represent a frequent cause of primary CoQ deficiency and have been associated with the widest clinical spectrum, ranging from fatal neonatal multisystemic disease to late-onset encephalopathy. However, the reasons of this variability are still unknown. We have characterized the structure of human COQ2, defined its subcellular localization and developed a yeast model to validate all the mutant alleles reported so far. Our findings show that the main functional transcript of COQ2 is shorter than what was previously reported and that its protein product localizes to mitochondria with the C-terminus facing the intermembrane space. Complementation experiments in yeast showed that the residual activity of the mutant proteins correlates with the clinical phenotypes observed in patients. We defined the structure of COQ2 with relevant implications for mutation screening in patients and demonstrated that, contrary to other COQ gene defects such as ADCK3, there is a correlation between COQ2 genotype and patient’s phenotype.

Human T-cell leukemia virus type 1 encodes a number of “accessory” proteins of unclear function; one of these proteins, p13^II, is targeted to mitochondria and disrupts mitochondrial morphology. The present study was undertaken to unravel the function of p13^II through (i) determination of its submitochondrial localization and sequences required to alter mitochondrial morphology and (ii) an assessment of the biophysical and biological properties of synthetic peptides spanning residues 9–41 (p13^9–41), which include the amphipathic mitochondrial-targeting sequence of the protein. p13^9–41 folded into an α helix in micellar environments. Fractionation and immunogold labeling indicated that full-length p13^II accumulates in the inner mitochondrial membrane. p13^9–41 induced energy-dependent swelling of isolated mitochondria by increasing inner membrane permeability to small cations (Na⁺, K⁺) and released Ca²⁺ from Ca²⁺-preloaded mitochondria. These effects as well as the ability of full-length p13^II to alter mitochondrial morphology in cells required the presence of four arginines, forming the charged face of the targeting signal. The mitochondrial effects of p13^9–41 were insensitive to cyclosporin A, suggesting that full-length p13^II might alter mitochondrial permeability through a permeability transition pore-independent mechanism, thus distinguishing it from the mitochondrial proteins Vpr and X of human immunodeficiency virus type 1 and hepatitis B virus, respectively.

Human T cell leukemia virus type 1 encodes an “accessory” protein named p13 ^II that is targeted to mitochondria and triggers a rapid flux of K ⁺ and Ca ²⁺ across the inner membrane. In this study, we investigated the effects of p13 ^II on tumorigenicity in vivo and on cell growth in vitro . Results showed that p13 ^II significantly reduced the incidence and growth rate of tumors arising from c-myc and Ha-ras-cotransfected rat embryo fibroblasts. Consistent with these findings, HeLa-derived cell lines stably expressing p13 ^II exhibited markedly reduced tumorigenicity, as well as reduced proliferation at high density in vitro . Mixed culture assays revealed that the phenotype of the p13 ^II cell lines was dominant over that of control lines and was mediated by a heat-labile soluble factor. The p13 ^II cell lines exhibited an enhanced response to Ca ²⁺ -mediated stimuli, as measured by increased sensitivity to C2-ceramide-induced apoptosis and by cAMP-responsive element-binding protein (CREB) phosphorylation in response to histamine. p13 ^II -expressing Jurkat T cells also exhibited reduced proliferation, suggesting that the protein might exert similar effects in T cells, the primary target of HTLV-1 infection. These findings provide clues into the function of p13 ^II as a negative regulator of cell growth and underscore a link between mitochondria, Ca ²⁺ signaling, and tumorigenicity.