The voltage-dependent anion channel 1 (VDAC1), localized in the outer mitochondrial membrane, mediates metabolic cross-talk between the mitochondrion and the cytoplasm and thus serves a fundamental role in cell energy metabolism. VDAC1 also plays a key role in mitochondria-mediated apoptosis, interacting with anti-apoptotic proteins. Resistance of cancer cells to apoptosis involves quenching the mitochondrial apoptotic pathway by over-expression of anti-apoptotic/pro-survival hexokinase (HK) and Bcl-2 family proteins, proteins that mediate their anti-apoptotic activities via interaction with VDAC1. Using specifically designed VDAC1-based cell-penetrating peptides, we targeted these anti-apoptotic proteins to prevent their pro-survival/anti-apoptotic activities. Anti-apoptotic proteins are expressed at high levels in B-cell chronic lymphocytic leukemia (CLL), an incurable disease requiring innovative new approaches to improve therapeutic outcome. CLL is characterized by a clonal accumulation of mature neoplastic B cells that are resistant to apoptosis. Specifically, we demonstrate that the VDAC1-based peptides (Antp-LP4 and N-Terminal-Antp) selectively kill peripheral blood mononuclear cells (PBMCs) obtained from CLL patients, yet spare those obtained from healthy donors. The cell death induction competence of the peptides was well correlated with the amount of double positive CD19/CD5 cancerous CLL PBMCs, further illustrating their selectivity toward cancer cells. Moreover, these VDAC1-based peptides induced apoptosis by activating the mitochondria-mediated pathway, reflected in membrane blebbing, condensation of nuclei, DNA fragmentation, release of mitochondrial cytochrome c, loss of mitochondrial membrane potential, decreased cellular ATP levels and detachment of HK, all leading to apoptotic cell death. Thus, the mode of action of the peptides involves decreasing energy production and inducing apoptosis. Over 27 versions of cell-penetrating VDAC1-based peptides were designed and screened to identify the most stable, short and apoptosis-inducing peptides toward CLL-derived lymphocytes. In this manner, three optimized peptides suitable for in vivo studies were identified. This study thus reveals the potential of VDAC1-based peptides as an innovative and effective anti-CLL therapy.

In many cancers, cells undergo re-programming of metabolism, cell survival and anti-apoptotic defense strategies, with the proteins mediating this reprogramming representing potential biomarkers. Here, we searched for novel biomarker proteins in chronic lymphocytic leukemia (CLL) that can impact diagnosis, treatment and prognosis by comparing the protein expression profiles of peripheral blood mononuclear cells from CLL patients and healthy donors using specific antibodies, mass spectrometry and binary logistic regression analyses and other bioinformatics tools. Mass spectrometry (LC-HR-MS/MS) analysis identified 1,360 proteins whose expression levels were modified in CLL-derived lymphocytes. Some of these proteins were previously connected to different cancer types, including CLL, while four other highly expressed proteins were not previously reported to be associated with cancer, and here, for the first time, DDX46 and AK3 are linked to CLL. Down-regulation expression of two of these proteins resulted in cell growth inhibition. High DDX46 expression levels were associated with shorter survival of CLL patients and thus can serve as a prognosis marker. The proteins with modified expression include proteins involved in RNA splicing and translation and particularly mitochondrial proteins involved in apoptosis and metabolism. Thus, we focused on several metabolism- and apoptosis-modulating proteins, particularly on the voltage-dependent anion channel 1 (VDAC1), regulating both metabolism and apoptosis. Expression levels of Bcl-2, VDAC1, MAVS, AIF and SMAC/Diablo were markedly increased in CLL-derived lymphocytes. VDAC1 levels were highly correlated with the amount of CLL-cancerous CD19+/CD5+ cells and with the levels of all other apoptosis-modulating proteins tested. Binary logistic regression analysis demonstrated the ability to predict probability of disease with over 90% accuracy. Finally, based on the changes in the levels of several proteins in CLL patients, as revealed from LC-HR-MS/MS, we could distinguish between patients in a stable disease state and those who would be later transferred to anti-cancer treatments. The over-expressed proteins can thus serve as potential biomarkers for early diagnosis, prognosis, new targets for CLL therapy, and treatment guidance of CLL, forming the basis for personalized therapy.

Much progress has been made in the identification of proteins that mediate mitochondrial fusion, as well as in the elucidation of their role in mitochondrial quality control. Yet, while deficiency of mitochondrial fusion seems to induce a mitochondrial dysfunction suggesting a requirement of fusion for oxidative metabolism, the cause of the dysfunction is unclear. We have undertaken a bioenergetics analysis to understand the basis of the mitochondrial dysfunction, using intact mouse embryonic fibroblasts deficient in mitofusin1 and mitofusin2 (DKO) incubated under conditions replete in glycolytic vs. oxidative substrate. We first noted an approximate doubling of the nonmitochondrial oxygen consumption (JO2) in DKO cells compared to wildtype (Wt) MEFs, regardless of substrate. Upon switching from primarily glycolytic to more oxidative conditions, DKO MEFs, similar to the Wt, increased basal mitochondrial JO2 (oligomycin-sensitiveþoligolycin-insensitive, non-mitochondrial subtracted), although the rise was smaller in DKO cells (an increase of 55511 vs. 114511 pmoles/min/40k cells in DKO vs. Wt; values: mean5sem). When only the oligomycin-sensitive respiration is considered, the rise was similar in DKO cells (an increase of 121.3510 vs. 135.8513 pmoles O 2 /min/40k cells in DKO vs. Wt), whereas the oligomycin-sensitive JO2 decreased in DKO cells only (by~50%). In both Wt and DKO cells, the rate of media acidification declined upon switching from glycolytic to oxidative substrate, indicating a shift from glycolytic to oxidative ATP production. Thus, as in Wt MEFs, DKO MEFs demonstrate a basal mitochondrial respiration controlled by ATP turnover and substrate oxidation. Differently from the Wt, DKO mitochondria can exert a significant control of basal JO2 by proton leak, which could function to compensate for any limitation in mitochondrial capacity.

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