[PubMed] [Google Scholar] 43. further validated that these novel mitochondrial inhibitors metabolically target mitochondrial respiration in cancer cells and effectively inhibit the propagation of cancer stem-like cells – a pathogenic yeast. Remarkably, these novel antibiotics also were effective against methicillin-resistant Staphylococcus aureus (MRSA). Thus, this simple, yet systematic, approach to the discovery of mitochondrial ribosome inhibitors could provide a plethora of anti-microbials and anti-cancer therapies, to target drug-resistance that is characteristic of both i) tumor recurrence and ii) infectious disease. In summary, we have successfully used vHTS combined with Chlorogenic acid phenotypic drug screening of human cancer cells to identify several new classes of broad-spectrum antibiotics that target both bacteria and pathogenic yeast. We propose the new term mitoriboscins to describe these novel mitochondrial-related antibiotics. Thus far, we have identified four different classes of mitoriboscins, such as: = 28 patients) revealed that 95 mRNA transcripts associated with mitochondrial biogenesis and/or mitochondrial translation are significantly elevated in cancer cells, as compared with adjacent stromal tissue [10, 11]. Remarkably, 35 of these 95 upregulated mRNAs encode mitochondrial ribosomal proteins (MRPs) . MRPs are the functional subunits of the mitochondrial ribosomes (mitoribosomes), which are responsible for the mitochondrial translation of 13 protein components of the OXPHOS complex encoded by mitochondrial DNA. In this context, MRPS gene products are used to form the small subunit of the mitoribosome, while MRPL gene products are used to generate the large subunit of the mitoribosome [12C15]. Most of these 36 mitoribosome-related Chlorogenic acid mRNA transcripts were elevated between 2- to 5-fold in human breast cancer cells, including seventeen members of the MRPS gene family (S7, S11, S12, S13, S14, S15, S17, S18A, S18B, S22, S26, S27, S28, S30, S31, S33, S35) and nineteen members of the MRPL gene family (L3, L9, L15, L16, L17, L18, L20, L22, L24, L33, L39, L40, L42, L46, L48, L49, L52, L54, L57) . Proteomic analysis of human breast cancer stem-like cells also revealed the significant over-expression of several mitoribosomal proteins, such as MRPL45 and MRPL17, and 6 other proteins associated with mitochondrial biogenesis (HSPA9, TIMM8A, GFM1, HSPD1 [a.k.a., HSP60], TSFM, TUFM) . Importantly, functional inhibition of mitochondrial biogenesis, using the off-target effects of certain bacteriostatic antibiotics, effectively ablated the propagation of CSCs, in 12 cell Chlorogenic acid lines representing 8 different tumor types (breast, DCIS, prostate, ovarian, pancreatic, lung, melanoma and glioblastoma) [3, 5]. Virtually identical results were also obtained with OXPHOS inhibitors (pyrvinium pamoate and atovaquone), providing additional complementary evidence that functional mitochondria are required for the propagation of CSCs [3, 16]. Taken together, these preliminary studies provide the necessary evidence that the development of novel mitoribosome inhibitors might be a beneficial approach for the more effective treatment of cancer patients. Recently, the 3D structures of both the large (39S) and the small (28S) subunits of the mammalian mitoribosome (55S) have been resolved [17C22], allowing for the rationale molecular design of mitoribosome inhibitors. Here, we used the known 3D structure of the large 39S mammalian mitoribosome as a target to perform virtual high-throughput Chlorogenic acid screening (vHTS). We coupled this computational chemistry approach with phenotypic drug screening, allowing for the functional identification and validation of novel compounds targeting mammalian mitoribosomes. The ability of these mitochondrial inhibitors to functionally prevent oxygen-consumption and halt ATP production was also demonstrated TIAM1 by metabolic flux analysis. Most importantly, these mitochondrial inhibitors effectively blocked the propagation of CSC, Chlorogenic acid as predicted, providing proof-of-concept. Interestingly, we also show that these mitochondrial inhibitors behave as broad-spectrum antibiotics, which is consistent with the well-established hypothesis that mitochondria originally evolved from the engulfment of aerobic bacteria, approximately 1.5 billion years ago [23C28]. This has important implications for more effectively combating the development of antibiotic-resistance. RESULTS Exploiting the evolutionary relationship between bacteria and mitochondria, to drive the discovery of new antibiotics and novel anti-cancer agents The Endo-symbiotic Theory of Mitochondrial Evolution states that mitochondria originally evolved from aerobic bacteria that were incorporated into eukaryotic cells [23C28], during millions of years of adaptation (Figure ?(Figure1).1). Consistent with this theory, we have recently shown that certain classes of well-known antibiotics that inhibit bacterial protein synthesis [29C31], can also be used to successfully target mitochondrial protein translation, especially in cancer stem-like cells (CSCs) . Open in a separate window Figure 1 The endo-symbiotic theory of mitochondrial evolution: Implications for modern drug developmentNote that mitochondria originally evolved from engulfed aerobic bacteria, during millions of years of adaptation. A corollary of.