Hitachimycin

In our laboratory, we have studied the mechanism of action of tumor-inhibitory antibiotics, including bleomycin, phleomycin, adriamycin, aclarubicin, neothramycin, macromomycin, auromomycin, chartreusin, pluramycin, neopluramycin, xanthomycin A, angustmycins A and C, blasticidin S and phenomycin. The recent advances are summarized. Screening of microorganism for new antitumor antibiotics based upon our studies on mechanism of action are currently ongoing. We are interested in drug-resistance of tumor cells, and have obtained drug-resistant sublines of murine lymphoblastoma L5178Y cells. We have found that glycoprotein synthesis and alkaline phosphodiesterase (APD) activity of the plasma membrane are higher in adriamycin (ADM)-, aclarubicin (ACR)- and bleomycin (BLM)-resistant cell sublines than in the parental cells. An inhibitor of APD has been isolated from a soil Streptomyces, and identified with 2-crotonyloxymethyl-4,5,6-trihydroxycyclohex-2-enone (COTC).

Several acyl derivatives of hitachimycin have been synthesized and their activities, including antibacterial, cytocidal against HeLa cells and in vivo antitumor against sarcoma 180, evaluated. Some of these derivatives showed higher antitumor activity than hitachimycin. Among the derivatives, 11-O-propionyl-15-O-butyrylhitachimycin (12) and the 11-O-acylhitachimycins (15-17) were most effective in in vivo assay.

The taxonomic position was determined for a soil actinomycete, isolate KM-4927(T), that produced the antibiotic hitachimycin. The strain was assigned to the genus Streptomyces on the basis of 16S rDNA analysis, where it formed a separate clade. The strain is characterized by grey aerial cell mass, spiral spore chains and a rugose spore surface, menaquinones of the MK-9(H(4), H(2), H(6)) types and cell-wall chemotype I. DNA-DNA reassociation with 21 phylogenetically neighbouring Streptomyces type strains showing similar morphological characteristics to strain KM-4927(T) indicated that this isolate is only moderately related to other Streptomyces species. On the basis of genomic and physiological properties, the novel species Streptomyces scabrisporus sp. nov. is proposed; the type strain is strain KM-4927(T) (=JCM 11712(T)=NRRL B-24202(T)).