Митрамицин A

Mithramycin is an antineoplastic antibiotic produced by Streptomyces plicatus. It is well known as the aureolic acid antitumor antibiotic that inhibits both cancer growth and bone resorption by cross-linking GC-rich DNA, thus blocking binding of Sp-family transcription factors to gene regulatory elements. Transcription of c-Src, a gene implicated in many human cancers and required for osteoclast-dependent bone resorption, is regulated by the binding of Sp factors to specific elements in its promoter. Therefore, this gene represents an important anticancer target and a potential lead target through which mithramycin displays action against osteoclastic bone resorption via an unknown mechanism. Hazards of handling this drug by the health-care personnel arise from a combination of factors: (1) its inherent toxicity and (2) the extent to which workers are exposed to the drug in the course of carrying out their duties. This exposure may be through inadvertent ingestion of the drug on foodstuffs (e.g., workers’ lunches), inhalation of drug dusts or droplets, or direct skin contact. Mithramycin has been used to decrease bone resorption in patients with humoral hypercalcemia and Paget’s disease.

yellow powder

Mithramycin was the first of the aureolic acid class of antitumour antibiotics, isolated from Streptomyces. Mithramycin inhibits transcription and protein synthesis by non-covalent binding with G-C-rich duplex DNA in the presence of magnesium and zinc ions. Mithramycin also induces differentiation of leukemic cells accompanied by an early decrease in c-myc expression, and selectively inhibits collagen-1 gene expression in human fibroblasts.

Mithramycin, recently renamed plicamycin, was found in the culture broth of Streptomyces argillaceus and S. tanashiensis by Abbott Laboratories in 1952. It is structurally related to chromomycin A3. Mithramycin shows strong inhibitory activity against malignant cells of human origin. It acts by inhibition of the DNA-directed RNA synthesis through binding with DNA. Mithramycin is used intravenously to treat cancers of the embryonal cells, seminoma, choriocarcinoma, etc.

Plicamycin (mithramycin, Mithracin) is one of the chromomycin group of antibiotics produced by Streptomyces tanashiensis. Plicamycin binds to DNA and inhibits transcription. It also inhibits resorption of bone by osteoblasts, thus lowering serum calcium levels.Very little is known about its distribution, metabolism, and excretion. Because of its severe toxicity, plicamycin has limited clinical utility.The major indication for plicamycin therapy is in the treatment of life-threatening hypercalcemia associated with malignancy. Plicamycin also can be used in the palliative therapy of metastatic testicular carcinoma when all other known active drugs have failed.

Chemical structure: aureolic acid

Anticancer antibiotic that selectively binds to G-C-rich DNA in the presence of Mg 2+ or Zn 2+ , inhibiting RNA and DNA polymerase action. Inhibits c-myc expression and induces myeloid differentiation of HL-60 promyelocytic leukemia cells.

Purify mithramycin A by crystallisation from CHCl3. It is soluble in MeOH, EtOH, Me2CO, EtOAc, Me2SO and H2O, and moderately soluble in CHCl3, but is slightly soluble in *C6H6 and Et2O. It is a fluorescent antitumour agent used in flow cytometry. [Thiem & Meyer Tetrahedron 37 551 1981, NMR: Yu et al. Nature 218 193 1968, Beilstein 17/1 V 672.]