manumycin and Neoplasms

Cancer is an uncontrolled cell growth that can generate diverse types of cancer, in which these will also present a different behavior in the face of pharmacological treatment. These cancers' types are found in one of the three categories, leukemias (also named lymphomas), carcinomas, and sarcomas. In general, cancer's pathogenesis is associated with three genetic mutations, where could emerge from oncogenes, tumor suppressor genes, and/or genes responsible for regulating DNA replication. The term "undruggable" is frequently related to the difficulty to design drugs to specific targets, such as MYC, MYB, NF-κB, and RAS family of proteins. This last comprises more than 140 proteins, and these are responsible for 30% of mutations in human cancers. Also, there are three ras genes transcribed in human cells, called H-, K-, and N-ras oncogenes. Still, the RAS proteins (farnesyltransferase (FTase) and geranylgeranyltransferase (GGTase) enzymes) perform essential steps in post-translational modification of eukaryotes cells, such as (1) the farnesylation of the cysteine residue at the C-terminal tetrapeptide CAAX; (2) proteolytic cleavage of the three C-terminal AAX oligopeptide; and (3) carboxymethylation of the new C-terminal prenylated cysteine. Thus, the inhibition of this undruggable RAS family of proteins has been considered a promising alternative to design new anticancer agents since they are responsible for many types of human cancers. Then, the manumycin A (obtained from the Streptomyces parvulus Tü64) and its analogs (epoxyquinol core with or without their southern and eastern side chains; and dihydroxycyclohexenones core) have been described as promising FTase inhibitors, which have demonstrated their benefits against several types of cancer. In this review, a complete introduction about cancer and its relation with RAS proteins is provided, as well as, the prenylation mechanism of the cysteine residue is discussed in detail. Posteriorly, studies involving manumycin-related compounds are described, showing some synthetic routes for obtaining them and utilizing these natural products in monotherapies or combined therapies with other anticancer drugs.

Topics: Alkyl and Aryl Transferases; Biological Products; Enzyme Inhibitors; Farnesyltranstransferase; Humans; Neoplasms; Polyenes; Polyunsaturated Alkamides

Manumycin A (MA) is a well-tolerated natural antibiotic showing pleiotropic anticancer effects in various preclinical in vitro and in vivo models. Anticancer drugs may themselves act as stressors to induce the cellular adaptive mechanism that can minimize their cytotoxicity. Heat shock proteins (HSPs) as cytoprotective factors can counteract the deleterious effects of various stressful stimuli. In this study, we examined whether the anticancer effects of MA can be counteracted by the mechanism related to HSPs belonging to the HSPA (HSP70) family. We found that MA caused cell type-specific alterations in the levels of HSPAs. These changes included concomitant upregulation of the stress-inducible (HSPA1 and HSPA6) and downregulation of the non-stress-inducible (HSPA2) paralogs. However, neither HSPA1 nor HSPA2 were necessary to provide protection against MA in lung cancer cells. Conversely, the simultaneous repression of several HSPA paralogs using pan-HSPA inhibitors (VER-155008 or JG-98) sensitized cancer cells to MA. We also observed that genetic ablation of the heat shock factor 1 (HSF1) transcription factor, a main transactivator of HSPAs expression, sensitized MCF7 cells to MA treatment. Our study reveals that inhibition of HSF1-mediated heat shock response (HSR) can improve the anticancer effect of MA. These observations suggest that targeting the HSR- or HSPA-mediated adaptive mechanisms may be a promising strategy for further preclinical developments.

Topics: A549 Cells; Antineoplastic Agents; Heat Shock Transcription Factors; Heat-Shock Response; HSP70 Heat-Shock Proteins; Humans; MCF-7 Cells; Neoplasm Proteins; Neoplasms; Polyenes; Polyunsaturated Alkamides

We have recently reported that Ras acts as an intermediate coactivator in IL-1β-mediated hypoxia-inducible factor-1α (HIF-1α) activation in glioblastoma multiforme (GBM). Since HIF-1α plays a crucial role in linking inflammatory and oncogenic pathways, we investigated whether this IL1β-Ras-HIF-1α signaling axis observed in GBM also exists in other tumors of diverse origin under normoxia. Treatment with IL-1β induced Ras in non-GBM cell lines A549 (lung), HeLa (cervical), and HepG2 (liver), and inhibition of Ras activity attenuated HIF-1α activity. Our findings suggest that Ras links IL-1β and HIF-1α in tumors of diverse origin. As we have previously reported that the farnesyltransferase inhibitor manumycin decreases Ras activity in glioma cells, we investigated whether manumycin could regulate IL-1β-mediated HIF-1α activation. Manumycin abrogated IL-1β-induced HIF-1α activation in both glioma and non-glioma tumor cells. In addition, manumycin also decreased IL-1β induced pro-inflammatory responses in tumor cells.

