Growth and Metastases of Human Lung Cancer Are Inhibited in Mouse Xenografts by a Transition State Analogue of 5′-Methylthioadenosine Phosphorylase

Abstract

The S-adenosylmethionine (AdoMet) salvage enzyme 5 -methylthioadenosine phosphorylase (MTAP) has been implicated as both a cancer target and a tumor suppressor. We tested these hypotheses in mouse xenografts of human lung cancers. AdoMet recycling from 5 -methylthioadenosine (MTA) was blocked by inhibition of MTAP with methylthioDADMe-Immucillin-A (MTDIA), an orally available, nontoxic, picomolar transition state analogue. Blood, urine, and tumor levels of MTA increased in response to MTDIA treatment. Disruption of pathways linked to polyamine synthesis and S-adenosylmethionine (AdoMet) 2 salvage provides metabolic targets in anticancer therapy based on the essential roles of these metabolites in cell growth. AdoMet is the major methyl donor for biosynthetic methylation reactions, a precursor for polyamine synthesis, and the source of methyl groups for DNA methylation. Targeting polyamine metabolism directly at L-ornithine decarboxylase by ␣,␣-difluoromethylornithine has had limited anticancer success (1). Two AdoMet molecules are converted to 5Ј-methylthioadenosine (MTA) in spermine synthesis, and 5Ј-methylthioadenosine phosphorylase (MTAP) recycles MTA by phosphorolysis to permit subsequent resynthesis of AdoMet (Fig. 1). Our working hypothesis was that inhibition of MTAP would affect cellular MTA and AdoMet metabolism with downstream effects on protein, DNA methylation, polyamine synthesis, and polyamine-dependent enzyme reactions. We targeted MTAP by transition state analysis and developed methylthio-DADMe-Immucillin-A (MTDIA), an orally available transition state analogue inhibitor of MTAP (2). Others have proposed that MTAP is a tumor suppressor gene (3), and experiments here explore the effects of MTAP inhibition in human lung cancer xenografts.We previously demonstrated that treatment of human FaDu head and neck tumors in mouse xenografts with MT-DIA prevented tumor growth with no apparent toxicity to the mice (4). Here, we report that both MTAP-positive (H358) and MTAP-deleted (A549) human lung cancer cell lines are also sensitive to MTAP inhibition in mouse xenografts. The mechanism is probed by the metabolic and genetic consequences of MTDIA administration. In culture, MTDIA in combination with MTA slows A549 cell growth but induces apoptosis in H358 cells.Lung cancer is the leading cause of cancer-related deaths worldwide (5). Patients diagnosed at an advanced stage have a median survival of less than 12 months (6 -8). Thus, development of novel therapeutics for lung cancer is a research priority. MTDIA demonstrated significant suppression of tumor growth with human lung cancer A549 and H358 cells in mouse xenografts. Low toxicity, oral availability, and significant tumor suppression by MTDIA all support additional evaluation as an agent for the treatment of lung cancers. EXPERIMENTAL PROCEDURESCell Lines-Human non-small cell lung adenocarcinoma (NSCLC) cell line A549 and prostate carcinoma cell line PC3 were obtained from the American Type Culture Collection (Manassas, VA). Human bronchioloalveolar ...

Metabolomic Markers of Altered Nucleotide Metabolism in Early Stage Adenocarcinoma

“…MTA, through the action of 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAP), is involved in S-adenosylmethionine (AdoMet) salvage, purine salvage and spermidine synthesis (40). MTAP activity has been shown to be reduced in a wide variety of tumor types including NSCLC (41).…”

Expression of Methylthioadenosine Phosphorylase (MTAP) in Pilocytic Astrocytomas

“…It has been reported that a loss of MTAP expression sensitizes cancer cells to DNSP inhibitors, as shown in studies on leukemia and lung cell lines [30] and various malignant neoplasms [27] . This is particularly relevant for lymphomas, leukemias [27,29] and nonsmall-cell lung carcinoma [34,45] . Nevertheless, chemotherapy regimens with pemetrexed were not effective for pediatric patients with medulloblastomas, ependymomas and high-grade gliomas [49] , and the addition of methotrexate in the chemotherapeutic treatment of infratentorial ependymomas did not improve the response to these drugs [50] .…”

“…Interestingly, MTAP deletion increases the sensitivity of neoplastic cells to DNSP inhibitors such as methotrexate, L -alanosine and pemetrexed [27,30] , particularly in leukemia [29,30] and other solid tumors, e.g. in the lung, liver and breast [30,[33][34][35] . In tumors of the central nervous system, deletion and gene copy-number breakpoints of MTAP have been reported in glioblastomas [36,37] , and in pediatric high-grade gliomas [38] , respectively.…”

Tight binding enantiomers of pre-clinical drug candidates

“…In particular, where whole-body methylthioadenosine phosphorylase (MTAP) is blocked by MTDIA, 24 dramatic effects are observed in mouse xenografts of a variety of human tumours. 25,26 Also, MTDIA is a femtomolar inhibitor of the dual-substrate enzyme methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) 27 from E. coli and MTDIA and its analogues may act as antibiotics that do not induce resistance. 28,29 …”