Topics: Cell Line, Tumor; Enzyme Inhibitors; Farnesyltranstransferase; HeLa Cells; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Interleukin-1beta; Neoplasms; Polyenes; Polyunsaturated Alkamides; ras Proteins

Farnesyltransferase inhibitors (FTIs) possess antitumor activity. Based on recent findings, we hypothesized that FTIs induce reactive oxygen species (ROS) that damage DNA, leading to DNA damage responses. To test this hypothesis, we investigated the effects of FTIs on the generation of ROS, DNA double-strand breaks (DSB), DNA damage responses, and RhoB, and the effects of quenching ROS on these FTI effects. We evaluated four FTIs in human cancer cell lines of different tissue origins. We found that FTIs induced ROS and DSBs. Suppressing expression of the beta-subunit of farnesyltransferase with siRNA did not induce ROS, but slightly attenuated the ROS induced by FTIs. N-acetyl-L-cysteine (NAC), but not caspase inhibitors, blocked FTI-induced DSBs, suggesting that the DSBs were caused by ROS and did not result from apoptosis. The DSBs led to DNA damage responses. H2AX became phosphorylated and formed nuclear foci. The DNA-damage-sensing molecules involved were probably ataxia-telangiectasia mutated protein (ATM) and DNA-dependent protein kinase (DNA-PK) but not ATM- and Rad3-related protein (ATR). Key components of the homologous recombination and nonhomologous end joining repair pathways (DNA-PK, BRCA1, and NBS1) underwent phosphorylation and formed nuclear foci. RhoB, a mediator of the antineoplastic effect of FTIs and a protein inducible by DNA damage, was increased by FTIs. This increase was blocked by NAC. We concluded that FTIs induced oxidative DNA damage by inducing ROS and initiated DNA damage responses, including RhoB induction, and there was a complex relationship among FTIs, farnesyltransferase, ROS, and RhoB. Our data also imply that inhibitors of DNA repair may accentuate the clinical efficacy of FTIs.

Topics: Alkyl and Aryl Transferases; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Line, Tumor; DNA Damage; DNA-Activated Protein Kinase; DNA-Binding Proteins; DNA, Neoplasm; Enzyme Inhibitors; Farnesyltranstransferase; HCT116 Cells; Humans; Neoplasms; Nuclear Proteins; Polyenes; Polyunsaturated Alkamides; Protein Serine-Threonine Kinases; Reactive Oxygen Species; rhoB GTP-Binding Protein; Tumor Suppressor Proteins

Recently, many inhibitors of farnesyl protein transferase (FPTase) have been identified. Some of them interrupt cell growth in addition to Ras and nuclear lamin processing of Ras-transformed cells. We have tested the effect of the FPTase inhibitors manumycin, an analogue of farnesyl diphosphate, and KT7595, a gliotoxin derivative, on Ras farnesylation, DNA synthesis and the anchorage-dependent and -independent growth of human colon carcinoma (LoVo), hepatoma (Mahlavu and PLC/PRF/5) and gastric carcinoma (KATO III). Both drugs severely inhibited DNA synthesis, cellular proliferation and Ras farnesylation in LoVo and moderately reduced them in Mahlavu and PLC/PRF/5 but not in KATO III. Complete sequencing of ras genes, however, revealed that LoVo and KATO III have activated Ki-ras and activated N-ras, respectively, whereas Mahlavu and PLC/PRF/5 have no activated ras. We next checked whether the inhibition of the cellular proliferation is due to the blocking of nuclear lamin function. Neither drug disturbed lamin farnesylation and localization, as demonstrated using metabolic labelling, immunoblotting and indirect immunofluorescence. These results indicate that manumycin and KT7595 can inhibit Ras farnesylation and cell growth without disturbing the farnesylation and localization of the lamins on human tumour cell lines.

Topics: Alkyl and Aryl Transferases; Carcinoma, Hepatocellular; Cell Division; Colonic Neoplasms; DNA, Neoplasm; Drug Screening Assays, Antitumor; Enzyme Inhibitors; Fluorescent Antibody Technique, Indirect; Gliotoxin; Humans; Immunoblotting; Lamins; Liver Neoplasms; Neoplasms; Nuclear Proteins; Polyenes; Polyunsaturated Alkamides; Protein Prenylation; ras Proteins; Stomach Neoplasms; Tumor Cells, Cultured